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/-
Copyright (c) 2022 Yaël Dillies. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yaël Dillies
-/
import Mathlib.Data.Finset.Prod
import Mathlib.Data.Set.Finite
#align_import data.finset.n_ary from "leanprover-community/mathlib"@"eba7871095e834365616b5e43c8c7bb0b37058d0"
/-!
# N-ary images of finsets
This file defines `Finset.image₂`, the binary image of finsets. This is the finset version of
`Set.image2`. This is mostly useful to define pointwise operations.
## Notes
This file is very similar to `Data.Set.NAry`, `Order.Filter.NAry` and `Data.Option.NAry`. Please
keep them in sync.
We do not define `Finset.image₃` as its only purpose would be to prove properties of `Finset.image₂`
and `Set.image2` already fulfills this task.
-/
open Function Set
variable {α α' β β' γ γ' δ δ' ε ε' ζ ζ' ν : Type*}
namespace Finset
variable [DecidableEq α'] [DecidableEq β'] [DecidableEq γ] [DecidableEq γ'] [DecidableEq δ]
[DecidableEq δ'] [DecidableEq ε] [DecidableEq ε'] {f f' : α → β → γ} {g g' : α → β → γ → δ}
{s s' : Finset α} {t t' : Finset β} {u u' : Finset γ} {a a' : α} {b b' : β} {c : γ}
/-- The image of a binary function `f : α → β → γ` as a function `Finset α → Finset β → Finset γ`.
Mathematically this should be thought of as the image of the corresponding function `α × β → γ`. -/
def image₂ (f : α → β → γ) (s : Finset α) (t : Finset β) : Finset γ :=
(s ×ˢ t).image <| uncurry f
#align finset.image₂ Finset.image₂
@[simp]
theorem mem_image₂ : c ∈ image₂ f s t ↔ ∃ a ∈ s, ∃ b ∈ t, f a b = c := by
simp [image₂, and_assoc]
#align finset.mem_image₂ Finset.mem_image₂
@[simp, norm_cast]
theorem coe_image₂ (f : α → β → γ) (s : Finset α) (t : Finset β) :
(image₂ f s t : Set γ) = Set.image2 f s t :=
Set.ext fun _ => mem_image₂
#align finset.coe_image₂ Finset.coe_image₂
theorem card_image₂_le (f : α → β → γ) (s : Finset α) (t : Finset β) :
(image₂ f s t).card ≤ s.card * t.card :=
card_image_le.trans_eq <| card_product _ _
#align finset.card_image₂_le Finset.card_image₂_le
theorem card_image₂_iff :
(image₂ f s t).card = s.card * t.card ↔ (s ×ˢ t : Set (α × β)).InjOn fun x => f x.1 x.2 := by
rw [← card_product, ← coe_product]
exact card_image_iff
#align finset.card_image₂_iff Finset.card_image₂_iff
theorem card_image₂ (hf : Injective2 f) (s : Finset α) (t : Finset β) :
(image₂ f s t).card = s.card * t.card :=
(card_image_of_injective _ hf.uncurry).trans <| card_product _ _
#align finset.card_image₂ Finset.card_image₂
theorem mem_image₂_of_mem (ha : a ∈ s) (hb : b ∈ t) : f a b ∈ image₂ f s t :=
mem_image₂.2 ⟨a, ha, b, hb, rfl⟩
#align finset.mem_image₂_of_mem Finset.mem_image₂_of_mem
theorem mem_image₂_iff (hf : Injective2 f) : f a b ∈ image₂ f s t ↔ a ∈ s ∧ b ∈ t := by
rw [← mem_coe, coe_image₂, mem_image2_iff hf, mem_coe, mem_coe]
#align finset.mem_image₂_iff Finset.mem_image₂_iff
theorem image₂_subset (hs : s ⊆ s') (ht : t ⊆ t') : image₂ f s t ⊆ image₂ f s' t' := by
rw [← coe_subset, coe_image₂, coe_image₂]
exact image2_subset hs ht
#align finset.image₂_subset Finset.image₂_subset
theorem image₂_subset_left (ht : t ⊆ t') : image₂ f s t ⊆ image₂ f s t' :=
image₂_subset Subset.rfl ht
#align finset.image₂_subset_left Finset.image₂_subset_left
theorem image₂_subset_right (hs : s ⊆ s') : image₂ f s t ⊆ image₂ f s' t :=
image₂_subset hs Subset.rfl
#align finset.image₂_subset_right Finset.image₂_subset_right
theorem image_subset_image₂_left (hb : b ∈ t) : s.image (fun a => f a b) ⊆ image₂ f s t :=
image_subset_iff.2 fun _ ha => mem_image₂_of_mem ha hb
#align finset.image_subset_image₂_left Finset.image_subset_image₂_left
theorem image_subset_image₂_right (ha : a ∈ s) : t.image (fun b => f a b) ⊆ image₂ f s t :=
image_subset_iff.2 fun _ => mem_image₂_of_mem ha
#align finset.image_subset_image₂_right Finset.image_subset_image₂_right
| Mathlib/Data/Finset/NAry.lean | 98 | 100 | theorem forall_image₂_iff {p : γ → Prop} :
(∀ z ∈ image₂ f s t, p z) ↔ ∀ x ∈ s, ∀ y ∈ t, p (f x y) := by |
simp_rw [← mem_coe, coe_image₂, forall_image2_iff]
|
/-
Copyright (c) 2023 Oliver Nash. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Oliver Nash, Bhavik Mehta
-/
import Mathlib.Topology.Constructions
import Mathlib.Topology.Separation
/-!
# Discrete subsets of topological spaces
This file contains various additional properties of discrete subsets of topological spaces.
## Discreteness and compact sets
Given a topological space `X` together with a subset `s ⊆ X`, there are two distinct concepts of
"discreteness" which may hold. These are:
(i) Every point of `s` is isolated (i.e., the subset topology induced on `s` is the discrete
topology).
(ii) Every compact subset of `X` meets `s` only finitely often (i.e., the inclusion map `s → X`
tends to the cocompact filter along the cofinite filter on `s`).
When `s` is closed, the two conditions are equivalent provided `X` is locally compact and T1,
see `IsClosed.tendsto_coe_cofinite_iff`.
### Main statements
* `tendsto_cofinite_cocompact_iff`:
* `IsClosed.tendsto_coe_cofinite_iff`:
## Co-discrete open sets
In a topological space the sets which are open with discrete complement form a filter. We
formalise this as `Filter.codiscrete`.
-/
open Set Filter Function Topology
variable {X Y : Type*} [TopologicalSpace X] [TopologicalSpace Y] {f : X → Y}
section cofinite_cocompact
lemma tendsto_cofinite_cocompact_iff :
Tendsto f cofinite (cocompact _) ↔ ∀ K, IsCompact K → Set.Finite (f ⁻¹' K) := by
rw [hasBasis_cocompact.tendsto_right_iff]
refine forall₂_congr (fun K _ ↦ ?_)
simp only [mem_compl_iff, eventually_cofinite, not_not, preimage]
lemma Continuous.discrete_of_tendsto_cofinite_cocompact [T1Space X] [WeaklyLocallyCompactSpace Y]
(hf' : Continuous f) (hf : Tendsto f cofinite (cocompact _)) :
DiscreteTopology X := by
refine singletons_open_iff_discrete.mp (fun x ↦ ?_)
obtain ⟨K : Set Y, hK : IsCompact K, hK' : K ∈ 𝓝 (f x)⟩ := exists_compact_mem_nhds (f x)
obtain ⟨U : Set Y, hU₁ : U ⊆ K, hU₂ : IsOpen U, hU₃ : f x ∈ U⟩ := mem_nhds_iff.mp hK'
have hU₄ : Set.Finite (f⁻¹' U) :=
Finite.subset (tendsto_cofinite_cocompact_iff.mp hf K hK) (preimage_mono hU₁)
exact isOpen_singleton_of_finite_mem_nhds _ ((hU₂.preimage hf').mem_nhds hU₃) hU₄
lemma tendsto_cofinite_cocompact_of_discrete [DiscreteTopology X]
(hf : Tendsto f (cocompact _) (cocompact _)) :
Tendsto f cofinite (cocompact _) := by
convert hf
rw [cocompact_eq_cofinite X]
lemma IsClosed.tendsto_coe_cofinite_of_discreteTopology
{s : Set X} (hs : IsClosed s) (_hs' : DiscreteTopology s) :
Tendsto ((↑) : s → X) cofinite (cocompact _) :=
tendsto_cofinite_cocompact_of_discrete hs.closedEmbedding_subtype_val.tendsto_cocompact
lemma IsClosed.tendsto_coe_cofinite_iff [T1Space X] [WeaklyLocallyCompactSpace X]
{s : Set X} (hs : IsClosed s) :
Tendsto ((↑) : s → X) cofinite (cocompact _) ↔ DiscreteTopology s :=
⟨continuous_subtype_val.discrete_of_tendsto_cofinite_cocompact,
fun _ ↦ hs.tendsto_coe_cofinite_of_discreteTopology inferInstance⟩
end cofinite_cocompact
section codiscrete_filter
/-- Criterion for a subset `S ⊆ X` to be closed and discrete in terms of the punctured
neighbourhood filter at an arbitrary point of `X`. (Compare `discreteTopology_subtype_iff`.) -/
| Mathlib/Topology/DiscreteSubset.lean | 83 | 92 | theorem isClosed_and_discrete_iff {S : Set X} :
IsClosed S ∧ DiscreteTopology S ↔ ∀ x, Disjoint (𝓝[≠] x) (𝓟 S) := by |
rw [discreteTopology_subtype_iff, isClosed_iff_clusterPt, ← forall_and]
congrm (∀ x, ?_)
rw [← not_imp_not, clusterPt_iff_not_disjoint, not_not, ← disjoint_iff]
constructor <;> intro H
· by_cases hx : x ∈ S
exacts [H.2 hx, (H.1 hx).mono_left nhdsWithin_le_nhds]
· refine ⟨fun hx ↦ ?_, fun _ ↦ H⟩
simpa [disjoint_iff, nhdsWithin, inf_assoc, hx] using H
|
/-
Copyright (c) 2021 Sébastien Gouëzel. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Sébastien Gouëzel, Yaël Dillies
-/
import Mathlib.Analysis.Normed.Group.Pointwise
import Mathlib.Analysis.NormedSpace.Real
#align_import analysis.normed_space.pointwise from "leanprover-community/mathlib"@"bc91ed7093bf098d253401e69df601fc33dde156"
/-!
# Properties of pointwise scalar multiplication of sets in normed spaces.
We explore the relationships between scalar multiplication of sets in vector spaces, and the norm.
Notably, we express arbitrary balls as rescaling of other balls, and we show that the
multiplication of bounded sets remain bounded.
-/
open Metric Set
open Pointwise Topology
variable {𝕜 E : Type*}
section SMulZeroClass
variable [SeminormedAddCommGroup 𝕜] [SeminormedAddCommGroup E]
variable [SMulZeroClass 𝕜 E] [BoundedSMul 𝕜 E]
theorem ediam_smul_le (c : 𝕜) (s : Set E) : EMetric.diam (c • s) ≤ ‖c‖₊ • EMetric.diam s :=
(lipschitzWith_smul c).ediam_image_le s
#align ediam_smul_le ediam_smul_le
end SMulZeroClass
section DivisionRing
variable [NormedDivisionRing 𝕜] [SeminormedAddCommGroup E]
variable [Module 𝕜 E] [BoundedSMul 𝕜 E]
theorem ediam_smul₀ (c : 𝕜) (s : Set E) : EMetric.diam (c • s) = ‖c‖₊ • EMetric.diam s := by
refine le_antisymm (ediam_smul_le c s) ?_
obtain rfl | hc := eq_or_ne c 0
· obtain rfl | hs := s.eq_empty_or_nonempty
· simp
simp [zero_smul_set hs, ← Set.singleton_zero]
· have := (lipschitzWith_smul c⁻¹).ediam_image_le (c • s)
rwa [← smul_eq_mul, ← ENNReal.smul_def, Set.image_smul, inv_smul_smul₀ hc s, nnnorm_inv,
le_inv_smul_iff_of_pos (nnnorm_pos.2 hc)] at this
#align ediam_smul₀ ediam_smul₀
theorem diam_smul₀ (c : 𝕜) (x : Set E) : diam (c • x) = ‖c‖ * diam x := by
simp_rw [diam, ediam_smul₀, ENNReal.toReal_smul, NNReal.smul_def, coe_nnnorm, smul_eq_mul]
#align diam_smul₀ diam_smul₀
theorem infEdist_smul₀ {c : 𝕜} (hc : c ≠ 0) (s : Set E) (x : E) :
EMetric.infEdist (c • x) (c • s) = ‖c‖₊ • EMetric.infEdist x s := by
simp_rw [EMetric.infEdist]
have : Function.Surjective ((c • ·) : E → E) :=
Function.RightInverse.surjective (smul_inv_smul₀ hc)
trans ⨅ (y) (_ : y ∈ s), ‖c‖₊ • edist x y
· refine (this.iInf_congr _ fun y => ?_).symm
simp_rw [smul_mem_smul_set_iff₀ hc, edist_smul₀]
· have : (‖c‖₊ : ENNReal) ≠ 0 := by simp [hc]
simp_rw [ENNReal.smul_def, smul_eq_mul, ENNReal.mul_iInf_of_ne this ENNReal.coe_ne_top]
#align inf_edist_smul₀ infEdist_smul₀
theorem infDist_smul₀ {c : 𝕜} (hc : c ≠ 0) (s : Set E) (x : E) :
Metric.infDist (c • x) (c • s) = ‖c‖ * Metric.infDist x s := by
simp_rw [Metric.infDist, infEdist_smul₀ hc s, ENNReal.toReal_smul, NNReal.smul_def, coe_nnnorm,
smul_eq_mul]
#align inf_dist_smul₀ infDist_smul₀
end DivisionRing
variable [NormedField 𝕜]
section SeminormedAddCommGroup
variable [SeminormedAddCommGroup E] [NormedSpace 𝕜 E]
theorem smul_ball {c : 𝕜} (hc : c ≠ 0) (x : E) (r : ℝ) : c • ball x r = ball (c • x) (‖c‖ * r) := by
ext y
rw [mem_smul_set_iff_inv_smul_mem₀ hc]
conv_lhs => rw [← inv_smul_smul₀ hc x]
simp [← div_eq_inv_mul, div_lt_iff (norm_pos_iff.2 hc), mul_comm _ r, dist_smul₀]
#align smul_ball smul_ball
theorem smul_unitBall {c : 𝕜} (hc : c ≠ 0) : c • ball (0 : E) (1 : ℝ) = ball (0 : E) ‖c‖ := by
rw [_root_.smul_ball hc, smul_zero, mul_one]
#align smul_unit_ball smul_unitBall
theorem smul_sphere' {c : 𝕜} (hc : c ≠ 0) (x : E) (r : ℝ) :
c • sphere x r = sphere (c • x) (‖c‖ * r) := by
ext y
rw [mem_smul_set_iff_inv_smul_mem₀ hc]
conv_lhs => rw [← inv_smul_smul₀ hc x]
simp only [mem_sphere, dist_smul₀, norm_inv, ← div_eq_inv_mul, div_eq_iff (norm_pos_iff.2 hc).ne',
mul_comm r]
#align smul_sphere' smul_sphere'
theorem smul_closedBall' {c : 𝕜} (hc : c ≠ 0) (x : E) (r : ℝ) :
c • closedBall x r = closedBall (c • x) (‖c‖ * r) := by
simp only [← ball_union_sphere, Set.smul_set_union, _root_.smul_ball hc, smul_sphere' hc]
#align smul_closed_ball' smul_closedBall'
theorem set_smul_sphere_zero {s : Set 𝕜} (hs : 0 ∉ s) (r : ℝ) :
s • sphere (0 : E) r = (‖·‖) ⁻¹' ((‖·‖ * r) '' s) :=
calc
s • sphere (0 : E) r = ⋃ c ∈ s, c • sphere (0 : E) r := iUnion_smul_left_image.symm
_ = ⋃ c ∈ s, sphere (0 : E) (‖c‖ * r) := iUnion₂_congr fun c hc ↦ by
rw [smul_sphere' (ne_of_mem_of_not_mem hc hs), smul_zero]
_ = (‖·‖) ⁻¹' ((‖·‖ * r) '' s) := by ext; simp [eq_comm]
/-- Image of a bounded set in a normed space under scalar multiplication by a constant is
bounded. See also `Bornology.IsBounded.smul` for a similar lemma about an isometric action. -/
theorem Bornology.IsBounded.smul₀ {s : Set E} (hs : IsBounded s) (c : 𝕜) : IsBounded (c • s) :=
(lipschitzWith_smul c).isBounded_image hs
#align metric.bounded.smul Bornology.IsBounded.smul₀
/-- If `s` is a bounded set, then for small enough `r`, the set `{x} + r • s` is contained in any
fixed neighborhood of `x`. -/
theorem eventually_singleton_add_smul_subset {x : E} {s : Set E} (hs : Bornology.IsBounded s)
{u : Set E} (hu : u ∈ 𝓝 x) : ∀ᶠ r in 𝓝 (0 : 𝕜), {x} + r • s ⊆ u := by
obtain ⟨ε, εpos, hε⟩ : ∃ ε : ℝ, 0 < ε ∧ closedBall x ε ⊆ u := nhds_basis_closedBall.mem_iff.1 hu
obtain ⟨R, Rpos, hR⟩ : ∃ R : ℝ, 0 < R ∧ s ⊆ closedBall 0 R := hs.subset_closedBall_lt 0 0
have : Metric.closedBall (0 : 𝕜) (ε / R) ∈ 𝓝 (0 : 𝕜) := closedBall_mem_nhds _ (div_pos εpos Rpos)
filter_upwards [this] with r hr
simp only [image_add_left, singleton_add]
intro y hy
obtain ⟨z, zs, hz⟩ : ∃ z : E, z ∈ s ∧ r • z = -x + y := by simpa [mem_smul_set] using hy
have I : ‖r • z‖ ≤ ε :=
calc
‖r • z‖ = ‖r‖ * ‖z‖ := norm_smul _ _
_ ≤ ε / R * R :=
(mul_le_mul (mem_closedBall_zero_iff.1 hr) (mem_closedBall_zero_iff.1 (hR zs))
(norm_nonneg _) (div_pos εpos Rpos).le)
_ = ε := by field_simp
have : y = x + r • z := by simp only [hz, add_neg_cancel_left]
apply hε
simpa only [this, dist_eq_norm, add_sub_cancel_left, mem_closedBall] using I
#align eventually_singleton_add_smul_subset eventually_singleton_add_smul_subset
variable [NormedSpace ℝ E] {x y z : E} {δ ε : ℝ}
/-- In a real normed space, the image of the unit ball under scalar multiplication by a positive
constant `r` is the ball of radius `r`. -/
theorem smul_unitBall_of_pos {r : ℝ} (hr : 0 < r) : r • ball (0 : E) 1 = ball (0 : E) r := by
rw [smul_unitBall hr.ne', Real.norm_of_nonneg hr.le]
#align smul_unit_ball_of_pos smul_unitBall_of_pos
lemma Ioo_smul_sphere_zero {a b r : ℝ} (ha : 0 ≤ a) (hr : 0 < r) :
Ioo a b • sphere (0 : E) r = ball 0 (b * r) \ closedBall 0 (a * r) := by
have : EqOn (‖·‖) id (Ioo a b) := fun x hx ↦ abs_of_pos (ha.trans_lt hx.1)
rw [set_smul_sphere_zero (by simp [ha.not_lt]), ← image_image (· * r), this.image_eq, image_id,
image_mul_right_Ioo _ _ hr]
ext x; simp [and_comm]
-- This is also true for `ℚ`-normed spaces
theorem exists_dist_eq (x z : E) {a b : ℝ} (ha : 0 ≤ a) (hb : 0 ≤ b) (hab : a + b = 1) :
∃ y, dist x y = b * dist x z ∧ dist y z = a * dist x z := by
use a • x + b • z
nth_rw 1 [← one_smul ℝ x]
nth_rw 4 [← one_smul ℝ z]
simp [dist_eq_norm, ← hab, add_smul, ← smul_sub, norm_smul_of_nonneg, ha, hb]
#align exists_dist_eq exists_dist_eq
theorem exists_dist_le_le (hδ : 0 ≤ δ) (hε : 0 ≤ ε) (h : dist x z ≤ ε + δ) :
∃ y, dist x y ≤ δ ∧ dist y z ≤ ε := by
obtain rfl | hε' := hε.eq_or_lt
· exact ⟨z, by rwa [zero_add] at h, (dist_self _).le⟩
have hεδ := add_pos_of_pos_of_nonneg hε' hδ
refine (exists_dist_eq x z (div_nonneg hε <| add_nonneg hε hδ)
(div_nonneg hδ <| add_nonneg hε hδ) <| by
rw [← add_div, div_self hεδ.ne']).imp
fun y hy => ?_
rw [hy.1, hy.2, div_mul_comm, div_mul_comm ε]
rw [← div_le_one hεδ] at h
exact ⟨mul_le_of_le_one_left hδ h, mul_le_of_le_one_left hε h⟩
#align exists_dist_le_le exists_dist_le_le
-- This is also true for `ℚ`-normed spaces
theorem exists_dist_le_lt (hδ : 0 ≤ δ) (hε : 0 < ε) (h : dist x z < ε + δ) :
∃ y, dist x y ≤ δ ∧ dist y z < ε := by
refine (exists_dist_eq x z (div_nonneg hε.le <| add_nonneg hε.le hδ)
(div_nonneg hδ <| add_nonneg hε.le hδ) <| by
rw [← add_div, div_self (add_pos_of_pos_of_nonneg hε hδ).ne']).imp
fun y hy => ?_
rw [hy.1, hy.2, div_mul_comm, div_mul_comm ε]
rw [← div_lt_one (add_pos_of_pos_of_nonneg hε hδ)] at h
exact ⟨mul_le_of_le_one_left hδ h.le, mul_lt_of_lt_one_left hε h⟩
#align exists_dist_le_lt exists_dist_le_lt
-- This is also true for `ℚ`-normed spaces
| Mathlib/Analysis/NormedSpace/Pointwise.lean | 197 | 201 | theorem exists_dist_lt_le (hδ : 0 < δ) (hε : 0 ≤ ε) (h : dist x z < ε + δ) :
∃ y, dist x y < δ ∧ dist y z ≤ ε := by |
obtain ⟨y, yz, xy⟩ :=
exists_dist_le_lt hε hδ (show dist z x < δ + ε by simpa only [dist_comm, add_comm] using h)
exact ⟨y, by simp [dist_comm x y, dist_comm y z, *]⟩
|
/-
Copyright (c) 2018 Kenny Lau. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kenny Lau, Mario Carneiro
-/
import Mathlib.Algebra.Module.Submodule.Bilinear
import Mathlib.GroupTheory.Congruence.Basic
import Mathlib.LinearAlgebra.Basic
import Mathlib.Tactic.SuppressCompilation
#align_import linear_algebra.tensor_product from "leanprover-community/mathlib"@"88fcdc3da43943f5b01925deddaa5bf0c0e85e4e"
/-!
# Tensor product of modules over commutative semirings.
This file constructs the tensor product of modules over commutative semirings. Given a semiring
`R` and modules over it `M` and `N`, the standard construction of the tensor product is
`TensorProduct R M N`. It is also a module over `R`.
It comes with a canonical bilinear map `M → N → TensorProduct R M N`.
Given any bilinear map `M → N → P`, there is a unique linear map `TensorProduct R M N → P` whose
composition with the canonical bilinear map `M → N → TensorProduct R M N` is the given bilinear
map `M → N → P`.
We start by proving basic lemmas about bilinear maps.
## Notations
This file uses the localized notation `M ⊗ N` and `M ⊗[R] N` for `TensorProduct R M N`, as well
as `m ⊗ₜ n` and `m ⊗ₜ[R] n` for `TensorProduct.tmul R m n`.
## Tags
bilinear, tensor, tensor product
-/
suppress_compilation
section Semiring
variable {R : Type*} [CommSemiring R]
variable {R' : Type*} [Monoid R']
variable {R'' : Type*} [Semiring R'']
variable {M : Type*} {N : Type*} {P : Type*} {Q : Type*} {S : Type*} {T : Type*}
variable [AddCommMonoid M] [AddCommMonoid N] [AddCommMonoid P]
variable [AddCommMonoid Q] [AddCommMonoid S] [AddCommMonoid T]
variable [Module R M] [Module R N] [Module R P] [Module R Q] [Module R S] [Module R T]
variable [DistribMulAction R' M]
variable [Module R'' M]
variable (M N)
namespace TensorProduct
section
variable (R)
/-- The relation on `FreeAddMonoid (M × N)` that generates a congruence whose quotient is
the tensor product. -/
inductive Eqv : FreeAddMonoid (M × N) → FreeAddMonoid (M × N) → Prop
| of_zero_left : ∀ n : N, Eqv (.of (0, n)) 0
| of_zero_right : ∀ m : M, Eqv (.of (m, 0)) 0
| of_add_left : ∀ (m₁ m₂ : M) (n : N), Eqv (.of (m₁, n) + .of (m₂, n)) (.of (m₁ + m₂, n))
| of_add_right : ∀ (m : M) (n₁ n₂ : N), Eqv (.of (m, n₁) + .of (m, n₂)) (.of (m, n₁ + n₂))
| of_smul : ∀ (r : R) (m : M) (n : N), Eqv (.of (r • m, n)) (.of (m, r • n))
| add_comm : ∀ x y, Eqv (x + y) (y + x)
#align tensor_product.eqv TensorProduct.Eqv
end
end TensorProduct
variable (R)
/-- The tensor product of two modules `M` and `N` over the same commutative semiring `R`.
The localized notations are `M ⊗ N` and `M ⊗[R] N`, accessed by `open scoped TensorProduct`. -/
def TensorProduct : Type _ :=
(addConGen (TensorProduct.Eqv R M N)).Quotient
#align tensor_product TensorProduct
variable {R}
set_option quotPrecheck false in
@[inherit_doc TensorProduct] scoped[TensorProduct] infixl:100 " ⊗ " => TensorProduct _
@[inherit_doc] scoped[TensorProduct] notation:100 M " ⊗[" R "] " N:100 => TensorProduct R M N
namespace TensorProduct
section Module
protected instance add : Add (M ⊗[R] N) :=
(addConGen (TensorProduct.Eqv R M N)).hasAdd
instance addZeroClass : AddZeroClass (M ⊗[R] N) :=
{ (addConGen (TensorProduct.Eqv R M N)).addMonoid with
/- The `toAdd` field is given explicitly as `TensorProduct.add` for performance reasons.
This avoids any need to unfold `Con.addMonoid` when the type checker is checking
that instance diagrams commute -/
toAdd := TensorProduct.add _ _ }
instance addSemigroup : AddSemigroup (M ⊗[R] N) :=
{ (addConGen (TensorProduct.Eqv R M N)).addMonoid with
toAdd := TensorProduct.add _ _ }
instance addCommSemigroup : AddCommSemigroup (M ⊗[R] N) :=
{ (addConGen (TensorProduct.Eqv R M N)).addMonoid with
toAddSemigroup := TensorProduct.addSemigroup _ _
add_comm := fun x y =>
AddCon.induction_on₂ x y fun _ _ =>
Quotient.sound' <| AddConGen.Rel.of _ _ <| Eqv.add_comm _ _ }
instance : Inhabited (M ⊗[R] N) :=
⟨0⟩
variable (R) {M N}
/-- The canonical function `M → N → M ⊗ N`. The localized notations are `m ⊗ₜ n` and `m ⊗ₜ[R] n`,
accessed by `open scoped TensorProduct`. -/
def tmul (m : M) (n : N) : M ⊗[R] N :=
AddCon.mk' _ <| FreeAddMonoid.of (m, n)
#align tensor_product.tmul TensorProduct.tmul
variable {R}
/-- The canonical function `M → N → M ⊗ N`. -/
infixl:100 " ⊗ₜ " => tmul _
/-- The canonical function `M → N → M ⊗ N`. -/
notation:100 x " ⊗ₜ[" R "] " y:100 => tmul R x y
-- Porting note: make the arguments of induction_on explicit
@[elab_as_elim]
protected theorem induction_on {motive : M ⊗[R] N → Prop} (z : M ⊗[R] N)
(zero : motive 0)
(tmul : ∀ x y, motive <| x ⊗ₜ[R] y)
(add : ∀ x y, motive x → motive y → motive (x + y)) : motive z :=
AddCon.induction_on z fun x =>
FreeAddMonoid.recOn x zero fun ⟨m, n⟩ y ih => by
rw [AddCon.coe_add]
exact add _ _ (tmul ..) ih
#align tensor_product.induction_on TensorProduct.induction_on
/-- Lift an `R`-balanced map to the tensor product.
A map `f : M →+ N →+ P` additive in both components is `R`-balanced, or middle linear with respect
to `R`, if scalar multiplication in either argument is equivalent, `f (r • m) n = f m (r • n)`.
Note that strictly the first action should be a right-action by `R`, but for now `R` is commutative
so it doesn't matter. -/
-- TODO: use this to implement `lift` and `SMul.aux`. For now we do not do this as it causes
-- performance issues elsewhere.
def liftAddHom (f : M →+ N →+ P)
(hf : ∀ (r : R) (m : M) (n : N), f (r • m) n = f m (r • n)) :
M ⊗[R] N →+ P :=
(addConGen (TensorProduct.Eqv R M N)).lift (FreeAddMonoid.lift (fun mn : M × N => f mn.1 mn.2)) <|
AddCon.addConGen_le fun x y hxy =>
match x, y, hxy with
| _, _, .of_zero_left n =>
(AddCon.ker_rel _).2 <| by simp_rw [map_zero, FreeAddMonoid.lift_eval_of, map_zero,
AddMonoidHom.zero_apply]
| _, _, .of_zero_right m =>
(AddCon.ker_rel _).2 <| by simp_rw [map_zero, FreeAddMonoid.lift_eval_of, map_zero]
| _, _, .of_add_left m₁ m₂ n =>
(AddCon.ker_rel _).2 <| by simp_rw [map_add, FreeAddMonoid.lift_eval_of, map_add,
AddMonoidHom.add_apply]
| _, _, .of_add_right m n₁ n₂ =>
(AddCon.ker_rel _).2 <| by simp_rw [map_add, FreeAddMonoid.lift_eval_of, map_add]
| _, _, .of_smul s m n =>
(AddCon.ker_rel _).2 <| by rw [FreeAddMonoid.lift_eval_of, FreeAddMonoid.lift_eval_of, hf]
| _, _, .add_comm x y =>
(AddCon.ker_rel _).2 <| by simp_rw [map_add, add_comm]
@[simp]
theorem liftAddHom_tmul (f : M →+ N →+ P)
(hf : ∀ (r : R) (m : M) (n : N), f (r • m) n = f m (r • n)) (m : M) (n : N) :
liftAddHom f hf (m ⊗ₜ n) = f m n :=
rfl
variable (M)
@[simp]
theorem zero_tmul (n : N) : (0 : M) ⊗ₜ[R] n = 0 :=
Quotient.sound' <| AddConGen.Rel.of _ _ <| Eqv.of_zero_left _
#align tensor_product.zero_tmul TensorProduct.zero_tmul
variable {M}
theorem add_tmul (m₁ m₂ : M) (n : N) : (m₁ + m₂) ⊗ₜ n = m₁ ⊗ₜ n + m₂ ⊗ₜ[R] n :=
Eq.symm <| Quotient.sound' <| AddConGen.Rel.of _ _ <| Eqv.of_add_left _ _ _
#align tensor_product.add_tmul TensorProduct.add_tmul
variable (N)
@[simp]
theorem tmul_zero (m : M) : m ⊗ₜ[R] (0 : N) = 0 :=
Quotient.sound' <| AddConGen.Rel.of _ _ <| Eqv.of_zero_right _
#align tensor_product.tmul_zero TensorProduct.tmul_zero
variable {N}
theorem tmul_add (m : M) (n₁ n₂ : N) : m ⊗ₜ (n₁ + n₂) = m ⊗ₜ n₁ + m ⊗ₜ[R] n₂ :=
Eq.symm <| Quotient.sound' <| AddConGen.Rel.of _ _ <| Eqv.of_add_right _ _ _
#align tensor_product.tmul_add TensorProduct.tmul_add
instance uniqueLeft [Subsingleton M] : Unique (M ⊗[R] N) where
default := 0
uniq z := z.induction_on rfl (fun x y ↦ by rw [Subsingleton.elim x 0, zero_tmul]; rfl) <| by
rintro _ _ rfl rfl; apply add_zero
instance uniqueRight [Subsingleton N] : Unique (M ⊗[R] N) where
default := 0
uniq z := z.induction_on rfl (fun x y ↦ by rw [Subsingleton.elim y 0, tmul_zero]; rfl) <| by
rintro _ _ rfl rfl; apply add_zero
section
variable (R R' M N)
/-- A typeclass for `SMul` structures which can be moved across a tensor product.
This typeclass is generated automatically from an `IsScalarTower` instance, but exists so that
we can also add an instance for `AddCommGroup.intModule`, allowing `z •` to be moved even if
`R` does not support negation.
Note that `Module R' (M ⊗[R] N)` is available even without this typeclass on `R'`; it's only
needed if `TensorProduct.smul_tmul`, `TensorProduct.smul_tmul'`, or `TensorProduct.tmul_smul` is
used.
-/
class CompatibleSMul [DistribMulAction R' N] : Prop where
smul_tmul : ∀ (r : R') (m : M) (n : N), (r • m) ⊗ₜ n = m ⊗ₜ[R] (r • n)
#align tensor_product.compatible_smul TensorProduct.CompatibleSMul
end
/-- Note that this provides the default `compatible_smul R R M N` instance through
`IsScalarTower.left`. -/
instance (priority := 100) CompatibleSMul.isScalarTower [SMul R' R] [IsScalarTower R' R M]
[DistribMulAction R' N] [IsScalarTower R' R N] : CompatibleSMul R R' M N :=
⟨fun r m n => by
conv_lhs => rw [← one_smul R m]
conv_rhs => rw [← one_smul R n]
rw [← smul_assoc, ← smul_assoc]
exact Quotient.sound' <| AddConGen.Rel.of _ _ <| Eqv.of_smul _ _ _⟩
#align tensor_product.compatible_smul.is_scalar_tower TensorProduct.CompatibleSMul.isScalarTower
/-- `smul` can be moved from one side of the product to the other . -/
theorem smul_tmul [DistribMulAction R' N] [CompatibleSMul R R' M N] (r : R') (m : M) (n : N) :
(r • m) ⊗ₜ n = m ⊗ₜ[R] (r • n) :=
CompatibleSMul.smul_tmul _ _ _
#align tensor_product.smul_tmul TensorProduct.smul_tmul
-- Porting note: This is added as a local instance for `SMul.aux`.
-- For some reason type-class inference in Lean 3 unfolded this definition.
private def addMonoidWithWrongNSMul : AddMonoid (M ⊗[R] N) :=
{ (addConGen (TensorProduct.Eqv R M N)).addMonoid with }
attribute [local instance] addMonoidWithWrongNSMul in
/-- Auxiliary function to defining scalar multiplication on tensor product. -/
def SMul.aux {R' : Type*} [SMul R' M] (r : R') : FreeAddMonoid (M × N) →+ M ⊗[R] N :=
FreeAddMonoid.lift fun p : M × N => (r • p.1) ⊗ₜ p.2
#align tensor_product.smul.aux TensorProduct.SMul.aux
theorem SMul.aux_of {R' : Type*} [SMul R' M] (r : R') (m : M) (n : N) :
SMul.aux r (.of (m, n)) = (r • m) ⊗ₜ[R] n :=
rfl
#align tensor_product.smul.aux_of TensorProduct.SMul.aux_of
variable [SMulCommClass R R' M] [SMulCommClass R R'' M]
/-- Given two modules over a commutative semiring `R`, if one of the factors carries a
(distributive) action of a second type of scalars `R'`, which commutes with the action of `R`, then
the tensor product (over `R`) carries an action of `R'`.
This instance defines this `R'` action in the case that it is the left module which has the `R'`
action. Two natural ways in which this situation arises are:
* Extension of scalars
* A tensor product of a group representation with a module not carrying an action
Note that in the special case that `R = R'`, since `R` is commutative, we just get the usual scalar
action on a tensor product of two modules. This special case is important enough that, for
performance reasons, we define it explicitly below. -/
instance leftHasSMul : SMul R' (M ⊗[R] N) :=
⟨fun r =>
(addConGen (TensorProduct.Eqv R M N)).lift (SMul.aux r : _ →+ M ⊗[R] N) <|
AddCon.addConGen_le fun x y hxy =>
match x, y, hxy with
| _, _, .of_zero_left n =>
(AddCon.ker_rel _).2 <| by simp_rw [map_zero, SMul.aux_of, smul_zero, zero_tmul]
| _, _, .of_zero_right m =>
(AddCon.ker_rel _).2 <| by simp_rw [map_zero, SMul.aux_of, tmul_zero]
| _, _, .of_add_left m₁ m₂ n =>
(AddCon.ker_rel _).2 <| by simp_rw [map_add, SMul.aux_of, smul_add, add_tmul]
| _, _, .of_add_right m n₁ n₂ =>
(AddCon.ker_rel _).2 <| by simp_rw [map_add, SMul.aux_of, tmul_add]
| _, _, .of_smul s m n =>
(AddCon.ker_rel _).2 <| by rw [SMul.aux_of, SMul.aux_of, ← smul_comm, smul_tmul]
| _, _, .add_comm x y =>
(AddCon.ker_rel _).2 <| by simp_rw [map_add, add_comm]⟩
#align tensor_product.left_has_smul TensorProduct.leftHasSMul
instance : SMul R (M ⊗[R] N) :=
TensorProduct.leftHasSMul
protected theorem smul_zero (r : R') : r • (0 : M ⊗[R] N) = 0 :=
AddMonoidHom.map_zero _
#align tensor_product.smul_zero TensorProduct.smul_zero
protected theorem smul_add (r : R') (x y : M ⊗[R] N) : r • (x + y) = r • x + r • y :=
AddMonoidHom.map_add _ _ _
#align tensor_product.smul_add TensorProduct.smul_add
protected theorem zero_smul (x : M ⊗[R] N) : (0 : R'') • x = 0 :=
have : ∀ (r : R'') (m : M) (n : N), r • m ⊗ₜ[R] n = (r • m) ⊗ₜ n := fun _ _ _ => rfl
x.induction_on (by rw [TensorProduct.smul_zero])
(fun m n => by rw [this, zero_smul, zero_tmul]) fun x y ihx ihy => by
rw [TensorProduct.smul_add, ihx, ihy, add_zero]
#align tensor_product.zero_smul TensorProduct.zero_smul
protected theorem one_smul (x : M ⊗[R] N) : (1 : R') • x = x :=
have : ∀ (r : R') (m : M) (n : N), r • m ⊗ₜ[R] n = (r • m) ⊗ₜ n := fun _ _ _ => rfl
x.induction_on (by rw [TensorProduct.smul_zero])
(fun m n => by rw [this, one_smul])
fun x y ihx ihy => by rw [TensorProduct.smul_add, ihx, ihy]
#align tensor_product.one_smul TensorProduct.one_smul
protected theorem add_smul (r s : R'') (x : M ⊗[R] N) : (r + s) • x = r • x + s • x :=
have : ∀ (r : R'') (m : M) (n : N), r • m ⊗ₜ[R] n = (r • m) ⊗ₜ n := fun _ _ _ => rfl
x.induction_on (by simp_rw [TensorProduct.smul_zero, add_zero])
(fun m n => by simp_rw [this, add_smul, add_tmul]) fun x y ihx ihy => by
simp_rw [TensorProduct.smul_add]
rw [ihx, ihy, add_add_add_comm]
#align tensor_product.add_smul TensorProduct.add_smul
instance addMonoid : AddMonoid (M ⊗[R] N) :=
{ TensorProduct.addZeroClass _ _ with
toAddSemigroup := TensorProduct.addSemigroup _ _
toZero := (TensorProduct.addZeroClass _ _).toZero
nsmul := fun n v => n • v
nsmul_zero := by simp [TensorProduct.zero_smul]
nsmul_succ := by simp only [TensorProduct.one_smul, TensorProduct.add_smul, add_comm,
forall_const] }
instance addCommMonoid : AddCommMonoid (M ⊗[R] N) :=
{ TensorProduct.addCommSemigroup _ _ with
toAddMonoid := TensorProduct.addMonoid }
instance leftDistribMulAction : DistribMulAction R' (M ⊗[R] N) :=
have : ∀ (r : R') (m : M) (n : N), r • m ⊗ₜ[R] n = (r • m) ⊗ₜ n := fun _ _ _ => rfl
{ smul_add := fun r x y => TensorProduct.smul_add r x y
mul_smul := fun r s x =>
x.induction_on (by simp_rw [TensorProduct.smul_zero])
(fun m n => by simp_rw [this, mul_smul]) fun x y ihx ihy => by
simp_rw [TensorProduct.smul_add]
rw [ihx, ihy]
one_smul := TensorProduct.one_smul
smul_zero := TensorProduct.smul_zero }
#align tensor_product.left_distrib_mul_action TensorProduct.leftDistribMulAction
instance : DistribMulAction R (M ⊗[R] N) :=
TensorProduct.leftDistribMulAction
theorem smul_tmul' (r : R') (m : M) (n : N) : r • m ⊗ₜ[R] n = (r • m) ⊗ₜ n :=
rfl
#align tensor_product.smul_tmul' TensorProduct.smul_tmul'
@[simp]
theorem tmul_smul [DistribMulAction R' N] [CompatibleSMul R R' M N] (r : R') (x : M) (y : N) :
x ⊗ₜ (r • y) = r • x ⊗ₜ[R] y :=
(smul_tmul _ _ _).symm
#align tensor_product.tmul_smul TensorProduct.tmul_smul
theorem smul_tmul_smul (r s : R) (m : M) (n : N) : (r • m) ⊗ₜ[R] (s • n) = (r * s) • m ⊗ₜ[R] n := by
simp_rw [smul_tmul, tmul_smul, mul_smul]
#align tensor_product.smul_tmul_smul TensorProduct.smul_tmul_smul
instance leftModule : Module R'' (M ⊗[R] N) :=
{ add_smul := TensorProduct.add_smul
zero_smul := TensorProduct.zero_smul }
#align tensor_product.left_module TensorProduct.leftModule
instance : Module R (M ⊗[R] N) :=
TensorProduct.leftModule
instance [Module R''ᵐᵒᵖ M] [IsCentralScalar R'' M] : IsCentralScalar R'' (M ⊗[R] N) where
op_smul_eq_smul r x :=
x.induction_on (by rw [smul_zero, smul_zero])
(fun x y => by rw [smul_tmul', smul_tmul', op_smul_eq_smul]) fun x y hx hy => by
rw [smul_add, smul_add, hx, hy]
section
-- Like `R'`, `R'₂` provides a `DistribMulAction R'₂ (M ⊗[R] N)`
variable {R'₂ : Type*} [Monoid R'₂] [DistribMulAction R'₂ M]
variable [SMulCommClass R R'₂ M]
/-- `SMulCommClass R' R'₂ M` implies `SMulCommClass R' R'₂ (M ⊗[R] N)` -/
instance smulCommClass_left [SMulCommClass R' R'₂ M] : SMulCommClass R' R'₂ (M ⊗[R] N) where
smul_comm r' r'₂ x :=
TensorProduct.induction_on x (by simp_rw [TensorProduct.smul_zero])
(fun m n => by simp_rw [smul_tmul', smul_comm]) fun x y ihx ihy => by
simp_rw [TensorProduct.smul_add]; rw [ihx, ihy]
#align tensor_product.smul_comm_class_left TensorProduct.smulCommClass_left
variable [SMul R'₂ R']
/-- `IsScalarTower R'₂ R' M` implies `IsScalarTower R'₂ R' (M ⊗[R] N)` -/
instance isScalarTower_left [IsScalarTower R'₂ R' M] : IsScalarTower R'₂ R' (M ⊗[R] N) :=
⟨fun s r x =>
x.induction_on (by simp)
(fun m n => by rw [smul_tmul', smul_tmul', smul_tmul', smul_assoc]) fun x y ihx ihy => by
rw [smul_add, smul_add, smul_add, ihx, ihy]⟩
#align tensor_product.is_scalar_tower_left TensorProduct.isScalarTower_left
variable [DistribMulAction R'₂ N] [DistribMulAction R' N]
variable [CompatibleSMul R R'₂ M N] [CompatibleSMul R R' M N]
/-- `IsScalarTower R'₂ R' N` implies `IsScalarTower R'₂ R' (M ⊗[R] N)` -/
instance isScalarTower_right [IsScalarTower R'₂ R' N] : IsScalarTower R'₂ R' (M ⊗[R] N) :=
⟨fun s r x =>
x.induction_on (by simp)
(fun m n => by rw [← tmul_smul, ← tmul_smul, ← tmul_smul, smul_assoc]) fun x y ihx ihy => by
rw [smul_add, smul_add, smul_add, ihx, ihy]⟩
#align tensor_product.is_scalar_tower_right TensorProduct.isScalarTower_right
end
/-- A short-cut instance for the common case, where the requirements for the `compatible_smul`
instances are sufficient. -/
instance isScalarTower [SMul R' R] [IsScalarTower R' R M] : IsScalarTower R' R (M ⊗[R] N) :=
TensorProduct.isScalarTower_left
#align tensor_product.is_scalar_tower TensorProduct.isScalarTower
-- or right
variable (R M N)
/-- The canonical bilinear map `M → N → M ⊗[R] N`. -/
def mk : M →ₗ[R] N →ₗ[R] M ⊗[R] N :=
LinearMap.mk₂ R (· ⊗ₜ ·) add_tmul (fun c m n => by simp_rw [smul_tmul, tmul_smul])
tmul_add tmul_smul
#align tensor_product.mk TensorProduct.mk
variable {R M N}
@[simp]
theorem mk_apply (m : M) (n : N) : mk R M N m n = m ⊗ₜ n :=
rfl
#align tensor_product.mk_apply TensorProduct.mk_apply
theorem ite_tmul (x₁ : M) (x₂ : N) (P : Prop) [Decidable P] :
(if P then x₁ else 0) ⊗ₜ[R] x₂ = if P then x₁ ⊗ₜ x₂ else 0 := by split_ifs <;> simp
#align tensor_product.ite_tmul TensorProduct.ite_tmul
theorem tmul_ite (x₁ : M) (x₂ : N) (P : Prop) [Decidable P] :
(x₁ ⊗ₜ[R] if P then x₂ else 0) = if P then x₁ ⊗ₜ x₂ else 0 := by split_ifs <;> simp
#align tensor_product.tmul_ite TensorProduct.tmul_ite
section
theorem sum_tmul {α : Type*} (s : Finset α) (m : α → M) (n : N) :
(∑ a ∈ s, m a) ⊗ₜ[R] n = ∑ a ∈ s, m a ⊗ₜ[R] n := by
classical
induction' s using Finset.induction with a s has ih h
· simp
· simp [Finset.sum_insert has, add_tmul, ih]
#align tensor_product.sum_tmul TensorProduct.sum_tmul
theorem tmul_sum (m : M) {α : Type*} (s : Finset α) (n : α → N) :
(m ⊗ₜ[R] ∑ a ∈ s, n a) = ∑ a ∈ s, m ⊗ₜ[R] n a := by
classical
induction' s using Finset.induction with a s has ih h
· simp
· simp [Finset.sum_insert has, tmul_add, ih]
#align tensor_product.tmul_sum TensorProduct.tmul_sum
end
variable (R M N)
/-- The simple (aka pure) elements span the tensor product. -/
theorem span_tmul_eq_top : Submodule.span R { t : M ⊗[R] N | ∃ m n, m ⊗ₜ n = t } = ⊤ := by
ext t; simp only [Submodule.mem_top, iff_true_iff]
refine t.induction_on ?_ ?_ ?_
· exact Submodule.zero_mem _
· intro m n
apply Submodule.subset_span
use m, n
· intro t₁ t₂ ht₁ ht₂
exact Submodule.add_mem _ ht₁ ht₂
#align tensor_product.span_tmul_eq_top TensorProduct.span_tmul_eq_top
@[simp]
theorem map₂_mk_top_top_eq_top : Submodule.map₂ (mk R M N) ⊤ ⊤ = ⊤ := by
rw [← top_le_iff, ← span_tmul_eq_top, Submodule.map₂_eq_span_image2]
exact Submodule.span_mono fun _ ⟨m, n, h⟩ => ⟨m, trivial, n, trivial, h⟩
#align tensor_product.map₂_mk_top_top_eq_top TensorProduct.map₂_mk_top_top_eq_top
theorem exists_eq_tmul_of_forall (x : TensorProduct R M N)
(h : ∀ (m₁ m₂ : M) (n₁ n₂ : N), ∃ m n, m₁ ⊗ₜ n₁ + m₂ ⊗ₜ n₂ = m ⊗ₜ[R] n) :
∃ m n, x = m ⊗ₜ n := by
induction x using TensorProduct.induction_on with
| zero =>
use 0, 0
rw [TensorProduct.zero_tmul]
| tmul m n => use m, n
| add x y h₁ h₂ =>
obtain ⟨m₁, n₁, rfl⟩ := h₁
obtain ⟨m₂, n₂, rfl⟩ := h₂
apply h
end Module
section UMP
variable {M N}
variable (f : M →ₗ[R] N →ₗ[R] P)
/-- Auxiliary function to constructing a linear map `M ⊗ N → P` given a bilinear map `M → N → P`
with the property that its composition with the canonical bilinear map `M → N → M ⊗ N` is
the given bilinear map `M → N → P`. -/
def liftAux : M ⊗[R] N →+ P :=
liftAddHom (LinearMap.toAddMonoidHom'.comp <| f.toAddMonoidHom)
fun r m n => by dsimp; rw [LinearMap.map_smul₂, map_smul]
#align tensor_product.lift_aux TensorProduct.liftAux
theorem liftAux_tmul (m n) : liftAux f (m ⊗ₜ n) = f m n :=
rfl
#align tensor_product.lift_aux_tmul TensorProduct.liftAux_tmul
variable {f}
@[simp]
theorem liftAux.smul (r : R) (x) : liftAux f (r • x) = r • liftAux f x :=
TensorProduct.induction_on x (smul_zero _).symm
(fun p q => by simp_rw [← tmul_smul, liftAux_tmul, (f p).map_smul])
fun p q ih1 ih2 => by simp_rw [smul_add, (liftAux f).map_add, ih1, ih2, smul_add]
#align tensor_product.lift_aux.smul TensorProduct.liftAux.smul
variable (f)
/-- Constructing a linear map `M ⊗ N → P` given a bilinear map `M → N → P` with the property that
its composition with the canonical bilinear map `M → N → M ⊗ N` is
the given bilinear map `M → N → P`. -/
def lift : M ⊗[R] N →ₗ[R] P :=
{ liftAux f with map_smul' := liftAux.smul }
#align tensor_product.lift TensorProduct.lift
variable {f}
@[simp]
theorem lift.tmul (x y) : lift f (x ⊗ₜ y) = f x y :=
rfl
#align tensor_product.lift.tmul TensorProduct.lift.tmul
@[simp]
theorem lift.tmul' (x y) : (lift f).1 (x ⊗ₜ y) = f x y :=
rfl
#align tensor_product.lift.tmul' TensorProduct.lift.tmul'
theorem ext' {g h : M ⊗[R] N →ₗ[R] P} (H : ∀ x y, g (x ⊗ₜ y) = h (x ⊗ₜ y)) : g = h :=
LinearMap.ext fun z =>
TensorProduct.induction_on z (by simp_rw [LinearMap.map_zero]) H fun x y ihx ihy => by
rw [g.map_add, h.map_add, ihx, ihy]
#align tensor_product.ext' TensorProduct.ext'
theorem lift.unique {g : M ⊗[R] N →ₗ[R] P} (H : ∀ x y, g (x ⊗ₜ y) = f x y) : g = lift f :=
ext' fun m n => by rw [H, lift.tmul]
#align tensor_product.lift.unique TensorProduct.lift.unique
theorem lift_mk : lift (mk R M N) = LinearMap.id :=
Eq.symm <| lift.unique fun _ _ => rfl
#align tensor_product.lift_mk TensorProduct.lift_mk
theorem lift_compr₂ (g : P →ₗ[R] Q) : lift (f.compr₂ g) = g.comp (lift f) :=
Eq.symm <| lift.unique fun _ _ => by simp
#align tensor_product.lift_compr₂ TensorProduct.lift_compr₂
theorem lift_mk_compr₂ (f : M ⊗ N →ₗ[R] P) : lift ((mk R M N).compr₂ f) = f := by
rw [lift_compr₂ f, lift_mk, LinearMap.comp_id]
#align tensor_product.lift_mk_compr₂ TensorProduct.lift_mk_compr₂
/-- This used to be an `@[ext]` lemma, but it fails very slowly when the `ext` tactic tries to apply
it in some cases, notably when one wants to show equality of two linear maps. The `@[ext]`
attribute is now added locally where it is needed. Using this as the `@[ext]` lemma instead of
`TensorProduct.ext'` allows `ext` to apply lemmas specific to `M →ₗ _` and `N →ₗ _`.
See note [partially-applied ext lemmas]. -/
| Mathlib/LinearAlgebra/TensorProduct/Basic.lean | 589 | 590 | theorem ext {g h : M ⊗ N →ₗ[R] P} (H : (mk R M N).compr₂ g = (mk R M N).compr₂ h) : g = h := by |
rw [← lift_mk_compr₂ g, H, lift_mk_compr₂]
|
/-
Copyright (c) 2020 James Arthur. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: James Arthur, Chris Hughes, Shing Tak Lam
-/
import Mathlib.Analysis.SpecialFunctions.Trigonometric.Deriv
import Mathlib.Analysis.SpecialFunctions.Log.Basic
#align_import analysis.special_functions.arsinh from "leanprover-community/mathlib"@"f2ce6086713c78a7f880485f7917ea547a215982"
/-!
# Inverse of the sinh function
In this file we prove that sinh is bijective and hence has an
inverse, arsinh.
## Main definitions
- `Real.arsinh`: The inverse function of `Real.sinh`.
- `Real.sinhEquiv`, `Real.sinhOrderIso`, `Real.sinhHomeomorph`: `Real.sinh` as an `Equiv`,
`OrderIso`, and `Homeomorph`, respectively.
## Main Results
- `Real.sinh_surjective`, `Real.sinh_bijective`: `Real.sinh` is surjective and bijective;
- `Real.arsinh_injective`, `Real.arsinh_surjective`, `Real.arsinh_bijective`: `Real.arsinh` is
injective, surjective, and bijective;
- `Real.continuous_arsinh`, `Real.differentiable_arsinh`, `Real.contDiff_arsinh`: `Real.arsinh` is
continuous, differentiable, and continuously differentiable; we also provide dot notation
convenience lemmas like `Filter.Tendsto.arsinh` and `ContDiffAt.arsinh`.
## Tags
arsinh, arcsinh, argsinh, asinh, sinh injective, sinh bijective, sinh surjective
-/
noncomputable section
open Function Filter Set
open scoped Topology
namespace Real
variable {x y : ℝ}
/-- `arsinh` is defined using a logarithm, `arsinh x = log (x + sqrt(1 + x^2))`. -/
-- @[pp_nodot] is no longer needed
def arsinh (x : ℝ) :=
log (x + √(1 + x ^ 2))
#align real.arsinh Real.arsinh
theorem exp_arsinh (x : ℝ) : exp (arsinh x) = x + √(1 + x ^ 2) := by
apply exp_log
rw [← neg_lt_iff_pos_add']
apply lt_sqrt_of_sq_lt
simp
#align real.exp_arsinh Real.exp_arsinh
@[simp]
theorem arsinh_zero : arsinh 0 = 0 := by simp [arsinh]
#align real.arsinh_zero Real.arsinh_zero
@[simp]
theorem arsinh_neg (x : ℝ) : arsinh (-x) = -arsinh x := by
rw [← exp_eq_exp, exp_arsinh, exp_neg, exp_arsinh]
apply eq_inv_of_mul_eq_one_left
rw [neg_sq, neg_add_eq_sub, add_comm x, mul_comm, ← sq_sub_sq, sq_sqrt, add_sub_cancel_right]
exact add_nonneg zero_le_one (sq_nonneg _)
#align real.arsinh_neg Real.arsinh_neg
/-- `arsinh` is the right inverse of `sinh`. -/
@[simp]
theorem sinh_arsinh (x : ℝ) : sinh (arsinh x) = x := by
rw [sinh_eq, ← arsinh_neg, exp_arsinh, exp_arsinh, neg_sq]; field_simp
#align real.sinh_arsinh Real.sinh_arsinh
@[simp]
theorem cosh_arsinh (x : ℝ) : cosh (arsinh x) = √(1 + x ^ 2) := by
rw [← sqrt_sq (cosh_pos _).le, cosh_sq', sinh_arsinh]
#align real.cosh_arsinh Real.cosh_arsinh
/-- `sinh` is surjective, `∀ b, ∃ a, sinh a = b`. In this case, we use `a = arsinh b`. -/
theorem sinh_surjective : Surjective sinh :=
LeftInverse.surjective sinh_arsinh
#align real.sinh_surjective Real.sinh_surjective
/-- `sinh` is bijective, both injective and surjective. -/
theorem sinh_bijective : Bijective sinh :=
⟨sinh_injective, sinh_surjective⟩
#align real.sinh_bijective Real.sinh_bijective
/-- `arsinh` is the left inverse of `sinh`. -/
@[simp]
theorem arsinh_sinh (x : ℝ) : arsinh (sinh x) = x :=
rightInverse_of_injective_of_leftInverse sinh_injective sinh_arsinh x
#align real.arsinh_sinh Real.arsinh_sinh
/-- `Real.sinh` as an `Equiv`. -/
@[simps]
def sinhEquiv : ℝ ≃ ℝ where
toFun := sinh
invFun := arsinh
left_inv := arsinh_sinh
right_inv := sinh_arsinh
#align real.sinh_equiv Real.sinhEquiv
/-- `Real.sinh` as an `OrderIso`. -/
@[simps! (config := .asFn)]
def sinhOrderIso : ℝ ≃o ℝ where
toEquiv := sinhEquiv
map_rel_iff' := @sinh_le_sinh
#align real.sinh_order_iso Real.sinhOrderIso
/-- `Real.sinh` as a `Homeomorph`. -/
@[simps! (config := .asFn)]
def sinhHomeomorph : ℝ ≃ₜ ℝ :=
sinhOrderIso.toHomeomorph
#align real.sinh_homeomorph Real.sinhHomeomorph
theorem arsinh_bijective : Bijective arsinh :=
sinhEquiv.symm.bijective
#align real.arsinh_bijective Real.arsinh_bijective
theorem arsinh_injective : Injective arsinh :=
sinhEquiv.symm.injective
#align real.arsinh_injective Real.arsinh_injective
theorem arsinh_surjective : Surjective arsinh :=
sinhEquiv.symm.surjective
#align real.arsinh_surjective Real.arsinh_surjective
theorem arsinh_strictMono : StrictMono arsinh :=
sinhOrderIso.symm.strictMono
#align real.arsinh_strict_mono Real.arsinh_strictMono
@[simp]
theorem arsinh_inj : arsinh x = arsinh y ↔ x = y :=
arsinh_injective.eq_iff
#align real.arsinh_inj Real.arsinh_inj
@[simp]
theorem arsinh_le_arsinh : arsinh x ≤ arsinh y ↔ x ≤ y :=
sinhOrderIso.symm.le_iff_le
#align real.arsinh_le_arsinh Real.arsinh_le_arsinh
@[gcongr] protected alias ⟨_, GCongr.arsinh_le_arsinh⟩ := arsinh_le_arsinh
@[simp]
theorem arsinh_lt_arsinh : arsinh x < arsinh y ↔ x < y :=
sinhOrderIso.symm.lt_iff_lt
#align real.arsinh_lt_arsinh Real.arsinh_lt_arsinh
@[simp]
theorem arsinh_eq_zero_iff : arsinh x = 0 ↔ x = 0 :=
arsinh_injective.eq_iff' arsinh_zero
#align real.arsinh_eq_zero_iff Real.arsinh_eq_zero_iff
@[simp]
| Mathlib/Analysis/SpecialFunctions/Arsinh.lean | 164 | 164 | theorem arsinh_nonneg_iff : 0 ≤ arsinh x ↔ 0 ≤ x := by | rw [← sinh_le_sinh, sinh_zero, sinh_arsinh]
|
/-
Copyright (c) 2021 Joseph Myers. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Joseph Myers
-/
import Mathlib.Algebra.Group.Subgroup.Actions
import Mathlib.Algebra.Order.Module.Algebra
import Mathlib.LinearAlgebra.LinearIndependent
import Mathlib.Algebra.Ring.Subring.Units
#align_import linear_algebra.ray from "leanprover-community/mathlib"@"0f6670b8af2dff699de1c0b4b49039b31bc13c46"
/-!
# Rays in modules
This file defines rays in modules.
## Main definitions
* `SameRay`: two vectors belong to the same ray if they are proportional with a nonnegative
coefficient.
* `Module.Ray` is a type for the equivalence class of nonzero vectors in a module with some
common positive multiple.
-/
noncomputable section
section StrictOrderedCommSemiring
variable (R : Type*) [StrictOrderedCommSemiring R]
variable {M : Type*} [AddCommMonoid M] [Module R M]
variable {N : Type*} [AddCommMonoid N] [Module R N]
variable (ι : Type*) [DecidableEq ι]
/-- Two vectors are in the same ray if either one of them is zero or some positive multiples of them
are equal (in the typical case over a field, this means one of them is a nonnegative multiple of
the other). -/
def SameRay (v₁ v₂ : M) : Prop :=
v₁ = 0 ∨ v₂ = 0 ∨ ∃ r₁ r₂ : R, 0 < r₁ ∧ 0 < r₂ ∧ r₁ • v₁ = r₂ • v₂
#align same_ray SameRay
variable {R}
namespace SameRay
variable {x y z : M}
@[simp]
theorem zero_left (y : M) : SameRay R 0 y :=
Or.inl rfl
#align same_ray.zero_left SameRay.zero_left
@[simp]
theorem zero_right (x : M) : SameRay R x 0 :=
Or.inr <| Or.inl rfl
#align same_ray.zero_right SameRay.zero_right
@[nontriviality]
theorem of_subsingleton [Subsingleton M] (x y : M) : SameRay R x y := by
rw [Subsingleton.elim x 0]
exact zero_left _
#align same_ray.of_subsingleton SameRay.of_subsingleton
@[nontriviality]
theorem of_subsingleton' [Subsingleton R] (x y : M) : SameRay R x y :=
haveI := Module.subsingleton R M
of_subsingleton x y
#align same_ray.of_subsingleton' SameRay.of_subsingleton'
/-- `SameRay` is reflexive. -/
@[refl]
theorem refl (x : M) : SameRay R x x := by
nontriviality R
exact Or.inr (Or.inr <| ⟨1, 1, zero_lt_one, zero_lt_one, rfl⟩)
#align same_ray.refl SameRay.refl
protected theorem rfl : SameRay R x x :=
refl _
#align same_ray.rfl SameRay.rfl
/-- `SameRay` is symmetric. -/
@[symm]
theorem symm (h : SameRay R x y) : SameRay R y x :=
(or_left_comm.1 h).imp_right <| Or.imp_right fun ⟨r₁, r₂, h₁, h₂, h⟩ => ⟨r₂, r₁, h₂, h₁, h.symm⟩
#align same_ray.symm SameRay.symm
/-- If `x` and `y` are nonzero vectors on the same ray, then there exist positive numbers `r₁ r₂`
such that `r₁ • x = r₂ • y`. -/
theorem exists_pos (h : SameRay R x y) (hx : x ≠ 0) (hy : y ≠ 0) :
∃ r₁ r₂ : R, 0 < r₁ ∧ 0 < r₂ ∧ r₁ • x = r₂ • y :=
(h.resolve_left hx).resolve_left hy
#align same_ray.exists_pos SameRay.exists_pos
theorem sameRay_comm : SameRay R x y ↔ SameRay R y x :=
⟨SameRay.symm, SameRay.symm⟩
#align same_ray_comm SameRay.sameRay_comm
/-- `SameRay` is transitive unless the vector in the middle is zero and both other vectors are
nonzero. -/
theorem trans (hxy : SameRay R x y) (hyz : SameRay R y z) (hy : y = 0 → x = 0 ∨ z = 0) :
SameRay R x z := by
rcases eq_or_ne x 0 with (rfl | hx); · exact zero_left z
rcases eq_or_ne z 0 with (rfl | hz); · exact zero_right x
rcases eq_or_ne y 0 with (rfl | hy);
· exact (hy rfl).elim (fun h => (hx h).elim) fun h => (hz h).elim
rcases hxy.exists_pos hx hy with ⟨r₁, r₂, hr₁, hr₂, h₁⟩
rcases hyz.exists_pos hy hz with ⟨r₃, r₄, hr₃, hr₄, h₂⟩
refine Or.inr (Or.inr <| ⟨r₃ * r₁, r₂ * r₄, mul_pos hr₃ hr₁, mul_pos hr₂ hr₄, ?_⟩)
rw [mul_smul, mul_smul, h₁, ← h₂, smul_comm]
#align same_ray.trans SameRay.trans
variable {S : Type*} [OrderedCommSemiring S] [Algebra S R] [Module S M] [SMulPosMono S R]
[IsScalarTower S R M] {a : S}
/-- A vector is in the same ray as a nonnegative multiple of itself. -/
lemma sameRay_nonneg_smul_right (v : M) (h : 0 ≤ a) : SameRay R v (a • v) := by
obtain h | h := (algebraMap_nonneg R h).eq_or_gt
· rw [← algebraMap_smul R a v, h, zero_smul]
exact zero_right _
· refine Or.inr $ Or.inr ⟨algebraMap S R a, 1, h, by nontriviality R; exact zero_lt_one, ?_⟩
rw [algebraMap_smul, one_smul]
#align same_ray_nonneg_smul_right SameRay.sameRay_nonneg_smul_right
/-- A nonnegative multiple of a vector is in the same ray as that vector. -/
lemma sameRay_nonneg_smul_left (v : M) (ha : 0 ≤ a) : SameRay R (a • v) v :=
(sameRay_nonneg_smul_right v ha).symm
#align same_ray_nonneg_smul_left SameRay.sameRay_nonneg_smul_left
/-- A vector is in the same ray as a positive multiple of itself. -/
lemma sameRay_pos_smul_right (v : M) (ha : 0 < a) : SameRay R v (a • v) :=
sameRay_nonneg_smul_right v ha.le
#align same_ray_pos_smul_right SameRay.sameRay_pos_smul_right
/-- A positive multiple of a vector is in the same ray as that vector. -/
lemma sameRay_pos_smul_left (v : M) (ha : 0 < a) : SameRay R (a • v) v :=
sameRay_nonneg_smul_left v ha.le
#align same_ray_pos_smul_left SameRay.sameRay_pos_smul_left
/-- A vector is in the same ray as a nonnegative multiple of one it is in the same ray as. -/
lemma nonneg_smul_right (h : SameRay R x y) (ha : 0 ≤ a) : SameRay R x (a • y) :=
h.trans (sameRay_nonneg_smul_right y ha) fun hy => Or.inr <| by rw [hy, smul_zero]
#align same_ray.nonneg_smul_right SameRay.nonneg_smul_right
/-- A nonnegative multiple of a vector is in the same ray as one it is in the same ray as. -/
lemma nonneg_smul_left (h : SameRay R x y) (ha : 0 ≤ a) : SameRay R (a • x) y :=
(h.symm.nonneg_smul_right ha).symm
#align same_ray.nonneg_smul_left SameRay.nonneg_smul_left
/-- A vector is in the same ray as a positive multiple of one it is in the same ray as. -/
theorem pos_smul_right (h : SameRay R x y) (ha : 0 < a) : SameRay R x (a • y) :=
h.nonneg_smul_right ha.le
#align same_ray.pos_smul_right SameRay.pos_smul_right
/-- A positive multiple of a vector is in the same ray as one it is in the same ray as. -/
theorem pos_smul_left (h : SameRay R x y) (hr : 0 < a) : SameRay R (a • x) y :=
h.nonneg_smul_left hr.le
#align same_ray.pos_smul_left SameRay.pos_smul_left
/-- If two vectors are on the same ray then they remain so after applying a linear map. -/
theorem map (f : M →ₗ[R] N) (h : SameRay R x y) : SameRay R (f x) (f y) :=
(h.imp fun hx => by rw [hx, map_zero]) <|
Or.imp (fun hy => by rw [hy, map_zero]) fun ⟨r₁, r₂, hr₁, hr₂, h⟩ =>
⟨r₁, r₂, hr₁, hr₂, by rw [← f.map_smul, ← f.map_smul, h]⟩
#align same_ray.map SameRay.map
/-- The images of two vectors under an injective linear map are on the same ray if and only if the
original vectors are on the same ray. -/
theorem _root_.Function.Injective.sameRay_map_iff
{F : Type*} [FunLike F M N] [LinearMapClass F R M N]
{f : F} (hf : Function.Injective f) :
SameRay R (f x) (f y) ↔ SameRay R x y := by
simp only [SameRay, map_zero, ← hf.eq_iff, map_smul]
#align function.injective.same_ray_map_iff Function.Injective.sameRay_map_iff
/-- The images of two vectors under a linear equivalence are on the same ray if and only if the
original vectors are on the same ray. -/
@[simp]
theorem sameRay_map_iff (e : M ≃ₗ[R] N) : SameRay R (e x) (e y) ↔ SameRay R x y :=
Function.Injective.sameRay_map_iff (EquivLike.injective e)
#align same_ray_map_iff SameRay.sameRay_map_iff
/-- If two vectors are on the same ray then both scaled by the same action are also on the same
ray. -/
theorem smul {S : Type*} [Monoid S] [DistribMulAction S M] [SMulCommClass R S M]
(h : SameRay R x y) (s : S) : SameRay R (s • x) (s • y) :=
h.map (s • (LinearMap.id : M →ₗ[R] M))
#align same_ray.smul SameRay.smul
/-- If `x` and `y` are on the same ray as `z`, then so is `x + y`. -/
theorem add_left (hx : SameRay R x z) (hy : SameRay R y z) : SameRay R (x + y) z := by
rcases eq_or_ne x 0 with (rfl | hx₀); · rwa [zero_add]
rcases eq_or_ne y 0 with (rfl | hy₀); · rwa [add_zero]
rcases eq_or_ne z 0 with (rfl | hz₀); · apply zero_right
rcases hx.exists_pos hx₀ hz₀ with ⟨rx, rz₁, hrx, hrz₁, Hx⟩
rcases hy.exists_pos hy₀ hz₀ with ⟨ry, rz₂, hry, hrz₂, Hy⟩
refine Or.inr (Or.inr ⟨rx * ry, ry * rz₁ + rx * rz₂, mul_pos hrx hry, ?_, ?_⟩)
· apply_rules [add_pos, mul_pos]
· simp only [mul_smul, smul_add, add_smul, ← Hx, ← Hy]
rw [smul_comm]
#align same_ray.add_left SameRay.add_left
/-- If `y` and `z` are on the same ray as `x`, then so is `y + z`. -/
theorem add_right (hy : SameRay R x y) (hz : SameRay R x z) : SameRay R x (y + z) :=
(hy.symm.add_left hz.symm).symm
#align same_ray.add_right SameRay.add_right
end SameRay
-- Porting note(#5171): removed has_nonempty_instance nolint, no such linter
set_option linter.unusedVariables false in
/-- Nonzero vectors, as used to define rays. This type depends on an unused argument `R` so that
`RayVector.Setoid` can be an instance. -/
@[nolint unusedArguments]
def RayVector (R M : Type*) [Zero M] :=
{ v : M // v ≠ 0 }
#align ray_vector RayVector
-- Porting note: Made Coe into CoeOut so it's not dangerous anymore
instance RayVector.coe [Zero M] : CoeOut (RayVector R M) M where
coe := Subtype.val
#align ray_vector.has_coe RayVector.coe
instance {R M : Type*} [Zero M] [Nontrivial M] : Nonempty (RayVector R M) :=
let ⟨x, hx⟩ := exists_ne (0 : M)
⟨⟨x, hx⟩⟩
variable (R M)
/-- The setoid of the `SameRay` relation for the subtype of nonzero vectors. -/
instance RayVector.Setoid : Setoid (RayVector R M) where
r x y := SameRay R (x : M) y
iseqv :=
⟨fun x => SameRay.refl _, fun h => h.symm, by
intros x y z hxy hyz
exact hxy.trans hyz fun hy => (y.2 hy).elim⟩
/-- A ray (equivalence class of nonzero vectors with common positive multiples) in a module. -/
-- Porting note(#5171): removed has_nonempty_instance nolint, no such linter
def Module.Ray :=
Quotient (RayVector.Setoid R M)
#align module.ray Module.Ray
variable {R M}
/-- Equivalence of nonzero vectors, in terms of `SameRay`. -/
theorem equiv_iff_sameRay {v₁ v₂ : RayVector R M} : v₁ ≈ v₂ ↔ SameRay R (v₁ : M) v₂ :=
Iff.rfl
#align equiv_iff_same_ray equiv_iff_sameRay
variable (R)
-- Porting note: Removed `protected` here, not in namespace
/-- The ray given by a nonzero vector. -/
def rayOfNeZero (v : M) (h : v ≠ 0) : Module.Ray R M :=
⟦⟨v, h⟩⟧
#align ray_of_ne_zero rayOfNeZero
/-- An induction principle for `Module.Ray`, used as `induction x using Module.Ray.ind`. -/
theorem Module.Ray.ind {C : Module.Ray R M → Prop} (h : ∀ (v) (hv : v ≠ 0), C (rayOfNeZero R v hv))
(x : Module.Ray R M) : C x :=
Quotient.ind (Subtype.rec <| h) x
#align module.ray.ind Module.Ray.ind
variable {R}
instance [Nontrivial M] : Nonempty (Module.Ray R M) :=
Nonempty.map Quotient.mk' inferInstance
/-- The rays given by two nonzero vectors are equal if and only if those vectors
satisfy `SameRay`. -/
theorem ray_eq_iff {v₁ v₂ : M} (hv₁ : v₁ ≠ 0) (hv₂ : v₂ ≠ 0) :
rayOfNeZero R _ hv₁ = rayOfNeZero R _ hv₂ ↔ SameRay R v₁ v₂ :=
Quotient.eq'
#align ray_eq_iff ray_eq_iff
/-- The ray given by a positive multiple of a nonzero vector. -/
@[simp]
theorem ray_pos_smul {v : M} (h : v ≠ 0) {r : R} (hr : 0 < r) (hrv : r • v ≠ 0) :
rayOfNeZero R (r • v) hrv = rayOfNeZero R v h :=
(ray_eq_iff _ _).2 <| SameRay.sameRay_pos_smul_left v hr
#align ray_pos_smul ray_pos_smul
/-- An equivalence between modules implies an equivalence between ray vectors. -/
def RayVector.mapLinearEquiv (e : M ≃ₗ[R] N) : RayVector R M ≃ RayVector R N :=
Equiv.subtypeEquiv e.toEquiv fun _ => e.map_ne_zero_iff.symm
#align ray_vector.map_linear_equiv RayVector.mapLinearEquiv
/-- An equivalence between modules implies an equivalence between rays. -/
def Module.Ray.map (e : M ≃ₗ[R] N) : Module.Ray R M ≃ Module.Ray R N :=
Quotient.congr (RayVector.mapLinearEquiv e) fun _ _=> (SameRay.sameRay_map_iff _).symm
#align module.ray.map Module.Ray.map
@[simp]
theorem Module.Ray.map_apply (e : M ≃ₗ[R] N) (v : M) (hv : v ≠ 0) :
Module.Ray.map e (rayOfNeZero _ v hv) = rayOfNeZero _ (e v) (e.map_ne_zero_iff.2 hv) :=
rfl
#align module.ray.map_apply Module.Ray.map_apply
@[simp]
theorem Module.Ray.map_refl : (Module.Ray.map <| LinearEquiv.refl R M) = Equiv.refl _ :=
Equiv.ext <| Module.Ray.ind R fun _ _ => rfl
#align module.ray.map_refl Module.Ray.map_refl
@[simp]
theorem Module.Ray.map_symm (e : M ≃ₗ[R] N) : (Module.Ray.map e).symm = Module.Ray.map e.symm :=
rfl
#align module.ray.map_symm Module.Ray.map_symm
section Action
variable {G : Type*} [Group G] [DistribMulAction G M]
/-- Any invertible action preserves the non-zeroness of ray vectors. This is primarily of interest
when `G = Rˣ` -/
instance {R : Type*} : MulAction G (RayVector R M) where
smul r := Subtype.map (r • ·) fun _ => (smul_ne_zero_iff_ne _).2
mul_smul a b _ := Subtype.ext <| mul_smul a b _
one_smul _ := Subtype.ext <| one_smul _ _
variable [SMulCommClass R G M]
/-- Any invertible action preserves the non-zeroness of rays. This is primarily of interest when
`G = Rˣ` -/
instance : MulAction G (Module.Ray R M) where
smul r := Quotient.map (r • ·) fun _ _ h => h.smul _
mul_smul a b := Quotient.ind fun _ => congr_arg Quotient.mk' <| mul_smul a b _
one_smul := Quotient.ind fun _ => congr_arg Quotient.mk' <| one_smul _ _
/-- The action via `LinearEquiv.apply_distribMulAction` corresponds to `Module.Ray.map`. -/
@[simp]
theorem Module.Ray.linearEquiv_smul_eq_map (e : M ≃ₗ[R] M) (v : Module.Ray R M) :
e • v = Module.Ray.map e v :=
rfl
#align module.ray.linear_equiv_smul_eq_map Module.Ray.linearEquiv_smul_eq_map
@[simp]
theorem smul_rayOfNeZero (g : G) (v : M) (hv) :
g • rayOfNeZero R v hv = rayOfNeZero R (g • v) ((smul_ne_zero_iff_ne _).2 hv) :=
rfl
#align smul_ray_of_ne_zero smul_rayOfNeZero
end Action
namespace Module.Ray
-- Porting note: `(u.1 : R)` was `(u : R)`, CoeHead from R to Rˣ does not seem to work.
/-- Scaling by a positive unit is a no-op. -/
theorem units_smul_of_pos (u : Rˣ) (hu : 0 < (u.1 : R)) (v : Module.Ray R M) : u • v = v := by
induction v using Module.Ray.ind
rw [smul_rayOfNeZero, ray_eq_iff]
exact SameRay.sameRay_pos_smul_left _ hu
#align module.ray.units_smul_of_pos Module.Ray.units_smul_of_pos
/-- An arbitrary `RayVector` giving a ray. -/
def someRayVector (x : Module.Ray R M) : RayVector R M :=
Quotient.out x
#align module.ray.some_ray_vector Module.Ray.someRayVector
/-- The ray of `someRayVector`. -/
@[simp]
theorem someRayVector_ray (x : Module.Ray R M) : (⟦x.someRayVector⟧ : Module.Ray R M) = x :=
Quotient.out_eq _
#align module.ray.some_ray_vector_ray Module.Ray.someRayVector_ray
/-- An arbitrary nonzero vector giving a ray. -/
def someVector (x : Module.Ray R M) : M :=
x.someRayVector
#align module.ray.some_vector Module.Ray.someVector
/-- `someVector` is nonzero. -/
@[simp]
theorem someVector_ne_zero (x : Module.Ray R M) : x.someVector ≠ 0 :=
x.someRayVector.property
#align module.ray.some_vector_ne_zero Module.Ray.someVector_ne_zero
/-- The ray of `someVector`. -/
@[simp]
theorem someVector_ray (x : Module.Ray R M) : rayOfNeZero R _ x.someVector_ne_zero = x :=
(congr_arg _ (Subtype.coe_eta _ _) : _).trans x.out_eq
#align module.ray.some_vector_ray Module.Ray.someVector_ray
end Module.Ray
end StrictOrderedCommSemiring
section StrictOrderedCommRing
variable {R : Type*} [StrictOrderedCommRing R]
variable {M N : Type*} [AddCommGroup M] [AddCommGroup N] [Module R M] [Module R N] {x y : M}
/-- `SameRay.neg` as an `iff`. -/
@[simp]
theorem sameRay_neg_iff : SameRay R (-x) (-y) ↔ SameRay R x y := by
simp only [SameRay, neg_eq_zero, smul_neg, neg_inj]
#align same_ray_neg_iff sameRay_neg_iff
alias ⟨SameRay.of_neg, SameRay.neg⟩ := sameRay_neg_iff
#align same_ray.of_neg SameRay.of_neg
#align same_ray.neg SameRay.neg
theorem sameRay_neg_swap : SameRay R (-x) y ↔ SameRay R x (-y) := by rw [← sameRay_neg_iff, neg_neg]
#align same_ray_neg_swap sameRay_neg_swap
theorem eq_zero_of_sameRay_neg_smul_right [NoZeroSMulDivisors R M] {r : R} (hr : r < 0)
(h : SameRay R x (r • x)) : x = 0 := by
rcases h with (rfl | h₀ | ⟨r₁, r₂, hr₁, hr₂, h⟩)
· rfl
· simpa [hr.ne] using h₀
· rw [← sub_eq_zero, smul_smul, ← sub_smul, smul_eq_zero] at h
refine h.resolve_left (ne_of_gt <| sub_pos.2 ?_)
exact (mul_neg_of_pos_of_neg hr₂ hr).trans hr₁
#align eq_zero_of_same_ray_neg_smul_right eq_zero_of_sameRay_neg_smul_right
/-- If a vector is in the same ray as its negation, that vector is zero. -/
theorem eq_zero_of_sameRay_self_neg [NoZeroSMulDivisors R M] (h : SameRay R x (-x)) : x = 0 := by
nontriviality M; haveI : Nontrivial R := Module.nontrivial R M
refine eq_zero_of_sameRay_neg_smul_right (neg_lt_zero.2 (zero_lt_one' R)) ?_
rwa [neg_one_smul]
#align eq_zero_of_same_ray_self_neg eq_zero_of_sameRay_self_neg
namespace RayVector
/-- Negating a nonzero vector. -/
instance {R : Type*} : Neg (RayVector R M) :=
⟨fun v => ⟨-v, neg_ne_zero.2 v.prop⟩⟩
/-- Negating a nonzero vector commutes with coercion to the underlying module. -/
@[simp, norm_cast]
theorem coe_neg {R : Type*} (v : RayVector R M) : ↑(-v) = -(v : M) :=
rfl
#align ray_vector.coe_neg RayVector.coe_neg
/-- Negating a nonzero vector twice produces the original vector. -/
instance {R : Type*} : InvolutiveNeg (RayVector R M) where
neg := Neg.neg
neg_neg v := by rw [Subtype.ext_iff, coe_neg, coe_neg, neg_neg]
/-- If two nonzero vectors are equivalent, so are their negations. -/
@[simp]
theorem equiv_neg_iff {v₁ v₂ : RayVector R M} : -v₁ ≈ -v₂ ↔ v₁ ≈ v₂ :=
sameRay_neg_iff
#align ray_vector.equiv_neg_iff RayVector.equiv_neg_iff
end RayVector
variable (R)
/-- Negating a ray. -/
instance : Neg (Module.Ray R M) :=
⟨Quotient.map (fun v => -v) fun _ _ => RayVector.equiv_neg_iff.2⟩
/-- The ray given by the negation of a nonzero vector. -/
@[simp]
theorem neg_rayOfNeZero (v : M) (h : v ≠ 0) :
-rayOfNeZero R _ h = rayOfNeZero R (-v) (neg_ne_zero.2 h) :=
rfl
#align neg_ray_of_ne_zero neg_rayOfNeZero
namespace Module.Ray
variable {R}
/-- Negating a ray twice produces the original ray. -/
instance : InvolutiveNeg (Module.Ray R M) where
neg := Neg.neg
neg_neg x := by apply ind R (by simp) x
-- Quotient.ind (fun a => congr_arg Quotient.mk' <| neg_neg _) x
/-- A ray does not equal its own negation. -/
theorem ne_neg_self [NoZeroSMulDivisors R M] (x : Module.Ray R M) : x ≠ -x := by
induction' x using Module.Ray.ind with x hx
rw [neg_rayOfNeZero, Ne, ray_eq_iff]
exact mt eq_zero_of_sameRay_self_neg hx
#align module.ray.ne_neg_self Module.Ray.ne_neg_self
theorem neg_units_smul (u : Rˣ) (v : Module.Ray R M) : -u • v = -(u • v) := by
induction v using Module.Ray.ind
simp only [smul_rayOfNeZero, Units.smul_def, Units.val_neg, neg_smul, neg_rayOfNeZero]
#align module.ray.neg_units_smul Module.Ray.neg_units_smul
-- Porting note: `(u.1 : R)` was `(u : R)`, CoeHead from R to Rˣ does not seem to work.
/-- Scaling by a negative unit is negation. -/
theorem units_smul_of_neg (u : Rˣ) (hu : u.1 < 0) (v : Module.Ray R M) : u • v = -v := by
rw [← neg_inj, neg_neg, ← neg_units_smul, units_smul_of_pos]
rwa [Units.val_neg, Right.neg_pos_iff]
#align module.ray.units_smul_of_neg Module.Ray.units_smul_of_neg
@[simp]
protected theorem map_neg (f : M ≃ₗ[R] N) (v : Module.Ray R M) : map f (-v) = -map f v := by
induction' v using Module.Ray.ind with g hg
simp
#align module.ray.map_neg Module.Ray.map_neg
end Module.Ray
end StrictOrderedCommRing
section LinearOrderedCommRing
variable {R : Type*} [LinearOrderedCommRing R]
variable {M : Type*} [AddCommGroup M] [Module R M]
-- Porting note: Needed to add coercion ↥ below
/-- `SameRay` follows from membership of `MulAction.orbit` for the `Units.posSubgroup`. -/
theorem sameRay_of_mem_orbit {v₁ v₂ : M} (h : v₁ ∈ MulAction.orbit ↥(Units.posSubgroup R) v₂) :
SameRay R v₁ v₂ := by
rcases h with ⟨⟨r, hr : 0 < r.1⟩, rfl : r • v₂ = v₁⟩
exact SameRay.sameRay_pos_smul_left _ hr
#align same_ray_of_mem_orbit sameRay_of_mem_orbit
/-- Scaling by an inverse unit is the same as scaling by itself. -/
@[simp]
theorem units_inv_smul (u : Rˣ) (v : Module.Ray R M) : u⁻¹ • v = u • v :=
have := mul_self_pos.2 u.ne_zero
calc
u⁻¹ • v = (u * u) • u⁻¹ • v := Eq.symm <| (u⁻¹ • v).units_smul_of_pos _ (by exact this)
_ = u • v := by rw [mul_smul, smul_inv_smul]
#align units_inv_smul units_inv_smul
section
variable [NoZeroSMulDivisors R M]
@[simp]
theorem sameRay_smul_right_iff {v : M} {r : R} : SameRay R v (r • v) ↔ 0 ≤ r ∨ v = 0 :=
⟨fun hrv => or_iff_not_imp_left.2 fun hr => eq_zero_of_sameRay_neg_smul_right (not_le.1 hr) hrv,
or_imp.2 ⟨SameRay.sameRay_nonneg_smul_right v, fun h => h.symm ▸ SameRay.zero_left _⟩⟩
#align same_ray_smul_right_iff sameRay_smul_right_iff
/-- A nonzero vector is in the same ray as a multiple of itself if and only if that multiple
is positive. -/
| Mathlib/LinearAlgebra/Ray.lean | 532 | 534 | theorem sameRay_smul_right_iff_of_ne {v : M} (hv : v ≠ 0) {r : R} (hr : r ≠ 0) :
SameRay R v (r • v) ↔ 0 < r := by |
simp only [sameRay_smul_right_iff, hv, or_false_iff, hr.symm.le_iff_lt]
|
/-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Johannes Hölzl, Scott Morrison, Jens Wagemaker
-/
import Mathlib.Algebra.MonoidAlgebra.Degree
import Mathlib.Algebra.Polynomial.Coeff
import Mathlib.Algebra.Polynomial.Monomial
import Mathlib.Data.Fintype.BigOperators
import Mathlib.Data.Nat.WithBot
import Mathlib.Data.Nat.Cast.WithTop
import Mathlib.Data.Nat.SuccPred
#align_import data.polynomial.degree.definitions from "leanprover-community/mathlib"@"808ea4ebfabeb599f21ec4ae87d6dc969597887f"
/-!
# Theory of univariate polynomials
The definitions include
`degree`, `Monic`, `leadingCoeff`
Results include
- `degree_mul` : The degree of the product is the sum of degrees
- `leadingCoeff_add_of_degree_eq` and `leadingCoeff_add_of_degree_lt` :
The leading_coefficient of a sum is determined by the leading coefficients and degrees
-/
-- Porting note: `Mathlib.Data.Nat.Cast.WithTop` should be imported for `Nat.cast_withBot`.
set_option linter.uppercaseLean3 false
noncomputable section
open Finsupp Finset
open Polynomial
namespace Polynomial
universe u v
variable {R : Type u} {S : Type v} {a b c d : R} {n m : ℕ}
section Semiring
variable [Semiring R] {p q r : R[X]}
/-- `degree p` is the degree of the polynomial `p`, i.e. the largest `X`-exponent in `p`.
`degree p = some n` when `p ≠ 0` and `n` is the highest power of `X` that appears in `p`, otherwise
`degree 0 = ⊥`. -/
def degree (p : R[X]) : WithBot ℕ :=
p.support.max
#align polynomial.degree Polynomial.degree
theorem supDegree_eq_degree (p : R[X]) : p.toFinsupp.supDegree WithBot.some = p.degree :=
max_eq_sup_coe
theorem degree_lt_wf : WellFounded fun p q : R[X] => degree p < degree q :=
InvImage.wf degree wellFounded_lt
#align polynomial.degree_lt_wf Polynomial.degree_lt_wf
instance : WellFoundedRelation R[X] :=
⟨_, degree_lt_wf⟩
/-- `natDegree p` forces `degree p` to ℕ, by defining `natDegree 0 = 0`. -/
def natDegree (p : R[X]) : ℕ :=
(degree p).unbot' 0
#align polynomial.nat_degree Polynomial.natDegree
/-- `leadingCoeff p` gives the coefficient of the highest power of `X` in `p`-/
def leadingCoeff (p : R[X]) : R :=
coeff p (natDegree p)
#align polynomial.leading_coeff Polynomial.leadingCoeff
/-- a polynomial is `Monic` if its leading coefficient is 1 -/
def Monic (p : R[X]) :=
leadingCoeff p = (1 : R)
#align polynomial.monic Polynomial.Monic
@[nontriviality]
theorem monic_of_subsingleton [Subsingleton R] (p : R[X]) : Monic p :=
Subsingleton.elim _ _
#align polynomial.monic_of_subsingleton Polynomial.monic_of_subsingleton
theorem Monic.def : Monic p ↔ leadingCoeff p = 1 :=
Iff.rfl
#align polynomial.monic.def Polynomial.Monic.def
instance Monic.decidable [DecidableEq R] : Decidable (Monic p) := by unfold Monic; infer_instance
#align polynomial.monic.decidable Polynomial.Monic.decidable
@[simp]
theorem Monic.leadingCoeff {p : R[X]} (hp : p.Monic) : leadingCoeff p = 1 :=
hp
#align polynomial.monic.leading_coeff Polynomial.Monic.leadingCoeff
theorem Monic.coeff_natDegree {p : R[X]} (hp : p.Monic) : p.coeff p.natDegree = 1 :=
hp
#align polynomial.monic.coeff_nat_degree Polynomial.Monic.coeff_natDegree
@[simp]
theorem degree_zero : degree (0 : R[X]) = ⊥ :=
rfl
#align polynomial.degree_zero Polynomial.degree_zero
@[simp]
theorem natDegree_zero : natDegree (0 : R[X]) = 0 :=
rfl
#align polynomial.nat_degree_zero Polynomial.natDegree_zero
@[simp]
theorem coeff_natDegree : coeff p (natDegree p) = leadingCoeff p :=
rfl
#align polynomial.coeff_nat_degree Polynomial.coeff_natDegree
@[simp]
theorem degree_eq_bot : degree p = ⊥ ↔ p = 0 :=
⟨fun h => support_eq_empty.1 (Finset.max_eq_bot.1 h), fun h => h.symm ▸ rfl⟩
#align polynomial.degree_eq_bot Polynomial.degree_eq_bot
@[nontriviality]
theorem degree_of_subsingleton [Subsingleton R] : degree p = ⊥ := by
rw [Subsingleton.elim p 0, degree_zero]
#align polynomial.degree_of_subsingleton Polynomial.degree_of_subsingleton
@[nontriviality]
theorem natDegree_of_subsingleton [Subsingleton R] : natDegree p = 0 := by
rw [Subsingleton.elim p 0, natDegree_zero]
#align polynomial.nat_degree_of_subsingleton Polynomial.natDegree_of_subsingleton
theorem degree_eq_natDegree (hp : p ≠ 0) : degree p = (natDegree p : WithBot ℕ) := by
let ⟨n, hn⟩ := not_forall.1 (mt Option.eq_none_iff_forall_not_mem.2 (mt degree_eq_bot.1 hp))
have hn : degree p = some n := Classical.not_not.1 hn
rw [natDegree, hn]; rfl
#align polynomial.degree_eq_nat_degree Polynomial.degree_eq_natDegree
theorem supDegree_eq_natDegree (p : R[X]) : p.toFinsupp.supDegree id = p.natDegree := by
obtain rfl|h := eq_or_ne p 0
· simp
apply WithBot.coe_injective
rw [← AddMonoidAlgebra.supDegree_withBot_some_comp, Function.comp_id, supDegree_eq_degree,
degree_eq_natDegree h, Nat.cast_withBot]
rwa [support_toFinsupp, nonempty_iff_ne_empty, Ne, support_eq_empty]
theorem degree_eq_iff_natDegree_eq {p : R[X]} {n : ℕ} (hp : p ≠ 0) :
p.degree = n ↔ p.natDegree = n := by rw [degree_eq_natDegree hp]; exact WithBot.coe_eq_coe
#align polynomial.degree_eq_iff_nat_degree_eq Polynomial.degree_eq_iff_natDegree_eq
theorem degree_eq_iff_natDegree_eq_of_pos {p : R[X]} {n : ℕ} (hn : 0 < n) :
p.degree = n ↔ p.natDegree = n := by
obtain rfl|h := eq_or_ne p 0
· simp [hn.ne]
· exact degree_eq_iff_natDegree_eq h
#align polynomial.degree_eq_iff_nat_degree_eq_of_pos Polynomial.degree_eq_iff_natDegree_eq_of_pos
theorem natDegree_eq_of_degree_eq_some {p : R[X]} {n : ℕ} (h : degree p = n) : natDegree p = n := by
-- Porting note: `Nat.cast_withBot` is required.
rw [natDegree, h, Nat.cast_withBot, WithBot.unbot'_coe]
#align polynomial.nat_degree_eq_of_degree_eq_some Polynomial.natDegree_eq_of_degree_eq_some
theorem degree_ne_of_natDegree_ne {n : ℕ} : p.natDegree ≠ n → degree p ≠ n :=
mt natDegree_eq_of_degree_eq_some
#align polynomial.degree_ne_of_nat_degree_ne Polynomial.degree_ne_of_natDegree_ne
@[simp]
theorem degree_le_natDegree : degree p ≤ natDegree p :=
WithBot.giUnbot'Bot.gc.le_u_l _
#align polynomial.degree_le_nat_degree Polynomial.degree_le_natDegree
theorem natDegree_eq_of_degree_eq [Semiring S] {q : S[X]} (h : degree p = degree q) :
natDegree p = natDegree q := by unfold natDegree; rw [h]
#align polynomial.nat_degree_eq_of_degree_eq Polynomial.natDegree_eq_of_degree_eq
theorem le_degree_of_ne_zero (h : coeff p n ≠ 0) : (n : WithBot ℕ) ≤ degree p := by
rw [Nat.cast_withBot]
exact Finset.le_sup (mem_support_iff.2 h)
#align polynomial.le_degree_of_ne_zero Polynomial.le_degree_of_ne_zero
theorem le_natDegree_of_ne_zero (h : coeff p n ≠ 0) : n ≤ natDegree p := by
rw [← Nat.cast_le (α := WithBot ℕ), ← degree_eq_natDegree]
· exact le_degree_of_ne_zero h
· rintro rfl
exact h rfl
#align polynomial.le_nat_degree_of_ne_zero Polynomial.le_natDegree_of_ne_zero
theorem le_natDegree_of_mem_supp (a : ℕ) : a ∈ p.support → a ≤ natDegree p :=
le_natDegree_of_ne_zero ∘ mem_support_iff.mp
#align polynomial.le_nat_degree_of_mem_supp Polynomial.le_natDegree_of_mem_supp
theorem degree_eq_of_le_of_coeff_ne_zero (pn : p.degree ≤ n) (p1 : p.coeff n ≠ 0) : p.degree = n :=
pn.antisymm (le_degree_of_ne_zero p1)
#align polynomial.degree_eq_of_le_of_coeff_ne_zero Polynomial.degree_eq_of_le_of_coeff_ne_zero
theorem natDegree_eq_of_le_of_coeff_ne_zero (pn : p.natDegree ≤ n) (p1 : p.coeff n ≠ 0) :
p.natDegree = n :=
pn.antisymm (le_natDegree_of_ne_zero p1)
#align polynomial.nat_degree_eq_of_le_of_coeff_ne_zero Polynomial.natDegree_eq_of_le_of_coeff_ne_zero
theorem degree_mono [Semiring S] {f : R[X]} {g : S[X]} (h : f.support ⊆ g.support) :
f.degree ≤ g.degree :=
Finset.sup_mono h
#align polynomial.degree_mono Polynomial.degree_mono
theorem supp_subset_range (h : natDegree p < m) : p.support ⊆ Finset.range m := fun _n hn =>
mem_range.2 <| (le_natDegree_of_mem_supp _ hn).trans_lt h
#align polynomial.supp_subset_range Polynomial.supp_subset_range
theorem supp_subset_range_natDegree_succ : p.support ⊆ Finset.range (natDegree p + 1) :=
supp_subset_range (Nat.lt_succ_self _)
#align polynomial.supp_subset_range_nat_degree_succ Polynomial.supp_subset_range_natDegree_succ
theorem degree_le_degree (h : coeff q (natDegree p) ≠ 0) : degree p ≤ degree q := by
by_cases hp : p = 0
· rw [hp, degree_zero]
exact bot_le
· rw [degree_eq_natDegree hp]
exact le_degree_of_ne_zero h
#align polynomial.degree_le_degree Polynomial.degree_le_degree
theorem natDegree_le_iff_degree_le {n : ℕ} : natDegree p ≤ n ↔ degree p ≤ n :=
WithBot.unbot'_le_iff (fun _ ↦ bot_le)
#align polynomial.nat_degree_le_iff_degree_le Polynomial.natDegree_le_iff_degree_le
theorem natDegree_lt_iff_degree_lt (hp : p ≠ 0) : p.natDegree < n ↔ p.degree < ↑n :=
WithBot.unbot'_lt_iff (absurd · (degree_eq_bot.not.mpr hp))
#align polynomial.nat_degree_lt_iff_degree_lt Polynomial.natDegree_lt_iff_degree_lt
alias ⟨degree_le_of_natDegree_le, natDegree_le_of_degree_le⟩ := natDegree_le_iff_degree_le
#align polynomial.degree_le_of_nat_degree_le Polynomial.degree_le_of_natDegree_le
#align polynomial.nat_degree_le_of_degree_le Polynomial.natDegree_le_of_degree_le
theorem natDegree_le_natDegree [Semiring S] {q : S[X]} (hpq : p.degree ≤ q.degree) :
p.natDegree ≤ q.natDegree :=
WithBot.giUnbot'Bot.gc.monotone_l hpq
#align polynomial.nat_degree_le_nat_degree Polynomial.natDegree_le_natDegree
theorem natDegree_lt_natDegree {p q : R[X]} (hp : p ≠ 0) (hpq : p.degree < q.degree) :
p.natDegree < q.natDegree := by
by_cases hq : q = 0
· exact (not_lt_bot <| hq ▸ hpq).elim
rwa [degree_eq_natDegree hp, degree_eq_natDegree hq, Nat.cast_lt] at hpq
#align polynomial.nat_degree_lt_nat_degree Polynomial.natDegree_lt_natDegree
@[simp]
theorem degree_C (ha : a ≠ 0) : degree (C a) = (0 : WithBot ℕ) := by
rw [degree, ← monomial_zero_left, support_monomial 0 ha, max_eq_sup_coe, sup_singleton,
WithBot.coe_zero]
#align polynomial.degree_C Polynomial.degree_C
theorem degree_C_le : degree (C a) ≤ 0 := by
by_cases h : a = 0
· rw [h, C_0]
exact bot_le
· rw [degree_C h]
#align polynomial.degree_C_le Polynomial.degree_C_le
theorem degree_C_lt : degree (C a) < 1 :=
degree_C_le.trans_lt <| WithBot.coe_lt_coe.mpr zero_lt_one
#align polynomial.degree_C_lt Polynomial.degree_C_lt
theorem degree_one_le : degree (1 : R[X]) ≤ (0 : WithBot ℕ) := by rw [← C_1]; exact degree_C_le
#align polynomial.degree_one_le Polynomial.degree_one_le
@[simp]
theorem natDegree_C (a : R) : natDegree (C a) = 0 := by
by_cases ha : a = 0
· have : C a = 0 := by rw [ha, C_0]
rw [natDegree, degree_eq_bot.2 this, WithBot.unbot'_bot]
· rw [natDegree, degree_C ha, WithBot.unbot_zero']
#align polynomial.nat_degree_C Polynomial.natDegree_C
@[simp]
theorem natDegree_one : natDegree (1 : R[X]) = 0 :=
natDegree_C 1
#align polynomial.nat_degree_one Polynomial.natDegree_one
@[simp]
theorem natDegree_natCast (n : ℕ) : natDegree (n : R[X]) = 0 := by
simp only [← C_eq_natCast, natDegree_C]
#align polynomial.nat_degree_nat_cast Polynomial.natDegree_natCast
@[deprecated (since := "2024-04-17")]
alias natDegree_nat_cast := natDegree_natCast
theorem degree_natCast_le (n : ℕ) : degree (n : R[X]) ≤ 0 := degree_le_of_natDegree_le (by simp)
@[deprecated (since := "2024-04-17")]
alias degree_nat_cast_le := degree_natCast_le
@[simp]
theorem degree_monomial (n : ℕ) (ha : a ≠ 0) : degree (monomial n a) = n := by
rw [degree, support_monomial n ha, max_singleton, Nat.cast_withBot]
#align polynomial.degree_monomial Polynomial.degree_monomial
@[simp]
theorem degree_C_mul_X_pow (n : ℕ) (ha : a ≠ 0) : degree (C a * X ^ n) = n := by
rw [C_mul_X_pow_eq_monomial, degree_monomial n ha]
#align polynomial.degree_C_mul_X_pow Polynomial.degree_C_mul_X_pow
theorem degree_C_mul_X (ha : a ≠ 0) : degree (C a * X) = 1 := by
simpa only [pow_one] using degree_C_mul_X_pow 1 ha
#align polynomial.degree_C_mul_X Polynomial.degree_C_mul_X
theorem degree_monomial_le (n : ℕ) (a : R) : degree (monomial n a) ≤ n :=
letI := Classical.decEq R
if h : a = 0 then by rw [h, (monomial n).map_zero, degree_zero]; exact bot_le
else le_of_eq (degree_monomial n h)
#align polynomial.degree_monomial_le Polynomial.degree_monomial_le
theorem degree_C_mul_X_pow_le (n : ℕ) (a : R) : degree (C a * X ^ n) ≤ n := by
rw [C_mul_X_pow_eq_monomial]
apply degree_monomial_le
#align polynomial.degree_C_mul_X_pow_le Polynomial.degree_C_mul_X_pow_le
theorem degree_C_mul_X_le (a : R) : degree (C a * X) ≤ 1 := by
simpa only [pow_one] using degree_C_mul_X_pow_le 1 a
#align polynomial.degree_C_mul_X_le Polynomial.degree_C_mul_X_le
@[simp]
theorem natDegree_C_mul_X_pow (n : ℕ) (a : R) (ha : a ≠ 0) : natDegree (C a * X ^ n) = n :=
natDegree_eq_of_degree_eq_some (degree_C_mul_X_pow n ha)
#align polynomial.nat_degree_C_mul_X_pow Polynomial.natDegree_C_mul_X_pow
@[simp]
theorem natDegree_C_mul_X (a : R) (ha : a ≠ 0) : natDegree (C a * X) = 1 := by
simpa only [pow_one] using natDegree_C_mul_X_pow 1 a ha
#align polynomial.nat_degree_C_mul_X Polynomial.natDegree_C_mul_X
@[simp]
theorem natDegree_monomial [DecidableEq R] (i : ℕ) (r : R) :
natDegree (monomial i r) = if r = 0 then 0 else i := by
split_ifs with hr
· simp [hr]
· rw [← C_mul_X_pow_eq_monomial, natDegree_C_mul_X_pow i r hr]
#align polynomial.nat_degree_monomial Polynomial.natDegree_monomial
theorem natDegree_monomial_le (a : R) {m : ℕ} : (monomial m a).natDegree ≤ m := by
classical
rw [Polynomial.natDegree_monomial]
split_ifs
exacts [Nat.zero_le _, le_rfl]
#align polynomial.nat_degree_monomial_le Polynomial.natDegree_monomial_le
theorem natDegree_monomial_eq (i : ℕ) {r : R} (r0 : r ≠ 0) : (monomial i r).natDegree = i :=
letI := Classical.decEq R
Eq.trans (natDegree_monomial _ _) (if_neg r0)
#align polynomial.nat_degree_monomial_eq Polynomial.natDegree_monomial_eq
theorem coeff_eq_zero_of_degree_lt (h : degree p < n) : coeff p n = 0 :=
Classical.not_not.1 (mt le_degree_of_ne_zero (not_le_of_gt h))
#align polynomial.coeff_eq_zero_of_degree_lt Polynomial.coeff_eq_zero_of_degree_lt
| Mathlib/Algebra/Polynomial/Degree/Definitions.lean | 354 | 360 | theorem coeff_eq_zero_of_natDegree_lt {p : R[X]} {n : ℕ} (h : p.natDegree < n) :
p.coeff n = 0 := by |
apply coeff_eq_zero_of_degree_lt
by_cases hp : p = 0
· subst hp
exact WithBot.bot_lt_coe n
· rwa [degree_eq_natDegree hp, Nat.cast_lt]
|
/-
Copyright (c) 2020 Anne Baanen. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Anne Baanen
-/
import Mathlib.LinearAlgebra.Matrix.BilinearForm
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Vandermonde
import Mathlib.LinearAlgebra.Trace
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.FieldTheory.Galois
import Mathlib.RingTheory.PowerBasis
import Mathlib.FieldTheory.Minpoly.MinpolyDiv
#align_import ring_theory.trace from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
/-!
# Trace for (finite) ring extensions.
Suppose we have an `R`-algebra `S` with a finite basis. For each `s : S`,
the trace of the linear map given by multiplying by `s` gives information about
the roots of the minimal polynomial of `s` over `R`.
## Main definitions
* `Algebra.trace R S x`: the trace of an element `s` of an `R`-algebra `S`
* `Algebra.traceForm R S`: bilinear form sending `x`, `y` to the trace of `x * y`
* `Algebra.traceMatrix R b`: the matrix whose `(i j)`-th element is the trace of `b i * b j`.
* `Algebra.embeddingsMatrix A C b : Matrix κ (B →ₐ[A] C) C` is the matrix whose
`(i, σ)` coefficient is `σ (b i)`.
* `Algebra.embeddingsMatrixReindex A C b e : Matrix κ κ C` is the matrix whose `(i, j)`
coefficient is `σⱼ (b i)`, where `σⱼ : B →ₐ[A] C` is the embedding corresponding to `j : κ`
given by a bijection `e : κ ≃ (B →ₐ[A] C)`.
## Main results
* `trace_algebraMap_of_basis`, `trace_algebraMap`: if `x : K`, then `Tr_{L/K} x = [L : K] x`
* `trace_trace_of_basis`, `trace_trace`: `Tr_{L/K} (Tr_{F/L} x) = Tr_{F/K} x`
* `trace_eq_sum_roots`: the trace of `x : K(x)` is the sum of all conjugate roots of `x`
* `trace_eq_sum_embeddings`: the trace of `x : K(x)` is the sum of all embeddings of `x` into an
algebraically closed field
* `traceForm_nondegenerate`: the trace form over a separable extension is a nondegenerate
bilinear form
* `traceForm_dualBasis_powerBasis_eq`: The dual basis of a powerbasis `{1, x, x²...}` under the
trace form is `aᵢ / f'(x)`, with `f` being the minpoly of `x` and `f / (X - x) = ∑ aᵢxⁱ`.
## Implementation notes
Typically, the trace is defined specifically for finite field extensions.
The definition is as general as possible and the assumption that we have
fields or that the extension is finite is added to the lemmas as needed.
We only define the trace for left multiplication (`Algebra.leftMulMatrix`,
i.e. `LinearMap.mulLeft`).
For now, the definitions assume `S` is commutative, so the choice doesn't matter anyway.
## References
* https://en.wikipedia.org/wiki/Field_trace
-/
universe u v w z
variable {R S T : Type*} [CommRing R] [CommRing S] [CommRing T]
variable [Algebra R S] [Algebra R T]
variable {K L : Type*} [Field K] [Field L] [Algebra K L]
variable {ι κ : Type w} [Fintype ι]
open FiniteDimensional
open LinearMap (BilinForm)
open LinearMap
open Matrix
open scoped Matrix
namespace Algebra
variable (b : Basis ι R S)
variable (R S)
/-- The trace of an element `s` of an `R`-algebra is the trace of `(s * ·)`,
as an `R`-linear map. -/
noncomputable def trace : S →ₗ[R] R :=
(LinearMap.trace R S).comp (lmul R S).toLinearMap
#align algebra.trace Algebra.trace
variable {S}
-- Not a `simp` lemma since there are more interesting ways to rewrite `trace R S x`,
-- for example `trace_trace`
theorem trace_apply (x) : trace R S x = LinearMap.trace R S (lmul R S x) :=
rfl
#align algebra.trace_apply Algebra.trace_apply
theorem trace_eq_zero_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) :
trace R S = 0 := by ext s; simp [trace_apply, LinearMap.trace, h]
#align algebra.trace_eq_zero_of_not_exists_basis Algebra.trace_eq_zero_of_not_exists_basis
variable {R}
-- Can't be a `simp` lemma because it depends on a choice of basis
theorem trace_eq_matrix_trace [DecidableEq ι] (b : Basis ι R S) (s : S) :
trace R S s = Matrix.trace (Algebra.leftMulMatrix b s) := by
rw [trace_apply, LinearMap.trace_eq_matrix_trace _ b, ← toMatrix_lmul_eq]; rfl
#align algebra.trace_eq_matrix_trace Algebra.trace_eq_matrix_trace
/-- If `x` is in the base field `K`, then the trace is `[L : K] * x`. -/
theorem trace_algebraMap_of_basis (x : R) : trace R S (algebraMap R S x) = Fintype.card ι • x := by
haveI := Classical.decEq ι
rw [trace_apply, LinearMap.trace_eq_matrix_trace R b, Matrix.trace]
convert Finset.sum_const x
simp [-coe_lmul_eq_mul]
#align algebra.trace_algebra_map_of_basis Algebra.trace_algebraMap_of_basis
/-- If `x` is in the base field `K`, then the trace is `[L : K] * x`.
(If `L` is not finite-dimensional over `K`, then `trace` and `finrank` return `0`.)
-/
@[simp]
theorem trace_algebraMap (x : K) : trace K L (algebraMap K L x) = finrank K L • x := by
by_cases H : ∃ s : Finset L, Nonempty (Basis s K L)
· rw [trace_algebraMap_of_basis H.choose_spec.some, finrank_eq_card_basis H.choose_spec.some]
· simp [trace_eq_zero_of_not_exists_basis K H, finrank_eq_zero_of_not_exists_basis_finset H]
#align algebra.trace_algebra_map Algebra.trace_algebraMap
theorem trace_trace_of_basis [Algebra S T] [IsScalarTower R S T] {ι κ : Type*} [Finite ι]
[Finite κ] (b : Basis ι R S) (c : Basis κ S T) (x : T) :
trace R S (trace S T x) = trace R T x := by
haveI := Classical.decEq ι
haveI := Classical.decEq κ
cases nonempty_fintype ι
cases nonempty_fintype κ
rw [trace_eq_matrix_trace (b.smul c), trace_eq_matrix_trace b, trace_eq_matrix_trace c,
Matrix.trace, Matrix.trace, Matrix.trace, ← Finset.univ_product_univ, Finset.sum_product]
refine Finset.sum_congr rfl fun i _ ↦ ?_
simp only [AlgHom.map_sum, smul_leftMulMatrix, Finset.sum_apply,
Matrix.diag, Finset.sum_apply
i (Finset.univ : Finset κ) fun y => leftMulMatrix b (leftMulMatrix c x y y)]
#align algebra.trace_trace_of_basis Algebra.trace_trace_of_basis
theorem trace_comp_trace_of_basis [Algebra S T] [IsScalarTower R S T] {ι κ : Type*} [Finite ι]
[Finite κ] (b : Basis ι R S) (c : Basis κ S T) :
(trace R S).comp ((trace S T).restrictScalars R) = trace R T := by
ext
rw [LinearMap.comp_apply, LinearMap.restrictScalars_apply, trace_trace_of_basis b c]
#align algebra.trace_comp_trace_of_basis Algebra.trace_comp_trace_of_basis
@[simp]
theorem trace_trace [Algebra K T] [Algebra L T] [IsScalarTower K L T] [FiniteDimensional K L]
[FiniteDimensional L T] (x : T) : trace K L (trace L T x) = trace K T x :=
trace_trace_of_basis (Basis.ofVectorSpace K L) (Basis.ofVectorSpace L T) x
#align algebra.trace_trace Algebra.trace_trace
@[simp]
theorem trace_comp_trace [Algebra K T] [Algebra L T] [IsScalarTower K L T] [FiniteDimensional K L]
[FiniteDimensional L T] : (trace K L).comp ((trace L T).restrictScalars K) = trace K T := by
ext; rw [LinearMap.comp_apply, LinearMap.restrictScalars_apply, trace_trace]
#align algebra.trace_comp_trace Algebra.trace_comp_trace
@[simp]
theorem trace_prod_apply [Module.Free R S] [Module.Free R T] [Module.Finite R S] [Module.Finite R T]
(x : S × T) : trace R (S × T) x = trace R S x.fst + trace R T x.snd := by
nontriviality R
let f := (lmul R S).toLinearMap.prodMap (lmul R T).toLinearMap
have : (lmul R (S × T)).toLinearMap = (prodMapLinear R S T S T R).comp f :=
LinearMap.ext₂ Prod.mul_def
simp_rw [trace, this]
exact trace_prodMap' _ _
#align algebra.trace_prod_apply Algebra.trace_prod_apply
theorem trace_prod [Module.Free R S] [Module.Free R T] [Module.Finite R S] [Module.Finite R T] :
trace R (S × T) = (trace R S).coprod (trace R T) :=
LinearMap.ext fun p => by rw [coprod_apply, trace_prod_apply]
#align algebra.trace_prod Algebra.trace_prod
section TraceForm
variable (R S)
/-- The `traceForm` maps `x y : S` to the trace of `x * y`.
It is a symmetric bilinear form and is nondegenerate if the extension is separable. -/
noncomputable def traceForm : BilinForm R S :=
LinearMap.compr₂ (lmul R S).toLinearMap (trace R S)
#align algebra.trace_form Algebra.traceForm
variable {S}
-- This is a nicer lemma than the one produced by `@[simps] def traceForm`.
@[simp]
theorem traceForm_apply (x y : S) : traceForm R S x y = trace R S (x * y) :=
rfl
#align algebra.trace_form_apply Algebra.traceForm_apply
theorem traceForm_isSymm : (traceForm R S).IsSymm := fun _ _ => congr_arg (trace R S) (mul_comm _ _)
#align algebra.trace_form_is_symm Algebra.traceForm_isSymm
theorem traceForm_toMatrix [DecidableEq ι] (i j) :
BilinForm.toMatrix b (traceForm R S) i j = trace R S (b i * b j) := by
rw [BilinForm.toMatrix_apply, traceForm_apply]
#align algebra.trace_form_to_matrix Algebra.traceForm_toMatrix
theorem traceForm_toMatrix_powerBasis (h : PowerBasis R S) :
BilinForm.toMatrix h.basis (traceForm R S) = of fun i j => trace R S (h.gen ^ (i.1 + j.1)) := by
ext; rw [traceForm_toMatrix, of_apply, pow_add, h.basis_eq_pow, h.basis_eq_pow]
#align algebra.trace_form_to_matrix_power_basis Algebra.traceForm_toMatrix_powerBasis
end TraceForm
end Algebra
section EqSumRoots
open Algebra Polynomial
variable {F : Type*} [Field F]
variable [Algebra K S] [Algebra K F]
/-- Given `pb : PowerBasis K S`, the trace of `pb.gen` is `-(minpoly K pb.gen).nextCoeff`. -/
theorem PowerBasis.trace_gen_eq_nextCoeff_minpoly [Nontrivial S] (pb : PowerBasis K S) :
Algebra.trace K S pb.gen = -(minpoly K pb.gen).nextCoeff := by
have d_pos : 0 < pb.dim := PowerBasis.dim_pos pb
have d_pos' : 0 < (minpoly K pb.gen).natDegree := by simpa
haveI : Nonempty (Fin pb.dim) := ⟨⟨0, d_pos⟩⟩
rw [trace_eq_matrix_trace pb.basis, trace_eq_neg_charpoly_coeff, charpoly_leftMulMatrix, ←
pb.natDegree_minpoly, Fintype.card_fin, ← nextCoeff_of_natDegree_pos d_pos']
#align power_basis.trace_gen_eq_next_coeff_minpoly PowerBasis.trace_gen_eq_nextCoeff_minpoly
/-- Given `pb : PowerBasis K S`, then the trace of `pb.gen` is
`((minpoly K pb.gen).aroots F).sum`. -/
theorem PowerBasis.trace_gen_eq_sum_roots [Nontrivial S] (pb : PowerBasis K S)
(hf : (minpoly K pb.gen).Splits (algebraMap K F)) :
algebraMap K F (trace K S pb.gen) = ((minpoly K pb.gen).aroots F).sum := by
rw [PowerBasis.trace_gen_eq_nextCoeff_minpoly, RingHom.map_neg, ←
nextCoeff_map (algebraMap K F).injective,
sum_roots_eq_nextCoeff_of_monic_of_split ((minpoly.monic (PowerBasis.isIntegral_gen _)).map _)
((splits_id_iff_splits _).2 hf),
neg_neg]
#align power_basis.trace_gen_eq_sum_roots PowerBasis.trace_gen_eq_sum_roots
namespace IntermediateField.AdjoinSimple
open IntermediateField
theorem trace_gen_eq_zero {x : L} (hx : ¬IsIntegral K x) :
Algebra.trace K K⟮x⟯ (AdjoinSimple.gen K x) = 0 := by
rw [trace_eq_zero_of_not_exists_basis, LinearMap.zero_apply]
contrapose! hx
obtain ⟨s, ⟨b⟩⟩ := hx
refine .of_mem_of_fg K⟮x⟯.toSubalgebra ?_ x ?_
· exact (Submodule.fg_iff_finiteDimensional _).mpr (FiniteDimensional.of_fintype_basis b)
· exact subset_adjoin K _ (Set.mem_singleton x)
#align intermediate_field.adjoin_simple.trace_gen_eq_zero IntermediateField.AdjoinSimple.trace_gen_eq_zero
theorem trace_gen_eq_sum_roots (x : L) (hf : (minpoly K x).Splits (algebraMap K F)) :
algebraMap K F (trace K K⟮x⟯ (AdjoinSimple.gen K x)) =
((minpoly K x).aroots F).sum := by
have injKxL := (algebraMap K⟮x⟯ L).injective
by_cases hx : IsIntegral K x; swap
· simp [minpoly.eq_zero hx, trace_gen_eq_zero hx, aroots_def]
rw [← adjoin.powerBasis_gen hx, (adjoin.powerBasis hx).trace_gen_eq_sum_roots] <;>
rw [adjoin.powerBasis_gen hx, ← minpoly.algebraMap_eq injKxL] <;>
try simp only [AdjoinSimple.algebraMap_gen _ _]
exact hf
#align intermediate_field.adjoin_simple.trace_gen_eq_sum_roots IntermediateField.AdjoinSimple.trace_gen_eq_sum_roots
end IntermediateField.AdjoinSimple
open IntermediateField
variable (K)
theorem trace_eq_trace_adjoin [FiniteDimensional K L] (x : L) :
Algebra.trace K L x = finrank K⟮x⟯ L • trace K K⟮x⟯ (AdjoinSimple.gen K x) := by
-- Porting note: `conv` was
-- `conv in x => rw [← IntermediateField.AdjoinSimple.algebraMap_gen K x]`
-- and it was after the first `rw`.
conv =>
lhs
rw [← IntermediateField.AdjoinSimple.algebraMap_gen K x]
rw [← trace_trace (L := K⟮x⟯), trace_algebraMap, LinearMap.map_smul_of_tower]
#align trace_eq_trace_adjoin trace_eq_trace_adjoin
variable {K}
theorem trace_eq_sum_roots [FiniteDimensional K L] {x : L}
(hF : (minpoly K x).Splits (algebraMap K F)) :
algebraMap K F (Algebra.trace K L x) =
finrank K⟮x⟯ L • ((minpoly K x).aroots F).sum := by
rw [trace_eq_trace_adjoin K x, Algebra.smul_def, RingHom.map_mul, ← Algebra.smul_def,
IntermediateField.AdjoinSimple.trace_gen_eq_sum_roots _ hF, IsScalarTower.algebraMap_smul]
#align trace_eq_sum_roots trace_eq_sum_roots
end EqSumRoots
variable {F : Type*} [Field F]
variable [Algebra R L] [Algebra L F] [Algebra R F] [IsScalarTower R L F]
open Polynomial
attribute [-instance] Field.toEuclideanDomain
theorem Algebra.isIntegral_trace [FiniteDimensional L F] {x : F} (hx : IsIntegral R x) :
IsIntegral R (Algebra.trace L F x) := by
have hx' : IsIntegral L x := hx.tower_top
rw [← isIntegral_algebraMap_iff (algebraMap L (AlgebraicClosure F)).injective, trace_eq_sum_roots]
· refine (IsIntegral.multiset_sum ?_).nsmul _
intro y hy
rw [mem_roots_map (minpoly.ne_zero hx')] at hy
use minpoly R x, minpoly.monic hx
rw [← aeval_def] at hy ⊢
exact minpoly.aeval_of_isScalarTower R x y hy
· apply IsAlgClosed.splits_codomain
#align algebra.is_integral_trace Algebra.isIntegral_trace
lemma Algebra.trace_eq_of_algEquiv {A B C : Type*} [CommRing A] [CommRing B] [CommRing C]
[Algebra A B] [Algebra A C] (e : B ≃ₐ[A] C) (x) :
Algebra.trace A C (e x) = Algebra.trace A B x := by
simp_rw [Algebra.trace_apply, ← LinearMap.trace_conj' _ e.toLinearEquiv]
congr; ext; simp [LinearEquiv.conj_apply]
lemma Algebra.trace_eq_of_ringEquiv {A B C : Type*} [CommRing A] [CommRing B] [CommRing C]
[Algebra A C] [Algebra B C] (e : A ≃+* B) (he : (algebraMap B C).comp e = algebraMap A C) (x) :
e (Algebra.trace A C x) = Algebra.trace B C x := by
classical
by_cases h : ∃ s : Finset C, Nonempty (Basis s B C)
· obtain ⟨s, ⟨b⟩⟩ := h
letI : Algebra A B := RingHom.toAlgebra e
letI : IsScalarTower A B C := IsScalarTower.of_algebraMap_eq' he.symm
rw [Algebra.trace_eq_matrix_trace b,
Algebra.trace_eq_matrix_trace (b.mapCoeffs e.symm (by simp [Algebra.smul_def, ← he]))]
show e.toAddMonoidHom _ = _
rw [AddMonoidHom.map_trace]
congr
ext i j
simp [leftMulMatrix_apply, LinearMap.toMatrix_apply]
rw [trace_eq_zero_of_not_exists_basis _ h, trace_eq_zero_of_not_exists_basis,
LinearMap.zero_apply, LinearMap.zero_apply, map_zero]
intro ⟨s, ⟨b⟩⟩
exact h ⟨s, ⟨b.mapCoeffs e (by simp [Algebra.smul_def, ← he])⟩⟩
lemma Algebra.trace_eq_of_equiv_equiv {A₁ B₁ A₂ B₂ : Type*} [CommRing A₁] [CommRing B₁]
[CommRing A₂] [CommRing B₂] [Algebra A₁ B₁] [Algebra A₂ B₂] (e₁ : A₁ ≃+* A₂) (e₂ : B₁ ≃+* B₂)
(he : RingHom.comp (algebraMap A₂ B₂) ↑e₁ = RingHom.comp ↑e₂ (algebraMap A₁ B₁)) (x) :
Algebra.trace A₁ B₁ x = e₁.symm (Algebra.trace A₂ B₂ (e₂ x)) := by
letI := (RingHom.comp (e₂ : B₁ →+* B₂) (algebraMap A₁ B₁)).toAlgebra
let e' : B₁ ≃ₐ[A₁] B₂ := { e₂ with commutes' := fun _ ↦ rfl }
rw [← Algebra.trace_eq_of_ringEquiv e₁ he, ← Algebra.trace_eq_of_algEquiv e',
RingEquiv.symm_apply_apply]
rfl
section EqSumEmbeddings
variable [Algebra K F] [IsScalarTower K L F]
open Algebra IntermediateField
variable (F) (E : Type*) [Field E] [Algebra K E]
theorem trace_eq_sum_embeddings_gen (pb : PowerBasis K L)
(hE : (minpoly K pb.gen).Splits (algebraMap K E)) (hfx : (minpoly K pb.gen).Separable) :
algebraMap K E (Algebra.trace K L pb.gen) =
(@Finset.univ _ (PowerBasis.AlgHom.fintype pb)).sum fun σ => σ pb.gen := by
letI := Classical.decEq E
-- Porting note: the following `letI` was not needed.
letI : Fintype (L →ₐ[K] E) := PowerBasis.AlgHom.fintype pb
rw [pb.trace_gen_eq_sum_roots hE, Fintype.sum_equiv pb.liftEquiv', Finset.sum_mem_multiset,
Finset.sum_eq_multiset_sum, Multiset.toFinset_val, Multiset.dedup_eq_self.mpr _,
Multiset.map_id]
· exact nodup_roots ((separable_map _).mpr hfx)
-- Porting note: the following goal does not exist in mathlib3.
· exact (fun x => x.1)
· intro x; rfl
· intro σ
rw [PowerBasis.liftEquiv'_apply_coe]
#align trace_eq_sum_embeddings_gen trace_eq_sum_embeddings_gen
variable [IsAlgClosed E]
theorem sum_embeddings_eq_finrank_mul [FiniteDimensional K F] [IsSeparable K F]
(pb : PowerBasis K L) :
∑ σ : F →ₐ[K] E, σ (algebraMap L F pb.gen) =
finrank L F •
(@Finset.univ _ (PowerBasis.AlgHom.fintype pb)).sum fun σ : L →ₐ[K] E => σ pb.gen := by
haveI : FiniteDimensional L F := FiniteDimensional.right K L F
haveI : IsSeparable L F := isSeparable_tower_top_of_isSeparable K L F
letI : Fintype (L →ₐ[K] E) := PowerBasis.AlgHom.fintype pb
letI : ∀ f : L →ₐ[K] E, Fintype (haveI := f.toRingHom.toAlgebra; AlgHom L F E) := ?_
· rw [Fintype.sum_equiv algHomEquivSigma (fun σ : F →ₐ[K] E => _) fun σ => σ.1 pb.gen, ←
Finset.univ_sigma_univ, Finset.sum_sigma, ← Finset.sum_nsmul]
· refine Finset.sum_congr rfl fun σ _ => ?_
letI : Algebra L E := σ.toRingHom.toAlgebra
-- Porting note: `Finset.card_univ` was inside `simp only`.
simp only [Finset.sum_const]
congr
rw [← AlgHom.card L F E]
exact Finset.card_univ (α := F →ₐ[L] E)
· intro σ
simp only [algHomEquivSigma, Equiv.coe_fn_mk, AlgHom.restrictDomain, AlgHom.comp_apply,
IsScalarTower.coe_toAlgHom']
#align sum_embeddings_eq_finrank_mul sum_embeddings_eq_finrank_mul
theorem trace_eq_sum_embeddings [FiniteDimensional K L] [IsSeparable K L] {x : L} :
algebraMap K E (Algebra.trace K L x) = ∑ σ : L →ₐ[K] E, σ x := by
have hx := IsSeparable.isIntegral K x
let pb := adjoin.powerBasis hx
rw [trace_eq_trace_adjoin K x, Algebra.smul_def, RingHom.map_mul, ← adjoin.powerBasis_gen hx,
trace_eq_sum_embeddings_gen E pb (IsAlgClosed.splits_codomain _)]
-- Porting note: the following `convert` was `exact`, with `← algebra.smul_def, algebra_map_smul`
-- in the previous `rw`.
· convert (sum_embeddings_eq_finrank_mul L E pb).symm
ext
simp
· haveI := isSeparable_tower_bot_of_isSeparable K K⟮x⟯ L
exact IsSeparable.separable K _
#align trace_eq_sum_embeddings trace_eq_sum_embeddings
theorem trace_eq_sum_automorphisms (x : L) [FiniteDimensional K L] [IsGalois K L] :
algebraMap K L (Algebra.trace K L x) = ∑ σ : L ≃ₐ[K] L, σ x := by
apply NoZeroSMulDivisors.algebraMap_injective L (AlgebraicClosure L)
rw [_root_.map_sum (algebraMap L (AlgebraicClosure L))]
rw [← Fintype.sum_equiv (Normal.algHomEquivAut K (AlgebraicClosure L) L)]
· rw [← trace_eq_sum_embeddings (AlgebraicClosure L)]
· simp only [algebraMap_eq_smul_one]
-- Porting note: `smul_one_smul` was in the `simp only`.
apply smul_one_smul
· intro σ
simp only [Normal.algHomEquivAut, AlgHom.restrictNormal', Equiv.coe_fn_mk,
AlgEquiv.coe_ofBijective, AlgHom.restrictNormal_commutes, id.map_eq_id, RingHom.id_apply]
#align trace_eq_sum_automorphisms trace_eq_sum_automorphisms
end EqSumEmbeddings
section DetNeZero
namespace Algebra
variable (A : Type u) {B : Type v} (C : Type z)
variable [CommRing A] [CommRing B] [Algebra A B] [CommRing C] [Algebra A C]
open Finset
/-- Given an `A`-algebra `B` and `b`, a `κ`-indexed family of elements of `B`, we define
`traceMatrix A b` as the matrix whose `(i j)`-th element is the trace of `b i * b j`. -/
noncomputable def traceMatrix (b : κ → B) : Matrix κ κ A :=
of fun i j => traceForm A B (b i) (b j)
#align algebra.trace_matrix Algebra.traceMatrix
-- TODO: set as an equation lemma for `traceMatrix`, see mathlib4#3024
@[simp]
theorem traceMatrix_apply (b : κ → B) (i j) : traceMatrix A b i j = traceForm A B (b i) (b j) :=
rfl
#align algebra.trace_matrix_apply Algebra.traceMatrix_apply
theorem traceMatrix_reindex {κ' : Type*} (b : Basis κ A B) (f : κ ≃ κ') :
traceMatrix A (b.reindex f) = reindex f f (traceMatrix A b) := by ext (x y); simp
#align algebra.trace_matrix_reindex Algebra.traceMatrix_reindex
variable {A}
theorem traceMatrix_of_matrix_vecMul [Fintype κ] (b : κ → B) (P : Matrix κ κ A) :
traceMatrix A (b ᵥ* P.map (algebraMap A B)) = Pᵀ * traceMatrix A b * P := by
ext (α β)
rw [traceMatrix_apply, vecMul, dotProduct, vecMul, dotProduct, Matrix.mul_apply,
BilinForm.sum_left,
Fintype.sum_congr _ _ fun i : κ =>
BilinForm.sum_right _ _ (b i * P.map (algebraMap A B) i α) fun y : κ =>
b y * P.map (algebraMap A B) y β,
sum_comm]
congr; ext x
rw [Matrix.mul_apply, sum_mul]
congr; ext y
rw [map_apply, traceForm_apply, mul_comm (b y), ← smul_def]
simp only [id.smul_eq_mul, RingHom.id_apply, map_apply, transpose_apply, LinearMap.map_smulₛₗ,
traceForm_apply, Algebra.smul_mul_assoc]
rw [mul_comm (b x), ← smul_def]
ring_nf
rw [mul_assoc]
simp [mul_comm]
#align algebra.trace_matrix_of_matrix_vec_mul Algebra.traceMatrix_of_matrix_vecMul
theorem traceMatrix_of_matrix_mulVec [Fintype κ] (b : κ → B) (P : Matrix κ κ A) :
traceMatrix A (P.map (algebraMap A B) *ᵥ b) = P * traceMatrix A b * Pᵀ := by
refine AddEquiv.injective (transposeAddEquiv κ κ A) ?_
rw [transposeAddEquiv_apply, transposeAddEquiv_apply, ← vecMul_transpose, ← transpose_map,
traceMatrix_of_matrix_vecMul, transpose_transpose]
#align algebra.trace_matrix_of_matrix_mul_vec Algebra.traceMatrix_of_matrix_mulVec
theorem traceMatrix_of_basis [Fintype κ] [DecidableEq κ] (b : Basis κ A B) :
traceMatrix A b = BilinForm.toMatrix b (traceForm A B) := by
ext (i j)
rw [traceMatrix_apply, traceForm_apply, traceForm_toMatrix]
#align algebra.trace_matrix_of_basis Algebra.traceMatrix_of_basis
| Mathlib/RingTheory/Trace.lean | 502 | 522 | theorem traceMatrix_of_basis_mulVec (b : Basis ι A B) (z : B) :
traceMatrix A b *ᵥ b.equivFun z = fun i => trace A B (z * b i) := by |
ext i
rw [← col_apply (traceMatrix A b *ᵥ b.equivFun z) i Unit.unit, col_mulVec,
Matrix.mul_apply, traceMatrix]
simp only [col_apply, traceForm_apply]
conv_lhs =>
congr
rfl
ext
rw [mul_comm _ (b.equivFun z _), ← smul_eq_mul, of_apply, ← LinearMap.map_smul]
rw [← _root_.map_sum]
congr
conv_lhs =>
congr
rfl
ext
rw [← mul_smul_comm]
rw [← Finset.mul_sum, mul_comm z]
congr
rw [b.sum_equivFun]
|
/-
Copyright (c) 2019 Johannes Hölzl, Zhouhang Zhou. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Zhouhang Zhou
-/
import Mathlib.MeasureTheory.Integral.Lebesgue
import Mathlib.Order.Filter.Germ
import Mathlib.Topology.ContinuousFunction.Algebra
import Mathlib.MeasureTheory.Function.StronglyMeasurable.Basic
#align_import measure_theory.function.ae_eq_fun from "leanprover-community/mathlib"@"f2ce6086713c78a7f880485f7917ea547a215982"
/-!
# Almost everywhere equal functions
We build a space of equivalence classes of functions, where two functions are treated as identical
if they are almost everywhere equal. We form the set of equivalence classes under the relation of
being almost everywhere equal, which is sometimes known as the `L⁰` space.
To use this space as a basis for the `L^p` spaces and for the Bochner integral, we consider
equivalence classes of strongly measurable functions (or, equivalently, of almost everywhere
strongly measurable functions.)
See `L1Space.lean` for `L¹` space.
## Notation
* `α →ₘ[μ] β` is the type of `L⁰` space, where `α` is a measurable space, `β` is a topological
space, and `μ` is a measure on `α`. `f : α →ₘ β` is a "function" in `L⁰`.
In comments, `[f]` is also used to denote an `L⁰` function.
`ₘ` can be typed as `\_m`. Sometimes it is shown as a box if font is missing.
## Main statements
* The linear structure of `L⁰` :
Addition and scalar multiplication are defined on `L⁰` in the natural way, i.e.,
`[f] + [g] := [f + g]`, `c • [f] := [c • f]`. So defined, `α →ₘ β` inherits the linear structure
of `β`. For example, if `β` is a module, then `α →ₘ β` is a module over the same ring.
See `mk_add_mk`, `neg_mk`, `mk_sub_mk`, `smul_mk`,
`add_toFun`, `neg_toFun`, `sub_toFun`, `smul_toFun`
* The order structure of `L⁰` :
`≤` can be defined in a similar way: `[f] ≤ [g]` if `f a ≤ g a` for almost all `a` in domain.
And `α →ₘ β` inherits the preorder and partial order of `β`.
TODO: Define `sup` and `inf` on `L⁰` so that it forms a lattice. It seems that `β` must be a
linear order, since otherwise `f ⊔ g` may not be a measurable function.
## Implementation notes
* `f.toFun` : To find a representative of `f : α →ₘ β`, use the coercion `(f : α → β)`, which
is implemented as `f.toFun`.
For each operation `op` in `L⁰`, there is a lemma called `coe_fn_op`,
characterizing, say, `(f op g : α → β)`.
* `ae_eq_fun.mk` : To constructs an `L⁰` function `α →ₘ β` from an almost everywhere strongly
measurable function `f : α → β`, use `ae_eq_fun.mk`
* `comp` : Use `comp g f` to get `[g ∘ f]` from `g : β → γ` and `[f] : α →ₘ γ` when `g` is
continuous. Use `comp_measurable` if `g` is only measurable (this requires the
target space to be second countable).
* `comp₂` : Use `comp₂ g f₁ f₂` to get `[fun a ↦ g (f₁ a) (f₂ a)]`.
For example, `[f + g]` is `comp₂ (+)`
## Tags
function space, almost everywhere equal, `L⁰`, ae_eq_fun
-/
noncomputable section
open scoped Classical
open ENNReal Topology
open Set Filter TopologicalSpace ENNReal EMetric MeasureTheory Function
variable {α β γ δ : Type*} [MeasurableSpace α] {μ ν : Measure α}
namespace MeasureTheory
section MeasurableSpace
variable [TopologicalSpace β]
variable (β)
/-- The equivalence relation of being almost everywhere equal for almost everywhere strongly
measurable functions. -/
def Measure.aeEqSetoid (μ : Measure α) : Setoid { f : α → β // AEStronglyMeasurable f μ } :=
⟨fun f g => (f : α → β) =ᵐ[μ] g, fun {f} => ae_eq_refl f.val, fun {_ _} => ae_eq_symm,
fun {_ _ _} => ae_eq_trans⟩
#align measure_theory.measure.ae_eq_setoid MeasureTheory.Measure.aeEqSetoid
variable (α)
/-- The space of equivalence classes of almost everywhere strongly measurable functions, where two
strongly measurable functions are equivalent if they agree almost everywhere, i.e.,
they differ on a set of measure `0`. -/
def AEEqFun (μ : Measure α) : Type _ :=
Quotient (μ.aeEqSetoid β)
#align measure_theory.ae_eq_fun MeasureTheory.AEEqFun
variable {α β}
@[inherit_doc MeasureTheory.AEEqFun]
notation:25 α " →ₘ[" μ "] " β => AEEqFun α β μ
end MeasurableSpace
namespace AEEqFun
variable [TopologicalSpace β] [TopologicalSpace γ] [TopologicalSpace δ]
/-- Construct the equivalence class `[f]` of an almost everywhere measurable function `f`, based
on the equivalence relation of being almost everywhere equal. -/
def mk {β : Type*} [TopologicalSpace β] (f : α → β) (hf : AEStronglyMeasurable f μ) : α →ₘ[μ] β :=
Quotient.mk'' ⟨f, hf⟩
#align measure_theory.ae_eq_fun.mk MeasureTheory.AEEqFun.mk
/-- Coercion from a space of equivalence classes of almost everywhere strongly measurable
functions to functions. -/
@[coe]
def cast (f : α →ₘ[μ] β) : α → β :=
AEStronglyMeasurable.mk _ (Quotient.out' f : { f : α → β // AEStronglyMeasurable f μ }).2
/-- A measurable representative of an `AEEqFun` [f] -/
instance instCoeFun : CoeFun (α →ₘ[μ] β) fun _ => α → β := ⟨cast⟩
#align measure_theory.ae_eq_fun.has_coe_to_fun MeasureTheory.AEEqFun.instCoeFun
protected theorem stronglyMeasurable (f : α →ₘ[μ] β) : StronglyMeasurable f :=
AEStronglyMeasurable.stronglyMeasurable_mk _
#align measure_theory.ae_eq_fun.strongly_measurable MeasureTheory.AEEqFun.stronglyMeasurable
protected theorem aestronglyMeasurable (f : α →ₘ[μ] β) : AEStronglyMeasurable f μ :=
f.stronglyMeasurable.aestronglyMeasurable
#align measure_theory.ae_eq_fun.ae_strongly_measurable MeasureTheory.AEEqFun.aestronglyMeasurable
protected theorem measurable [PseudoMetrizableSpace β] [MeasurableSpace β] [BorelSpace β]
(f : α →ₘ[μ] β) : Measurable f :=
AEStronglyMeasurable.measurable_mk _
#align measure_theory.ae_eq_fun.measurable MeasureTheory.AEEqFun.measurable
protected theorem aemeasurable [PseudoMetrizableSpace β] [MeasurableSpace β] [BorelSpace β]
(f : α →ₘ[μ] β) : AEMeasurable f μ :=
f.measurable.aemeasurable
#align measure_theory.ae_eq_fun.ae_measurable MeasureTheory.AEEqFun.aemeasurable
@[simp]
theorem quot_mk_eq_mk (f : α → β) (hf) :
(Quot.mk (@Setoid.r _ <| μ.aeEqSetoid β) ⟨f, hf⟩ : α →ₘ[μ] β) = mk f hf :=
rfl
#align measure_theory.ae_eq_fun.quot_mk_eq_mk MeasureTheory.AEEqFun.quot_mk_eq_mk
@[simp]
theorem mk_eq_mk {f g : α → β} {hf hg} : (mk f hf : α →ₘ[μ] β) = mk g hg ↔ f =ᵐ[μ] g :=
Quotient.eq''
#align measure_theory.ae_eq_fun.mk_eq_mk MeasureTheory.AEEqFun.mk_eq_mk
@[simp]
theorem mk_coeFn (f : α →ₘ[μ] β) : mk f f.aestronglyMeasurable = f := by
conv_rhs => rw [← Quotient.out_eq' f]
set g : { f : α → β // AEStronglyMeasurable f μ } := Quotient.out' f
have : g = ⟨g.1, g.2⟩ := Subtype.eq rfl
rw [this, ← mk, mk_eq_mk]
exact (AEStronglyMeasurable.ae_eq_mk _).symm
#align measure_theory.ae_eq_fun.mk_coe_fn MeasureTheory.AEEqFun.mk_coeFn
@[ext]
theorem ext {f g : α →ₘ[μ] β} (h : f =ᵐ[μ] g) : f = g := by
rwa [← f.mk_coeFn, ← g.mk_coeFn, mk_eq_mk]
#align measure_theory.ae_eq_fun.ext MeasureTheory.AEEqFun.ext
theorem ext_iff {f g : α →ₘ[μ] β} : f = g ↔ f =ᵐ[μ] g :=
⟨fun h => by rw [h], fun h => ext h⟩
#align measure_theory.ae_eq_fun.ext_iff MeasureTheory.AEEqFun.ext_iff
theorem coeFn_mk (f : α → β) (hf) : (mk f hf : α →ₘ[μ] β) =ᵐ[μ] f := by
apply (AEStronglyMeasurable.ae_eq_mk _).symm.trans
exact @Quotient.mk_out' _ (μ.aeEqSetoid β) (⟨f, hf⟩ : { f // AEStronglyMeasurable f μ })
#align measure_theory.ae_eq_fun.coe_fn_mk MeasureTheory.AEEqFun.coeFn_mk
@[elab_as_elim]
theorem induction_on (f : α →ₘ[μ] β) {p : (α →ₘ[μ] β) → Prop} (H : ∀ f hf, p (mk f hf)) : p f :=
Quotient.inductionOn' f <| Subtype.forall.2 H
#align measure_theory.ae_eq_fun.induction_on MeasureTheory.AEEqFun.induction_on
@[elab_as_elim]
theorem induction_on₂ {α' β' : Type*} [MeasurableSpace α'] [TopologicalSpace β'] {μ' : Measure α'}
(f : α →ₘ[μ] β) (f' : α' →ₘ[μ'] β') {p : (α →ₘ[μ] β) → (α' →ₘ[μ'] β') → Prop}
(H : ∀ f hf f' hf', p (mk f hf) (mk f' hf')) : p f f' :=
induction_on f fun f hf => induction_on f' <| H f hf
#align measure_theory.ae_eq_fun.induction_on₂ MeasureTheory.AEEqFun.induction_on₂
@[elab_as_elim]
theorem induction_on₃ {α' β' : Type*} [MeasurableSpace α'] [TopologicalSpace β'] {μ' : Measure α'}
{α'' β'' : Type*} [MeasurableSpace α''] [TopologicalSpace β''] {μ'' : Measure α''}
(f : α →ₘ[μ] β) (f' : α' →ₘ[μ'] β') (f'' : α'' →ₘ[μ''] β'')
{p : (α →ₘ[μ] β) → (α' →ₘ[μ'] β') → (α'' →ₘ[μ''] β'') → Prop}
(H : ∀ f hf f' hf' f'' hf'', p (mk f hf) (mk f' hf') (mk f'' hf'')) : p f f' f'' :=
induction_on f fun f hf => induction_on₂ f' f'' <| H f hf
#align measure_theory.ae_eq_fun.induction_on₃ MeasureTheory.AEEqFun.induction_on₃
/-!
### Composition of an a.e. equal function with a (quasi) measure preserving function
-/
section compQuasiMeasurePreserving
variable [MeasurableSpace β] {ν : MeasureTheory.Measure β} {f : α → β}
open MeasureTheory.Measure (QuasiMeasurePreserving)
/-- Composition of an almost everywhere equal function and a quasi measure preserving function.
See also `AEEqFun.compMeasurePreserving`. -/
def compQuasiMeasurePreserving (g : β →ₘ[ν] γ) (f : α → β) (hf : QuasiMeasurePreserving f μ ν) :
α →ₘ[μ] γ :=
Quotient.liftOn' g (fun g ↦ mk (g ∘ f) <| g.2.comp_quasiMeasurePreserving hf) fun _ _ h ↦
mk_eq_mk.2 <| h.comp_tendsto hf.tendsto_ae
@[simp]
theorem compQuasiMeasurePreserving_mk {g : β → γ} (hg : AEStronglyMeasurable g ν)
(hf : QuasiMeasurePreserving f μ ν) :
(mk g hg).compQuasiMeasurePreserving f hf = mk (g ∘ f) (hg.comp_quasiMeasurePreserving hf) :=
rfl
theorem compQuasiMeasurePreserving_eq_mk (g : β →ₘ[ν] γ) (hf : QuasiMeasurePreserving f μ ν) :
g.compQuasiMeasurePreserving f hf =
mk (g ∘ f) (g.aestronglyMeasurable.comp_quasiMeasurePreserving hf) := by
rw [← compQuasiMeasurePreserving_mk g.aestronglyMeasurable hf, mk_coeFn]
theorem coeFn_compQuasiMeasurePreserving (g : β →ₘ[ν] γ) (hf : QuasiMeasurePreserving f μ ν) :
g.compQuasiMeasurePreserving f hf =ᵐ[μ] g ∘ f := by
rw [compQuasiMeasurePreserving_eq_mk]
apply coeFn_mk
end compQuasiMeasurePreserving
section compMeasurePreserving
variable [MeasurableSpace β] {ν : MeasureTheory.Measure β} {f : α → β} {g : β → γ}
/-- Composition of an almost everywhere equal function and a quasi measure preserving function.
This is an important special case of `AEEqFun.compQuasiMeasurePreserving`. We use a separate
definition so that lemmas that need `f` to be measure preserving can be `@[simp]` lemmas. -/
def compMeasurePreserving (g : β →ₘ[ν] γ) (f : α → β) (hf : MeasurePreserving f μ ν) : α →ₘ[μ] γ :=
g.compQuasiMeasurePreserving f hf.quasiMeasurePreserving
@[simp]
theorem compMeasurePreserving_mk (hg : AEStronglyMeasurable g ν) (hf : MeasurePreserving f μ ν) :
(mk g hg).compMeasurePreserving f hf =
mk (g ∘ f) (hg.comp_quasiMeasurePreserving hf.quasiMeasurePreserving) :=
rfl
theorem compMeasurePreserving_eq_mk (g : β →ₘ[ν] γ) (hf : MeasurePreserving f μ ν) :
g.compMeasurePreserving f hf =
mk (g ∘ f) (g.aestronglyMeasurable.comp_quasiMeasurePreserving hf.quasiMeasurePreserving) :=
g.compQuasiMeasurePreserving_eq_mk _
theorem coeFn_compMeasurePreserving (g : β →ₘ[ν] γ) (hf : MeasurePreserving f μ ν) :
g.compMeasurePreserving f hf =ᵐ[μ] g ∘ f :=
g.coeFn_compQuasiMeasurePreserving _
end compMeasurePreserving
/-- Given a continuous function `g : β → γ`, and an almost everywhere equal function `[f] : α →ₘ β`,
return the equivalence class of `g ∘ f`, i.e., the almost everywhere equal function
`[g ∘ f] : α →ₘ γ`. -/
def comp (g : β → γ) (hg : Continuous g) (f : α →ₘ[μ] β) : α →ₘ[μ] γ :=
Quotient.liftOn' f (fun f => mk (g ∘ (f : α → β)) (hg.comp_aestronglyMeasurable f.2))
fun _ _ H => mk_eq_mk.2 <| H.fun_comp g
#align measure_theory.ae_eq_fun.comp MeasureTheory.AEEqFun.comp
@[simp]
theorem comp_mk (g : β → γ) (hg : Continuous g) (f : α → β) (hf) :
comp g hg (mk f hf : α →ₘ[μ] β) = mk (g ∘ f) (hg.comp_aestronglyMeasurable hf) :=
rfl
#align measure_theory.ae_eq_fun.comp_mk MeasureTheory.AEEqFun.comp_mk
theorem comp_eq_mk (g : β → γ) (hg : Continuous g) (f : α →ₘ[μ] β) :
comp g hg f = mk (g ∘ f) (hg.comp_aestronglyMeasurable f.aestronglyMeasurable) := by
rw [← comp_mk g hg f f.aestronglyMeasurable, mk_coeFn]
#align measure_theory.ae_eq_fun.comp_eq_mk MeasureTheory.AEEqFun.comp_eq_mk
theorem coeFn_comp (g : β → γ) (hg : Continuous g) (f : α →ₘ[μ] β) : comp g hg f =ᵐ[μ] g ∘ f := by
rw [comp_eq_mk]
apply coeFn_mk
#align measure_theory.ae_eq_fun.coe_fn_comp MeasureTheory.AEEqFun.coeFn_comp
theorem comp_compQuasiMeasurePreserving [MeasurableSpace β] {ν} (g : γ → δ) (hg : Continuous g)
(f : β →ₘ[ν] γ) {φ : α → β} (hφ : Measure.QuasiMeasurePreserving φ μ ν) :
(comp g hg f).compQuasiMeasurePreserving φ hφ =
comp g hg (f.compQuasiMeasurePreserving φ hφ) := by
rcases f; rfl
section CompMeasurable
variable [MeasurableSpace β] [PseudoMetrizableSpace β] [BorelSpace β] [MeasurableSpace γ]
[PseudoMetrizableSpace γ] [OpensMeasurableSpace γ] [SecondCountableTopology γ]
/-- Given a measurable function `g : β → γ`, and an almost everywhere equal function `[f] : α →ₘ β`,
return the equivalence class of `g ∘ f`, i.e., the almost everywhere equal function
`[g ∘ f] : α →ₘ γ`. This requires that `γ` has a second countable topology. -/
def compMeasurable (g : β → γ) (hg : Measurable g) (f : α →ₘ[μ] β) : α →ₘ[μ] γ :=
Quotient.liftOn' f
(fun f' => mk (g ∘ (f' : α → β)) (hg.comp_aemeasurable f'.2.aemeasurable).aestronglyMeasurable)
fun _ _ H => mk_eq_mk.2 <| H.fun_comp g
#align measure_theory.ae_eq_fun.comp_measurable MeasureTheory.AEEqFun.compMeasurable
@[simp]
theorem compMeasurable_mk (g : β → γ) (hg : Measurable g) (f : α → β)
(hf : AEStronglyMeasurable f μ) :
compMeasurable g hg (mk f hf : α →ₘ[μ] β) =
mk (g ∘ f) (hg.comp_aemeasurable hf.aemeasurable).aestronglyMeasurable :=
rfl
#align measure_theory.ae_eq_fun.comp_measurable_mk MeasureTheory.AEEqFun.compMeasurable_mk
theorem compMeasurable_eq_mk (g : β → γ) (hg : Measurable g) (f : α →ₘ[μ] β) :
compMeasurable g hg f =
mk (g ∘ f) (hg.comp_aemeasurable f.aemeasurable).aestronglyMeasurable := by
rw [← compMeasurable_mk g hg f f.aestronglyMeasurable, mk_coeFn]
#align measure_theory.ae_eq_fun.comp_measurable_eq_mk MeasureTheory.AEEqFun.compMeasurable_eq_mk
theorem coeFn_compMeasurable (g : β → γ) (hg : Measurable g) (f : α →ₘ[μ] β) :
compMeasurable g hg f =ᵐ[μ] g ∘ f := by
rw [compMeasurable_eq_mk]
apply coeFn_mk
#align measure_theory.ae_eq_fun.coe_fn_comp_measurable MeasureTheory.AEEqFun.coeFn_compMeasurable
end CompMeasurable
/-- The class of `x ↦ (f x, g x)`. -/
def pair (f : α →ₘ[μ] β) (g : α →ₘ[μ] γ) : α →ₘ[μ] β × γ :=
Quotient.liftOn₂' f g (fun f g => mk (fun x => (f.1 x, g.1 x)) (f.2.prod_mk g.2))
fun _f _g _f' _g' Hf Hg => mk_eq_mk.2 <| Hf.prod_mk Hg
#align measure_theory.ae_eq_fun.pair MeasureTheory.AEEqFun.pair
@[simp]
theorem pair_mk_mk (f : α → β) (hf) (g : α → γ) (hg) :
(mk f hf : α →ₘ[μ] β).pair (mk g hg) = mk (fun x => (f x, g x)) (hf.prod_mk hg) :=
rfl
#align measure_theory.ae_eq_fun.pair_mk_mk MeasureTheory.AEEqFun.pair_mk_mk
theorem pair_eq_mk (f : α →ₘ[μ] β) (g : α →ₘ[μ] γ) :
f.pair g =
mk (fun x => (f x, g x)) (f.aestronglyMeasurable.prod_mk g.aestronglyMeasurable) := by
simp only [← pair_mk_mk, mk_coeFn, f.aestronglyMeasurable, g.aestronglyMeasurable]
#align measure_theory.ae_eq_fun.pair_eq_mk MeasureTheory.AEEqFun.pair_eq_mk
| Mathlib/MeasureTheory/Function/AEEqFun.lean | 352 | 354 | theorem coeFn_pair (f : α →ₘ[μ] β) (g : α →ₘ[μ] γ) : f.pair g =ᵐ[μ] fun x => (f x, g x) := by |
rw [pair_eq_mk]
apply coeFn_mk
|
/-
Copyright (c) 2021 Aaron Anderson. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Aaron Anderson
-/
import Mathlib.Algebra.Group.Support
import Mathlib.Order.WellFoundedSet
#align_import ring_theory.hahn_series from "leanprover-community/mathlib"@"a484a7d0eade4e1268f4fb402859b6686037f965"
/-!
# Hahn Series
If `Γ` is ordered and `R` has zero, then `HahnSeries Γ R` consists of formal series over `Γ` with
coefficients in `R`, whose supports are partially well-ordered. With further structure on `R` and
`Γ`, we can add further structure on `HahnSeries Γ R`, with the most studied case being when `Γ` is
a linearly ordered abelian group and `R` is a field, in which case `HahnSeries Γ R` is a
valued field, with value group `Γ`.
These generalize Laurent series (with value group `ℤ`), and Laurent series are implemented that way
in the file `RingTheory/LaurentSeries`.
## Main Definitions
* If `Γ` is ordered and `R` has zero, then `HahnSeries Γ R` consists of
formal series over `Γ` with coefficients in `R`, whose supports are partially well-ordered.
* `support x` is the subset of `Γ` whose coefficients are nonzero.
* `single a r` is the Hahn series which has coefficient `r` at `a` and zero otherwise.
* `orderTop x` is a minimal element of `WithTop Γ` where `x` has a nonzero
coefficient if `x ≠ 0`, and is `⊤` when `x = 0`.
* `order x` is a minimal element of `Γ` where `x` has a nonzero coefficient if `x ≠ 0`, and is zero
when `x = 0`.
## References
- [J. van der Hoeven, *Operators on Generalized Power Series*][van_der_hoeven]
-/
set_option linter.uppercaseLean3 false
open Finset Function
open scoped Classical
noncomputable section
/-- If `Γ` is linearly ordered and `R` has zero, then `HahnSeries Γ R` consists of
formal series over `Γ` with coefficients in `R`, whose supports are well-founded. -/
@[ext]
structure HahnSeries (Γ : Type*) (R : Type*) [PartialOrder Γ] [Zero R] where
/-- The coefficient function of a Hahn Series. -/
coeff : Γ → R
isPWO_support' : (Function.support coeff).IsPWO
#align hahn_series HahnSeries
variable {Γ : Type*} {R : Type*}
namespace HahnSeries
section Zero
variable [PartialOrder Γ] [Zero R]
theorem coeff_injective : Injective (coeff : HahnSeries Γ R → Γ → R) :=
HahnSeries.ext
#align hahn_series.coeff_injective HahnSeries.coeff_injective
@[simp]
theorem coeff_inj {x y : HahnSeries Γ R} : x.coeff = y.coeff ↔ x = y :=
coeff_injective.eq_iff
#align hahn_series.coeff_inj HahnSeries.coeff_inj
/-- The support of a Hahn series is just the set of indices whose coefficients are nonzero.
Notably, it is well-founded. -/
nonrec def support (x : HahnSeries Γ R) : Set Γ :=
support x.coeff
#align hahn_series.support HahnSeries.support
@[simp]
theorem isPWO_support (x : HahnSeries Γ R) : x.support.IsPWO :=
x.isPWO_support'
#align hahn_series.is_pwo_support HahnSeries.isPWO_support
@[simp]
theorem isWF_support (x : HahnSeries Γ R) : x.support.IsWF :=
x.isPWO_support.isWF
#align hahn_series.is_wf_support HahnSeries.isWF_support
@[simp]
theorem mem_support (x : HahnSeries Γ R) (a : Γ) : a ∈ x.support ↔ x.coeff a ≠ 0 :=
Iff.refl _
#align hahn_series.mem_support HahnSeries.mem_support
instance : Zero (HahnSeries Γ R) :=
⟨{ coeff := 0
isPWO_support' := by simp }⟩
instance : Inhabited (HahnSeries Γ R) :=
⟨0⟩
instance [Subsingleton R] : Subsingleton (HahnSeries Γ R) :=
⟨fun a b => a.ext b (Subsingleton.elim _ _)⟩
@[simp]
theorem zero_coeff {a : Γ} : (0 : HahnSeries Γ R).coeff a = 0 :=
rfl
#align hahn_series.zero_coeff HahnSeries.zero_coeff
@[simp]
theorem coeff_fun_eq_zero_iff {x : HahnSeries Γ R} : x.coeff = 0 ↔ x = 0 :=
coeff_injective.eq_iff' rfl
#align hahn_series.coeff_fun_eq_zero_iff HahnSeries.coeff_fun_eq_zero_iff
theorem ne_zero_of_coeff_ne_zero {x : HahnSeries Γ R} {g : Γ} (h : x.coeff g ≠ 0) : x ≠ 0 :=
mt (fun x0 => (x0.symm ▸ zero_coeff : x.coeff g = 0)) h
#align hahn_series.ne_zero_of_coeff_ne_zero HahnSeries.ne_zero_of_coeff_ne_zero
@[simp]
theorem support_zero : support (0 : HahnSeries Γ R) = ∅ :=
Function.support_zero
#align hahn_series.support_zero HahnSeries.support_zero
@[simp]
nonrec theorem support_nonempty_iff {x : HahnSeries Γ R} : x.support.Nonempty ↔ x ≠ 0 := by
rw [support, support_nonempty_iff, Ne, coeff_fun_eq_zero_iff]
#align hahn_series.support_nonempty_iff HahnSeries.support_nonempty_iff
@[simp]
theorem support_eq_empty_iff {x : HahnSeries Γ R} : x.support = ∅ ↔ x = 0 :=
support_eq_empty_iff.trans coeff_fun_eq_zero_iff
#align hahn_series.support_eq_empty_iff HahnSeries.support_eq_empty_iff
/-- Change a HahnSeries with coefficients in HahnSeries to a HahnSeries on the Lex product. -/
def ofIterate {Γ' : Type*} [PartialOrder Γ'] (x : HahnSeries Γ (HahnSeries Γ' R)) :
HahnSeries (Γ ×ₗ Γ') R where
coeff := fun g => coeff (coeff x g.1) g.2
isPWO_support' := by
refine Set.PartiallyWellOrderedOn.subsetProdLex ?_ ?_
· refine Set.IsPWO.mono x.isPWO_support' ?_
simp_rw [Set.image_subset_iff, support_subset_iff, Set.mem_preimage, Function.mem_support]
exact fun _ ↦ ne_zero_of_coeff_ne_zero
· exact fun a => by simpa [Function.mem_support, ne_eq] using (x.coeff a).isPWO_support'
@[simp]
lemma mk_eq_zero (f : Γ → R) (h) : HahnSeries.mk f h = 0 ↔ f = 0 := by
rw [HahnSeries.ext_iff]
rfl
/-- Change a Hahn series on a lex product to a Hahn series with coefficients in a Hahn series. -/
def toIterate {Γ' : Type*} [PartialOrder Γ'] (x : HahnSeries (Γ ×ₗ Γ') R) :
HahnSeries Γ (HahnSeries Γ' R) where
coeff := fun g => {
coeff := fun g' => coeff x (g, g')
isPWO_support' := Set.PartiallyWellOrderedOn.fiberProdLex x.isPWO_support' g
}
isPWO_support' := by
have h₁ : (Function.support fun g => HahnSeries.mk (fun g' => x.coeff (g, g'))
(Set.PartiallyWellOrderedOn.fiberProdLex x.isPWO_support' g)) = Function.support
fun g => fun g' => x.coeff (g, g') := by
simp only [Function.support, ne_eq, mk_eq_zero]
rw [h₁, Function.support_curry' x.coeff]
exact Set.PartiallyWellOrderedOn.imageProdLex x.isPWO_support'
/-- The equivalence between iterated Hahn series and Hahn series on the lex product. -/
@[simps]
def iterateEquiv {Γ' : Type*} [PartialOrder Γ'] :
HahnSeries Γ (HahnSeries Γ' R) ≃ HahnSeries (Γ ×ₗ Γ') R where
toFun := ofIterate
invFun := toIterate
left_inv := congrFun rfl
right_inv := congrFun rfl
/-- `single a r` is the Hahn series which has coefficient `r` at `a` and zero otherwise. -/
def single (a : Γ) : ZeroHom R (HahnSeries Γ R) where
toFun r :=
{ coeff := Pi.single a r
isPWO_support' := (Set.isPWO_singleton a).mono Pi.support_single_subset }
map_zero' := HahnSeries.ext _ _ (Pi.single_zero _)
#align hahn_series.single HahnSeries.single
variable {a b : Γ} {r : R}
@[simp]
theorem single_coeff_same (a : Γ) (r : R) : (single a r).coeff a = r :=
Pi.single_eq_same (f := fun _ => R) a r
#align hahn_series.single_coeff_same HahnSeries.single_coeff_same
@[simp]
theorem single_coeff_of_ne (h : b ≠ a) : (single a r).coeff b = 0 :=
Pi.single_eq_of_ne (f := fun _ => R) h r
#align hahn_series.single_coeff_of_ne HahnSeries.single_coeff_of_ne
theorem single_coeff : (single a r).coeff b = if b = a then r else 0 := by
split_ifs with h <;> simp [h]
#align hahn_series.single_coeff HahnSeries.single_coeff
@[simp]
theorem support_single_of_ne (h : r ≠ 0) : support (single a r) = {a} :=
Pi.support_single_of_ne h
#align hahn_series.support_single_of_ne HahnSeries.support_single_of_ne
theorem support_single_subset : support (single a r) ⊆ {a} :=
Pi.support_single_subset
#align hahn_series.support_single_subset HahnSeries.support_single_subset
theorem eq_of_mem_support_single {b : Γ} (h : b ∈ support (single a r)) : b = a :=
support_single_subset h
#align hahn_series.eq_of_mem_support_single HahnSeries.eq_of_mem_support_single
--@[simp] Porting note (#10618): simp can prove it
theorem single_eq_zero : single a (0 : R) = 0 :=
(single a).map_zero
#align hahn_series.single_eq_zero HahnSeries.single_eq_zero
theorem single_injective (a : Γ) : Function.Injective (single a : R → HahnSeries Γ R) :=
fun r s rs => by rw [← single_coeff_same a r, ← single_coeff_same a s, rs]
#align hahn_series.single_injective HahnSeries.single_injective
theorem single_ne_zero (h : r ≠ 0) : single a r ≠ 0 := fun con =>
h (single_injective a (con.trans single_eq_zero.symm))
#align hahn_series.single_ne_zero HahnSeries.single_ne_zero
@[simp]
theorem single_eq_zero_iff {a : Γ} {r : R} : single a r = 0 ↔ r = 0 :=
map_eq_zero_iff _ <| single_injective a
#align hahn_series.single_eq_zero_iff HahnSeries.single_eq_zero_iff
instance [Nonempty Γ] [Nontrivial R] : Nontrivial (HahnSeries Γ R) :=
⟨by
obtain ⟨r, s, rs⟩ := exists_pair_ne R
inhabit Γ
refine ⟨single default r, single default s, fun con => rs ?_⟩
rw [← single_coeff_same (default : Γ) r, con, single_coeff_same]⟩
section Order
/-- The orderTop of a Hahn series `x` is a minimal element of `WithTop Γ` where `x` has a nonzero
coefficient if `x ≠ 0`, and is `⊤` when `x = 0`. -/
def orderTop (x : HahnSeries Γ R) : WithTop Γ :=
if h : x = 0 then ⊤ else x.isWF_support.min (support_nonempty_iff.2 h)
@[simp]
theorem orderTop_zero : orderTop (0 : HahnSeries Γ R) = ⊤ :=
dif_pos rfl
theorem orderTop_of_ne {x : HahnSeries Γ R} (hx : x ≠ 0) :
orderTop x = x.isWF_support.min (support_nonempty_iff.2 hx) :=
dif_neg hx
@[simp]
theorem ne_zero_iff_orderTop {x : HahnSeries Γ R} : x ≠ 0 ↔ orderTop x ≠ ⊤ := by
constructor
· exact fun hx => Eq.mpr (congrArg (fun h ↦ h ≠ ⊤) (orderTop_of_ne hx)) WithTop.coe_ne_top
· contrapose!
simp_all only [orderTop_zero, implies_true]
theorem orderTop_eq_top_iff {x : HahnSeries Γ R} : orderTop x = ⊤ ↔ x = 0 := by
constructor
· contrapose!
exact ne_zero_iff_orderTop.mp
· simp_all only [orderTop_zero, implies_true]
theorem untop_orderTop_of_ne_zero {x : HahnSeries Γ R} (hx : x ≠ 0) :
WithTop.untop x.orderTop (ne_zero_iff_orderTop.mp hx) =
x.isWF_support.min (support_nonempty_iff.2 hx) :=
WithTop.coe_inj.mp ((WithTop.coe_untop (orderTop x) (ne_zero_iff_orderTop.mp hx)).trans
(orderTop_of_ne hx))
theorem coeff_orderTop_ne {x : HahnSeries Γ R} {g : Γ} (hg : x.orderTop = g) :
x.coeff g ≠ 0 := by
have h : orderTop x ≠ ⊤ := by simp_all only [ne_eq, WithTop.coe_ne_top, not_false_eq_true]
have hx : x ≠ 0 := ne_zero_iff_orderTop.mpr h
rw [orderTop_of_ne hx, WithTop.coe_eq_coe] at hg
rw [← hg]
exact x.isWF_support.min_mem (support_nonempty_iff.2 hx)
theorem orderTop_le_of_coeff_ne_zero {Γ} [LinearOrder Γ] {x : HahnSeries Γ R}
{g : Γ} (h : x.coeff g ≠ 0) : x.orderTop ≤ g := by
rw [orderTop_of_ne (ne_zero_of_coeff_ne_zero h), WithTop.coe_le_coe]
exact Set.IsWF.min_le _ _ ((mem_support _ _).2 h)
@[simp]
theorem orderTop_single (h : r ≠ 0) : (single a r).orderTop = a :=
(orderTop_of_ne (single_ne_zero h)).trans
(WithTop.coe_inj.mpr (support_single_subset
((single a r).isWF_support.min_mem (support_nonempty_iff.2 (single_ne_zero h)))))
theorem coeff_eq_zero_of_lt_orderTop {x : HahnSeries Γ R} {i : Γ} (hi : i < x.orderTop) :
x.coeff i = 0 := by
rcases eq_or_ne x 0 with (rfl | hx)
· exact zero_coeff
contrapose! hi
rw [← mem_support] at hi
rw [orderTop_of_ne hx, WithTop.coe_lt_coe]
exact Set.IsWF.not_lt_min _ _ hi
variable [Zero Γ]
/-- The order of a nonzero Hahn series `x` is a minimal element of `Γ` where `x` has a
nonzero coefficient, the order of 0 is 0. -/
def order (x : HahnSeries Γ R) : Γ :=
if h : x = 0 then 0 else x.isWF_support.min (support_nonempty_iff.2 h)
#align hahn_series.order HahnSeries.order
@[simp]
theorem order_zero : order (0 : HahnSeries Γ R) = 0 :=
dif_pos rfl
#align hahn_series.order_zero HahnSeries.order_zero
theorem order_of_ne {x : HahnSeries Γ R} (hx : x ≠ 0) :
order x = x.isWF_support.min (support_nonempty_iff.2 hx) :=
dif_neg hx
#align hahn_series.order_of_ne HahnSeries.order_of_ne
theorem order_eq_orderTop_of_ne {x : HahnSeries Γ R} (hx : x ≠ 0) : order x = orderTop x := by
rw [order_of_ne hx, orderTop_of_ne hx]
theorem coeff_order_ne_zero {x : HahnSeries Γ R} (hx : x ≠ 0) : x.coeff x.order ≠ 0 := by
rw [order_of_ne hx]
exact x.isWF_support.min_mem (support_nonempty_iff.2 hx)
#align hahn_series.coeff_order_ne_zero HahnSeries.coeff_order_ne_zero
theorem order_le_of_coeff_ne_zero {Γ} [LinearOrderedCancelAddCommMonoid Γ] {x : HahnSeries Γ R}
{g : Γ} (h : x.coeff g ≠ 0) : x.order ≤ g :=
le_trans (le_of_eq (order_of_ne (ne_zero_of_coeff_ne_zero h)))
(Set.IsWF.min_le _ _ ((mem_support _ _).2 h))
#align hahn_series.order_le_of_coeff_ne_zero HahnSeries.order_le_of_coeff_ne_zero
@[simp]
theorem order_single (h : r ≠ 0) : (single a r).order = a :=
(order_of_ne (single_ne_zero h)).trans
(support_single_subset
((single a r).isWF_support.min_mem (support_nonempty_iff.2 (single_ne_zero h))))
#align hahn_series.order_single HahnSeries.order_single
theorem coeff_eq_zero_of_lt_order {x : HahnSeries Γ R} {i : Γ} (hi : i < x.order) :
x.coeff i = 0 := by
rcases eq_or_ne x 0 with (rfl | hx)
· simp
contrapose! hi
rw [← mem_support] at hi
rw [order_of_ne hx]
exact Set.IsWF.not_lt_min _ _ hi
#align hahn_series.coeff_eq_zero_of_lt_order HahnSeries.coeff_eq_zero_of_lt_order
end Order
section Domain
variable {Γ' : Type*} [PartialOrder Γ']
/-- Extends the domain of a `HahnSeries` by an `OrderEmbedding`. -/
def embDomain (f : Γ ↪o Γ') : HahnSeries Γ R → HahnSeries Γ' R := fun x =>
{ coeff := fun b : Γ' => if h : b ∈ f '' x.support then x.coeff (Classical.choose h) else 0
isPWO_support' :=
(x.isPWO_support.image_of_monotone f.monotone).mono fun b hb => by
contrapose! hb
rw [Function.mem_support, dif_neg hb, Classical.not_not] }
#align hahn_series.emb_domain HahnSeries.embDomain
@[simp]
theorem embDomain_coeff {f : Γ ↪o Γ'} {x : HahnSeries Γ R} {a : Γ} :
(embDomain f x).coeff (f a) = x.coeff a := by
rw [embDomain]
dsimp only
by_cases ha : a ∈ x.support
· rw [dif_pos (Set.mem_image_of_mem f ha)]
exact congr rfl (f.injective (Classical.choose_spec (Set.mem_image_of_mem f ha)).2)
· rw [dif_neg, Classical.not_not.1 fun c => ha ((mem_support _ _).2 c)]
contrapose! ha
obtain ⟨b, hb1, hb2⟩ := (Set.mem_image _ _ _).1 ha
rwa [f.injective hb2] at hb1
#align hahn_series.emb_domain_coeff HahnSeries.embDomain_coeff
@[simp]
theorem embDomain_mk_coeff {f : Γ → Γ'} (hfi : Function.Injective f)
(hf : ∀ g g' : Γ, f g ≤ f g' ↔ g ≤ g') {x : HahnSeries Γ R} {a : Γ} :
(embDomain ⟨⟨f, hfi⟩, hf _ _⟩ x).coeff (f a) = x.coeff a :=
embDomain_coeff
#align hahn_series.emb_domain_mk_coeff HahnSeries.embDomain_mk_coeff
theorem embDomain_notin_image_support {f : Γ ↪o Γ'} {x : HahnSeries Γ R} {b : Γ'}
(hb : b ∉ f '' x.support) : (embDomain f x).coeff b = 0 :=
dif_neg hb
#align hahn_series.emb_domain_notin_image_support HahnSeries.embDomain_notin_image_support
theorem support_embDomain_subset {f : Γ ↪o Γ'} {x : HahnSeries Γ R} :
support (embDomain f x) ⊆ f '' x.support := by
intro g hg
contrapose! hg
rw [mem_support, embDomain_notin_image_support hg, Classical.not_not]
#align hahn_series.support_emb_domain_subset HahnSeries.support_embDomain_subset
theorem embDomain_notin_range {f : Γ ↪o Γ'} {x : HahnSeries Γ R} {b : Γ'} (hb : b ∉ Set.range f) :
(embDomain f x).coeff b = 0 :=
embDomain_notin_image_support fun con => hb (Set.image_subset_range _ _ con)
#align hahn_series.emb_domain_notin_range HahnSeries.embDomain_notin_range
@[simp]
theorem embDomain_zero {f : Γ ↪o Γ'} : embDomain f (0 : HahnSeries Γ R) = 0 := by
ext
simp [embDomain_notin_image_support]
#align hahn_series.emb_domain_zero HahnSeries.embDomain_zero
@[simp]
theorem embDomain_single {f : Γ ↪o Γ'} {g : Γ} {r : R} :
embDomain f (single g r) = single (f g) r := by
ext g'
by_cases h : g' = f g
· simp [h]
rw [embDomain_notin_image_support, single_coeff_of_ne h]
by_cases hr : r = 0
· simp [hr]
rwa [support_single_of_ne hr, Set.image_singleton, Set.mem_singleton_iff]
#align hahn_series.emb_domain_single HahnSeries.embDomain_single
theorem embDomain_injective {f : Γ ↪o Γ'} :
Function.Injective (embDomain f : HahnSeries Γ R → HahnSeries Γ' R) := fun x y xy => by
ext g
rw [HahnSeries.ext_iff, Function.funext_iff] at xy
have xyg := xy (f g)
rwa [embDomain_coeff, embDomain_coeff] at xyg
#align hahn_series.emb_domain_injective HahnSeries.embDomain_injective
end Domain
end Zero
section LocallyFiniteLinearOrder
variable [Zero R] [LinearOrder Γ] [LocallyFiniteOrder Γ]
theorem suppBddBelow_supp_PWO (f : Γ → R) (hf : BddBelow (Function.support f)) :
(Function.support f).IsPWO := Set.isWF_iff_isPWO.mp hf.wellFoundedOn_lt
| Mathlib/RingTheory/HahnSeries/Basic.lean | 431 | 437 | theorem forallLTEqZero_supp_BddBelow (f : Γ → R) (n : Γ) (hn : ∀(m : Γ), m < n → f m = 0) :
BddBelow (Function.support f) := by |
simp only [BddBelow, Set.Nonempty, lowerBounds]
use n
intro m hm
rw [Function.mem_support, ne_eq] at hm
exact not_lt.mp (mt (hn m) hm)
|
/-
Copyright (c) 2020 Joseph Myers. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Joseph Myers, Manuel Candales
-/
import Mathlib.Analysis.InnerProductSpace.Basic
import Mathlib.Analysis.SpecialFunctions.Trigonometric.Inverse
#align_import geometry.euclidean.angle.unoriented.basic from "leanprover-community/mathlib"@"46b633fd842bef9469441c0209906f6dddd2b4f5"
/-!
# Angles between vectors
This file defines unoriented angles in real inner product spaces.
## Main definitions
* `InnerProductGeometry.angle` is the undirected angle between two vectors.
## TODO
Prove the triangle inequality for the angle.
-/
assert_not_exists HasFDerivAt
assert_not_exists ConformalAt
noncomputable section
open Real Set
open Real
open RealInnerProductSpace
namespace InnerProductGeometry
variable {V : Type*} [NormedAddCommGroup V] [InnerProductSpace ℝ V] {x y : V}
/-- The undirected angle between two vectors. If either vector is 0,
this is π/2. See `Orientation.oangle` for the corresponding oriented angle
definition. -/
def angle (x y : V) : ℝ :=
Real.arccos (⟪x, y⟫ / (‖x‖ * ‖y‖))
#align inner_product_geometry.angle InnerProductGeometry.angle
theorem continuousAt_angle {x : V × V} (hx1 : x.1 ≠ 0) (hx2 : x.2 ≠ 0) :
ContinuousAt (fun y : V × V => angle y.1 y.2) x :=
Real.continuous_arccos.continuousAt.comp <|
continuous_inner.continuousAt.div
((continuous_norm.comp continuous_fst).mul (continuous_norm.comp continuous_snd)).continuousAt
(by simp [hx1, hx2])
#align inner_product_geometry.continuous_at_angle InnerProductGeometry.continuousAt_angle
theorem angle_smul_smul {c : ℝ} (hc : c ≠ 0) (x y : V) : angle (c • x) (c • y) = angle x y := by
have : c * c ≠ 0 := mul_ne_zero hc hc
rw [angle, angle, real_inner_smul_left, inner_smul_right, norm_smul, norm_smul, Real.norm_eq_abs,
mul_mul_mul_comm _ ‖x‖, abs_mul_abs_self, ← mul_assoc c c, mul_div_mul_left _ _ this]
#align inner_product_geometry.angle_smul_smul InnerProductGeometry.angle_smul_smul
@[simp]
theorem _root_.LinearIsometry.angle_map {E F : Type*} [NormedAddCommGroup E] [NormedAddCommGroup F]
[InnerProductSpace ℝ E] [InnerProductSpace ℝ F] (f : E →ₗᵢ[ℝ] F) (u v : E) :
angle (f u) (f v) = angle u v := by
rw [angle, angle, f.inner_map_map, f.norm_map, f.norm_map]
#align linear_isometry.angle_map LinearIsometry.angle_map
@[simp, norm_cast]
theorem _root_.Submodule.angle_coe {s : Submodule ℝ V} (x y : s) :
angle (x : V) (y : V) = angle x y :=
s.subtypeₗᵢ.angle_map x y
#align submodule.angle_coe Submodule.angle_coe
/-- The cosine of the angle between two vectors. -/
theorem cos_angle (x y : V) : Real.cos (angle x y) = ⟪x, y⟫ / (‖x‖ * ‖y‖) :=
Real.cos_arccos (abs_le.mp (abs_real_inner_div_norm_mul_norm_le_one x y)).1
(abs_le.mp (abs_real_inner_div_norm_mul_norm_le_one x y)).2
#align inner_product_geometry.cos_angle InnerProductGeometry.cos_angle
/-- The angle between two vectors does not depend on their order. -/
theorem angle_comm (x y : V) : angle x y = angle y x := by
unfold angle
rw [real_inner_comm, mul_comm]
#align inner_product_geometry.angle_comm InnerProductGeometry.angle_comm
/-- The angle between the negation of two vectors. -/
@[simp]
theorem angle_neg_neg (x y : V) : angle (-x) (-y) = angle x y := by
unfold angle
rw [inner_neg_neg, norm_neg, norm_neg]
#align inner_product_geometry.angle_neg_neg InnerProductGeometry.angle_neg_neg
/-- The angle between two vectors is nonnegative. -/
theorem angle_nonneg (x y : V) : 0 ≤ angle x y :=
Real.arccos_nonneg _
#align inner_product_geometry.angle_nonneg InnerProductGeometry.angle_nonneg
/-- The angle between two vectors is at most π. -/
theorem angle_le_pi (x y : V) : angle x y ≤ π :=
Real.arccos_le_pi _
#align inner_product_geometry.angle_le_pi InnerProductGeometry.angle_le_pi
/-- The angle between a vector and the negation of another vector. -/
theorem angle_neg_right (x y : V) : angle x (-y) = π - angle x y := by
unfold angle
rw [← Real.arccos_neg, norm_neg, inner_neg_right, neg_div]
#align inner_product_geometry.angle_neg_right InnerProductGeometry.angle_neg_right
/-- The angle between the negation of a vector and another vector. -/
theorem angle_neg_left (x y : V) : angle (-x) y = π - angle x y := by
rw [← angle_neg_neg, neg_neg, angle_neg_right]
#align inner_product_geometry.angle_neg_left InnerProductGeometry.angle_neg_left
proof_wanted angle_triangle (x y z : V) : angle x z ≤ angle x y + angle y z
/-- The angle between the zero vector and a vector. -/
@[simp]
theorem angle_zero_left (x : V) : angle 0 x = π / 2 := by
unfold angle
rw [inner_zero_left, zero_div, Real.arccos_zero]
#align inner_product_geometry.angle_zero_left InnerProductGeometry.angle_zero_left
/-- The angle between a vector and the zero vector. -/
@[simp]
theorem angle_zero_right (x : V) : angle x 0 = π / 2 := by
unfold angle
rw [inner_zero_right, zero_div, Real.arccos_zero]
#align inner_product_geometry.angle_zero_right InnerProductGeometry.angle_zero_right
/-- The angle between a nonzero vector and itself. -/
@[simp]
theorem angle_self {x : V} (hx : x ≠ 0) : angle x x = 0 := by
unfold angle
rw [← real_inner_self_eq_norm_mul_norm, div_self (inner_self_ne_zero.2 hx : ⟪x, x⟫ ≠ 0),
Real.arccos_one]
#align inner_product_geometry.angle_self InnerProductGeometry.angle_self
/-- The angle between a nonzero vector and its negation. -/
@[simp]
theorem angle_self_neg_of_nonzero {x : V} (hx : x ≠ 0) : angle x (-x) = π := by
rw [angle_neg_right, angle_self hx, sub_zero]
#align inner_product_geometry.angle_self_neg_of_nonzero InnerProductGeometry.angle_self_neg_of_nonzero
/-- The angle between the negation of a nonzero vector and that
vector. -/
@[simp]
theorem angle_neg_self_of_nonzero {x : V} (hx : x ≠ 0) : angle (-x) x = π := by
rw [angle_comm, angle_self_neg_of_nonzero hx]
#align inner_product_geometry.angle_neg_self_of_nonzero InnerProductGeometry.angle_neg_self_of_nonzero
/-- The angle between a vector and a positive multiple of a vector. -/
@[simp]
theorem angle_smul_right_of_pos (x y : V) {r : ℝ} (hr : 0 < r) : angle x (r • y) = angle x y := by
unfold angle
rw [inner_smul_right, norm_smul, Real.norm_eq_abs, abs_of_nonneg (le_of_lt hr), ← mul_assoc,
mul_comm _ r, mul_assoc, mul_div_mul_left _ _ (ne_of_gt hr)]
#align inner_product_geometry.angle_smul_right_of_pos InnerProductGeometry.angle_smul_right_of_pos
/-- The angle between a positive multiple of a vector and a vector. -/
@[simp]
theorem angle_smul_left_of_pos (x y : V) {r : ℝ} (hr : 0 < r) : angle (r • x) y = angle x y := by
rw [angle_comm, angle_smul_right_of_pos y x hr, angle_comm]
#align inner_product_geometry.angle_smul_left_of_pos InnerProductGeometry.angle_smul_left_of_pos
/-- The angle between a vector and a negative multiple of a vector. -/
@[simp]
theorem angle_smul_right_of_neg (x y : V) {r : ℝ} (hr : r < 0) :
angle x (r • y) = angle x (-y) := by
rw [← neg_neg r, neg_smul, angle_neg_right, angle_smul_right_of_pos x y (neg_pos_of_neg hr),
angle_neg_right]
#align inner_product_geometry.angle_smul_right_of_neg InnerProductGeometry.angle_smul_right_of_neg
/-- The angle between a negative multiple of a vector and a vector. -/
@[simp]
theorem angle_smul_left_of_neg (x y : V) {r : ℝ} (hr : r < 0) : angle (r • x) y = angle (-x) y := by
rw [angle_comm, angle_smul_right_of_neg y x hr, angle_comm]
#align inner_product_geometry.angle_smul_left_of_neg InnerProductGeometry.angle_smul_left_of_neg
/-- The cosine of the angle between two vectors, multiplied by the
product of their norms. -/
theorem cos_angle_mul_norm_mul_norm (x y : V) : Real.cos (angle x y) * (‖x‖ * ‖y‖) = ⟪x, y⟫ := by
rw [cos_angle, div_mul_cancel_of_imp]
simp (config := { contextual := true }) [or_imp]
#align inner_product_geometry.cos_angle_mul_norm_mul_norm InnerProductGeometry.cos_angle_mul_norm_mul_norm
/-- The sine of the angle between two vectors, multiplied by the
product of their norms. -/
theorem sin_angle_mul_norm_mul_norm (x y : V) :
Real.sin (angle x y) * (‖x‖ * ‖y‖) = √(⟪x, x⟫ * ⟪y, y⟫ - ⟪x, y⟫ * ⟪x, y⟫) := by
unfold angle
rw [Real.sin_arccos, ← Real.sqrt_mul_self (mul_nonneg (norm_nonneg x) (norm_nonneg y)),
← Real.sqrt_mul' _ (mul_self_nonneg _), sq,
Real.sqrt_mul_self (mul_nonneg (norm_nonneg x) (norm_nonneg y)),
real_inner_self_eq_norm_mul_norm, real_inner_self_eq_norm_mul_norm]
by_cases h : ‖x‖ * ‖y‖ = 0
· rw [show ‖x‖ * ‖x‖ * (‖y‖ * ‖y‖) = ‖x‖ * ‖y‖ * (‖x‖ * ‖y‖) by ring, h, mul_zero,
mul_zero, zero_sub]
cases' eq_zero_or_eq_zero_of_mul_eq_zero h with hx hy
· rw [norm_eq_zero] at hx
rw [hx, inner_zero_left, zero_mul, neg_zero]
· rw [norm_eq_zero] at hy
rw [hy, inner_zero_right, zero_mul, neg_zero]
· field_simp [h]
ring_nf
#align inner_product_geometry.sin_angle_mul_norm_mul_norm InnerProductGeometry.sin_angle_mul_norm_mul_norm
/-- The angle between two vectors is zero if and only if they are
nonzero and one is a positive multiple of the other. -/
theorem angle_eq_zero_iff {x y : V} : angle x y = 0 ↔ x ≠ 0 ∧ ∃ r : ℝ, 0 < r ∧ y = r • x := by
rw [angle, ← real_inner_div_norm_mul_norm_eq_one_iff, Real.arccos_eq_zero, LE.le.le_iff_eq,
eq_comm]
exact (abs_le.mp (abs_real_inner_div_norm_mul_norm_le_one x y)).2
#align inner_product_geometry.angle_eq_zero_iff InnerProductGeometry.angle_eq_zero_iff
/-- The angle between two vectors is π if and only if they are nonzero
and one is a negative multiple of the other. -/
theorem angle_eq_pi_iff {x y : V} : angle x y = π ↔ x ≠ 0 ∧ ∃ r : ℝ, r < 0 ∧ y = r • x := by
rw [angle, ← real_inner_div_norm_mul_norm_eq_neg_one_iff, Real.arccos_eq_pi, LE.le.le_iff_eq]
exact (abs_le.mp (abs_real_inner_div_norm_mul_norm_le_one x y)).1
#align inner_product_geometry.angle_eq_pi_iff InnerProductGeometry.angle_eq_pi_iff
/-- If the angle between two vectors is π, the angles between those
vectors and a third vector add to π. -/
theorem angle_add_angle_eq_pi_of_angle_eq_pi {x y : V} (z : V) (h : angle x y = π) :
angle x z + angle y z = π := by
rcases angle_eq_pi_iff.1 h with ⟨_, ⟨r, ⟨hr, rfl⟩⟩⟩
rw [angle_smul_left_of_neg x z hr, angle_neg_left, add_sub_cancel]
#align inner_product_geometry.angle_add_angle_eq_pi_of_angle_eq_pi InnerProductGeometry.angle_add_angle_eq_pi_of_angle_eq_pi
/-- Two vectors have inner product 0 if and only if the angle between
them is π/2. -/
theorem inner_eq_zero_iff_angle_eq_pi_div_two (x y : V) : ⟪x, y⟫ = 0 ↔ angle x y = π / 2 :=
Iff.symm <| by simp (config := { contextual := true }) [angle, or_imp]
#align inner_product_geometry.inner_eq_zero_iff_angle_eq_pi_div_two InnerProductGeometry.inner_eq_zero_iff_angle_eq_pi_div_two
/-- If the angle between two vectors is π, the inner product equals the negative product
of the norms. -/
theorem inner_eq_neg_mul_norm_of_angle_eq_pi {x y : V} (h : angle x y = π) :
⟪x, y⟫ = -(‖x‖ * ‖y‖) := by
simp [← cos_angle_mul_norm_mul_norm, h]
#align inner_product_geometry.inner_eq_neg_mul_norm_of_angle_eq_pi InnerProductGeometry.inner_eq_neg_mul_norm_of_angle_eq_pi
/-- If the angle between two vectors is 0, the inner product equals the product of the norms. -/
| Mathlib/Geometry/Euclidean/Angle/Unoriented/Basic.lean | 246 | 247 | theorem inner_eq_mul_norm_of_angle_eq_zero {x y : V} (h : angle x y = 0) : ⟪x, y⟫ = ‖x‖ * ‖y‖ := by |
simp [← cos_angle_mul_norm_mul_norm, h]
|
/-
Copyright (c) 2020 Johan Commelin. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johan Commelin, Robert Y. Lewis
-/
import Mathlib.Algebra.CharP.Invertible
import Mathlib.Algebra.MvPolynomial.Variables
import Mathlib.Algebra.MvPolynomial.CommRing
import Mathlib.Algebra.MvPolynomial.Expand
import Mathlib.Data.Fintype.BigOperators
import Mathlib.Data.ZMod.Basic
#align_import ring_theory.witt_vector.witt_polynomial from "leanprover-community/mathlib"@"c3019c79074b0619edb4b27553a91b2e82242395"
/-!
# Witt polynomials
To endow `WittVector p R` with a ring structure,
we need to study the so-called Witt polynomials.
Fix a base value `p : ℕ`.
The `p`-adic Witt polynomials are an infinite family of polynomials
indexed by a natural number `n`, taking values in an arbitrary ring `R`.
The variables of these polynomials are represented by natural numbers.
The variable set of the `n`th Witt polynomial contains at most `n+1` elements `{0, ..., n}`,
with exactly these variables when `R` has characteristic `0`.
These polynomials are used to define the addition and multiplication operators
on the type of Witt vectors. (While this type itself is not complicated,
the ring operations are what make it interesting.)
When the base `p` is invertible in `R`, the `p`-adic Witt polynomials
form a basis for `MvPolynomial ℕ R`, equivalent to the standard basis.
## Main declarations
* `WittPolynomial p R n`: the `n`-th Witt polynomial, viewed as polynomial over the ring `R`
* `xInTermsOfW p R n`: if `p` is invertible, the polynomial `X n` is contained in the subalgebra
generated by the Witt polynomials. `xInTermsOfW p R n` is the explicit polynomial,
which upon being bound to the Witt polynomials yields `X n`.
* `bind₁_wittPolynomial_xInTermsOfW`: the proof of the claim that
`bind₁ (xInTermsOfW p R) (W_ R n) = X n`
* `bind₁_xInTermsOfW_wittPolynomial`: the converse of the above statement
## Notation
In this file we use the following notation
* `p` is a natural number, typically assumed to be prime.
* `R` and `S` are commutative rings
* `W n` (and `W_ R n` when the ring needs to be explicit) denotes the `n`th Witt polynomial
## References
* [Hazewinkel, *Witt Vectors*][Haze09]
* [Commelin and Lewis, *Formalizing the Ring of Witt Vectors*][CL21]
-/
open MvPolynomial
open Finset hiding map
open Finsupp (single)
--attribute [-simp] coe_eval₂_hom
variable (p : ℕ)
variable (R : Type*) [CommRing R] [DecidableEq R]
/-- `wittPolynomial p R n` is the `n`-th Witt polynomial
with respect to a prime `p` with coefficients in a commutative ring `R`.
It is defined as:
`∑_{i ≤ n} p^i X_i^{p^{n-i}} ∈ R[X_0, X_1, X_2, …]`. -/
noncomputable def wittPolynomial (n : ℕ) : MvPolynomial ℕ R :=
∑ i ∈ range (n + 1), monomial (single i (p ^ (n - i))) ((p : R) ^ i)
#align witt_polynomial wittPolynomial
theorem wittPolynomial_eq_sum_C_mul_X_pow (n : ℕ) :
wittPolynomial p R n = ∑ i ∈ range (n + 1), C ((p : R) ^ i) * X i ^ p ^ (n - i) := by
apply sum_congr rfl
rintro i -
rw [monomial_eq, Finsupp.prod_single_index]
rw [pow_zero]
set_option linter.uppercaseLean3 false in
#align witt_polynomial_eq_sum_C_mul_X_pow wittPolynomial_eq_sum_C_mul_X_pow
/-! We set up notation locally to this file, to keep statements short and comprehensible.
This allows us to simply write `W n` or `W_ ℤ n`. -/
-- Notation with ring of coefficients explicit
set_option quotPrecheck false in
@[inherit_doc]
scoped[Witt] notation "W_" => wittPolynomial p
-- Notation with ring of coefficients implicit
set_option quotPrecheck false in
@[inherit_doc]
scoped[Witt] notation "W" => wittPolynomial p _
open Witt
open MvPolynomial
/-! The first observation is that the Witt polynomial doesn't really depend on the coefficient ring.
If we map the coefficients through a ring homomorphism, we obtain the corresponding Witt polynomial
over the target ring. -/
section
variable {R} {S : Type*} [CommRing S]
@[simp]
theorem map_wittPolynomial (f : R →+* S) (n : ℕ) : map f (W n) = W n := by
rw [wittPolynomial, map_sum, wittPolynomial]
refine sum_congr rfl fun i _ => ?_
rw [map_monomial, RingHom.map_pow, map_natCast]
#align map_witt_polynomial map_wittPolynomial
variable (R)
@[simp]
theorem constantCoeff_wittPolynomial [hp : Fact p.Prime] (n : ℕ) :
constantCoeff (wittPolynomial p R n) = 0 := by
simp only [wittPolynomial, map_sum, constantCoeff_monomial]
rw [sum_eq_zero]
rintro i _
rw [if_neg]
rw [Finsupp.single_eq_zero]
exact ne_of_gt (pow_pos hp.1.pos _)
#align constant_coeff_witt_polynomial constantCoeff_wittPolynomial
@[simp]
theorem wittPolynomial_zero : wittPolynomial p R 0 = X 0 := by
simp only [wittPolynomial, X, sum_singleton, range_one, pow_zero, zero_add, tsub_self]
#align witt_polynomial_zero wittPolynomial_zero
@[simp]
theorem wittPolynomial_one : wittPolynomial p R 1 = C (p : R) * X 1 + X 0 ^ p := by
simp only [wittPolynomial_eq_sum_C_mul_X_pow, sum_range_succ_comm, range_one, sum_singleton,
one_mul, pow_one, C_1, pow_zero, tsub_self, tsub_zero]
#align witt_polynomial_one wittPolynomial_one
theorem aeval_wittPolynomial {A : Type*} [CommRing A] [Algebra R A] (f : ℕ → A) (n : ℕ) :
aeval f (W_ R n) = ∑ i ∈ range (n + 1), (p : A) ^ i * f i ^ p ^ (n - i) := by
simp [wittPolynomial, AlgHom.map_sum, aeval_monomial, Finsupp.prod_single_index]
#align aeval_witt_polynomial aeval_wittPolynomial
/-- Over the ring `ZMod (p^(n+1))`, we produce the `n+1`st Witt polynomial
by expanding the `n`th Witt polynomial by `p`. -/
@[simp]
theorem wittPolynomial_zmod_self (n : ℕ) :
W_ (ZMod (p ^ (n + 1))) (n + 1) = expand p (W_ (ZMod (p ^ (n + 1))) n) := by
simp only [wittPolynomial_eq_sum_C_mul_X_pow]
rw [sum_range_succ, ← Nat.cast_pow, CharP.cast_eq_zero (ZMod (p ^ (n + 1))) (p ^ (n + 1)), C_0,
zero_mul, add_zero, AlgHom.map_sum, sum_congr rfl]
intro k hk
rw [AlgHom.map_mul, AlgHom.map_pow, expand_X, algHom_C, ← pow_mul, ← pow_succ']
congr
rw [mem_range] at hk
rw [add_comm, add_tsub_assoc_of_le (Nat.lt_succ_iff.mp hk), ← add_comm]
#align witt_polynomial_zmod_self wittPolynomial_zmod_self
section PPrime
variable [hp : NeZero p]
theorem wittPolynomial_vars [CharZero R] (n : ℕ) : (wittPolynomial p R n).vars = range (n + 1) := by
have : ∀ i, (monomial (Finsupp.single i (p ^ (n - i))) ((p : R) ^ i)).vars = {i} := by
intro i
refine vars_monomial_single i (pow_ne_zero _ hp.1) ?_
rw [← Nat.cast_pow, Nat.cast_ne_zero]
exact pow_ne_zero i hp.1
rw [wittPolynomial, vars_sum_of_disjoint]
· simp only [this, biUnion_singleton_eq_self]
· simp only [this]
intro a b h
apply disjoint_singleton_left.mpr
rwa [mem_singleton]
#align witt_polynomial_vars wittPolynomial_vars
theorem wittPolynomial_vars_subset (n : ℕ) : (wittPolynomial p R n).vars ⊆ range (n + 1) := by
rw [← map_wittPolynomial p (Int.castRingHom R), ← wittPolynomial_vars p ℤ]
apply vars_map
#align witt_polynomial_vars_subset wittPolynomial_vars_subset
end PPrime
end
/-!
## Witt polynomials as a basis of the polynomial algebra
If `p` is invertible in `R`, then the Witt polynomials form a basis
of the polynomial algebra `MvPolynomial ℕ R`.
The polynomials `xInTermsOfW` give the coordinate transformation in the backwards direction.
-/
/-- The `xInTermsOfW p R n` is the polynomial on the basis of Witt polynomials
that corresponds to the ordinary `X n`. -/
noncomputable def xInTermsOfW [Invertible (p : R)] : ℕ → MvPolynomial ℕ R
| n => (X n - ∑ i : Fin n,
C ((p : R) ^ (i : ℕ)) * xInTermsOfW i ^ p ^ (n - (i : ℕ))) * C ((⅟ p : R) ^ n)
set_option linter.uppercaseLean3 false in
#align X_in_terms_of_W xInTermsOfW
theorem xInTermsOfW_eq [Invertible (p : R)] {n : ℕ} : xInTermsOfW p R n =
(X n - ∑ i ∈ range n, C ((p: R) ^ i) * xInTermsOfW p R i ^ p ^ (n - i)) * C ((⅟p : R) ^ n) := by
rw [xInTermsOfW, ← Fin.sum_univ_eq_sum_range]
set_option linter.uppercaseLean3 false in
#align X_in_terms_of_W_eq xInTermsOfW_eq
@[simp]
theorem constantCoeff_xInTermsOfW [hp : Fact p.Prime] [Invertible (p : R)] (n : ℕ) :
constantCoeff (xInTermsOfW p R n) = 0 := by
apply Nat.strongInductionOn n; clear n
intro n IH
rw [xInTermsOfW_eq, mul_comm, RingHom.map_mul, RingHom.map_sub, map_sum, constantCoeff_C,
constantCoeff_X, zero_sub, mul_neg, neg_eq_zero]
-- Porting note: here, we should be able to do `rw [sum_eq_zero]`, but the goal that
-- is created is not what we expect, and the sum is not replaced by zero...
-- is it a bug in `rw` tactic?
refine Eq.trans (?_ : _ = ((⅟↑p : R) ^ n)* 0) (mul_zero _)
congr 1
rw [sum_eq_zero]
intro m H
rw [mem_range] at H
simp only [RingHom.map_mul, RingHom.map_pow, map_natCast, IH m H]
rw [zero_pow, mul_zero]
exact pow_ne_zero _ hp.1.ne_zero
set_option linter.uppercaseLean3 false in
#align constant_coeff_X_in_terms_of_W constantCoeff_xInTermsOfW
@[simp]
| Mathlib/RingTheory/WittVector/WittPolynomial.lean | 239 | 240 | theorem xInTermsOfW_zero [Invertible (p : R)] : xInTermsOfW p R 0 = X 0 := by |
rw [xInTermsOfW_eq, range_zero, sum_empty, pow_zero, C_1, mul_one, sub_zero]
|
/-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Analysis.SpecialFunctions.Trigonometric.Inverse
import Mathlib.Analysis.SpecialFunctions.Trigonometric.Deriv
#align_import analysis.special_functions.trigonometric.inverse_deriv from "leanprover-community/mathlib"@"f2ce6086713c78a7f880485f7917ea547a215982"
/-!
# derivatives of the inverse trigonometric functions
Derivatives of `arcsin` and `arccos`.
-/
noncomputable section
open scoped Classical Topology Filter
open Set Filter
open scoped Real
namespace Real
section Arcsin
theorem deriv_arcsin_aux {x : ℝ} (h₁ : x ≠ -1) (h₂ : x ≠ 1) :
HasStrictDerivAt arcsin (1 / √(1 - x ^ 2)) x ∧ ContDiffAt ℝ ⊤ arcsin x := by
cases' h₁.lt_or_lt with h₁ h₁
· have : 1 - x ^ 2 < 0 := by nlinarith [h₁]
rw [sqrt_eq_zero'.2 this.le, div_zero]
have : arcsin =ᶠ[𝓝 x] fun _ => -(π / 2) :=
(gt_mem_nhds h₁).mono fun y hy => arcsin_of_le_neg_one hy.le
exact ⟨(hasStrictDerivAt_const _ _).congr_of_eventuallyEq this.symm,
contDiffAt_const.congr_of_eventuallyEq this⟩
cases' h₂.lt_or_lt with h₂ h₂
· have : 0 < √(1 - x ^ 2) := sqrt_pos.2 (by nlinarith [h₁, h₂])
simp only [← cos_arcsin, one_div] at this ⊢
exact ⟨sinPartialHomeomorph.hasStrictDerivAt_symm ⟨h₁, h₂⟩ this.ne' (hasStrictDerivAt_sin _),
sinPartialHomeomorph.contDiffAt_symm_deriv this.ne' ⟨h₁, h₂⟩ (hasDerivAt_sin _)
contDiff_sin.contDiffAt⟩
· have : 1 - x ^ 2 < 0 := by nlinarith [h₂]
rw [sqrt_eq_zero'.2 this.le, div_zero]
have : arcsin =ᶠ[𝓝 x] fun _ => π / 2 := (lt_mem_nhds h₂).mono fun y hy => arcsin_of_one_le hy.le
exact ⟨(hasStrictDerivAt_const _ _).congr_of_eventuallyEq this.symm,
contDiffAt_const.congr_of_eventuallyEq this⟩
#align real.deriv_arcsin_aux Real.deriv_arcsin_aux
theorem hasStrictDerivAt_arcsin {x : ℝ} (h₁ : x ≠ -1) (h₂ : x ≠ 1) :
HasStrictDerivAt arcsin (1 / √(1 - x ^ 2)) x :=
(deriv_arcsin_aux h₁ h₂).1
#align real.has_strict_deriv_at_arcsin Real.hasStrictDerivAt_arcsin
theorem hasDerivAt_arcsin {x : ℝ} (h₁ : x ≠ -1) (h₂ : x ≠ 1) :
HasDerivAt arcsin (1 / √(1 - x ^ 2)) x :=
(hasStrictDerivAt_arcsin h₁ h₂).hasDerivAt
#align real.has_deriv_at_arcsin Real.hasDerivAt_arcsin
theorem contDiffAt_arcsin {x : ℝ} (h₁ : x ≠ -1) (h₂ : x ≠ 1) {n : ℕ∞} : ContDiffAt ℝ n arcsin x :=
(deriv_arcsin_aux h₁ h₂).2.of_le le_top
#align real.cont_diff_at_arcsin Real.contDiffAt_arcsin
theorem hasDerivWithinAt_arcsin_Ici {x : ℝ} (h : x ≠ -1) :
HasDerivWithinAt arcsin (1 / √(1 - x ^ 2)) (Ici x) x := by
rcases eq_or_ne x 1 with (rfl | h')
· convert (hasDerivWithinAt_const (1 : ℝ) _ (π / 2)).congr _ _ <;>
simp (config := { contextual := true }) [arcsin_of_one_le]
· exact (hasDerivAt_arcsin h h').hasDerivWithinAt
#align real.has_deriv_within_at_arcsin_Ici Real.hasDerivWithinAt_arcsin_Ici
theorem hasDerivWithinAt_arcsin_Iic {x : ℝ} (h : x ≠ 1) :
HasDerivWithinAt arcsin (1 / √(1 - x ^ 2)) (Iic x) x := by
rcases em (x = -1) with (rfl | h')
· convert (hasDerivWithinAt_const (-1 : ℝ) _ (-(π / 2))).congr _ _ <;>
simp (config := { contextual := true }) [arcsin_of_le_neg_one]
· exact (hasDerivAt_arcsin h' h).hasDerivWithinAt
#align real.has_deriv_within_at_arcsin_Iic Real.hasDerivWithinAt_arcsin_Iic
theorem differentiableWithinAt_arcsin_Ici {x : ℝ} :
DifferentiableWithinAt ℝ arcsin (Ici x) x ↔ x ≠ -1 := by
refine ⟨?_, fun h => (hasDerivWithinAt_arcsin_Ici h).differentiableWithinAt⟩
rintro h rfl
have : sin ∘ arcsin =ᶠ[𝓝[≥] (-1 : ℝ)] id := by
filter_upwards [Icc_mem_nhdsWithin_Ici ⟨le_rfl, neg_lt_self (zero_lt_one' ℝ)⟩] with x using
sin_arcsin'
have := h.hasDerivWithinAt.sin.congr_of_eventuallyEq this.symm (by simp)
simpa using (uniqueDiffOn_Ici _ _ left_mem_Ici).eq_deriv _ this (hasDerivWithinAt_id _ _)
#align real.differentiable_within_at_arcsin_Ici Real.differentiableWithinAt_arcsin_Ici
| Mathlib/Analysis/SpecialFunctions/Trigonometric/InverseDeriv.lean | 93 | 98 | theorem differentiableWithinAt_arcsin_Iic {x : ℝ} :
DifferentiableWithinAt ℝ arcsin (Iic x) x ↔ x ≠ 1 := by |
refine ⟨fun h => ?_, fun h => (hasDerivWithinAt_arcsin_Iic h).differentiableWithinAt⟩
rw [← neg_neg x, ← image_neg_Ici] at h
have := (h.comp (-x) differentiableWithinAt_id.neg (mapsTo_image _ _)).neg
simpa [(· ∘ ·), differentiableWithinAt_arcsin_Ici] using this
|
/-
Copyright (c) 2017 Mario Carneiro. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro, Floris van Doorn, Violeta Hernández Palacios
-/
import Mathlib.SetTheory.Cardinal.Ordinal
import Mathlib.SetTheory.Ordinal.FixedPoint
#align_import set_theory.cardinal.cofinality from "leanprover-community/mathlib"@"7c2ce0c2da15516b4e65d0c9e254bb6dc93abd1f"
/-!
# Cofinality
This file contains the definition of cofinality of an ordinal number and regular cardinals
## Main Definitions
* `Ordinal.cof o` is the cofinality of the ordinal `o`.
If `o` is the order type of the relation `<` on `α`, then `o.cof` is the smallest cardinality of a
subset `s` of α that is *cofinal* in `α`, i.e. `∀ x : α, ∃ y ∈ s, ¬ y < x`.
* `Cardinal.IsStrongLimit c` means that `c` is a strong limit cardinal:
`c ≠ 0 ∧ ∀ x < c, 2 ^ x < c`.
* `Cardinal.IsRegular c` means that `c` is a regular cardinal: `ℵ₀ ≤ c ∧ c.ord.cof = c`.
* `Cardinal.IsInaccessible c` means that `c` is strongly inaccessible:
`ℵ₀ < c ∧ IsRegular c ∧ IsStrongLimit c`.
## Main Statements
* `Ordinal.infinite_pigeonhole_card`: the infinite pigeonhole principle
* `Cardinal.lt_power_cof`: A consequence of König's theorem stating that `c < c ^ c.ord.cof` for
`c ≥ ℵ₀`
* `Cardinal.univ_inaccessible`: The type of ordinals in `Type u` form an inaccessible cardinal
(in `Type v` with `v > u`). This shows (externally) that in `Type u` there are at least `u`
inaccessible cardinals.
## Implementation Notes
* The cofinality is defined for ordinals.
If `c` is a cardinal number, its cofinality is `c.ord.cof`.
## Tags
cofinality, regular cardinals, limits cardinals, inaccessible cardinals,
infinite pigeonhole principle
-/
noncomputable section
open Function Cardinal Set Order
open scoped Classical
open Cardinal Ordinal
universe u v w
variable {α : Type*} {r : α → α → Prop}
/-! ### Cofinality of orders -/
namespace Order
/-- Cofinality of a reflexive order `≼`. This is the smallest cardinality
of a subset `S : Set α` such that `∀ a, ∃ b ∈ S, a ≼ b`. -/
def cof (r : α → α → Prop) : Cardinal :=
sInf { c | ∃ S : Set α, (∀ a, ∃ b ∈ S, r a b) ∧ #S = c }
#align order.cof Order.cof
/-- The set in the definition of `Order.cof` is nonempty. -/
theorem cof_nonempty (r : α → α → Prop) [IsRefl α r] :
{ c | ∃ S : Set α, (∀ a, ∃ b ∈ S, r a b) ∧ #S = c }.Nonempty :=
⟨_, Set.univ, fun a => ⟨a, ⟨⟩, refl _⟩, rfl⟩
#align order.cof_nonempty Order.cof_nonempty
theorem cof_le (r : α → α → Prop) {S : Set α} (h : ∀ a, ∃ b ∈ S, r a b) : cof r ≤ #S :=
csInf_le' ⟨S, h, rfl⟩
#align order.cof_le Order.cof_le
theorem le_cof {r : α → α → Prop} [IsRefl α r] (c : Cardinal) :
c ≤ cof r ↔ ∀ {S : Set α}, (∀ a, ∃ b ∈ S, r a b) → c ≤ #S := by
rw [cof, le_csInf_iff'' (cof_nonempty r)]
use fun H S h => H _ ⟨S, h, rfl⟩
rintro H d ⟨S, h, rfl⟩
exact H h
#align order.le_cof Order.le_cof
end Order
theorem RelIso.cof_le_lift {α : Type u} {β : Type v} {r : α → α → Prop} {s} [IsRefl β s]
(f : r ≃r s) : Cardinal.lift.{max u v} (Order.cof r) ≤
Cardinal.lift.{max u v} (Order.cof s) := by
rw [Order.cof, Order.cof, lift_sInf, lift_sInf,
le_csInf_iff'' ((Order.cof_nonempty s).image _)]
rintro - ⟨-, ⟨u, H, rfl⟩, rfl⟩
apply csInf_le'
refine
⟨_, ⟨f.symm '' u, fun a => ?_, rfl⟩,
lift_mk_eq.{u, v, max u v}.2 ⟨(f.symm.toEquiv.image u).symm⟩⟩
rcases H (f a) with ⟨b, hb, hb'⟩
refine ⟨f.symm b, mem_image_of_mem _ hb, f.map_rel_iff.1 ?_⟩
rwa [RelIso.apply_symm_apply]
#align rel_iso.cof_le_lift RelIso.cof_le_lift
theorem RelIso.cof_eq_lift {α : Type u} {β : Type v} {r s} [IsRefl α r] [IsRefl β s] (f : r ≃r s) :
Cardinal.lift.{max u v} (Order.cof r) = Cardinal.lift.{max u v} (Order.cof s) :=
(RelIso.cof_le_lift f).antisymm (RelIso.cof_le_lift f.symm)
#align rel_iso.cof_eq_lift RelIso.cof_eq_lift
theorem RelIso.cof_le {α β : Type u} {r : α → α → Prop} {s} [IsRefl β s] (f : r ≃r s) :
Order.cof r ≤ Order.cof s :=
lift_le.1 (RelIso.cof_le_lift f)
#align rel_iso.cof_le RelIso.cof_le
theorem RelIso.cof_eq {α β : Type u} {r s} [IsRefl α r] [IsRefl β s] (f : r ≃r s) :
Order.cof r = Order.cof s :=
lift_inj.1 (RelIso.cof_eq_lift f)
#align rel_iso.cof_eq RelIso.cof_eq
/-- Cofinality of a strict order `≺`. This is the smallest cardinality of a set `S : Set α` such
that `∀ a, ∃ b ∈ S, ¬ b ≺ a`. -/
def StrictOrder.cof (r : α → α → Prop) : Cardinal :=
Order.cof (swap rᶜ)
#align strict_order.cof StrictOrder.cof
/-- The set in the definition of `Order.StrictOrder.cof` is nonempty. -/
theorem StrictOrder.cof_nonempty (r : α → α → Prop) [IsIrrefl α r] :
{ c | ∃ S : Set α, Unbounded r S ∧ #S = c }.Nonempty :=
@Order.cof_nonempty α _ (IsRefl.swap rᶜ)
#align strict_order.cof_nonempty StrictOrder.cof_nonempty
/-! ### Cofinality of ordinals -/
namespace Ordinal
/-- Cofinality of an ordinal. This is the smallest cardinal of a
subset `S` of the ordinal which is unbounded, in the sense
`∀ a, ∃ b ∈ S, a ≤ b`. It is defined for all ordinals, but
`cof 0 = 0` and `cof (succ o) = 1`, so it is only really
interesting on limit ordinals (when it is an infinite cardinal). -/
def cof (o : Ordinal.{u}) : Cardinal.{u} :=
o.liftOn (fun a => StrictOrder.cof a.r)
(by
rintro ⟨α, r, wo₁⟩ ⟨β, s, wo₂⟩ ⟨⟨f, hf⟩⟩
haveI := wo₁; haveI := wo₂
dsimp only
apply @RelIso.cof_eq _ _ _ _ ?_ ?_
· constructor
exact @fun a b => not_iff_not.2 hf
· dsimp only [swap]
exact ⟨fun _ => irrefl _⟩
· dsimp only [swap]
exact ⟨fun _ => irrefl _⟩)
#align ordinal.cof Ordinal.cof
theorem cof_type (r : α → α → Prop) [IsWellOrder α r] : (type r).cof = StrictOrder.cof r :=
rfl
#align ordinal.cof_type Ordinal.cof_type
theorem le_cof_type [IsWellOrder α r] {c} : c ≤ cof (type r) ↔ ∀ S, Unbounded r S → c ≤ #S :=
(le_csInf_iff'' (StrictOrder.cof_nonempty r)).trans
⟨fun H S h => H _ ⟨S, h, rfl⟩, by
rintro H d ⟨S, h, rfl⟩
exact H _ h⟩
#align ordinal.le_cof_type Ordinal.le_cof_type
theorem cof_type_le [IsWellOrder α r] {S : Set α} (h : Unbounded r S) : cof (type r) ≤ #S :=
le_cof_type.1 le_rfl S h
#align ordinal.cof_type_le Ordinal.cof_type_le
theorem lt_cof_type [IsWellOrder α r] {S : Set α} : #S < cof (type r) → Bounded r S := by
simpa using not_imp_not.2 cof_type_le
#align ordinal.lt_cof_type Ordinal.lt_cof_type
theorem cof_eq (r : α → α → Prop) [IsWellOrder α r] : ∃ S, Unbounded r S ∧ #S = cof (type r) :=
csInf_mem (StrictOrder.cof_nonempty r)
#align ordinal.cof_eq Ordinal.cof_eq
theorem ord_cof_eq (r : α → α → Prop) [IsWellOrder α r] :
∃ S, Unbounded r S ∧ type (Subrel r S) = (cof (type r)).ord := by
let ⟨S, hS, e⟩ := cof_eq r
let ⟨s, _, e'⟩ := Cardinal.ord_eq S
let T : Set α := { a | ∃ aS : a ∈ S, ∀ b : S, s b ⟨_, aS⟩ → r b a }
suffices Unbounded r T by
refine ⟨T, this, le_antisymm ?_ (Cardinal.ord_le.2 <| cof_type_le this)⟩
rw [← e, e']
refine
(RelEmbedding.ofMonotone
(fun a : T =>
(⟨a,
let ⟨aS, _⟩ := a.2
aS⟩ :
S))
fun a b h => ?_).ordinal_type_le
rcases a with ⟨a, aS, ha⟩
rcases b with ⟨b, bS, hb⟩
change s ⟨a, _⟩ ⟨b, _⟩
refine ((trichotomous_of s _ _).resolve_left fun hn => ?_).resolve_left ?_
· exact asymm h (ha _ hn)
· intro e
injection e with e
subst b
exact irrefl _ h
intro a
have : { b : S | ¬r b a }.Nonempty :=
let ⟨b, bS, ba⟩ := hS a
⟨⟨b, bS⟩, ba⟩
let b := (IsWellFounded.wf : WellFounded s).min _ this
have ba : ¬r b a := IsWellFounded.wf.min_mem _ this
refine ⟨b, ⟨b.2, fun c => not_imp_not.1 fun h => ?_⟩, ba⟩
rw [show ∀ b : S, (⟨b, b.2⟩ : S) = b by intro b; cases b; rfl]
exact IsWellFounded.wf.not_lt_min _ this (IsOrderConnected.neg_trans h ba)
#align ordinal.ord_cof_eq Ordinal.ord_cof_eq
/-! ### Cofinality of suprema and least strict upper bounds -/
private theorem card_mem_cof {o} : ∃ (ι : _) (f : ι → Ordinal), lsub.{u, u} f = o ∧ #ι = o.card :=
⟨_, _, lsub_typein o, mk_ordinal_out o⟩
/-- The set in the `lsub` characterization of `cof` is nonempty. -/
theorem cof_lsub_def_nonempty (o) :
{ a : Cardinal | ∃ (ι : _) (f : ι → Ordinal), lsub.{u, u} f = o ∧ #ι = a }.Nonempty :=
⟨_, card_mem_cof⟩
#align ordinal.cof_lsub_def_nonempty Ordinal.cof_lsub_def_nonempty
theorem cof_eq_sInf_lsub (o : Ordinal.{u}) : cof o =
sInf { a : Cardinal | ∃ (ι : Type u) (f : ι → Ordinal), lsub.{u, u} f = o ∧ #ι = a } := by
refine le_antisymm (le_csInf (cof_lsub_def_nonempty o) ?_) (csInf_le' ?_)
· rintro a ⟨ι, f, hf, rfl⟩
rw [← type_lt o]
refine
(cof_type_le fun a => ?_).trans
(@mk_le_of_injective _ _
(fun s : typein ((· < ·) : o.out.α → o.out.α → Prop) ⁻¹' Set.range f =>
Classical.choose s.prop)
fun s t hst => by
let H := congr_arg f hst
rwa [Classical.choose_spec s.prop, Classical.choose_spec t.prop, typein_inj,
Subtype.coe_inj] at H)
have := typein_lt_self a
simp_rw [← hf, lt_lsub_iff] at this
cases' this with i hi
refine ⟨enum (· < ·) (f i) ?_, ?_, ?_⟩
· rw [type_lt, ← hf]
apply lt_lsub
· rw [mem_preimage, typein_enum]
exact mem_range_self i
· rwa [← typein_le_typein, typein_enum]
· rcases cof_eq (· < · : (Quotient.out o).α → (Quotient.out o).α → Prop) with ⟨S, hS, hS'⟩
let f : S → Ordinal := fun s => typein LT.lt s.val
refine ⟨S, f, le_antisymm (lsub_le fun i => typein_lt_self (o := o) i)
(le_of_forall_lt fun a ha => ?_), by rwa [type_lt o] at hS'⟩
rw [← type_lt o] at ha
rcases hS (enum (· < ·) a ha) with ⟨b, hb, hb'⟩
rw [← typein_le_typein, typein_enum] at hb'
exact hb'.trans_lt (lt_lsub.{u, u} f ⟨b, hb⟩)
#align ordinal.cof_eq_Inf_lsub Ordinal.cof_eq_sInf_lsub
@[simp]
theorem lift_cof (o) : Cardinal.lift.{u, v} (cof o) = cof (Ordinal.lift.{u, v} o) := by
refine inductionOn o ?_
intro α r _
apply le_antisymm
· refine le_cof_type.2 fun S H => ?_
have : Cardinal.lift.{u, v} #(ULift.up ⁻¹' S) ≤ #(S : Type (max u v)) := by
rw [← Cardinal.lift_umax.{v, u}, ← Cardinal.lift_id'.{v, u} #S]
exact mk_preimage_of_injective_lift.{v, max u v} ULift.up S (ULift.up_injective.{u, v})
refine (Cardinal.lift_le.2 <| cof_type_le ?_).trans this
exact fun a =>
let ⟨⟨b⟩, bs, br⟩ := H ⟨a⟩
⟨b, bs, br⟩
· rcases cof_eq r with ⟨S, H, e'⟩
have : #(ULift.down.{u, v} ⁻¹' S) ≤ Cardinal.lift.{u, v} #S :=
⟨⟨fun ⟨⟨x⟩, h⟩ => ⟨⟨x, h⟩⟩, fun ⟨⟨x⟩, h₁⟩ ⟨⟨y⟩, h₂⟩ e => by
simp at e; congr⟩⟩
rw [e'] at this
refine (cof_type_le ?_).trans this
exact fun ⟨a⟩ =>
let ⟨b, bs, br⟩ := H a
⟨⟨b⟩, bs, br⟩
#align ordinal.lift_cof Ordinal.lift_cof
theorem cof_le_card (o) : cof o ≤ card o := by
rw [cof_eq_sInf_lsub]
exact csInf_le' card_mem_cof
#align ordinal.cof_le_card Ordinal.cof_le_card
theorem cof_ord_le (c : Cardinal) : c.ord.cof ≤ c := by simpa using cof_le_card c.ord
#align ordinal.cof_ord_le Ordinal.cof_ord_le
theorem ord_cof_le (o : Ordinal.{u}) : o.cof.ord ≤ o :=
(ord_le_ord.2 (cof_le_card o)).trans (ord_card_le o)
#align ordinal.ord_cof_le Ordinal.ord_cof_le
theorem exists_lsub_cof (o : Ordinal) :
∃ (ι : _) (f : ι → Ordinal), lsub.{u, u} f = o ∧ #ι = cof o := by
rw [cof_eq_sInf_lsub]
exact csInf_mem (cof_lsub_def_nonempty o)
#align ordinal.exists_lsub_cof Ordinal.exists_lsub_cof
theorem cof_lsub_le {ι} (f : ι → Ordinal) : cof (lsub.{u, u} f) ≤ #ι := by
rw [cof_eq_sInf_lsub]
exact csInf_le' ⟨ι, f, rfl, rfl⟩
#align ordinal.cof_lsub_le Ordinal.cof_lsub_le
theorem cof_lsub_le_lift {ι} (f : ι → Ordinal) :
cof (lsub.{u, v} f) ≤ Cardinal.lift.{v, u} #ι := by
rw [← mk_uLift.{u, v}]
convert cof_lsub_le.{max u v} fun i : ULift.{v, u} ι => f i.down
exact
lsub_eq_of_range_eq.{u, max u v, max u v}
(Set.ext fun x => ⟨fun ⟨i, hi⟩ => ⟨ULift.up.{v, u} i, hi⟩, fun ⟨i, hi⟩ => ⟨_, hi⟩⟩)
#align ordinal.cof_lsub_le_lift Ordinal.cof_lsub_le_lift
theorem le_cof_iff_lsub {o : Ordinal} {a : Cardinal} :
a ≤ cof o ↔ ∀ {ι} (f : ι → Ordinal), lsub.{u, u} f = o → a ≤ #ι := by
rw [cof_eq_sInf_lsub]
exact
(le_csInf_iff'' (cof_lsub_def_nonempty o)).trans
⟨fun H ι f hf => H _ ⟨ι, f, hf, rfl⟩, fun H b ⟨ι, f, hf, hb⟩ => by
rw [← hb]
exact H _ hf⟩
#align ordinal.le_cof_iff_lsub Ordinal.le_cof_iff_lsub
theorem lsub_lt_ord_lift {ι} {f : ι → Ordinal} {c : Ordinal}
(hι : Cardinal.lift.{v, u} #ι < c.cof)
(hf : ∀ i, f i < c) : lsub.{u, v} f < c :=
lt_of_le_of_ne (lsub_le.{v, u} hf) fun h => by
subst h
exact (cof_lsub_le_lift.{u, v} f).not_lt hι
#align ordinal.lsub_lt_ord_lift Ordinal.lsub_lt_ord_lift
theorem lsub_lt_ord {ι} {f : ι → Ordinal} {c : Ordinal} (hι : #ι < c.cof) :
(∀ i, f i < c) → lsub.{u, u} f < c :=
lsub_lt_ord_lift (by rwa [(#ι).lift_id])
#align ordinal.lsub_lt_ord Ordinal.lsub_lt_ord
theorem cof_sup_le_lift {ι} {f : ι → Ordinal} (H : ∀ i, f i < sup.{u, v} f) :
cof (sup.{u, v} f) ≤ Cardinal.lift.{v, u} #ι := by
rw [← sup_eq_lsub_iff_lt_sup.{u, v}] at H
rw [H]
exact cof_lsub_le_lift f
#align ordinal.cof_sup_le_lift Ordinal.cof_sup_le_lift
theorem cof_sup_le {ι} {f : ι → Ordinal} (H : ∀ i, f i < sup.{u, u} f) :
cof (sup.{u, u} f) ≤ #ι := by
rw [← (#ι).lift_id]
exact cof_sup_le_lift H
#align ordinal.cof_sup_le Ordinal.cof_sup_le
theorem sup_lt_ord_lift {ι} {f : ι → Ordinal} {c : Ordinal} (hι : Cardinal.lift.{v, u} #ι < c.cof)
(hf : ∀ i, f i < c) : sup.{u, v} f < c :=
(sup_le_lsub.{u, v} f).trans_lt (lsub_lt_ord_lift hι hf)
#align ordinal.sup_lt_ord_lift Ordinal.sup_lt_ord_lift
theorem sup_lt_ord {ι} {f : ι → Ordinal} {c : Ordinal} (hι : #ι < c.cof) :
(∀ i, f i < c) → sup.{u, u} f < c :=
sup_lt_ord_lift (by rwa [(#ι).lift_id])
#align ordinal.sup_lt_ord Ordinal.sup_lt_ord
theorem iSup_lt_lift {ι} {f : ι → Cardinal} {c : Cardinal}
(hι : Cardinal.lift.{v, u} #ι < c.ord.cof)
(hf : ∀ i, f i < c) : iSup.{max u v + 1, u + 1} f < c := by
rw [← ord_lt_ord, iSup_ord (Cardinal.bddAbove_range.{u, v} _)]
refine sup_lt_ord_lift hι fun i => ?_
rw [ord_lt_ord]
apply hf
#align ordinal.supr_lt_lift Ordinal.iSup_lt_lift
theorem iSup_lt {ι} {f : ι → Cardinal} {c : Cardinal} (hι : #ι < c.ord.cof) :
(∀ i, f i < c) → iSup f < c :=
iSup_lt_lift (by rwa [(#ι).lift_id])
#align ordinal.supr_lt Ordinal.iSup_lt
theorem nfpFamily_lt_ord_lift {ι} {f : ι → Ordinal → Ordinal} {c} (hc : ℵ₀ < cof c)
(hc' : Cardinal.lift.{v, u} #ι < cof c) (hf : ∀ (i), ∀ b < c, f i b < c) {a} (ha : a < c) :
nfpFamily.{u, v} f a < c := by
refine sup_lt_ord_lift ((Cardinal.lift_le.2 (mk_list_le_max ι)).trans_lt ?_) fun l => ?_
· rw [lift_max]
apply max_lt _ hc'
rwa [Cardinal.lift_aleph0]
· induction' l with i l H
· exact ha
· exact hf _ _ H
#align ordinal.nfp_family_lt_ord_lift Ordinal.nfpFamily_lt_ord_lift
theorem nfpFamily_lt_ord {ι} {f : ι → Ordinal → Ordinal} {c} (hc : ℵ₀ < cof c) (hc' : #ι < cof c)
(hf : ∀ (i), ∀ b < c, f i b < c) {a} : a < c → nfpFamily.{u, u} f a < c :=
nfpFamily_lt_ord_lift hc (by rwa [(#ι).lift_id]) hf
#align ordinal.nfp_family_lt_ord Ordinal.nfpFamily_lt_ord
theorem nfpBFamily_lt_ord_lift {o : Ordinal} {f : ∀ a < o, Ordinal → Ordinal} {c} (hc : ℵ₀ < cof c)
(hc' : Cardinal.lift.{v, u} o.card < cof c) (hf : ∀ (i hi), ∀ b < c, f i hi b < c) {a} :
a < c → nfpBFamily.{u, v} o f a < c :=
nfpFamily_lt_ord_lift hc (by rwa [mk_ordinal_out]) fun i => hf _ _
#align ordinal.nfp_bfamily_lt_ord_lift Ordinal.nfpBFamily_lt_ord_lift
theorem nfpBFamily_lt_ord {o : Ordinal} {f : ∀ a < o, Ordinal → Ordinal} {c} (hc : ℵ₀ < cof c)
(hc' : o.card < cof c) (hf : ∀ (i hi), ∀ b < c, f i hi b < c) {a} :
a < c → nfpBFamily.{u, u} o f a < c :=
nfpBFamily_lt_ord_lift hc (by rwa [o.card.lift_id]) hf
#align ordinal.nfp_bfamily_lt_ord Ordinal.nfpBFamily_lt_ord
theorem nfp_lt_ord {f : Ordinal → Ordinal} {c} (hc : ℵ₀ < cof c) (hf : ∀ i < c, f i < c) {a} :
a < c → nfp f a < c :=
nfpFamily_lt_ord_lift hc (by simpa using Cardinal.one_lt_aleph0.trans hc) fun _ => hf
#align ordinal.nfp_lt_ord Ordinal.nfp_lt_ord
theorem exists_blsub_cof (o : Ordinal) :
∃ f : ∀ a < (cof o).ord, Ordinal, blsub.{u, u} _ f = o := by
rcases exists_lsub_cof o with ⟨ι, f, hf, hι⟩
rcases Cardinal.ord_eq ι with ⟨r, hr, hι'⟩
rw [← @blsub_eq_lsub' ι r hr] at hf
rw [← hι, hι']
exact ⟨_, hf⟩
#align ordinal.exists_blsub_cof Ordinal.exists_blsub_cof
theorem le_cof_iff_blsub {b : Ordinal} {a : Cardinal} :
a ≤ cof b ↔ ∀ {o} (f : ∀ a < o, Ordinal), blsub.{u, u} o f = b → a ≤ o.card :=
le_cof_iff_lsub.trans
⟨fun H o f hf => by simpa using H _ hf, fun H ι f hf => by
rcases Cardinal.ord_eq ι with ⟨r, hr, hι'⟩
rw [← @blsub_eq_lsub' ι r hr] at hf
simpa using H _ hf⟩
#align ordinal.le_cof_iff_blsub Ordinal.le_cof_iff_blsub
theorem cof_blsub_le_lift {o} (f : ∀ a < o, Ordinal) :
cof (blsub.{u, v} o f) ≤ Cardinal.lift.{v, u} o.card := by
rw [← mk_ordinal_out o]
exact cof_lsub_le_lift _
#align ordinal.cof_blsub_le_lift Ordinal.cof_blsub_le_lift
theorem cof_blsub_le {o} (f : ∀ a < o, Ordinal) : cof (blsub.{u, u} o f) ≤ o.card := by
rw [← o.card.lift_id]
exact cof_blsub_le_lift f
#align ordinal.cof_blsub_le Ordinal.cof_blsub_le
theorem blsub_lt_ord_lift {o : Ordinal.{u}} {f : ∀ a < o, Ordinal} {c : Ordinal}
(ho : Cardinal.lift.{v, u} o.card < c.cof) (hf : ∀ i hi, f i hi < c) : blsub.{u, v} o f < c :=
lt_of_le_of_ne (blsub_le hf) fun h =>
ho.not_le (by simpa [← iSup_ord, hf, h] using cof_blsub_le_lift.{u, v} f)
#align ordinal.blsub_lt_ord_lift Ordinal.blsub_lt_ord_lift
theorem blsub_lt_ord {o : Ordinal} {f : ∀ a < o, Ordinal} {c : Ordinal} (ho : o.card < c.cof)
(hf : ∀ i hi, f i hi < c) : blsub.{u, u} o f < c :=
blsub_lt_ord_lift (by rwa [o.card.lift_id]) hf
#align ordinal.blsub_lt_ord Ordinal.blsub_lt_ord
theorem cof_bsup_le_lift {o : Ordinal} {f : ∀ a < o, Ordinal} (H : ∀ i h, f i h < bsup.{u, v} o f) :
cof (bsup.{u, v} o f) ≤ Cardinal.lift.{v, u} o.card := by
rw [← bsup_eq_blsub_iff_lt_bsup.{u, v}] at H
rw [H]
exact cof_blsub_le_lift.{u, v} f
#align ordinal.cof_bsup_le_lift Ordinal.cof_bsup_le_lift
theorem cof_bsup_le {o : Ordinal} {f : ∀ a < o, Ordinal} :
(∀ i h, f i h < bsup.{u, u} o f) → cof (bsup.{u, u} o f) ≤ o.card := by
rw [← o.card.lift_id]
exact cof_bsup_le_lift
#align ordinal.cof_bsup_le Ordinal.cof_bsup_le
theorem bsup_lt_ord_lift {o : Ordinal} {f : ∀ a < o, Ordinal} {c : Ordinal}
(ho : Cardinal.lift.{v, u} o.card < c.cof) (hf : ∀ i hi, f i hi < c) : bsup.{u, v} o f < c :=
(bsup_le_blsub f).trans_lt (blsub_lt_ord_lift ho hf)
#align ordinal.bsup_lt_ord_lift Ordinal.bsup_lt_ord_lift
theorem bsup_lt_ord {o : Ordinal} {f : ∀ a < o, Ordinal} {c : Ordinal} (ho : o.card < c.cof) :
(∀ i hi, f i hi < c) → bsup.{u, u} o f < c :=
bsup_lt_ord_lift (by rwa [o.card.lift_id])
#align ordinal.bsup_lt_ord Ordinal.bsup_lt_ord
/-! ### Basic results -/
@[simp]
theorem cof_zero : cof 0 = 0 := by
refine LE.le.antisymm ?_ (Cardinal.zero_le _)
rw [← card_zero]
exact cof_le_card 0
#align ordinal.cof_zero Ordinal.cof_zero
@[simp]
theorem cof_eq_zero {o} : cof o = 0 ↔ o = 0 :=
⟨inductionOn o fun α r _ z =>
let ⟨S, hl, e⟩ := cof_eq r
type_eq_zero_iff_isEmpty.2 <|
⟨fun a =>
let ⟨b, h, _⟩ := hl a
(mk_eq_zero_iff.1 (e.trans z)).elim' ⟨_, h⟩⟩,
fun e => by simp [e]⟩
#align ordinal.cof_eq_zero Ordinal.cof_eq_zero
theorem cof_ne_zero {o} : cof o ≠ 0 ↔ o ≠ 0 :=
cof_eq_zero.not
#align ordinal.cof_ne_zero Ordinal.cof_ne_zero
@[simp]
theorem cof_succ (o) : cof (succ o) = 1 := by
apply le_antisymm
· refine inductionOn o fun α r _ => ?_
change cof (type _) ≤ _
rw [← (_ : #_ = 1)]
· apply cof_type_le
refine fun a => ⟨Sum.inr PUnit.unit, Set.mem_singleton _, ?_⟩
rcases a with (a | ⟨⟨⟨⟩⟩⟩) <;> simp [EmptyRelation]
· rw [Cardinal.mk_fintype, Set.card_singleton]
simp
· rw [← Cardinal.succ_zero, succ_le_iff]
simpa [lt_iff_le_and_ne, Cardinal.zero_le] using fun h =>
succ_ne_zero o (cof_eq_zero.1 (Eq.symm h))
#align ordinal.cof_succ Ordinal.cof_succ
@[simp]
theorem cof_eq_one_iff_is_succ {o} : cof.{u} o = 1 ↔ ∃ a, o = succ a :=
⟨inductionOn o fun α r _ z => by
rcases cof_eq r with ⟨S, hl, e⟩; rw [z] at e
cases' mk_ne_zero_iff.1 (by rw [e]; exact one_ne_zero) with a
refine
⟨typein r a,
Eq.symm <|
Quotient.sound
⟨RelIso.ofSurjective (RelEmbedding.ofMonotone ?_ fun x y => ?_) fun x => ?_⟩⟩
· apply Sum.rec <;> [exact Subtype.val; exact fun _ => a]
· rcases x with (x | ⟨⟨⟨⟩⟩⟩) <;> rcases y with (y | ⟨⟨⟨⟩⟩⟩) <;>
simp [Subrel, Order.Preimage, EmptyRelation]
exact x.2
· suffices r x a ∨ ∃ _ : PUnit.{u}, ↑a = x by
convert this
dsimp [RelEmbedding.ofMonotone]; simp
rcases trichotomous_of r x a with (h | h | h)
· exact Or.inl h
· exact Or.inr ⟨PUnit.unit, h.symm⟩
· rcases hl x with ⟨a', aS, hn⟩
rw [(_ : ↑a = a')] at h
· exact absurd h hn
refine congr_arg Subtype.val (?_ : a = ⟨a', aS⟩)
haveI := le_one_iff_subsingleton.1 (le_of_eq e)
apply Subsingleton.elim,
fun ⟨a, e⟩ => by simp [e]⟩
#align ordinal.cof_eq_one_iff_is_succ Ordinal.cof_eq_one_iff_is_succ
/-- A fundamental sequence for `a` is an increasing sequence of length `o = cof a` that converges at
`a`. We provide `o` explicitly in order to avoid type rewrites. -/
def IsFundamentalSequence (a o : Ordinal.{u}) (f : ∀ b < o, Ordinal.{u}) : Prop :=
o ≤ a.cof.ord ∧ (∀ {i j} (hi hj), i < j → f i hi < f j hj) ∧ blsub.{u, u} o f = a
#align ordinal.is_fundamental_sequence Ordinal.IsFundamentalSequence
namespace IsFundamentalSequence
variable {a o : Ordinal.{u}} {f : ∀ b < o, Ordinal.{u}}
protected theorem cof_eq (hf : IsFundamentalSequence a o f) : a.cof.ord = o :=
hf.1.antisymm' <| by
rw [← hf.2.2]
exact (ord_le_ord.2 (cof_blsub_le f)).trans (ord_card_le o)
#align ordinal.is_fundamental_sequence.cof_eq Ordinal.IsFundamentalSequence.cof_eq
protected theorem strict_mono (hf : IsFundamentalSequence a o f) {i j} :
∀ hi hj, i < j → f i hi < f j hj :=
hf.2.1
#align ordinal.is_fundamental_sequence.strict_mono Ordinal.IsFundamentalSequence.strict_mono
theorem blsub_eq (hf : IsFundamentalSequence a o f) : blsub.{u, u} o f = a :=
hf.2.2
#align ordinal.is_fundamental_sequence.blsub_eq Ordinal.IsFundamentalSequence.blsub_eq
theorem ord_cof (hf : IsFundamentalSequence a o f) :
IsFundamentalSequence a a.cof.ord fun i hi => f i (hi.trans_le (by rw [hf.cof_eq])) := by
have H := hf.cof_eq
subst H
exact hf
#align ordinal.is_fundamental_sequence.ord_cof Ordinal.IsFundamentalSequence.ord_cof
theorem id_of_le_cof (h : o ≤ o.cof.ord) : IsFundamentalSequence o o fun a _ => a :=
⟨h, @fun _ _ _ _ => id, blsub_id o⟩
#align ordinal.is_fundamental_sequence.id_of_le_cof Ordinal.IsFundamentalSequence.id_of_le_cof
protected theorem zero {f : ∀ b < (0 : Ordinal), Ordinal} : IsFundamentalSequence 0 0 f :=
⟨by rw [cof_zero, ord_zero], @fun i j hi => (Ordinal.not_lt_zero i hi).elim, blsub_zero f⟩
#align ordinal.is_fundamental_sequence.zero Ordinal.IsFundamentalSequence.zero
protected theorem succ : IsFundamentalSequence (succ o) 1 fun _ _ => o := by
refine ⟨?_, @fun i j hi hj h => ?_, blsub_const Ordinal.one_ne_zero o⟩
· rw [cof_succ, ord_one]
· rw [lt_one_iff_zero] at hi hj
rw [hi, hj] at h
exact h.false.elim
#align ordinal.is_fundamental_sequence.succ Ordinal.IsFundamentalSequence.succ
protected theorem monotone (hf : IsFundamentalSequence a o f) {i j : Ordinal} (hi : i < o)
(hj : j < o) (hij : i ≤ j) : f i hi ≤ f j hj := by
rcases lt_or_eq_of_le hij with (hij | rfl)
· exact (hf.2.1 hi hj hij).le
· rfl
#align ordinal.is_fundamental_sequence.monotone Ordinal.IsFundamentalSequence.monotone
theorem trans {a o o' : Ordinal.{u}} {f : ∀ b < o, Ordinal.{u}} (hf : IsFundamentalSequence a o f)
{g : ∀ b < o', Ordinal.{u}} (hg : IsFundamentalSequence o o' g) :
IsFundamentalSequence a o' fun i hi =>
f (g i hi) (by rw [← hg.2.2]; apply lt_blsub) := by
refine ⟨?_, @fun i j _ _ h => hf.2.1 _ _ (hg.2.1 _ _ h), ?_⟩
· rw [hf.cof_eq]
exact hg.1.trans (ord_cof_le o)
· rw [@blsub_comp.{u, u, u} o _ f (@IsFundamentalSequence.monotone _ _ f hf)]
· exact hf.2.2
· exact hg.2.2
#align ordinal.is_fundamental_sequence.trans Ordinal.IsFundamentalSequence.trans
end IsFundamentalSequence
/-- Every ordinal has a fundamental sequence. -/
theorem exists_fundamental_sequence (a : Ordinal.{u}) :
∃ f, IsFundamentalSequence a a.cof.ord f := by
suffices h : ∃ o f, IsFundamentalSequence a o f by
rcases h with ⟨o, f, hf⟩
exact ⟨_, hf.ord_cof⟩
rcases exists_lsub_cof a with ⟨ι, f, hf, hι⟩
rcases ord_eq ι with ⟨r, wo, hr⟩
haveI := wo
let r' := Subrel r { i | ∀ j, r j i → f j < f i }
let hrr' : r' ↪r r := Subrel.relEmbedding _ _
haveI := hrr'.isWellOrder
refine
⟨_, _, hrr'.ordinal_type_le.trans ?_, @fun i j _ h _ => (enum r' j h).prop _ ?_,
le_antisymm (blsub_le fun i hi => lsub_le_iff.1 hf.le _) ?_⟩
· rw [← hι, hr]
· change r (hrr'.1 _) (hrr'.1 _)
rwa [hrr'.2, @enum_lt_enum _ r']
· rw [← hf, lsub_le_iff]
intro i
suffices h : ∃ i' hi', f i ≤ bfamilyOfFamily' r' (fun i => f i) i' hi' by
rcases h with ⟨i', hi', hfg⟩
exact hfg.trans_lt (lt_blsub _ _ _)
by_cases h : ∀ j, r j i → f j < f i
· refine ⟨typein r' ⟨i, h⟩, typein_lt_type _ _, ?_⟩
rw [bfamilyOfFamily'_typein]
· push_neg at h
cases' wo.wf.min_mem _ h with hji hij
refine ⟨typein r' ⟨_, fun k hkj => lt_of_lt_of_le ?_ hij⟩, typein_lt_type _ _, ?_⟩
· by_contra! H
exact (wo.wf.not_lt_min _ h ⟨IsTrans.trans _ _ _ hkj hji, H⟩) hkj
· rwa [bfamilyOfFamily'_typein]
#align ordinal.exists_fundamental_sequence Ordinal.exists_fundamental_sequence
@[simp]
theorem cof_cof (a : Ordinal.{u}) : cof (cof a).ord = cof a := by
cases' exists_fundamental_sequence a with f hf
cases' exists_fundamental_sequence a.cof.ord with g hg
exact ord_injective (hf.trans hg).cof_eq.symm
#align ordinal.cof_cof Ordinal.cof_cof
protected theorem IsNormal.isFundamentalSequence {f : Ordinal.{u} → Ordinal.{u}} (hf : IsNormal f)
{a o} (ha : IsLimit a) {g} (hg : IsFundamentalSequence a o g) :
IsFundamentalSequence (f a) o fun b hb => f (g b hb) := by
refine ⟨?_, @fun i j _ _ h => hf.strictMono (hg.2.1 _ _ h), ?_⟩
· rcases exists_lsub_cof (f a) with ⟨ι, f', hf', hι⟩
rw [← hg.cof_eq, ord_le_ord, ← hι]
suffices (lsub.{u, u} fun i => sInf { b : Ordinal | f' i ≤ f b }) = a by
rw [← this]
apply cof_lsub_le
have H : ∀ i, ∃ b < a, f' i ≤ f b := fun i => by
have := lt_lsub.{u, u} f' i
rw [hf', ← IsNormal.blsub_eq.{u, u} hf ha, lt_blsub_iff] at this
simpa using this
refine (lsub_le fun i => ?_).antisymm (le_of_forall_lt fun b hb => ?_)
· rcases H i with ⟨b, hb, hb'⟩
exact lt_of_le_of_lt (csInf_le' hb') hb
· have := hf.strictMono hb
rw [← hf', lt_lsub_iff] at this
cases' this with i hi
rcases H i with ⟨b, _, hb⟩
exact
((le_csInf_iff'' ⟨b, by exact hb⟩).2 fun c hc =>
hf.strictMono.le_iff_le.1 (hi.trans hc)).trans_lt (lt_lsub _ i)
· rw [@blsub_comp.{u, u, u} a _ (fun b _ => f b) (@fun i j _ _ h => hf.strictMono.monotone h) g
hg.2.2]
exact IsNormal.blsub_eq.{u, u} hf ha
#align ordinal.is_normal.is_fundamental_sequence Ordinal.IsNormal.isFundamentalSequence
theorem IsNormal.cof_eq {f} (hf : IsNormal f) {a} (ha : IsLimit a) : cof (f a) = cof a :=
let ⟨_, hg⟩ := exists_fundamental_sequence a
ord_injective (hf.isFundamentalSequence ha hg).cof_eq
#align ordinal.is_normal.cof_eq Ordinal.IsNormal.cof_eq
theorem IsNormal.cof_le {f} (hf : IsNormal f) (a) : cof a ≤ cof (f a) := by
rcases zero_or_succ_or_limit a with (rfl | ⟨b, rfl⟩ | ha)
· rw [cof_zero]
exact zero_le _
· rw [cof_succ, Cardinal.one_le_iff_ne_zero, cof_ne_zero, ← Ordinal.pos_iff_ne_zero]
exact (Ordinal.zero_le (f b)).trans_lt (hf.1 b)
· rw [hf.cof_eq ha]
#align ordinal.is_normal.cof_le Ordinal.IsNormal.cof_le
@[simp]
theorem cof_add (a b : Ordinal) : b ≠ 0 → cof (a + b) = cof b := fun h => by
rcases zero_or_succ_or_limit b with (rfl | ⟨c, rfl⟩ | hb)
· contradiction
· rw [add_succ, cof_succ, cof_succ]
· exact (add_isNormal a).cof_eq hb
#align ordinal.cof_add Ordinal.cof_add
theorem aleph0_le_cof {o} : ℵ₀ ≤ cof o ↔ IsLimit o := by
rcases zero_or_succ_or_limit o with (rfl | ⟨o, rfl⟩ | l)
· simp [not_zero_isLimit, Cardinal.aleph0_ne_zero]
· simp [not_succ_isLimit, Cardinal.one_lt_aleph0]
· simp [l]
refine le_of_not_lt fun h => ?_
cases' Cardinal.lt_aleph0.1 h with n e
have := cof_cof o
rw [e, ord_nat] at this
cases n
· simp at e
simp [e, not_zero_isLimit] at l
· rw [natCast_succ, cof_succ] at this
rw [← this, cof_eq_one_iff_is_succ] at e
rcases e with ⟨a, rfl⟩
exact not_succ_isLimit _ l
#align ordinal.aleph_0_le_cof Ordinal.aleph0_le_cof
@[simp]
theorem aleph'_cof {o : Ordinal} (ho : o.IsLimit) : (aleph' o).ord.cof = o.cof :=
aleph'_isNormal.cof_eq ho
#align ordinal.aleph'_cof Ordinal.aleph'_cof
@[simp]
theorem aleph_cof {o : Ordinal} (ho : o.IsLimit) : (aleph o).ord.cof = o.cof :=
aleph_isNormal.cof_eq ho
#align ordinal.aleph_cof Ordinal.aleph_cof
@[simp]
theorem cof_omega : cof ω = ℵ₀ :=
(aleph0_le_cof.2 omega_isLimit).antisymm' <| by
rw [← card_omega]
apply cof_le_card
#align ordinal.cof_omega Ordinal.cof_omega
theorem cof_eq' (r : α → α → Prop) [IsWellOrder α r] (h : IsLimit (type r)) :
∃ S : Set α, (∀ a, ∃ b ∈ S, r a b) ∧ #S = cof (type r) :=
let ⟨S, H, e⟩ := cof_eq r
⟨S, fun a =>
let a' := enum r _ (h.2 _ (typein_lt_type r a))
let ⟨b, h, ab⟩ := H a'
⟨b, h,
(IsOrderConnected.conn a b a' <|
(typein_lt_typein r).1
(by
rw [typein_enum]
exact lt_succ (typein _ _))).resolve_right
ab⟩,
e⟩
#align ordinal.cof_eq' Ordinal.cof_eq'
@[simp]
theorem cof_univ : cof univ.{u, v} = Cardinal.univ.{u, v} :=
le_antisymm (cof_le_card _)
(by
refine le_of_forall_lt fun c h => ?_
rcases lt_univ'.1 h with ⟨c, rfl⟩
rcases @cof_eq Ordinal.{u} (· < ·) _ with ⟨S, H, Se⟩
rw [univ, ← lift_cof, ← Cardinal.lift_lift.{u+1, v, u}, Cardinal.lift_lt, ← Se]
refine lt_of_not_ge fun h => ?_
cases' Cardinal.lift_down h with a e
refine Quotient.inductionOn a (fun α e => ?_) e
cases' Quotient.exact e with f
have f := Equiv.ulift.symm.trans f
let g a := (f a).1
let o := succ (sup.{u, u} g)
rcases H o with ⟨b, h, l⟩
refine l (lt_succ_iff.2 ?_)
rw [← show g (f.symm ⟨b, h⟩) = b by simp [g]]
apply le_sup)
#align ordinal.cof_univ Ordinal.cof_univ
/-! ### Infinite pigeonhole principle -/
/-- If the union of s is unbounded and s is smaller than the cofinality,
then s has an unbounded member -/
theorem unbounded_of_unbounded_sUnion (r : α → α → Prop) [wo : IsWellOrder α r] {s : Set (Set α)}
(h₁ : Unbounded r <| ⋃₀ s) (h₂ : #s < StrictOrder.cof r) : ∃ x ∈ s, Unbounded r x := by
by_contra! h
simp_rw [not_unbounded_iff] at h
let f : s → α := fun x : s => wo.wf.sup x (h x.1 x.2)
refine h₂.not_le (le_trans (csInf_le' ⟨range f, fun x => ?_, rfl⟩) mk_range_le)
rcases h₁ x with ⟨y, ⟨c, hc, hy⟩, hxy⟩
exact ⟨f ⟨c, hc⟩, mem_range_self _, fun hxz => hxy (Trans.trans (wo.wf.lt_sup _ hy) hxz)⟩
#align ordinal.unbounded_of_unbounded_sUnion Ordinal.unbounded_of_unbounded_sUnion
/-- If the union of s is unbounded and s is smaller than the cofinality,
then s has an unbounded member -/
theorem unbounded_of_unbounded_iUnion {α β : Type u} (r : α → α → Prop) [wo : IsWellOrder α r]
(s : β → Set α) (h₁ : Unbounded r <| ⋃ x, s x) (h₂ : #β < StrictOrder.cof r) :
∃ x : β, Unbounded r (s x) := by
rw [← sUnion_range] at h₁
rcases unbounded_of_unbounded_sUnion r h₁ (mk_range_le.trans_lt h₂) with ⟨_, ⟨x, rfl⟩, u⟩
exact ⟨x, u⟩
#align ordinal.unbounded_of_unbounded_Union Ordinal.unbounded_of_unbounded_iUnion
/-- The infinite pigeonhole principle -/
theorem infinite_pigeonhole {β α : Type u} (f : β → α) (h₁ : ℵ₀ ≤ #β) (h₂ : #α < (#β).ord.cof) :
∃ a : α, #(f ⁻¹' {a}) = #β := by
have : ∃ a, #β ≤ #(f ⁻¹' {a}) := by
by_contra! h
apply mk_univ.not_lt
rw [← preimage_univ, ← iUnion_of_singleton, preimage_iUnion]
exact
mk_iUnion_le_sum_mk.trans_lt
((sum_le_iSup _).trans_lt <| mul_lt_of_lt h₁ (h₂.trans_le <| cof_ord_le _) (iSup_lt h₂ h))
cases' this with x h
refine ⟨x, h.antisymm' ?_⟩
rw [le_mk_iff_exists_set]
exact ⟨_, rfl⟩
#align ordinal.infinite_pigeonhole Ordinal.infinite_pigeonhole
/-- Pigeonhole principle for a cardinality below the cardinality of the domain -/
theorem infinite_pigeonhole_card {β α : Type u} (f : β → α) (θ : Cardinal) (hθ : θ ≤ #β)
(h₁ : ℵ₀ ≤ θ) (h₂ : #α < θ.ord.cof) : ∃ a : α, θ ≤ #(f ⁻¹' {a}) := by
rcases le_mk_iff_exists_set.1 hθ with ⟨s, rfl⟩
cases' infinite_pigeonhole (f ∘ Subtype.val : s → α) h₁ h₂ with a ha
use a; rw [← ha, @preimage_comp _ _ _ Subtype.val f]
exact mk_preimage_of_injective _ _ Subtype.val_injective
#align ordinal.infinite_pigeonhole_card Ordinal.infinite_pigeonhole_card
theorem infinite_pigeonhole_set {β α : Type u} {s : Set β} (f : s → α) (θ : Cardinal)
(hθ : θ ≤ #s) (h₁ : ℵ₀ ≤ θ) (h₂ : #α < θ.ord.cof) :
∃ (a : α) (t : Set β) (h : t ⊆ s), θ ≤ #t ∧ ∀ ⦃x⦄ (hx : x ∈ t), f ⟨x, h hx⟩ = a := by
cases' infinite_pigeonhole_card f θ hθ h₁ h₂ with a ha
refine ⟨a, { x | ∃ h, f ⟨x, h⟩ = a }, ?_, ?_, ?_⟩
· rintro x ⟨hx, _⟩
exact hx
· refine
ha.trans
(ge_of_eq <|
Quotient.sound ⟨Equiv.trans ?_ (Equiv.subtypeSubtypeEquivSubtypeExists _ _).symm⟩)
simp only [coe_eq_subtype, mem_singleton_iff, mem_preimage, mem_setOf_eq]
rfl
rintro x ⟨_, hx'⟩; exact hx'
#align ordinal.infinite_pigeonhole_set Ordinal.infinite_pigeonhole_set
end Ordinal
/-! ### Regular and inaccessible cardinals -/
namespace Cardinal
open Ordinal
/-- A cardinal is a strong limit if it is not zero and it is
closed under powersets. Note that `ℵ₀` is a strong limit by this definition. -/
def IsStrongLimit (c : Cardinal) : Prop :=
c ≠ 0 ∧ ∀ x < c, (2^x) < c
#align cardinal.is_strong_limit Cardinal.IsStrongLimit
theorem IsStrongLimit.ne_zero {c} (h : IsStrongLimit c) : c ≠ 0 :=
h.1
#align cardinal.is_strong_limit.ne_zero Cardinal.IsStrongLimit.ne_zero
theorem IsStrongLimit.two_power_lt {x c} (h : IsStrongLimit c) : x < c → (2^x) < c :=
h.2 x
#align cardinal.is_strong_limit.two_power_lt Cardinal.IsStrongLimit.two_power_lt
theorem isStrongLimit_aleph0 : IsStrongLimit ℵ₀ :=
⟨aleph0_ne_zero, fun x hx => by
rcases lt_aleph0.1 hx with ⟨n, rfl⟩
exact mod_cast nat_lt_aleph0 (2 ^ n)⟩
#align cardinal.is_strong_limit_aleph_0 Cardinal.isStrongLimit_aleph0
protected theorem IsStrongLimit.isSuccLimit {c} (H : IsStrongLimit c) : IsSuccLimit c :=
isSuccLimit_of_succ_lt fun x h => (succ_le_of_lt <| cantor x).trans_lt (H.two_power_lt h)
#align cardinal.is_strong_limit.is_succ_limit Cardinal.IsStrongLimit.isSuccLimit
theorem IsStrongLimit.isLimit {c} (H : IsStrongLimit c) : IsLimit c :=
⟨H.ne_zero, H.isSuccLimit⟩
#align cardinal.is_strong_limit.is_limit Cardinal.IsStrongLimit.isLimit
theorem isStrongLimit_beth {o : Ordinal} (H : IsSuccLimit o) : IsStrongLimit (beth o) := by
rcases eq_or_ne o 0 with (rfl | h)
· rw [beth_zero]
exact isStrongLimit_aleph0
· refine ⟨beth_ne_zero o, fun a ha => ?_⟩
rw [beth_limit ⟨h, isSuccLimit_iff_succ_lt.1 H⟩] at ha
rcases exists_lt_of_lt_ciSup' ha with ⟨⟨i, hi⟩, ha⟩
have := power_le_power_left two_ne_zero ha.le
rw [← beth_succ] at this
exact this.trans_lt (beth_lt.2 (H.succ_lt hi))
#align cardinal.is_strong_limit_beth Cardinal.isStrongLimit_beth
theorem mk_bounded_subset {α : Type*} (h : ∀ x < #α, (2^x) < #α) {r : α → α → Prop}
[IsWellOrder α r] (hr : (#α).ord = type r) : #{ s : Set α // Bounded r s } = #α := by
rcases eq_or_ne #α 0 with (ha | ha)
· rw [ha]
haveI := mk_eq_zero_iff.1 ha
rw [mk_eq_zero_iff]
constructor
rintro ⟨s, hs⟩
exact (not_unbounded_iff s).2 hs (unbounded_of_isEmpty s)
have h' : IsStrongLimit #α := ⟨ha, h⟩
have ha := h'.isLimit.aleph0_le
apply le_antisymm
· have : { s : Set α | Bounded r s } = ⋃ i, 𝒫{ j | r j i } := setOf_exists _
rw [← coe_setOf, this]
refine mk_iUnion_le_sum_mk.trans ((sum_le_iSup (fun i => #(𝒫{ j | r j i }))).trans
((mul_le_max_of_aleph0_le_left ha).trans ?_))
rw [max_eq_left]
apply ciSup_le' _
intro i
rw [mk_powerset]
apply (h'.two_power_lt _).le
rw [coe_setOf, card_typein, ← lt_ord, hr]
apply typein_lt_type
· refine @mk_le_of_injective α _ (fun x => Subtype.mk {x} ?_) ?_
· apply bounded_singleton
rw [← hr]
apply ord_isLimit ha
· intro a b hab
simpa [singleton_eq_singleton_iff] using hab
#align cardinal.mk_bounded_subset Cardinal.mk_bounded_subset
theorem mk_subset_mk_lt_cof {α : Type*} (h : ∀ x < #α, (2^x) < #α) :
#{ s : Set α // #s < cof (#α).ord } = #α := by
rcases eq_or_ne #α 0 with (ha | ha)
· simp [ha]
have h' : IsStrongLimit #α := ⟨ha, h⟩
rcases ord_eq α with ⟨r, wo, hr⟩
haveI := wo
apply le_antisymm
· conv_rhs => rw [← mk_bounded_subset h hr]
apply mk_le_mk_of_subset
intro s hs
rw [hr] at hs
exact lt_cof_type hs
· refine @mk_le_of_injective α _ (fun x => Subtype.mk {x} ?_) ?_
· rw [mk_singleton]
exact one_lt_aleph0.trans_le (aleph0_le_cof.2 (ord_isLimit h'.isLimit.aleph0_le))
· intro a b hab
simpa [singleton_eq_singleton_iff] using hab
#align cardinal.mk_subset_mk_lt_cof Cardinal.mk_subset_mk_lt_cof
/-- A cardinal is regular if it is infinite and it equals its own cofinality. -/
def IsRegular (c : Cardinal) : Prop :=
ℵ₀ ≤ c ∧ c ≤ c.ord.cof
#align cardinal.is_regular Cardinal.IsRegular
theorem IsRegular.aleph0_le {c : Cardinal} (H : c.IsRegular) : ℵ₀ ≤ c :=
H.1
#align cardinal.is_regular.aleph_0_le Cardinal.IsRegular.aleph0_le
theorem IsRegular.cof_eq {c : Cardinal} (H : c.IsRegular) : c.ord.cof = c :=
(cof_ord_le c).antisymm H.2
#align cardinal.is_regular.cof_eq Cardinal.IsRegular.cof_eq
theorem IsRegular.pos {c : Cardinal} (H : c.IsRegular) : 0 < c :=
aleph0_pos.trans_le H.1
#align cardinal.is_regular.pos Cardinal.IsRegular.pos
theorem IsRegular.nat_lt {c : Cardinal} (H : c.IsRegular) (n : ℕ) : n < c :=
lt_of_lt_of_le (nat_lt_aleph0 n) H.aleph0_le
theorem IsRegular.ord_pos {c : Cardinal} (H : c.IsRegular) : 0 < c.ord := by
rw [Cardinal.lt_ord, card_zero]
exact H.pos
#align cardinal.is_regular.ord_pos Cardinal.IsRegular.ord_pos
theorem isRegular_cof {o : Ordinal} (h : o.IsLimit) : IsRegular o.cof :=
⟨aleph0_le_cof.2 h, (cof_cof o).ge⟩
#align cardinal.is_regular_cof Cardinal.isRegular_cof
theorem isRegular_aleph0 : IsRegular ℵ₀ :=
⟨le_rfl, by simp⟩
#align cardinal.is_regular_aleph_0 Cardinal.isRegular_aleph0
theorem isRegular_succ {c : Cardinal.{u}} (h : ℵ₀ ≤ c) : IsRegular (succ c) :=
⟨h.trans (le_succ c),
succ_le_of_lt
(by
cases' Quotient.exists_rep (@succ Cardinal _ _ c) with α αe; simp at αe
rcases ord_eq α with ⟨r, wo, re⟩
have := ord_isLimit (h.trans (le_succ _))
rw [← αe, re] at this ⊢
rcases cof_eq' r this with ⟨S, H, Se⟩
rw [← Se]
apply lt_imp_lt_of_le_imp_le fun h => mul_le_mul_right' h c
rw [mul_eq_self h, ← succ_le_iff, ← αe, ← sum_const']
refine le_trans ?_ (sum_le_sum (fun (x : S) => card (typein r (x : α))) _ fun i => ?_)
· simp only [← card_typein, ← mk_sigma]
exact
⟨Embedding.ofSurjective (fun x => x.2.1) fun a =>
let ⟨b, h, ab⟩ := H a
⟨⟨⟨_, h⟩, _, ab⟩, rfl⟩⟩
· rw [← lt_succ_iff, ← lt_ord, ← αe, re]
apply typein_lt_type)⟩
#align cardinal.is_regular_succ Cardinal.isRegular_succ
theorem isRegular_aleph_one : IsRegular (aleph 1) := by
rw [← succ_aleph0]
exact isRegular_succ le_rfl
#align cardinal.is_regular_aleph_one Cardinal.isRegular_aleph_one
theorem isRegular_aleph'_succ {o : Ordinal} (h : ω ≤ o) : IsRegular (aleph' (succ o)) := by
rw [aleph'_succ]
exact isRegular_succ (aleph0_le_aleph'.2 h)
#align cardinal.is_regular_aleph'_succ Cardinal.isRegular_aleph'_succ
theorem isRegular_aleph_succ (o : Ordinal) : IsRegular (aleph (succ o)) := by
rw [aleph_succ]
exact isRegular_succ (aleph0_le_aleph o)
#align cardinal.is_regular_aleph_succ Cardinal.isRegular_aleph_succ
/-- A function whose codomain's cardinality is infinite but strictly smaller than its domain's
has a fiber with cardinality strictly great than the codomain.
-/
theorem infinite_pigeonhole_card_lt {β α : Type u} (f : β → α) (w : #α < #β) (w' : ℵ₀ ≤ #α) :
∃ a : α, #α < #(f ⁻¹' {a}) := by
simp_rw [← succ_le_iff]
exact
Ordinal.infinite_pigeonhole_card f (succ #α) (succ_le_of_lt w) (w'.trans (lt_succ _).le)
((lt_succ _).trans_le (isRegular_succ w').2.ge)
#align cardinal.infinite_pigeonhole_card_lt Cardinal.infinite_pigeonhole_card_lt
/-- A function whose codomain's cardinality is infinite but strictly smaller than its domain's
has an infinite fiber.
-/
theorem exists_infinite_fiber {β α : Type u} (f : β → α) (w : #α < #β) (w' : Infinite α) :
∃ a : α, Infinite (f ⁻¹' {a}) := by
simp_rw [Cardinal.infinite_iff] at w' ⊢
cases' infinite_pigeonhole_card_lt f w w' with a ha
exact ⟨a, w'.trans ha.le⟩
#align cardinal.exists_infinite_fiber Cardinal.exists_infinite_fiber
/-- If an infinite type `β` can be expressed as a union of finite sets,
then the cardinality of the collection of those finite sets
must be at least the cardinality of `β`.
-/
theorem le_range_of_union_finset_eq_top {α β : Type*} [Infinite β] (f : α → Finset β)
(w : ⋃ a, (f a : Set β) = ⊤) : #β ≤ #(range f) := by
have k : _root_.Infinite (range f) := by
rw [infinite_coe_iff]
apply mt (union_finset_finite_of_range_finite f)
rw [w]
exact infinite_univ
by_contra h
simp only [not_le] at h
let u : ∀ b, ∃ a, b ∈ f a := fun b => by simpa using (w.ge : _) (Set.mem_univ b)
let u' : β → range f := fun b => ⟨f (u b).choose, by simp⟩
have v' : ∀ a, u' ⁻¹' {⟨f a, by simp⟩} ≤ f a := by
rintro a p m
simp? [u'] at m says simp only [mem_preimage, mem_singleton_iff, Subtype.mk.injEq, u'] at m
rw [← m]
apply fun b => (u b).choose_spec
obtain ⟨⟨-, ⟨a, rfl⟩⟩, p⟩ := exists_infinite_fiber u' h k
exact (@Infinite.of_injective _ _ p (inclusion (v' a)) (inclusion_injective _)).false
#align cardinal.le_range_of_union_finset_eq_top Cardinal.le_range_of_union_finset_eq_top
theorem lsub_lt_ord_lift_of_isRegular {ι} {f : ι → Ordinal} {c} (hc : IsRegular c)
(hι : Cardinal.lift.{v, u} #ι < c) : (∀ i, f i < c.ord) → Ordinal.lsub.{u, v} f < c.ord :=
lsub_lt_ord_lift (by rwa [hc.cof_eq])
#align cardinal.lsub_lt_ord_lift_of_is_regular Cardinal.lsub_lt_ord_lift_of_isRegular
theorem lsub_lt_ord_of_isRegular {ι} {f : ι → Ordinal} {c} (hc : IsRegular c) (hι : #ι < c) :
(∀ i, f i < c.ord) → Ordinal.lsub f < c.ord :=
lsub_lt_ord (by rwa [hc.cof_eq])
#align cardinal.lsub_lt_ord_of_is_regular Cardinal.lsub_lt_ord_of_isRegular
theorem sup_lt_ord_lift_of_isRegular {ι} {f : ι → Ordinal} {c} (hc : IsRegular c)
(hι : Cardinal.lift.{v, u} #ι < c) : (∀ i, f i < c.ord) → Ordinal.sup.{u, v} f < c.ord :=
sup_lt_ord_lift (by rwa [hc.cof_eq])
#align cardinal.sup_lt_ord_lift_of_is_regular Cardinal.sup_lt_ord_lift_of_isRegular
theorem sup_lt_ord_of_isRegular {ι} {f : ι → Ordinal} {c} (hc : IsRegular c) (hι : #ι < c) :
(∀ i, f i < c.ord) → Ordinal.sup f < c.ord :=
sup_lt_ord (by rwa [hc.cof_eq])
#align cardinal.sup_lt_ord_of_is_regular Cardinal.sup_lt_ord_of_isRegular
theorem blsub_lt_ord_lift_of_isRegular {o : Ordinal} {f : ∀ a < o, Ordinal} {c} (hc : IsRegular c)
(ho : Cardinal.lift.{v, u} o.card < c) :
(∀ i hi, f i hi < c.ord) → Ordinal.blsub.{u, v} o f < c.ord :=
blsub_lt_ord_lift (by rwa [hc.cof_eq])
#align cardinal.blsub_lt_ord_lift_of_is_regular Cardinal.blsub_lt_ord_lift_of_isRegular
theorem blsub_lt_ord_of_isRegular {o : Ordinal} {f : ∀ a < o, Ordinal} {c} (hc : IsRegular c)
(ho : o.card < c) : (∀ i hi, f i hi < c.ord) → Ordinal.blsub o f < c.ord :=
blsub_lt_ord (by rwa [hc.cof_eq])
#align cardinal.blsub_lt_ord_of_is_regular Cardinal.blsub_lt_ord_of_isRegular
theorem bsup_lt_ord_lift_of_isRegular {o : Ordinal} {f : ∀ a < o, Ordinal} {c} (hc : IsRegular c)
(hι : Cardinal.lift.{v, u} o.card < c) :
(∀ i hi, f i hi < c.ord) → Ordinal.bsup.{u, v} o f < c.ord :=
bsup_lt_ord_lift (by rwa [hc.cof_eq])
#align cardinal.bsup_lt_ord_lift_of_is_regular Cardinal.bsup_lt_ord_lift_of_isRegular
theorem bsup_lt_ord_of_isRegular {o : Ordinal} {f : ∀ a < o, Ordinal} {c} (hc : IsRegular c)
(hι : o.card < c) : (∀ i hi, f i hi < c.ord) → Ordinal.bsup o f < c.ord :=
bsup_lt_ord (by rwa [hc.cof_eq])
#align cardinal.bsup_lt_ord_of_is_regular Cardinal.bsup_lt_ord_of_isRegular
theorem iSup_lt_lift_of_isRegular {ι} {f : ι → Cardinal} {c} (hc : IsRegular c)
(hι : Cardinal.lift.{v, u} #ι < c) : (∀ i, f i < c) → iSup.{max u v + 1, u + 1} f < c :=
iSup_lt_lift.{u, v} (by rwa [hc.cof_eq])
#align cardinal.supr_lt_lift_of_is_regular Cardinal.iSup_lt_lift_of_isRegular
theorem iSup_lt_of_isRegular {ι} {f : ι → Cardinal} {c} (hc : IsRegular c) (hι : #ι < c) :
(∀ i, f i < c) → iSup f < c :=
iSup_lt (by rwa [hc.cof_eq])
#align cardinal.supr_lt_of_is_regular Cardinal.iSup_lt_of_isRegular
theorem sum_lt_lift_of_isRegular {ι : Type u} {f : ι → Cardinal} {c : Cardinal} (hc : IsRegular c)
(hι : Cardinal.lift.{v, u} #ι < c) (hf : ∀ i, f i < c) : sum f < c :=
(sum_le_iSup_lift _).trans_lt <| mul_lt_of_lt hc.1 hι (iSup_lt_lift_of_isRegular hc hι hf)
#align cardinal.sum_lt_lift_of_is_regular Cardinal.sum_lt_lift_of_isRegular
theorem sum_lt_of_isRegular {ι : Type u} {f : ι → Cardinal} {c : Cardinal} (hc : IsRegular c)
(hι : #ι < c) : (∀ i, f i < c) → sum f < c :=
sum_lt_lift_of_isRegular.{u, u} hc (by rwa [lift_id])
#align cardinal.sum_lt_of_is_regular Cardinal.sum_lt_of_isRegular
@[simp]
theorem card_lt_of_card_iUnion_lt {ι : Type u} {α : Type u} {t : ι → Set α} {c : Cardinal}
(h : #(⋃ i, t i) < c) (i : ι) : #(t i) < c :=
lt_of_le_of_lt (Cardinal.mk_le_mk_of_subset <| subset_iUnion _ _) h
@[simp]
theorem card_iUnion_lt_iff_forall_of_isRegular {ι : Type u} {α : Type u} {t : ι → Set α}
{c : Cardinal} (hc : c.IsRegular) (hι : #ι < c) : #(⋃ i, t i) < c ↔ ∀ i, #(t i) < c := by
refine ⟨card_lt_of_card_iUnion_lt, fun h ↦ ?_⟩
apply lt_of_le_of_lt (Cardinal.mk_sUnion_le _)
apply Cardinal.mul_lt_of_lt hc.aleph0_le
(lt_of_le_of_lt Cardinal.mk_range_le hι)
apply Cardinal.iSup_lt_of_isRegular hc (lt_of_le_of_lt Cardinal.mk_range_le hι)
simpa
theorem card_lt_of_card_biUnion_lt {α β : Type u} {s : Set α} {t : ∀ a ∈ s, Set β} {c : Cardinal}
(h : #(⋃ a ∈ s, t a ‹_›) < c) (a : α) (ha : a ∈ s) : # (t a ha) < c := by
rw [biUnion_eq_iUnion] at h
have := card_lt_of_card_iUnion_lt h
simp_all only [iUnion_coe_set,
Subtype.forall]
theorem card_biUnion_lt_iff_forall_of_isRegular {α β : Type u} {s : Set α} {t : ∀ a ∈ s, Set β}
{c : Cardinal} (hc : c.IsRegular) (hs : #s < c) :
#(⋃ a ∈ s, t a ‹_›) < c ↔ ∀ a (ha : a ∈ s), # (t a ha) < c := by
rw [biUnion_eq_iUnion, card_iUnion_lt_iff_forall_of_isRegular hc hs, SetCoe.forall']
theorem nfpFamily_lt_ord_lift_of_isRegular {ι} {f : ι → Ordinal → Ordinal} {c} (hc : IsRegular c)
(hι : Cardinal.lift.{v, u} #ι < c) (hc' : c ≠ ℵ₀) (hf : ∀ (i), ∀ b < c.ord, f i b < c.ord) {a}
(ha : a < c.ord) : nfpFamily.{u, v} f a < c.ord := by
apply nfpFamily_lt_ord_lift.{u, v} _ _ hf ha <;> rw [hc.cof_eq]
· exact lt_of_le_of_ne hc.1 hc'.symm
· exact hι
#align cardinal.nfp_family_lt_ord_lift_of_is_regular Cardinal.nfpFamily_lt_ord_lift_of_isRegular
theorem nfpFamily_lt_ord_of_isRegular {ι} {f : ι → Ordinal → Ordinal} {c} (hc : IsRegular c)
(hι : #ι < c) (hc' : c ≠ ℵ₀) {a} (hf : ∀ (i), ∀ b < c.ord, f i b < c.ord) :
a < c.ord → nfpFamily.{u, u} f a < c.ord :=
nfpFamily_lt_ord_lift_of_isRegular hc (by rwa [lift_id]) hc' hf
#align cardinal.nfp_family_lt_ord_of_is_regular Cardinal.nfpFamily_lt_ord_of_isRegular
theorem nfpBFamily_lt_ord_lift_of_isRegular {o : Ordinal} {f : ∀ a < o, Ordinal → Ordinal} {c}
(hc : IsRegular c) (ho : Cardinal.lift.{v, u} o.card < c) (hc' : c ≠ ℵ₀)
(hf : ∀ (i hi), ∀ b < c.ord, f i hi b < c.ord) {a} :
a < c.ord → nfpBFamily.{u, v} o f a < c.ord :=
nfpFamily_lt_ord_lift_of_isRegular hc (by rwa [mk_ordinal_out]) hc' fun i => hf _ _
#align cardinal.nfp_bfamily_lt_ord_lift_of_is_regular Cardinal.nfpBFamily_lt_ord_lift_of_isRegular
theorem nfpBFamily_lt_ord_of_isRegular {o : Ordinal} {f : ∀ a < o, Ordinal → Ordinal} {c}
(hc : IsRegular c) (ho : o.card < c) (hc' : c ≠ ℵ₀)
(hf : ∀ (i hi), ∀ b < c.ord, f i hi b < c.ord) {a} :
a < c.ord → nfpBFamily.{u, u} o f a < c.ord :=
nfpBFamily_lt_ord_lift_of_isRegular hc (by rwa [lift_id]) hc' hf
#align cardinal.nfp_bfamily_lt_ord_of_is_regular Cardinal.nfpBFamily_lt_ord_of_isRegular
theorem nfp_lt_ord_of_isRegular {f : Ordinal → Ordinal} {c} (hc : IsRegular c) (hc' : c ≠ ℵ₀)
(hf : ∀ i < c.ord, f i < c.ord) {a} : a < c.ord → nfp f a < c.ord :=
nfp_lt_ord
(by
rw [hc.cof_eq]
exact lt_of_le_of_ne hc.1 hc'.symm)
hf
#align cardinal.nfp_lt_ord_of_is_regular Cardinal.nfp_lt_ord_of_isRegular
theorem derivFamily_lt_ord_lift {ι} {f : ι → Ordinal → Ordinal} {c} (hc : IsRegular c)
(hι : Cardinal.lift.{v, u} #ι < c) (hc' : c ≠ ℵ₀)
(hf : ∀ (i), ∀ b < c.ord, f i b < c.ord) {a} :
a < c.ord → derivFamily.{u, v} f a < c.ord := by
have hω : ℵ₀ < c.ord.cof := by
rw [hc.cof_eq]
exact lt_of_le_of_ne hc.1 hc'.symm
induction a using limitRecOn with
| H₁ =>
rw [derivFamily_zero]
exact nfpFamily_lt_ord_lift hω (by rwa [hc.cof_eq]) hf
| H₂ b hb =>
intro hb'
rw [derivFamily_succ]
exact
nfpFamily_lt_ord_lift hω (by rwa [hc.cof_eq]) hf
((ord_isLimit hc.1).2 _ (hb ((lt_succ b).trans hb')))
| H₃ b hb H =>
intro hb'
rw [derivFamily_limit f hb]
exact
bsup_lt_ord_of_isRegular.{u, v} hc (ord_lt_ord.1 ((ord_card_le b).trans_lt hb')) fun o' ho' =>
H o' ho' (ho'.trans hb')
#align cardinal.deriv_family_lt_ord_lift Cardinal.derivFamily_lt_ord_lift
theorem derivFamily_lt_ord {ι} {f : ι → Ordinal → Ordinal} {c} (hc : IsRegular c) (hι : #ι < c)
(hc' : c ≠ ℵ₀) (hf : ∀ (i), ∀ b < c.ord, f i b < c.ord) {a} :
a < c.ord → derivFamily.{u, u} f a < c.ord :=
derivFamily_lt_ord_lift hc (by rwa [lift_id]) hc' hf
#align cardinal.deriv_family_lt_ord Cardinal.derivFamily_lt_ord
theorem derivBFamily_lt_ord_lift {o : Ordinal} {f : ∀ a < o, Ordinal → Ordinal} {c}
(hc : IsRegular c) (hι : Cardinal.lift.{v, u} o.card < c) (hc' : c ≠ ℵ₀)
(hf : ∀ (i hi), ∀ b < c.ord, f i hi b < c.ord) {a} :
a < c.ord → derivBFamily.{u, v} o f a < c.ord :=
derivFamily_lt_ord_lift hc (by rwa [mk_ordinal_out]) hc' fun i => hf _ _
#align cardinal.deriv_bfamily_lt_ord_lift Cardinal.derivBFamily_lt_ord_lift
theorem derivBFamily_lt_ord {o : Ordinal} {f : ∀ a < o, Ordinal → Ordinal} {c} (hc : IsRegular c)
(hι : o.card < c) (hc' : c ≠ ℵ₀) (hf : ∀ (i hi), ∀ b < c.ord, f i hi b < c.ord) {a} :
a < c.ord → derivBFamily.{u, u} o f a < c.ord :=
derivBFamily_lt_ord_lift hc (by rwa [lift_id]) hc' hf
#align cardinal.deriv_bfamily_lt_ord Cardinal.derivBFamily_lt_ord
theorem deriv_lt_ord {f : Ordinal.{u} → Ordinal} {c} (hc : IsRegular c) (hc' : c ≠ ℵ₀)
(hf : ∀ i < c.ord, f i < c.ord) {a} : a < c.ord → deriv f a < c.ord :=
derivFamily_lt_ord_lift hc
(by simpa using Cardinal.one_lt_aleph0.trans (lt_of_le_of_ne hc.1 hc'.symm)) hc' fun _ => hf
#align cardinal.deriv_lt_ord Cardinal.deriv_lt_ord
/-- A cardinal is inaccessible if it is an uncountable regular strong limit cardinal. -/
def IsInaccessible (c : Cardinal) :=
ℵ₀ < c ∧ IsRegular c ∧ IsStrongLimit c
#align cardinal.is_inaccessible Cardinal.IsInaccessible
theorem IsInaccessible.mk {c} (h₁ : ℵ₀ < c) (h₂ : c ≤ c.ord.cof) (h₃ : ∀ x < c, (2^x) < c) :
IsInaccessible c :=
⟨h₁, ⟨h₁.le, h₂⟩, (aleph0_pos.trans h₁).ne', h₃⟩
#align cardinal.is_inaccessible.mk Cardinal.IsInaccessible.mk
-- Lean's foundations prove the existence of ℵ₀ many inaccessible cardinals
theorem univ_inaccessible : IsInaccessible univ.{u, v} :=
IsInaccessible.mk (by simpa using lift_lt_univ' ℵ₀) (by simp) fun c h => by
rcases lt_univ'.1 h with ⟨c, rfl⟩
rw [← lift_two_power.{u, max (u + 1) v}]
apply lift_lt_univ'
#align cardinal.univ_inaccessible Cardinal.univ_inaccessible
theorem lt_power_cof {c : Cardinal.{u}} : ℵ₀ ≤ c → c < (c^cof c.ord) :=
Quotient.inductionOn c fun α h => by
rcases ord_eq α with ⟨r, wo, re⟩
have := ord_isLimit h
rw [mk'_def, re] at this ⊢
rcases cof_eq' r this with ⟨S, H, Se⟩
have := sum_lt_prod (fun a : S => #{ x // r x a }) (fun _ => #α) fun i => ?_
· simp only [Cardinal.prod_const, Cardinal.lift_id, ← Se, ← mk_sigma, power_def] at this ⊢
refine lt_of_le_of_lt ?_ this
refine ⟨Embedding.ofSurjective ?_ ?_⟩
· exact fun x => x.2.1
· exact fun a =>
let ⟨b, h, ab⟩ := H a
⟨⟨⟨_, h⟩, _, ab⟩, rfl⟩
· have := typein_lt_type r i
rwa [← re, lt_ord] at this
#align cardinal.lt_power_cof Cardinal.lt_power_cof
| Mathlib/SetTheory/Cardinal/Cofinality.lean | 1,269 | 1,273 | theorem lt_cof_power {a b : Cardinal} (ha : ℵ₀ ≤ a) (b1 : 1 < b) : a < cof (b^a).ord := by |
have b0 : b ≠ 0 := (zero_lt_one.trans b1).ne'
apply lt_imp_lt_of_le_imp_le (power_le_power_left <| power_ne_zero a b0)
rw [← power_mul, mul_eq_self ha]
exact lt_power_cof (ha.trans <| (cantor' _ b1).le)
|
/-
Copyright (c) 2022 Junyan Xu. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Junyan Xu
-/
import Mathlib.Data.DFinsupp.Lex
import Mathlib.Order.GameAdd
import Mathlib.Order.Antisymmetrization
import Mathlib.SetTheory.Ordinal.Basic
import Mathlib.Tactic.AdaptationNote
#align_import data.dfinsupp.well_founded from "leanprover-community/mathlib"@"e9b8651eb1ad354f4de6be35a38ef31efcd2cfaa"
/-!
# Well-foundedness of the lexicographic and product orders on `DFinsupp` and `Pi`
The primary results are `DFinsupp.Lex.wellFounded` and the two variants that follow it,
which essentially say that if `(· > ·)` is a well order on `ι`, `(· < ·)` is well-founded on each
`α i`, and `0` is a bottom element in `α i`, then the lexicographic `(· < ·)` is well-founded
on `Π₀ i, α i`. The proof is modelled on the proof of `WellFounded.cutExpand`.
The results are used to prove `Pi.Lex.wellFounded` and two variants, which say that if
`ι` is finite and equipped with a linear order and `(· < ·)` is well-founded on each `α i`,
then the lexicographic `(· < ·)` is well-founded on `Π i, α i`, and the same is true for
`Π₀ i, α i` (`DFinsupp.Lex.wellFounded_of_finite`), because `DFinsupp` is order-isomorphic
to `pi` when `ι` is finite.
Finally, we deduce `DFinsupp.wellFoundedLT`, `Pi.wellFoundedLT`,
`DFinsupp.wellFoundedLT_of_finite` and variants, which concern the product order
rather than the lexicographic one. An order on `ι` is not required in these results,
but we deduce them from the well-foundedness of the lexicographic order by choosing
a well order on `ι` so that the product order `(· < ·)` becomes a subrelation
of the lexicographic `(· < ·)`.
All results are provided in two forms whenever possible: a general form where the relations
can be arbitrary (not the `(· < ·)` of a preorder, or not even transitive, etc.) and a specialized
form provided as `WellFoundedLT` instances where the `(d)Finsupp/pi` type (or their `Lex`
type synonyms) carries a natural `(· < ·)`.
Notice that the definition of `DFinsupp.Lex` says that `x < y` according to `DFinsupp.Lex r s`
iff there exists a coordinate `i : ι` such that `x i < y i` according to `s i`, and at all
`r`-smaller coordinates `j` (i.e. satisfying `r j i`), `x` remains unchanged relative to `y`;
in other words, coordinates `j` such that `¬ r j i` and `j ≠ i` are exactly where changes
can happen arbitrarily. This explains the appearance of `rᶜ ⊓ (≠)` in
`dfinsupp.acc_single` and `dfinsupp.well_founded`. When `r` is trichotomous (e.g. the `(· < ·)`
of a linear order), `¬ r j i ∧ j ≠ i` implies `r i j`, so it suffices to require `r.swap`
to be well-founded.
-/
variable {ι : Type*} {α : ι → Type*}
namespace DFinsupp
open Relation Prod
section Zero
variable [∀ i, Zero (α i)] (r : ι → ι → Prop) (s : ∀ i, α i → α i → Prop)
/-- This key lemma says that if a finitely supported dependent function `x₀` is obtained by merging
two such functions `x₁` and `x₂`, and if we evolve `x₀` down the `DFinsupp.Lex` relation one
step and get `x`, we can always evolve one of `x₁` and `x₂` down the `DFinsupp.Lex` relation
one step while keeping the other unchanged, and merge them back (possibly in a different way)
to get back `x`. In other words, the two parts evolve essentially independently under
`DFinsupp.Lex`. This is used to show that a function `x` is accessible if
`DFinsupp.single i (x i)` is accessible for each `i` in the (finite) support of `x`
(`DFinsupp.Lex.acc_of_single`). -/
| Mathlib/Data/DFinsupp/WellFounded.lean | 69 | 98 | theorem lex_fibration [∀ (i) (s : Set ι), Decidable (i ∈ s)] :
Fibration (InvImage (GameAdd (DFinsupp.Lex r s) (DFinsupp.Lex r s)) snd) (DFinsupp.Lex r s)
fun x => piecewise x.2.1 x.2.2 x.1 := by |
rintro ⟨p, x₁, x₂⟩ x ⟨i, hr, hs⟩
simp_rw [piecewise_apply] at hs hr
split_ifs at hs with hp
· refine ⟨⟨{ j | r j i → j ∈ p }, piecewise x₁ x { j | r j i }, x₂⟩,
.fst ⟨i, fun j hj ↦ ?_, ?_⟩, ?_⟩ <;> simp only [piecewise_apply, Set.mem_setOf_eq]
· simp only [if_pos hj]
· split_ifs with hi
· rwa [hr i hi, if_pos hp] at hs
· assumption
· ext1 j
simp only [piecewise_apply, Set.mem_setOf_eq]
split_ifs with h₁ h₂ <;> try rfl
· rw [hr j h₂, if_pos (h₁ h₂)]
· rw [Classical.not_imp] at h₁
rw [hr j h₁.1, if_neg h₁.2]
· refine ⟨⟨{ j | r j i ∧ j ∈ p }, x₁, piecewise x₂ x { j | r j i }⟩,
.snd ⟨i, fun j hj ↦ ?_, ?_⟩, ?_⟩ <;> simp only [piecewise_apply, Set.mem_setOf_eq]
· exact if_pos hj
· split_ifs with hi
· rwa [hr i hi, if_neg hp] at hs
· assumption
· ext1 j
simp only [piecewise_apply, Set.mem_setOf_eq]
split_ifs with h₁ h₂ <;> try rfl
· rw [hr j h₁.1, if_pos h₁.2]
· rw [hr j h₂, if_neg]
simpa [h₂] using h₁
|
/-
Copyright (c) 2020 Scott Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro, Scott Morrison, Ainsley Pahljina
-/
import Mathlib.Algebra.Order.Group.Basic
import Mathlib.Algebra.Order.Ring.Abs
import Mathlib.Algebra.Order.Ring.Basic
import Mathlib.Algebra.Ring.Nat
import Mathlib.Data.ZMod.Basic
import Mathlib.GroupTheory.OrderOfElement
import Mathlib.RingTheory.Fintype
import Mathlib.Tactic.IntervalCases
#align_import number_theory.lucas_lehmer from "leanprover-community/mathlib"@"10b4e499f43088dd3bb7b5796184ad5216648ab1"
/-!
# The Lucas-Lehmer test for Mersenne primes.
We define `lucasLehmerResidue : Π p : ℕ, ZMod (2^p - 1)`, and
prove `lucasLehmerResidue p = 0 → Prime (mersenne p)`.
We construct a `norm_num` extension to calculate this residue to certify primality of Mersenne
primes using `lucas_lehmer_sufficiency`.
## TODO
- Show reverse implication.
- Speed up the calculations using `n ≡ (n % 2^p) + (n / 2^p) [MOD 2^p - 1]`.
- Find some bigger primes!
## History
This development began as a student project by Ainsley Pahljina,
and was then cleaned up for mathlib by Scott Morrison.
The tactic for certified computation of Lucas-Lehmer residues was provided by Mario Carneiro.
This tactic was ported by Thomas Murrills to Lean 4, and then it was converted to a `norm_num`
extension and made to use kernel reductions by Kyle Miller.
-/
/-- The Mersenne numbers, 2^p - 1. -/
def mersenne (p : ℕ) : ℕ :=
2 ^ p - 1
#align mersenne mersenne
theorem strictMono_mersenne : StrictMono mersenne := fun m n h ↦
(Nat.sub_lt_sub_iff_right <| Nat.one_le_pow _ _ two_pos).2 <| by gcongr; norm_num1
@[simp]
theorem mersenne_lt_mersenne {p q : ℕ} : mersenne p < mersenne q ↔ p < q :=
strictMono_mersenne.lt_iff_lt
@[gcongr] protected alias ⟨_, GCongr.mersenne_lt_mersenne⟩ := mersenne_lt_mersenne
@[simp]
theorem mersenne_le_mersenne {p q : ℕ} : mersenne p ≤ mersenne q ↔ p ≤ q :=
strictMono_mersenne.le_iff_le
@[gcongr] protected alias ⟨_, GCongr.mersenne_le_mersenne⟩ := mersenne_le_mersenne
@[simp] theorem mersenne_zero : mersenne 0 = 0 := rfl
@[simp] theorem mersenne_pos {p : ℕ} : 0 < mersenne p ↔ 0 < p := mersenne_lt_mersenne (p := 0)
#align mersenne_pos mersenne_pos
namespace Mathlib.Meta.Positivity
open Lean Meta Qq Function
alias ⟨_, mersenne_pos_of_pos⟩ := mersenne_pos
/-- Extension for the `positivity` tactic: `mersenne`. -/
@[positivity mersenne _]
def evalMersenne : PositivityExt where eval {u α} _zα _pα e := do
match u, α, e with
| 0, ~q(ℕ), ~q(mersenne $a) =>
let ra ← core q(inferInstance) q(inferInstance) a
assertInstancesCommute
match ra with
| .positive pa => pure (.positive q(mersenne_pos_of_pos $pa))
| _ => pure (.nonnegative q(Nat.zero_le (mersenne $a)))
| _, _, _ => throwError "not mersenne"
end Mathlib.Meta.Positivity
@[simp]
theorem one_lt_mersenne {p : ℕ} : 1 < mersenne p ↔ 1 < p :=
mersenne_lt_mersenne (p := 1)
@[simp]
theorem succ_mersenne (k : ℕ) : mersenne k + 1 = 2 ^ k := by
rw [mersenne, tsub_add_cancel_of_le]
exact one_le_pow_of_one_le (by norm_num) k
#align succ_mersenne succ_mersenne
namespace LucasLehmer
open Nat
/-!
We now define three(!) different versions of the recurrence
`s (i+1) = (s i)^2 - 2`.
These versions take values either in `ℤ`, in `ZMod (2^p - 1)`, or
in `ℤ` but applying `% (2^p - 1)` at each step.
They are each useful at different points in the proof,
so we take a moment setting up the lemmas relating them.
-/
/-- The recurrence `s (i+1) = (s i)^2 - 2` in `ℤ`. -/
def s : ℕ → ℤ
| 0 => 4
| i + 1 => s i ^ 2 - 2
#align lucas_lehmer.s LucasLehmer.s
/-- The recurrence `s (i+1) = (s i)^2 - 2` in `ZMod (2^p - 1)`. -/
def sZMod (p : ℕ) : ℕ → ZMod (2 ^ p - 1)
| 0 => 4
| i + 1 => sZMod p i ^ 2 - 2
#align lucas_lehmer.s_zmod LucasLehmer.sZMod
/-- The recurrence `s (i+1) = ((s i)^2 - 2) % (2^p - 1)` in `ℤ`. -/
def sMod (p : ℕ) : ℕ → ℤ
| 0 => 4 % (2 ^ p - 1)
| i + 1 => (sMod p i ^ 2 - 2) % (2 ^ p - 1)
#align lucas_lehmer.s_mod LucasLehmer.sMod
theorem mersenne_int_pos {p : ℕ} (hp : p ≠ 0) : (0 : ℤ) < 2 ^ p - 1 :=
sub_pos.2 <| mod_cast Nat.one_lt_two_pow hp
theorem mersenne_int_ne_zero (p : ℕ) (hp : p ≠ 0) : (2 ^ p - 1 : ℤ) ≠ 0 :=
(mersenne_int_pos hp).ne'
#align lucas_lehmer.mersenne_int_ne_zero LucasLehmer.mersenne_int_ne_zero
theorem sMod_nonneg (p : ℕ) (hp : p ≠ 0) (i : ℕ) : 0 ≤ sMod p i := by
cases i <;> dsimp [sMod]
· exact sup_eq_right.mp rfl
· apply Int.emod_nonneg
exact mersenne_int_ne_zero p hp
#align lucas_lehmer.s_mod_nonneg LucasLehmer.sMod_nonneg
theorem sMod_mod (p i : ℕ) : sMod p i % (2 ^ p - 1) = sMod p i := by cases i <;> simp [sMod]
#align lucas_lehmer.s_mod_mod LucasLehmer.sMod_mod
theorem sMod_lt (p : ℕ) (hp : p ≠ 0) (i : ℕ) : sMod p i < 2 ^ p - 1 := by
rw [← sMod_mod]
refine (Int.emod_lt _ (mersenne_int_ne_zero p hp)).trans_eq ?_
exact abs_of_nonneg (mersenne_int_pos hp).le
#align lucas_lehmer.s_mod_lt LucasLehmer.sMod_lt
theorem sZMod_eq_s (p' : ℕ) (i : ℕ) : sZMod (p' + 2) i = (s i : ZMod (2 ^ (p' + 2) - 1)) := by
induction' i with i ih
· dsimp [s, sZMod]
norm_num
· push_cast [s, sZMod, ih]; rfl
#align lucas_lehmer.s_zmod_eq_s LucasLehmer.sZMod_eq_s
-- These next two don't make good `norm_cast` lemmas.
theorem Int.natCast_pow_pred (b p : ℕ) (w : 0 < b) : ((b ^ p - 1 : ℕ) : ℤ) = (b : ℤ) ^ p - 1 := by
have : 1 ≤ b ^ p := Nat.one_le_pow p b w
norm_cast
#align lucas_lehmer.int.coe_nat_pow_pred LucasLehmer.Int.natCast_pow_pred
@[deprecated (since := "2024-05-25")] alias Int.coe_nat_pow_pred := Int.natCast_pow_pred
theorem Int.coe_nat_two_pow_pred (p : ℕ) : ((2 ^ p - 1 : ℕ) : ℤ) = (2 ^ p - 1 : ℤ) :=
Int.natCast_pow_pred 2 p (by decide)
#align lucas_lehmer.int.coe_nat_two_pow_pred LucasLehmer.Int.coe_nat_two_pow_pred
theorem sZMod_eq_sMod (p : ℕ) (i : ℕ) : sZMod p i = (sMod p i : ZMod (2 ^ p - 1)) := by
induction i <;> push_cast [← Int.coe_nat_two_pow_pred p, sMod, sZMod, *] <;> rfl
#align lucas_lehmer.s_zmod_eq_s_mod LucasLehmer.sZMod_eq_sMod
/-- The Lucas-Lehmer residue is `s p (p-2)` in `ZMod (2^p - 1)`. -/
def lucasLehmerResidue (p : ℕ) : ZMod (2 ^ p - 1) :=
sZMod p (p - 2)
#align lucas_lehmer.lucas_lehmer_residue LucasLehmer.lucasLehmerResidue
theorem residue_eq_zero_iff_sMod_eq_zero (p : ℕ) (w : 1 < p) :
lucasLehmerResidue p = 0 ↔ sMod p (p - 2) = 0 := by
dsimp [lucasLehmerResidue]
rw [sZMod_eq_sMod p]
constructor
· -- We want to use that fact that `0 ≤ s_mod p (p-2) < 2^p - 1`
-- and `lucas_lehmer_residue p = 0 → 2^p - 1 ∣ s_mod p (p-2)`.
intro h
simp? [ZMod.intCast_zmod_eq_zero_iff_dvd] at h says
simp only [ZMod.intCast_zmod_eq_zero_iff_dvd, gt_iff_lt, ofNat_pos, pow_pos, cast_pred,
cast_pow, cast_ofNat] at h
apply Int.eq_zero_of_dvd_of_nonneg_of_lt _ _ h <;> clear h
· exact sMod_nonneg _ (by positivity) _
· exact sMod_lt _ (by positivity) _
· intro h
rw [h]
simp
#align lucas_lehmer.residue_eq_zero_iff_s_mod_eq_zero LucasLehmer.residue_eq_zero_iff_sMod_eq_zero
/-- **Lucas-Lehmer Test**: a Mersenne number `2^p-1` is prime if and only if
the Lucas-Lehmer residue `s p (p-2) % (2^p - 1)` is zero.
-/
def LucasLehmerTest (p : ℕ) : Prop :=
lucasLehmerResidue p = 0
#align lucas_lehmer.lucas_lehmer_test LucasLehmer.LucasLehmerTest
-- Porting note: We have a fast `norm_num` extension, and we would rather use that than accidentally
-- have `simp` use `decide`!
/-
instance : DecidablePred LucasLehmerTest :=
inferInstanceAs (DecidablePred (lucasLehmerResidue · = 0))
-/
/-- `q` is defined as the minimum factor of `mersenne p`, bundled as an `ℕ+`. -/
def q (p : ℕ) : ℕ+ :=
⟨Nat.minFac (mersenne p), Nat.minFac_pos (mersenne p)⟩
#align lucas_lehmer.q LucasLehmer.q
-- It would be nice to define this as (ℤ/qℤ)[x] / (x^2 - 3),
-- obtaining the ring structure for free,
-- but that seems to be more trouble than it's worth;
-- if it were easy to make the definition,
-- cardinality calculations would be somewhat more involved, too.
/-- We construct the ring `X q` as ℤ/qℤ + √3 ℤ/qℤ. -/
def X (q : ℕ+) : Type :=
ZMod q × ZMod q
set_option linter.uppercaseLean3 false in
#align lucas_lehmer.X LucasLehmer.X
namespace X
variable {q : ℕ+}
instance : Inhabited (X q) := inferInstanceAs (Inhabited (ZMod q × ZMod q))
instance : Fintype (X q) := inferInstanceAs (Fintype (ZMod q × ZMod q))
instance : DecidableEq (X q) := inferInstanceAs (DecidableEq (ZMod q × ZMod q))
instance : AddCommGroup (X q) := inferInstanceAs (AddCommGroup (ZMod q × ZMod q))
@[ext]
| Mathlib/NumberTheory/LucasLehmer.lean | 241 | 242 | theorem ext {x y : X q} (h₁ : x.1 = y.1) (h₂ : x.2 = y.2) : x = y := by |
cases x; cases y; congr
|
/-
Copyright (c) 2021 Yakov Pechersky. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yakov Pechersky, Chris Hughes
-/
import Mathlib.Data.List.Nodup
#align_import data.list.duplicate from "leanprover-community/mathlib"@"f694c7dead66f5d4c80f446c796a5aad14707f0e"
/-!
# List duplicates
## Main definitions
* `List.Duplicate x l : Prop` is an inductive property that holds when `x` is a duplicate in `l`
## Implementation details
In this file, `x ∈+ l` notation is shorthand for `List.Duplicate x l`.
-/
variable {α : Type*}
namespace List
/-- Property that an element `x : α` of `l : List α` can be found in the list more than once. -/
inductive Duplicate (x : α) : List α → Prop
| cons_mem {l : List α} : x ∈ l → Duplicate x (x :: l)
| cons_duplicate {y : α} {l : List α} : Duplicate x l → Duplicate x (y :: l)
#align list.duplicate List.Duplicate
local infixl:50 " ∈+ " => List.Duplicate
variable {l : List α} {x : α}
theorem Mem.duplicate_cons_self (h : x ∈ l) : x ∈+ x :: l :=
Duplicate.cons_mem h
#align list.mem.duplicate_cons_self List.Mem.duplicate_cons_self
theorem Duplicate.duplicate_cons (h : x ∈+ l) (y : α) : x ∈+ y :: l :=
Duplicate.cons_duplicate h
#align list.duplicate.duplicate_cons List.Duplicate.duplicate_cons
theorem Duplicate.mem (h : x ∈+ l) : x ∈ l := by
induction' h with l' _ y l' _ hm
· exact mem_cons_self _ _
· exact mem_cons_of_mem _ hm
#align list.duplicate.mem List.Duplicate.mem
theorem Duplicate.mem_cons_self (h : x ∈+ x :: l) : x ∈ l := by
cases' h with _ h _ _ h
· exact h
· exact h.mem
#align list.duplicate.mem_cons_self List.Duplicate.mem_cons_self
@[simp]
theorem duplicate_cons_self_iff : x ∈+ x :: l ↔ x ∈ l :=
⟨Duplicate.mem_cons_self, Mem.duplicate_cons_self⟩
#align list.duplicate_cons_self_iff List.duplicate_cons_self_iff
theorem Duplicate.ne_nil (h : x ∈+ l) : l ≠ [] := fun H => (mem_nil_iff x).mp (H ▸ h.mem)
#align list.duplicate.ne_nil List.Duplicate.ne_nil
@[simp]
theorem not_duplicate_nil (x : α) : ¬x ∈+ [] := fun H => H.ne_nil rfl
#align list.not_duplicate_nil List.not_duplicate_nil
theorem Duplicate.ne_singleton (h : x ∈+ l) (y : α) : l ≠ [y] := by
induction' h with l' h z l' h _
· simp [ne_nil_of_mem h]
· simp [ne_nil_of_mem h.mem]
#align list.duplicate.ne_singleton List.Duplicate.ne_singleton
@[simp]
theorem not_duplicate_singleton (x y : α) : ¬x ∈+ [y] := fun H => H.ne_singleton _ rfl
#align list.not_duplicate_singleton List.not_duplicate_singleton
theorem Duplicate.elim_nil (h : x ∈+ []) : False :=
not_duplicate_nil x h
#align list.duplicate.elim_nil List.Duplicate.elim_nil
theorem Duplicate.elim_singleton {y : α} (h : x ∈+ [y]) : False :=
not_duplicate_singleton x y h
#align list.duplicate.elim_singleton List.Duplicate.elim_singleton
| Mathlib/Data/List/Duplicate.lean | 88 | 95 | theorem duplicate_cons_iff {y : α} : x ∈+ y :: l ↔ y = x ∧ x ∈ l ∨ x ∈+ l := by |
refine ⟨fun h => ?_, fun h => ?_⟩
· cases' h with _ hm _ _ hm
· exact Or.inl ⟨rfl, hm⟩
· exact Or.inr hm
· rcases h with (⟨rfl | h⟩ | h)
· simpa
· exact h.cons_duplicate
|
/-
Copyright (c) 2023 David Loeffler. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: David Loeffler
-/
import Mathlib.Analysis.SpecialFunctions.Gaussian.GaussianIntegral
#align_import analysis.special_functions.gamma.bohr_mollerup from "leanprover-community/mathlib"@"a3209ddf94136d36e5e5c624b10b2a347cc9d090"
/-! # Convexity properties of the Gamma function
In this file, we prove that `Gamma` and `log ∘ Gamma` are convex functions on the positive real
line. We then prove the Bohr-Mollerup theorem, which characterises `Gamma` as the *unique*
positive-real-valued, log-convex function on the positive reals satisfying `f (x + 1) = x f x` and
`f 1 = 1`.
The proof of the Bohr-Mollerup theorem is bound up with the proof of (a weak form of) the Euler
limit formula, `Real.BohrMollerup.tendsto_logGammaSeq`, stating that for positive
real `x` the sequence `x * log n + log n! - ∑ (m : ℕ) ∈ Finset.range (n + 1), log (x + m)`
tends to `log Γ(x)` as `n → ∞`. We prove that any function satisfying the hypotheses of the
Bohr-Mollerup theorem must agree with the limit in the Euler limit formula, so there is at most one
such function; then we show that `Γ` satisfies these conditions.
Since most of the auxiliary lemmas for the Bohr-Mollerup theorem are of no relevance outside the
context of this proof, we place them in a separate namespace `Real.BohrMollerup` to avoid clutter.
(This includes the logarithmic form of the Euler limit formula, since later we will prove a more
general form of the Euler limit formula valid for any real or complex `x`; see
`Real.Gamma_seq_tendsto_Gamma` and `Complex.Gamma_seq_tendsto_Gamma` in the file
`Mathlib/Analysis/SpecialFunctions/Gamma/Beta.lean`.)
As an application of the Bohr-Mollerup theorem we prove the Legendre doubling formula for the
Gamma function for real positive `s` (which will be upgraded to a proof for all complex `s` in a
later file).
TODO: This argument can be extended to prove the general `k`-multiplication formula (at least up
to a constant, and it should be possible to deduce the value of this constant using Stirling's
formula).
-/
set_option linter.uppercaseLean3 false
noncomputable section
open Filter Set MeasureTheory
open scoped Nat ENNReal Topology Real
section Convexity
-- Porting note: move the following lemmas to `Analysis.Convex.Function`
variable {𝕜 E β : Type*} {s : Set E} {f g : E → β} [OrderedSemiring 𝕜] [SMul 𝕜 E] [AddCommMonoid E]
[OrderedAddCommMonoid β]
theorem ConvexOn.congr [SMul 𝕜 β] (hf : ConvexOn 𝕜 s f) (hfg : EqOn f g s) : ConvexOn 𝕜 s g :=
⟨hf.1, fun x hx y hy a b ha hb hab => by
simpa only [← hfg hx, ← hfg hy, ← hfg (hf.1 hx hy ha hb hab)] using hf.2 hx hy ha hb hab⟩
#align convex_on.congr ConvexOn.congr
theorem ConcaveOn.congr [SMul 𝕜 β] (hf : ConcaveOn 𝕜 s f) (hfg : EqOn f g s) : ConcaveOn 𝕜 s g :=
⟨hf.1, fun x hx y hy a b ha hb hab => by
simpa only [← hfg hx, ← hfg hy, ← hfg (hf.1 hx hy ha hb hab)] using hf.2 hx hy ha hb hab⟩
#align concave_on.congr ConcaveOn.congr
theorem StrictConvexOn.congr [SMul 𝕜 β] (hf : StrictConvexOn 𝕜 s f) (hfg : EqOn f g s) :
StrictConvexOn 𝕜 s g :=
⟨hf.1, fun x hx y hy hxy a b ha hb hab => by
simpa only [← hfg hx, ← hfg hy, ← hfg (hf.1 hx hy ha.le hb.le hab)] using
hf.2 hx hy hxy ha hb hab⟩
#align strict_convex_on.congr StrictConvexOn.congr
theorem StrictConcaveOn.congr [SMul 𝕜 β] (hf : StrictConcaveOn 𝕜 s f) (hfg : EqOn f g s) :
StrictConcaveOn 𝕜 s g :=
⟨hf.1, fun x hx y hy hxy a b ha hb hab => by
simpa only [← hfg hx, ← hfg hy, ← hfg (hf.1 hx hy ha.le hb.le hab)] using
hf.2 hx hy hxy ha hb hab⟩
#align strict_concave_on.congr StrictConcaveOn.congr
theorem ConvexOn.add_const [Module 𝕜 β] (hf : ConvexOn 𝕜 s f) (b : β) :
ConvexOn 𝕜 s (f + fun _ => b) :=
hf.add (convexOn_const _ hf.1)
#align convex_on.add_const ConvexOn.add_const
theorem ConcaveOn.add_const [Module 𝕜 β] (hf : ConcaveOn 𝕜 s f) (b : β) :
ConcaveOn 𝕜 s (f + fun _ => b) :=
hf.add (concaveOn_const _ hf.1)
#align concave_on.add_const ConcaveOn.add_const
theorem StrictConvexOn.add_const {γ : Type*} {f : E → γ} [OrderedCancelAddCommMonoid γ]
[Module 𝕜 γ] (hf : StrictConvexOn 𝕜 s f) (b : γ) : StrictConvexOn 𝕜 s (f + fun _ => b) :=
hf.add_convexOn (convexOn_const _ hf.1)
#align strict_convex_on.add_const StrictConvexOn.add_const
theorem StrictConcaveOn.add_const {γ : Type*} {f : E → γ} [OrderedCancelAddCommMonoid γ]
[Module 𝕜 γ] (hf : StrictConcaveOn 𝕜 s f) (b : γ) : StrictConcaveOn 𝕜 s (f + fun _ => b) :=
hf.add_concaveOn (concaveOn_const _ hf.1)
#align strict_concave_on.add_const StrictConcaveOn.add_const
end Convexity
namespace Real
section Convexity
/-- Log-convexity of the Gamma function on the positive reals (stated in multiplicative form),
proved using the Hölder inequality applied to Euler's integral. -/
| Mathlib/Analysis/SpecialFunctions/Gamma/BohrMollerup.lean | 106 | 161 | theorem Gamma_mul_add_mul_le_rpow_Gamma_mul_rpow_Gamma {s t a b : ℝ} (hs : 0 < s) (ht : 0 < t)
(ha : 0 < a) (hb : 0 < b) (hab : a + b = 1) :
Gamma (a * s + b * t) ≤ Gamma s ^ a * Gamma t ^ b := by |
-- We will apply Hölder's inequality, for the conjugate exponents `p = 1 / a`
-- and `q = 1 / b`, to the functions `f a s` and `f b t`, where `f` is as follows:
let f : ℝ → ℝ → ℝ → ℝ := fun c u x => exp (-c * x) * x ^ (c * (u - 1))
have e : IsConjExponent (1 / a) (1 / b) := Real.isConjExponent_one_div ha hb hab
have hab' : b = 1 - a := by linarith
have hst : 0 < a * s + b * t := add_pos (mul_pos ha hs) (mul_pos hb ht)
-- some properties of f:
have posf : ∀ c u x : ℝ, x ∈ Ioi (0 : ℝ) → 0 ≤ f c u x := fun c u x hx =>
mul_nonneg (exp_pos _).le (rpow_pos_of_pos hx _).le
have posf' : ∀ c u : ℝ, ∀ᵐ x : ℝ ∂volume.restrict (Ioi 0), 0 ≤ f c u x := fun c u =>
(ae_restrict_iff' measurableSet_Ioi).mpr (ae_of_all _ (posf c u))
have fpow :
∀ {c x : ℝ} (_ : 0 < c) (u : ℝ) (_ : 0 < x), exp (-x) * x ^ (u - 1) = f c u x ^ (1 / c) := by
intro c x hc u hx
dsimp only [f]
rw [mul_rpow (exp_pos _).le ((rpow_nonneg hx.le) _), ← exp_mul, ← rpow_mul hx.le]
congr 2 <;> field_simp [hc.ne']; ring
-- show `f c u` is in `ℒp` for `p = 1/c`:
have f_mem_Lp :
∀ {c u : ℝ} (hc : 0 < c) (hu : 0 < u),
Memℒp (f c u) (ENNReal.ofReal (1 / c)) (volume.restrict (Ioi 0)) := by
intro c u hc hu
have A : ENNReal.ofReal (1 / c) ≠ 0 := by
rwa [Ne, ENNReal.ofReal_eq_zero, not_le, one_div_pos]
have B : ENNReal.ofReal (1 / c) ≠ ∞ := ENNReal.ofReal_ne_top
rw [← memℒp_norm_rpow_iff _ A B, ENNReal.toReal_ofReal (one_div_nonneg.mpr hc.le),
ENNReal.div_self A B, memℒp_one_iff_integrable]
· apply Integrable.congr (GammaIntegral_convergent hu)
refine eventuallyEq_of_mem (self_mem_ae_restrict measurableSet_Ioi) fun x hx => ?_
dsimp only
rw [fpow hc u hx]
congr 1
exact (norm_of_nonneg (posf _ _ x hx)).symm
· refine ContinuousOn.aestronglyMeasurable ?_ measurableSet_Ioi
refine (Continuous.continuousOn ?_).mul (ContinuousAt.continuousOn fun x hx => ?_)
· exact continuous_exp.comp (continuous_const.mul continuous_id')
· exact continuousAt_rpow_const _ _ (Or.inl (mem_Ioi.mp hx).ne')
-- now apply Hölder:
rw [Gamma_eq_integral hs, Gamma_eq_integral ht, Gamma_eq_integral hst]
convert
MeasureTheory.integral_mul_le_Lp_mul_Lq_of_nonneg e (posf' a s) (posf' b t) (f_mem_Lp ha hs)
(f_mem_Lp hb ht) using
1
· refine setIntegral_congr measurableSet_Ioi fun x hx => ?_
dsimp only
have A : exp (-x) = exp (-a * x) * exp (-b * x) := by
rw [← exp_add, ← add_mul, ← neg_add, hab, neg_one_mul]
have B : x ^ (a * s + b * t - 1) = x ^ (a * (s - 1)) * x ^ (b * (t - 1)) := by
rw [← rpow_add hx, hab']; congr 1; ring
rw [A, B]
ring
· rw [one_div_one_div, one_div_one_div]
congr 2 <;> exact setIntegral_congr measurableSet_Ioi fun x hx => fpow (by assumption) _ hx
|
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Johan Commelin, Mario Carneiro
-/
import Mathlib.Algebra.Algebra.Tower
import Mathlib.Algebra.GroupWithZero.Divisibility
import Mathlib.Algebra.Regular.Pow
import Mathlib.Algebra.MonoidAlgebra.Support
import Mathlib.Data.Finsupp.Antidiagonal
import Mathlib.Order.SymmDiff
import Mathlib.RingTheory.Adjoin.Basic
#align_import data.mv_polynomial.basic from "leanprover-community/mathlib"@"c8734e8953e4b439147bd6f75c2163f6d27cdce6"
/-!
# Multivariate polynomials
This file defines polynomial rings over a base ring (or even semiring),
with variables from a general type `σ` (which could be infinite).
## Important definitions
Let `R` be a commutative ring (or a semiring) and let `σ` be an arbitrary
type. This file creates the type `MvPolynomial σ R`, which mathematicians
might denote $R[X_i : i \in σ]$. It is the type of multivariate
(a.k.a. multivariable) polynomials, with variables
corresponding to the terms in `σ`, and coefficients in `R`.
### Notation
In the definitions below, we use the following notation:
+ `σ : Type*` (indexing the variables)
+ `R : Type*` `[CommSemiring R]` (the coefficients)
+ `s : σ →₀ ℕ`, a function from `σ` to `ℕ` which is zero away from a finite set.
This will give rise to a monomial in `MvPolynomial σ R` which mathematicians might call `X^s`
+ `a : R`
+ `i : σ`, with corresponding monomial `X i`, often denoted `X_i` by mathematicians
+ `p : MvPolynomial σ R`
### Definitions
* `MvPolynomial σ R` : the type of polynomials with variables of type `σ` and coefficients
in the commutative semiring `R`
* `monomial s a` : the monomial which mathematically would be denoted `a * X^s`
* `C a` : the constant polynomial with value `a`
* `X i` : the degree one monomial corresponding to i; mathematically this might be denoted `Xᵢ`.
* `coeff s p` : the coefficient of `s` in `p`.
* `eval₂ (f : R → S₁) (g : σ → S₁) p` : given a semiring homomorphism from `R` to another
semiring `S₁`, and a map `σ → S₁`, evaluates `p` at this valuation, returning a term of type `S₁`.
Note that `eval₂` can be made using `eval` and `map` (see below), and it has been suggested
that sticking to `eval` and `map` might make the code less brittle.
* `eval (g : σ → R) p` : given a map `σ → R`, evaluates `p` at this valuation,
returning a term of type `R`
* `map (f : R → S₁) p` : returns the multivariate polynomial obtained from `p` by the change of
coefficient semiring corresponding to `f`
## Implementation notes
Recall that if `Y` has a zero, then `X →₀ Y` is the type of functions from `X` to `Y` with finite
support, i.e. such that only finitely many elements of `X` get sent to non-zero terms in `Y`.
The definition of `MvPolynomial σ R` is `(σ →₀ ℕ) →₀ R`; here `σ →₀ ℕ` denotes the space of all
monomials in the variables, and the function to `R` sends a monomial to its coefficient in
the polynomial being represented.
## Tags
polynomial, multivariate polynomial, multivariable polynomial
-/
noncomputable section
open Set Function Finsupp AddMonoidAlgebra
open scoped Pointwise
universe u v w x
variable {R : Type u} {S₁ : Type v} {S₂ : Type w} {S₃ : Type x}
/-- Multivariate polynomial, where `σ` is the index set of the variables and
`R` is the coefficient ring -/
def MvPolynomial (σ : Type*) (R : Type*) [CommSemiring R] :=
AddMonoidAlgebra R (σ →₀ ℕ)
#align mv_polynomial MvPolynomial
namespace MvPolynomial
-- Porting note: because of `MvPolynomial.C` and `MvPolynomial.X` this linter throws
-- tons of warnings in this file, and it's easier to just disable them globally in the file
set_option linter.uppercaseLean3 false
variable {σ : Type*} {a a' a₁ a₂ : R} {e : ℕ} {n m : σ} {s : σ →₀ ℕ}
section CommSemiring
section Instances
instance decidableEqMvPolynomial [CommSemiring R] [DecidableEq σ] [DecidableEq R] :
DecidableEq (MvPolynomial σ R) :=
Finsupp.instDecidableEq
#align mv_polynomial.decidable_eq_mv_polynomial MvPolynomial.decidableEqMvPolynomial
instance commSemiring [CommSemiring R] : CommSemiring (MvPolynomial σ R) :=
AddMonoidAlgebra.commSemiring
instance inhabited [CommSemiring R] : Inhabited (MvPolynomial σ R) :=
⟨0⟩
instance distribuMulAction [Monoid R] [CommSemiring S₁] [DistribMulAction R S₁] :
DistribMulAction R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.distribMulAction
instance smulZeroClass [CommSemiring S₁] [SMulZeroClass R S₁] :
SMulZeroClass R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.smulZeroClass
instance faithfulSMul [CommSemiring S₁] [SMulZeroClass R S₁] [FaithfulSMul R S₁] :
FaithfulSMul R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.faithfulSMul
instance module [Semiring R] [CommSemiring S₁] [Module R S₁] : Module R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.module
instance isScalarTower [CommSemiring S₂] [SMul R S₁] [SMulZeroClass R S₂] [SMulZeroClass S₁ S₂]
[IsScalarTower R S₁ S₂] : IsScalarTower R S₁ (MvPolynomial σ S₂) :=
AddMonoidAlgebra.isScalarTower
instance smulCommClass [CommSemiring S₂] [SMulZeroClass R S₂] [SMulZeroClass S₁ S₂]
[SMulCommClass R S₁ S₂] : SMulCommClass R S₁ (MvPolynomial σ S₂) :=
AddMonoidAlgebra.smulCommClass
instance isCentralScalar [CommSemiring S₁] [SMulZeroClass R S₁] [SMulZeroClass Rᵐᵒᵖ S₁]
[IsCentralScalar R S₁] : IsCentralScalar R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.isCentralScalar
instance algebra [CommSemiring R] [CommSemiring S₁] [Algebra R S₁] :
Algebra R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.algebra
instance isScalarTower_right [CommSemiring S₁] [DistribSMul R S₁] [IsScalarTower R S₁ S₁] :
IsScalarTower R (MvPolynomial σ S₁) (MvPolynomial σ S₁) :=
AddMonoidAlgebra.isScalarTower_self _
#align mv_polynomial.is_scalar_tower_right MvPolynomial.isScalarTower_right
instance smulCommClass_right [CommSemiring S₁] [DistribSMul R S₁] [SMulCommClass R S₁ S₁] :
SMulCommClass R (MvPolynomial σ S₁) (MvPolynomial σ S₁) :=
AddMonoidAlgebra.smulCommClass_self _
#align mv_polynomial.smul_comm_class_right MvPolynomial.smulCommClass_right
/-- If `R` is a subsingleton, then `MvPolynomial σ R` has a unique element -/
instance unique [CommSemiring R] [Subsingleton R] : Unique (MvPolynomial σ R) :=
AddMonoidAlgebra.unique
#align mv_polynomial.unique MvPolynomial.unique
end Instances
variable [CommSemiring R] [CommSemiring S₁] {p q : MvPolynomial σ R}
/-- `monomial s a` is the monomial with coefficient `a` and exponents given by `s` -/
def monomial (s : σ →₀ ℕ) : R →ₗ[R] MvPolynomial σ R :=
lsingle s
#align mv_polynomial.monomial MvPolynomial.monomial
theorem single_eq_monomial (s : σ →₀ ℕ) (a : R) : Finsupp.single s a = monomial s a :=
rfl
#align mv_polynomial.single_eq_monomial MvPolynomial.single_eq_monomial
theorem mul_def : p * q = p.sum fun m a => q.sum fun n b => monomial (m + n) (a * b) :=
AddMonoidAlgebra.mul_def
#align mv_polynomial.mul_def MvPolynomial.mul_def
/-- `C a` is the constant polynomial with value `a` -/
def C : R →+* MvPolynomial σ R :=
{ singleZeroRingHom with toFun := monomial 0 }
#align mv_polynomial.C MvPolynomial.C
variable (R σ)
@[simp]
theorem algebraMap_eq : algebraMap R (MvPolynomial σ R) = C :=
rfl
#align mv_polynomial.algebra_map_eq MvPolynomial.algebraMap_eq
variable {R σ}
/-- `X n` is the degree `1` monomial $X_n$. -/
def X (n : σ) : MvPolynomial σ R :=
monomial (Finsupp.single n 1) 1
#align mv_polynomial.X MvPolynomial.X
theorem monomial_left_injective {r : R} (hr : r ≠ 0) :
Function.Injective fun s : σ →₀ ℕ => monomial s r :=
Finsupp.single_left_injective hr
#align mv_polynomial.monomial_left_injective MvPolynomial.monomial_left_injective
@[simp]
theorem monomial_left_inj {s t : σ →₀ ℕ} {r : R} (hr : r ≠ 0) :
monomial s r = monomial t r ↔ s = t :=
Finsupp.single_left_inj hr
#align mv_polynomial.monomial_left_inj MvPolynomial.monomial_left_inj
theorem C_apply : (C a : MvPolynomial σ R) = monomial 0 a :=
rfl
#align mv_polynomial.C_apply MvPolynomial.C_apply
-- Porting note (#10618): `simp` can prove this
theorem C_0 : C 0 = (0 : MvPolynomial σ R) := map_zero _
#align mv_polynomial.C_0 MvPolynomial.C_0
-- Porting note (#10618): `simp` can prove this
theorem C_1 : C 1 = (1 : MvPolynomial σ R) :=
rfl
#align mv_polynomial.C_1 MvPolynomial.C_1
theorem C_mul_monomial : C a * monomial s a' = monomial s (a * a') := by
-- Porting note: this `show` feels like defeq abuse, but I can't find the appropriate lemmas
show AddMonoidAlgebra.single _ _ * AddMonoidAlgebra.single _ _ = AddMonoidAlgebra.single _ _
simp [C_apply, single_mul_single]
#align mv_polynomial.C_mul_monomial MvPolynomial.C_mul_monomial
-- Porting note (#10618): `simp` can prove this
theorem C_add : (C (a + a') : MvPolynomial σ R) = C a + C a' :=
Finsupp.single_add _ _ _
#align mv_polynomial.C_add MvPolynomial.C_add
-- Porting note (#10618): `simp` can prove this
theorem C_mul : (C (a * a') : MvPolynomial σ R) = C a * C a' :=
C_mul_monomial.symm
#align mv_polynomial.C_mul MvPolynomial.C_mul
-- Porting note (#10618): `simp` can prove this
theorem C_pow (a : R) (n : ℕ) : (C (a ^ n) : MvPolynomial σ R) = C a ^ n :=
map_pow _ _ _
#align mv_polynomial.C_pow MvPolynomial.C_pow
theorem C_injective (σ : Type*) (R : Type*) [CommSemiring R] :
Function.Injective (C : R → MvPolynomial σ R) :=
Finsupp.single_injective _
#align mv_polynomial.C_injective MvPolynomial.C_injective
theorem C_surjective {R : Type*} [CommSemiring R] (σ : Type*) [IsEmpty σ] :
Function.Surjective (C : R → MvPolynomial σ R) := by
refine fun p => ⟨p.toFun 0, Finsupp.ext fun a => ?_⟩
simp only [C_apply, ← single_eq_monomial, (Finsupp.ext isEmptyElim (α := σ) : a = 0),
single_eq_same]
rfl
#align mv_polynomial.C_surjective MvPolynomial.C_surjective
@[simp]
theorem C_inj {σ : Type*} (R : Type*) [CommSemiring R] (r s : R) :
(C r : MvPolynomial σ R) = C s ↔ r = s :=
(C_injective σ R).eq_iff
#align mv_polynomial.C_inj MvPolynomial.C_inj
instance nontrivial_of_nontrivial (σ : Type*) (R : Type*) [CommSemiring R] [Nontrivial R] :
Nontrivial (MvPolynomial σ R) :=
inferInstanceAs (Nontrivial <| AddMonoidAlgebra R (σ →₀ ℕ))
instance infinite_of_infinite (σ : Type*) (R : Type*) [CommSemiring R] [Infinite R] :
Infinite (MvPolynomial σ R) :=
Infinite.of_injective C (C_injective _ _)
#align mv_polynomial.infinite_of_infinite MvPolynomial.infinite_of_infinite
instance infinite_of_nonempty (σ : Type*) (R : Type*) [Nonempty σ] [CommSemiring R]
[Nontrivial R] : Infinite (MvPolynomial σ R) :=
Infinite.of_injective ((fun s : σ →₀ ℕ => monomial s 1) ∘ Finsupp.single (Classical.arbitrary σ))
<| (monomial_left_injective one_ne_zero).comp (Finsupp.single_injective _)
#align mv_polynomial.infinite_of_nonempty MvPolynomial.infinite_of_nonempty
theorem C_eq_coe_nat (n : ℕ) : (C ↑n : MvPolynomial σ R) = n := by
induction n <;> simp [Nat.succ_eq_add_one, *]
#align mv_polynomial.C_eq_coe_nat MvPolynomial.C_eq_coe_nat
theorem C_mul' : MvPolynomial.C a * p = a • p :=
(Algebra.smul_def a p).symm
#align mv_polynomial.C_mul' MvPolynomial.C_mul'
theorem smul_eq_C_mul (p : MvPolynomial σ R) (a : R) : a • p = C a * p :=
C_mul'.symm
#align mv_polynomial.smul_eq_C_mul MvPolynomial.smul_eq_C_mul
theorem C_eq_smul_one : (C a : MvPolynomial σ R) = a • (1 : MvPolynomial σ R) := by
rw [← C_mul', mul_one]
#align mv_polynomial.C_eq_smul_one MvPolynomial.C_eq_smul_one
theorem smul_monomial {S₁ : Type*} [SMulZeroClass S₁ R] (r : S₁) :
r • monomial s a = monomial s (r • a) :=
Finsupp.smul_single _ _ _
#align mv_polynomial.smul_monomial MvPolynomial.smul_monomial
theorem X_injective [Nontrivial R] : Function.Injective (X : σ → MvPolynomial σ R) :=
(monomial_left_injective one_ne_zero).comp (Finsupp.single_left_injective one_ne_zero)
#align mv_polynomial.X_injective MvPolynomial.X_injective
@[simp]
theorem X_inj [Nontrivial R] (m n : σ) : X m = (X n : MvPolynomial σ R) ↔ m = n :=
X_injective.eq_iff
#align mv_polynomial.X_inj MvPolynomial.X_inj
theorem monomial_pow : monomial s a ^ e = monomial (e • s) (a ^ e) :=
AddMonoidAlgebra.single_pow e
#align mv_polynomial.monomial_pow MvPolynomial.monomial_pow
@[simp]
theorem monomial_mul {s s' : σ →₀ ℕ} {a b : R} :
monomial s a * monomial s' b = monomial (s + s') (a * b) :=
AddMonoidAlgebra.single_mul_single
#align mv_polynomial.monomial_mul MvPolynomial.monomial_mul
variable (σ R)
/-- `fun s ↦ monomial s 1` as a homomorphism. -/
def monomialOneHom : Multiplicative (σ →₀ ℕ) →* MvPolynomial σ R :=
AddMonoidAlgebra.of _ _
#align mv_polynomial.monomial_one_hom MvPolynomial.monomialOneHom
variable {σ R}
@[simp]
theorem monomialOneHom_apply : monomialOneHom R σ s = (monomial s 1 : MvPolynomial σ R) :=
rfl
#align mv_polynomial.monomial_one_hom_apply MvPolynomial.monomialOneHom_apply
theorem X_pow_eq_monomial : X n ^ e = monomial (Finsupp.single n e) (1 : R) := by
simp [X, monomial_pow]
#align mv_polynomial.X_pow_eq_monomial MvPolynomial.X_pow_eq_monomial
theorem monomial_add_single : monomial (s + Finsupp.single n e) a = monomial s a * X n ^ e := by
rw [X_pow_eq_monomial, monomial_mul, mul_one]
#align mv_polynomial.monomial_add_single MvPolynomial.monomial_add_single
theorem monomial_single_add : monomial (Finsupp.single n e + s) a = X n ^ e * monomial s a := by
rw [X_pow_eq_monomial, monomial_mul, one_mul]
#align mv_polynomial.monomial_single_add MvPolynomial.monomial_single_add
theorem C_mul_X_pow_eq_monomial {s : σ} {a : R} {n : ℕ} :
C a * X s ^ n = monomial (Finsupp.single s n) a := by
rw [← zero_add (Finsupp.single s n), monomial_add_single, C_apply]
#align mv_polynomial.C_mul_X_pow_eq_monomial MvPolynomial.C_mul_X_pow_eq_monomial
theorem C_mul_X_eq_monomial {s : σ} {a : R} : C a * X s = monomial (Finsupp.single s 1) a := by
rw [← C_mul_X_pow_eq_monomial, pow_one]
#align mv_polynomial.C_mul_X_eq_monomial MvPolynomial.C_mul_X_eq_monomial
-- Porting note (#10618): `simp` can prove this
theorem monomial_zero {s : σ →₀ ℕ} : monomial s (0 : R) = 0 :=
Finsupp.single_zero _
#align mv_polynomial.monomial_zero MvPolynomial.monomial_zero
@[simp]
theorem monomial_zero' : (monomial (0 : σ →₀ ℕ) : R → MvPolynomial σ R) = C :=
rfl
#align mv_polynomial.monomial_zero' MvPolynomial.monomial_zero'
@[simp]
theorem monomial_eq_zero {s : σ →₀ ℕ} {b : R} : monomial s b = 0 ↔ b = 0 :=
Finsupp.single_eq_zero
#align mv_polynomial.monomial_eq_zero MvPolynomial.monomial_eq_zero
@[simp]
theorem sum_monomial_eq {A : Type*} [AddCommMonoid A] {u : σ →₀ ℕ} {r : R} {b : (σ →₀ ℕ) → R → A}
(w : b u 0 = 0) : sum (monomial u r) b = b u r :=
Finsupp.sum_single_index w
#align mv_polynomial.sum_monomial_eq MvPolynomial.sum_monomial_eq
@[simp]
theorem sum_C {A : Type*} [AddCommMonoid A] {b : (σ →₀ ℕ) → R → A} (w : b 0 0 = 0) :
sum (C a) b = b 0 a :=
sum_monomial_eq w
#align mv_polynomial.sum_C MvPolynomial.sum_C
theorem monomial_sum_one {α : Type*} (s : Finset α) (f : α → σ →₀ ℕ) :
(monomial (∑ i ∈ s, f i) 1 : MvPolynomial σ R) = ∏ i ∈ s, monomial (f i) 1 :=
map_prod (monomialOneHom R σ) (fun i => Multiplicative.ofAdd (f i)) s
#align mv_polynomial.monomial_sum_one MvPolynomial.monomial_sum_one
theorem monomial_sum_index {α : Type*} (s : Finset α) (f : α → σ →₀ ℕ) (a : R) :
monomial (∑ i ∈ s, f i) a = C a * ∏ i ∈ s, monomial (f i) 1 := by
rw [← monomial_sum_one, C_mul', ← (monomial _).map_smul, smul_eq_mul, mul_one]
#align mv_polynomial.monomial_sum_index MvPolynomial.monomial_sum_index
theorem monomial_finsupp_sum_index {α β : Type*} [Zero β] (f : α →₀ β) (g : α → β → σ →₀ ℕ)
(a : R) : monomial (f.sum g) a = C a * f.prod fun a b => monomial (g a b) 1 :=
monomial_sum_index _ _ _
#align mv_polynomial.monomial_finsupp_sum_index MvPolynomial.monomial_finsupp_sum_index
theorem monomial_eq_monomial_iff {α : Type*} (a₁ a₂ : α →₀ ℕ) (b₁ b₂ : R) :
monomial a₁ b₁ = monomial a₂ b₂ ↔ a₁ = a₂ ∧ b₁ = b₂ ∨ b₁ = 0 ∧ b₂ = 0 :=
Finsupp.single_eq_single_iff _ _ _ _
#align mv_polynomial.monomial_eq_monomial_iff MvPolynomial.monomial_eq_monomial_iff
theorem monomial_eq : monomial s a = C a * (s.prod fun n e => X n ^ e : MvPolynomial σ R) := by
simp only [X_pow_eq_monomial, ← monomial_finsupp_sum_index, Finsupp.sum_single]
#align mv_polynomial.monomial_eq MvPolynomial.monomial_eq
@[simp]
lemma prod_X_pow_eq_monomial : ∏ x ∈ s.support, X x ^ s x = monomial s (1 : R) := by
simp only [monomial_eq, map_one, one_mul, Finsupp.prod]
theorem induction_on_monomial {M : MvPolynomial σ R → Prop} (h_C : ∀ a, M (C a))
(h_X : ∀ p n, M p → M (p * X n)) : ∀ s a, M (monomial s a) := by
intro s a
apply @Finsupp.induction σ ℕ _ _ s
· show M (monomial 0 a)
exact h_C a
· intro n e p _hpn _he ih
have : ∀ e : ℕ, M (monomial p a * X n ^ e) := by
intro e
induction e with
| zero => simp [ih]
| succ e e_ih => simp [ih, pow_succ, (mul_assoc _ _ _).symm, h_X, e_ih]
simp [add_comm, monomial_add_single, this]
#align mv_polynomial.induction_on_monomial MvPolynomial.induction_on_monomial
/-- Analog of `Polynomial.induction_on'`.
To prove something about mv_polynomials,
it suffices to show the condition is closed under taking sums,
and it holds for monomials. -/
@[elab_as_elim]
theorem induction_on' {P : MvPolynomial σ R → Prop} (p : MvPolynomial σ R)
(h1 : ∀ (u : σ →₀ ℕ) (a : R), P (monomial u a))
(h2 : ∀ p q : MvPolynomial σ R, P p → P q → P (p + q)) : P p :=
Finsupp.induction p
(suffices P (monomial 0 0) by rwa [monomial_zero] at this
show P (monomial 0 0) from h1 0 0)
fun a b f _ha _hb hPf => h2 _ _ (h1 _ _) hPf
#align mv_polynomial.induction_on' MvPolynomial.induction_on'
/-- Similar to `MvPolynomial.induction_on` but only a weak form of `h_add` is required. -/
theorem induction_on''' {M : MvPolynomial σ R → Prop} (p : MvPolynomial σ R) (h_C : ∀ a, M (C a))
(h_add_weak :
∀ (a : σ →₀ ℕ) (b : R) (f : (σ →₀ ℕ) →₀ R),
a ∉ f.support → b ≠ 0 → M f → M ((show (σ →₀ ℕ) →₀ R from monomial a b) + f)) :
M p :=
-- Porting note: I had to add the `show ... from ...` above, a type ascription was insufficient.
Finsupp.induction p (C_0.rec <| h_C 0) h_add_weak
#align mv_polynomial.induction_on''' MvPolynomial.induction_on'''
/-- Similar to `MvPolynomial.induction_on` but only a yet weaker form of `h_add` is required. -/
theorem induction_on'' {M : MvPolynomial σ R → Prop} (p : MvPolynomial σ R) (h_C : ∀ a, M (C a))
(h_add_weak :
∀ (a : σ →₀ ℕ) (b : R) (f : (σ →₀ ℕ) →₀ R),
a ∉ f.support → b ≠ 0 → M f → M (monomial a b) →
M ((show (σ →₀ ℕ) →₀ R from monomial a b) + f))
(h_X : ∀ (p : MvPolynomial σ R) (n : σ), M p → M (p * MvPolynomial.X n)) : M p :=
-- Porting note: I had to add the `show ... from ...` above, a type ascription was insufficient.
induction_on''' p h_C fun a b f ha hb hf =>
h_add_weak a b f ha hb hf <| induction_on_monomial h_C h_X a b
#align mv_polynomial.induction_on'' MvPolynomial.induction_on''
/-- Analog of `Polynomial.induction_on`. -/
@[recursor 5]
theorem induction_on {M : MvPolynomial σ R → Prop} (p : MvPolynomial σ R) (h_C : ∀ a, M (C a))
(h_add : ∀ p q, M p → M q → M (p + q)) (h_X : ∀ p n, M p → M (p * X n)) : M p :=
induction_on'' p h_C (fun a b f _ha _hb hf hm => h_add (monomial a b) f hm hf) h_X
#align mv_polynomial.induction_on MvPolynomial.induction_on
theorem ringHom_ext {A : Type*} [Semiring A] {f g : MvPolynomial σ R →+* A}
(hC : ∀ r, f (C r) = g (C r)) (hX : ∀ i, f (X i) = g (X i)) : f = g := by
refine AddMonoidAlgebra.ringHom_ext' ?_ ?_
-- Porting note: this has high priority, but Lean still chooses `RingHom.ext`, why?
-- probably because of the type synonym
· ext x
exact hC _
· apply Finsupp.mulHom_ext'; intros x
-- Porting note: `Finsupp.mulHom_ext'` needs to have increased priority
apply MonoidHom.ext_mnat
exact hX _
#align mv_polynomial.ring_hom_ext MvPolynomial.ringHom_ext
/-- See note [partially-applied ext lemmas]. -/
@[ext 1100]
theorem ringHom_ext' {A : Type*} [Semiring A] {f g : MvPolynomial σ R →+* A}
(hC : f.comp C = g.comp C) (hX : ∀ i, f (X i) = g (X i)) : f = g :=
ringHom_ext (RingHom.ext_iff.1 hC) hX
#align mv_polynomial.ring_hom_ext' MvPolynomial.ringHom_ext'
theorem hom_eq_hom [Semiring S₂] (f g : MvPolynomial σ R →+* S₂) (hC : f.comp C = g.comp C)
(hX : ∀ n : σ, f (X n) = g (X n)) (p : MvPolynomial σ R) : f p = g p :=
RingHom.congr_fun (ringHom_ext' hC hX) p
#align mv_polynomial.hom_eq_hom MvPolynomial.hom_eq_hom
theorem is_id (f : MvPolynomial σ R →+* MvPolynomial σ R) (hC : f.comp C = C)
(hX : ∀ n : σ, f (X n) = X n) (p : MvPolynomial σ R) : f p = p :=
hom_eq_hom f (RingHom.id _) hC hX p
#align mv_polynomial.is_id MvPolynomial.is_id
@[ext 1100]
theorem algHom_ext' {A B : Type*} [CommSemiring A] [CommSemiring B] [Algebra R A] [Algebra R B]
{f g : MvPolynomial σ A →ₐ[R] B}
(h₁ :
f.comp (IsScalarTower.toAlgHom R A (MvPolynomial σ A)) =
g.comp (IsScalarTower.toAlgHom R A (MvPolynomial σ A)))
(h₂ : ∀ i, f (X i) = g (X i)) : f = g :=
AlgHom.coe_ringHom_injective (MvPolynomial.ringHom_ext' (congr_arg AlgHom.toRingHom h₁) h₂)
#align mv_polynomial.alg_hom_ext' MvPolynomial.algHom_ext'
@[ext 1200]
theorem algHom_ext {A : Type*} [Semiring A] [Algebra R A] {f g : MvPolynomial σ R →ₐ[R] A}
(hf : ∀ i : σ, f (X i) = g (X i)) : f = g :=
AddMonoidAlgebra.algHom_ext' (mulHom_ext' fun X : σ => MonoidHom.ext_mnat (hf X))
#align mv_polynomial.alg_hom_ext MvPolynomial.algHom_ext
@[simp]
theorem algHom_C {τ : Type*} (f : MvPolynomial σ R →ₐ[R] MvPolynomial τ R) (r : R) :
f (C r) = C r :=
f.commutes r
#align mv_polynomial.alg_hom_C MvPolynomial.algHom_C
@[simp]
theorem adjoin_range_X : Algebra.adjoin R (range (X : σ → MvPolynomial σ R)) = ⊤ := by
set S := Algebra.adjoin R (range (X : σ → MvPolynomial σ R))
refine top_unique fun p hp => ?_; clear hp
induction p using MvPolynomial.induction_on with
| h_C => exact S.algebraMap_mem _
| h_add p q hp hq => exact S.add_mem hp hq
| h_X p i hp => exact S.mul_mem hp (Algebra.subset_adjoin <| mem_range_self _)
#align mv_polynomial.adjoin_range_X MvPolynomial.adjoin_range_X
@[ext]
theorem linearMap_ext {M : Type*} [AddCommMonoid M] [Module R M] {f g : MvPolynomial σ R →ₗ[R] M}
(h : ∀ s, f ∘ₗ monomial s = g ∘ₗ monomial s) : f = g :=
Finsupp.lhom_ext' h
#align mv_polynomial.linear_map_ext MvPolynomial.linearMap_ext
section Support
/-- The finite set of all `m : σ →₀ ℕ` such that `X^m` has a non-zero coefficient. -/
def support (p : MvPolynomial σ R) : Finset (σ →₀ ℕ) :=
Finsupp.support p
#align mv_polynomial.support MvPolynomial.support
theorem finsupp_support_eq_support (p : MvPolynomial σ R) : Finsupp.support p = p.support :=
rfl
#align mv_polynomial.finsupp_support_eq_support MvPolynomial.finsupp_support_eq_support
theorem support_monomial [h : Decidable (a = 0)] :
(monomial s a).support = if a = 0 then ∅ else {s} := by
rw [← Subsingleton.elim (Classical.decEq R a 0) h]
rfl
-- Porting note: the proof in Lean 3 wasn't fundamentally better and needed `by convert rfl`
-- the issue is the different decidability instances in the `ite` expressions
#align mv_polynomial.support_monomial MvPolynomial.support_monomial
theorem support_monomial_subset : (monomial s a).support ⊆ {s} :=
support_single_subset
#align mv_polynomial.support_monomial_subset MvPolynomial.support_monomial_subset
theorem support_add [DecidableEq σ] : (p + q).support ⊆ p.support ∪ q.support :=
Finsupp.support_add
#align mv_polynomial.support_add MvPolynomial.support_add
theorem support_X [Nontrivial R] : (X n : MvPolynomial σ R).support = {Finsupp.single n 1} := by
classical rw [X, support_monomial, if_neg]; exact one_ne_zero
#align mv_polynomial.support_X MvPolynomial.support_X
theorem support_X_pow [Nontrivial R] (s : σ) (n : ℕ) :
(X s ^ n : MvPolynomial σ R).support = {Finsupp.single s n} := by
classical
rw [X_pow_eq_monomial, support_monomial, if_neg (one_ne_zero' R)]
#align mv_polynomial.support_X_pow MvPolynomial.support_X_pow
@[simp]
theorem support_zero : (0 : MvPolynomial σ R).support = ∅ :=
rfl
#align mv_polynomial.support_zero MvPolynomial.support_zero
theorem support_smul {S₁ : Type*} [SMulZeroClass S₁ R] {a : S₁} {f : MvPolynomial σ R} :
(a • f).support ⊆ f.support :=
Finsupp.support_smul
#align mv_polynomial.support_smul MvPolynomial.support_smul
theorem support_sum {α : Type*} [DecidableEq σ] {s : Finset α} {f : α → MvPolynomial σ R} :
(∑ x ∈ s, f x).support ⊆ s.biUnion fun x => (f x).support :=
Finsupp.support_finset_sum
#align mv_polynomial.support_sum MvPolynomial.support_sum
end Support
section Coeff
/-- The coefficient of the monomial `m` in the multi-variable polynomial `p`. -/
def coeff (m : σ →₀ ℕ) (p : MvPolynomial σ R) : R :=
@DFunLike.coe ((σ →₀ ℕ) →₀ R) _ _ _ p m
-- Porting note: I changed this from `@CoeFun.coe _ _ (MonoidAlgebra.coeFun _ _) p m` because
-- I think it should work better syntactically. They are defeq.
#align mv_polynomial.coeff MvPolynomial.coeff
@[simp]
theorem mem_support_iff {p : MvPolynomial σ R} {m : σ →₀ ℕ} : m ∈ p.support ↔ p.coeff m ≠ 0 := by
simp [support, coeff]
#align mv_polynomial.mem_support_iff MvPolynomial.mem_support_iff
theorem not_mem_support_iff {p : MvPolynomial σ R} {m : σ →₀ ℕ} : m ∉ p.support ↔ p.coeff m = 0 :=
by simp
#align mv_polynomial.not_mem_support_iff MvPolynomial.not_mem_support_iff
theorem sum_def {A} [AddCommMonoid A] {p : MvPolynomial σ R} {b : (σ →₀ ℕ) → R → A} :
p.sum b = ∑ m ∈ p.support, b m (p.coeff m) := by simp [support, Finsupp.sum, coeff]
#align mv_polynomial.sum_def MvPolynomial.sum_def
theorem support_mul [DecidableEq σ] (p q : MvPolynomial σ R) :
(p * q).support ⊆ p.support + q.support :=
AddMonoidAlgebra.support_mul p q
#align mv_polynomial.support_mul MvPolynomial.support_mul
@[ext]
theorem ext (p q : MvPolynomial σ R) : (∀ m, coeff m p = coeff m q) → p = q :=
Finsupp.ext
#align mv_polynomial.ext MvPolynomial.ext
theorem ext_iff (p q : MvPolynomial σ R) : p = q ↔ ∀ m, coeff m p = coeff m q :=
⟨fun h m => by rw [h], ext p q⟩
#align mv_polynomial.ext_iff MvPolynomial.ext_iff
@[simp]
theorem coeff_add (m : σ →₀ ℕ) (p q : MvPolynomial σ R) : coeff m (p + q) = coeff m p + coeff m q :=
add_apply p q m
#align mv_polynomial.coeff_add MvPolynomial.coeff_add
@[simp]
theorem coeff_smul {S₁ : Type*} [SMulZeroClass S₁ R] (m : σ →₀ ℕ) (C : S₁) (p : MvPolynomial σ R) :
coeff m (C • p) = C • coeff m p :=
smul_apply C p m
#align mv_polynomial.coeff_smul MvPolynomial.coeff_smul
@[simp]
theorem coeff_zero (m : σ →₀ ℕ) : coeff m (0 : MvPolynomial σ R) = 0 :=
rfl
#align mv_polynomial.coeff_zero MvPolynomial.coeff_zero
@[simp]
theorem coeff_zero_X (i : σ) : coeff 0 (X i : MvPolynomial σ R) = 0 :=
single_eq_of_ne fun h => by cases Finsupp.single_eq_zero.1 h
#align mv_polynomial.coeff_zero_X MvPolynomial.coeff_zero_X
/-- `MvPolynomial.coeff m` but promoted to an `AddMonoidHom`. -/
@[simps]
def coeffAddMonoidHom (m : σ →₀ ℕ) : MvPolynomial σ R →+ R where
toFun := coeff m
map_zero' := coeff_zero m
map_add' := coeff_add m
#align mv_polynomial.coeff_add_monoid_hom MvPolynomial.coeffAddMonoidHom
variable (R) in
/-- `MvPolynomial.coeff m` but promoted to a `LinearMap`. -/
@[simps]
def lcoeff (m : σ →₀ ℕ) : MvPolynomial σ R →ₗ[R] R where
toFun := coeff m
map_add' := coeff_add m
map_smul' := coeff_smul m
theorem coeff_sum {X : Type*} (s : Finset X) (f : X → MvPolynomial σ R) (m : σ →₀ ℕ) :
coeff m (∑ x ∈ s, f x) = ∑ x ∈ s, coeff m (f x) :=
map_sum (@coeffAddMonoidHom R σ _ _) _ s
#align mv_polynomial.coeff_sum MvPolynomial.coeff_sum
theorem monic_monomial_eq (m) :
monomial m (1 : R) = (m.prod fun n e => X n ^ e : MvPolynomial σ R) := by simp [monomial_eq]
#align mv_polynomial.monic_monomial_eq MvPolynomial.monic_monomial_eq
@[simp]
theorem coeff_monomial [DecidableEq σ] (m n) (a) :
coeff m (monomial n a : MvPolynomial σ R) = if n = m then a else 0 :=
Finsupp.single_apply
#align mv_polynomial.coeff_monomial MvPolynomial.coeff_monomial
@[simp]
theorem coeff_C [DecidableEq σ] (m) (a) :
coeff m (C a : MvPolynomial σ R) = if 0 = m then a else 0 :=
Finsupp.single_apply
#align mv_polynomial.coeff_C MvPolynomial.coeff_C
lemma eq_C_of_isEmpty [IsEmpty σ] (p : MvPolynomial σ R) :
p = C (p.coeff 0) := by
obtain ⟨x, rfl⟩ := C_surjective σ p
simp
theorem coeff_one [DecidableEq σ] (m) : coeff m (1 : MvPolynomial σ R) = if 0 = m then 1 else 0 :=
coeff_C m 1
#align mv_polynomial.coeff_one MvPolynomial.coeff_one
@[simp]
theorem coeff_zero_C (a) : coeff 0 (C a : MvPolynomial σ R) = a :=
single_eq_same
#align mv_polynomial.coeff_zero_C MvPolynomial.coeff_zero_C
@[simp]
theorem coeff_zero_one : coeff 0 (1 : MvPolynomial σ R) = 1 :=
coeff_zero_C 1
#align mv_polynomial.coeff_zero_one MvPolynomial.coeff_zero_one
theorem coeff_X_pow [DecidableEq σ] (i : σ) (m) (k : ℕ) :
coeff m (X i ^ k : MvPolynomial σ R) = if Finsupp.single i k = m then 1 else 0 := by
have := coeff_monomial m (Finsupp.single i k) (1 : R)
rwa [@monomial_eq _ _ (1 : R) (Finsupp.single i k) _, C_1, one_mul, Finsupp.prod_single_index]
at this
exact pow_zero _
#align mv_polynomial.coeff_X_pow MvPolynomial.coeff_X_pow
theorem coeff_X' [DecidableEq σ] (i : σ) (m) :
coeff m (X i : MvPolynomial σ R) = if Finsupp.single i 1 = m then 1 else 0 := by
rw [← coeff_X_pow, pow_one]
#align mv_polynomial.coeff_X' MvPolynomial.coeff_X'
@[simp]
theorem coeff_X (i : σ) : coeff (Finsupp.single i 1) (X i : MvPolynomial σ R) = 1 := by
classical rw [coeff_X', if_pos rfl]
#align mv_polynomial.coeff_X MvPolynomial.coeff_X
@[simp]
theorem coeff_C_mul (m) (a : R) (p : MvPolynomial σ R) : coeff m (C a * p) = a * coeff m p := by
classical
rw [mul_def, sum_C]
· simp (config := { contextual := true }) [sum_def, coeff_sum]
simp
#align mv_polynomial.coeff_C_mul MvPolynomial.coeff_C_mul
theorem coeff_mul [DecidableEq σ] (p q : MvPolynomial σ R) (n : σ →₀ ℕ) :
coeff n (p * q) = ∑ x ∈ Finset.antidiagonal n, coeff x.1 p * coeff x.2 q :=
AddMonoidAlgebra.mul_apply_antidiagonal p q _ _ Finset.mem_antidiagonal
#align mv_polynomial.coeff_mul MvPolynomial.coeff_mul
@[simp]
theorem coeff_mul_monomial (m) (s : σ →₀ ℕ) (r : R) (p : MvPolynomial σ R) :
coeff (m + s) (p * monomial s r) = coeff m p * r :=
AddMonoidAlgebra.mul_single_apply_aux p _ _ _ _ fun _a => add_left_inj _
#align mv_polynomial.coeff_mul_monomial MvPolynomial.coeff_mul_monomial
@[simp]
theorem coeff_monomial_mul (m) (s : σ →₀ ℕ) (r : R) (p : MvPolynomial σ R) :
coeff (s + m) (monomial s r * p) = r * coeff m p :=
AddMonoidAlgebra.single_mul_apply_aux p _ _ _ _ fun _a => add_right_inj _
#align mv_polynomial.coeff_monomial_mul MvPolynomial.coeff_monomial_mul
@[simp]
theorem coeff_mul_X (m) (s : σ) (p : MvPolynomial σ R) :
coeff (m + Finsupp.single s 1) (p * X s) = coeff m p :=
(coeff_mul_monomial _ _ _ _).trans (mul_one _)
#align mv_polynomial.coeff_mul_X MvPolynomial.coeff_mul_X
@[simp]
theorem coeff_X_mul (m) (s : σ) (p : MvPolynomial σ R) :
coeff (Finsupp.single s 1 + m) (X s * p) = coeff m p :=
(coeff_monomial_mul _ _ _ _).trans (one_mul _)
#align mv_polynomial.coeff_X_mul MvPolynomial.coeff_X_mul
lemma coeff_single_X_pow [DecidableEq σ] (s s' : σ) (n n' : ℕ) :
(X (R := R) s ^ n).coeff (Finsupp.single s' n')
= if s = s' ∧ n = n' ∨ n = 0 ∧ n' = 0 then 1 else 0 := by
simp only [coeff_X_pow, single_eq_single_iff]
@[simp]
lemma coeff_single_X [DecidableEq σ] (s s' : σ) (n : ℕ) :
(X s).coeff (R := R) (Finsupp.single s' n) = if n = 1 ∧ s = s' then 1 else 0 := by
simpa [eq_comm, and_comm] using coeff_single_X_pow s s' 1 n
@[simp]
theorem support_mul_X (s : σ) (p : MvPolynomial σ R) :
(p * X s).support = p.support.map (addRightEmbedding (Finsupp.single s 1)) :=
AddMonoidAlgebra.support_mul_single p _ (by simp) _
#align mv_polynomial.support_mul_X MvPolynomial.support_mul_X
@[simp]
theorem support_X_mul (s : σ) (p : MvPolynomial σ R) :
(X s * p).support = p.support.map (addLeftEmbedding (Finsupp.single s 1)) :=
AddMonoidAlgebra.support_single_mul p _ (by simp) _
#align mv_polynomial.support_X_mul MvPolynomial.support_X_mul
@[simp]
theorem support_smul_eq {S₁ : Type*} [Semiring S₁] [Module S₁ R] [NoZeroSMulDivisors S₁ R] {a : S₁}
(h : a ≠ 0) (p : MvPolynomial σ R) : (a • p).support = p.support :=
Finsupp.support_smul_eq h
#align mv_polynomial.support_smul_eq MvPolynomial.support_smul_eq
theorem support_sdiff_support_subset_support_add [DecidableEq σ] (p q : MvPolynomial σ R) :
p.support \ q.support ⊆ (p + q).support := by
intro m hm
simp only [Classical.not_not, mem_support_iff, Finset.mem_sdiff, Ne] at hm
simp [hm.2, hm.1]
#align mv_polynomial.support_sdiff_support_subset_support_add MvPolynomial.support_sdiff_support_subset_support_add
open scoped symmDiff in
theorem support_symmDiff_support_subset_support_add [DecidableEq σ] (p q : MvPolynomial σ R) :
p.support ∆ q.support ⊆ (p + q).support := by
rw [symmDiff_def, Finset.sup_eq_union]
apply Finset.union_subset
· exact support_sdiff_support_subset_support_add p q
· rw [add_comm]
exact support_sdiff_support_subset_support_add q p
#align mv_polynomial.support_symm_diff_support_subset_support_add MvPolynomial.support_symmDiff_support_subset_support_add
theorem coeff_mul_monomial' (m) (s : σ →₀ ℕ) (r : R) (p : MvPolynomial σ R) :
coeff m (p * monomial s r) = if s ≤ m then coeff (m - s) p * r else 0 := by
classical
split_ifs with h
· conv_rhs => rw [← coeff_mul_monomial _ s]
congr with t
rw [tsub_add_cancel_of_le h]
· contrapose! h
rw [← mem_support_iff] at h
obtain ⟨j, -, rfl⟩ : ∃ j ∈ support p, j + s = m := by
simpa [Finset.add_singleton]
using Finset.add_subset_add_left support_monomial_subset <| support_mul _ _ h
exact le_add_left le_rfl
#align mv_polynomial.coeff_mul_monomial' MvPolynomial.coeff_mul_monomial'
theorem coeff_monomial_mul' (m) (s : σ →₀ ℕ) (r : R) (p : MvPolynomial σ R) :
coeff m (monomial s r * p) = if s ≤ m then r * coeff (m - s) p else 0 := by
-- note that if we allow `R` to be non-commutative we will have to duplicate the proof above.
rw [mul_comm, mul_comm r]
exact coeff_mul_monomial' _ _ _ _
#align mv_polynomial.coeff_monomial_mul' MvPolynomial.coeff_monomial_mul'
theorem coeff_mul_X' [DecidableEq σ] (m) (s : σ) (p : MvPolynomial σ R) :
coeff m (p * X s) = if s ∈ m.support then coeff (m - Finsupp.single s 1) p else 0 := by
refine (coeff_mul_monomial' _ _ _ _).trans ?_
simp_rw [Finsupp.single_le_iff, Finsupp.mem_support_iff, Nat.succ_le_iff, pos_iff_ne_zero,
mul_one]
#align mv_polynomial.coeff_mul_X' MvPolynomial.coeff_mul_X'
theorem coeff_X_mul' [DecidableEq σ] (m) (s : σ) (p : MvPolynomial σ R) :
coeff m (X s * p) = if s ∈ m.support then coeff (m - Finsupp.single s 1) p else 0 := by
refine (coeff_monomial_mul' _ _ _ _).trans ?_
simp_rw [Finsupp.single_le_iff, Finsupp.mem_support_iff, Nat.succ_le_iff, pos_iff_ne_zero,
one_mul]
#align mv_polynomial.coeff_X_mul' MvPolynomial.coeff_X_mul'
theorem eq_zero_iff {p : MvPolynomial σ R} : p = 0 ↔ ∀ d, coeff d p = 0 := by
rw [ext_iff]
simp only [coeff_zero]
#align mv_polynomial.eq_zero_iff MvPolynomial.eq_zero_iff
theorem ne_zero_iff {p : MvPolynomial σ R} : p ≠ 0 ↔ ∃ d, coeff d p ≠ 0 := by
rw [Ne, eq_zero_iff]
push_neg
rfl
#align mv_polynomial.ne_zero_iff MvPolynomial.ne_zero_iff
@[simp]
theorem X_ne_zero [Nontrivial R] (s : σ) :
X (R := R) s ≠ 0 := by
rw [ne_zero_iff]
use Finsupp.single s 1
simp only [coeff_X, ne_eq, one_ne_zero, not_false_eq_true]
@[simp]
theorem support_eq_empty {p : MvPolynomial σ R} : p.support = ∅ ↔ p = 0 :=
Finsupp.support_eq_empty
#align mv_polynomial.support_eq_empty MvPolynomial.support_eq_empty
@[simp]
lemma support_nonempty {p : MvPolynomial σ R} : p.support.Nonempty ↔ p ≠ 0 := by
rw [Finset.nonempty_iff_ne_empty, ne_eq, support_eq_empty]
theorem exists_coeff_ne_zero {p : MvPolynomial σ R} (h : p ≠ 0) : ∃ d, coeff d p ≠ 0 :=
ne_zero_iff.mp h
#align mv_polynomial.exists_coeff_ne_zero MvPolynomial.exists_coeff_ne_zero
theorem C_dvd_iff_dvd_coeff (r : R) (φ : MvPolynomial σ R) : C r ∣ φ ↔ ∀ i, r ∣ φ.coeff i := by
constructor
· rintro ⟨φ, rfl⟩ c
rw [coeff_C_mul]
apply dvd_mul_right
· intro h
choose C hc using h
classical
let c' : (σ →₀ ℕ) → R := fun i => if i ∈ φ.support then C i else 0
let ψ : MvPolynomial σ R := ∑ i ∈ φ.support, monomial i (c' i)
use ψ
apply MvPolynomial.ext
intro i
simp only [ψ, c', coeff_C_mul, coeff_sum, coeff_monomial, Finset.sum_ite_eq']
split_ifs with hi
· rw [hc]
· rw [not_mem_support_iff] at hi
rwa [mul_zero]
#align mv_polynomial.C_dvd_iff_dvd_coeff MvPolynomial.C_dvd_iff_dvd_coeff
@[simp] lemma isRegular_X : IsRegular (X n : MvPolynomial σ R) := by
suffices IsLeftRegular (X n : MvPolynomial σ R) from
⟨this, this.right_of_commute <| Commute.all _⟩
intro P Q (hPQ : (X n) * P = (X n) * Q)
ext i
rw [← coeff_X_mul i n P, hPQ, coeff_X_mul i n Q]
@[simp] lemma isRegular_X_pow (k : ℕ) : IsRegular (X n ^ k : MvPolynomial σ R) := isRegular_X.pow k
@[simp] lemma isRegular_prod_X (s : Finset σ) :
IsRegular (∏ n ∈ s, X n : MvPolynomial σ R) :=
IsRegular.prod fun _ _ ↦ isRegular_X
/-- The finset of nonzero coefficients of a multivariate polynomial. -/
def coeffs (p : MvPolynomial σ R) : Finset R :=
letI := Classical.decEq R
Finset.image p.coeff p.support
@[simp]
lemma coeffs_zero : coeffs (0 : MvPolynomial σ R) = ∅ :=
rfl
lemma coeffs_one : coeffs (1 : MvPolynomial σ R) ⊆ {1} := by
classical
rw [coeffs, Finset.image_subset_iff]
simp_all [coeff_one]
@[nontriviality]
lemma coeffs_eq_empty_of_subsingleton [Subsingleton R] (p : MvPolynomial σ R) : p.coeffs = ∅ := by
simpa [coeffs] using Subsingleton.eq_zero p
@[simp]
lemma coeffs_one_of_nontrivial [Nontrivial R] : coeffs (1 : MvPolynomial σ R) = {1} := by
apply Finset.Subset.antisymm coeffs_one
simp only [coeffs, Finset.singleton_subset_iff, Finset.mem_image]
exact ⟨0, by simp⟩
lemma mem_coeffs_iff {p : MvPolynomial σ R} {c : R} :
c ∈ p.coeffs ↔ ∃ n ∈ p.support, c = p.coeff n := by
simp [coeffs, eq_comm, (Finset.mem_image)]
lemma coeff_mem_coeffs {p : MvPolynomial σ R} (m : σ →₀ ℕ)
(h : p.coeff m ≠ 0) : p.coeff m ∈ p.coeffs :=
letI := Classical.decEq R
Finset.mem_image_of_mem p.coeff (mem_support_iff.mpr h)
lemma zero_not_mem_coeffs (p : MvPolynomial σ R) : 0 ∉ p.coeffs := by
intro hz
obtain ⟨n, hnsupp, hn⟩ := mem_coeffs_iff.mp hz
exact (mem_support_iff.mp hnsupp) hn.symm
end Coeff
section ConstantCoeff
/-- `constantCoeff p` returns the constant term of the polynomial `p`, defined as `coeff 0 p`.
This is a ring homomorphism.
-/
def constantCoeff : MvPolynomial σ R →+* R where
toFun := coeff 0
map_one' := by simp [AddMonoidAlgebra.one_def]
map_mul' := by classical simp [coeff_mul, Finsupp.support_single_ne_zero]
map_zero' := coeff_zero _
map_add' := coeff_add _
#align mv_polynomial.constant_coeff MvPolynomial.constantCoeff
theorem constantCoeff_eq : (constantCoeff : MvPolynomial σ R → R) = coeff 0 :=
rfl
#align mv_polynomial.constant_coeff_eq MvPolynomial.constantCoeff_eq
variable (σ)
@[simp]
| Mathlib/Algebra/MvPolynomial/Basic.lean | 955 | 956 | theorem constantCoeff_C (r : R) : constantCoeff (C r : MvPolynomial σ R) = r := by |
classical simp [constantCoeff_eq]
|
/-
Copyright (c) 2016 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Mario Carneiro
-/
import Mathlib.Logic.Nonempty
import Mathlib.Init.Set
import Mathlib.Logic.Basic
#align_import logic.function.basic from "leanprover-community/mathlib"@"29cb56a7b35f72758b05a30490e1f10bd62c35c1"
/-!
# Miscellaneous function constructions and lemmas
-/
open Function
universe u v w
namespace Function
section
variable {α β γ : Sort*} {f : α → β}
/-- Evaluate a function at an argument. Useful if you want to talk about the partially applied
`Function.eval x : (∀ x, β x) → β x`. -/
@[reducible, simp] def eval {β : α → Sort*} (x : α) (f : ∀ x, β x) : β x := f x
#align function.eval Function.eval
theorem eval_apply {β : α → Sort*} (x : α) (f : ∀ x, β x) : eval x f = f x :=
rfl
#align function.eval_apply Function.eval_apply
theorem const_def {y : β} : (fun _ : α ↦ y) = const α y :=
rfl
#align function.const_def Function.const_def
theorem const_injective [Nonempty α] : Injective (const α : β → α → β) := fun y₁ y₂ h ↦
let ⟨x⟩ := ‹Nonempty α›
congr_fun h x
#align function.const_injective Function.const_injective
@[simp]
theorem const_inj [Nonempty α] {y₁ y₂ : β} : const α y₁ = const α y₂ ↔ y₁ = y₂ :=
⟨fun h ↦ const_injective h, fun h ↦ h ▸ rfl⟩
#align function.const_inj Function.const_inj
#align function.id_def Function.id_def
-- Porting note: `Function.onFun` is now reducible
-- @[simp]
theorem onFun_apply (f : β → β → γ) (g : α → β) (a b : α) : onFun f g a b = f (g a) (g b) :=
rfl
#align function.on_fun_apply Function.onFun_apply
lemma hfunext {α α' : Sort u} {β : α → Sort v} {β' : α' → Sort v} {f : ∀a, β a} {f' : ∀a, β' a}
(hα : α = α') (h : ∀a a', HEq a a' → HEq (f a) (f' a')) : HEq f f' := by
subst hα
have : ∀a, HEq (f a) (f' a) := fun a ↦ h a a (HEq.refl a)
have : β = β' := by funext a; exact type_eq_of_heq (this a)
subst this
apply heq_of_eq
funext a
exact eq_of_heq (this a)
#align function.hfunext Function.hfunext
#align function.funext_iff Function.funext_iff
theorem ne_iff {β : α → Sort*} {f₁ f₂ : ∀ a, β a} : f₁ ≠ f₂ ↔ ∃ a, f₁ a ≠ f₂ a :=
funext_iff.not.trans not_forall
#align function.ne_iff Function.ne_iff
lemma funext_iff_of_subsingleton [Subsingleton α] {g : α → β} (x y : α) :
f x = g y ↔ f = g := by
refine ⟨fun h ↦ funext fun z ↦ ?_, fun h ↦ ?_⟩
· rwa [Subsingleton.elim x z, Subsingleton.elim y z] at h
· rw [h, Subsingleton.elim x y]
protected theorem Bijective.injective {f : α → β} (hf : Bijective f) : Injective f := hf.1
#align function.bijective.injective Function.Bijective.injective
protected theorem Bijective.surjective {f : α → β} (hf : Bijective f) : Surjective f := hf.2
#align function.bijective.surjective Function.Bijective.surjective
theorem Injective.eq_iff (I : Injective f) {a b : α} : f a = f b ↔ a = b :=
⟨@I _ _, congr_arg f⟩
#align function.injective.eq_iff Function.Injective.eq_iff
theorem Injective.beq_eq {α β : Type*} [BEq α] [LawfulBEq α] [BEq β] [LawfulBEq β] {f : α → β}
(I : Injective f) {a b : α} : (f a == f b) = (a == b) := by
by_cases h : a == b <;> simp [h] <;> simpa [I.eq_iff] using h
theorem Injective.eq_iff' (I : Injective f) {a b : α} {c : β} (h : f b = c) : f a = c ↔ a = b :=
h ▸ I.eq_iff
#align function.injective.eq_iff' Function.Injective.eq_iff'
theorem Injective.ne (hf : Injective f) {a₁ a₂ : α} : a₁ ≠ a₂ → f a₁ ≠ f a₂ :=
mt fun h ↦ hf h
#align function.injective.ne Function.Injective.ne
theorem Injective.ne_iff (hf : Injective f) {x y : α} : f x ≠ f y ↔ x ≠ y :=
⟨mt <| congr_arg f, hf.ne⟩
#align function.injective.ne_iff Function.Injective.ne_iff
theorem Injective.ne_iff' (hf : Injective f) {x y : α} {z : β} (h : f y = z) : f x ≠ z ↔ x ≠ y :=
h ▸ hf.ne_iff
#align function.injective.ne_iff' Function.Injective.ne_iff'
theorem not_injective_iff : ¬ Injective f ↔ ∃ a b, f a = f b ∧ a ≠ b := by
simp only [Injective, not_forall, exists_prop]
/-- If the co-domain `β` of an injective function `f : α → β` has decidable equality, then
the domain `α` also has decidable equality. -/
protected def Injective.decidableEq [DecidableEq β] (I : Injective f) : DecidableEq α :=
fun _ _ ↦ decidable_of_iff _ I.eq_iff
#align function.injective.decidable_eq Function.Injective.decidableEq
theorem Injective.of_comp {g : γ → α} (I : Injective (f ∘ g)) : Injective g :=
fun _ _ h ↦ I <| congr_arg f h
#align function.injective.of_comp Function.Injective.of_comp
@[simp]
theorem Injective.of_comp_iff (hf : Injective f) (g : γ → α) :
Injective (f ∘ g) ↔ Injective g :=
⟨Injective.of_comp, hf.comp⟩
#align function.injective.of_comp_iff Function.Injective.of_comp_iff
theorem Injective.of_comp_right {g : γ → α} (I : Injective (f ∘ g)) (hg : Surjective g) :
Injective f := fun x y h ↦ by
obtain ⟨x, rfl⟩ := hg x
obtain ⟨y, rfl⟩ := hg y
exact congr_arg g (I h)
theorem Surjective.bijective₂_of_injective {g : γ → α} (hf : Surjective f) (hg : Surjective g)
(I : Injective (f ∘ g)) : Bijective f ∧ Bijective g :=
⟨⟨I.of_comp_right hg, hf⟩, I.of_comp, hg⟩
@[simp]
theorem Injective.of_comp_iff' (f : α → β) {g : γ → α} (hg : Bijective g) :
Injective (f ∘ g) ↔ Injective f :=
⟨fun I ↦ I.of_comp_right hg.2, fun h ↦ h.comp hg.injective⟩
#align function.injective.of_comp_iff' Function.Injective.of_comp_iff'
/-- Composition by an injective function on the left is itself injective. -/
theorem Injective.comp_left {g : β → γ} (hg : Function.Injective g) :
Function.Injective (g ∘ · : (α → β) → α → γ) :=
fun _ _ hgf ↦ funext fun i ↦ hg <| (congr_fun hgf i : _)
#align function.injective.comp_left Function.Injective.comp_left
theorem injective_of_subsingleton [Subsingleton α] (f : α → β) : Injective f :=
fun _ _ _ ↦ Subsingleton.elim _ _
#align function.injective_of_subsingleton Function.injective_of_subsingleton
lemma Injective.dite (p : α → Prop) [DecidablePred p]
{f : {a : α // p a} → β} {f' : {a : α // ¬ p a} → β}
(hf : Injective f) (hf' : Injective f')
(im_disj : ∀ {x x' : α} {hx : p x} {hx' : ¬ p x'}, f ⟨x, hx⟩ ≠ f' ⟨x', hx'⟩) :
Function.Injective (fun x ↦ if h : p x then f ⟨x, h⟩ else f' ⟨x, h⟩) := fun x₁ x₂ h => by
dsimp only at h
by_cases h₁ : p x₁ <;> by_cases h₂ : p x₂
· rw [dif_pos h₁, dif_pos h₂] at h; injection (hf h)
· rw [dif_pos h₁, dif_neg h₂] at h; exact (im_disj h).elim
· rw [dif_neg h₁, dif_pos h₂] at h; exact (im_disj h.symm).elim
· rw [dif_neg h₁, dif_neg h₂] at h; injection (hf' h)
#align function.injective.dite Function.Injective.dite
theorem Surjective.of_comp {g : γ → α} (S : Surjective (f ∘ g)) : Surjective f := fun y ↦
let ⟨x, h⟩ := S y
⟨g x, h⟩
#align function.surjective.of_comp Function.Surjective.of_comp
@[simp]
theorem Surjective.of_comp_iff (f : α → β) {g : γ → α} (hg : Surjective g) :
Surjective (f ∘ g) ↔ Surjective f :=
⟨Surjective.of_comp, fun h ↦ h.comp hg⟩
#align function.surjective.of_comp_iff Function.Surjective.of_comp_iff
theorem Surjective.of_comp_left {g : γ → α} (S : Surjective (f ∘ g)) (hf : Injective f) :
Surjective g := fun a ↦ let ⟨c, hc⟩ := S (f a); ⟨c, hf hc⟩
theorem Injective.bijective₂_of_surjective {g : γ → α} (hf : Injective f) (hg : Injective g)
(S : Surjective (f ∘ g)) : Bijective f ∧ Bijective g :=
⟨⟨hf, S.of_comp⟩, hg, S.of_comp_left hf⟩
@[simp]
theorem Surjective.of_comp_iff' (hf : Bijective f) (g : γ → α) :
Surjective (f ∘ g) ↔ Surjective g :=
⟨fun S ↦ S.of_comp_left hf.1, hf.surjective.comp⟩
#align function.surjective.of_comp_iff' Function.Surjective.of_comp_iff'
instance decidableEqPFun (p : Prop) [Decidable p] (α : p → Type*) [∀ hp, DecidableEq (α hp)] :
DecidableEq (∀ hp, α hp)
| f, g => decidable_of_iff (∀ hp, f hp = g hp) funext_iff.symm
protected theorem Surjective.forall (hf : Surjective f) {p : β → Prop} :
(∀ y, p y) ↔ ∀ x, p (f x) :=
⟨fun h x ↦ h (f x), fun h y ↦
let ⟨x, hx⟩ := hf y
hx ▸ h x⟩
#align function.surjective.forall Function.Surjective.forall
protected theorem Surjective.forall₂ (hf : Surjective f) {p : β → β → Prop} :
(∀ y₁ y₂, p y₁ y₂) ↔ ∀ x₁ x₂, p (f x₁) (f x₂) :=
hf.forall.trans <| forall_congr' fun _ ↦ hf.forall
#align function.surjective.forall₂ Function.Surjective.forall₂
protected theorem Surjective.forall₃ (hf : Surjective f) {p : β → β → β → Prop} :
(∀ y₁ y₂ y₃, p y₁ y₂ y₃) ↔ ∀ x₁ x₂ x₃, p (f x₁) (f x₂) (f x₃) :=
hf.forall.trans <| forall_congr' fun _ ↦ hf.forall₂
#align function.surjective.forall₃ Function.Surjective.forall₃
protected theorem Surjective.exists (hf : Surjective f) {p : β → Prop} :
(∃ y, p y) ↔ ∃ x, p (f x) :=
⟨fun ⟨y, hy⟩ ↦
let ⟨x, hx⟩ := hf y
⟨x, hx.symm ▸ hy⟩,
fun ⟨x, hx⟩ ↦ ⟨f x, hx⟩⟩
#align function.surjective.exists Function.Surjective.exists
protected theorem Surjective.exists₂ (hf : Surjective f) {p : β → β → Prop} :
(∃ y₁ y₂, p y₁ y₂) ↔ ∃ x₁ x₂, p (f x₁) (f x₂) :=
hf.exists.trans <| exists_congr fun _ ↦ hf.exists
#align function.surjective.exists₂ Function.Surjective.exists₂
protected theorem Surjective.exists₃ (hf : Surjective f) {p : β → β → β → Prop} :
(∃ y₁ y₂ y₃, p y₁ y₂ y₃) ↔ ∃ x₁ x₂ x₃, p (f x₁) (f x₂) (f x₃) :=
hf.exists.trans <| exists_congr fun _ ↦ hf.exists₂
#align function.surjective.exists₃ Function.Surjective.exists₃
theorem Surjective.injective_comp_right (hf : Surjective f) : Injective fun g : β → γ ↦ g ∘ f :=
fun _ _ h ↦ funext <| hf.forall.2 <| congr_fun h
#align function.surjective.injective_comp_right Function.Surjective.injective_comp_right
protected theorem Surjective.right_cancellable (hf : Surjective f) {g₁ g₂ : β → γ} :
g₁ ∘ f = g₂ ∘ f ↔ g₁ = g₂ :=
hf.injective_comp_right.eq_iff
#align function.surjective.right_cancellable Function.Surjective.right_cancellable
theorem surjective_of_right_cancellable_Prop (h : ∀ g₁ g₂ : β → Prop, g₁ ∘ f = g₂ ∘ f → g₁ = g₂) :
Surjective f := by
specialize h (fun y ↦ ∃ x, f x = y) (fun _ ↦ True) (funext fun x ↦ eq_true ⟨_, rfl⟩)
intro y; rw [congr_fun h y]; trivial
#align function.surjective_of_right_cancellable_Prop Function.surjective_of_right_cancellable_Prop
theorem bijective_iff_existsUnique (f : α → β) : Bijective f ↔ ∀ b : β, ∃! a : α, f a = b :=
⟨fun hf b ↦
let ⟨a, ha⟩ := hf.surjective b
⟨a, ha, fun _ ha' ↦ hf.injective (ha'.trans ha.symm)⟩,
fun he ↦ ⟨fun {_a a'} h ↦ (he (f a')).unique h rfl, fun b ↦ (he b).exists⟩⟩
#align function.bijective_iff_exists_unique Function.bijective_iff_existsUnique
/-- Shorthand for using projection notation with `Function.bijective_iff_existsUnique`. -/
protected theorem Bijective.existsUnique {f : α → β} (hf : Bijective f) (b : β) :
∃! a : α, f a = b :=
(bijective_iff_existsUnique f).mp hf b
#align function.bijective.exists_unique Function.Bijective.existsUnique
theorem Bijective.existsUnique_iff {f : α → β} (hf : Bijective f) {p : β → Prop} :
(∃! y, p y) ↔ ∃! x, p (f x) :=
⟨fun ⟨y, hpy, hy⟩ ↦
let ⟨x, hx⟩ := hf.surjective y
⟨x, by simpa [hx], fun z (hz : p (f z)) ↦ hf.injective <| hx.symm ▸ hy _ hz⟩,
fun ⟨x, hpx, hx⟩ ↦
⟨f x, hpx, fun y hy ↦
let ⟨z, hz⟩ := hf.surjective y
hz ▸ congr_arg f (hx _ (by simpa [hz]))⟩⟩
#align function.bijective.exists_unique_iff Function.Bijective.existsUnique_iff
theorem Bijective.of_comp_iff (f : α → β) {g : γ → α} (hg : Bijective g) :
Bijective (f ∘ g) ↔ Bijective f :=
and_congr (Injective.of_comp_iff' _ hg) (Surjective.of_comp_iff _ hg.surjective)
#align function.bijective.of_comp_iff Function.Bijective.of_comp_iff
theorem Bijective.of_comp_iff' {f : α → β} (hf : Bijective f) (g : γ → α) :
Function.Bijective (f ∘ g) ↔ Function.Bijective g :=
and_congr (Injective.of_comp_iff hf.injective _) (Surjective.of_comp_iff' hf _)
#align function.bijective.of_comp_iff' Function.Bijective.of_comp_iff'
/-- **Cantor's diagonal argument** implies that there are no surjective functions from `α`
to `Set α`. -/
theorem cantor_surjective {α} (f : α → Set α) : ¬Surjective f
| h => let ⟨D, e⟩ := h {a | ¬ f a a}
@iff_not_self (D ∈ f D) <| iff_of_eq <| congr_arg (D ∈ ·) e
#align function.cantor_surjective Function.cantor_surjective
/-- **Cantor's diagonal argument** implies that there are no injective functions from `Set α`
to `α`. -/
theorem cantor_injective {α : Type*} (f : Set α → α) : ¬Injective f
| i => cantor_surjective (fun a ↦ {b | ∀ U, a = f U → U b}) <|
RightInverse.surjective (fun U ↦ Set.ext fun _ ↦ ⟨fun h ↦ h U rfl, fun h _ e ↦ i e ▸ h⟩)
#align function.cantor_injective Function.cantor_injective
/-- There is no surjection from `α : Type u` into `Type (max u v)`. This theorem
demonstrates why `Type : Type` would be inconsistent in Lean. -/
theorem not_surjective_Type {α : Type u} (f : α → Type max u v) : ¬Surjective f := by
intro hf
let T : Type max u v := Sigma f
cases hf (Set T) with | intro U hU =>
let g : Set T → T := fun s ↦ ⟨U, cast hU.symm s⟩
have hg : Injective g := by
intro s t h
suffices cast hU (g s).2 = cast hU (g t).2 by
simp only [cast_cast, cast_eq] at this
assumption
· congr
exact cantor_injective g hg
#align function.not_surjective_Type Function.not_surjective_Type
/-- `g` is a partial inverse to `f` (an injective but not necessarily
surjective function) if `g y = some x` implies `f x = y`, and `g y = none`
implies that `y` is not in the range of `f`. -/
def IsPartialInv {α β} (f : α → β) (g : β → Option α) : Prop :=
∀ x y, g y = some x ↔ f x = y
#align function.is_partial_inv Function.IsPartialInv
theorem isPartialInv_left {α β} {f : α → β} {g} (H : IsPartialInv f g) (x) : g (f x) = some x :=
(H _ _).2 rfl
#align function.is_partial_inv_left Function.isPartialInv_left
theorem injective_of_isPartialInv {α β} {f : α → β} {g} (H : IsPartialInv f g) :
Injective f := fun _ _ h ↦
Option.some.inj <| ((H _ _).2 h).symm.trans ((H _ _).2 rfl)
#align function.injective_of_partial_inv Function.injective_of_isPartialInv
theorem injective_of_isPartialInv_right {α β} {f : α → β} {g} (H : IsPartialInv f g) (x y b)
(h₁ : b ∈ g x) (h₂ : b ∈ g y) : x = y :=
((H _ _).1 h₁).symm.trans ((H _ _).1 h₂)
#align function.injective_of_partial_inv_right Function.injective_of_isPartialInv_right
theorem LeftInverse.comp_eq_id {f : α → β} {g : β → α} (h : LeftInverse f g) : f ∘ g = id :=
funext h
#align function.left_inverse.comp_eq_id Function.LeftInverse.comp_eq_id
theorem leftInverse_iff_comp {f : α → β} {g : β → α} : LeftInverse f g ↔ f ∘ g = id :=
⟨LeftInverse.comp_eq_id, congr_fun⟩
#align function.left_inverse_iff_comp Function.leftInverse_iff_comp
theorem RightInverse.comp_eq_id {f : α → β} {g : β → α} (h : RightInverse f g) : g ∘ f = id :=
funext h
#align function.right_inverse.comp_eq_id Function.RightInverse.comp_eq_id
theorem rightInverse_iff_comp {f : α → β} {g : β → α} : RightInverse f g ↔ g ∘ f = id :=
⟨RightInverse.comp_eq_id, congr_fun⟩
#align function.right_inverse_iff_comp Function.rightInverse_iff_comp
theorem LeftInverse.comp {f : α → β} {g : β → α} {h : β → γ} {i : γ → β} (hf : LeftInverse f g)
(hh : LeftInverse h i) : LeftInverse (h ∘ f) (g ∘ i) :=
fun a ↦ show h (f (g (i a))) = a by rw [hf (i a), hh a]
#align function.left_inverse.comp Function.LeftInverse.comp
theorem RightInverse.comp {f : α → β} {g : β → α} {h : β → γ} {i : γ → β} (hf : RightInverse f g)
(hh : RightInverse h i) : RightInverse (h ∘ f) (g ∘ i) :=
LeftInverse.comp hh hf
#align function.right_inverse.comp Function.RightInverse.comp
theorem LeftInverse.rightInverse {f : α → β} {g : β → α} (h : LeftInverse g f) : RightInverse f g :=
h
#align function.left_inverse.right_inverse Function.LeftInverse.rightInverse
theorem RightInverse.leftInverse {f : α → β} {g : β → α} (h : RightInverse g f) : LeftInverse f g :=
h
#align function.right_inverse.left_inverse Function.RightInverse.leftInverse
theorem LeftInverse.surjective {f : α → β} {g : β → α} (h : LeftInverse f g) : Surjective f :=
h.rightInverse.surjective
#align function.left_inverse.surjective Function.LeftInverse.surjective
theorem RightInverse.injective {f : α → β} {g : β → α} (h : RightInverse f g) : Injective f :=
h.leftInverse.injective
#align function.right_inverse.injective Function.RightInverse.injective
theorem LeftInverse.rightInverse_of_injective {f : α → β} {g : β → α} (h : LeftInverse f g)
(hf : Injective f) : RightInverse f g :=
fun x ↦ hf <| h (f x)
#align function.left_inverse.right_inverse_of_injective Function.LeftInverse.rightInverse_of_injective
theorem LeftInverse.rightInverse_of_surjective {f : α → β} {g : β → α} (h : LeftInverse f g)
(hg : Surjective g) : RightInverse f g :=
fun x ↦ let ⟨y, hy⟩ := hg x; hy ▸ congr_arg g (h y)
#align function.left_inverse.right_inverse_of_surjective Function.LeftInverse.rightInverse_of_surjective
theorem RightInverse.leftInverse_of_surjective {f : α → β} {g : β → α} :
RightInverse f g → Surjective f → LeftInverse f g :=
LeftInverse.rightInverse_of_surjective
#align function.right_inverse.left_inverse_of_surjective Function.RightInverse.leftInverse_of_surjective
theorem RightInverse.leftInverse_of_injective {f : α → β} {g : β → α} :
RightInverse f g → Injective g → LeftInverse f g :=
LeftInverse.rightInverse_of_injective
#align function.right_inverse.left_inverse_of_injective Function.RightInverse.leftInverse_of_injective
| Mathlib/Logic/Function/Basic.lean | 392 | 396 | theorem LeftInverse.eq_rightInverse {f : α → β} {g₁ g₂ : β → α} (h₁ : LeftInverse g₁ f)
(h₂ : RightInverse g₂ f) : g₁ = g₂ :=
calc
g₁ = g₁ ∘ f ∘ g₂ := by | rw [h₂.comp_eq_id, comp_id]
_ = g₂ := by rw [← comp.assoc, h₁.comp_eq_id, id_comp]
|
/-
Copyright (c) 2021 Aaron Anderson. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Aaron Anderson
-/
import Mathlib.Data.Int.Interval
import Mathlib.RingTheory.Binomial
import Mathlib.RingTheory.HahnSeries.PowerSeries
import Mathlib.RingTheory.HahnSeries.Summable
import Mathlib.FieldTheory.RatFunc.AsPolynomial
import Mathlib.RingTheory.Localization.FractionRing
#align_import ring_theory.laurent_series from "leanprover-community/mathlib"@"831c494092374cfe9f50591ed0ac81a25efc5b86"
/-!
# Laurent Series
## Main Definitions
* Defines `LaurentSeries` as an abbreviation for `HahnSeries ℤ`.
* Defines `hasseDeriv` of a Laurent series with coefficients in a module over a ring.
* Provides a coercion `PowerSeries R` into `LaurentSeries R` given by
`HahnSeries.ofPowerSeries`.
* Defines `LaurentSeries.powerSeriesPart`
* Defines the localization map `LaurentSeries.of_powerSeries_localization` which evaluates to
`HahnSeries.ofPowerSeries`.
* Embedding of rational functions into Laurent series, provided as a coercion, utilizing
the underlying `RatFunc.coeAlgHom`.
## Main Results
* Basic properties of Hasse derivatives
-/
universe u
open scoped Classical
open HahnSeries Polynomial
noncomputable section
/-- A `LaurentSeries` is implemented as a `HahnSeries` with value group `ℤ`. -/
abbrev LaurentSeries (R : Type u) [Zero R] :=
HahnSeries ℤ R
#align laurent_series LaurentSeries
variable {R : Type*}
namespace LaurentSeries
section HasseDeriv
/-- The Hasse derivative of Laurent series, as a linear map. -/
@[simps]
def hasseDeriv (R : Type*) {V : Type*} [AddCommGroup V] [Semiring R] [Module R V] (k : ℕ) :
LaurentSeries V →ₗ[R] LaurentSeries V where
toFun f := HahnSeries.ofSuppBddBelow (fun (n : ℤ) => (Ring.choose (n + k) k) • f.coeff (n + k))
(forallLTEqZero_supp_BddBelow _ (f.order - k : ℤ)
(fun _ h_lt ↦ by rw [coeff_eq_zero_of_lt_order <| lt_sub_iff_add_lt.mp h_lt, smul_zero]))
map_add' f g := by
ext
simp only [ofSuppBddBelow, add_coeff', Pi.add_apply, smul_add]
map_smul' r f := by
ext
simp only [ofSuppBddBelow, smul_coeff, RingHom.id_apply, smul_comm r]
variable [Semiring R] {V : Type*} [AddCommGroup V] [Module R V]
theorem hasseDeriv_coeff (k : ℕ) (f : LaurentSeries V) (n : ℤ) :
(hasseDeriv R k f).coeff n = Ring.choose (n + k) k • f.coeff (n + k) :=
rfl
end HasseDeriv
section Semiring
variable [Semiring R]
instance : Coe (PowerSeries R) (LaurentSeries R) :=
⟨HahnSeries.ofPowerSeries ℤ R⟩
/- Porting note: now a syntactic tautology and not needed elsewhere
theorem coe_powerSeries (x : PowerSeries R) :
(x : LaurentSeries R) = HahnSeries.ofPowerSeries ℤ R x :=
rfl -/
#noalign laurent_series.coe_power_series
@[simp]
theorem coeff_coe_powerSeries (x : PowerSeries R) (n : ℕ) :
HahnSeries.coeff (x : LaurentSeries R) n = PowerSeries.coeff R n x := by
rw [ofPowerSeries_apply_coeff]
#align laurent_series.coeff_coe_power_series LaurentSeries.coeff_coe_powerSeries
/-- This is a power series that can be multiplied by an integer power of `X` to give our
Laurent series. If the Laurent series is nonzero, `powerSeriesPart` has a nonzero
constant term. -/
def powerSeriesPart (x : LaurentSeries R) : PowerSeries R :=
PowerSeries.mk fun n => x.coeff (x.order + n)
#align laurent_series.power_series_part LaurentSeries.powerSeriesPart
@[simp]
theorem powerSeriesPart_coeff (x : LaurentSeries R) (n : ℕ) :
PowerSeries.coeff R n x.powerSeriesPart = x.coeff (x.order + n) :=
PowerSeries.coeff_mk _ _
#align laurent_series.power_series_part_coeff LaurentSeries.powerSeriesPart_coeff
@[simp]
theorem powerSeriesPart_zero : powerSeriesPart (0 : LaurentSeries R) = 0 := by
ext
simp [(PowerSeries.coeff _ _).map_zero] -- Note: this doesn't get picked up any more
#align laurent_series.power_series_part_zero LaurentSeries.powerSeriesPart_zero
@[simp]
theorem powerSeriesPart_eq_zero (x : LaurentSeries R) : x.powerSeriesPart = 0 ↔ x = 0 := by
constructor
· contrapose!
simp only [ne_eq]
intro h
rw [PowerSeries.ext_iff, not_forall]
refine ⟨0, ?_⟩
simp [coeff_order_ne_zero h]
· rintro rfl
simp
#align laurent_series.power_series_part_eq_zero LaurentSeries.powerSeriesPart_eq_zero
@[simp]
theorem single_order_mul_powerSeriesPart (x : LaurentSeries R) :
(single x.order 1 : LaurentSeries R) * x.powerSeriesPart = x := by
ext n
rw [← sub_add_cancel n x.order, single_mul_coeff_add, sub_add_cancel, one_mul]
by_cases h : x.order ≤ n
· rw [Int.eq_natAbs_of_zero_le (sub_nonneg_of_le h), coeff_coe_powerSeries,
powerSeriesPart_coeff, ← Int.eq_natAbs_of_zero_le (sub_nonneg_of_le h),
add_sub_cancel]
· rw [ofPowerSeries_apply, embDomain_notin_range]
· contrapose! h
exact order_le_of_coeff_ne_zero h.symm
· contrapose! h
simp only [Set.mem_range, RelEmbedding.coe_mk, Function.Embedding.coeFn_mk] at h
obtain ⟨m, hm⟩ := h
rw [← sub_nonneg, ← hm]
simp only [Nat.cast_nonneg]
#align laurent_series.single_order_mul_power_series_part LaurentSeries.single_order_mul_powerSeriesPart
theorem ofPowerSeries_powerSeriesPart (x : LaurentSeries R) :
ofPowerSeries ℤ R x.powerSeriesPart = single (-x.order) 1 * x := by
refine Eq.trans ?_ (congr rfl x.single_order_mul_powerSeriesPart)
rw [← mul_assoc, single_mul_single, neg_add_self, mul_one, ← C_apply, C_one, one_mul]
#align laurent_series.of_power_series_power_series_part LaurentSeries.ofPowerSeries_powerSeriesPart
end Semiring
instance [CommSemiring R] : Algebra (PowerSeries R) (LaurentSeries R) :=
(HahnSeries.ofPowerSeries ℤ R).toAlgebra
@[simp]
theorem coe_algebraMap [CommSemiring R] :
⇑(algebraMap (PowerSeries R) (LaurentSeries R)) = HahnSeries.ofPowerSeries ℤ R :=
rfl
#align laurent_series.coe_algebra_map LaurentSeries.coe_algebraMap
/-- The localization map from power series to Laurent series. -/
@[simps (config := { rhsMd := .all, simpRhs := true })]
instance of_powerSeries_localization [CommRing R] :
IsLocalization (Submonoid.powers (PowerSeries.X : PowerSeries R)) (LaurentSeries R) where
map_units' := by
rintro ⟨_, n, rfl⟩
refine ⟨⟨single (n : ℤ) 1, single (-n : ℤ) 1, ?_, ?_⟩, ?_⟩
· simp only [single_mul_single, mul_one, add_right_neg]
rfl
· simp only [single_mul_single, mul_one, add_left_neg]
rfl
· dsimp; rw [ofPowerSeries_X_pow]
surj' z := by
by_cases h : 0 ≤ z.order
· refine ⟨⟨PowerSeries.X ^ Int.natAbs z.order * powerSeriesPart z, 1⟩, ?_⟩
simp only [RingHom.map_one, mul_one, RingHom.map_mul, coe_algebraMap, ofPowerSeries_X_pow,
Submonoid.coe_one]
rw [Int.natAbs_of_nonneg h, single_order_mul_powerSeriesPart]
· refine ⟨⟨powerSeriesPart z, PowerSeries.X ^ Int.natAbs z.order, ⟨_, rfl⟩⟩, ?_⟩
simp only [coe_algebraMap, ofPowerSeries_powerSeriesPart]
rw [mul_comm _ z]
refine congr rfl ?_
rw [ofPowerSeries_X_pow, Int.ofNat_natAbs_of_nonpos]
exact le_of_not_ge h
exists_of_eq {x y} := by
rw [coe_algebraMap, ofPowerSeries_injective.eq_iff]
rintro rfl
exact ⟨1, rfl⟩
#align laurent_series.of_power_series_localization LaurentSeries.of_powerSeries_localization
instance {K : Type*} [Field K] : IsFractionRing (PowerSeries K) (LaurentSeries K) :=
IsLocalization.of_le (Submonoid.powers (PowerSeries.X : PowerSeries K)) _
(powers_le_nonZeroDivisors_of_noZeroDivisors PowerSeries.X_ne_zero) fun _ hf =>
isUnit_of_mem_nonZeroDivisors <| map_mem_nonZeroDivisors _ HahnSeries.ofPowerSeries_injective hf
end LaurentSeries
namespace PowerSeries
open LaurentSeries
variable {R' : Type*} [Semiring R] [Ring R'] (f g : PowerSeries R) (f' g' : PowerSeries R')
@[norm_cast] -- Porting note (#10618): simp can prove this
theorem coe_zero : ((0 : PowerSeries R) : LaurentSeries R) = 0 :=
(ofPowerSeries ℤ R).map_zero
#align power_series.coe_zero PowerSeries.coe_zero
@[norm_cast] -- Porting note (#10618): simp can prove this
theorem coe_one : ((1 : PowerSeries R) : LaurentSeries R) = 1 :=
(ofPowerSeries ℤ R).map_one
#align power_series.coe_one PowerSeries.coe_one
@[norm_cast] -- Porting note (#10618): simp can prove this
theorem coe_add : ((f + g : PowerSeries R) : LaurentSeries R) = f + g :=
(ofPowerSeries ℤ R).map_add _ _
#align power_series.coe_add PowerSeries.coe_add
@[norm_cast]
theorem coe_sub : ((f' - g' : PowerSeries R') : LaurentSeries R') = f' - g' :=
(ofPowerSeries ℤ R').map_sub _ _
#align power_series.coe_sub PowerSeries.coe_sub
@[norm_cast]
theorem coe_neg : ((-f' : PowerSeries R') : LaurentSeries R') = -f' :=
(ofPowerSeries ℤ R').map_neg _
#align power_series.coe_neg PowerSeries.coe_neg
@[norm_cast] -- Porting note (#10618): simp can prove this
theorem coe_mul : ((f * g : PowerSeries R) : LaurentSeries R) = f * g :=
(ofPowerSeries ℤ R).map_mul _ _
#align power_series.coe_mul PowerSeries.coe_mul
theorem coeff_coe (i : ℤ) :
((f : PowerSeries R) : LaurentSeries R).coeff i =
if i < 0 then 0 else PowerSeries.coeff R i.natAbs f := by
cases i
· rw [Int.ofNat_eq_coe, coeff_coe_powerSeries, if_neg (Int.natCast_nonneg _).not_lt,
Int.natAbs_ofNat]
· rw [ofPowerSeries_apply, embDomain_notin_image_support, if_pos (Int.negSucc_lt_zero _)]
simp only [not_exists, RelEmbedding.coe_mk, Set.mem_image, not_and, Function.Embedding.coeFn_mk,
Ne, toPowerSeries_symm_apply_coeff, mem_support, imp_true_iff,
not_false_iff]
#align power_series.coeff_coe PowerSeries.coeff_coe
-- Porting note (#10618): simp can prove this
-- Porting note: removed norm_cast attribute
theorem coe_C (r : R) : ((C R r : PowerSeries R) : LaurentSeries R) = HahnSeries.C r :=
ofPowerSeries_C _
set_option linter.uppercaseLean3 false in
#align power_series.coe_C PowerSeries.coe_C
-- @[simp] -- Porting note (#10618): simp can prove this
theorem coe_X : ((X : PowerSeries R) : LaurentSeries R) = single 1 1 :=
ofPowerSeries_X
set_option linter.uppercaseLean3 false in
#align power_series.coe_X PowerSeries.coe_X
@[simp, norm_cast]
theorem coe_smul {S : Type*} [Semiring S] [Module R S] (r : R) (x : PowerSeries S) :
((r • x : PowerSeries S) : LaurentSeries S) = r • (ofPowerSeries ℤ S x) := by
ext
simp [coeff_coe, coeff_smul, smul_ite]
#align power_series.coe_smul PowerSeries.coe_smul
-- Porting note: RingHom.map_bit0 and RingHom.map_bit1 no longer exist
#noalign power_series.coe_bit0
#noalign power_series.coe_bit1
@[norm_cast]
theorem coe_pow (n : ℕ) : ((f ^ n : PowerSeries R) : LaurentSeries R) = (ofPowerSeries ℤ R f) ^ n :=
(ofPowerSeries ℤ R).map_pow _ _
#align power_series.coe_pow PowerSeries.coe_pow
end PowerSeries
namespace RatFunc
section RatFunc
open RatFunc
variable {F : Type u} [Field F] (p q : F[X]) (f g : RatFunc F)
/-- The coercion `RatFunc F → LaurentSeries F` as bundled alg hom. -/
def coeAlgHom (F : Type u) [Field F] : RatFunc F →ₐ[F[X]] LaurentSeries F :=
liftAlgHom (Algebra.ofId _ _) <|
nonZeroDivisors_le_comap_nonZeroDivisors_of_injective _ <|
Polynomial.algebraMap_hahnSeries_injective _
#align ratfunc.coe_alg_hom RatFunc.coeAlgHom
/-- The coercion `RatFunc F → LaurentSeries F` as a function.
This is the implementation of `coeToLaurentSeries`.
-/
@[coe]
def coeToLaurentSeries_fun {F : Type u} [Field F] : RatFunc F → LaurentSeries F :=
coeAlgHom F
instance coeToLaurentSeries : Coe (RatFunc F) (LaurentSeries F) :=
⟨coeToLaurentSeries_fun⟩
#align ratfunc.coe_to_laurent_series RatFunc.coeToLaurentSeries
theorem coe_def : (f : LaurentSeries F) = coeAlgHom F f :=
rfl
#align ratfunc.coe_def RatFunc.coe_def
theorem coe_num_denom : (f : LaurentSeries F) = f.num / f.denom :=
liftAlgHom_apply _ _ f
#align ratfunc.coe_num_denom RatFunc.coe_num_denom
theorem coe_injective : Function.Injective ((↑) : RatFunc F → LaurentSeries F) :=
liftAlgHom_injective _ (Polynomial.algebraMap_hahnSeries_injective _)
#align ratfunc.coe_injective RatFunc.coe_injective
-- Porting note: removed the `norm_cast` tag:
-- `norm_cast: badly shaped lemma, rhs can't start with coe `↑(coeAlgHom F) f`
@[simp]
theorem coe_apply : coeAlgHom F f = f :=
rfl
#align ratfunc.coe_apply RatFunc.coe_apply
theorem coe_coe (P : Polynomial F) : (P : LaurentSeries F) = (P : RatFunc F) := by
simp only [coePolynomial, coe_def, AlgHom.commutes, algebraMap_hahnSeries_apply]
@[simp, norm_cast]
theorem coe_zero : ((0 : RatFunc F) : LaurentSeries F) = 0 :=
(coeAlgHom F).map_zero
#align ratfunc.coe_zero RatFunc.coe_zero
theorem coe_ne_zero {f : Polynomial F} (hf : f ≠ 0) : (↑f : PowerSeries F) ≠ 0 := by
simp only [ne_eq, Polynomial.coe_eq_zero_iff, hf, not_false_eq_true]
@[simp, norm_cast]
theorem coe_one : ((1 : RatFunc F) : LaurentSeries F) = 1 :=
(coeAlgHom F).map_one
#align ratfunc.coe_one RatFunc.coe_one
@[simp, norm_cast]
theorem coe_add : ((f + g : RatFunc F) : LaurentSeries F) = f + g :=
(coeAlgHom F).map_add _ _
#align ratfunc.coe_add RatFunc.coe_add
@[simp, norm_cast]
theorem coe_sub : ((f - g : RatFunc F) : LaurentSeries F) = f - g :=
(coeAlgHom F).map_sub _ _
#align ratfunc.coe_sub RatFunc.coe_sub
@[simp, norm_cast]
theorem coe_neg : ((-f : RatFunc F) : LaurentSeries F) = -f :=
(coeAlgHom F).map_neg _
#align ratfunc.coe_neg RatFunc.coe_neg
@[simp, norm_cast]
theorem coe_mul : ((f * g : RatFunc F) : LaurentSeries F) = f * g :=
(coeAlgHom F).map_mul _ _
#align ratfunc.coe_mul RatFunc.coe_mul
@[simp, norm_cast]
theorem coe_pow (n : ℕ) : ((f ^ n : RatFunc F) : LaurentSeries F) = (f : LaurentSeries F) ^ n :=
(coeAlgHom F).map_pow _ _
#align ratfunc.coe_pow RatFunc.coe_pow
@[simp, norm_cast]
theorem coe_div :
((f / g : RatFunc F) : LaurentSeries F) = (f : LaurentSeries F) / (g : LaurentSeries F) :=
map_div₀ (coeAlgHom F) _ _
#align ratfunc.coe_div RatFunc.coe_div
@[simp, norm_cast]
theorem coe_C (r : F) : ((RatFunc.C r : RatFunc F) : LaurentSeries F) = HahnSeries.C r := by
rw [coe_num_denom, num_C, denom_C, Polynomial.coe_C, -- Porting note: removed `coe_C`
Polynomial.coe_one,
PowerSeries.coe_one, div_one]
simp only [algebraMap_eq_C, ofPowerSeries_C, C_apply] -- Porting note: added
set_option linter.uppercaseLean3 false in
#align ratfunc.coe_C RatFunc.coe_C
-- TODO: generalize over other modules
@[simp, norm_cast]
theorem coe_smul (r : F) : ((r • f : RatFunc F) : LaurentSeries F) = r • (f : LaurentSeries F) := by
rw [RatFunc.smul_eq_C_mul, ← C_mul_eq_smul, coe_mul, coe_C]
#align ratfunc.coe_smul RatFunc.coe_smul
-- Porting note: removed `norm_cast` because "badly shaped lemma, rhs can't start with coe"
-- even though `single 1 1` is a bundled function application, not a "real" coercion
@[simp, nolint simpNF] -- Added `simpNF` to avoid timeout #8386
theorem coe_X : ((X : RatFunc F) : LaurentSeries F) = single 1 1 := by
rw [coe_num_denom, num_X, denom_X, Polynomial.coe_X, -- Porting note: removed `coe_C`
Polynomial.coe_one,
PowerSeries.coe_one, div_one]
simp only [ofPowerSeries_X] -- Porting note: added
set_option linter.uppercaseLean3 false in
#align ratfunc.coe_X RatFunc.coe_X
theorem single_one_eq_pow {R : Type _} [Ring R] (n : ℕ) :
single (n : ℤ) (1 : R) = single (1 : ℤ) 1 ^ n := by
induction' n with n h_ind
· simp only [Nat.cast_zero, pow_zero]
rfl
· rw [← Int.ofNat_add_one_out, pow_succ', ← h_ind, HahnSeries.single_mul_single, one_mul,
add_comm]
| Mathlib/RingTheory/LaurentSeries.lean | 402 | 407 | theorem single_inv (d : ℤ) {α : F} (hα : α ≠ 0) :
single (-d) (α⁻¹ : F) = (single (d : ℤ) (α : F))⁻¹ := by |
apply eq_inv_of_mul_eq_one_right
rw [HahnSeries.single_mul_single, add_right_neg, mul_comm,
inv_mul_cancel hα]
rfl
|
/-
Copyright (c) 2022 Scott Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Scott Morrison, Oleksandr Manzyuk
-/
import Mathlib.CategoryTheory.Bicategory.Basic
import Mathlib.CategoryTheory.Monoidal.Mon_
import Mathlib.CategoryTheory.Limits.Preserves.Shapes.Equalizers
#align_import category_theory.monoidal.Bimod from "leanprover-community/mathlib"@"4698e35ca56a0d4fa53aa5639c3364e0a77f4eba"
/-!
# The category of bimodule objects over a pair of monoid objects.
-/
universe v₁ v₂ u₁ u₂
open CategoryTheory
open CategoryTheory.MonoidalCategory
variable {C : Type u₁} [Category.{v₁} C] [MonoidalCategory.{v₁} C]
section
open CategoryTheory.Limits
variable [HasCoequalizers C]
section
variable [∀ X : C, PreservesColimitsOfSize.{0, 0} (tensorLeft X)]
theorem id_tensor_π_preserves_coequalizer_inv_desc {W X Y Z : C} (f g : X ⟶ Y) (h : Z ⊗ Y ⟶ W)
(wh : (Z ◁ f) ≫ h = (Z ◁ g) ≫ h) :
(Z ◁ coequalizer.π f g) ≫
(PreservesCoequalizer.iso (tensorLeft Z) f g).inv ≫ coequalizer.desc h wh =
h :=
map_π_preserves_coequalizer_inv_desc (tensorLeft Z) f g h wh
#align id_tensor_π_preserves_coequalizer_inv_desc id_tensor_π_preserves_coequalizer_inv_desc
theorem id_tensor_π_preserves_coequalizer_inv_colimMap_desc {X Y Z X' Y' Z' : C} (f g : X ⟶ Y)
(f' g' : X' ⟶ Y') (p : Z ⊗ X ⟶ X') (q : Z ⊗ Y ⟶ Y') (wf : (Z ◁ f) ≫ q = p ≫ f')
(wg : (Z ◁ g) ≫ q = p ≫ g') (h : Y' ⟶ Z') (wh : f' ≫ h = g' ≫ h) :
(Z ◁ coequalizer.π f g) ≫
(PreservesCoequalizer.iso (tensorLeft Z) f g).inv ≫
colimMap (parallelPairHom (Z ◁ f) (Z ◁ g) f' g' p q wf wg) ≫ coequalizer.desc h wh =
q ≫ h :=
map_π_preserves_coequalizer_inv_colimMap_desc (tensorLeft Z) f g f' g' p q wf wg h wh
#align id_tensor_π_preserves_coequalizer_inv_colim_map_desc id_tensor_π_preserves_coequalizer_inv_colimMap_desc
end
section
variable [∀ X : C, PreservesColimitsOfSize.{0, 0} (tensorRight X)]
theorem π_tensor_id_preserves_coequalizer_inv_desc {W X Y Z : C} (f g : X ⟶ Y) (h : Y ⊗ Z ⟶ W)
(wh : (f ▷ Z) ≫ h = (g ▷ Z) ≫ h) :
(coequalizer.π f g ▷ Z) ≫
(PreservesCoequalizer.iso (tensorRight Z) f g).inv ≫ coequalizer.desc h wh =
h :=
map_π_preserves_coequalizer_inv_desc (tensorRight Z) f g h wh
#align π_tensor_id_preserves_coequalizer_inv_desc π_tensor_id_preserves_coequalizer_inv_desc
theorem π_tensor_id_preserves_coequalizer_inv_colimMap_desc {X Y Z X' Y' Z' : C} (f g : X ⟶ Y)
(f' g' : X' ⟶ Y') (p : X ⊗ Z ⟶ X') (q : Y ⊗ Z ⟶ Y') (wf : (f ▷ Z) ≫ q = p ≫ f')
(wg : (g ▷ Z) ≫ q = p ≫ g') (h : Y' ⟶ Z') (wh : f' ≫ h = g' ≫ h) :
(coequalizer.π f g ▷ Z) ≫
(PreservesCoequalizer.iso (tensorRight Z) f g).inv ≫
colimMap (parallelPairHom (f ▷ Z) (g ▷ Z) f' g' p q wf wg) ≫ coequalizer.desc h wh =
q ≫ h :=
map_π_preserves_coequalizer_inv_colimMap_desc (tensorRight Z) f g f' g' p q wf wg h wh
#align π_tensor_id_preserves_coequalizer_inv_colim_map_desc π_tensor_id_preserves_coequalizer_inv_colimMap_desc
end
end
/-- A bimodule object for a pair of monoid objects, all internal to some monoidal category. -/
structure Bimod (A B : Mon_ C) where
X : C
actLeft : A.X ⊗ X ⟶ X
one_actLeft : (A.one ▷ X) ≫ actLeft = (λ_ X).hom := by aesop_cat
left_assoc :
(A.mul ▷ X) ≫ actLeft = (α_ A.X A.X X).hom ≫ (A.X ◁ actLeft) ≫ actLeft := by aesop_cat
actRight : X ⊗ B.X ⟶ X
actRight_one : (X ◁ B.one) ≫ actRight = (ρ_ X).hom := by aesop_cat
right_assoc :
(X ◁ B.mul) ≫ actRight = (α_ X B.X B.X).inv ≫ (actRight ▷ B.X) ≫ actRight := by
aesop_cat
middle_assoc :
(actLeft ▷ B.X) ≫ actRight = (α_ A.X X B.X).hom ≫ (A.X ◁ actRight) ≫ actLeft := by
aesop_cat
set_option linter.uppercaseLean3 false in
#align Bimod Bimod
attribute [reassoc (attr := simp)] Bimod.one_actLeft Bimod.actRight_one Bimod.left_assoc
Bimod.right_assoc Bimod.middle_assoc
namespace Bimod
variable {A B : Mon_ C} (M : Bimod A B)
/-- A morphism of bimodule objects. -/
@[ext]
structure Hom (M N : Bimod A B) where
hom : M.X ⟶ N.X
left_act_hom : M.actLeft ≫ hom = (A.X ◁ hom) ≫ N.actLeft := by aesop_cat
right_act_hom : M.actRight ≫ hom = (hom ▷ B.X) ≫ N.actRight := by aesop_cat
set_option linter.uppercaseLean3 false in
#align Bimod.hom Bimod.Hom
attribute [reassoc (attr := simp)] Hom.left_act_hom Hom.right_act_hom
/-- The identity morphism on a bimodule object. -/
@[simps]
def id' (M : Bimod A B) : Hom M M where hom := 𝟙 M.X
set_option linter.uppercaseLean3 false in
#align Bimod.id' Bimod.id'
instance homInhabited (M : Bimod A B) : Inhabited (Hom M M) :=
⟨id' M⟩
set_option linter.uppercaseLean3 false in
#align Bimod.hom_inhabited Bimod.homInhabited
/-- Composition of bimodule object morphisms. -/
@[simps]
def comp {M N O : Bimod A B} (f : Hom M N) (g : Hom N O) : Hom M O where hom := f.hom ≫ g.hom
set_option linter.uppercaseLean3 false in
#align Bimod.comp Bimod.comp
instance : Category (Bimod A B) where
Hom M N := Hom M N
id := id'
comp f g := comp f g
-- Porting note: added because `Hom.ext` is not triggered automatically
@[ext]
lemma hom_ext {M N : Bimod A B} (f g : M ⟶ N) (h : f.hom = g.hom) : f = g :=
Hom.ext _ _ h
@[simp]
theorem id_hom' (M : Bimod A B) : (𝟙 M : Hom M M).hom = 𝟙 M.X :=
rfl
set_option linter.uppercaseLean3 false in
#align Bimod.id_hom' Bimod.id_hom'
@[simp]
theorem comp_hom' {M N K : Bimod A B} (f : M ⟶ N) (g : N ⟶ K) :
(f ≫ g : Hom M K).hom = f.hom ≫ g.hom :=
rfl
set_option linter.uppercaseLean3 false in
#align Bimod.comp_hom' Bimod.comp_hom'
/-- Construct an isomorphism of bimodules by giving an isomorphism between the underlying objects
and checking compatibility with left and right actions only in the forward direction.
-/
@[simps]
def isoOfIso {X Y : Mon_ C} {P Q : Bimod X Y} (f : P.X ≅ Q.X)
(f_left_act_hom : P.actLeft ≫ f.hom = (X.X ◁ f.hom) ≫ Q.actLeft)
(f_right_act_hom : P.actRight ≫ f.hom = (f.hom ▷ Y.X) ≫ Q.actRight) : P ≅ Q where
hom :=
{ hom := f.hom }
inv :=
{ hom := f.inv
left_act_hom := by
rw [← cancel_mono f.hom, Category.assoc, Category.assoc, Iso.inv_hom_id, Category.comp_id,
f_left_act_hom, ← Category.assoc, ← MonoidalCategory.whiskerLeft_comp, Iso.inv_hom_id,
MonoidalCategory.whiskerLeft_id, Category.id_comp]
right_act_hom := by
rw [← cancel_mono f.hom, Category.assoc, Category.assoc, Iso.inv_hom_id, Category.comp_id,
f_right_act_hom, ← Category.assoc, ← comp_whiskerRight, Iso.inv_hom_id,
MonoidalCategory.id_whiskerRight, Category.id_comp] }
hom_inv_id := by ext; dsimp; rw [Iso.hom_inv_id]
inv_hom_id := by ext; dsimp; rw [Iso.inv_hom_id]
set_option linter.uppercaseLean3 false in
#align Bimod.iso_of_iso Bimod.isoOfIso
variable (A)
/-- A monoid object as a bimodule over itself. -/
@[simps]
def regular : Bimod A A where
X := A.X
actLeft := A.mul
actRight := A.mul
set_option linter.uppercaseLean3 false in
#align Bimod.regular Bimod.regular
instance : Inhabited (Bimod A A) :=
⟨regular A⟩
/-- The forgetful functor from bimodule objects to the ambient category. -/
def forget : Bimod A B ⥤ C where
obj A := A.X
map f := f.hom
set_option linter.uppercaseLean3 false in
#align Bimod.forget Bimod.forget
open CategoryTheory.Limits
variable [HasCoequalizers C]
namespace TensorBimod
variable {R S T : Mon_ C} (P : Bimod R S) (Q : Bimod S T)
/-- The underlying object of the tensor product of two bimodules. -/
noncomputable def X : C :=
coequalizer (P.actRight ▷ Q.X) ((α_ _ _ _).hom ≫ (P.X ◁ Q.actLeft))
set_option linter.uppercaseLean3 false in
#align Bimod.tensor_Bimod.X Bimod.TensorBimod.X
section
variable [∀ X : C, PreservesColimitsOfSize.{0, 0} (tensorLeft X)]
/-- Left action for the tensor product of two bimodules. -/
noncomputable def actLeft : R.X ⊗ X P Q ⟶ X P Q :=
(PreservesCoequalizer.iso (tensorLeft R.X) _ _).inv ≫
colimMap
(parallelPairHom _ _ _ _
((α_ _ _ _).inv ≫ ((α_ _ _ _).inv ▷ _) ≫ (P.actLeft ▷ S.X ▷ Q.X))
((α_ _ _ _).inv ≫ (P.actLeft ▷ Q.X))
(by
dsimp
simp only [Category.assoc]
slice_lhs 1 2 => rw [associator_inv_naturality_middle]
slice_rhs 3 4 => rw [← comp_whiskerRight, middle_assoc, comp_whiskerRight]
coherence)
(by
dsimp
slice_lhs 1 1 => rw [MonoidalCategory.whiskerLeft_comp]
slice_lhs 2 3 => rw [associator_inv_naturality_right]
slice_lhs 3 4 => rw [whisker_exchange]
coherence))
set_option linter.uppercaseLean3 false in
#align Bimod.tensor_Bimod.act_left Bimod.TensorBimod.actLeft
theorem whiskerLeft_π_actLeft :
(R.X ◁ coequalizer.π _ _) ≫ actLeft P Q =
(α_ _ _ _).inv ≫ (P.actLeft ▷ Q.X) ≫ coequalizer.π _ _ := by
erw [map_π_preserves_coequalizer_inv_colimMap (tensorLeft _)]
simp only [Category.assoc]
set_option linter.uppercaseLean3 false in
#align Bimod.tensor_Bimod.id_tensor_π_act_left Bimod.TensorBimod.whiskerLeft_π_actLeft
theorem one_act_left' : (R.one ▷ _) ≫ actLeft P Q = (λ_ _).hom := by
refine (cancel_epi ((tensorLeft _).map (coequalizer.π _ _))).1 ?_
dsimp [X]
-- Porting note: had to replace `rw` by `erw`
slice_lhs 1 2 => erw [whisker_exchange]
slice_lhs 2 3 => rw [whiskerLeft_π_actLeft]
slice_lhs 1 2 => rw [associator_inv_naturality_left]
slice_lhs 2 3 => rw [← comp_whiskerRight, one_actLeft]
slice_rhs 1 2 => rw [leftUnitor_naturality]
coherence
set_option linter.uppercaseLean3 false in
#align Bimod.tensor_Bimod.one_act_left' Bimod.TensorBimod.one_act_left'
theorem left_assoc' :
(R.mul ▷ _) ≫ actLeft P Q = (α_ R.X R.X _).hom ≫ (R.X ◁ actLeft P Q) ≫ actLeft P Q := by
refine (cancel_epi ((tensorLeft _).map (coequalizer.π _ _))).1 ?_
dsimp [X]
slice_lhs 1 2 => rw [whisker_exchange]
slice_lhs 2 3 => rw [whiskerLeft_π_actLeft]
slice_lhs 1 2 => rw [associator_inv_naturality_left]
slice_lhs 2 3 => rw [← comp_whiskerRight, left_assoc, comp_whiskerRight, comp_whiskerRight]
slice_rhs 1 2 => rw [associator_naturality_right]
slice_rhs 2 3 =>
rw [← MonoidalCategory.whiskerLeft_comp, whiskerLeft_π_actLeft,
MonoidalCategory.whiskerLeft_comp, MonoidalCategory.whiskerLeft_comp]
slice_rhs 4 5 => rw [whiskerLeft_π_actLeft]
slice_rhs 3 4 => rw [associator_inv_naturality_middle]
coherence
set_option linter.uppercaseLean3 false in
#align Bimod.tensor_Bimod.left_assoc' Bimod.TensorBimod.left_assoc'
end
section
variable [∀ X : C, PreservesColimitsOfSize.{0, 0} (tensorRight X)]
/-- Right action for the tensor product of two bimodules. -/
noncomputable def actRight : X P Q ⊗ T.X ⟶ X P Q :=
(PreservesCoequalizer.iso (tensorRight T.X) _ _).inv ≫
colimMap
(parallelPairHom _ _ _ _
((α_ _ _ _).hom ≫ (α_ _ _ _).hom ≫ (P.X ◁ S.X ◁ Q.actRight) ≫ (α_ _ _ _).inv)
((α_ _ _ _).hom ≫ (P.X ◁ Q.actRight))
(by
dsimp
slice_lhs 1 2 => rw [associator_naturality_left]
slice_lhs 2 3 => rw [← whisker_exchange]
simp)
(by
dsimp
simp only [comp_whiskerRight, whisker_assoc, Category.assoc, Iso.inv_hom_id_assoc]
slice_lhs 3 4 =>
rw [← MonoidalCategory.whiskerLeft_comp, middle_assoc,
MonoidalCategory.whiskerLeft_comp]
simp))
set_option linter.uppercaseLean3 false in
#align Bimod.tensor_Bimod.act_right Bimod.TensorBimod.actRight
theorem π_tensor_id_actRight :
(coequalizer.π _ _ ▷ T.X) ≫ actRight P Q =
(α_ _ _ _).hom ≫ (P.X ◁ Q.actRight) ≫ coequalizer.π _ _ := by
erw [map_π_preserves_coequalizer_inv_colimMap (tensorRight _)]
simp only [Category.assoc]
set_option linter.uppercaseLean3 false in
#align Bimod.tensor_Bimod.π_tensor_id_act_right Bimod.TensorBimod.π_tensor_id_actRight
theorem actRight_one' : (_ ◁ T.one) ≫ actRight P Q = (ρ_ _).hom := by
refine (cancel_epi ((tensorRight _).map (coequalizer.π _ _))).1 ?_
dsimp [X]
-- Porting note: had to replace `rw` by `erw`
slice_lhs 1 2 =>erw [← whisker_exchange]
slice_lhs 2 3 => rw [π_tensor_id_actRight]
slice_lhs 1 2 => rw [associator_naturality_right]
slice_lhs 2 3 => rw [← MonoidalCategory.whiskerLeft_comp, actRight_one]
simp
set_option linter.uppercaseLean3 false in
#align Bimod.tensor_Bimod.act_right_one' Bimod.TensorBimod.actRight_one'
theorem right_assoc' :
(_ ◁ T.mul) ≫ actRight P Q =
(α_ _ T.X T.X).inv ≫ (actRight P Q ▷ T.X) ≫ actRight P Q := by
refine (cancel_epi ((tensorRight _).map (coequalizer.π _ _))).1 ?_
dsimp [X]
-- Porting note: had to replace some `rw` by `erw`
slice_lhs 1 2 => rw [← whisker_exchange]
slice_lhs 2 3 => rw [π_tensor_id_actRight]
slice_lhs 1 2 => rw [associator_naturality_right]
slice_lhs 2 3 => rw [← MonoidalCategory.whiskerLeft_comp, right_assoc,
MonoidalCategory.whiskerLeft_comp, MonoidalCategory.whiskerLeft_comp]
slice_rhs 1 2 => rw [associator_inv_naturality_left]
slice_rhs 2 3 => rw [← comp_whiskerRight, π_tensor_id_actRight, comp_whiskerRight,
comp_whiskerRight]
slice_rhs 4 5 => rw [π_tensor_id_actRight]
simp
set_option linter.uppercaseLean3 false in
#align Bimod.tensor_Bimod.right_assoc' Bimod.TensorBimod.right_assoc'
end
section
variable [∀ X : C, PreservesColimitsOfSize.{0, 0} (tensorLeft X)]
variable [∀ X : C, PreservesColimitsOfSize.{0, 0} (tensorRight X)]
theorem middle_assoc' :
(actLeft P Q ▷ T.X) ≫ actRight P Q =
(α_ R.X _ T.X).hom ≫ (R.X ◁ actRight P Q) ≫ actLeft P Q := by
refine (cancel_epi ((tensorLeft _ ⋙ tensorRight _).map (coequalizer.π _ _))).1 ?_
dsimp [X]
slice_lhs 1 2 => rw [← comp_whiskerRight, whiskerLeft_π_actLeft, comp_whiskerRight,
comp_whiskerRight]
slice_lhs 3 4 => rw [π_tensor_id_actRight]
slice_lhs 2 3 => rw [associator_naturality_left]
-- Porting note: had to replace `rw` by `erw`
slice_rhs 1 2 => rw [associator_naturality_middle]
slice_rhs 2 3 => rw [← MonoidalCategory.whiskerLeft_comp, π_tensor_id_actRight,
MonoidalCategory.whiskerLeft_comp, MonoidalCategory.whiskerLeft_comp]
slice_rhs 4 5 => rw [whiskerLeft_π_actLeft]
slice_rhs 3 4 => rw [associator_inv_naturality_right]
slice_rhs 4 5 => rw [whisker_exchange]
simp
set_option linter.uppercaseLean3 false in
#align Bimod.tensor_Bimod.middle_assoc' Bimod.TensorBimod.middle_assoc'
end
end TensorBimod
section
variable [∀ X : C, PreservesColimitsOfSize.{0, 0} (tensorLeft X)]
variable [∀ X : C, PreservesColimitsOfSize.{0, 0} (tensorRight X)]
/-- Tensor product of two bimodule objects as a bimodule object. -/
@[simps]
noncomputable def tensorBimod {X Y Z : Mon_ C} (M : Bimod X Y) (N : Bimod Y Z) : Bimod X Z where
X := TensorBimod.X M N
actLeft := TensorBimod.actLeft M N
actRight := TensorBimod.actRight M N
one_actLeft := TensorBimod.one_act_left' M N
actRight_one := TensorBimod.actRight_one' M N
left_assoc := TensorBimod.left_assoc' M N
right_assoc := TensorBimod.right_assoc' M N
middle_assoc := TensorBimod.middle_assoc' M N
set_option linter.uppercaseLean3 false in
#align Bimod.tensor_Bimod Bimod.tensorBimod
/-- Left whiskering for morphisms of bimodule objects. -/
@[simps]
noncomputable def whiskerLeft {X Y Z : Mon_ C} (M : Bimod X Y) {N₁ N₂ : Bimod Y Z} (f : N₁ ⟶ N₂) :
M.tensorBimod N₁ ⟶ M.tensorBimod N₂ where
hom :=
colimMap
(parallelPairHom _ _ _ _ (_ ◁ f.hom) (_ ◁ f.hom)
(by rw [whisker_exchange])
(by
simp only [Category.assoc, tensor_whiskerLeft, Iso.inv_hom_id_assoc,
Iso.cancel_iso_hom_left]
slice_lhs 1 2 => rw [← MonoidalCategory.whiskerLeft_comp, Hom.left_act_hom]
simp))
left_act_hom := by
refine (cancel_epi ((tensorLeft _).map (coequalizer.π _ _))).1 ?_
dsimp
slice_lhs 1 2 => rw [TensorBimod.whiskerLeft_π_actLeft]
slice_lhs 3 4 => rw [ι_colimMap, parallelPairHom_app_one]
slice_rhs 1 2 => rw [← MonoidalCategory.whiskerLeft_comp, ι_colimMap, parallelPairHom_app_one,
MonoidalCategory.whiskerLeft_comp]
slice_rhs 2 3 => rw [TensorBimod.whiskerLeft_π_actLeft]
slice_rhs 1 2 => rw [associator_inv_naturality_right]
slice_rhs 2 3 => rw [whisker_exchange]
simp
right_act_hom := by
refine (cancel_epi ((tensorRight _).map (coequalizer.π _ _))).1 ?_
dsimp
slice_lhs 1 2 => rw [TensorBimod.π_tensor_id_actRight]
slice_lhs 3 4 => rw [ι_colimMap, parallelPairHom_app_one]
slice_lhs 2 3 => rw [← MonoidalCategory.whiskerLeft_comp, Hom.right_act_hom]
slice_rhs 1 2 =>
rw [← comp_whiskerRight, ι_colimMap, parallelPairHom_app_one, comp_whiskerRight]
slice_rhs 2 3 => rw [TensorBimod.π_tensor_id_actRight]
simp
/-- Right whiskering for morphisms of bimodule objects. -/
@[simps]
noncomputable def whiskerRight {X Y Z : Mon_ C} {M₁ M₂ : Bimod X Y} (f : M₁ ⟶ M₂) (N : Bimod Y Z) :
M₁.tensorBimod N ⟶ M₂.tensorBimod N where
hom :=
colimMap
(parallelPairHom _ _ _ _ (f.hom ▷ _ ▷ _) (f.hom ▷ _)
(by rw [← comp_whiskerRight, Hom.right_act_hom, comp_whiskerRight])
(by
slice_lhs 2 3 => rw [whisker_exchange]
simp))
left_act_hom := by
refine (cancel_epi ((tensorLeft _).map (coequalizer.π _ _))).1 ?_
dsimp
slice_lhs 1 2 => rw [TensorBimod.whiskerLeft_π_actLeft]
slice_lhs 3 4 => rw [ι_colimMap, parallelPairHom_app_one]
slice_lhs 2 3 => rw [← comp_whiskerRight, Hom.left_act_hom]
slice_rhs 1 2 => rw [← MonoidalCategory.whiskerLeft_comp, ι_colimMap, parallelPairHom_app_one,
MonoidalCategory.whiskerLeft_comp]
slice_rhs 2 3 => rw [TensorBimod.whiskerLeft_π_actLeft]
slice_rhs 1 2 => rw [associator_inv_naturality_middle]
simp
right_act_hom := by
refine (cancel_epi ((tensorRight _).map (coequalizer.π _ _))).1 ?_
dsimp
slice_lhs 1 2 => rw [TensorBimod.π_tensor_id_actRight]
slice_lhs 3 4 => rw [ι_colimMap, parallelPairHom_app_one]
slice_lhs 2 3 => rw [whisker_exchange]
slice_rhs 1 2 => rw [← comp_whiskerRight, ι_colimMap, parallelPairHom_app_one,
comp_whiskerRight]
slice_rhs 2 3 => rw [TensorBimod.π_tensor_id_actRight]
simp
end
namespace AssociatorBimod
variable [∀ X : C, PreservesColimitsOfSize.{0, 0} (tensorLeft X)]
variable [∀ X : C, PreservesColimitsOfSize.{0, 0} (tensorRight X)]
variable {R S T U : Mon_ C} (P : Bimod R S) (Q : Bimod S T) (L : Bimod T U)
/-- An auxiliary morphism for the definition of the underlying morphism of the forward component of
the associator isomorphism. -/
noncomputable def homAux : (P.tensorBimod Q).X ⊗ L.X ⟶ (P.tensorBimod (Q.tensorBimod L)).X :=
(PreservesCoequalizer.iso (tensorRight L.X) _ _).inv ≫
coequalizer.desc ((α_ _ _ _).hom ≫ (P.X ◁ coequalizer.π _ _) ≫ coequalizer.π _ _)
(by
dsimp; dsimp [TensorBimod.X]
slice_lhs 1 2 => rw [associator_naturality_left]
slice_lhs 2 3 => rw [← whisker_exchange]
slice_lhs 3 4 => rw [coequalizer.condition]
slice_lhs 2 3 => rw [associator_naturality_right]
slice_lhs 3 4 =>
rw [← MonoidalCategory.whiskerLeft_comp,
TensorBimod.whiskerLeft_π_actLeft, MonoidalCategory.whiskerLeft_comp]
simp)
set_option linter.uppercaseLean3 false in
#align Bimod.associator_Bimod.hom_aux Bimod.AssociatorBimod.homAux
/-- The underlying morphism of the forward component of the associator isomorphism. -/
noncomputable def hom :
((P.tensorBimod Q).tensorBimod L).X ⟶ (P.tensorBimod (Q.tensorBimod L)).X :=
coequalizer.desc (homAux P Q L)
(by
dsimp [homAux]
refine (cancel_epi ((tensorRight _ ⋙ tensorRight _).map (coequalizer.π _ _))).1 ?_
dsimp [TensorBimod.X]
slice_lhs 1 2 => rw [← comp_whiskerRight, TensorBimod.π_tensor_id_actRight,
comp_whiskerRight, comp_whiskerRight]
slice_lhs 3 5 => rw [π_tensor_id_preserves_coequalizer_inv_desc]
slice_lhs 2 3 => rw [associator_naturality_middle]
slice_lhs 3 4 =>
rw [← MonoidalCategory.whiskerLeft_comp, coequalizer.condition,
MonoidalCategory.whiskerLeft_comp, MonoidalCategory.whiskerLeft_comp]
slice_rhs 1 2 => rw [associator_naturality_left]
slice_rhs 2 3 => rw [← whisker_exchange]
slice_rhs 3 5 => rw [π_tensor_id_preserves_coequalizer_inv_desc]
simp)
set_option linter.uppercaseLean3 false in
#align Bimod.associator_Bimod.hom Bimod.AssociatorBimod.hom
theorem hom_left_act_hom' :
((P.tensorBimod Q).tensorBimod L).actLeft ≫ hom P Q L =
(R.X ◁ hom P Q L) ≫ (P.tensorBimod (Q.tensorBimod L)).actLeft := by
dsimp; dsimp [hom, homAux]
refine (cancel_epi ((tensorLeft _).map (coequalizer.π _ _))).1 ?_
rw [tensorLeft_map]
slice_lhs 1 2 => rw [TensorBimod.whiskerLeft_π_actLeft]
slice_lhs 3 4 => rw [coequalizer.π_desc]
slice_rhs 1 2 => rw [← MonoidalCategory.whiskerLeft_comp, coequalizer.π_desc,
MonoidalCategory.whiskerLeft_comp]
refine (cancel_epi ((tensorRight _ ⋙ tensorLeft _).map (coequalizer.π _ _))).1 ?_
dsimp; dsimp [TensorBimod.X]
slice_lhs 1 2 => rw [associator_inv_naturality_middle]
slice_lhs 2 3 =>
rw [← comp_whiskerRight, TensorBimod.whiskerLeft_π_actLeft,
comp_whiskerRight, comp_whiskerRight]
slice_lhs 4 6 => rw [π_tensor_id_preserves_coequalizer_inv_desc]
slice_lhs 3 4 => rw [associator_naturality_left]
slice_rhs 1 3 =>
rw [← MonoidalCategory.whiskerLeft_comp, ← MonoidalCategory.whiskerLeft_comp,
π_tensor_id_preserves_coequalizer_inv_desc, MonoidalCategory.whiskerLeft_comp,
MonoidalCategory.whiskerLeft_comp]
slice_rhs 3 4 => erw [TensorBimod.whiskerLeft_π_actLeft P (Q.tensorBimod L)]
slice_rhs 2 3 => erw [associator_inv_naturality_right]
slice_rhs 3 4 => erw [whisker_exchange]
coherence
set_option linter.uppercaseLean3 false in
#align Bimod.associator_Bimod.hom_left_act_hom' Bimod.AssociatorBimod.hom_left_act_hom'
| Mathlib/CategoryTheory/Monoidal/Bimod.lean | 543 | 567 | theorem hom_right_act_hom' :
((P.tensorBimod Q).tensorBimod L).actRight ≫ hom P Q L =
(hom P Q L ▷ U.X) ≫ (P.tensorBimod (Q.tensorBimod L)).actRight := by |
dsimp; dsimp [hom, homAux]
refine (cancel_epi ((tensorRight _).map (coequalizer.π _ _))).1 ?_
rw [tensorRight_map]
slice_lhs 1 2 => rw [TensorBimod.π_tensor_id_actRight]
slice_lhs 3 4 => rw [coequalizer.π_desc]
slice_rhs 1 2 => rw [← comp_whiskerRight, coequalizer.π_desc, comp_whiskerRight]
refine (cancel_epi ((tensorRight _ ⋙ tensorRight _).map (coequalizer.π _ _))).1 ?_
dsimp; dsimp [TensorBimod.X]
slice_lhs 1 2 => rw [associator_naturality_left]
slice_lhs 2 3 => rw [← whisker_exchange]
slice_lhs 3 5 => rw [π_tensor_id_preserves_coequalizer_inv_desc]
slice_lhs 2 3 => rw [associator_naturality_right]
slice_rhs 1 3 =>
rw [← comp_whiskerRight, ← comp_whiskerRight, π_tensor_id_preserves_coequalizer_inv_desc,
comp_whiskerRight, comp_whiskerRight]
slice_rhs 3 4 => erw [TensorBimod.π_tensor_id_actRight P (Q.tensorBimod L)]
slice_rhs 2 3 => erw [associator_naturality_middle]
dsimp
slice_rhs 3 4 =>
rw [← MonoidalCategory.whiskerLeft_comp, TensorBimod.π_tensor_id_actRight,
MonoidalCategory.whiskerLeft_comp, MonoidalCategory.whiskerLeft_comp]
coherence
|
/-
Copyright (c) 2022 Yaël Dillies, Bhavik Mehta. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yaël Dillies, Bhavik Mehta
-/
import Mathlib.Algebra.Order.Field.Basic
import Mathlib.Combinatorics.SimpleGraph.Basic
import Mathlib.Data.Rat.Cast.Order
import Mathlib.Order.Partition.Finpartition
import Mathlib.Tactic.GCongr
import Mathlib.Tactic.NormNum
import Mathlib.Tactic.Positivity
import Mathlib.Tactic.Ring
#align_import combinatorics.simple_graph.density from "leanprover-community/mathlib"@"a4ec43f53b0bd44c697bcc3f5a62edd56f269ef1"
/-!
# Edge density
This file defines the number and density of edges of a relation/graph.
## Main declarations
Between two finsets of vertices,
* `Rel.interedges`: Finset of edges of a relation.
* `Rel.edgeDensity`: Edge density of a relation.
* `SimpleGraph.interedges`: Finset of edges of a graph.
* `SimpleGraph.edgeDensity`: Edge density of a graph.
-/
open Finset
variable {𝕜 ι κ α β : Type*}
/-! ### Density of a relation -/
namespace Rel
section Asymmetric
variable [LinearOrderedField 𝕜] (r : α → β → Prop) [∀ a, DecidablePred (r a)] {s s₁ s₂ : Finset α}
{t t₁ t₂ : Finset β} {a : α} {b : β} {δ : 𝕜}
/-- Finset of edges of a relation between two finsets of vertices. -/
def interedges (s : Finset α) (t : Finset β) : Finset (α × β) :=
(s ×ˢ t).filter fun e ↦ r e.1 e.2
#align rel.interedges Rel.interedges
/-- Edge density of a relation between two finsets of vertices. -/
def edgeDensity (s : Finset α) (t : Finset β) : ℚ :=
(interedges r s t).card / (s.card * t.card)
#align rel.edge_density Rel.edgeDensity
variable {r}
| Mathlib/Combinatorics/SimpleGraph/Density.lean | 57 | 58 | theorem mem_interedges_iff {x : α × β} : x ∈ interedges r s t ↔ x.1 ∈ s ∧ x.2 ∈ t ∧ r x.1 x.2 := by |
rw [interedges, mem_filter, Finset.mem_product, and_assoc]
|
/-
Copyright (c) 2020 Kenny Lau. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kenny Lau, Ken Lee, Chris Hughes
-/
import Mathlib.Algebra.GroupWithZero.Divisibility
import Mathlib.Algebra.Ring.Divisibility.Basic
import Mathlib.Algebra.Ring.Hom.Defs
import Mathlib.GroupTheory.GroupAction.Units
import Mathlib.Logic.Basic
import Mathlib.Tactic.Ring
#align_import ring_theory.coprime.basic from "leanprover-community/mathlib"@"a95b16cbade0f938fc24abd05412bde1e84bab9b"
/-!
# Coprime elements of a ring or monoid
## Main definition
* `IsCoprime x y`: that `x` and `y` are coprime, defined to be the existence of `a` and `b` such
that `a * x + b * y = 1`. Note that elements with no common divisors (`IsRelPrime`) are not
necessarily coprime, e.g., the multivariate polynomials `x₁` and `x₂` are not coprime.
The two notions are equivalent in Bézout rings, see `isRelPrime_iff_isCoprime`.
This file also contains lemmas about `IsRelPrime` parallel to `IsCoprime`.
See also `RingTheory.Coprime.Lemmas` for further development of coprime elements.
-/
universe u v
section CommSemiring
variable {R : Type u} [CommSemiring R] (x y z : R)
/-- The proposition that `x` and `y` are coprime, defined to be the existence of `a` and `b` such
that `a * x + b * y = 1`. Note that elements with no common divisors are not necessarily coprime,
e.g., the multivariate polynomials `x₁` and `x₂` are not coprime. -/
def IsCoprime : Prop :=
∃ a b, a * x + b * y = 1
#align is_coprime IsCoprime
variable {x y z}
@[symm]
theorem IsCoprime.symm (H : IsCoprime x y) : IsCoprime y x :=
let ⟨a, b, H⟩ := H
⟨b, a, by rw [add_comm, H]⟩
#align is_coprime.symm IsCoprime.symm
theorem isCoprime_comm : IsCoprime x y ↔ IsCoprime y x :=
⟨IsCoprime.symm, IsCoprime.symm⟩
#align is_coprime_comm isCoprime_comm
theorem isCoprime_self : IsCoprime x x ↔ IsUnit x :=
⟨fun ⟨a, b, h⟩ => isUnit_of_mul_eq_one x (a + b) <| by rwa [mul_comm, add_mul], fun h =>
let ⟨b, hb⟩ := isUnit_iff_exists_inv'.1 h
⟨b, 0, by rwa [zero_mul, add_zero]⟩⟩
#align is_coprime_self isCoprime_self
theorem isCoprime_zero_left : IsCoprime 0 x ↔ IsUnit x :=
⟨fun ⟨a, b, H⟩ => isUnit_of_mul_eq_one x b <| by rwa [mul_zero, zero_add, mul_comm] at H, fun H =>
let ⟨b, hb⟩ := isUnit_iff_exists_inv'.1 H
⟨1, b, by rwa [one_mul, zero_add]⟩⟩
#align is_coprime_zero_left isCoprime_zero_left
theorem isCoprime_zero_right : IsCoprime x 0 ↔ IsUnit x :=
isCoprime_comm.trans isCoprime_zero_left
#align is_coprime_zero_right isCoprime_zero_right
theorem not_isCoprime_zero_zero [Nontrivial R] : ¬IsCoprime (0 : R) 0 :=
mt isCoprime_zero_right.mp not_isUnit_zero
#align not_coprime_zero_zero not_isCoprime_zero_zero
lemma IsCoprime.intCast {R : Type*} [CommRing R] {a b : ℤ} (h : IsCoprime a b) :
IsCoprime (a : R) (b : R) := by
rcases h with ⟨u, v, H⟩
use u, v
rw_mod_cast [H]
exact Int.cast_one
/-- If a 2-vector `p` satisfies `IsCoprime (p 0) (p 1)`, then `p ≠ 0`. -/
| Mathlib/RingTheory/Coprime/Basic.lean | 84 | 86 | theorem IsCoprime.ne_zero [Nontrivial R] {p : Fin 2 → R} (h : IsCoprime (p 0) (p 1)) : p ≠ 0 := by |
rintro rfl
exact not_isCoprime_zero_zero h
|
/-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes
-/
import Mathlib.Data.Finset.Fin
import Mathlib.Data.Int.Order.Units
import Mathlib.GroupTheory.OrderOfElement
import Mathlib.GroupTheory.Perm.Support
import Mathlib.Logic.Equiv.Fintype
#align_import group_theory.perm.sign from "leanprover-community/mathlib"@"f694c7dead66f5d4c80f446c796a5aad14707f0e"
/-!
# Permutations on `Fintype`s
This file contains miscellaneous lemmas about `Equiv.Perm` and `Equiv.swap`, building on top
of those in `Data/Equiv/Basic` and other files in `GroupTheory/Perm/*`.
-/
universe u v
open Equiv Function Fintype Finset
variable {α : Type u} {β : Type v}
-- An example on how to determine the order of an element of a finite group.
example : orderOf (-1 : ℤˣ) = 2 :=
orderOf_eq_prime (Int.units_sq _) (by decide)
namespace Equiv.Perm
section Conjugation
variable [DecidableEq α] [Fintype α] {σ τ : Perm α}
theorem isConj_of_support_equiv
(f : { x // x ∈ (σ.support : Set α) } ≃ { x // x ∈ (τ.support : Set α) })
(hf : ∀ (x : α) (hx : x ∈ (σ.support : Set α)),
(f ⟨σ x, apply_mem_support.2 hx⟩ : α) = τ ↑(f ⟨x, hx⟩)) :
IsConj σ τ := by
refine isConj_iff.2 ⟨Equiv.extendSubtype f, ?_⟩
rw [mul_inv_eq_iff_eq_mul]
ext x
simp only [Perm.mul_apply]
by_cases hx : x ∈ σ.support
· rw [Equiv.extendSubtype_apply_of_mem, Equiv.extendSubtype_apply_of_mem]
· exact hf x (Finset.mem_coe.2 hx)
· rwa [Classical.not_not.1 ((not_congr mem_support).1 (Equiv.extendSubtype_not_mem f _ _)),
Classical.not_not.1 ((not_congr mem_support).mp hx)]
#align equiv.perm.is_conj_of_support_equiv Equiv.Perm.isConj_of_support_equiv
end Conjugation
theorem perm_inv_on_of_perm_on_finset {s : Finset α} {f : Perm α} (h : ∀ x ∈ s, f x ∈ s) {y : α}
(hy : y ∈ s) : f⁻¹ y ∈ s := by
have h0 : ∀ y ∈ s, ∃ (x : _) (hx : x ∈ s), y = (fun i (_ : i ∈ s) => f i) x hx :=
Finset.surj_on_of_inj_on_of_card_le (fun x hx => (fun i _ => f i) x hx) (fun a ha => h a ha)
(fun a₁ a₂ ha₁ ha₂ heq => (Equiv.apply_eq_iff_eq f).mp heq) rfl.ge
obtain ⟨y2, hy2, heq⟩ := h0 y hy
convert hy2
rw [heq]
simp only [inv_apply_self]
#align equiv.perm.perm_inv_on_of_perm_on_finset Equiv.Perm.perm_inv_on_of_perm_on_finset
| Mathlib/GroupTheory/Perm/Finite.lean | 68 | 75 | theorem perm_inv_mapsTo_of_mapsTo (f : Perm α) {s : Set α} [Finite s] (h : Set.MapsTo f s s) :
Set.MapsTo (f⁻¹ : _) s s := by |
cases nonempty_fintype s
exact fun x hx =>
Set.mem_toFinset.mp <|
perm_inv_on_of_perm_on_finset
(fun a ha => Set.mem_toFinset.mpr (h (Set.mem_toFinset.mp ha)))
(Set.mem_toFinset.mpr hx)
|
/-
Copyright (c) 2021 Rémy Degenne. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Rémy Degenne
-/
import Mathlib.MeasureTheory.Function.StronglyMeasurable.Lp
import Mathlib.MeasureTheory.Integral.Bochner
import Mathlib.Order.Filter.IndicatorFunction
import Mathlib.MeasureTheory.Function.StronglyMeasurable.Inner
import Mathlib.MeasureTheory.Function.LpSeminorm.Trim
#align_import measure_theory.function.conditional_expectation.ae_measurable from "leanprover-community/mathlib"@"d8bbb04e2d2a44596798a9207ceefc0fb236e41e"
/-! # Functions a.e. measurable with respect to a sub-σ-algebra
A function `f` verifies `AEStronglyMeasurable' m f μ` if it is `μ`-a.e. equal to
an `m`-strongly measurable function. This is similar to `AEStronglyMeasurable`, but the
`MeasurableSpace` structures used for the measurability statement and for the measure are
different.
We define `lpMeas F 𝕜 m p μ`, the subspace of `Lp F p μ` containing functions `f` verifying
`AEStronglyMeasurable' m f μ`, i.e. functions which are `μ`-a.e. equal to an `m`-strongly
measurable function.
## Main statements
We define an `IsometryEquiv` between `lpMeasSubgroup` and the `Lp` space corresponding to the
measure `μ.trim hm`. As a consequence, the completeness of `Lp` implies completeness of `lpMeas`.
`Lp.induction_stronglyMeasurable` (see also `Memℒp.induction_stronglyMeasurable`):
To prove something for an `Lp` function a.e. strongly measurable with respect to a
sub-σ-algebra `m` in a normed space, it suffices to show that
* the property holds for (multiples of) characteristic functions which are measurable w.r.t. `m`;
* is closed under addition;
* the set of functions in `Lp` strongly measurable w.r.t. `m` for which the property holds is
closed.
-/
set_option linter.uppercaseLean3 false
open TopologicalSpace Filter
open scoped ENNReal MeasureTheory
namespace MeasureTheory
/-- A function `f` verifies `AEStronglyMeasurable' m f μ` if it is `μ`-a.e. equal to
an `m`-strongly measurable function. This is similar to `AEStronglyMeasurable`, but the
`MeasurableSpace` structures used for the measurability statement and for the measure are
different. -/
def AEStronglyMeasurable' {α β} [TopologicalSpace β] (m : MeasurableSpace α)
{_ : MeasurableSpace α} (f : α → β) (μ : Measure α) : Prop :=
∃ g : α → β, StronglyMeasurable[m] g ∧ f =ᵐ[μ] g
#align measure_theory.ae_strongly_measurable' MeasureTheory.AEStronglyMeasurable'
namespace AEStronglyMeasurable'
variable {α β 𝕜 : Type*} {m m0 : MeasurableSpace α} {μ : Measure α} [TopologicalSpace β]
{f g : α → β}
theorem congr (hf : AEStronglyMeasurable' m f μ) (hfg : f =ᵐ[μ] g) :
AEStronglyMeasurable' m g μ := by
obtain ⟨f', hf'_meas, hff'⟩ := hf; exact ⟨f', hf'_meas, hfg.symm.trans hff'⟩
#align measure_theory.ae_strongly_measurable'.congr MeasureTheory.AEStronglyMeasurable'.congr
theorem mono {m'} (hf : AEStronglyMeasurable' m f μ) (hm : m ≤ m') :
AEStronglyMeasurable' m' f μ :=
let ⟨f', hf'_meas, hff'⟩ := hf; ⟨f', hf'_meas.mono hm, hff'⟩
theorem add [Add β] [ContinuousAdd β] (hf : AEStronglyMeasurable' m f μ)
(hg : AEStronglyMeasurable' m g μ) : AEStronglyMeasurable' m (f + g) μ := by
rcases hf with ⟨f', h_f'_meas, hff'⟩
rcases hg with ⟨g', h_g'_meas, hgg'⟩
exact ⟨f' + g', h_f'_meas.add h_g'_meas, hff'.add hgg'⟩
#align measure_theory.ae_strongly_measurable'.add MeasureTheory.AEStronglyMeasurable'.add
theorem neg [AddGroup β] [TopologicalAddGroup β] {f : α → β} (hfm : AEStronglyMeasurable' m f μ) :
AEStronglyMeasurable' m (-f) μ := by
rcases hfm with ⟨f', hf'_meas, hf_ae⟩
refine ⟨-f', hf'_meas.neg, hf_ae.mono fun x hx => ?_⟩
simp_rw [Pi.neg_apply]
rw [hx]
#align measure_theory.ae_strongly_measurable'.neg MeasureTheory.AEStronglyMeasurable'.neg
theorem sub [AddGroup β] [TopologicalAddGroup β] {f g : α → β} (hfm : AEStronglyMeasurable' m f μ)
(hgm : AEStronglyMeasurable' m g μ) : AEStronglyMeasurable' m (f - g) μ := by
rcases hfm with ⟨f', hf'_meas, hf_ae⟩
rcases hgm with ⟨g', hg'_meas, hg_ae⟩
refine ⟨f' - g', hf'_meas.sub hg'_meas, hf_ae.mp (hg_ae.mono fun x hx1 hx2 => ?_)⟩
simp_rw [Pi.sub_apply]
rw [hx1, hx2]
#align measure_theory.ae_strongly_measurable'.sub MeasureTheory.AEStronglyMeasurable'.sub
theorem const_smul [SMul 𝕜 β] [ContinuousConstSMul 𝕜 β] (c : 𝕜) (hf : AEStronglyMeasurable' m f μ) :
AEStronglyMeasurable' m (c • f) μ := by
rcases hf with ⟨f', h_f'_meas, hff'⟩
refine ⟨c • f', h_f'_meas.const_smul c, ?_⟩
exact EventuallyEq.fun_comp hff' fun x => c • x
#align measure_theory.ae_strongly_measurable'.const_smul MeasureTheory.AEStronglyMeasurable'.const_smul
theorem const_inner {𝕜 β} [RCLike 𝕜] [NormedAddCommGroup β] [InnerProductSpace 𝕜 β] {f : α → β}
(hfm : AEStronglyMeasurable' m f μ) (c : β) :
AEStronglyMeasurable' m (fun x => (inner c (f x) : 𝕜)) μ := by
rcases hfm with ⟨f', hf'_meas, hf_ae⟩
refine
⟨fun x => (inner c (f' x) : 𝕜), (@stronglyMeasurable_const _ _ m _ c).inner hf'_meas,
hf_ae.mono fun x hx => ?_⟩
dsimp only
rw [hx]
#align measure_theory.ae_strongly_measurable'.const_inner MeasureTheory.AEStronglyMeasurable'.const_inner
/-- An `m`-strongly measurable function almost everywhere equal to `f`. -/
noncomputable def mk (f : α → β) (hfm : AEStronglyMeasurable' m f μ) : α → β :=
hfm.choose
#align measure_theory.ae_strongly_measurable'.mk MeasureTheory.AEStronglyMeasurable'.mk
theorem stronglyMeasurable_mk {f : α → β} (hfm : AEStronglyMeasurable' m f μ) :
StronglyMeasurable[m] (hfm.mk f) :=
hfm.choose_spec.1
#align measure_theory.ae_strongly_measurable'.stronglyMeasurable_mk MeasureTheory.AEStronglyMeasurable'.stronglyMeasurable_mk
theorem ae_eq_mk {f : α → β} (hfm : AEStronglyMeasurable' m f μ) : f =ᵐ[μ] hfm.mk f :=
hfm.choose_spec.2
#align measure_theory.ae_strongly_measurable'.ae_eq_mk MeasureTheory.AEStronglyMeasurable'.ae_eq_mk
theorem continuous_comp {γ} [TopologicalSpace γ] {f : α → β} {g : β → γ} (hg : Continuous g)
(hf : AEStronglyMeasurable' m f μ) : AEStronglyMeasurable' m (g ∘ f) μ :=
⟨fun x => g (hf.mk _ x),
@Continuous.comp_stronglyMeasurable _ _ _ m _ _ _ _ hg hf.stronglyMeasurable_mk,
hf.ae_eq_mk.mono fun x hx => by rw [Function.comp_apply, hx]⟩
#align measure_theory.ae_strongly_measurable'.continuous_comp MeasureTheory.AEStronglyMeasurable'.continuous_comp
end AEStronglyMeasurable'
theorem aeStronglyMeasurable'_of_aeStronglyMeasurable'_trim {α β} {m m0 m0' : MeasurableSpace α}
[TopologicalSpace β] (hm0 : m0 ≤ m0') {μ : Measure α} {f : α → β}
(hf : AEStronglyMeasurable' m f (μ.trim hm0)) : AEStronglyMeasurable' m f μ := by
obtain ⟨g, hg_meas, hfg⟩ := hf; exact ⟨g, hg_meas, ae_eq_of_ae_eq_trim hfg⟩
#align measure_theory.ae_strongly_measurable'_of_ae_strongly_measurable'_trim MeasureTheory.aeStronglyMeasurable'_of_aeStronglyMeasurable'_trim
theorem StronglyMeasurable.aeStronglyMeasurable' {α β} {m _ : MeasurableSpace α}
[TopologicalSpace β] {μ : Measure α} {f : α → β} (hf : StronglyMeasurable[m] f) :
AEStronglyMeasurable' m f μ :=
⟨f, hf, ae_eq_refl _⟩
#align measure_theory.strongly_measurable.ae_strongly_measurable' MeasureTheory.StronglyMeasurable.aeStronglyMeasurable'
theorem ae_eq_trim_iff_of_aeStronglyMeasurable' {α β} [TopologicalSpace β] [MetrizableSpace β]
{m m0 : MeasurableSpace α} {μ : Measure α} {f g : α → β} (hm : m ≤ m0)
(hfm : AEStronglyMeasurable' m f μ) (hgm : AEStronglyMeasurable' m g μ) :
hfm.mk f =ᵐ[μ.trim hm] hgm.mk g ↔ f =ᵐ[μ] g :=
(ae_eq_trim_iff hm hfm.stronglyMeasurable_mk hgm.stronglyMeasurable_mk).trans
⟨fun h => hfm.ae_eq_mk.trans (h.trans hgm.ae_eq_mk.symm), fun h =>
hfm.ae_eq_mk.symm.trans (h.trans hgm.ae_eq_mk)⟩
#align measure_theory.ae_eq_trim_iff_of_ae_strongly_measurable' MeasureTheory.ae_eq_trim_iff_of_aeStronglyMeasurable'
theorem AEStronglyMeasurable.comp_ae_measurable' {α β γ : Type*} [TopologicalSpace β]
{mα : MeasurableSpace α} {_ : MeasurableSpace γ} {f : α → β} {μ : Measure γ} {g : γ → α}
(hf : AEStronglyMeasurable f (μ.map g)) (hg : AEMeasurable g μ) :
AEStronglyMeasurable' (mα.comap g) (f ∘ g) μ :=
⟨hf.mk f ∘ g, hf.stronglyMeasurable_mk.comp_measurable (measurable_iff_comap_le.mpr le_rfl),
ae_eq_comp hg hf.ae_eq_mk⟩
#align measure_theory.ae_strongly_measurable.comp_ae_measurable' MeasureTheory.AEStronglyMeasurable.comp_ae_measurable'
/-- If the restriction to a set `s` of a σ-algebra `m` is included in the restriction to `s` of
another σ-algebra `m₂` (hypothesis `hs`), the set `s` is `m` measurable and a function `f` almost
everywhere supported on `s` is `m`-ae-strongly-measurable, then `f` is also
`m₂`-ae-strongly-measurable. -/
theorem AEStronglyMeasurable'.aeStronglyMeasurable'_of_measurableSpace_le_on {α E}
{m m₂ m0 : MeasurableSpace α} {μ : Measure α} [TopologicalSpace E] [Zero E] (hm : m ≤ m0)
{s : Set α} {f : α → E} (hs_m : MeasurableSet[m] s)
(hs : ∀ t, MeasurableSet[m] (s ∩ t) → MeasurableSet[m₂] (s ∩ t))
(hf : AEStronglyMeasurable' m f μ) (hf_zero : f =ᵐ[μ.restrict sᶜ] 0) :
AEStronglyMeasurable' m₂ f μ := by
have h_ind_eq : s.indicator (hf.mk f) =ᵐ[μ] f := by
refine Filter.EventuallyEq.trans ?_ <|
indicator_ae_eq_of_restrict_compl_ae_eq_zero (hm _ hs_m) hf_zero
filter_upwards [hf.ae_eq_mk] with x hx
by_cases hxs : x ∈ s
· simp [hxs, hx]
· simp [hxs]
suffices StronglyMeasurable[m₂] (s.indicator (hf.mk f)) from
AEStronglyMeasurable'.congr this.aeStronglyMeasurable' h_ind_eq
have hf_ind : StronglyMeasurable[m] (s.indicator (hf.mk f)) :=
hf.stronglyMeasurable_mk.indicator hs_m
exact
hf_ind.stronglyMeasurable_of_measurableSpace_le_on hs_m hs fun x hxs =>
Set.indicator_of_not_mem hxs _
#align measure_theory.ae_strongly_measurable'.ae_strongly_measurable'_of_measurable_space_le_on MeasureTheory.AEStronglyMeasurable'.aeStronglyMeasurable'_of_measurableSpace_le_on
variable {α E' F F' 𝕜 : Type*} {p : ℝ≥0∞} [RCLike 𝕜]
-- 𝕜 for ℝ or ℂ
-- E' for an inner product space on which we compute integrals
[NormedAddCommGroup E']
[InnerProductSpace 𝕜 E'] [CompleteSpace E'] [NormedSpace ℝ E']
-- F for a Lp submodule
[NormedAddCommGroup F]
[NormedSpace 𝕜 F]
-- F' for integrals on a Lp submodule
[NormedAddCommGroup F']
[NormedSpace 𝕜 F'] [NormedSpace ℝ F'] [CompleteSpace F']
section LpMeas
/-! ## The subset `lpMeas` of `Lp` functions a.e. measurable with respect to a sub-sigma-algebra -/
variable (F)
/-- `lpMeasSubgroup F m p μ` is the subspace of `Lp F p μ` containing functions `f` verifying
`AEStronglyMeasurable' m f μ`, i.e. functions which are `μ`-a.e. equal to
an `m`-strongly measurable function. -/
def lpMeasSubgroup (m : MeasurableSpace α) [MeasurableSpace α] (p : ℝ≥0∞) (μ : Measure α) :
AddSubgroup (Lp F p μ) where
carrier := {f : Lp F p μ | AEStronglyMeasurable' m f μ}
zero_mem' := ⟨(0 : α → F), @stronglyMeasurable_zero _ _ m _ _, Lp.coeFn_zero _ _ _⟩
add_mem' {f g} hf hg := (hf.add hg).congr (Lp.coeFn_add f g).symm
neg_mem' {f} hf := AEStronglyMeasurable'.congr hf.neg (Lp.coeFn_neg f).symm
#align measure_theory.Lp_meas_subgroup MeasureTheory.lpMeasSubgroup
variable (𝕜)
/-- `lpMeas F 𝕜 m p μ` is the subspace of `Lp F p μ` containing functions `f` verifying
`AEStronglyMeasurable' m f μ`, i.e. functions which are `μ`-a.e. equal to
an `m`-strongly measurable function. -/
def lpMeas (m : MeasurableSpace α) [MeasurableSpace α] (p : ℝ≥0∞) (μ : Measure α) :
Submodule 𝕜 (Lp F p μ) where
carrier := {f : Lp F p μ | AEStronglyMeasurable' m f μ}
zero_mem' := ⟨(0 : α → F), @stronglyMeasurable_zero _ _ m _ _, Lp.coeFn_zero _ _ _⟩
add_mem' {f g} hf hg := (hf.add hg).congr (Lp.coeFn_add f g).symm
smul_mem' c f hf := (hf.const_smul c).congr (Lp.coeFn_smul c f).symm
#align measure_theory.Lp_meas MeasureTheory.lpMeas
variable {F 𝕜}
theorem mem_lpMeasSubgroup_iff_aeStronglyMeasurable' {m m0 : MeasurableSpace α} {μ : Measure α}
{f : Lp F p μ} : f ∈ lpMeasSubgroup F m p μ ↔ AEStronglyMeasurable' m f μ := by
rw [← AddSubgroup.mem_carrier, lpMeasSubgroup, Set.mem_setOf_eq]
#align measure_theory.mem_Lp_meas_subgroup_iff_ae_strongly_measurable' MeasureTheory.mem_lpMeasSubgroup_iff_aeStronglyMeasurable'
theorem mem_lpMeas_iff_aeStronglyMeasurable' {m m0 : MeasurableSpace α} {μ : Measure α}
{f : Lp F p μ} : f ∈ lpMeas F 𝕜 m p μ ↔ AEStronglyMeasurable' m f μ := by
rw [← SetLike.mem_coe, ← Submodule.mem_carrier, lpMeas, Set.mem_setOf_eq]
#align measure_theory.mem_Lp_meas_iff_ae_strongly_measurable' MeasureTheory.mem_lpMeas_iff_aeStronglyMeasurable'
theorem lpMeas.aeStronglyMeasurable' {m _ : MeasurableSpace α} {μ : Measure α}
(f : lpMeas F 𝕜 m p μ) : AEStronglyMeasurable' (β := F) m f μ :=
mem_lpMeas_iff_aeStronglyMeasurable'.mp f.mem
#align measure_theory.Lp_meas.ae_strongly_measurable' MeasureTheory.lpMeas.aeStronglyMeasurable'
theorem mem_lpMeas_self {m0 : MeasurableSpace α} (μ : Measure α) (f : Lp F p μ) :
f ∈ lpMeas F 𝕜 m0 p μ :=
mem_lpMeas_iff_aeStronglyMeasurable'.mpr (Lp.aestronglyMeasurable f)
#align measure_theory.mem_Lp_meas_self MeasureTheory.mem_lpMeas_self
theorem lpMeasSubgroup_coe {m _ : MeasurableSpace α} {μ : Measure α} {f : lpMeasSubgroup F m p μ} :
(f : _ → _) = (f : Lp F p μ) :=
rfl
#align measure_theory.Lp_meas_subgroup_coe MeasureTheory.lpMeasSubgroup_coe
theorem lpMeas_coe {m _ : MeasurableSpace α} {μ : Measure α} {f : lpMeas F 𝕜 m p μ} :
(f : _ → _) = (f : Lp F p μ) :=
rfl
#align measure_theory.Lp_meas_coe MeasureTheory.lpMeas_coe
theorem mem_lpMeas_indicatorConstLp {m m0 : MeasurableSpace α} (hm : m ≤ m0) {μ : Measure α}
{s : Set α} (hs : MeasurableSet[m] s) (hμs : μ s ≠ ∞) {c : F} :
indicatorConstLp p (hm s hs) hμs c ∈ lpMeas F 𝕜 m p μ :=
⟨s.indicator fun _ : α => c, (@stronglyMeasurable_const _ _ m _ _).indicator hs,
indicatorConstLp_coeFn⟩
#align measure_theory.mem_Lp_meas_indicator_const_Lp MeasureTheory.mem_lpMeas_indicatorConstLp
section CompleteSubspace
/-! ## The subspace `lpMeas` is complete.
We define an `IsometryEquiv` between `lpMeasSubgroup` and the `Lp` space corresponding to the
measure `μ.trim hm`. As a consequence, the completeness of `Lp` implies completeness of
`lpMeasSubgroup` (and `lpMeas`). -/
variable {ι : Type*} {m m0 : MeasurableSpace α} {μ : Measure α}
/-- If `f` belongs to `lpMeasSubgroup F m p μ`, then the measurable function it is almost
everywhere equal to (given by `AEMeasurable.mk`) belongs to `ℒp` for the measure `μ.trim hm`. -/
theorem memℒp_trim_of_mem_lpMeasSubgroup (hm : m ≤ m0) (f : Lp F p μ)
(hf_meas : f ∈ lpMeasSubgroup F m p μ) :
Memℒp (mem_lpMeasSubgroup_iff_aeStronglyMeasurable'.mp hf_meas).choose p (μ.trim hm) := by
have hf : AEStronglyMeasurable' m f μ :=
mem_lpMeasSubgroup_iff_aeStronglyMeasurable'.mp hf_meas
let g := hf.choose
obtain ⟨hg, hfg⟩ := hf.choose_spec
change Memℒp g p (μ.trim hm)
refine ⟨hg.aestronglyMeasurable, ?_⟩
have h_snorm_fg : snorm g p (μ.trim hm) = snorm f p μ := by
rw [snorm_trim hm hg]
exact snorm_congr_ae hfg.symm
rw [h_snorm_fg]
exact Lp.snorm_lt_top f
#align measure_theory.mem_ℒp_trim_of_mem_Lp_meas_subgroup MeasureTheory.memℒp_trim_of_mem_lpMeasSubgroup
/-- If `f` belongs to `Lp` for the measure `μ.trim hm`, then it belongs to the subgroup
`lpMeasSubgroup F m p μ`. -/
theorem mem_lpMeasSubgroup_toLp_of_trim (hm : m ≤ m0) (f : Lp F p (μ.trim hm)) :
(memℒp_of_memℒp_trim hm (Lp.memℒp f)).toLp f ∈ lpMeasSubgroup F m p μ := by
let hf_mem_ℒp := memℒp_of_memℒp_trim hm (Lp.memℒp f)
rw [mem_lpMeasSubgroup_iff_aeStronglyMeasurable']
refine AEStronglyMeasurable'.congr ?_ (Memℒp.coeFn_toLp hf_mem_ℒp).symm
refine aeStronglyMeasurable'_of_aeStronglyMeasurable'_trim hm ?_
exact Lp.aestronglyMeasurable f
#align measure_theory.mem_Lp_meas_subgroup_to_Lp_of_trim MeasureTheory.mem_lpMeasSubgroup_toLp_of_trim
variable (F p μ)
/-- Map from `lpMeasSubgroup` to `Lp F p (μ.trim hm)`. -/
noncomputable def lpMeasSubgroupToLpTrim (hm : m ≤ m0) (f : lpMeasSubgroup F m p μ) :
Lp F p (μ.trim hm) :=
Memℒp.toLp (mem_lpMeasSubgroup_iff_aeStronglyMeasurable'.mp f.mem).choose
-- Porting note: had to replace `f` with `f.1` here.
(memℒp_trim_of_mem_lpMeasSubgroup hm f.1 f.mem)
#align measure_theory.Lp_meas_subgroup_to_Lp_trim MeasureTheory.lpMeasSubgroupToLpTrim
variable (𝕜)
/-- Map from `lpMeas` to `Lp F p (μ.trim hm)`. -/
noncomputable def lpMeasToLpTrim (hm : m ≤ m0) (f : lpMeas F 𝕜 m p μ) : Lp F p (μ.trim hm) :=
Memℒp.toLp (mem_lpMeas_iff_aeStronglyMeasurable'.mp f.mem).choose
-- Porting note: had to replace `f` with `f.1` here.
(memℒp_trim_of_mem_lpMeasSubgroup hm f.1 f.mem)
#align measure_theory.Lp_meas_to_Lp_trim MeasureTheory.lpMeasToLpTrim
variable {𝕜}
/-- Map from `Lp F p (μ.trim hm)` to `lpMeasSubgroup`, inverse of
`lpMeasSubgroupToLpTrim`. -/
noncomputable def lpTrimToLpMeasSubgroup (hm : m ≤ m0) (f : Lp F p (μ.trim hm)) :
lpMeasSubgroup F m p μ :=
⟨(memℒp_of_memℒp_trim hm (Lp.memℒp f)).toLp f, mem_lpMeasSubgroup_toLp_of_trim hm f⟩
#align measure_theory.Lp_trim_to_Lp_meas_subgroup MeasureTheory.lpTrimToLpMeasSubgroup
variable (𝕜)
/-- Map from `Lp F p (μ.trim hm)` to `lpMeas`, inverse of `Lp_meas_to_Lp_trim`. -/
noncomputable def lpTrimToLpMeas (hm : m ≤ m0) (f : Lp F p (μ.trim hm)) : lpMeas F 𝕜 m p μ :=
⟨(memℒp_of_memℒp_trim hm (Lp.memℒp f)).toLp f, mem_lpMeasSubgroup_toLp_of_trim hm f⟩
#align measure_theory.Lp_trim_to_Lp_meas MeasureTheory.lpTrimToLpMeas
variable {F 𝕜 p μ}
theorem lpMeasSubgroupToLpTrim_ae_eq (hm : m ≤ m0) (f : lpMeasSubgroup F m p μ) :
lpMeasSubgroupToLpTrim F p μ hm f =ᵐ[μ] f :=
-- Porting note: replaced `(↑f)` with `f.1` here.
(ae_eq_of_ae_eq_trim (Memℒp.coeFn_toLp (memℒp_trim_of_mem_lpMeasSubgroup hm f.1 f.mem))).trans
(mem_lpMeasSubgroup_iff_aeStronglyMeasurable'.mp f.mem).choose_spec.2.symm
#align measure_theory.Lp_meas_subgroup_to_Lp_trim_ae_eq MeasureTheory.lpMeasSubgroupToLpTrim_ae_eq
theorem lpTrimToLpMeasSubgroup_ae_eq (hm : m ≤ m0) (f : Lp F p (μ.trim hm)) :
lpTrimToLpMeasSubgroup F p μ hm f =ᵐ[μ] f :=
-- Porting note: filled in the argument
Memℒp.coeFn_toLp (memℒp_of_memℒp_trim hm (Lp.memℒp f))
#align measure_theory.Lp_trim_to_Lp_meas_subgroup_ae_eq MeasureTheory.lpTrimToLpMeasSubgroup_ae_eq
theorem lpMeasToLpTrim_ae_eq (hm : m ≤ m0) (f : lpMeas F 𝕜 m p μ) :
lpMeasToLpTrim F 𝕜 p μ hm f =ᵐ[μ] f :=
-- Porting note: replaced `(↑f)` with `f.1` here.
(ae_eq_of_ae_eq_trim (Memℒp.coeFn_toLp (memℒp_trim_of_mem_lpMeasSubgroup hm f.1 f.mem))).trans
(mem_lpMeasSubgroup_iff_aeStronglyMeasurable'.mp f.mem).choose_spec.2.symm
#align measure_theory.Lp_meas_to_Lp_trim_ae_eq MeasureTheory.lpMeasToLpTrim_ae_eq
theorem lpTrimToLpMeas_ae_eq (hm : m ≤ m0) (f : Lp F p (μ.trim hm)) :
lpTrimToLpMeas F 𝕜 p μ hm f =ᵐ[μ] f :=
-- Porting note: filled in the argument
Memℒp.coeFn_toLp (memℒp_of_memℒp_trim hm (Lp.memℒp f))
#align measure_theory.Lp_trim_to_Lp_meas_ae_eq MeasureTheory.lpTrimToLpMeas_ae_eq
/-- `lpTrimToLpMeasSubgroup` is a right inverse of `lpMeasSubgroupToLpTrim`. -/
theorem lpMeasSubgroupToLpTrim_right_inv (hm : m ≤ m0) :
Function.RightInverse (lpTrimToLpMeasSubgroup F p μ hm) (lpMeasSubgroupToLpTrim F p μ hm) := by
intro f
ext1
refine
ae_eq_trim_of_stronglyMeasurable hm (Lp.stronglyMeasurable _) (Lp.stronglyMeasurable _) ?_
exact (lpMeasSubgroupToLpTrim_ae_eq hm _).trans (lpTrimToLpMeasSubgroup_ae_eq hm _)
#align measure_theory.Lp_meas_subgroup_to_Lp_trim_right_inv MeasureTheory.lpMeasSubgroupToLpTrim_right_inv
/-- `lpTrimToLpMeasSubgroup` is a left inverse of `lpMeasSubgroupToLpTrim`. -/
theorem lpMeasSubgroupToLpTrim_left_inv (hm : m ≤ m0) :
Function.LeftInverse (lpTrimToLpMeasSubgroup F p μ hm) (lpMeasSubgroupToLpTrim F p μ hm) := by
intro f
ext1
ext1
rw [← lpMeasSubgroup_coe]
exact (lpTrimToLpMeasSubgroup_ae_eq hm _).trans (lpMeasSubgroupToLpTrim_ae_eq hm _)
#align measure_theory.Lp_meas_subgroup_to_Lp_trim_left_inv MeasureTheory.lpMeasSubgroupToLpTrim_left_inv
theorem lpMeasSubgroupToLpTrim_add (hm : m ≤ m0) (f g : lpMeasSubgroup F m p μ) :
lpMeasSubgroupToLpTrim F p μ hm (f + g) =
lpMeasSubgroupToLpTrim F p μ hm f + lpMeasSubgroupToLpTrim F p μ hm g := by
ext1
refine EventuallyEq.trans ?_ (Lp.coeFn_add _ _).symm
refine ae_eq_trim_of_stronglyMeasurable hm (Lp.stronglyMeasurable _) ?_ ?_
· exact (Lp.stronglyMeasurable _).add (Lp.stronglyMeasurable _)
refine (lpMeasSubgroupToLpTrim_ae_eq hm _).trans ?_
refine
EventuallyEq.trans ?_
(EventuallyEq.add (lpMeasSubgroupToLpTrim_ae_eq hm f).symm
(lpMeasSubgroupToLpTrim_ae_eq hm g).symm)
refine (Lp.coeFn_add _ _).trans ?_
simp_rw [lpMeasSubgroup_coe]
filter_upwards with x using rfl
#align measure_theory.Lp_meas_subgroup_to_Lp_trim_add MeasureTheory.lpMeasSubgroupToLpTrim_add
theorem lpMeasSubgroupToLpTrim_neg (hm : m ≤ m0) (f : lpMeasSubgroup F m p μ) :
lpMeasSubgroupToLpTrim F p μ hm (-f) = -lpMeasSubgroupToLpTrim F p μ hm f := by
ext1
refine EventuallyEq.trans ?_ (Lp.coeFn_neg _).symm
refine ae_eq_trim_of_stronglyMeasurable hm (Lp.stronglyMeasurable _) ?_ ?_
· exact @StronglyMeasurable.neg _ _ _ m _ _ _ (Lp.stronglyMeasurable _)
refine (lpMeasSubgroupToLpTrim_ae_eq hm _).trans ?_
refine EventuallyEq.trans ?_ (EventuallyEq.neg (lpMeasSubgroupToLpTrim_ae_eq hm f).symm)
refine (Lp.coeFn_neg _).trans ?_
simp_rw [lpMeasSubgroup_coe]
exact eventually_of_forall fun x => by rfl
#align measure_theory.Lp_meas_subgroup_to_Lp_trim_neg MeasureTheory.lpMeasSubgroupToLpTrim_neg
| Mathlib/MeasureTheory/Function/ConditionalExpectation/AEMeasurable.lean | 426 | 430 | theorem lpMeasSubgroupToLpTrim_sub (hm : m ≤ m0) (f g : lpMeasSubgroup F m p μ) :
lpMeasSubgroupToLpTrim F p μ hm (f - g) =
lpMeasSubgroupToLpTrim F p μ hm f - lpMeasSubgroupToLpTrim F p μ hm g := by |
rw [sub_eq_add_neg, sub_eq_add_neg, lpMeasSubgroupToLpTrim_add,
lpMeasSubgroupToLpTrim_neg]
|
/-
Copyright (c) 2020 Bhavik Mehta. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Bhavik Mehta, Scott Morrison
-/
import Mathlib.CategoryTheory.Subobject.MonoOver
import Mathlib.CategoryTheory.Skeletal
import Mathlib.CategoryTheory.ConcreteCategory.Basic
import Mathlib.Tactic.ApplyFun
import Mathlib.Tactic.CategoryTheory.Elementwise
#align_import category_theory.subobject.basic from "leanprover-community/mathlib"@"70fd9563a21e7b963887c9360bd29b2393e6225a"
/-!
# Subobjects
We define `Subobject X` as the quotient (by isomorphisms) of
`MonoOver X := {f : Over X // Mono f.hom}`.
Here `MonoOver X` is a thin category (a pair of objects has at most one morphism between them),
so we can think of it as a preorder. However as it is not skeletal, it is not a partial order.
There is a coercion from `Subobject X` back to the ambient category `C`
(using choice to pick a representative), and for `P : Subobject X`,
`P.arrow : (P : C) ⟶ X` is the inclusion morphism.
We provide
* `def pullback [HasPullbacks C] (f : X ⟶ Y) : Subobject Y ⥤ Subobject X`
* `def map (f : X ⟶ Y) [Mono f] : Subobject X ⥤ Subobject Y`
* `def «exists_» [HasImages C] (f : X ⟶ Y) : Subobject X ⥤ Subobject Y`
and prove their basic properties and relationships.
These are all easy consequences of the earlier development
of the corresponding functors for `MonoOver`.
The subobjects of `X` form a preorder making them into a category. We have `X ≤ Y` if and only if
`X.arrow` factors through `Y.arrow`: see `ofLE`/`ofLEMk`/`ofMkLE`/`ofMkLEMk` and
`le_of_comm`. Similarly, to show that two subobjects are equal, we can supply an isomorphism between
the underlying objects that commutes with the arrows (`eq_of_comm`).
See also
* `CategoryTheory.Subobject.factorThru` :
an API describing factorization of morphisms through subobjects.
* `CategoryTheory.Subobject.lattice` :
the lattice structures on subobjects.
## Notes
This development originally appeared in Bhavik Mehta's "Topos theory for Lean" repository,
and was ported to mathlib by Scott Morrison.
### Implementation note
Currently we describe `pullback`, `map`, etc., as functors.
It may be better to just say that they are monotone functions,
and even avoid using categorical language entirely when describing `Subobject X`.
(It's worth keeping this in mind in future use; it should be a relatively easy change here
if it looks preferable.)
### Relation to pseudoelements
There is a separate development of pseudoelements in `CategoryTheory.Abelian.Pseudoelements`,
as a quotient (but not by isomorphism) of `Over X`.
When a morphism `f` has an image, the image represents the same pseudoelement.
In a category with images `Pseudoelements X` could be constructed as a quotient of `MonoOver X`.
In fact, in an abelian category (I'm not sure in what generality beyond that),
`Pseudoelements X` agrees with `Subobject X`, but we haven't developed this in mathlib yet.
-/
universe v₁ v₂ u₁ u₂
noncomputable section
namespace CategoryTheory
open CategoryTheory CategoryTheory.Category CategoryTheory.Limits
variable {C : Type u₁} [Category.{v₁} C] {X Y Z : C}
variable {D : Type u₂} [Category.{v₂} D]
/-!
We now construct the subobject lattice for `X : C`,
as the quotient by isomorphisms of `MonoOver X`.
Since `MonoOver X` is a thin category, we use `ThinSkeleton` to take the quotient.
Essentially all the structure defined above on `MonoOver X` descends to `Subobject X`,
with morphisms becoming inequalities, and isomorphisms becoming equations.
-/
/-- The category of subobjects of `X : C`, defined as isomorphism classes of monomorphisms into `X`.
-/
def Subobject (X : C) :=
ThinSkeleton (MonoOver X)
#align category_theory.subobject CategoryTheory.Subobject
instance (X : C) : PartialOrder (Subobject X) := by
dsimp only [Subobject]
infer_instance
namespace Subobject
-- Porting note: made it a def rather than an abbreviation
-- because Lean would make it too transparent
/-- Convenience constructor for a subobject. -/
def mk {X A : C} (f : A ⟶ X) [Mono f] : Subobject X :=
(toThinSkeleton _).obj (MonoOver.mk' f)
#align category_theory.subobject.mk CategoryTheory.Subobject.mk
section
attribute [local ext] CategoryTheory.Comma
protected theorem ind {X : C} (p : Subobject X → Prop)
(h : ∀ ⦃A : C⦄ (f : A ⟶ X) [Mono f], p (Subobject.mk f)) (P : Subobject X) : p P := by
apply Quotient.inductionOn'
intro a
exact h a.arrow
#align category_theory.subobject.ind CategoryTheory.Subobject.ind
protected theorem ind₂ {X : C} (p : Subobject X → Subobject X → Prop)
(h : ∀ ⦃A B : C⦄ (f : A ⟶ X) (g : B ⟶ X) [Mono f] [Mono g],
p (Subobject.mk f) (Subobject.mk g))
(P Q : Subobject X) : p P Q := by
apply Quotient.inductionOn₂'
intro a b
exact h a.arrow b.arrow
#align category_theory.subobject.ind₂ CategoryTheory.Subobject.ind₂
end
/-- Declare a function on subobjects of `X` by specifying a function on monomorphisms with
codomain `X`. -/
protected def lift {α : Sort*} {X : C} (F : ∀ ⦃A : C⦄ (f : A ⟶ X) [Mono f], α)
(h :
∀ ⦃A B : C⦄ (f : A ⟶ X) (g : B ⟶ X) [Mono f] [Mono g] (i : A ≅ B),
i.hom ≫ g = f → F f = F g) :
Subobject X → α := fun P =>
Quotient.liftOn' P (fun m => F m.arrow) fun m n ⟨i⟩ =>
h m.arrow n.arrow ((MonoOver.forget X ⋙ Over.forget X).mapIso i) (Over.w i.hom)
#align category_theory.subobject.lift CategoryTheory.Subobject.lift
@[simp]
protected theorem lift_mk {α : Sort*} {X : C} (F : ∀ ⦃A : C⦄ (f : A ⟶ X) [Mono f], α) {h A}
(f : A ⟶ X) [Mono f] : Subobject.lift F h (Subobject.mk f) = F f :=
rfl
#align category_theory.subobject.lift_mk CategoryTheory.Subobject.lift_mk
/-- The category of subobjects is equivalent to the `MonoOver` category. It is more convenient to
use the former due to the partial order instance, but oftentimes it is easier to define structures
on the latter. -/
noncomputable def equivMonoOver (X : C) : Subobject X ≌ MonoOver X :=
ThinSkeleton.equivalence _
#align category_theory.subobject.equiv_mono_over CategoryTheory.Subobject.equivMonoOver
/-- Use choice to pick a representative `MonoOver X` for each `Subobject X`.
-/
noncomputable def representative {X : C} : Subobject X ⥤ MonoOver X :=
(equivMonoOver X).functor
#align category_theory.subobject.representative CategoryTheory.Subobject.representative
/-- Starting with `A : MonoOver X`, we can take its equivalence class in `Subobject X`
then pick an arbitrary representative using `representative.obj`.
This is isomorphic (in `MonoOver X`) to the original `A`.
-/
noncomputable def representativeIso {X : C} (A : MonoOver X) :
representative.obj ((toThinSkeleton _).obj A) ≅ A :=
(equivMonoOver X).counitIso.app A
#align category_theory.subobject.representative_iso CategoryTheory.Subobject.representativeIso
/-- Use choice to pick a representative underlying object in `C` for any `Subobject X`.
Prefer to use the coercion `P : C` rather than explicitly writing `underlying.obj P`.
-/
noncomputable def underlying {X : C} : Subobject X ⥤ C :=
representative ⋙ MonoOver.forget _ ⋙ Over.forget _
#align category_theory.subobject.underlying CategoryTheory.Subobject.underlying
instance : CoeOut (Subobject X) C where coe Y := underlying.obj Y
-- Porting note: removed as it has become a syntactic tautology
-- @[simp]
-- theorem underlying_as_coe {X : C} (P : Subobject X) : underlying.obj P = P :=
-- rfl
-- #align category_theory.subobject.underlying_as_coe CategoryTheory.Subobject.underlying_as_coe
/-- If we construct a `Subobject Y` from an explicit `f : X ⟶ Y` with `[Mono f]`,
then pick an arbitrary choice of underlying object `(Subobject.mk f : C)` back in `C`,
it is isomorphic (in `C`) to the original `X`.
-/
noncomputable def underlyingIso {X Y : C} (f : X ⟶ Y) [Mono f] : (Subobject.mk f : C) ≅ X :=
(MonoOver.forget _ ⋙ Over.forget _).mapIso (representativeIso (MonoOver.mk' f))
#align category_theory.subobject.underlying_iso CategoryTheory.Subobject.underlyingIso
/-- The morphism in `C` from the arbitrarily chosen underlying object to the ambient object.
-/
noncomputable def arrow {X : C} (Y : Subobject X) : (Y : C) ⟶ X :=
(representative.obj Y).obj.hom
#align category_theory.subobject.arrow CategoryTheory.Subobject.arrow
instance arrow_mono {X : C} (Y : Subobject X) : Mono Y.arrow :=
(representative.obj Y).property
#align category_theory.subobject.arrow_mono CategoryTheory.Subobject.arrow_mono
@[simp]
theorem arrow_congr {A : C} (X Y : Subobject A) (h : X = Y) :
eqToHom (congr_arg (fun X : Subobject A => (X : C)) h) ≫ Y.arrow = X.arrow := by
induction h
simp
#align category_theory.subobject.arrow_congr CategoryTheory.Subobject.arrow_congr
@[simp]
theorem representative_coe (Y : Subobject X) : (representative.obj Y : C) = (Y : C) :=
rfl
#align category_theory.subobject.representative_coe CategoryTheory.Subobject.representative_coe
@[simp]
theorem representative_arrow (Y : Subobject X) : (representative.obj Y).arrow = Y.arrow :=
rfl
#align category_theory.subobject.representative_arrow CategoryTheory.Subobject.representative_arrow
@[reassoc (attr := simp)]
theorem underlying_arrow {X : C} {Y Z : Subobject X} (f : Y ⟶ Z) :
underlying.map f ≫ arrow Z = arrow Y :=
Over.w (representative.map f)
#align category_theory.subobject.underlying_arrow CategoryTheory.Subobject.underlying_arrow
@[reassoc (attr := simp), elementwise (attr := simp)]
theorem underlyingIso_arrow {X Y : C} (f : X ⟶ Y) [Mono f] :
(underlyingIso f).inv ≫ (Subobject.mk f).arrow = f :=
Over.w _
#align category_theory.subobject.underlying_iso_arrow CategoryTheory.Subobject.underlyingIso_arrow
@[reassoc (attr := simp)]
theorem underlyingIso_hom_comp_eq_mk {X Y : C} (f : X ⟶ Y) [Mono f] :
(underlyingIso f).hom ≫ f = (mk f).arrow :=
(Iso.eq_inv_comp _).1 (underlyingIso_arrow f).symm
#align category_theory.subobject.underlying_iso_hom_comp_eq_mk CategoryTheory.Subobject.underlyingIso_hom_comp_eq_mk
/-- Two morphisms into a subobject are equal exactly if
the morphisms into the ambient object are equal -/
@[ext]
theorem eq_of_comp_arrow_eq {X Y : C} {P : Subobject Y} {f g : X ⟶ P}
(h : f ≫ P.arrow = g ≫ P.arrow) : f = g :=
(cancel_mono P.arrow).mp h
#align category_theory.subobject.eq_of_comp_arrow_eq CategoryTheory.Subobject.eq_of_comp_arrow_eq
theorem mk_le_mk_of_comm {B A₁ A₂ : C} {f₁ : A₁ ⟶ B} {f₂ : A₂ ⟶ B} [Mono f₁] [Mono f₂] (g : A₁ ⟶ A₂)
(w : g ≫ f₂ = f₁) : mk f₁ ≤ mk f₂ :=
⟨MonoOver.homMk _ w⟩
#align category_theory.subobject.mk_le_mk_of_comm CategoryTheory.Subobject.mk_le_mk_of_comm
@[simp]
theorem mk_arrow (P : Subobject X) : mk P.arrow = P :=
Quotient.inductionOn' P fun Q => by
obtain ⟨e⟩ := @Quotient.mk_out' _ (isIsomorphicSetoid _) Q
exact Quotient.sound' ⟨MonoOver.isoMk (Iso.refl _) ≪≫ e⟩
#align category_theory.subobject.mk_arrow CategoryTheory.Subobject.mk_arrow
theorem le_of_comm {B : C} {X Y : Subobject B} (f : (X : C) ⟶ (Y : C)) (w : f ≫ Y.arrow = X.arrow) :
X ≤ Y := by
convert mk_le_mk_of_comm _ w <;> simp
#align category_theory.subobject.le_of_comm CategoryTheory.Subobject.le_of_comm
theorem le_mk_of_comm {B A : C} {X : Subobject B} {f : A ⟶ B} [Mono f] (g : (X : C) ⟶ A)
(w : g ≫ f = X.arrow) : X ≤ mk f :=
le_of_comm (g ≫ (underlyingIso f).inv) <| by simp [w]
#align category_theory.subobject.le_mk_of_comm CategoryTheory.Subobject.le_mk_of_comm
theorem mk_le_of_comm {B A : C} {X : Subobject B} {f : A ⟶ B} [Mono f] (g : A ⟶ (X : C))
(w : g ≫ X.arrow = f) : mk f ≤ X :=
le_of_comm ((underlyingIso f).hom ≫ g) <| by simp [w]
#align category_theory.subobject.mk_le_of_comm CategoryTheory.Subobject.mk_le_of_comm
/-- To show that two subobjects are equal, it suffices to exhibit an isomorphism commuting with
the arrows. -/
@[ext]
theorem eq_of_comm {B : C} {X Y : Subobject B} (f : (X : C) ≅ (Y : C))
(w : f.hom ≫ Y.arrow = X.arrow) : X = Y :=
le_antisymm (le_of_comm f.hom w) <| le_of_comm f.inv <| f.inv_comp_eq.2 w.symm
#align category_theory.subobject.eq_of_comm CategoryTheory.Subobject.eq_of_comm
-- Porting note (#11182): removed @[ext]
/-- To show that two subobjects are equal, it suffices to exhibit an isomorphism commuting with
the arrows. -/
theorem eq_mk_of_comm {B A : C} {X : Subobject B} (f : A ⟶ B) [Mono f] (i : (X : C) ≅ A)
(w : i.hom ≫ f = X.arrow) : X = mk f :=
eq_of_comm (i.trans (underlyingIso f).symm) <| by simp [w]
#align category_theory.subobject.eq_mk_of_comm CategoryTheory.Subobject.eq_mk_of_comm
-- Porting note (#11182): removed @[ext]
/-- To show that two subobjects are equal, it suffices to exhibit an isomorphism commuting with
the arrows. -/
theorem mk_eq_of_comm {B A : C} {X : Subobject B} (f : A ⟶ B) [Mono f] (i : A ≅ (X : C))
(w : i.hom ≫ X.arrow = f) : mk f = X :=
Eq.symm <| eq_mk_of_comm _ i.symm <| by rw [Iso.symm_hom, Iso.inv_comp_eq, w]
#align category_theory.subobject.mk_eq_of_comm CategoryTheory.Subobject.mk_eq_of_comm
-- Porting note (#11182): removed @[ext]
/-- To show that two subobjects are equal, it suffices to exhibit an isomorphism commuting with
the arrows. -/
theorem mk_eq_mk_of_comm {B A₁ A₂ : C} (f : A₁ ⟶ B) (g : A₂ ⟶ B) [Mono f] [Mono g] (i : A₁ ≅ A₂)
(w : i.hom ≫ g = f) : mk f = mk g :=
eq_mk_of_comm _ ((underlyingIso f).trans i) <| by simp [w]
#align category_theory.subobject.mk_eq_mk_of_comm CategoryTheory.Subobject.mk_eq_mk_of_comm
-- We make `X` and `Y` explicit arguments here so that when `ofLE` appears in goal statements
-- it is possible to see its source and target
-- (`h` will just display as `_`, because it is in `Prop`).
/-- An inequality of subobjects is witnessed by some morphism between the corresponding objects. -/
def ofLE {B : C} (X Y : Subobject B) (h : X ≤ Y) : (X : C) ⟶ (Y : C) :=
underlying.map <| h.hom
#align category_theory.subobject.of_le CategoryTheory.Subobject.ofLE
@[reassoc (attr := simp)]
theorem ofLE_arrow {B : C} {X Y : Subobject B} (h : X ≤ Y) : ofLE X Y h ≫ Y.arrow = X.arrow :=
underlying_arrow _
#align category_theory.subobject.of_le_arrow CategoryTheory.Subobject.ofLE_arrow
instance {B : C} (X Y : Subobject B) (h : X ≤ Y) : Mono (ofLE X Y h) := by
fconstructor
intro Z f g w
replace w := w =≫ Y.arrow
ext
simpa using w
theorem ofLE_mk_le_mk_of_comm {B A₁ A₂ : C} {f₁ : A₁ ⟶ B} {f₂ : A₂ ⟶ B} [Mono f₁] [Mono f₂]
(g : A₁ ⟶ A₂) (w : g ≫ f₂ = f₁) :
ofLE _ _ (mk_le_mk_of_comm g w) = (underlyingIso _).hom ≫ g ≫ (underlyingIso _).inv := by
ext
simp [w]
#align category_theory.subobject.of_le_mk_le_mk_of_comm CategoryTheory.Subobject.ofLE_mk_le_mk_of_comm
/-- An inequality of subobjects is witnessed by some morphism between the corresponding objects. -/
def ofLEMk {B A : C} (X : Subobject B) (f : A ⟶ B) [Mono f] (h : X ≤ mk f) : (X : C) ⟶ A :=
ofLE X (mk f) h ≫ (underlyingIso f).hom
#align category_theory.subobject.of_le_mk CategoryTheory.Subobject.ofLEMk
instance {B A : C} (X : Subobject B) (f : A ⟶ B) [Mono f] (h : X ≤ mk f) :
Mono (ofLEMk X f h) := by
dsimp only [ofLEMk]
infer_instance
@[simp]
theorem ofLEMk_comp {B A : C} {X : Subobject B} {f : A ⟶ B} [Mono f] (h : X ≤ mk f) :
ofLEMk X f h ≫ f = X.arrow := by simp [ofLEMk]
#align category_theory.subobject.of_le_mk_comp CategoryTheory.Subobject.ofLEMk_comp
/-- An inequality of subobjects is witnessed by some morphism between the corresponding objects. -/
def ofMkLE {B A : C} (f : A ⟶ B) [Mono f] (X : Subobject B) (h : mk f ≤ X) : A ⟶ (X : C) :=
(underlyingIso f).inv ≫ ofLE (mk f) X h
#align category_theory.subobject.of_mk_le CategoryTheory.Subobject.ofMkLE
instance {B A : C} (f : A ⟶ B) [Mono f] (X : Subobject B) (h : mk f ≤ X) :
Mono (ofMkLE f X h) := by
dsimp only [ofMkLE]
infer_instance
@[simp]
theorem ofMkLE_arrow {B A : C} {f : A ⟶ B} [Mono f] {X : Subobject B} (h : mk f ≤ X) :
ofMkLE f X h ≫ X.arrow = f := by simp [ofMkLE]
#align category_theory.subobject.of_mk_le_arrow CategoryTheory.Subobject.ofMkLE_arrow
/-- An inequality of subobjects is witnessed by some morphism between the corresponding objects. -/
def ofMkLEMk {B A₁ A₂ : C} (f : A₁ ⟶ B) (g : A₂ ⟶ B) [Mono f] [Mono g] (h : mk f ≤ mk g) :
A₁ ⟶ A₂ :=
(underlyingIso f).inv ≫ ofLE (mk f) (mk g) h ≫ (underlyingIso g).hom
#align category_theory.subobject.of_mk_le_mk CategoryTheory.Subobject.ofMkLEMk
instance {B A₁ A₂ : C} (f : A₁ ⟶ B) (g : A₂ ⟶ B) [Mono f] [Mono g] (h : mk f ≤ mk g) :
Mono (ofMkLEMk f g h) := by
dsimp only [ofMkLEMk]
infer_instance
@[simp]
theorem ofMkLEMk_comp {B A₁ A₂ : C} {f : A₁ ⟶ B} {g : A₂ ⟶ B} [Mono f] [Mono g] (h : mk f ≤ mk g) :
ofMkLEMk f g h ≫ g = f := by simp [ofMkLEMk]
#align category_theory.subobject.of_mk_le_mk_comp CategoryTheory.Subobject.ofMkLEMk_comp
@[reassoc (attr := simp)]
theorem ofLE_comp_ofLE {B : C} (X Y Z : Subobject B) (h₁ : X ≤ Y) (h₂ : Y ≤ Z) :
ofLE X Y h₁ ≫ ofLE Y Z h₂ = ofLE X Z (h₁.trans h₂) := by
simp only [ofLE, ← Functor.map_comp underlying]
congr 1
#align category_theory.subobject.of_le_comp_of_le CategoryTheory.Subobject.ofLE_comp_ofLE
@[reassoc (attr := simp)]
theorem ofLE_comp_ofLEMk {B A : C} (X Y : Subobject B) (f : A ⟶ B) [Mono f] (h₁ : X ≤ Y)
(h₂ : Y ≤ mk f) : ofLE X Y h₁ ≫ ofLEMk Y f h₂ = ofLEMk X f (h₁.trans h₂) := by
simp only [ofMkLE, ofLEMk, ofLE, ← Functor.map_comp_assoc underlying]
congr 1
#align category_theory.subobject.of_le_comp_of_le_mk CategoryTheory.Subobject.ofLE_comp_ofLEMk
@[reassoc (attr := simp)]
theorem ofLEMk_comp_ofMkLE {B A : C} (X : Subobject B) (f : A ⟶ B) [Mono f] (Y : Subobject B)
(h₁ : X ≤ mk f) (h₂ : mk f ≤ Y) : ofLEMk X f h₁ ≫ ofMkLE f Y h₂ = ofLE X Y (h₁.trans h₂) := by
simp only [ofMkLE, ofLEMk, ofLE, ← Functor.map_comp underlying, assoc, Iso.hom_inv_id_assoc]
congr 1
#align category_theory.subobject.of_le_mk_comp_of_mk_le CategoryTheory.Subobject.ofLEMk_comp_ofMkLE
@[reassoc (attr := simp)]
theorem ofLEMk_comp_ofMkLEMk {B A₁ A₂ : C} (X : Subobject B) (f : A₁ ⟶ B) [Mono f] (g : A₂ ⟶ B)
[Mono g] (h₁ : X ≤ mk f) (h₂ : mk f ≤ mk g) :
ofLEMk X f h₁ ≫ ofMkLEMk f g h₂ = ofLEMk X g (h₁.trans h₂) := by
simp only [ofMkLE, ofLEMk, ofLE, ofMkLEMk, ← Functor.map_comp_assoc underlying,
assoc, Iso.hom_inv_id_assoc]
congr 1
#align category_theory.subobject.of_le_mk_comp_of_mk_le_mk CategoryTheory.Subobject.ofLEMk_comp_ofMkLEMk
@[reassoc (attr := simp)]
theorem ofMkLE_comp_ofLE {B A₁ : C} (f : A₁ ⟶ B) [Mono f] (X Y : Subobject B) (h₁ : mk f ≤ X)
(h₂ : X ≤ Y) : ofMkLE f X h₁ ≫ ofLE X Y h₂ = ofMkLE f Y (h₁.trans h₂) := by
simp only [ofMkLE, ofLEMk, ofLE, ofMkLEMk, ← Functor.map_comp underlying,
assoc]
congr 1
#align category_theory.subobject.of_mk_le_comp_of_le CategoryTheory.Subobject.ofMkLE_comp_ofLE
@[reassoc (attr := simp)]
theorem ofMkLE_comp_ofLEMk {B A₁ A₂ : C} (f : A₁ ⟶ B) [Mono f] (X : Subobject B) (g : A₂ ⟶ B)
[Mono g] (h₁ : mk f ≤ X) (h₂ : X ≤ mk g) :
ofMkLE f X h₁ ≫ ofLEMk X g h₂ = ofMkLEMk f g (h₁.trans h₂) := by
simp only [ofMkLE, ofLEMk, ofLE, ofMkLEMk, ← Functor.map_comp_assoc underlying, assoc]
congr 1
#align category_theory.subobject.of_mk_le_comp_of_le_mk CategoryTheory.Subobject.ofMkLE_comp_ofLEMk
@[reassoc (attr := simp)]
theorem ofMkLEMk_comp_ofMkLE {B A₁ A₂ : C} (f : A₁ ⟶ B) [Mono f] (g : A₂ ⟶ B) [Mono g]
(X : Subobject B) (h₁ : mk f ≤ mk g) (h₂ : mk g ≤ X) :
ofMkLEMk f g h₁ ≫ ofMkLE g X h₂ = ofMkLE f X (h₁.trans h₂) := by
simp only [ofMkLE, ofLEMk, ofLE, ofMkLEMk, ← Functor.map_comp underlying,
assoc, Iso.hom_inv_id_assoc]
congr 1
#align category_theory.subobject.of_mk_le_mk_comp_of_mk_le CategoryTheory.Subobject.ofMkLEMk_comp_ofMkLE
@[reassoc (attr := simp)]
theorem ofMkLEMk_comp_ofMkLEMk {B A₁ A₂ A₃ : C} (f : A₁ ⟶ B) [Mono f] (g : A₂ ⟶ B) [Mono g]
(h : A₃ ⟶ B) [Mono h] (h₁ : mk f ≤ mk g) (h₂ : mk g ≤ mk h) :
ofMkLEMk f g h₁ ≫ ofMkLEMk g h h₂ = ofMkLEMk f h (h₁.trans h₂) := by
simp only [ofMkLE, ofLEMk, ofLE, ofMkLEMk, ← Functor.map_comp_assoc underlying, assoc,
Iso.hom_inv_id_assoc]
congr 1
#align category_theory.subobject.of_mk_le_mk_comp_of_mk_le_mk CategoryTheory.Subobject.ofMkLEMk_comp_ofMkLEMk
@[simp]
theorem ofLE_refl {B : C} (X : Subobject B) : ofLE X X le_rfl = 𝟙 _ := by
apply (cancel_mono X.arrow).mp
simp
#align category_theory.subobject.of_le_refl CategoryTheory.Subobject.ofLE_refl
@[simp]
theorem ofMkLEMk_refl {B A₁ : C} (f : A₁ ⟶ B) [Mono f] : ofMkLEMk f f le_rfl = 𝟙 _ := by
apply (cancel_mono f).mp
simp
#align category_theory.subobject.of_mk_le_mk_refl CategoryTheory.Subobject.ofMkLEMk_refl
-- As with `ofLE`, we have `X` and `Y` as explicit arguments for readability.
/-- An equality of subobjects gives an isomorphism of the corresponding objects.
(One could use `underlying.mapIso (eqToIso h))` here, but this is more readable.) -/
@[simps]
def isoOfEq {B : C} (X Y : Subobject B) (h : X = Y) : (X : C) ≅ (Y : C) where
hom := ofLE _ _ h.le
inv := ofLE _ _ h.ge
#align category_theory.subobject.iso_of_eq CategoryTheory.Subobject.isoOfEq
/-- An equality of subobjects gives an isomorphism of the corresponding objects. -/
@[simps]
def isoOfEqMk {B A : C} (X : Subobject B) (f : A ⟶ B) [Mono f] (h : X = mk f) : (X : C) ≅ A where
hom := ofLEMk X f h.le
inv := ofMkLE f X h.ge
#align category_theory.subobject.iso_of_eq_mk CategoryTheory.Subobject.isoOfEqMk
/-- An equality of subobjects gives an isomorphism of the corresponding objects. -/
@[simps]
def isoOfMkEq {B A : C} (f : A ⟶ B) [Mono f] (X : Subobject B) (h : mk f = X) : A ≅ (X : C) where
hom := ofMkLE f X h.le
inv := ofLEMk X f h.ge
#align category_theory.subobject.iso_of_mk_eq CategoryTheory.Subobject.isoOfMkEq
/-- An equality of subobjects gives an isomorphism of the corresponding objects. -/
@[simps]
def isoOfMkEqMk {B A₁ A₂ : C} (f : A₁ ⟶ B) (g : A₂ ⟶ B) [Mono f] [Mono g] (h : mk f = mk g) :
A₁ ≅ A₂ where
hom := ofMkLEMk f g h.le
inv := ofMkLEMk g f h.ge
#align category_theory.subobject.iso_of_mk_eq_mk CategoryTheory.Subobject.isoOfMkEqMk
end Subobject
open CategoryTheory.Limits
namespace Subobject
/-- Any functor `MonoOver X ⥤ MonoOver Y` descends to a functor
`Subobject X ⥤ Subobject Y`, because `MonoOver Y` is thin. -/
def lower {Y : D} (F : MonoOver X ⥤ MonoOver Y) : Subobject X ⥤ Subobject Y :=
ThinSkeleton.map F
#align category_theory.subobject.lower CategoryTheory.Subobject.lower
/-- Isomorphic functors become equal when lowered to `Subobject`.
(It's not as evil as usual to talk about equality between functors
because the categories are thin and skeletal.) -/
theorem lower_iso (F₁ F₂ : MonoOver X ⥤ MonoOver Y) (h : F₁ ≅ F₂) : lower F₁ = lower F₂ :=
ThinSkeleton.map_iso_eq h
#align category_theory.subobject.lower_iso CategoryTheory.Subobject.lower_iso
/-- A ternary version of `Subobject.lower`. -/
def lower₂ (F : MonoOver X ⥤ MonoOver Y ⥤ MonoOver Z) : Subobject X ⥤ Subobject Y ⥤ Subobject Z :=
ThinSkeleton.map₂ F
#align category_theory.subobject.lower₂ CategoryTheory.Subobject.lower₂
@[simp]
theorem lower_comm (F : MonoOver Y ⥤ MonoOver X) :
toThinSkeleton _ ⋙ lower F = F ⋙ toThinSkeleton _ :=
rfl
#align category_theory.subobject.lower_comm CategoryTheory.Subobject.lower_comm
/-- An adjunction between `MonoOver A` and `MonoOver B` gives an adjunction
between `Subobject A` and `Subobject B`. -/
def lowerAdjunction {A : C} {B : D} {L : MonoOver A ⥤ MonoOver B} {R : MonoOver B ⥤ MonoOver A}
(h : L ⊣ R) : lower L ⊣ lower R :=
ThinSkeleton.lowerAdjunction _ _ h
#align category_theory.subobject.lower_adjunction CategoryTheory.Subobject.lowerAdjunction
/-- An equivalence between `MonoOver A` and `MonoOver B` gives an equivalence
between `Subobject A` and `Subobject B`. -/
@[simps]
def lowerEquivalence {A : C} {B : D} (e : MonoOver A ≌ MonoOver B) : Subobject A ≌ Subobject B where
functor := lower e.functor
inverse := lower e.inverse
unitIso := by
apply eqToIso
convert ThinSkeleton.map_iso_eq e.unitIso
· exact ThinSkeleton.map_id_eq.symm
· exact (ThinSkeleton.map_comp_eq _ _).symm
counitIso := by
apply eqToIso
convert ThinSkeleton.map_iso_eq e.counitIso
· exact (ThinSkeleton.map_comp_eq _ _).symm
· exact ThinSkeleton.map_id_eq.symm
#align category_theory.subobject.lower_equivalence CategoryTheory.Subobject.lowerEquivalence
section Pullback
variable [HasPullbacks C]
/-- When `C` has pullbacks, a morphism `f : X ⟶ Y` induces a functor `Subobject Y ⥤ Subobject X`,
by pulling back a monomorphism along `f`. -/
def pullback (f : X ⟶ Y) : Subobject Y ⥤ Subobject X :=
lower (MonoOver.pullback f)
#align category_theory.subobject.pullback CategoryTheory.Subobject.pullback
theorem pullback_id (x : Subobject X) : (pullback (𝟙 X)).obj x = x := by
induction' x using Quotient.inductionOn' with f
exact Quotient.sound ⟨MonoOver.pullbackId.app f⟩
#align category_theory.subobject.pullback_id CategoryTheory.Subobject.pullback_id
theorem pullback_comp (f : X ⟶ Y) (g : Y ⟶ Z) (x : Subobject Z) :
(pullback (f ≫ g)).obj x = (pullback f).obj ((pullback g).obj x) := by
induction' x using Quotient.inductionOn' with t
exact Quotient.sound ⟨(MonoOver.pullbackComp _ _).app t⟩
#align category_theory.subobject.pullback_comp CategoryTheory.Subobject.pullback_comp
instance (f : X ⟶ Y) : (pullback f).Faithful where
end Pullback
section Map
/-- We can map subobjects of `X` to subobjects of `Y`
by post-composition with a monomorphism `f : X ⟶ Y`.
-/
def map (f : X ⟶ Y) [Mono f] : Subobject X ⥤ Subobject Y :=
lower (MonoOver.map f)
#align category_theory.subobject.map CategoryTheory.Subobject.map
theorem map_id (x : Subobject X) : (map (𝟙 X)).obj x = x := by
induction' x using Quotient.inductionOn' with f
exact Quotient.sound ⟨(MonoOver.mapId _).app f⟩
#align category_theory.subobject.map_id CategoryTheory.Subobject.map_id
theorem map_comp (f : X ⟶ Y) (g : Y ⟶ Z) [Mono f] [Mono g] (x : Subobject X) :
(map (f ≫ g)).obj x = (map g).obj ((map f).obj x) := by
induction' x using Quotient.inductionOn' with t
exact Quotient.sound ⟨(MonoOver.mapComp _ _).app t⟩
#align category_theory.subobject.map_comp CategoryTheory.Subobject.map_comp
/-- Isomorphic objects have equivalent subobject lattices. -/
def mapIso {A B : C} (e : A ≅ B) : Subobject A ≌ Subobject B :=
lowerEquivalence (MonoOver.mapIso e)
#align category_theory.subobject.map_iso CategoryTheory.Subobject.mapIso
-- Porting note: the note below doesn't seem true anymore
-- @[simps] here generates a lemma `map_iso_to_order_iso_to_equiv_symm_apply`
-- whose left hand side is not in simp normal form.
/-- In fact, there's a type level bijection between the subobjects of isomorphic objects,
which preserves the order. -/
def mapIsoToOrderIso (e : X ≅ Y) : Subobject X ≃o Subobject Y where
toFun := (map e.hom).obj
invFun := (map e.inv).obj
left_inv g := by simp_rw [← map_comp, e.hom_inv_id, map_id]
right_inv g := by simp_rw [← map_comp, e.inv_hom_id, map_id]
map_rel_iff' {A B} := by
dsimp
constructor
· intro h
apply_fun (map e.inv).obj at h
· simpa only [← map_comp, e.hom_inv_id, map_id] using h
· apply Functor.monotone
· intro h
apply_fun (map e.hom).obj at h
· exact h
· apply Functor.monotone
#align category_theory.subobject.map_iso_to_order_iso CategoryTheory.Subobject.mapIsoToOrderIso
@[simp]
theorem mapIsoToOrderIso_apply (e : X ≅ Y) (P : Subobject X) :
mapIsoToOrderIso e P = (map e.hom).obj P :=
rfl
#align category_theory.subobject.map_iso_to_order_iso_apply CategoryTheory.Subobject.mapIsoToOrderIso_apply
@[simp]
theorem mapIsoToOrderIso_symm_apply (e : X ≅ Y) (Q : Subobject Y) :
(mapIsoToOrderIso e).symm Q = (map e.inv).obj Q :=
rfl
#align category_theory.subobject.map_iso_to_order_iso_symm_apply CategoryTheory.Subobject.mapIsoToOrderIso_symm_apply
/-- `map f : Subobject X ⥤ Subobject Y` is
the left adjoint of `pullback f : Subobject Y ⥤ Subobject X`. -/
def mapPullbackAdj [HasPullbacks C] (f : X ⟶ Y) [Mono f] : map f ⊣ pullback f :=
lowerAdjunction (MonoOver.mapPullbackAdj f)
#align category_theory.subobject.map_pullback_adj CategoryTheory.Subobject.mapPullbackAdj
@[simp]
theorem pullback_map_self [HasPullbacks C] (f : X ⟶ Y) [Mono f] (g : Subobject X) :
(pullback f).obj ((map f).obj g) = g := by
revert g
exact Quotient.ind (fun g' => Quotient.sound ⟨(MonoOver.pullbackMapSelf f).app _⟩)
#align category_theory.subobject.pullback_map_self CategoryTheory.Subobject.pullback_map_self
| Mathlib/CategoryTheory/Subobject/Basic.lean | 644 | 662 | theorem map_pullback [HasPullbacks C] {X Y Z W : C} {f : X ⟶ Y} {g : X ⟶ Z} {h : Y ⟶ W} {k : Z ⟶ W}
[Mono h] [Mono g] (comm : f ≫ h = g ≫ k) (t : IsLimit (PullbackCone.mk f g comm))
(p : Subobject Y) : (map g).obj ((pullback f).obj p) = (pullback k).obj ((map h).obj p) := by |
revert p
apply Quotient.ind'
intro a
apply Quotient.sound
apply ThinSkeleton.equiv_of_both_ways
· refine MonoOver.homMk (pullback.lift pullback.fst _ ?_) (pullback.lift_snd _ _ _)
change _ ≫ a.arrow ≫ h = (pullback.snd ≫ g) ≫ _
rw [assoc, ← comm, pullback.condition_assoc]
· refine MonoOver.homMk (pullback.lift pullback.fst
(PullbackCone.IsLimit.lift t (pullback.fst ≫ a.arrow) pullback.snd _)
(PullbackCone.IsLimit.lift_fst _ _ _ ?_).symm) ?_
· rw [← pullback.condition, assoc]
rfl
· dsimp
rw [pullback.lift_snd_assoc]
apply PullbackCone.IsLimit.lift_snd
|
/-
Copyright (c) 2021 Rémy Degenne. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Rémy Degenne
-/
import Mathlib.MeasureTheory.Constructions.BorelSpace.Order
import Mathlib.Order.Filter.ENNReal
#align_import measure_theory.function.ess_sup from "leanprover-community/mathlib"@"bf6a01357ff5684b1ebcd0f1a13be314fc82c0bf"
/-!
# Essential supremum and infimum
We define the essential supremum and infimum of a function `f : α → β` with respect to a measure
`μ` on `α`. The essential supremum is the infimum of the constants `c : β` such that `f x ≤ c`
almost everywhere.
TODO: The essential supremum of functions `α → ℝ≥0∞` is used in particular to define the norm in
the `L∞` space (see `Mathlib.MeasureTheory.Function.LpSpace`).
There is a different quantity which is sometimes also called essential supremum: the least
upper-bound among measurable functions of a family of measurable functions (in an almost-everywhere
sense). We do not define that quantity here, which is simply the supremum of a map with values in
`α →ₘ[μ] β` (see `Mathlib.MeasureTheory.Function.AEEqFun`).
## Main definitions
* `essSup f μ := (ae μ).limsup f`
* `essInf f μ := (ae μ).liminf f`
-/
open MeasureTheory Filter Set TopologicalSpace
open ENNReal MeasureTheory NNReal
variable {α β : Type*} {m : MeasurableSpace α} {μ ν : Measure α}
section ConditionallyCompleteLattice
variable [ConditionallyCompleteLattice β]
/-- Essential supremum of `f` with respect to measure `μ`: the smallest `c : β` such that
`f x ≤ c` a.e. -/
def essSup {_ : MeasurableSpace α} (f : α → β) (μ : Measure α) :=
(ae μ).limsup f
#align ess_sup essSup
/-- Essential infimum of `f` with respect to measure `μ`: the greatest `c : β` such that
`c ≤ f x` a.e. -/
def essInf {_ : MeasurableSpace α} (f : α → β) (μ : Measure α) :=
(ae μ).liminf f
#align ess_inf essInf
theorem essSup_congr_ae {f g : α → β} (hfg : f =ᵐ[μ] g) : essSup f μ = essSup g μ :=
limsup_congr hfg
#align ess_sup_congr_ae essSup_congr_ae
theorem essInf_congr_ae {f g : α → β} (hfg : f =ᵐ[μ] g) : essInf f μ = essInf g μ :=
@essSup_congr_ae α βᵒᵈ _ _ _ _ _ hfg
#align ess_inf_congr_ae essInf_congr_ae
@[simp]
theorem essSup_const' [NeZero μ] (c : β) : essSup (fun _ : α => c) μ = c :=
limsup_const _
#align ess_sup_const' essSup_const'
@[simp]
theorem essInf_const' [NeZero μ] (c : β) : essInf (fun _ : α => c) μ = c :=
liminf_const _
#align ess_inf_const' essInf_const'
theorem essSup_const (c : β) (hμ : μ ≠ 0) : essSup (fun _ : α => c) μ = c :=
have := NeZero.mk hμ; essSup_const' _
#align ess_sup_const essSup_const
theorem essInf_const (c : β) (hμ : μ ≠ 0) : essInf (fun _ : α => c) μ = c :=
have := NeZero.mk hμ; essInf_const' _
#align ess_inf_const essInf_const
end ConditionallyCompleteLattice
section ConditionallyCompleteLinearOrder
variable [ConditionallyCompleteLinearOrder β] {x : β} {f : α → β}
theorem essSup_eq_sInf {m : MeasurableSpace α} (μ : Measure α) (f : α → β) :
essSup f μ = sInf { a | μ { x | a < f x } = 0 } := by
dsimp [essSup, limsup, limsSup]
simp only [eventually_map, ae_iff, not_le]
#align ess_sup_eq_Inf essSup_eq_sInf
theorem essInf_eq_sSup {m : MeasurableSpace α} (μ : Measure α) (f : α → β) :
essInf f μ = sSup { a | μ { x | f x < a } = 0 } := by
dsimp [essInf, liminf, limsInf]
simp only [eventually_map, ae_iff, not_le]
#align ess_inf_eq_Sup essInf_eq_sSup
theorem ae_lt_of_essSup_lt (hx : essSup f μ < x)
(hf : IsBoundedUnder (· ≤ ·) (ae μ) f := by isBoundedDefault) :
∀ᵐ y ∂μ, f y < x :=
eventually_lt_of_limsup_lt hx hf
#align ae_lt_of_ess_sup_lt ae_lt_of_essSup_lt
theorem ae_lt_of_lt_essInf (hx : x < essInf f μ)
(hf : IsBoundedUnder (· ≥ ·) (ae μ) f := by isBoundedDefault) :
∀ᵐ y ∂μ, x < f y :=
eventually_lt_of_lt_liminf hx hf
#align ae_lt_of_lt_ess_inf ae_lt_of_lt_essInf
variable [TopologicalSpace β] [FirstCountableTopology β] [OrderTopology β]
theorem ae_le_essSup
(hf : IsBoundedUnder (· ≤ ·) (ae μ) f := by isBoundedDefault) :
∀ᵐ y ∂μ, f y ≤ essSup f μ :=
eventually_le_limsup hf
#align ae_le_ess_sup ae_le_essSup
theorem ae_essInf_le
(hf : IsBoundedUnder (· ≥ ·) (ae μ) f := by isBoundedDefault) :
∀ᵐ y ∂μ, essInf f μ ≤ f y :=
eventually_liminf_le hf
#align ae_ess_inf_le ae_essInf_le
theorem meas_essSup_lt
(hf : IsBoundedUnder (· ≤ ·) (ae μ) f := by isBoundedDefault) :
μ { y | essSup f μ < f y } = 0 := by
simp_rw [← not_le]
exact ae_le_essSup hf
#align meas_ess_sup_lt meas_essSup_lt
theorem meas_lt_essInf
(hf : IsBoundedUnder (· ≥ ·) (ae μ) f := by isBoundedDefault) :
μ { y | f y < essInf f μ } = 0 := by
simp_rw [← not_le]
exact ae_essInf_le hf
#align meas_lt_ess_inf meas_lt_essInf
end ConditionallyCompleteLinearOrder
section CompleteLattice
variable [CompleteLattice β]
@[simp]
theorem essSup_measure_zero {m : MeasurableSpace α} {f : α → β} : essSup f (0 : Measure α) = ⊥ :=
le_bot_iff.mp (sInf_le (by simp [Set.mem_setOf_eq, EventuallyLE, ae_iff]))
#align ess_sup_measure_zero essSup_measure_zero
@[simp]
theorem essInf_measure_zero {_ : MeasurableSpace α} {f : α → β} : essInf f (0 : Measure α) = ⊤ :=
@essSup_measure_zero α βᵒᵈ _ _ _
#align ess_inf_measure_zero essInf_measure_zero
theorem essSup_mono_ae {f g : α → β} (hfg : f ≤ᵐ[μ] g) : essSup f μ ≤ essSup g μ :=
limsup_le_limsup hfg
#align ess_sup_mono_ae essSup_mono_ae
theorem essInf_mono_ae {f g : α → β} (hfg : f ≤ᵐ[μ] g) : essInf f μ ≤ essInf g μ :=
liminf_le_liminf hfg
#align ess_inf_mono_ae essInf_mono_ae
theorem essSup_le_of_ae_le {f : α → β} (c : β) (hf : f ≤ᵐ[μ] fun _ => c) : essSup f μ ≤ c :=
limsup_le_of_le (by isBoundedDefault) hf
#align ess_sup_le_of_ae_le essSup_le_of_ae_le
theorem le_essInf_of_ae_le {f : α → β} (c : β) (hf : (fun _ => c) ≤ᵐ[μ] f) : c ≤ essInf f μ :=
@essSup_le_of_ae_le α βᵒᵈ _ _ _ _ c hf
#align le_ess_inf_of_ae_le le_essInf_of_ae_le
theorem essSup_const_bot : essSup (fun _ : α => (⊥ : β)) μ = (⊥ : β) :=
limsup_const_bot
#align ess_sup_const_bot essSup_const_bot
theorem essInf_const_top : essInf (fun _ : α => (⊤ : β)) μ = (⊤ : β) :=
liminf_const_top
#align ess_inf_const_top essInf_const_top
theorem OrderIso.essSup_apply {m : MeasurableSpace α} {γ} [CompleteLattice γ] (f : α → β)
(μ : Measure α) (g : β ≃o γ) : g (essSup f μ) = essSup (fun x => g (f x)) μ := by
refine OrderIso.limsup_apply g ?_ ?_ ?_ ?_
all_goals isBoundedDefault
#align order_iso.ess_sup_apply OrderIso.essSup_apply
theorem OrderIso.essInf_apply {_ : MeasurableSpace α} {γ} [CompleteLattice γ] (f : α → β)
(μ : Measure α) (g : β ≃o γ) : g (essInf f μ) = essInf (fun x => g (f x)) μ :=
@OrderIso.essSup_apply α βᵒᵈ _ _ γᵒᵈ _ _ _ g.dual
#align order_iso.ess_inf_apply OrderIso.essInf_apply
theorem essSup_mono_measure {f : α → β} (hμν : ν ≪ μ) : essSup f ν ≤ essSup f μ := by
refine limsup_le_limsup_of_le (Measure.ae_le_iff_absolutelyContinuous.mpr hμν) ?_ ?_
all_goals isBoundedDefault
#align ess_sup_mono_measure essSup_mono_measure
theorem essSup_mono_measure' {α : Type*} {β : Type*} {_ : MeasurableSpace α}
{μ ν : MeasureTheory.Measure α} [CompleteLattice β] {f : α → β} (hμν : ν ≤ μ) :
essSup f ν ≤ essSup f μ :=
essSup_mono_measure (Measure.absolutelyContinuous_of_le hμν)
#align ess_sup_mono_measure' essSup_mono_measure'
theorem essInf_antitone_measure {f : α → β} (hμν : μ ≪ ν) : essInf f ν ≤ essInf f μ := by
refine liminf_le_liminf_of_le (Measure.ae_le_iff_absolutelyContinuous.mpr hμν) ?_ ?_
all_goals isBoundedDefault
#align ess_inf_antitone_measure essInf_antitone_measure
theorem essSup_smul_measure {f : α → β} {c : ℝ≥0∞} (hc : c ≠ 0) :
essSup f (c • μ) = essSup f μ := by
simp_rw [essSup]
suffices h_smul : ae (c • μ) = ae μ by rw [h_smul]
ext1
simp_rw [mem_ae_iff]
simp [hc]
#align ess_sup_smul_measure essSup_smul_measure
section TopologicalSpace
variable {γ : Type*} {mγ : MeasurableSpace γ} {f : α → γ} {g : γ → β}
theorem essSup_comp_le_essSup_map_measure (hf : AEMeasurable f μ) :
essSup (g ∘ f) μ ≤ essSup g (Measure.map f μ) := by
refine limsSup_le_limsSup_of_le ?_
rw [← Filter.map_map]
exact Filter.map_mono (Measure.tendsto_ae_map hf)
#align ess_sup_comp_le_ess_sup_map_measure essSup_comp_le_essSup_map_measure
theorem MeasurableEmbedding.essSup_map_measure (hf : MeasurableEmbedding f) :
essSup g (Measure.map f μ) = essSup (g ∘ f) μ := by
refine le_antisymm ?_ (essSup_comp_le_essSup_map_measure hf.measurable.aemeasurable)
refine limsSup_le_limsSup (by isBoundedDefault) (by isBoundedDefault) (fun c h_le => ?_)
rw [eventually_map] at h_le ⊢
exact hf.ae_map_iff.mpr h_le
#align measurable_embedding.ess_sup_map_measure MeasurableEmbedding.essSup_map_measure
variable [MeasurableSpace β] [TopologicalSpace β] [SecondCountableTopology β]
[OrderClosedTopology β] [OpensMeasurableSpace β]
theorem essSup_map_measure_of_measurable (hg : Measurable g) (hf : AEMeasurable f μ) :
essSup g (Measure.map f μ) = essSup (g ∘ f) μ := by
refine le_antisymm ?_ (essSup_comp_le_essSup_map_measure hf)
refine limsSup_le_limsSup (by isBoundedDefault) (by isBoundedDefault) (fun c h_le => ?_)
rw [eventually_map] at h_le ⊢
rw [ae_map_iff hf (measurableSet_le hg measurable_const)]
exact h_le
#align ess_sup_map_measure_of_measurable essSup_map_measure_of_measurable
theorem essSup_map_measure (hg : AEMeasurable g (Measure.map f μ)) (hf : AEMeasurable f μ) :
essSup g (Measure.map f μ) = essSup (g ∘ f) μ := by
rw [essSup_congr_ae hg.ae_eq_mk, essSup_map_measure_of_measurable hg.measurable_mk hf]
refine essSup_congr_ae ?_
have h_eq := ae_of_ae_map hf hg.ae_eq_mk
rw [← EventuallyEq] at h_eq
exact h_eq.symm
#align ess_sup_map_measure essSup_map_measure
end TopologicalSpace
end CompleteLattice
namespace ENNReal
variable {f : α → ℝ≥0∞}
lemma essSup_piecewise {s : Set α} [DecidablePred (· ∈ s)] {g} (hs : MeasurableSet s) :
essSup (s.piecewise f g) μ = max (essSup f (μ.restrict s)) (essSup g (μ.restrict sᶜ)) := by
simp only [essSup, limsup_piecewise, blimsup_eq_limsup, ae_restrict_eq, hs, hs.compl]; rfl
theorem essSup_indicator_eq_essSup_restrict {s : Set α} {f : α → ℝ≥0∞} (hs : MeasurableSet s) :
essSup (s.indicator f) μ = essSup f (μ.restrict s) := by
classical
simp only [← piecewise_eq_indicator, essSup_piecewise hs, max_eq_left_iff]
exact limsup_const_bot.trans_le (zero_le _)
theorem ae_le_essSup (f : α → ℝ≥0∞) : ∀ᵐ y ∂μ, f y ≤ essSup f μ :=
eventually_le_limsup f
#align ennreal.ae_le_ess_sup ENNReal.ae_le_essSup
@[simp]
theorem essSup_eq_zero_iff : essSup f μ = 0 ↔ f =ᵐ[μ] 0 :=
limsup_eq_zero_iff
#align ennreal.ess_sup_eq_zero_iff ENNReal.essSup_eq_zero_iff
theorem essSup_const_mul {a : ℝ≥0∞} : essSup (fun x : α => a * f x) μ = a * essSup f μ :=
limsup_const_mul
#align ennreal.ess_sup_const_mul ENNReal.essSup_const_mul
theorem essSup_mul_le (f g : α → ℝ≥0∞) : essSup (f * g) μ ≤ essSup f μ * essSup g μ :=
limsup_mul_le f g
#align ennreal.ess_sup_mul_le ENNReal.essSup_mul_le
theorem essSup_add_le (f g : α → ℝ≥0∞) : essSup (f + g) μ ≤ essSup f μ + essSup g μ :=
limsup_add_le f g
#align ennreal.ess_sup_add_le ENNReal.essSup_add_le
| Mathlib/MeasureTheory/Function/EssSup.lean | 293 | 297 | theorem essSup_liminf_le {ι} [Countable ι] [LinearOrder ι] (f : ι → α → ℝ≥0∞) :
essSup (fun x => atTop.liminf fun n => f n x) μ ≤
atTop.liminf fun n => essSup (fun x => f n x) μ := by |
simp_rw [essSup]
exact ENNReal.limsup_liminf_le_liminf_limsup fun a b => f b a
|
/-
Copyright (c) 2021 Adam Topaz. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Adam Topaz
-/
import Mathlib.CategoryTheory.Limits.Shapes.Products
import Mathlib.CategoryTheory.Limits.Shapes.Equalizers
import Mathlib.CategoryTheory.Limits.ConeCategory
#align_import category_theory.limits.shapes.multiequalizer from "leanprover-community/mathlib"@"70fd9563a21e7b963887c9360bd29b2393e6225a"
/-!
# Multi-(co)equalizers
A *multiequalizer* is an equalizer of two morphisms between two products.
Since both products and equalizers are limits, such an object is again a limit.
This file provides the diagram whose limit is indeed such an object.
In fact, it is well-known that any limit can be obtained as a multiequalizer.
The dual construction (multicoequalizers) is also provided.
## Projects
Prove that a multiequalizer can be identified with
an equalizer between products (and analogously for multicoequalizers).
Prove that the limit of any diagram is a multiequalizer (and similarly for colimits).
-/
namespace CategoryTheory.Limits
open CategoryTheory
universe w v u
/-- The type underlying the multiequalizer diagram. -/
--@[nolint unused_arguments]
inductive WalkingMulticospan {L R : Type w} (fst snd : R → L) : Type w
| left : L → WalkingMulticospan fst snd
| right : R → WalkingMulticospan fst snd
#align category_theory.limits.walking_multicospan CategoryTheory.Limits.WalkingMulticospan
/-- The type underlying the multiecoqualizer diagram. -/
--@[nolint unused_arguments]
inductive WalkingMultispan {L R : Type w} (fst snd : L → R) : Type w
| left : L → WalkingMultispan fst snd
| right : R → WalkingMultispan fst snd
#align category_theory.limits.walking_multispan CategoryTheory.Limits.WalkingMultispan
namespace WalkingMulticospan
variable {L R : Type w} {fst snd : R → L}
instance [Inhabited L] : Inhabited (WalkingMulticospan fst snd) :=
⟨left default⟩
/-- Morphisms for `WalkingMulticospan`. -/
inductive Hom : ∀ _ _ : WalkingMulticospan fst snd, Type w
| id (A) : Hom A A
| fst (b) : Hom (left (fst b)) (right b)
| snd (b) : Hom (left (snd b)) (right b)
#align category_theory.limits.walking_multicospan.hom CategoryTheory.Limits.WalkingMulticospan.Hom
/- Porting note: simpNF says the LHS of this internal identifier simplifies
(which it does, using Hom.id_eq_id) -/
attribute [-simp, nolint simpNF] WalkingMulticospan.Hom.id.sizeOf_spec
instance {a : WalkingMulticospan fst snd} : Inhabited (Hom a a) :=
⟨Hom.id _⟩
/-- Composition of morphisms for `WalkingMulticospan`. -/
def Hom.comp : ∀ {A B C : WalkingMulticospan fst snd} (_ : Hom A B) (_ : Hom B C), Hom A C
| _, _, _, Hom.id X, f => f
| _, _, _, Hom.fst b, Hom.id _ => Hom.fst b
| _, _, _, Hom.snd b, Hom.id _ => Hom.snd b
#align category_theory.limits.walking_multicospan.hom.comp CategoryTheory.Limits.WalkingMulticospan.Hom.comp
instance : SmallCategory (WalkingMulticospan fst snd) where
Hom := Hom
id := Hom.id
comp := Hom.comp
id_comp := by
rintro (_ | _) (_ | _) (_ | _ | _) <;> rfl
comp_id := by
rintro (_ | _) (_ | _) (_ | _ | _) <;> rfl
assoc := by
rintro (_ | _) (_ | _) (_ | _) (_ | _) (_ | _ | _) (_ | _ | _) (_ | _ | _) <;> rfl
@[simp] -- Porting note (#10756): added simp lemma
lemma Hom.id_eq_id (X : WalkingMulticospan fst snd) :
Hom.id X = 𝟙 X := rfl
@[simp] -- Porting note (#10756): added simp lemma
lemma Hom.comp_eq_comp {X Y Z : WalkingMulticospan fst snd}
(f : X ⟶ Y) (g : Y ⟶ Z) : Hom.comp f g = f ≫ g := rfl
end WalkingMulticospan
namespace WalkingMultispan
variable {L R : Type v} {fst snd : L → R}
instance [Inhabited L] : Inhabited (WalkingMultispan fst snd) :=
⟨left default⟩
/-- Morphisms for `WalkingMultispan`. -/
inductive Hom : ∀ _ _ : WalkingMultispan fst snd, Type v
| id (A) : Hom A A
| fst (a) : Hom (left a) (right (fst a))
| snd (a) : Hom (left a) (right (snd a))
#align category_theory.limits.walking_multispan.hom CategoryTheory.Limits.WalkingMultispan.Hom
/- Porting note: simpNF says the LHS of this internal identifier simplifies
(which it does, using Hom.id_eq_id) -/
attribute [-simp, nolint simpNF] WalkingMultispan.Hom.id.sizeOf_spec
instance {a : WalkingMultispan fst snd} : Inhabited (Hom a a) :=
⟨Hom.id _⟩
/-- Composition of morphisms for `WalkingMultispan`. -/
def Hom.comp : ∀ {A B C : WalkingMultispan fst snd} (_ : Hom A B) (_ : Hom B C), Hom A C
| _, _, _, Hom.id X, f => f
| _, _, _, Hom.fst a, Hom.id _ => Hom.fst a
| _, _, _, Hom.snd a, Hom.id _ => Hom.snd a
#align category_theory.limits.walking_multispan.hom.comp CategoryTheory.Limits.WalkingMultispan.Hom.comp
instance : SmallCategory (WalkingMultispan fst snd) where
Hom := Hom
id := Hom.id
comp := Hom.comp
id_comp := by
rintro (_ | _) (_ | _) (_ | _ | _) <;> rfl
comp_id := by
rintro (_ | _) (_ | _) (_ | _ | _) <;> rfl
assoc := by
rintro (_ | _) (_ | _) (_ | _) (_ | _) (_ | _ | _) (_ | _ | _) (_ | _ | _) <;> rfl
@[simp] -- Porting note (#10756): added simp lemma
lemma Hom.id_eq_id (X : WalkingMultispan fst snd) : Hom.id X = 𝟙 X := rfl
@[simp] -- Porting note (#10756): added simp lemma
lemma Hom.comp_eq_comp {X Y Z : WalkingMultispan fst snd}
(f : X ⟶ Y) (g : Y ⟶ Z) : Hom.comp f g = f ≫ g := rfl
end WalkingMultispan
/-- This is a structure encapsulating the data necessary to define a `Multicospan`. -/
-- Porting note(#5171): linter not ported yet
-- @[nolint has_nonempty_instance]
structure MulticospanIndex (C : Type u) [Category.{v} C] where
(L R : Type w)
(fstTo sndTo : R → L)
left : L → C
right : R → C
fst : ∀ b, left (fstTo b) ⟶ right b
snd : ∀ b, left (sndTo b) ⟶ right b
#align category_theory.limits.multicospan_index CategoryTheory.Limits.MulticospanIndex
/-- This is a structure encapsulating the data necessary to define a `Multispan`. -/
-- Porting note(#5171): linter not ported yet
-- @[nolint has_nonempty_instance]
structure MultispanIndex (C : Type u) [Category.{v} C] where
(L R : Type w)
(fstFrom sndFrom : L → R)
left : L → C
right : R → C
fst : ∀ a, left a ⟶ right (fstFrom a)
snd : ∀ a, left a ⟶ right (sndFrom a)
#align category_theory.limits.multispan_index CategoryTheory.Limits.MultispanIndex
namespace MulticospanIndex
variable {C : Type u} [Category.{v} C] (I : MulticospanIndex.{w} C)
/-- The multicospan associated to `I : MulticospanIndex`. -/
def multicospan : WalkingMulticospan I.fstTo I.sndTo ⥤ C where
obj x :=
match x with
| WalkingMulticospan.left a => I.left a
| WalkingMulticospan.right b => I.right b
map {x y} f :=
match x, y, f with
| _, _, WalkingMulticospan.Hom.id x => 𝟙 _
| _, _, WalkingMulticospan.Hom.fst b => I.fst _
| _, _, WalkingMulticospan.Hom.snd b => I.snd _
map_id := by
rintro (_ | _) <;> rfl
map_comp := by
rintro (_ | _) (_ | _) (_ | _) (_ | _ | _) (_ | _ | _) <;> aesop_cat
#align category_theory.limits.multicospan_index.multicospan CategoryTheory.Limits.MulticospanIndex.multicospan
@[simp]
theorem multicospan_obj_left (a) : I.multicospan.obj (WalkingMulticospan.left a) = I.left a :=
rfl
#align category_theory.limits.multicospan_index.multicospan_obj_left CategoryTheory.Limits.MulticospanIndex.multicospan_obj_left
@[simp]
theorem multicospan_obj_right (b) : I.multicospan.obj (WalkingMulticospan.right b) = I.right b :=
rfl
#align category_theory.limits.multicospan_index.multicospan_obj_right CategoryTheory.Limits.MulticospanIndex.multicospan_obj_right
@[simp]
theorem multicospan_map_fst (b) : I.multicospan.map (WalkingMulticospan.Hom.fst b) = I.fst b :=
rfl
#align category_theory.limits.multicospan_index.multicospan_map_fst CategoryTheory.Limits.MulticospanIndex.multicospan_map_fst
@[simp]
theorem multicospan_map_snd (b) : I.multicospan.map (WalkingMulticospan.Hom.snd b) = I.snd b :=
rfl
#align category_theory.limits.multicospan_index.multicospan_map_snd CategoryTheory.Limits.MulticospanIndex.multicospan_map_snd
variable [HasProduct I.left] [HasProduct I.right]
/-- The induced map `∏ᶜ I.left ⟶ ∏ᶜ I.right` via `I.fst`. -/
noncomputable def fstPiMap : ∏ᶜ I.left ⟶ ∏ᶜ I.right :=
Pi.lift fun b => Pi.π I.left (I.fstTo b) ≫ I.fst b
#align category_theory.limits.multicospan_index.fst_pi_map CategoryTheory.Limits.MulticospanIndex.fstPiMap
/-- The induced map `∏ᶜ I.left ⟶ ∏ᶜ I.right` via `I.snd`. -/
noncomputable def sndPiMap : ∏ᶜ I.left ⟶ ∏ᶜ I.right :=
Pi.lift fun b => Pi.π I.left (I.sndTo b) ≫ I.snd b
#align category_theory.limits.multicospan_index.snd_pi_map CategoryTheory.Limits.MulticospanIndex.sndPiMap
@[reassoc (attr := simp)]
theorem fstPiMap_π (b) : I.fstPiMap ≫ Pi.π I.right b = Pi.π I.left _ ≫ I.fst b := by
simp [fstPiMap]
#align category_theory.limits.multicospan_index.fst_pi_map_π CategoryTheory.Limits.MulticospanIndex.fstPiMap_π
@[reassoc (attr := simp)]
theorem sndPiMap_π (b) : I.sndPiMap ≫ Pi.π I.right b = Pi.π I.left _ ≫ I.snd b := by
simp [sndPiMap]
#align category_theory.limits.multicospan_index.snd_pi_map_π CategoryTheory.Limits.MulticospanIndex.sndPiMap_π
/-- Taking the multiequalizer over the multicospan index is equivalent to taking the equalizer over
the two morphisms `∏ᶜ I.left ⇉ ∏ᶜ I.right`. This is the diagram of the latter.
-/
@[simps!]
protected noncomputable def parallelPairDiagram :=
parallelPair I.fstPiMap I.sndPiMap
#align category_theory.limits.multicospan_index.parallel_pair_diagram CategoryTheory.Limits.MulticospanIndex.parallelPairDiagram
end MulticospanIndex
namespace MultispanIndex
variable {C : Type u} [Category.{v} C] (I : MultispanIndex.{w} C)
/-- The multispan associated to `I : MultispanIndex`. -/
def multispan : WalkingMultispan I.fstFrom I.sndFrom ⥤ C where
obj x :=
match x with
| WalkingMultispan.left a => I.left a
| WalkingMultispan.right b => I.right b
map {x y} f :=
match x, y, f with
| _, _, WalkingMultispan.Hom.id x => 𝟙 _
| _, _, WalkingMultispan.Hom.fst b => I.fst _
| _, _, WalkingMultispan.Hom.snd b => I.snd _
map_id := by
rintro (_ | _) <;> rfl
map_comp := by
rintro (_ | _) (_ | _) (_ | _) (_ | _ | _) (_ | _ | _) <;> aesop_cat
#align category_theory.limits.multispan_index.multispan CategoryTheory.Limits.MultispanIndex.multispan
@[simp]
theorem multispan_obj_left (a) : I.multispan.obj (WalkingMultispan.left a) = I.left a :=
rfl
#align category_theory.limits.multispan_index.multispan_obj_left CategoryTheory.Limits.MultispanIndex.multispan_obj_left
@[simp]
theorem multispan_obj_right (b) : I.multispan.obj (WalkingMultispan.right b) = I.right b :=
rfl
#align category_theory.limits.multispan_index.multispan_obj_right CategoryTheory.Limits.MultispanIndex.multispan_obj_right
@[simp]
theorem multispan_map_fst (a) : I.multispan.map (WalkingMultispan.Hom.fst a) = I.fst a :=
rfl
#align category_theory.limits.multispan_index.multispan_map_fst CategoryTheory.Limits.MultispanIndex.multispan_map_fst
@[simp]
theorem multispan_map_snd (a) : I.multispan.map (WalkingMultispan.Hom.snd a) = I.snd a :=
rfl
#align category_theory.limits.multispan_index.multispan_map_snd CategoryTheory.Limits.MultispanIndex.multispan_map_snd
variable [HasCoproduct I.left] [HasCoproduct I.right]
/-- The induced map `∐ I.left ⟶ ∐ I.right` via `I.fst`. -/
noncomputable def fstSigmaMap : ∐ I.left ⟶ ∐ I.right :=
Sigma.desc fun b => I.fst b ≫ Sigma.ι _ (I.fstFrom b)
#align category_theory.limits.multispan_index.fst_sigma_map CategoryTheory.Limits.MultispanIndex.fstSigmaMap
/-- The induced map `∐ I.left ⟶ ∐ I.right` via `I.snd`. -/
noncomputable def sndSigmaMap : ∐ I.left ⟶ ∐ I.right :=
Sigma.desc fun b => I.snd b ≫ Sigma.ι _ (I.sndFrom b)
#align category_theory.limits.multispan_index.snd_sigma_map CategoryTheory.Limits.MultispanIndex.sndSigmaMap
@[reassoc (attr := simp)]
theorem ι_fstSigmaMap (b) : Sigma.ι I.left b ≫ I.fstSigmaMap = I.fst b ≫ Sigma.ι I.right _ := by
simp [fstSigmaMap]
#align category_theory.limits.multispan_index.ι_fst_sigma_map CategoryTheory.Limits.MultispanIndex.ι_fstSigmaMap
@[reassoc (attr := simp)]
theorem ι_sndSigmaMap (b) : Sigma.ι I.left b ≫ I.sndSigmaMap = I.snd b ≫ Sigma.ι I.right _ := by
simp [sndSigmaMap]
#align category_theory.limits.multispan_index.ι_snd_sigma_map CategoryTheory.Limits.MultispanIndex.ι_sndSigmaMap
/--
Taking the multicoequalizer over the multispan index is equivalent to taking the coequalizer over
the two morphsims `∐ I.left ⇉ ∐ I.right`. This is the diagram of the latter.
-/
protected noncomputable abbrev parallelPairDiagram :=
parallelPair I.fstSigmaMap I.sndSigmaMap
#align category_theory.limits.multispan_index.parallel_pair_diagram CategoryTheory.Limits.MultispanIndex.parallelPairDiagram
end MultispanIndex
variable {C : Type u} [Category.{v} C]
/-- A multifork is a cone over a multicospan. -/
-- Porting note(#5171): linter not ported yet
-- @[nolint has_nonempty_instance]
abbrev Multifork (I : MulticospanIndex.{w} C) :=
Cone I.multicospan
#align category_theory.limits.multifork CategoryTheory.Limits.Multifork
/-- A multicofork is a cocone over a multispan. -/
-- Porting note(#5171): linter not ported yet
-- @[nolint has_nonempty_instance]
abbrev Multicofork (I : MultispanIndex.{w} C) :=
Cocone I.multispan
#align category_theory.limits.multicofork CategoryTheory.Limits.Multicofork
namespace Multifork
variable {I : MulticospanIndex.{w} C} (K : Multifork I)
/-- The maps from the cone point of a multifork to the objects on the left. -/
def ι (a : I.L) : K.pt ⟶ I.left a :=
K.π.app (WalkingMulticospan.left _)
#align category_theory.limits.multifork.ι CategoryTheory.Limits.Multifork.ι
@[simp]
theorem app_left_eq_ι (a) : K.π.app (WalkingMulticospan.left a) = K.ι a :=
rfl
#align category_theory.limits.multifork.app_left_eq_ι CategoryTheory.Limits.Multifork.app_left_eq_ι
@[simp]
theorem app_right_eq_ι_comp_fst (b) :
K.π.app (WalkingMulticospan.right b) = K.ι (I.fstTo b) ≫ I.fst b := by
rw [← K.w (WalkingMulticospan.Hom.fst b)]
rfl
#align category_theory.limits.multifork.app_right_eq_ι_comp_fst CategoryTheory.Limits.Multifork.app_right_eq_ι_comp_fst
@[reassoc]
theorem app_right_eq_ι_comp_snd (b) :
K.π.app (WalkingMulticospan.right b) = K.ι (I.sndTo b) ≫ I.snd b := by
rw [← K.w (WalkingMulticospan.Hom.snd b)]
rfl
#align category_theory.limits.multifork.app_right_eq_ι_comp_snd CategoryTheory.Limits.Multifork.app_right_eq_ι_comp_snd
@[reassoc (attr := simp)]
theorem hom_comp_ι (K₁ K₂ : Multifork I) (f : K₁ ⟶ K₂) (j : I.L) : f.hom ≫ K₂.ι j = K₁.ι j :=
f.w _
#align category_theory.limits.multifork.hom_comp_ι CategoryTheory.Limits.Multifork.hom_comp_ι
/-- Construct a multifork using a collection `ι` of morphisms. -/
@[simps]
def ofι (I : MulticospanIndex.{w} C) (P : C) (ι : ∀ a, P ⟶ I.left a)
(w : ∀ b, ι (I.fstTo b) ≫ I.fst b = ι (I.sndTo b) ≫ I.snd b) : Multifork I where
pt := P
π :=
{ app := fun x =>
match x with
| WalkingMulticospan.left a => ι _
| WalkingMulticospan.right b => ι (I.fstTo b) ≫ I.fst b
naturality := by
rintro (_ | _) (_ | _) (_ | _ | _) <;>
dsimp <;>
simp only [Category.id_comp, Category.comp_id, Functor.map_id,
MulticospanIndex.multicospan_obj_left, MulticospanIndex.multicospan_obj_right]
apply w }
#align category_theory.limits.multifork.of_ι CategoryTheory.Limits.Multifork.ofι
@[reassoc (attr := simp)]
theorem condition (b) : K.ι (I.fstTo b) ≫ I.fst b = K.ι (I.sndTo b) ≫ I.snd b := by
rw [← app_right_eq_ι_comp_fst, ← app_right_eq_ι_comp_snd]
#align category_theory.limits.multifork.condition CategoryTheory.Limits.Multifork.condition
/-- This definition provides a convenient way to show that a multifork is a limit. -/
@[simps]
def IsLimit.mk (lift : ∀ E : Multifork I, E.pt ⟶ K.pt)
(fac : ∀ (E : Multifork I) (i : I.L), lift E ≫ K.ι i = E.ι i)
(uniq : ∀ (E : Multifork I) (m : E.pt ⟶ K.pt), (∀ i : I.L, m ≫ K.ι i = E.ι i) → m = lift E) :
IsLimit K :=
{ lift
fac := by
rintro E (a | b)
· apply fac
· rw [← E.w (WalkingMulticospan.Hom.fst b), ← K.w (WalkingMulticospan.Hom.fst b), ←
Category.assoc]
congr 1
apply fac
uniq := by
rintro E m hm
apply uniq
intro i
apply hm }
#align category_theory.limits.multifork.is_limit.mk CategoryTheory.Limits.Multifork.IsLimit.mk
variable {K}
lemma IsLimit.hom_ext (hK : IsLimit K) {T : C} {f g : T ⟶ K.pt}
(h : ∀ a, f ≫ K.ι a = g ≫ K.ι a) : f = g := by
apply hK.hom_ext
rintro (_|b)
· apply h
· dsimp
rw [app_right_eq_ι_comp_fst, reassoc_of% h]
/-- Constructor for morphisms to the point of a limit multifork. -/
def IsLimit.lift (hK : IsLimit K) {T : C} (k : ∀ a, T ⟶ I.left a)
(hk : ∀ b, k (I.fstTo b) ≫ I.fst b = k (I.sndTo b) ≫ I.snd b) :
T ⟶ K.pt :=
hK.lift (Multifork.ofι _ _ k hk)
@[reassoc (attr := simp)]
lemma IsLimit.fac (hK : IsLimit K) {T : C} (k : ∀ a, T ⟶ I.left a)
(hk : ∀ b, k (I.fstTo b) ≫ I.fst b = k (I.sndTo b) ≫ I.snd b) (a : I.L):
IsLimit.lift hK k hk ≫ K.ι a = k a :=
hK.fac _ _
variable (K)
variable [HasProduct I.left] [HasProduct I.right]
@[reassoc (attr := simp)]
theorem pi_condition : Pi.lift K.ι ≫ I.fstPiMap = Pi.lift K.ι ≫ I.sndPiMap := by
ext
simp
#align category_theory.limits.multifork.pi_condition CategoryTheory.Limits.Multifork.pi_condition
/-- Given a multifork, we may obtain a fork over `∏ᶜ I.left ⇉ ∏ᶜ I.right`. -/
@[simps pt]
noncomputable def toPiFork (K : Multifork I) : Fork I.fstPiMap I.sndPiMap where
pt := K.pt
π :=
{ app := fun x =>
match x with
| WalkingParallelPair.zero => Pi.lift K.ι
| WalkingParallelPair.one => Pi.lift K.ι ≫ I.fstPiMap
naturality := by
rintro (_ | _) (_ | _) (_ | _ | _) <;>
dsimp <;>
simp only [Category.id_comp, Functor.map_id, parallelPair_obj_zero, Category.comp_id,
pi_condition, parallelPair_obj_one] }
#align category_theory.limits.multifork.to_pi_fork CategoryTheory.Limits.Multifork.toPiFork
@[simp]
theorem toPiFork_π_app_zero : K.toPiFork.ι = Pi.lift K.ι :=
rfl
#align category_theory.limits.multifork.to_pi_fork_π_app_zero CategoryTheory.Limits.Multifork.toPiFork_π_app_zero
@[simp, nolint simpNF] -- Porting note (#10675): dsimp cannot prove this
theorem toPiFork_π_app_one : K.toPiFork.π.app WalkingParallelPair.one = Pi.lift K.ι ≫ I.fstPiMap :=
rfl
#align category_theory.limits.multifork.to_pi_fork_π_app_one CategoryTheory.Limits.Multifork.toPiFork_π_app_one
variable (I)
/-- Given a fork over `∏ᶜ I.left ⇉ ∏ᶜ I.right`, we may obtain a multifork. -/
@[simps pt]
noncomputable def ofPiFork (c : Fork I.fstPiMap I.sndPiMap) : Multifork I where
pt := c.pt
π :=
{ app := fun x =>
match x with
| WalkingMulticospan.left a => c.ι ≫ Pi.π _ _
| WalkingMulticospan.right b => c.ι ≫ I.fstPiMap ≫ Pi.π _ _
naturality := by
rintro (_ | _) (_ | _) (_ | _ | _)
· simp
· simp
· dsimp; rw [c.condition_assoc]; simp
· simp }
#align category_theory.limits.multifork.of_pi_fork CategoryTheory.Limits.Multifork.ofPiFork
@[simp]
theorem ofPiFork_π_app_left (c : Fork I.fstPiMap I.sndPiMap) (a) :
(ofPiFork I c).ι a = c.ι ≫ Pi.π _ _ :=
rfl
#align category_theory.limits.multifork.of_pi_fork_π_app_left CategoryTheory.Limits.Multifork.ofPiFork_π_app_left
@[simp, nolint simpNF] -- Porting note (#10675): dsimp cannot prove this
theorem ofPiFork_π_app_right (c : Fork I.fstPiMap I.sndPiMap) (a) :
(ofPiFork I c).π.app (WalkingMulticospan.right a) = c.ι ≫ I.fstPiMap ≫ Pi.π _ _ :=
rfl
#align category_theory.limits.multifork.of_pi_fork_π_app_right CategoryTheory.Limits.Multifork.ofPiFork_π_app_right
end Multifork
namespace MulticospanIndex
variable (I : MulticospanIndex.{w} C) [HasProduct I.left] [HasProduct I.right]
--attribute [local tidy] tactic.case_bash
/-- `Multifork.toPiFork` as a functor. -/
@[simps]
noncomputable def toPiForkFunctor : Multifork I ⥤ Fork I.fstPiMap I.sndPiMap where
obj := Multifork.toPiFork
map {K₁ K₂} f :=
{ hom := f.hom
w := by
rintro (_ | _)
· apply limit.hom_ext
simp
· apply limit.hom_ext
intros j
simp only [Multifork.toPiFork_π_app_one, Multifork.pi_condition, Category.assoc]
dsimp [sndPiMap]
simp }
#align category_theory.limits.multicospan_index.to_pi_fork_functor CategoryTheory.Limits.MulticospanIndex.toPiForkFunctor
/-- `Multifork.ofPiFork` as a functor. -/
@[simps]
noncomputable def ofPiForkFunctor : Fork I.fstPiMap I.sndPiMap ⥤ Multifork I where
obj := Multifork.ofPiFork I
map {K₁ K₂} f :=
{ hom := f.hom
w := by rintro (_ | _) <;> simp }
#align category_theory.limits.multicospan_index.of_pi_fork_functor CategoryTheory.Limits.MulticospanIndex.ofPiForkFunctor
/-- The category of multiforks is equivalent to the category of forks over `∏ᶜ I.left ⇉ ∏ᶜ I.right`.
It then follows from `CategoryTheory.IsLimit.ofPreservesConeTerminal` (or `reflects`) that it
preserves and reflects limit cones.
-/
@[simps]
noncomputable def multiforkEquivPiFork : Multifork I ≌ Fork I.fstPiMap I.sndPiMap where
functor := toPiForkFunctor I
inverse := ofPiForkFunctor I
unitIso :=
NatIso.ofComponents fun K =>
Cones.ext (Iso.refl _) (by
rintro (_ | _) <;> simp [← Fork.app_one_eq_ι_comp_left])
counitIso :=
NatIso.ofComponents fun K => Fork.ext (Iso.refl _)
#align category_theory.limits.multicospan_index.multifork_equiv_pi_fork CategoryTheory.Limits.MulticospanIndex.multiforkEquivPiFork
end MulticospanIndex
namespace Multicofork
variable {I : MultispanIndex.{w} C} (K : Multicofork I)
/-- The maps to the cocone point of a multicofork from the objects on the right. -/
def π (b : I.R) : I.right b ⟶ K.pt :=
K.ι.app (WalkingMultispan.right _)
#align category_theory.limits.multicofork.π CategoryTheory.Limits.Multicofork.π
@[simp]
theorem π_eq_app_right (b) : K.ι.app (WalkingMultispan.right _) = K.π b :=
rfl
#align category_theory.limits.multicofork.π_eq_app_right CategoryTheory.Limits.Multicofork.π_eq_app_right
@[simp]
| Mathlib/CategoryTheory/Limits/Shapes/Multiequalizer.lean | 568 | 570 | theorem fst_app_right (a) : K.ι.app (WalkingMultispan.left a) = I.fst a ≫ K.π _ := by |
rw [← K.w (WalkingMultispan.Hom.fst a)]
rfl
|
/-
Copyright (c) 2022 Anatole Dedecker. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Sébastien Gouëzel, Anatole Dedecker
-/
import Mathlib.Analysis.LocallyConvex.BalancedCoreHull
import Mathlib.LinearAlgebra.FreeModule.Finite.Matrix
import Mathlib.Topology.Algebra.Module.Simple
import Mathlib.Topology.Algebra.Module.Determinant
import Mathlib.RingTheory.Ideal.LocalRing
#align_import topology.algebra.module.finite_dimension from "leanprover-community/mathlib"@"9425b6f8220e53b059f5a4904786c3c4b50fc057"
/-!
# Finite dimensional topological vector spaces over complete fields
Let `𝕜` be a complete nontrivially normed field, and `E` a topological vector space (TVS) over
`𝕜` (i.e we have `[AddCommGroup E] [Module 𝕜 E] [TopologicalSpace E] [TopologicalAddGroup E]`
and `[ContinuousSMul 𝕜 E]`).
If `E` is finite dimensional and Hausdorff, then all linear maps from `E` to any other TVS are
continuous.
When `E` is a normed space, this gets us the equivalence of norms in finite dimension.
## Main results :
* `LinearMap.continuous_iff_isClosed_ker` : a linear form is continuous if and only if its kernel
is closed.
* `LinearMap.continuous_of_finiteDimensional` : a linear map on a finite-dimensional Hausdorff
space over a complete field is continuous.
## TODO
Generalize more of `Mathlib.Analysis.NormedSpace.FiniteDimension` to general TVSs.
## Implementation detail
The main result from which everything follows is the fact that, if `ξ : ι → E` is a finite basis,
then `ξ.equivFun : E →ₗ (ι → 𝕜)` is continuous. However, for technical reasons, it is easier to
prove this when `ι` and `E` live in the same universe. So we start by doing that as a private
lemma, then we deduce `LinearMap.continuous_of_finiteDimensional` from it, and then the general
result follows as `continuous_equivFun_basis`.
-/
universe u v w x
noncomputable section
open Set FiniteDimensional TopologicalSpace Filter
section Field
variable {𝕜 E F : Type*} [Field 𝕜] [TopologicalSpace 𝕜] [AddCommGroup E] [Module 𝕜 E]
[TopologicalSpace E] [AddCommGroup F] [Module 𝕜 F] [TopologicalSpace F] [TopologicalAddGroup F]
[ContinuousSMul 𝕜 F]
/-- The space of continuous linear maps between finite-dimensional spaces is finite-dimensional. -/
instance [FiniteDimensional 𝕜 E] [FiniteDimensional 𝕜 F] : FiniteDimensional 𝕜 (E →L[𝕜] F) :=
FiniteDimensional.of_injective (ContinuousLinearMap.coeLM 𝕜 : (E →L[𝕜] F) →ₗ[𝕜] E →ₗ[𝕜] F)
ContinuousLinearMap.coe_injective
end Field
section NormedField
variable {𝕜 : Type u} [hnorm : NontriviallyNormedField 𝕜] {E : Type v} [AddCommGroup E] [Module 𝕜 E]
[TopologicalSpace E] [TopologicalAddGroup E] [ContinuousSMul 𝕜 E] {F : Type w} [AddCommGroup F]
[Module 𝕜 F] [TopologicalSpace F] [TopologicalAddGroup F] [ContinuousSMul 𝕜 F] {F' : Type x}
[AddCommGroup F'] [Module 𝕜 F'] [TopologicalSpace F'] [TopologicalAddGroup F']
[ContinuousSMul 𝕜 F']
/-- If `𝕜` is a nontrivially normed field, any T2 topology on `𝕜` which makes it a topological
vector space over itself (with the norm topology) is *equal* to the norm topology. -/
theorem unique_topology_of_t2 {t : TopologicalSpace 𝕜} (h₁ : @TopologicalAddGroup 𝕜 t _)
(h₂ : @ContinuousSMul 𝕜 𝕜 _ hnorm.toUniformSpace.toTopologicalSpace t) (h₃ : @T2Space 𝕜 t) :
t = hnorm.toUniformSpace.toTopologicalSpace := by
-- Let `𝓣₀` denote the topology on `𝕜` induced by the norm, and `𝓣` be any T2 vector
-- topology on `𝕜`. To show that `𝓣₀ = 𝓣`, it suffices to show that they have the same
-- neighborhoods of 0.
refine TopologicalAddGroup.ext h₁ inferInstance (le_antisymm ?_ ?_)
· -- To show `𝓣 ≤ 𝓣₀`, we have to show that closed balls are `𝓣`-neighborhoods of 0.
rw [Metric.nhds_basis_closedBall.ge_iff]
-- Let `ε > 0`. Since `𝕜` is nontrivially normed, we have `0 < ‖ξ₀‖ < ε` for some `ξ₀ : 𝕜`.
intro ε hε
rcases NormedField.exists_norm_lt 𝕜 hε with ⟨ξ₀, hξ₀, hξ₀ε⟩
-- Since `ξ₀ ≠ 0` and `𝓣` is T2, we know that `{ξ₀}ᶜ` is a `𝓣`-neighborhood of 0.
-- Porting note: added `mem_compl_singleton_iff.mpr`
have : {ξ₀}ᶜ ∈ @nhds 𝕜 t 0 := IsOpen.mem_nhds isOpen_compl_singleton <|
mem_compl_singleton_iff.mpr <| Ne.symm <| norm_ne_zero_iff.mp hξ₀.ne.symm
-- Thus, its balanced core `𝓑` is too. Let's show that the closed ball of radius `ε` contains
-- `𝓑`, which will imply that the closed ball is indeed a `𝓣`-neighborhood of 0.
have : balancedCore 𝕜 {ξ₀}ᶜ ∈ @nhds 𝕜 t 0 := balancedCore_mem_nhds_zero this
refine mem_of_superset this fun ξ hξ => ?_
-- Let `ξ ∈ 𝓑`. We want to show `‖ξ‖ < ε`. If `ξ = 0`, this is trivial.
by_cases hξ0 : ξ = 0
· rw [hξ0]
exact Metric.mem_closedBall_self hε.le
· rw [mem_closedBall_zero_iff]
-- Now suppose `ξ ≠ 0`. By contradiction, let's assume `ε < ‖ξ‖`, and show that
-- `ξ₀ ∈ 𝓑 ⊆ {ξ₀}ᶜ`, which is a contradiction.
by_contra! h
suffices (ξ₀ * ξ⁻¹) • ξ ∈ balancedCore 𝕜 {ξ₀}ᶜ by
rw [smul_eq_mul 𝕜, mul_assoc, inv_mul_cancel hξ0, mul_one] at this
exact not_mem_compl_iff.mpr (mem_singleton ξ₀) ((balancedCore_subset _) this)
-- For that, we use that `𝓑` is balanced : since `‖ξ₀‖ < ε < ‖ξ‖`, we have `‖ξ₀ / ξ‖ ≤ 1`,
-- hence `ξ₀ = (ξ₀ / ξ) • ξ ∈ 𝓑` because `ξ ∈ 𝓑`.
refine (balancedCore_balanced _).smul_mem ?_ hξ
rw [norm_mul, norm_inv, mul_inv_le_iff (norm_pos_iff.mpr hξ0), mul_one]
exact (hξ₀ε.trans h).le
· -- Finally, to show `𝓣₀ ≤ 𝓣`, we simply argue that `id = (fun x ↦ x • 1)` is continuous from
-- `(𝕜, 𝓣₀)` to `(𝕜, 𝓣)` because `(•) : (𝕜, 𝓣₀) × (𝕜, 𝓣) → (𝕜, 𝓣)` is continuous.
calc
@nhds 𝕜 hnorm.toUniformSpace.toTopologicalSpace 0 =
map id (@nhds 𝕜 hnorm.toUniformSpace.toTopologicalSpace 0) :=
map_id.symm
_ = map (fun x => id x • (1 : 𝕜)) (@nhds 𝕜 hnorm.toUniformSpace.toTopologicalSpace 0) := by
conv_rhs =>
congr
ext
rw [smul_eq_mul, mul_one]
_ ≤ @nhds 𝕜 t ((0 : 𝕜) • (1 : 𝕜)) :=
(@Tendsto.smul_const _ _ _ hnorm.toUniformSpace.toTopologicalSpace t _ _ _ _ _
tendsto_id (1 : 𝕜))
_ = @nhds 𝕜 t 0 := by rw [zero_smul]
#align unique_topology_of_t2 unique_topology_of_t2
/-- Any linear form on a topological vector space over a nontrivially normed field is continuous if
its kernel is closed. -/
theorem LinearMap.continuous_of_isClosed_ker (l : E →ₗ[𝕜] 𝕜)
(hl : IsClosed (LinearMap.ker l : Set E)) :
Continuous l := by
-- `l` is either constant or surjective. If it is constant, the result is trivial.
by_cases H : finrank 𝕜 (LinearMap.range l) = 0
· rw [Submodule.finrank_eq_zero, LinearMap.range_eq_bot] at H
rw [H]
exact continuous_zero
· -- In the case where `l` is surjective, we factor it as `φ : (E ⧸ l.ker) ≃ₗ[𝕜] 𝕜`. Note that
-- `E ⧸ l.ker` is T2 since `l.ker` is closed.
have : finrank 𝕜 (LinearMap.range l) = 1 :=
le_antisymm (finrank_self 𝕜 ▸ l.range.finrank_le) (zero_lt_iff.mpr H)
have hi : Function.Injective ((LinearMap.ker l).liftQ l (le_refl _)) := by
rw [← LinearMap.ker_eq_bot]
exact Submodule.ker_liftQ_eq_bot _ _ _ (le_refl _)
have hs : Function.Surjective ((LinearMap.ker l).liftQ l (le_refl _)) := by
rw [← LinearMap.range_eq_top, Submodule.range_liftQ]
exact Submodule.eq_top_of_finrank_eq ((finrank_self 𝕜).symm ▸ this)
let φ : (E ⧸ LinearMap.ker l) ≃ₗ[𝕜] 𝕜 :=
LinearEquiv.ofBijective ((LinearMap.ker l).liftQ l (le_refl _)) ⟨hi, hs⟩
have hlφ : (l : E → 𝕜) = φ ∘ (LinearMap.ker l).mkQ := by ext; rfl
-- Since the quotient map `E →ₗ[𝕜] (E ⧸ l.ker)` is continuous, the continuity of `l` will follow
-- form the continuity of `φ`.
suffices Continuous φ.toEquiv by
rw [hlφ]
exact this.comp continuous_quot_mk
-- The pullback by `φ.symm` of the quotient topology is a T2 topology on `𝕜`, because `φ.symm`
-- is injective. Since `φ.symm` is linear, it is also a vector space topology.
-- Hence, we know that it is equal to the topology induced by the norm.
have : induced φ.toEquiv.symm inferInstance = hnorm.toUniformSpace.toTopologicalSpace := by
refine unique_topology_of_t2 (topologicalAddGroup_induced φ.symm.toLinearMap)
(continuousSMul_induced φ.symm.toLinearMap) ?_
-- Porting note: was `rw [t2Space_iff]`
refine (@t2Space_iff 𝕜 (induced (↑(LinearEquiv.toEquiv φ).symm) inferInstance)).mpr ?_
exact fun x y hxy =>
@separated_by_continuous _ _ (induced _ _) _ _ _ continuous_induced_dom _ _
(φ.toEquiv.symm.injective.ne hxy)
-- Finally, the pullback by `φ.symm` is exactly the pushforward by `φ`, so we have to prove
-- that `φ` is continuous when `𝕜` is endowed with the pushforward by `φ` of the quotient
-- topology, which is trivial by definition of the pushforward.
rw [this.symm, Equiv.induced_symm]
exact continuous_coinduced_rng
#align linear_map.continuous_of_is_closed_ker LinearMap.continuous_of_isClosed_ker
/-- Any linear form on a topological vector space over a nontrivially normed field is continuous if
and only if its kernel is closed. -/
theorem LinearMap.continuous_iff_isClosed_ker (l : E →ₗ[𝕜] 𝕜) :
Continuous l ↔ IsClosed (LinearMap.ker l : Set E) :=
⟨fun h => isClosed_singleton.preimage h, l.continuous_of_isClosed_ker⟩
#align linear_map.continuous_iff_is_closed_ker LinearMap.continuous_iff_isClosed_ker
/-- Over a nontrivially normed field, any linear form which is nonzero on a nonempty open set is
automatically continuous. -/
theorem LinearMap.continuous_of_nonzero_on_open (l : E →ₗ[𝕜] 𝕜) (s : Set E) (hs₁ : IsOpen s)
(hs₂ : s.Nonempty) (hs₃ : ∀ x ∈ s, l x ≠ 0) : Continuous l := by
refine l.continuous_of_isClosed_ker (l.isClosed_or_dense_ker.resolve_right fun hl => ?_)
rcases hs₂ with ⟨x, hx⟩
have : x ∈ interior (LinearMap.ker l : Set E)ᶜ := by
rw [mem_interior_iff_mem_nhds]
exact mem_of_superset (hs₁.mem_nhds hx) hs₃
rwa [hl.interior_compl] at this
#align linear_map.continuous_of_nonzero_on_open LinearMap.continuous_of_nonzero_on_open
variable [CompleteSpace 𝕜]
/-- This version imposes `ι` and `E` to live in the same universe, so you should instead use
`continuous_equivFun_basis` which gives the same result without universe restrictions. -/
private theorem continuous_equivFun_basis_aux [T2Space E] {ι : Type v} [Fintype ι]
(ξ : Basis ι 𝕜 E) : Continuous ξ.equivFun := by
letI : UniformSpace E := TopologicalAddGroup.toUniformSpace E
letI : UniformAddGroup E := comm_topologicalAddGroup_is_uniform
induction' hn : Fintype.card ι with n IH generalizing ι E
· rw [Fintype.card_eq_zero_iff] at hn
exact continuous_of_const fun x y => funext hn.elim
· haveI : FiniteDimensional 𝕜 E := of_fintype_basis ξ
-- first step: thanks to the induction hypothesis, any n-dimensional subspace is equivalent
-- to a standard space of dimension n, hence it is complete and therefore closed.
have H₁ : ∀ s : Submodule 𝕜 E, finrank 𝕜 s = n → IsClosed (s : Set E) := by
intro s s_dim
letI : UniformAddGroup s := s.toAddSubgroup.uniformAddGroup
let b := Basis.ofVectorSpace 𝕜 s
have U : UniformEmbedding b.equivFun.symm.toEquiv := by
have : Fintype.card (Basis.ofVectorSpaceIndex 𝕜 s) = n := by
rw [← s_dim]
exact (finrank_eq_card_basis b).symm
have : Continuous b.equivFun := IH b this
exact
b.equivFun.symm.uniformEmbedding b.equivFun.symm.toLinearMap.continuous_on_pi this
have : IsComplete (s : Set E) :=
completeSpace_coe_iff_isComplete.1 ((completeSpace_congr U).1 (by infer_instance))
exact this.isClosed
-- second step: any linear form is continuous, as its kernel is closed by the first step
have H₂ : ∀ f : E →ₗ[𝕜] 𝕜, Continuous f := by
intro f
by_cases H : finrank 𝕜 (LinearMap.range f) = 0
· rw [Submodule.finrank_eq_zero, LinearMap.range_eq_bot] at H
rw [H]
exact continuous_zero
· have : finrank 𝕜 (LinearMap.ker f) = n := by
have Z := f.finrank_range_add_finrank_ker
rw [finrank_eq_card_basis ξ, hn] at Z
have : finrank 𝕜 (LinearMap.range f) = 1 :=
le_antisymm (finrank_self 𝕜 ▸ f.range.finrank_le) (zero_lt_iff.mpr H)
rw [this, add_comm, Nat.add_one] at Z
exact Nat.succ.inj Z
have : IsClosed (LinearMap.ker f : Set E) := H₁ _ this
exact LinearMap.continuous_of_isClosed_ker f this
rw [continuous_pi_iff]
intro i
change Continuous (ξ.coord i)
exact H₂ (ξ.coord i)
/-- Any linear map on a finite dimensional space over a complete field is continuous. -/
theorem LinearMap.continuous_of_finiteDimensional [T2Space E] [FiniteDimensional 𝕜 E]
(f : E →ₗ[𝕜] F') : Continuous f := by
-- for the proof, go to a model vector space `b → 𝕜` thanks to `continuous_equivFun_basis`, and
-- argue that all linear maps there are continuous.
let b := Basis.ofVectorSpace 𝕜 E
have A : Continuous b.equivFun := continuous_equivFun_basis_aux b
have B : Continuous (f.comp (b.equivFun.symm : (Basis.ofVectorSpaceIndex 𝕜 E → 𝕜) →ₗ[𝕜] E)) :=
LinearMap.continuous_on_pi _
have :
Continuous
(f.comp (b.equivFun.symm : (Basis.ofVectorSpaceIndex 𝕜 E → 𝕜) →ₗ[𝕜] E) ∘ b.equivFun) :=
B.comp A
convert this
ext x
dsimp
rw [Basis.equivFun_symm_apply, Basis.sum_repr]
#align linear_map.continuous_of_finite_dimensional LinearMap.continuous_of_finiteDimensional
instance LinearMap.continuousLinearMapClassOfFiniteDimensional [T2Space E] [FiniteDimensional 𝕜 E] :
ContinuousLinearMapClass (E →ₗ[𝕜] F') 𝕜 E F' :=
{ LinearMap.semilinearMapClass with map_continuous := fun f => f.continuous_of_finiteDimensional }
#align linear_map.continuous_linear_map_class_of_finite_dimensional LinearMap.continuousLinearMapClassOfFiniteDimensional
/-- In finite dimensions over a non-discrete complete normed field, the canonical identification
(in terms of a basis) with `𝕜^n` (endowed with the product topology) is continuous.
This is the key fact which makes all linear maps from a T2 finite dimensional TVS over such a field
continuous (see `LinearMap.continuous_of_finiteDimensional`), which in turn implies that all
norms are equivalent in finite dimensions. -/
theorem continuous_equivFun_basis [T2Space E] {ι : Type*} [Finite ι] (ξ : Basis ι 𝕜 E) :
Continuous ξ.equivFun :=
haveI : FiniteDimensional 𝕜 E := of_fintype_basis ξ
ξ.equivFun.toLinearMap.continuous_of_finiteDimensional
#align continuous_equiv_fun_basis continuous_equivFun_basis
namespace LinearMap
variable [T2Space E] [FiniteDimensional 𝕜 E]
/-- The continuous linear map induced by a linear map on a finite dimensional space -/
def toContinuousLinearMap : (E →ₗ[𝕜] F') ≃ₗ[𝕜] E →L[𝕜] F' where
toFun f := ⟨f, f.continuous_of_finiteDimensional⟩
invFun := (↑)
map_add' _ _ := rfl
map_smul' _ _ := rfl
left_inv _ := rfl
right_inv _ := ContinuousLinearMap.coe_injective rfl
#align linear_map.to_continuous_linear_map LinearMap.toContinuousLinearMap
@[simp]
theorem coe_toContinuousLinearMap' (f : E →ₗ[𝕜] F') : ⇑(LinearMap.toContinuousLinearMap f) = f :=
rfl
#align linear_map.coe_to_continuous_linear_map' LinearMap.coe_toContinuousLinearMap'
@[simp]
theorem coe_toContinuousLinearMap (f : E →ₗ[𝕜] F') :
((LinearMap.toContinuousLinearMap f) : E →ₗ[𝕜] F') = f :=
rfl
#align linear_map.coe_to_continuous_linear_map LinearMap.coe_toContinuousLinearMap
@[simp]
theorem coe_toContinuousLinearMap_symm :
⇑(toContinuousLinearMap : (E →ₗ[𝕜] F') ≃ₗ[𝕜] E →L[𝕜] F').symm =
((↑) : (E →L[𝕜] F') → E →ₗ[𝕜] F') :=
rfl
#align linear_map.coe_to_continuous_linear_map_symm LinearMap.coe_toContinuousLinearMap_symm
@[simp]
theorem det_toContinuousLinearMap (f : E →ₗ[𝕜] E) :
(LinearMap.toContinuousLinearMap f).det = LinearMap.det f :=
rfl
#align linear_map.det_to_continuous_linear_map LinearMap.det_toContinuousLinearMap
@[simp]
theorem ker_toContinuousLinearMap (f : E →ₗ[𝕜] F') :
ker (LinearMap.toContinuousLinearMap f) = ker f :=
rfl
#align linear_map.ker_to_continuous_linear_map LinearMap.ker_toContinuousLinearMap
@[simp]
theorem range_toContinuousLinearMap (f : E →ₗ[𝕜] F') :
range (LinearMap.toContinuousLinearMap f) = range f :=
rfl
#align linear_map.range_to_continuous_linear_map LinearMap.range_toContinuousLinearMap
/-- A surjective linear map `f` with finite dimensional codomain is an open map. -/
| Mathlib/Topology/Algebra/Module/FiniteDimension.lean | 330 | 339 | theorem isOpenMap_of_finiteDimensional (f : F →ₗ[𝕜] E) (hf : Function.Surjective f) :
IsOpenMap f := by |
rcases f.exists_rightInverse_of_surjective (LinearMap.range_eq_top.2 hf) with ⟨g, hg⟩
refine IsOpenMap.of_sections fun x => ⟨fun y => g (y - f x) + x, ?_, ?_, fun y => ?_⟩
· exact
((g.continuous_of_finiteDimensional.comp <| continuous_id.sub continuous_const).add
continuous_const).continuousAt
· simp only
rw [sub_self, map_zero, zero_add]
· simp only [map_sub, map_add, ← comp_apply f g, hg, id_apply, sub_add_cancel]
|
/-
Copyright (c) 2020 Kexing Ying and Kevin Buzzard. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kexing Ying, Kevin Buzzard, Yury Kudryashov
-/
import Mathlib.Algebra.BigOperators.GroupWithZero.Finset
import Mathlib.Algebra.Group.FiniteSupport
import Mathlib.Algebra.Module.Defs
import Mathlib.Algebra.Order.BigOperators.Group.Finset
import Mathlib.Data.Set.Subsingleton
#align_import algebra.big_operators.finprod from "leanprover-community/mathlib"@"d6fad0e5bf2d6f48da9175d25c3dc5706b3834ce"
/-!
# Finite products and sums over types and sets
We define products and sums over types and subsets of types, with no finiteness hypotheses.
All infinite products and sums are defined to be junk values (i.e. one or zero).
This approach is sometimes easier to use than `Finset.sum`,
when issues arise with `Finset` and `Fintype` being data.
## Main definitions
We use the following variables:
* `α`, `β` - types with no structure;
* `s`, `t` - sets
* `M`, `N` - additive or multiplicative commutative monoids
* `f`, `g` - functions
Definitions in this file:
* `finsum f : M` : the sum of `f x` as `x` ranges over the support of `f`, if it's finite.
Zero otherwise.
* `finprod f : M` : the product of `f x` as `x` ranges over the multiplicative support of `f`, if
it's finite. One otherwise.
## Notation
* `∑ᶠ i, f i` and `∑ᶠ i : α, f i` for `finsum f`
* `∏ᶠ i, f i` and `∏ᶠ i : α, f i` for `finprod f`
This notation works for functions `f : p → M`, where `p : Prop`, so the following works:
* `∑ᶠ i ∈ s, f i`, where `f : α → M`, `s : Set α` : sum over the set `s`;
* `∑ᶠ n < 5, f n`, where `f : ℕ → M` : same as `f 0 + f 1 + f 2 + f 3 + f 4`;
* `∏ᶠ (n >= -2) (hn : n < 3), f n`, where `f : ℤ → M` : same as `f (-2) * f (-1) * f 0 * f 1 * f 2`.
## Implementation notes
`finsum` and `finprod` is "yet another way of doing finite sums and products in Lean". However
experiments in the wild (e.g. with matroids) indicate that it is a helpful approach in settings
where the user is not interested in computability and wants to do reasoning without running into
typeclass diamonds caused by the constructive finiteness used in definitions such as `Finset` and
`Fintype`. By sticking solely to `Set.Finite` we avoid these problems. We are aware that there are
other solutions but for beginner mathematicians this approach is easier in practice.
Another application is the construction of a partition of unity from a collection of “bump”
function. In this case the finite set depends on the point and it's convenient to have a definition
that does not mention the set explicitly.
The first arguments in all definitions and lemmas is the codomain of the function of the big
operator. This is necessary for the heuristic in `@[to_additive]`.
See the documentation of `to_additive.attr` for more information.
We did not add `IsFinite (X : Type) : Prop`, because it is simply `Nonempty (Fintype X)`.
## Tags
finsum, finprod, finite sum, finite product
-/
open Function Set
/-!
### Definition and relation to `Finset.sum` and `Finset.prod`
-/
-- Porting note: Used to be section Sort
section sort
variable {G M N : Type*} {α β ι : Sort*} [CommMonoid M] [CommMonoid N]
section
/- Note: we use classical logic only for these definitions, to ensure that we do not write lemmas
with `Classical.dec` in their statement. -/
open scoped Classical
/-- Sum of `f x` as `x` ranges over the elements of the support of `f`, if it's finite. Zero
otherwise. -/
noncomputable irreducible_def finsum (lemma := finsum_def') [AddCommMonoid M] (f : α → M) : M :=
if h : (support (f ∘ PLift.down)).Finite then ∑ i ∈ h.toFinset, f i.down else 0
#align finsum finsum
/-- Product of `f x` as `x` ranges over the elements of the multiplicative support of `f`, if it's
finite. One otherwise. -/
@[to_additive existing]
noncomputable irreducible_def finprod (lemma := finprod_def') (f : α → M) : M :=
if h : (mulSupport (f ∘ PLift.down)).Finite then ∏ i ∈ h.toFinset, f i.down else 1
#align finprod finprod
attribute [to_additive existing] finprod_def'
end
open Batteries.ExtendedBinder
/-- `∑ᶠ x, f x` is notation for `finsum f`. It is the sum of `f x`, where `x` ranges over the
support of `f`, if it's finite, zero otherwise. Taking the sum over multiple arguments or
conditions is possible, e.g. `∏ᶠ (x) (y), f x y` and `∏ᶠ (x) (h: x ∈ s), f x`-/
notation3"∑ᶠ "(...)", "r:67:(scoped f => finsum f) => r
/-- `∏ᶠ x, f x` is notation for `finprod f`. It is the product of `f x`, where `x` ranges over the
multiplicative support of `f`, if it's finite, one otherwise. Taking the product over multiple
arguments or conditions is possible, e.g. `∏ᶠ (x) (y), f x y` and `∏ᶠ (x) (h: x ∈ s), f x`-/
notation3"∏ᶠ "(...)", "r:67:(scoped f => finprod f) => r
-- Porting note: The following ports the lean3 notation for this file, but is currently very fickle.
-- syntax (name := bigfinsum) "∑ᶠ" extBinders ", " term:67 : term
-- macro_rules (kind := bigfinsum)
-- | `(∑ᶠ $x:ident, $p) => `(finsum (fun $x:ident ↦ $p))
-- | `(∑ᶠ $x:ident : $t, $p) => `(finsum (fun $x:ident : $t ↦ $p))
-- | `(∑ᶠ $x:ident $b:binderPred, $p) =>
-- `(finsum fun $x => (finsum (α := satisfies_binder_pred% $x $b) (fun _ => $p)))
-- | `(∑ᶠ ($x:ident) ($h:ident : $t), $p) =>
-- `(finsum fun ($x) => finsum (α := $t) (fun $h => $p))
-- | `(∑ᶠ ($x:ident : $_) ($h:ident : $t), $p) =>
-- `(finsum fun ($x) => finsum (α := $t) (fun $h => $p))
-- | `(∑ᶠ ($x:ident) ($y:ident), $p) =>
-- `(finsum fun $x => (finsum fun $y => $p))
-- | `(∑ᶠ ($x:ident) ($y:ident) ($h:ident : $t), $p) =>
-- `(finsum fun $x => (finsum fun $y => (finsum (α := $t) fun $h => $p)))
-- | `(∑ᶠ ($x:ident) ($y:ident) ($z:ident), $p) =>
-- `(finsum fun $x => (finsum fun $y => (finsum fun $z => $p)))
-- | `(∑ᶠ ($x:ident) ($y:ident) ($z:ident) ($h:ident : $t), $p) =>
-- `(finsum fun $x => (finsum fun $y => (finsum fun $z => (finsum (α := $t) fun $h => $p))))
--
--
-- syntax (name := bigfinprod) "∏ᶠ " extBinders ", " term:67 : term
-- macro_rules (kind := bigfinprod)
-- | `(∏ᶠ $x:ident, $p) => `(finprod (fun $x:ident ↦ $p))
-- | `(∏ᶠ $x:ident : $t, $p) => `(finprod (fun $x:ident : $t ↦ $p))
-- | `(∏ᶠ $x:ident $b:binderPred, $p) =>
-- `(finprod fun $x => (finprod (α := satisfies_binder_pred% $x $b) (fun _ => $p)))
-- | `(∏ᶠ ($x:ident) ($h:ident : $t), $p) =>
-- `(finprod fun ($x) => finprod (α := $t) (fun $h => $p))
-- | `(∏ᶠ ($x:ident : $_) ($h:ident : $t), $p) =>
-- `(finprod fun ($x) => finprod (α := $t) (fun $h => $p))
-- | `(∏ᶠ ($x:ident) ($y:ident), $p) =>
-- `(finprod fun $x => (finprod fun $y => $p))
-- | `(∏ᶠ ($x:ident) ($y:ident) ($h:ident : $t), $p) =>
-- `(finprod fun $x => (finprod fun $y => (finprod (α := $t) fun $h => $p)))
-- | `(∏ᶠ ($x:ident) ($y:ident) ($z:ident), $p) =>
-- `(finprod fun $x => (finprod fun $y => (finprod fun $z => $p)))
-- | `(∏ᶠ ($x:ident) ($y:ident) ($z:ident) ($h:ident : $t), $p) =>
-- `(finprod fun $x => (finprod fun $y => (finprod fun $z =>
-- (finprod (α := $t) fun $h => $p))))
@[to_additive]
theorem finprod_eq_prod_plift_of_mulSupport_toFinset_subset {f : α → M}
(hf : (mulSupport (f ∘ PLift.down)).Finite) {s : Finset (PLift α)} (hs : hf.toFinset ⊆ s) :
∏ᶠ i, f i = ∏ i ∈ s, f i.down := by
rw [finprod, dif_pos]
refine Finset.prod_subset hs fun x _ hxf => ?_
rwa [hf.mem_toFinset, nmem_mulSupport] at hxf
#align finprod_eq_prod_plift_of_mul_support_to_finset_subset finprod_eq_prod_plift_of_mulSupport_toFinset_subset
#align finsum_eq_sum_plift_of_support_to_finset_subset finsum_eq_sum_plift_of_support_toFinset_subset
@[to_additive]
theorem finprod_eq_prod_plift_of_mulSupport_subset {f : α → M} {s : Finset (PLift α)}
(hs : mulSupport (f ∘ PLift.down) ⊆ s) : ∏ᶠ i, f i = ∏ i ∈ s, f i.down :=
finprod_eq_prod_plift_of_mulSupport_toFinset_subset (s.finite_toSet.subset hs) fun x hx => by
rw [Finite.mem_toFinset] at hx
exact hs hx
#align finprod_eq_prod_plift_of_mul_support_subset finprod_eq_prod_plift_of_mulSupport_subset
#align finsum_eq_sum_plift_of_support_subset finsum_eq_sum_plift_of_support_subset
@[to_additive (attr := simp)]
theorem finprod_one : (∏ᶠ _ : α, (1 : M)) = 1 := by
have : (mulSupport fun x : PLift α => (fun _ => 1 : α → M) x.down) ⊆ (∅ : Finset (PLift α)) :=
fun x h => by simp at h
rw [finprod_eq_prod_plift_of_mulSupport_subset this, Finset.prod_empty]
#align finprod_one finprod_one
#align finsum_zero finsum_zero
@[to_additive]
theorem finprod_of_isEmpty [IsEmpty α] (f : α → M) : ∏ᶠ i, f i = 1 := by
rw [← finprod_one]
congr
simp [eq_iff_true_of_subsingleton]
#align finprod_of_is_empty finprod_of_isEmpty
#align finsum_of_is_empty finsum_of_isEmpty
@[to_additive (attr := simp)]
theorem finprod_false (f : False → M) : ∏ᶠ i, f i = 1 :=
finprod_of_isEmpty _
#align finprod_false finprod_false
#align finsum_false finsum_false
@[to_additive]
theorem finprod_eq_single (f : α → M) (a : α) (ha : ∀ x, x ≠ a → f x = 1) :
∏ᶠ x, f x = f a := by
have : mulSupport (f ∘ PLift.down) ⊆ ({PLift.up a} : Finset (PLift α)) := by
intro x
contrapose
simpa [PLift.eq_up_iff_down_eq] using ha x.down
rw [finprod_eq_prod_plift_of_mulSupport_subset this, Finset.prod_singleton]
#align finprod_eq_single finprod_eq_single
#align finsum_eq_single finsum_eq_single
@[to_additive]
theorem finprod_unique [Unique α] (f : α → M) : ∏ᶠ i, f i = f default :=
finprod_eq_single f default fun _x hx => (hx <| Unique.eq_default _).elim
#align finprod_unique finprod_unique
#align finsum_unique finsum_unique
@[to_additive (attr := simp)]
theorem finprod_true (f : True → M) : ∏ᶠ i, f i = f trivial :=
@finprod_unique M True _ ⟨⟨trivial⟩, fun _ => rfl⟩ f
#align finprod_true finprod_true
#align finsum_true finsum_true
@[to_additive]
theorem finprod_eq_dif {p : Prop} [Decidable p] (f : p → M) :
∏ᶠ i, f i = if h : p then f h else 1 := by
split_ifs with h
· haveI : Unique p := ⟨⟨h⟩, fun _ => rfl⟩
exact finprod_unique f
· haveI : IsEmpty p := ⟨h⟩
exact finprod_of_isEmpty f
#align finprod_eq_dif finprod_eq_dif
#align finsum_eq_dif finsum_eq_dif
@[to_additive]
theorem finprod_eq_if {p : Prop} [Decidable p] {x : M} : ∏ᶠ _ : p, x = if p then x else 1 :=
finprod_eq_dif fun _ => x
#align finprod_eq_if finprod_eq_if
#align finsum_eq_if finsum_eq_if
@[to_additive]
theorem finprod_congr {f g : α → M} (h : ∀ x, f x = g x) : finprod f = finprod g :=
congr_arg _ <| funext h
#align finprod_congr finprod_congr
#align finsum_congr finsum_congr
@[to_additive (attr := congr)]
theorem finprod_congr_Prop {p q : Prop} {f : p → M} {g : q → M} (hpq : p = q)
(hfg : ∀ h : q, f (hpq.mpr h) = g h) : finprod f = finprod g := by
subst q
exact finprod_congr hfg
#align finprod_congr_Prop finprod_congr_Prop
#align finsum_congr_Prop finsum_congr_Prop
/-- To prove a property of a finite product, it suffices to prove that the property is
multiplicative and holds on the factors. -/
@[to_additive
"To prove a property of a finite sum, it suffices to prove that the property is
additive and holds on the summands."]
theorem finprod_induction {f : α → M} (p : M → Prop) (hp₀ : p 1)
(hp₁ : ∀ x y, p x → p y → p (x * y)) (hp₂ : ∀ i, p (f i)) : p (∏ᶠ i, f i) := by
rw [finprod]
split_ifs
exacts [Finset.prod_induction _ _ hp₁ hp₀ fun i _ => hp₂ _, hp₀]
#align finprod_induction finprod_induction
#align finsum_induction finsum_induction
theorem finprod_nonneg {R : Type*} [OrderedCommSemiring R] {f : α → R} (hf : ∀ x, 0 ≤ f x) :
0 ≤ ∏ᶠ x, f x :=
finprod_induction (fun x => 0 ≤ x) zero_le_one (fun _ _ => mul_nonneg) hf
#align finprod_nonneg finprod_nonneg
@[to_additive finsum_nonneg]
theorem one_le_finprod' {M : Type*} [OrderedCommMonoid M] {f : α → M} (hf : ∀ i, 1 ≤ f i) :
1 ≤ ∏ᶠ i, f i :=
finprod_induction _ le_rfl (fun _ _ => one_le_mul) hf
#align one_le_finprod' one_le_finprod'
#align finsum_nonneg finsum_nonneg
@[to_additive]
theorem MonoidHom.map_finprod_plift (f : M →* N) (g : α → M)
(h : (mulSupport <| g ∘ PLift.down).Finite) : f (∏ᶠ x, g x) = ∏ᶠ x, f (g x) := by
rw [finprod_eq_prod_plift_of_mulSupport_subset h.coe_toFinset.ge,
finprod_eq_prod_plift_of_mulSupport_subset, map_prod]
rw [h.coe_toFinset]
exact mulSupport_comp_subset f.map_one (g ∘ PLift.down)
#align monoid_hom.map_finprod_plift MonoidHom.map_finprod_plift
#align add_monoid_hom.map_finsum_plift AddMonoidHom.map_finsum_plift
@[to_additive]
theorem MonoidHom.map_finprod_Prop {p : Prop} (f : M →* N) (g : p → M) :
f (∏ᶠ x, g x) = ∏ᶠ x, f (g x) :=
f.map_finprod_plift g (Set.toFinite _)
#align monoid_hom.map_finprod_Prop MonoidHom.map_finprod_Prop
#align add_monoid_hom.map_finsum_Prop AddMonoidHom.map_finsum_Prop
@[to_additive]
theorem MonoidHom.map_finprod_of_preimage_one (f : M →* N) (hf : ∀ x, f x = 1 → x = 1) (g : α → M) :
f (∏ᶠ i, g i) = ∏ᶠ i, f (g i) := by
by_cases hg : (mulSupport <| g ∘ PLift.down).Finite; · exact f.map_finprod_plift g hg
rw [finprod, dif_neg, f.map_one, finprod, dif_neg]
exacts [Infinite.mono (fun x hx => mt (hf (g x.down)) hx) hg, hg]
#align monoid_hom.map_finprod_of_preimage_one MonoidHom.map_finprod_of_preimage_one
#align add_monoid_hom.map_finsum_of_preimage_zero AddMonoidHom.map_finsum_of_preimage_zero
@[to_additive]
theorem MonoidHom.map_finprod_of_injective (g : M →* N) (hg : Injective g) (f : α → M) :
g (∏ᶠ i, f i) = ∏ᶠ i, g (f i) :=
g.map_finprod_of_preimage_one (fun _ => (hg.eq_iff' g.map_one).mp) f
#align monoid_hom.map_finprod_of_injective MonoidHom.map_finprod_of_injective
#align add_monoid_hom.map_finsum_of_injective AddMonoidHom.map_finsum_of_injective
@[to_additive]
theorem MulEquiv.map_finprod (g : M ≃* N) (f : α → M) : g (∏ᶠ i, f i) = ∏ᶠ i, g (f i) :=
g.toMonoidHom.map_finprod_of_injective (EquivLike.injective g) f
#align mul_equiv.map_finprod MulEquiv.map_finprod
#align add_equiv.map_finsum AddEquiv.map_finsum
/-- The `NoZeroSMulDivisors` makes sure that the result holds even when the support of `f` is
infinite. For a more usual version assuming `(support f).Finite` instead, see `finsum_smul'`. -/
theorem finsum_smul {R M : Type*} [Ring R] [AddCommGroup M] [Module R M] [NoZeroSMulDivisors R M]
(f : ι → R) (x : M) : (∑ᶠ i, f i) • x = ∑ᶠ i, f i • x := by
rcases eq_or_ne x 0 with (rfl | hx)
· simp
· exact ((smulAddHom R M).flip x).map_finsum_of_injective (smul_left_injective R hx) _
#align finsum_smul finsum_smul
/-- The `NoZeroSMulDivisors` makes sure that the result holds even when the support of `f` is
infinite. For a more usual version assuming `(support f).Finite` instead, see `smul_finsum'`. -/
theorem smul_finsum {R M : Type*} [Ring R] [AddCommGroup M] [Module R M] [NoZeroSMulDivisors R M]
(c : R) (f : ι → M) : (c • ∑ᶠ i, f i) = ∑ᶠ i, c • f i := by
rcases eq_or_ne c 0 with (rfl | hc)
· simp
· exact (smulAddHom R M c).map_finsum_of_injective (smul_right_injective M hc) _
#align smul_finsum smul_finsum
@[to_additive]
theorem finprod_inv_distrib [DivisionCommMonoid G] (f : α → G) : (∏ᶠ x, (f x)⁻¹) = (∏ᶠ x, f x)⁻¹ :=
((MulEquiv.inv G).map_finprod f).symm
#align finprod_inv_distrib finprod_inv_distrib
#align finsum_neg_distrib finsum_neg_distrib
end sort
-- Porting note: Used to be section Type
section type
variable {α β ι G M N : Type*} [CommMonoid M] [CommMonoid N]
@[to_additive]
theorem finprod_eq_mulIndicator_apply (s : Set α) (f : α → M) (a : α) :
∏ᶠ _ : a ∈ s, f a = mulIndicator s f a := by
classical convert finprod_eq_if (M := M) (p := a ∈ s) (x := f a)
#align finprod_eq_mul_indicator_apply finprod_eq_mulIndicator_apply
#align finsum_eq_indicator_apply finsum_eq_indicator_apply
@[to_additive (attr := simp)]
theorem finprod_mem_mulSupport (f : α → M) (a : α) : ∏ᶠ _ : f a ≠ 1, f a = f a := by
rw [← mem_mulSupport, finprod_eq_mulIndicator_apply, mulIndicator_mulSupport]
#align finprod_mem_mul_support finprod_mem_mulSupport
#align finsum_mem_support finsum_mem_support
@[to_additive]
theorem finprod_mem_def (s : Set α) (f : α → M) : ∏ᶠ a ∈ s, f a = ∏ᶠ a, mulIndicator s f a :=
finprod_congr <| finprod_eq_mulIndicator_apply s f
#align finprod_mem_def finprod_mem_def
#align finsum_mem_def finsum_mem_def
@[to_additive]
theorem finprod_eq_prod_of_mulSupport_subset (f : α → M) {s : Finset α} (h : mulSupport f ⊆ s) :
∏ᶠ i, f i = ∏ i ∈ s, f i := by
have A : mulSupport (f ∘ PLift.down) = Equiv.plift.symm '' mulSupport f := by
rw [mulSupport_comp_eq_preimage]
exact (Equiv.plift.symm.image_eq_preimage _).symm
have : mulSupport (f ∘ PLift.down) ⊆ s.map Equiv.plift.symm.toEmbedding := by
rw [A, Finset.coe_map]
exact image_subset _ h
rw [finprod_eq_prod_plift_of_mulSupport_subset this]
simp only [Finset.prod_map, Equiv.coe_toEmbedding]
congr
#align finprod_eq_prod_of_mul_support_subset finprod_eq_prod_of_mulSupport_subset
#align finsum_eq_sum_of_support_subset finsum_eq_sum_of_support_subset
@[to_additive]
theorem finprod_eq_prod_of_mulSupport_toFinset_subset (f : α → M) (hf : (mulSupport f).Finite)
{s : Finset α} (h : hf.toFinset ⊆ s) : ∏ᶠ i, f i = ∏ i ∈ s, f i :=
finprod_eq_prod_of_mulSupport_subset _ fun _ hx => h <| hf.mem_toFinset.2 hx
#align finprod_eq_prod_of_mul_support_to_finset_subset finprod_eq_prod_of_mulSupport_toFinset_subset
#align finsum_eq_sum_of_support_to_finset_subset finsum_eq_sum_of_support_toFinset_subset
@[to_additive]
theorem finprod_eq_finset_prod_of_mulSupport_subset (f : α → M) {s : Finset α}
(h : mulSupport f ⊆ (s : Set α)) : ∏ᶠ i, f i = ∏ i ∈ s, f i :=
haveI h' : (s.finite_toSet.subset h).toFinset ⊆ s := by
simpa [← Finset.coe_subset, Set.coe_toFinset]
finprod_eq_prod_of_mulSupport_toFinset_subset _ _ h'
#align finprod_eq_finset_prod_of_mul_support_subset finprod_eq_finset_prod_of_mulSupport_subset
#align finsum_eq_finset_sum_of_support_subset finsum_eq_finset_sum_of_support_subset
@[to_additive]
theorem finprod_def (f : α → M) [Decidable (mulSupport f).Finite] :
∏ᶠ i : α, f i = if h : (mulSupport f).Finite then ∏ i ∈ h.toFinset, f i else 1 := by
split_ifs with h
· exact finprod_eq_prod_of_mulSupport_toFinset_subset _ h (Finset.Subset.refl _)
· rw [finprod, dif_neg]
rw [mulSupport_comp_eq_preimage]
exact mt (fun hf => hf.of_preimage Equiv.plift.surjective) h
#align finprod_def finprod_def
#align finsum_def finsum_def
@[to_additive]
theorem finprod_of_infinite_mulSupport {f : α → M} (hf : (mulSupport f).Infinite) :
∏ᶠ i, f i = 1 := by classical rw [finprod_def, dif_neg hf]
#align finprod_of_infinite_mul_support finprod_of_infinite_mulSupport
#align finsum_of_infinite_support finsum_of_infinite_support
@[to_additive]
theorem finprod_eq_prod (f : α → M) (hf : (mulSupport f).Finite) :
∏ᶠ i : α, f i = ∏ i ∈ hf.toFinset, f i := by classical rw [finprod_def, dif_pos hf]
#align finprod_eq_prod finprod_eq_prod
#align finsum_eq_sum finsum_eq_sum
@[to_additive]
theorem finprod_eq_prod_of_fintype [Fintype α] (f : α → M) : ∏ᶠ i : α, f i = ∏ i, f i :=
finprod_eq_prod_of_mulSupport_toFinset_subset _ (Set.toFinite _) <| Finset.subset_univ _
#align finprod_eq_prod_of_fintype finprod_eq_prod_of_fintype
#align finsum_eq_sum_of_fintype finsum_eq_sum_of_fintype
@[to_additive]
theorem finprod_cond_eq_prod_of_cond_iff (f : α → M) {p : α → Prop} {t : Finset α}
(h : ∀ {x}, f x ≠ 1 → (p x ↔ x ∈ t)) : (∏ᶠ (i) (_ : p i), f i) = ∏ i ∈ t, f i := by
set s := { x | p x }
have : mulSupport (s.mulIndicator f) ⊆ t := by
rw [Set.mulSupport_mulIndicator]
intro x hx
exact (h hx.2).1 hx.1
erw [finprod_mem_def, finprod_eq_prod_of_mulSupport_subset _ this]
refine Finset.prod_congr rfl fun x hx => mulIndicator_apply_eq_self.2 fun hxs => ?_
contrapose! hxs
exact (h hxs).2 hx
#align finprod_cond_eq_prod_of_cond_iff finprod_cond_eq_prod_of_cond_iff
#align finsum_cond_eq_sum_of_cond_iff finsum_cond_eq_sum_of_cond_iff
@[to_additive]
theorem finprod_cond_ne (f : α → M) (a : α) [DecidableEq α] (hf : (mulSupport f).Finite) :
(∏ᶠ (i) (_ : i ≠ a), f i) = ∏ i ∈ hf.toFinset.erase a, f i := by
apply finprod_cond_eq_prod_of_cond_iff
intro x hx
rw [Finset.mem_erase, Finite.mem_toFinset, mem_mulSupport]
exact ⟨fun h => And.intro h hx, fun h => h.1⟩
#align finprod_cond_ne finprod_cond_ne
#align finsum_cond_ne finsum_cond_ne
@[to_additive]
theorem finprod_mem_eq_prod_of_inter_mulSupport_eq (f : α → M) {s : Set α} {t : Finset α}
(h : s ∩ mulSupport f = t.toSet ∩ mulSupport f) : ∏ᶠ i ∈ s, f i = ∏ i ∈ t, f i :=
finprod_cond_eq_prod_of_cond_iff _ <| by
intro x hxf
rw [← mem_mulSupport] at hxf
refine ⟨fun hx => ?_, fun hx => ?_⟩
· refine ((mem_inter_iff x t (mulSupport f)).mp ?_).1
rw [← Set.ext_iff.mp h x, mem_inter_iff]
exact ⟨hx, hxf⟩
· refine ((mem_inter_iff x s (mulSupport f)).mp ?_).1
rw [Set.ext_iff.mp h x, mem_inter_iff]
exact ⟨hx, hxf⟩
#align finprod_mem_eq_prod_of_inter_mul_support_eq finprod_mem_eq_prod_of_inter_mulSupport_eq
#align finsum_mem_eq_sum_of_inter_support_eq finsum_mem_eq_sum_of_inter_support_eq
@[to_additive]
theorem finprod_mem_eq_prod_of_subset (f : α → M) {s : Set α} {t : Finset α}
(h₁ : s ∩ mulSupport f ⊆ t) (h₂ : ↑t ⊆ s) : ∏ᶠ i ∈ s, f i = ∏ i ∈ t, f i :=
finprod_cond_eq_prod_of_cond_iff _ fun hx => ⟨fun h => h₁ ⟨h, hx⟩, fun h => h₂ h⟩
#align finprod_mem_eq_prod_of_subset finprod_mem_eq_prod_of_subset
#align finsum_mem_eq_sum_of_subset finsum_mem_eq_sum_of_subset
@[to_additive]
theorem finprod_mem_eq_prod (f : α → M) {s : Set α} (hf : (s ∩ mulSupport f).Finite) :
∏ᶠ i ∈ s, f i = ∏ i ∈ hf.toFinset, f i :=
finprod_mem_eq_prod_of_inter_mulSupport_eq _ <| by simp [inter_assoc]
#align finprod_mem_eq_prod finprod_mem_eq_prod
#align finsum_mem_eq_sum finsum_mem_eq_sum
@[to_additive]
theorem finprod_mem_eq_prod_filter (f : α → M) (s : Set α) [DecidablePred (· ∈ s)]
(hf : (mulSupport f).Finite) :
∏ᶠ i ∈ s, f i = ∏ i ∈ Finset.filter (· ∈ s) hf.toFinset, f i :=
finprod_mem_eq_prod_of_inter_mulSupport_eq _ <| by
ext x
simp [and_comm]
#align finprod_mem_eq_prod_filter finprod_mem_eq_prod_filter
#align finsum_mem_eq_sum_filter finsum_mem_eq_sum_filter
@[to_additive]
theorem finprod_mem_eq_toFinset_prod (f : α → M) (s : Set α) [Fintype s] :
∏ᶠ i ∈ s, f i = ∏ i ∈ s.toFinset, f i :=
finprod_mem_eq_prod_of_inter_mulSupport_eq _ <| by simp_rw [coe_toFinset s]
#align finprod_mem_eq_to_finset_prod finprod_mem_eq_toFinset_prod
#align finsum_mem_eq_to_finset_sum finsum_mem_eq_toFinset_sum
@[to_additive]
theorem finprod_mem_eq_finite_toFinset_prod (f : α → M) {s : Set α} (hs : s.Finite) :
∏ᶠ i ∈ s, f i = ∏ i ∈ hs.toFinset, f i :=
finprod_mem_eq_prod_of_inter_mulSupport_eq _ <| by rw [hs.coe_toFinset]
#align finprod_mem_eq_finite_to_finset_prod finprod_mem_eq_finite_toFinset_prod
#align finsum_mem_eq_finite_to_finset_sum finsum_mem_eq_finite_toFinset_sum
@[to_additive]
theorem finprod_mem_finset_eq_prod (f : α → M) (s : Finset α) : ∏ᶠ i ∈ s, f i = ∏ i ∈ s, f i :=
finprod_mem_eq_prod_of_inter_mulSupport_eq _ rfl
#align finprod_mem_finset_eq_prod finprod_mem_finset_eq_prod
#align finsum_mem_finset_eq_sum finsum_mem_finset_eq_sum
@[to_additive]
theorem finprod_mem_coe_finset (f : α → M) (s : Finset α) :
(∏ᶠ i ∈ (s : Set α), f i) = ∏ i ∈ s, f i :=
finprod_mem_eq_prod_of_inter_mulSupport_eq _ rfl
#align finprod_mem_coe_finset finprod_mem_coe_finset
#align finsum_mem_coe_finset finsum_mem_coe_finset
@[to_additive]
theorem finprod_mem_eq_one_of_infinite {f : α → M} {s : Set α} (hs : (s ∩ mulSupport f).Infinite) :
∏ᶠ i ∈ s, f i = 1 := by
rw [finprod_mem_def]
apply finprod_of_infinite_mulSupport
rwa [← mulSupport_mulIndicator] at hs
#align finprod_mem_eq_one_of_infinite finprod_mem_eq_one_of_infinite
#align finsum_mem_eq_zero_of_infinite finsum_mem_eq_zero_of_infinite
@[to_additive]
| Mathlib/Algebra/BigOperators/Finprod.lean | 541 | 542 | theorem finprod_mem_eq_one_of_forall_eq_one {f : α → M} {s : Set α} (h : ∀ x ∈ s, f x = 1) :
∏ᶠ i ∈ s, f i = 1 := by | simp (config := { contextual := true }) [h]
|
/-
Copyright (c) 2021 Thomas Browning. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Thomas Browning
-/
import Mathlib.Algebra.BigOperators.GroupWithZero.Finset
import Mathlib.Data.Finite.Card
import Mathlib.GroupTheory.Finiteness
import Mathlib.GroupTheory.GroupAction.Quotient
#align_import group_theory.index from "leanprover-community/mathlib"@"dc6c365e751e34d100e80fe6e314c3c3e0fd2988"
/-!
# Index of a Subgroup
In this file we define the index of a subgroup, and prove several divisibility properties.
Several theorems proved in this file are known as Lagrange's theorem.
## Main definitions
- `H.index` : the index of `H : Subgroup G` as a natural number,
and returns 0 if the index is infinite.
- `H.relindex K` : the relative index of `H : Subgroup G` in `K : Subgroup G` as a natural number,
and returns 0 if the relative index is infinite.
# Main results
- `card_mul_index` : `Nat.card H * H.index = Nat.card G`
- `index_mul_card` : `H.index * Fintype.card H = Fintype.card G`
- `index_dvd_card` : `H.index ∣ Fintype.card G`
- `relindex_mul_index` : If `H ≤ K`, then `H.relindex K * K.index = H.index`
- `index_dvd_of_le` : If `H ≤ K`, then `K.index ∣ H.index`
- `relindex_mul_relindex` : `relindex` is multiplicative in towers
-/
namespace Subgroup
open Cardinal
variable {G : Type*} [Group G] (H K L : Subgroup G)
/-- The index of a subgroup as a natural number, and returns 0 if the index is infinite. -/
@[to_additive "The index of a subgroup as a natural number,
and returns 0 if the index is infinite."]
noncomputable def index : ℕ :=
Nat.card (G ⧸ H)
#align subgroup.index Subgroup.index
#align add_subgroup.index AddSubgroup.index
/-- The relative index of a subgroup as a natural number,
and returns 0 if the relative index is infinite. -/
@[to_additive "The relative index of a subgroup as a natural number,
and returns 0 if the relative index is infinite."]
noncomputable def relindex : ℕ :=
(H.subgroupOf K).index
#align subgroup.relindex Subgroup.relindex
#align add_subgroup.relindex AddSubgroup.relindex
@[to_additive]
theorem index_comap_of_surjective {G' : Type*} [Group G'] {f : G' →* G}
(hf : Function.Surjective f) : (H.comap f).index = H.index := by
letI := QuotientGroup.leftRel H
letI := QuotientGroup.leftRel (H.comap f)
have key : ∀ x y : G', Setoid.r x y ↔ Setoid.r (f x) (f y) := by
simp only [QuotientGroup.leftRel_apply]
exact fun x y => iff_of_eq (congr_arg (· ∈ H) (by rw [f.map_mul, f.map_inv]))
refine Cardinal.toNat_congr (Equiv.ofBijective (Quotient.map' f fun x y => (key x y).mp) ⟨?_, ?_⟩)
· simp_rw [← Quotient.eq''] at key
refine Quotient.ind' fun x => ?_
refine Quotient.ind' fun y => ?_
exact (key x y).mpr
· refine Quotient.ind' fun x => ?_
obtain ⟨y, hy⟩ := hf x
exact ⟨y, (Quotient.map'_mk'' f _ y).trans (congr_arg Quotient.mk'' hy)⟩
#align subgroup.index_comap_of_surjective Subgroup.index_comap_of_surjective
#align add_subgroup.index_comap_of_surjective AddSubgroup.index_comap_of_surjective
@[to_additive]
theorem index_comap {G' : Type*} [Group G'] (f : G' →* G) :
(H.comap f).index = H.relindex f.range :=
Eq.trans (congr_arg index (by rfl))
((H.subgroupOf f.range).index_comap_of_surjective f.rangeRestrict_surjective)
#align subgroup.index_comap Subgroup.index_comap
#align add_subgroup.index_comap AddSubgroup.index_comap
@[to_additive]
theorem relindex_comap {G' : Type*} [Group G'] (f : G' →* G) (K : Subgroup G') :
relindex (comap f H) K = relindex H (map f K) := by
rw [relindex, subgroupOf, comap_comap, index_comap, ← f.map_range, K.subtype_range]
#align subgroup.relindex_comap Subgroup.relindex_comap
#align add_subgroup.relindex_comap AddSubgroup.relindex_comap
variable {H K L}
@[to_additive relindex_mul_index]
theorem relindex_mul_index (h : H ≤ K) : H.relindex K * K.index = H.index :=
((mul_comm _ _).trans (Cardinal.toNat_mul _ _).symm).trans
(congr_arg Cardinal.toNat (Equiv.cardinal_eq (quotientEquivProdOfLE h))).symm
#align subgroup.relindex_mul_index Subgroup.relindex_mul_index
#align add_subgroup.relindex_mul_index AddSubgroup.relindex_mul_index
@[to_additive]
theorem index_dvd_of_le (h : H ≤ K) : K.index ∣ H.index :=
dvd_of_mul_left_eq (H.relindex K) (relindex_mul_index h)
#align subgroup.index_dvd_of_le Subgroup.index_dvd_of_le
#align add_subgroup.index_dvd_of_le AddSubgroup.index_dvd_of_le
@[to_additive]
theorem relindex_dvd_index_of_le (h : H ≤ K) : H.relindex K ∣ H.index :=
dvd_of_mul_right_eq K.index (relindex_mul_index h)
#align subgroup.relindex_dvd_index_of_le Subgroup.relindex_dvd_index_of_le
#align add_subgroup.relindex_dvd_index_of_le AddSubgroup.relindex_dvd_index_of_le
@[to_additive]
theorem relindex_subgroupOf (hKL : K ≤ L) :
(H.subgroupOf L).relindex (K.subgroupOf L) = H.relindex K :=
((index_comap (H.subgroupOf L) (inclusion hKL)).trans (congr_arg _ (inclusion_range hKL))).symm
#align subgroup.relindex_subgroup_of Subgroup.relindex_subgroupOf
#align add_subgroup.relindex_add_subgroup_of AddSubgroup.relindex_addSubgroupOf
variable (H K L)
@[to_additive relindex_mul_relindex]
theorem relindex_mul_relindex (hHK : H ≤ K) (hKL : K ≤ L) :
H.relindex K * K.relindex L = H.relindex L := by
rw [← relindex_subgroupOf hKL]
exact relindex_mul_index fun x hx => hHK hx
#align subgroup.relindex_mul_relindex Subgroup.relindex_mul_relindex
#align add_subgroup.relindex_mul_relindex AddSubgroup.relindex_mul_relindex
@[to_additive]
theorem inf_relindex_right : (H ⊓ K).relindex K = H.relindex K := by
rw [relindex, relindex, inf_subgroupOf_right]
#align subgroup.inf_relindex_right Subgroup.inf_relindex_right
#align add_subgroup.inf_relindex_right AddSubgroup.inf_relindex_right
@[to_additive]
theorem inf_relindex_left : (H ⊓ K).relindex H = K.relindex H := by
rw [inf_comm, inf_relindex_right]
#align subgroup.inf_relindex_left Subgroup.inf_relindex_left
#align add_subgroup.inf_relindex_left AddSubgroup.inf_relindex_left
@[to_additive relindex_inf_mul_relindex]
theorem relindex_inf_mul_relindex : H.relindex (K ⊓ L) * K.relindex L = (H ⊓ K).relindex L := by
rw [← inf_relindex_right H (K ⊓ L), ← inf_relindex_right K L, ← inf_relindex_right (H ⊓ K) L,
inf_assoc, relindex_mul_relindex (H ⊓ (K ⊓ L)) (K ⊓ L) L inf_le_right inf_le_right]
#align subgroup.relindex_inf_mul_relindex Subgroup.relindex_inf_mul_relindex
#align add_subgroup.relindex_inf_mul_relindex AddSubgroup.relindex_inf_mul_relindex
@[to_additive (attr := simp)]
theorem relindex_sup_right [K.Normal] : K.relindex (H ⊔ K) = K.relindex H :=
Nat.card_congr (QuotientGroup.quotientInfEquivProdNormalQuotient H K).toEquiv.symm
#align subgroup.relindex_sup_right Subgroup.relindex_sup_right
#align add_subgroup.relindex_sup_right AddSubgroup.relindex_sup_right
@[to_additive (attr := simp)]
theorem relindex_sup_left [K.Normal] : K.relindex (K ⊔ H) = K.relindex H := by
rw [sup_comm, relindex_sup_right]
#align subgroup.relindex_sup_left Subgroup.relindex_sup_left
#align add_subgroup.relindex_sup_left AddSubgroup.relindex_sup_left
@[to_additive]
theorem relindex_dvd_index_of_normal [H.Normal] : H.relindex K ∣ H.index :=
relindex_sup_right K H ▸ relindex_dvd_index_of_le le_sup_right
#align subgroup.relindex_dvd_index_of_normal Subgroup.relindex_dvd_index_of_normal
#align add_subgroup.relindex_dvd_index_of_normal AddSubgroup.relindex_dvd_index_of_normal
variable {H K}
@[to_additive]
theorem relindex_dvd_of_le_left (hHK : H ≤ K) : K.relindex L ∣ H.relindex L :=
inf_of_le_left hHK ▸ dvd_of_mul_left_eq _ (relindex_inf_mul_relindex _ _ _)
#align subgroup.relindex_dvd_of_le_left Subgroup.relindex_dvd_of_le_left
#align add_subgroup.relindex_dvd_of_le_left AddSubgroup.relindex_dvd_of_le_left
/-- A subgroup has index two if and only if there exists `a` such that for all `b`, exactly one
of `b * a` and `b` belong to `H`. -/
@[to_additive "An additive subgroup has index two if and only if there exists `a` such that
for all `b`, exactly one of `b + a` and `b` belong to `H`."]
theorem index_eq_two_iff : H.index = 2 ↔ ∃ a, ∀ b, Xor' (b * a ∈ H) (b ∈ H) := by
simp only [index, Nat.card_eq_two_iff' ((1 : G) : G ⧸ H), ExistsUnique, inv_mem_iff,
QuotientGroup.exists_mk, QuotientGroup.forall_mk, Ne, QuotientGroup.eq, mul_one,
xor_iff_iff_not]
refine exists_congr fun a =>
⟨fun ha b => ⟨fun hba hb => ?_, fun hb => ?_⟩, fun ha => ⟨?_, fun b hb => ?_⟩⟩
· exact ha.1 ((mul_mem_cancel_left hb).1 hba)
· exact inv_inv b ▸ ha.2 _ (mt (inv_mem_iff (x := b)).1 hb)
· rw [← inv_mem_iff (x := a), ← ha, inv_mul_self]
exact one_mem _
· rwa [ha, inv_mem_iff (x := b)]
#align subgroup.index_eq_two_iff Subgroup.index_eq_two_iff
#align add_subgroup.index_eq_two_iff AddSubgroup.index_eq_two_iff
@[to_additive]
theorem mul_mem_iff_of_index_two (h : H.index = 2) {a b : G} : a * b ∈ H ↔ (a ∈ H ↔ b ∈ H) := by
by_cases ha : a ∈ H; · simp only [ha, true_iff_iff, mul_mem_cancel_left ha]
by_cases hb : b ∈ H; · simp only [hb, iff_true_iff, mul_mem_cancel_right hb]
simp only [ha, hb, iff_self_iff, iff_true_iff]
rcases index_eq_two_iff.1 h with ⟨c, hc⟩
refine (hc _).or.resolve_left ?_
rwa [mul_assoc, mul_mem_cancel_right ((hc _).or.resolve_right hb)]
#align subgroup.mul_mem_iff_of_index_two Subgroup.mul_mem_iff_of_index_two
#align add_subgroup.add_mem_iff_of_index_two AddSubgroup.add_mem_iff_of_index_two
@[to_additive]
theorem mul_self_mem_of_index_two (h : H.index = 2) (a : G) : a * a ∈ H := by
rw [mul_mem_iff_of_index_two h]
#align subgroup.mul_self_mem_of_index_two Subgroup.mul_self_mem_of_index_two
#align add_subgroup.add_self_mem_of_index_two AddSubgroup.add_self_mem_of_index_two
@[to_additive two_smul_mem_of_index_two]
theorem sq_mem_of_index_two (h : H.index = 2) (a : G) : a ^ 2 ∈ H :=
(pow_two a).symm ▸ mul_self_mem_of_index_two h a
#align subgroup.sq_mem_of_index_two Subgroup.sq_mem_of_index_two
#align add_subgroup.two_smul_mem_of_index_two AddSubgroup.two_smul_mem_of_index_two
variable (H K)
-- Porting note: had to replace `Cardinal.toNat_eq_one_iff_unique` with `Nat.card_eq_one_iff_unique`
@[to_additive (attr := simp)]
theorem index_top : (⊤ : Subgroup G).index = 1 :=
Nat.card_eq_one_iff_unique.mpr ⟨QuotientGroup.subsingleton_quotient_top, ⟨1⟩⟩
#align subgroup.index_top Subgroup.index_top
#align add_subgroup.index_top AddSubgroup.index_top
@[to_additive (attr := simp)]
theorem index_bot : (⊥ : Subgroup G).index = Nat.card G :=
Cardinal.toNat_congr QuotientGroup.quotientBot.toEquiv
#align subgroup.index_bot Subgroup.index_bot
#align add_subgroup.index_bot AddSubgroup.index_bot
@[to_additive]
theorem index_bot_eq_card [Fintype G] : (⊥ : Subgroup G).index = Fintype.card G :=
index_bot.trans Nat.card_eq_fintype_card
#align subgroup.index_bot_eq_card Subgroup.index_bot_eq_card
#align add_subgroup.index_bot_eq_card AddSubgroup.index_bot_eq_card
@[to_additive (attr := simp)]
theorem relindex_top_left : (⊤ : Subgroup G).relindex H = 1 :=
index_top
#align subgroup.relindex_top_left Subgroup.relindex_top_left
#align add_subgroup.relindex_top_left AddSubgroup.relindex_top_left
@[to_additive (attr := simp)]
theorem relindex_top_right : H.relindex ⊤ = H.index := by
rw [← relindex_mul_index (show H ≤ ⊤ from le_top), index_top, mul_one]
#align subgroup.relindex_top_right Subgroup.relindex_top_right
#align add_subgroup.relindex_top_right AddSubgroup.relindex_top_right
@[to_additive (attr := simp)]
theorem relindex_bot_left : (⊥ : Subgroup G).relindex H = Nat.card H := by
rw [relindex, bot_subgroupOf, index_bot]
#align subgroup.relindex_bot_left Subgroup.relindex_bot_left
#align add_subgroup.relindex_bot_left AddSubgroup.relindex_bot_left
@[to_additive]
theorem relindex_bot_left_eq_card [Fintype H] : (⊥ : Subgroup G).relindex H = Fintype.card H :=
H.relindex_bot_left.trans Nat.card_eq_fintype_card
#align subgroup.relindex_bot_left_eq_card Subgroup.relindex_bot_left_eq_card
#align add_subgroup.relindex_bot_left_eq_card AddSubgroup.relindex_bot_left_eq_card
@[to_additive (attr := simp)]
theorem relindex_bot_right : H.relindex ⊥ = 1 := by rw [relindex, subgroupOf_bot_eq_top, index_top]
#align subgroup.relindex_bot_right Subgroup.relindex_bot_right
#align add_subgroup.relindex_bot_right AddSubgroup.relindex_bot_right
@[to_additive (attr := simp)]
theorem relindex_self : H.relindex H = 1 := by rw [relindex, subgroupOf_self, index_top]
#align subgroup.relindex_self Subgroup.relindex_self
#align add_subgroup.relindex_self AddSubgroup.relindex_self
@[to_additive]
theorem index_ker {H} [Group H] (f : G →* H) : f.ker.index = Nat.card (Set.range f) := by
rw [← MonoidHom.comap_bot, index_comap, relindex_bot_left]
rfl
#align subgroup.index_ker Subgroup.index_ker
#align add_subgroup.index_ker AddSubgroup.index_ker
@[to_additive]
theorem relindex_ker {H} [Group H] (f : G →* H) (K : Subgroup G) :
f.ker.relindex K = Nat.card (f '' K) := by
rw [← MonoidHom.comap_bot, relindex_comap, relindex_bot_left]
rfl
#align subgroup.relindex_ker Subgroup.relindex_ker
#align add_subgroup.relindex_ker AddSubgroup.relindex_ker
@[to_additive (attr := simp) card_mul_index]
theorem card_mul_index : Nat.card H * H.index = Nat.card G := by
rw [← relindex_bot_left, ← index_bot]
exact relindex_mul_index bot_le
#align subgroup.card_mul_index Subgroup.card_mul_index
#align add_subgroup.card_mul_index AddSubgroup.card_mul_index
@[to_additive]
theorem nat_card_dvd_of_injective {G H : Type*} [Group G] [Group H] (f : G →* H)
(hf : Function.Injective f) : Nat.card G ∣ Nat.card H := by
rw [Nat.card_congr (MonoidHom.ofInjective hf).toEquiv]
exact Dvd.intro f.range.index f.range.card_mul_index
#align subgroup.nat_card_dvd_of_injective Subgroup.nat_card_dvd_of_injective
#align add_subgroup.nat_card_dvd_of_injective AddSubgroup.nat_card_dvd_of_injective
@[to_additive]
theorem nat_card_dvd_of_le (hHK : H ≤ K) : Nat.card H ∣ Nat.card K :=
nat_card_dvd_of_injective (inclusion hHK) (inclusion_injective hHK)
#align subgroup.nat_card_dvd_of_le Subgroup.nat_card_dvd_of_le
#align add_subgroup.nat_card_dvd_of_le AddSubgroup.nat_card_dvd_of_le
@[to_additive]
theorem nat_card_dvd_of_surjective {G H : Type*} [Group G] [Group H] (f : G →* H)
(hf : Function.Surjective f) : Nat.card H ∣ Nat.card G := by
rw [← Nat.card_congr (QuotientGroup.quotientKerEquivOfSurjective f hf).toEquiv]
exact Dvd.intro_left (Nat.card f.ker) f.ker.card_mul_index
#align subgroup.nat_card_dvd_of_surjective Subgroup.nat_card_dvd_of_surjective
#align add_subgroup.nat_card_dvd_of_surjective AddSubgroup.nat_card_dvd_of_surjective
@[to_additive]
theorem card_dvd_of_surjective {G H : Type*} [Group G] [Group H] [Fintype G] [Fintype H]
(f : G →* H) (hf : Function.Surjective f) : Fintype.card H ∣ Fintype.card G := by
simp only [← Nat.card_eq_fintype_card, nat_card_dvd_of_surjective f hf]
#align subgroup.card_dvd_of_surjective Subgroup.card_dvd_of_surjective
#align add_subgroup.card_dvd_of_surjective AddSubgroup.card_dvd_of_surjective
@[to_additive]
theorem index_map {G' : Type*} [Group G'] (f : G →* G') :
(H.map f).index = (H ⊔ f.ker).index * f.range.index := by
rw [← comap_map_eq, index_comap, relindex_mul_index (H.map_le_range f)]
#align subgroup.index_map Subgroup.index_map
#align add_subgroup.index_map AddSubgroup.index_map
@[to_additive]
theorem index_map_dvd {G' : Type*} [Group G'] {f : G →* G'} (hf : Function.Surjective f) :
(H.map f).index ∣ H.index := by
rw [index_map, f.range_top_of_surjective hf, index_top, mul_one]
exact index_dvd_of_le le_sup_left
#align subgroup.index_map_dvd Subgroup.index_map_dvd
#align add_subgroup.index_map_dvd AddSubgroup.index_map_dvd
@[to_additive]
theorem dvd_index_map {G' : Type*} [Group G'] {f : G →* G'} (hf : f.ker ≤ H) :
H.index ∣ (H.map f).index := by
rw [index_map, sup_of_le_left hf]
apply dvd_mul_right
#align subgroup.dvd_index_map Subgroup.dvd_index_map
#align add_subgroup.dvd_index_map AddSubgroup.dvd_index_map
@[to_additive]
theorem index_map_eq {G' : Type*} [Group G'] {f : G →* G'} (hf1 : Function.Surjective f)
(hf2 : f.ker ≤ H) : (H.map f).index = H.index :=
Nat.dvd_antisymm (H.index_map_dvd hf1) (H.dvd_index_map hf2)
#align subgroup.index_map_eq Subgroup.index_map_eq
#align add_subgroup.index_map_eq AddSubgroup.index_map_eq
@[to_additive]
theorem index_eq_card [Fintype (G ⧸ H)] : H.index = Fintype.card (G ⧸ H) :=
Nat.card_eq_fintype_card
#align subgroup.index_eq_card Subgroup.index_eq_card
#align add_subgroup.index_eq_card AddSubgroup.index_eq_card
@[to_additive index_mul_card]
| Mathlib/GroupTheory/Index.lean | 362 | 365 | theorem index_mul_card [Fintype G] [hH : Fintype H] :
H.index * Fintype.card H = Fintype.card G := by |
rw [← relindex_bot_left_eq_card, ← index_bot_eq_card, mul_comm];
exact relindex_mul_index bot_le
|
/-
Copyright (c) 2018 Reid Barton. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Reid Barton, Scott Morrison
-/
import Mathlib.CategoryTheory.Opposites
#align_import category_theory.eq_to_hom from "leanprover-community/mathlib"@"dc6c365e751e34d100e80fe6e314c3c3e0fd2988"
/-!
# Morphisms from equations between objects.
When working categorically, sometimes one encounters an equation `h : X = Y` between objects.
Your initial aversion to this is natural and appropriate:
you're in for some trouble, and if there is another way to approach the problem that won't
rely on this equality, it may be worth pursuing.
You have two options:
1. Use the equality `h` as one normally would in Lean (e.g. using `rw` and `subst`).
This may immediately cause difficulties, because in category theory everything is dependently
typed, and equations between objects quickly lead to nasty goals with `eq.rec`.
2. Promote `h` to a morphism using `eqToHom h : X ⟶ Y`, or `eqToIso h : X ≅ Y`.
This file introduces various `simp` lemmas which in favourable circumstances
result in the various `eqToHom` morphisms to drop out at the appropriate moment!
-/
universe v₁ v₂ v₃ u₁ u₂ u₃
-- morphism levels before object levels. See note [CategoryTheory universes].
namespace CategoryTheory
open Opposite
variable {C : Type u₁} [Category.{v₁} C]
/-- An equality `X = Y` gives us a morphism `X ⟶ Y`.
It is typically better to use this, rather than rewriting by the equality then using `𝟙 _`
which usually leads to dependent type theory hell.
-/
def eqToHom {X Y : C} (p : X = Y) : X ⟶ Y := by rw [p]; exact 𝟙 _
#align category_theory.eq_to_hom CategoryTheory.eqToHom
@[simp]
theorem eqToHom_refl (X : C) (p : X = X) : eqToHom p = 𝟙 X :=
rfl
#align category_theory.eq_to_hom_refl CategoryTheory.eqToHom_refl
@[reassoc (attr := simp)]
| Mathlib/CategoryTheory/EqToHom.lean | 52 | 56 | theorem eqToHom_trans {X Y Z : C} (p : X = Y) (q : Y = Z) :
eqToHom p ≫ eqToHom q = eqToHom (p.trans q) := by |
cases p
cases q
simp
|
/-
Copyright (c) 2016 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad, Leonardo de Moura, Mario Carneiro, Johannes Hölzl
-/
import Mathlib.Algebra.CharZero.Defs
import Mathlib.Algebra.Group.Hom.Defs
import Mathlib.Algebra.Order.Monoid.Canonical.Defs
import Mathlib.Algebra.Order.Monoid.OrderDual
import Mathlib.Algebra.Order.ZeroLEOne
import Mathlib.Data.Nat.Cast.Defs
import Mathlib.Order.WithBot
#align_import algebra.order.monoid.with_top from "leanprover-community/mathlib"@"0111834459f5d7400215223ea95ae38a1265a907"
/-! # Adjoining top/bottom elements to ordered monoids.
-/
universe u v
variable {α : Type u} {β : Type v}
open Function
namespace WithTop
section One
variable [One α] {a : α}
@[to_additive]
instance one : One (WithTop α) :=
⟨(1 : α)⟩
#align with_top.has_one WithTop.one
#align with_top.has_zero WithTop.zero
@[to_additive (attr := simp, norm_cast)]
theorem coe_one : ((1 : α) : WithTop α) = 1 :=
rfl
#align with_top.coe_one WithTop.coe_one
#align with_top.coe_zero WithTop.coe_zero
@[to_additive (attr := simp, norm_cast)]
lemma coe_eq_one : (a : WithTop α) = 1 ↔ a = 1 := coe_eq_coe
#align with_top.coe_eq_one WithTop.coe_eq_one
#align with_top.coe_eq_zero WithTop.coe_eq_zero
@[to_additive (attr := simp, norm_cast)]
lemma one_eq_coe : 1 = (a : WithTop α) ↔ a = 1 := eq_comm.trans coe_eq_one
#align with_top.one_eq_coe WithTop.one_eq_coe
#align with_top.zero_eq_coe WithTop.zero_eq_coe
@[to_additive (attr := simp)] lemma top_ne_one : (⊤ : WithTop α) ≠ 1 := top_ne_coe
#align with_top.top_ne_one WithTop.top_ne_one
#align with_top.top_ne_zero WithTop.top_ne_zero
@[to_additive (attr := simp)] lemma one_ne_top : (1 : WithTop α) ≠ ⊤ := coe_ne_top
#align with_top.one_ne_top WithTop.one_ne_top
#align with_top.zero_ne_top WithTop.zero_ne_top
@[to_additive (attr := simp)]
theorem untop_one : (1 : WithTop α).untop coe_ne_top = 1 :=
rfl
#align with_top.untop_one WithTop.untop_one
#align with_top.untop_zero WithTop.untop_zero
@[to_additive (attr := simp)]
theorem untop_one' (d : α) : (1 : WithTop α).untop' d = 1 :=
rfl
#align with_top.untop_one' WithTop.untop_one'
#align with_top.untop_zero' WithTop.untop_zero'
@[to_additive (attr := simp, norm_cast) coe_nonneg]
theorem one_le_coe [LE α] {a : α} : 1 ≤ (a : WithTop α) ↔ 1 ≤ a :=
coe_le_coe
#align with_top.one_le_coe WithTop.one_le_coe
#align with_top.coe_nonneg WithTop.coe_nonneg
@[to_additive (attr := simp, norm_cast) coe_le_zero]
theorem coe_le_one [LE α] {a : α} : (a : WithTop α) ≤ 1 ↔ a ≤ 1 :=
coe_le_coe
#align with_top.coe_le_one WithTop.coe_le_one
#align with_top.coe_le_zero WithTop.coe_le_zero
@[to_additive (attr := simp, norm_cast) coe_pos]
theorem one_lt_coe [LT α] {a : α} : 1 < (a : WithTop α) ↔ 1 < a :=
coe_lt_coe
#align with_top.one_lt_coe WithTop.one_lt_coe
#align with_top.coe_pos WithTop.coe_pos
@[to_additive (attr := simp, norm_cast) coe_lt_zero]
theorem coe_lt_one [LT α] {a : α} : (a : WithTop α) < 1 ↔ a < 1 :=
coe_lt_coe
#align with_top.coe_lt_one WithTop.coe_lt_one
#align with_top.coe_lt_zero WithTop.coe_lt_zero
@[to_additive (attr := simp)]
protected theorem map_one {β} (f : α → β) : (1 : WithTop α).map f = (f 1 : WithTop β) :=
rfl
#align with_top.map_one WithTop.map_one
#align with_top.map_zero WithTop.map_zero
instance zeroLEOneClass [Zero α] [LE α] [ZeroLEOneClass α] : ZeroLEOneClass (WithTop α) :=
⟨coe_le_coe.2 zero_le_one⟩
end One
section Add
variable [Add α] {a b c d : WithTop α} {x y : α}
instance add : Add (WithTop α) :=
⟨Option.map₂ (· + ·)⟩
#align with_top.has_add WithTop.add
@[simp, norm_cast] lemma coe_add (a b : α) : ↑(a + b) = (a + b : WithTop α) := rfl
#align with_top.coe_add WithTop.coe_add
#noalign with_top.coe_bit0
#noalign with_top.coe_bit1
@[simp]
theorem top_add (a : WithTop α) : ⊤ + a = ⊤ :=
rfl
#align with_top.top_add WithTop.top_add
@[simp]
theorem add_top (a : WithTop α) : a + ⊤ = ⊤ := by cases a <;> rfl
#align with_top.add_top WithTop.add_top
@[simp]
theorem add_eq_top : a + b = ⊤ ↔ a = ⊤ ∨ b = ⊤ := by
match a, b with
| ⊤, _ => simp
| _, ⊤ => simp
| (a : α), (b : α) => simp only [← coe_add, coe_ne_top, or_false]
#align with_top.add_eq_top WithTop.add_eq_top
theorem add_ne_top : a + b ≠ ⊤ ↔ a ≠ ⊤ ∧ b ≠ ⊤ :=
add_eq_top.not.trans not_or
#align with_top.add_ne_top WithTop.add_ne_top
theorem add_lt_top [LT α] {a b : WithTop α} : a + b < ⊤ ↔ a < ⊤ ∧ b < ⊤ := by
simp_rw [WithTop.lt_top_iff_ne_top, add_ne_top]
#align with_top.add_lt_top WithTop.add_lt_top
theorem add_eq_coe :
∀ {a b : WithTop α} {c : α}, a + b = c ↔ ∃ a' b' : α, ↑a' = a ∧ ↑b' = b ∧ a' + b' = c
| ⊤, b, c => by simp
| some a, ⊤, c => by simp
| some a, some b, c => by norm_cast; simp
#align with_top.add_eq_coe WithTop.add_eq_coe
-- Porting note (#10618): simp can already prove this.
-- @[simp]
theorem add_coe_eq_top_iff {x : WithTop α} {y : α} : x + y = ⊤ ↔ x = ⊤ := by simp
#align with_top.add_coe_eq_top_iff WithTop.add_coe_eq_top_iff
-- Porting note (#10618): simp can already prove this.
-- @[simp]
theorem coe_add_eq_top_iff {y : WithTop α} : ↑x + y = ⊤ ↔ y = ⊤ := by simp
#align with_top.coe_add_eq_top_iff WithTop.coe_add_eq_top_iff
theorem add_right_cancel_iff [IsRightCancelAdd α] (ha : a ≠ ⊤) : b + a = c + a ↔ b = c := by
lift a to α using ha
obtain rfl | hb := eq_or_ne b ⊤
· rw [top_add, eq_comm, WithTop.add_coe_eq_top_iff, eq_comm]
lift b to α using hb
simp_rw [← WithTop.coe_add, eq_comm, WithTop.add_eq_coe, coe_eq_coe, exists_and_left,
exists_eq_left, add_left_inj, exists_eq_right, eq_comm]
theorem add_right_cancel [IsRightCancelAdd α] (ha : a ≠ ⊤) (h : b + a = c + a) : b = c :=
(WithTop.add_right_cancel_iff ha).1 h
theorem add_left_cancel_iff [IsLeftCancelAdd α] (ha : a ≠ ⊤) : a + b = a + c ↔ b = c := by
lift a to α using ha
obtain rfl | hb := eq_or_ne b ⊤
· rw [add_top, eq_comm, WithTop.coe_add_eq_top_iff, eq_comm]
lift b to α using hb
simp_rw [← WithTop.coe_add, eq_comm, WithTop.add_eq_coe, eq_comm, coe_eq_coe,
exists_and_left, exists_eq_left', add_right_inj, exists_eq_right']
theorem add_left_cancel [IsLeftCancelAdd α] (ha : a ≠ ⊤) (h : a + b = a + c) : b = c :=
(WithTop.add_left_cancel_iff ha).1 h
instance covariantClass_add_le [LE α] [CovariantClass α α (· + ·) (· ≤ ·)] :
CovariantClass (WithTop α) (WithTop α) (· + ·) (· ≤ ·) :=
⟨fun a b c h => by
cases a <;> cases c <;> try exact le_top
rcases le_coe_iff.1 h with ⟨b, rfl, _⟩
exact coe_le_coe.2 (add_le_add_left (coe_le_coe.1 h) _)⟩
#align with_top.covariant_class_add_le WithTop.covariantClass_add_le
instance covariantClass_swap_add_le [LE α] [CovariantClass α α (swap (· + ·)) (· ≤ ·)] :
CovariantClass (WithTop α) (WithTop α) (swap (· + ·)) (· ≤ ·) :=
⟨fun a b c h => by
cases a <;> cases c <;> try exact le_top
rcases le_coe_iff.1 h with ⟨b, rfl, _⟩
exact coe_le_coe.2 (add_le_add_right (coe_le_coe.1 h) _)⟩
#align with_top.covariant_class_swap_add_le WithTop.covariantClass_swap_add_le
instance contravariantClass_add_lt [LT α] [ContravariantClass α α (· + ·) (· < ·)] :
ContravariantClass (WithTop α) (WithTop α) (· + ·) (· < ·) :=
⟨fun a b c h => by
induction a; · exact (WithTop.not_top_lt _ h).elim
induction b; · exact (WithTop.not_top_lt _ h).elim
induction c
· exact coe_lt_top _
· exact coe_lt_coe.2 (lt_of_add_lt_add_left <| coe_lt_coe.1 h)⟩
#align with_top.contravariant_class_add_lt WithTop.contravariantClass_add_lt
instance contravariantClass_swap_add_lt [LT α] [ContravariantClass α α (swap (· + ·)) (· < ·)] :
ContravariantClass (WithTop α) (WithTop α) (swap (· + ·)) (· < ·) :=
⟨fun a b c h => by
cases a <;> cases b <;> try exact (WithTop.not_top_lt _ h).elim
cases c
· exact coe_lt_top _
· exact coe_lt_coe.2 (lt_of_add_lt_add_right <| coe_lt_coe.1 h)⟩
#align with_top.contravariant_class_swap_add_lt WithTop.contravariantClass_swap_add_lt
protected theorem le_of_add_le_add_left [LE α] [ContravariantClass α α (· + ·) (· ≤ ·)] (ha : a ≠ ⊤)
(h : a + b ≤ a + c) : b ≤ c := by
lift a to α using ha
induction c
· exact le_top
· induction b
· exact (not_top_le_coe _ h).elim
· simp only [← coe_add, coe_le_coe] at h ⊢
exact le_of_add_le_add_left h
#align with_top.le_of_add_le_add_left WithTop.le_of_add_le_add_left
protected theorem le_of_add_le_add_right [LE α] [ContravariantClass α α (swap (· + ·)) (· ≤ ·)]
(ha : a ≠ ⊤) (h : b + a ≤ c + a) : b ≤ c := by
lift a to α using ha
cases c
· exact le_top
· cases b
· exact (not_top_le_coe _ h).elim
· exact coe_le_coe.2 (le_of_add_le_add_right <| coe_le_coe.1 h)
#align with_top.le_of_add_le_add_right WithTop.le_of_add_le_add_right
protected theorem add_lt_add_left [LT α] [CovariantClass α α (· + ·) (· < ·)] (ha : a ≠ ⊤)
(h : b < c) : a + b < a + c := by
lift a to α using ha
rcases lt_iff_exists_coe.1 h with ⟨b, rfl, h'⟩
cases c
· exact coe_lt_top _
· exact coe_lt_coe.2 (add_lt_add_left (coe_lt_coe.1 h) _)
#align with_top.add_lt_add_left WithTop.add_lt_add_left
protected theorem add_lt_add_right [LT α] [CovariantClass α α (swap (· + ·)) (· < ·)] (ha : a ≠ ⊤)
(h : b < c) : b + a < c + a := by
lift a to α using ha
rcases lt_iff_exists_coe.1 h with ⟨b, rfl, h'⟩
cases c
· exact coe_lt_top _
· exact coe_lt_coe.2 (add_lt_add_right (coe_lt_coe.1 h) _)
#align with_top.add_lt_add_right WithTop.add_lt_add_right
protected theorem add_le_add_iff_left [LE α] [CovariantClass α α (· + ·) (· ≤ ·)]
[ContravariantClass α α (· + ·) (· ≤ ·)] (ha : a ≠ ⊤) : a + b ≤ a + c ↔ b ≤ c :=
⟨WithTop.le_of_add_le_add_left ha, fun h => add_le_add_left h a⟩
#align with_top.add_le_add_iff_left WithTop.add_le_add_iff_left
protected theorem add_le_add_iff_right [LE α] [CovariantClass α α (swap (· + ·)) (· ≤ ·)]
[ContravariantClass α α (swap (· + ·)) (· ≤ ·)] (ha : a ≠ ⊤) : b + a ≤ c + a ↔ b ≤ c :=
⟨WithTop.le_of_add_le_add_right ha, fun h => add_le_add_right h a⟩
#align with_top.add_le_add_iff_right WithTop.add_le_add_iff_right
protected theorem add_lt_add_iff_left [LT α] [CovariantClass α α (· + ·) (· < ·)]
[ContravariantClass α α (· + ·) (· < ·)] (ha : a ≠ ⊤) : a + b < a + c ↔ b < c :=
⟨lt_of_add_lt_add_left, WithTop.add_lt_add_left ha⟩
#align with_top.add_lt_add_iff_left WithTop.add_lt_add_iff_left
protected theorem add_lt_add_iff_right [LT α] [CovariantClass α α (swap (· + ·)) (· < ·)]
[ContravariantClass α α (swap (· + ·)) (· < ·)] (ha : a ≠ ⊤) : b + a < c + a ↔ b < c :=
⟨lt_of_add_lt_add_right, WithTop.add_lt_add_right ha⟩
#align with_top.add_lt_add_iff_right WithTop.add_lt_add_iff_right
protected theorem add_lt_add_of_le_of_lt [Preorder α] [CovariantClass α α (· + ·) (· < ·)]
[CovariantClass α α (swap (· + ·)) (· ≤ ·)] (ha : a ≠ ⊤) (hab : a ≤ b) (hcd : c < d) :
a + c < b + d :=
(WithTop.add_lt_add_left ha hcd).trans_le <| add_le_add_right hab _
#align with_top.add_lt_add_of_le_of_lt WithTop.add_lt_add_of_le_of_lt
protected theorem add_lt_add_of_lt_of_le [Preorder α] [CovariantClass α α (· + ·) (· ≤ ·)]
[CovariantClass α α (swap (· + ·)) (· < ·)] (hc : c ≠ ⊤) (hab : a < b) (hcd : c ≤ d) :
a + c < b + d :=
(WithTop.add_lt_add_right hc hab).trans_le <| add_le_add_left hcd _
#align with_top.add_lt_add_of_lt_of_le WithTop.add_lt_add_of_lt_of_le
-- There is no `WithTop.map_mul_of_mulHom`, since `WithTop` does not have a multiplication.
@[simp]
protected theorem map_add {F} [Add β] [FunLike F α β] [AddHomClass F α β]
(f : F) (a b : WithTop α) :
(a + b).map f = a.map f + b.map f := by
induction a
· exact (top_add _).symm
· induction b
· exact (add_top _).symm
· rw [map_coe, map_coe, ← coe_add, ← coe_add, ← map_add]
rfl
#align with_top.map_add WithTop.map_add
end Add
instance addSemigroup [AddSemigroup α] : AddSemigroup (WithTop α) :=
{ WithTop.add with
add_assoc := fun _ _ _ => Option.map₂_assoc add_assoc }
instance addCommSemigroup [AddCommSemigroup α] : AddCommSemigroup (WithTop α) :=
{ WithTop.addSemigroup with
add_comm := fun _ _ => Option.map₂_comm add_comm }
instance addZeroClass [AddZeroClass α] : AddZeroClass (WithTop α) :=
{ WithTop.zero, WithTop.add with
zero_add := Option.map₂_left_identity zero_add
add_zero := Option.map₂_right_identity add_zero }
section AddMonoid
variable [AddMonoid α]
instance addMonoid : AddMonoid (WithTop α) where
__ := WithTop.addSemigroup
__ := WithTop.addZeroClass
nsmul n a := match a, n with
| (a : α), n => ↑(n • a)
| ⊤, 0 => 0
| ⊤, _n + 1 => ⊤
nsmul_zero a := by cases a <;> simp [zero_nsmul]
nsmul_succ n a := by cases a <;> cases n <;> simp [succ_nsmul, coe_add]
@[simp, norm_cast] lemma coe_nsmul (a : α) (n : ℕ) : ↑(n • a) = n • (a : WithTop α) := rfl
/-- Coercion from `α` to `WithTop α` as an `AddMonoidHom`. -/
def addHom : α →+ WithTop α where
toFun := WithTop.some
map_zero' := rfl
map_add' _ _ := rfl
#align with_top.coe_add_hom WithTop.addHom
@[simp, norm_cast] lemma coe_addHom : ⇑(addHom : α →+ WithTop α) = WithTop.some := rfl
#align with_top.coe_coe_add_hom WithTop.coe_addHom
end AddMonoid
instance addCommMonoid [AddCommMonoid α] : AddCommMonoid (WithTop α) :=
{ WithTop.addMonoid, WithTop.addCommSemigroup with }
section AddMonoidWithOne
variable [AddMonoidWithOne α]
instance addMonoidWithOne : AddMonoidWithOne (WithTop α) :=
{ WithTop.one, WithTop.addMonoid with
natCast := fun n => ↑(n : α),
natCast_zero := by
simp only -- Porting note: Had to add this...?
rw [Nat.cast_zero, WithTop.coe_zero],
natCast_succ := fun n => by
simp only -- Porting note: Had to add this...?
rw [Nat.cast_add_one, WithTop.coe_add, WithTop.coe_one] }
@[simp, norm_cast] lemma coe_natCast (n : ℕ) : ((n : α) : WithTop α) = n := rfl
#align with_top.coe_nat WithTop.coe_natCast
@[simp] lemma natCast_ne_top (n : ℕ) : (n : WithTop α) ≠ ⊤ := coe_ne_top
#align with_top.nat_ne_top WithTop.natCast_ne_top
@[simp] lemma top_ne_natCast (n : ℕ) : (⊤ : WithTop α) ≠ n := top_ne_coe
#align with_top.top_ne_nat WithTop.top_ne_natCast
-- 2024-04-05
@[deprecated] alias coe_nat := coe_natCast
@[deprecated] alias nat_ne_top := natCast_ne_top
@[deprecated] alias top_ne_nat := top_ne_natCast
end AddMonoidWithOne
instance charZero [AddMonoidWithOne α] [CharZero α] : CharZero (WithTop α) :=
{ cast_injective := Function.Injective.comp (f := Nat.cast (R := α))
(fun _ _ => WithTop.coe_eq_coe.1) Nat.cast_injective}
instance addCommMonoidWithOne [AddCommMonoidWithOne α] : AddCommMonoidWithOne (WithTop α) :=
{ WithTop.addMonoidWithOne, WithTop.addCommMonoid with }
instance orderedAddCommMonoid [OrderedAddCommMonoid α] : OrderedAddCommMonoid (WithTop α) where
add_le_add_left _ _ := add_le_add_left
instance linearOrderedAddCommMonoidWithTop [LinearOrderedAddCommMonoid α] :
LinearOrderedAddCommMonoidWithTop (WithTop α) :=
{ WithTop.orderTop, WithTop.linearOrder, WithTop.orderedAddCommMonoid with
top_add' := WithTop.top_add }
instance existsAddOfLE [LE α] [Add α] [ExistsAddOfLE α] : ExistsAddOfLE (WithTop α) :=
⟨fun {a} {b} =>
match a, b with
| ⊤, ⊤ => by simp
| (a : α), ⊤ => fun _ => ⟨⊤, rfl⟩
| (a : α), (b : α) => fun h => by
obtain ⟨c, rfl⟩ := exists_add_of_le (WithTop.coe_le_coe.1 h)
exact ⟨c, rfl⟩
| ⊤, (b : α) => fun h => (not_top_le_coe _ h).elim⟩
instance canonicallyOrderedAddCommMonoid [CanonicallyOrderedAddCommMonoid α] :
CanonicallyOrderedAddCommMonoid (WithTop α) :=
{ WithTop.orderBot, WithTop.orderedAddCommMonoid, WithTop.existsAddOfLE with
le_self_add := fun a b =>
match a, b with
| ⊤, ⊤ => le_rfl
| (a : α), ⊤ => le_top
| (a : α), (b : α) => WithTop.coe_le_coe.2 le_self_add
| ⊤, (b : α) => le_rfl }
instance [CanonicallyLinearOrderedAddCommMonoid α] :
CanonicallyLinearOrderedAddCommMonoid (WithTop α) :=
{ WithTop.canonicallyOrderedAddCommMonoid, WithTop.linearOrder with }
@[simp]
theorem zero_lt_top [OrderedAddCommMonoid α] : (0 : WithTop α) < ⊤ :=
coe_lt_top 0
#align with_top.zero_lt_top WithTop.zero_lt_top
-- Porting note (#10618): simp can already prove this.
-- @[simp]
@[norm_cast]
theorem zero_lt_coe [OrderedAddCommMonoid α] (a : α) : (0 : WithTop α) < a ↔ 0 < a :=
coe_lt_coe
#align with_top.zero_lt_coe WithTop.zero_lt_coe
/-- A version of `WithTop.map` for `OneHom`s. -/
@[to_additive (attr := simps (config := .asFn))
"A version of `WithTop.map` for `ZeroHom`s"]
protected def _root_.OneHom.withTopMap {M N : Type*} [One M] [One N] (f : OneHom M N) :
OneHom (WithTop M) (WithTop N) where
toFun := WithTop.map f
map_one' := by rw [WithTop.map_one, map_one, coe_one]
#align one_hom.with_top_map OneHom.withTopMap
#align zero_hom.with_top_map ZeroHom.withTopMap
#align one_hom.with_top_map_apply OneHom.withTopMap_apply
/-- A version of `WithTop.map` for `AddHom`s. -/
@[simps (config := .asFn)]
protected def _root_.AddHom.withTopMap {M N : Type*} [Add M] [Add N] (f : AddHom M N) :
AddHom (WithTop M) (WithTop N) where
toFun := WithTop.map f
map_add' := WithTop.map_add f
#align add_hom.with_top_map AddHom.withTopMap
#align add_hom.with_top_map_apply AddHom.withTopMap_apply
/-- A version of `WithTop.map` for `AddMonoidHom`s. -/
@[simps (config := .asFn)]
protected def _root_.AddMonoidHom.withTopMap {M N : Type*} [AddZeroClass M] [AddZeroClass N]
(f : M →+ N) : WithTop M →+ WithTop N :=
{ ZeroHom.withTopMap f.toZeroHom, AddHom.withTopMap f.toAddHom with toFun := WithTop.map f }
#align add_monoid_hom.with_top_map AddMonoidHom.withTopMap
#align add_monoid_hom.with_top_map_apply AddMonoidHom.withTopMap_apply
end WithTop
namespace WithBot
section One
variable [One α] {a : α}
@[to_additive] instance one : One (WithBot α) := WithTop.one
@[to_additive (attr := simp, norm_cast)] lemma coe_one : ((1 : α) : WithBot α) = 1 := rfl
#align with_bot.coe_one WithBot.coe_one
#align with_bot.coe_zero WithBot.coe_zero
@[to_additive (attr := simp, norm_cast)]
lemma coe_eq_one : (a : WithBot α) = 1 ↔ a = 1 := coe_eq_coe
#align with_bot.coe_eq_one WithBot.coe_eq_one
#align with_bot.coe_eq_zero WithBot.coe_eq_zero
@[to_additive (attr := simp, norm_cast)]
lemma one_eq_coe : 1 = (a : WithBot α) ↔ a = 1 := eq_comm.trans coe_eq_one
@[to_additive (attr := simp)] lemma bot_ne_one : (⊥ : WithBot α) ≠ 1 := bot_ne_coe
@[to_additive (attr := simp)] lemma one_ne_bot : (1 : WithBot α) ≠ ⊥ := coe_ne_bot
@[to_additive (attr := simp)]
theorem unbot_one : (1 : WithBot α).unbot coe_ne_bot = 1 :=
rfl
#align with_bot.unbot_one WithBot.unbot_one
#align with_bot.unbot_zero WithBot.unbot_zero
@[to_additive (attr := simp)]
theorem unbot_one' (d : α) : (1 : WithBot α).unbot' d = 1 :=
rfl
#align with_bot.unbot_one' WithBot.unbot_one'
#align with_bot.unbot_zero' WithBot.unbot_zero'
@[to_additive (attr := simp, norm_cast) coe_nonneg]
theorem one_le_coe [LE α] : 1 ≤ (a : WithBot α) ↔ 1 ≤ a := coe_le_coe
#align with_bot.one_le_coe WithBot.one_le_coe
#align with_bot.coe_nonneg WithBot.coe_nonneg
@[to_additive (attr := simp, norm_cast) coe_le_zero]
theorem coe_le_one [LE α] : (a : WithBot α) ≤ 1 ↔ a ≤ 1 := coe_le_coe
#align with_bot.coe_le_one WithBot.coe_le_one
#align with_bot.coe_le_zero WithBot.coe_le_zero
@[to_additive (attr := simp, norm_cast) coe_pos]
theorem one_lt_coe [LT α] : 1 < (a : WithBot α) ↔ 1 < a := coe_lt_coe
#align with_bot.one_lt_coe WithBot.one_lt_coe
#align with_bot.coe_pos WithBot.coe_pos
@[to_additive (attr := simp, norm_cast) coe_lt_zero]
theorem coe_lt_one [LT α] : (a : WithBot α) < 1 ↔ a < 1 := coe_lt_coe
#align with_bot.coe_lt_one WithBot.coe_lt_one
#align with_bot.coe_lt_zero WithBot.coe_lt_zero
@[to_additive (attr := simp)]
protected theorem map_one {β} (f : α → β) : (1 : WithBot α).map f = (f 1 : WithBot β) :=
rfl
#align with_bot.map_one WithBot.map_one
#align with_bot.map_zero WithBot.map_zero
instance zeroLEOneClass [Zero α] [LE α] [ZeroLEOneClass α] : ZeroLEOneClass (WithBot α) :=
⟨coe_le_coe.2 zero_le_one⟩
end One
instance add [Add α] : Add (WithBot α) :=
WithTop.add
instance AddSemigroup [AddSemigroup α] : AddSemigroup (WithBot α) :=
WithTop.addSemigroup
instance addCommSemigroup [AddCommSemigroup α] : AddCommSemigroup (WithBot α) :=
WithTop.addCommSemigroup
instance addZeroClass [AddZeroClass α] : AddZeroClass (WithBot α) :=
WithTop.addZeroClass
section AddMonoid
variable [AddMonoid α]
instance addMonoid : AddMonoid (WithBot α) := WithTop.addMonoid
/-- Coercion from `α` to `WithBot α` as an `AddMonoidHom`. -/
def addHom : α →+ WithBot α where
toFun := WithTop.some
map_zero' := rfl
map_add' _ _ := rfl
@[simp, norm_cast] lemma coe_addHom : ⇑(addHom : α →+ WithBot α) = WithBot.some := rfl
@[simp, norm_cast]
lemma coe_nsmul (a : α) (n : ℕ) : ↑(n • a) = n • (a : WithBot α) :=
(addHom : α →+ WithBot α).map_nsmul _ _
#align with_bot.coe_nsmul WithBot.coe_nsmul
end AddMonoid
instance addCommMonoid [AddCommMonoid α] : AddCommMonoid (WithBot α) :=
WithTop.addCommMonoid
section AddMonoidWithOne
variable [AddMonoidWithOne α]
instance addMonoidWithOne : AddMonoidWithOne (WithBot α) := WithTop.addMonoidWithOne
@[norm_cast] lemma coe_natCast (n : ℕ) : ((n : α) : WithBot α) = n := rfl
#align with_bot.coe_nat WithBot.coe_natCast
@[simp] lemma natCast_ne_bot (n : ℕ) : (n : WithBot α) ≠ ⊥ := coe_ne_bot
#align with_bot.nat_ne_bot WithBot.natCast_ne_bot
@[simp] lemma bot_ne_natCast (n : ℕ) : (⊥ : WithBot α) ≠ n := bot_ne_coe
#align with_bot.bot_ne_nat WithBot.bot_ne_natCast
-- 2024-04-05
@[deprecated] alias coe_nat := coe_natCast
@[deprecated] alias nat_ne_bot := natCast_ne_bot
@[deprecated] alias bot_ne_nat := bot_ne_natCast
end AddMonoidWithOne
instance charZero [AddMonoidWithOne α] [CharZero α] : CharZero (WithBot α) :=
WithTop.charZero
instance addCommMonoidWithOne [AddCommMonoidWithOne α] : AddCommMonoidWithOne (WithBot α) :=
WithTop.addCommMonoidWithOne
section Add
variable [Add α] {a b c d : WithBot α} {x y : α}
@[simp, norm_cast]
theorem coe_add (a b : α) : ((a + b : α) : WithBot α) = a + b :=
rfl
#align with_bot.coe_add WithBot.coe_add
#noalign with_bot.coe_bit0
#noalign with_bot.coe_bit1
@[simp]
theorem bot_add (a : WithBot α) : ⊥ + a = ⊥ :=
rfl
#align with_bot.bot_add WithBot.bot_add
@[simp]
| Mathlib/Algebra/Order/Monoid/WithTop.lean | 604 | 604 | theorem add_bot (a : WithBot α) : a + ⊥ = ⊥ := by | cases a <;> rfl
|
/-
Copyright (c) 2021 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov
-/
import Mathlib.MeasureTheory.Measure.Lebesgue.Complex
import Mathlib.MeasureTheory.Integral.DivergenceTheorem
import Mathlib.MeasureTheory.Integral.CircleIntegral
import Mathlib.Analysis.Calculus.Dslope
import Mathlib.Analysis.Analytic.Basic
import Mathlib.Analysis.Complex.ReImTopology
import Mathlib.Analysis.Calculus.DiffContOnCl
import Mathlib.Analysis.Calculus.FDeriv.Analytic
import Mathlib.Data.Real.Cardinality
#align_import analysis.complex.cauchy_integral from "leanprover-community/mathlib"@"fd5edc43dc4f10b85abfe544b88f82cf13c5f844"
/-!
# Cauchy integral formula
In this file we prove the Cauchy-Goursat theorem and the Cauchy integral formula for integrals over
circles. Most results are formulated for a function `f : ℂ → E` that takes values in a complex
Banach space with second countable topology.
## Main statements
In the following theorems, if the name ends with `off_countable`, then the actual theorem assumes
differentiability at all but countably many points of the set mentioned below.
* `Complex.integral_boundary_rect_of_hasFDerivAt_real_off_countable`: If a function
`f : ℂ → E` is continuous on a closed rectangle and *real* differentiable on its interior, then
its integral over the boundary of this rectangle is equal to the integral of
`I • f' (x + y * I) 1 - f' (x + y * I) I` over the rectangle, where `f' z w : E` is the derivative
of `f` at `z` in the direction `w` and `I = Complex.I` is the imaginary unit.
* `Complex.integral_boundary_rect_eq_zero_of_differentiable_on_off_countable`: If a function
`f : ℂ → E` is continuous on a closed rectangle and is *complex* differentiable on its interior,
then its integral over the boundary of this rectangle is equal to zero.
* `Complex.circleIntegral_sub_center_inv_smul_eq_of_differentiable_on_annulus_off_countable`: If a
function `f : ℂ → E` is continuous on a closed annulus `{z | r ≤ |z - c| ≤ R}` and is complex
differentiable on its interior `{z | r < |z - c| < R}`, then the integrals of `(z - c)⁻¹ • f z`
over the outer boundary and over the inner boundary are equal.
* `Complex.circleIntegral_sub_center_inv_smul_of_differentiable_on_off_countable_of_tendsto`,
`Complex.circleIntegral_sub_center_inv_smul_of_differentiable_on_off_countable`:
If a function `f : ℂ → E` is continuous on a punctured closed disc `{z | |z - c| ≤ R ∧ z ≠ c}`, is
complex differentiable on the corresponding punctured open disc, and tends to `y` as `z → c`,
`z ≠ c`, then the integral of `(z - c)⁻¹ • f z` over the circle `|z - c| = R` is equal to
`2πiy`. In particular, if `f` is continuous on the whole closed disc and is complex differentiable
on the corresponding open disc, then this integral is equal to `2πif(c)`.
* `Complex.circleIntegral_sub_inv_smul_of_differentiable_on_off_countable`,
`Complex.two_pi_I_inv_smul_circleIntegral_sub_inv_smul_of_differentiable_on_off_countable`
**Cauchy integral formula**: if `f : ℂ → E` is continuous on a closed disc of radius `R` and is
complex differentiable on the corresponding open disc, then for any `w` in the corresponding open
disc the integral of `(z - w)⁻¹ • f z` over the boundary of the disc is equal to `2πif(w)`.
Two versions of the lemma put the multiplier `2πi` at the different sides of the equality.
* `Complex.hasFPowerSeriesOnBall_of_differentiable_off_countable`: If `f : ℂ → E` is continuous
on a closed disc of positive radius and is complex differentiable on the corresponding open disc,
then it is analytic on the corresponding open disc, and the coefficients of the power series are
given by Cauchy integral formulas.
* `DifferentiableOn.hasFPowerSeriesOnBall`: If `f : ℂ → E` is complex differentiable on a
closed disc of positive radius, then it is analytic on the corresponding open disc, and the
coefficients of the power series are given by Cauchy integral formulas.
* `DifferentiableOn.analyticAt`, `Differentiable.analyticAt`: If `f : ℂ → E` is differentiable
on a neighborhood of a point, then it is analytic at this point. In particular, if `f : ℂ → E`
is differentiable on the whole `ℂ`, then it is analytic at every point `z : ℂ`.
* `Differentiable.hasFPowerSeriesOnBall`: If `f : ℂ → E` is differentiable everywhere then the
`cauchyPowerSeries f z R` is a formal power series representing `f` at `z` with infinite
radius of convergence (this holds for any choice of `0 < R`).
## Implementation details
The proof of the Cauchy integral formula in this file is based on a very general version of the
divergence theorem, see `MeasureTheory.integral_divergence_of_hasFDerivWithinAt_off_countable`
(a version for functions defined on `Fin (n + 1) → ℝ`),
`MeasureTheory.integral_divergence_prod_Icc_of_hasFDerivWithinAt_off_countable_of_le`, and
`MeasureTheory.integral2_divergence_prod_of_hasFDerivWithinAt_off_countable` (versions for
functions defined on `ℝ × ℝ`).
Usually, the divergence theorem is formulated for a $C^1$ smooth function. The theorems formulated
above deal with a function that is
* continuous on a closed box/rectangle;
* differentiable at all but countably many points of its interior;
* have divergence integrable over the closed box/rectangle.
First, we reformulate the theorem for a *real*-differentiable map `ℂ → E`, and relate the integral
of `f` over the boundary of a rectangle in `ℂ` to the integral of the derivative
$\frac{\partial f}{\partial \bar z}$ over the interior of this box. In particular, for a *complex*
differentiable function, the latter derivative is zero, hence the integral over the boundary of a
rectangle is zero. Thus we get the Cauchy-Goursat theorem for a rectangle in `ℂ`.
Next, we apply this theorem to the function $F(z)=f(c+e^{z})$ on the rectangle
$[\ln r, \ln R]\times [0, 2\pi]$ to prove that
$$
\oint_{|z-c|=r}\frac{f(z)\,dz}{z-c}=\oint_{|z-c|=R}\frac{f(z)\,dz}{z-c}
$$
provided that `f` is continuous on the closed annulus `r ≤ |z - c| ≤ R` and is complex
differentiable on its interior `r < |z - c| < R` (possibly, at all but countably many points).
Here and below, we write $\frac{f(z)}{z-c}$ in the documentation while the actual lemmas use
`(z - c)⁻¹ • f z` because `f z` belongs to some Banach space over `ℂ` and `f z / (z - c)` is
undefined.
Taking the limit of this equality as `r` tends to `𝓝[>] 0`, we prove
$$
\oint_{|z-c|=R}\frac{f(z)\,dz}{z-c}=2\pi if(c)
$$
provided that `f` is continuous on the closed disc `|z - c| ≤ R` and is differentiable at all but
countably many points of its interior. This is the Cauchy integral formula for the center of a
circle. In particular, if we apply this function to `F z = (z - c) • f z`, then we get
$$
\oint_{|z-c|=R} f(z)\,dz=0.
$$
In order to deduce the Cauchy integral formula for any point `w`, `|w - c| < R`, we consider the
slope function `g : ℂ → E` given by `g z = (z - w)⁻¹ • (f z - f w)` if `z ≠ w` and `g w = f' w`.
This function satisfies assumptions of the previous theorem, so we have
$$
\oint_{|z-c|=R} \frac{f(z)\,dz}{z-w}=\oint_{|z-c|=R} \frac{f(w)\,dz}{z-w}=
\left(\oint_{|z-c|=R} \frac{dz}{z-w}\right)f(w).
$$
The latter integral was computed in `circleIntegral.integral_sub_inv_of_mem_ball` and is equal to
`2 * π * Complex.I`.
There is one more step in the actual proof. Since we allow `f` to be non-differentiable on a
countable set `s`, we cannot immediately claim that `g` is continuous at `w` if `w ∈ s`. So, we use
the proof outlined in the previous paragraph for `w ∉ s` (see
`Complex.circleIntegral_sub_inv_smul_of_differentiable_on_off_countable_aux`), then use continuity
of both sides of the formula and density of `sᶜ` to prove the formula for all points of the open
ball, see `Complex.circleIntegral_sub_inv_smul_of_differentiable_on_off_countable`.
Finally, we use the properties of the Cauchy integrals established elsewhere (see
`hasFPowerSeriesOn_cauchy_integral`) and Cauchy integral formula to prove that the original
function is analytic on the open ball.
## Tags
Cauchy-Goursat theorem, Cauchy integral formula
-/
open TopologicalSpace Set MeasureTheory intervalIntegral Metric Filter Function
open scoped Interval Real NNReal ENNReal Topology
noncomputable section
universe u
variable {E : Type u} [NormedAddCommGroup E] [NormedSpace ℂ E] [CompleteSpace E]
namespace Complex
/-- Suppose that a function `f : ℂ → E` is continuous on a closed rectangle with opposite corners at
`z w : ℂ`, is *real* differentiable at all but countably many points of the corresponding open
rectangle, and $\frac{\partial f}{\partial \bar z}$ is integrable on this rectangle. Then the
integral of `f` over the boundary of the rectangle is equal to the integral of
$2i\frac{\partial f}{\partial \bar z}=i\frac{\partial f}{\partial x}-\frac{\partial f}{\partial y}$
over the rectangle. -/
| Mathlib/Analysis/Complex/CauchyIntegral.lean | 166 | 203 | theorem integral_boundary_rect_of_hasFDerivAt_real_off_countable (f : ℂ → E) (f' : ℂ → ℂ →L[ℝ] E)
(z w : ℂ) (s : Set ℂ) (hs : s.Countable)
(Hc : ContinuousOn f ([[z.re, w.re]] ×ℂ [[z.im, w.im]]))
(Hd : ∀ x ∈ Ioo (min z.re w.re) (max z.re w.re) ×ℂ Ioo (min z.im w.im) (max z.im w.im) \ s,
HasFDerivAt f (f' x) x)
(Hi : IntegrableOn (fun z => I • f' z 1 - f' z I) ([[z.re, w.re]] ×ℂ [[z.im, w.im]])) :
(∫ x : ℝ in z.re..w.re, f (x + z.im * I)) - (∫ x : ℝ in z.re..w.re, f (x + w.im * I)) +
I • (∫ y : ℝ in z.im..w.im, f (re w + y * I)) -
I • ∫ y : ℝ in z.im..w.im, f (re z + y * I) =
∫ x : ℝ in z.re..w.re, ∫ y : ℝ in z.im..w.im, I • f' (x + y * I) 1 - f' (x + y * I) I := by |
set e : (ℝ × ℝ) ≃L[ℝ] ℂ := equivRealProdCLM.symm
have he : ∀ x y : ℝ, ↑x + ↑y * I = e (x, y) := fun x y => (mk_eq_add_mul_I x y).symm
have he₁ : e (1, 0) = 1 := rfl; have he₂ : e (0, 1) = I := rfl
simp only [he] at *
set F : ℝ × ℝ → E := f ∘ e
set F' : ℝ × ℝ → ℝ × ℝ →L[ℝ] E := fun p => (f' (e p)).comp (e : ℝ × ℝ →L[ℝ] ℂ)
have hF' : ∀ p : ℝ × ℝ, (-(I • F' p)) (1, 0) + F' p (0, 1) = -(I • f' (e p) 1 - f' (e p) I) := by
rintro ⟨x, y⟩
simp only [F', ContinuousLinearMap.neg_apply, ContinuousLinearMap.smul_apply,
ContinuousLinearMap.comp_apply, ContinuousLinearEquiv.coe_coe, he₁, he₂, neg_add_eq_sub,
neg_sub]
set R : Set (ℝ × ℝ) := [[z.re, w.re]] ×ˢ [[w.im, z.im]]
set t : Set (ℝ × ℝ) := e ⁻¹' s
rw [uIcc_comm z.im] at Hc Hi; rw [min_comm z.im, max_comm z.im] at Hd
have hR : e ⁻¹' ([[z.re, w.re]] ×ℂ [[w.im, z.im]]) = R := rfl
have htc : ContinuousOn F R := Hc.comp e.continuousOn hR.ge
have htd :
∀ p ∈ Ioo (min z.re w.re) (max z.re w.re) ×ˢ Ioo (min w.im z.im) (max w.im z.im) \ t,
HasFDerivAt F (F' p) p :=
fun p hp => (Hd (e p) hp).comp p e.hasFDerivAt
simp_rw [← intervalIntegral.integral_smul, intervalIntegral.integral_symm w.im z.im, ←
intervalIntegral.integral_neg, ← hF']
refine (integral2_divergence_prod_of_hasFDerivWithinAt_off_countable (fun p => -(I • F p)) F
(fun p => -(I • F' p)) F' z.re w.im w.re z.im t (hs.preimage e.injective)
(htc.const_smul _).neg htc (fun p hp => ((htd p hp).const_smul I).neg) htd ?_).symm
rw [← (volume_preserving_equiv_real_prod.symm _).integrableOn_comp_preimage
(MeasurableEquiv.measurableEmbedding _)] at Hi
simpa only [hF'] using Hi.neg
|
/-
Copyright (c) 2021 Aaron Anderson, Jesse Michael Han, Floris van Doorn. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Aaron Anderson, Jesse Michael Han, Floris van Doorn
-/
import Mathlib.Data.Fin.VecNotation
import Mathlib.SetTheory.Cardinal.Basic
#align_import model_theory.basic from "leanprover-community/mathlib"@"369525b73f229ccd76a6ec0e0e0bf2be57599768"
/-!
# Basics on First-Order Structures
This file defines first-order languages and structures in the style of the
[Flypitch project](https://flypitch.github.io/), as well as several important maps between
structures.
## Main Definitions
* A `FirstOrder.Language` defines a language as a pair of functions from the natural numbers to
`Type l`. One sends `n` to the type of `n`-ary functions, and the other sends `n` to the type of
`n`-ary relations.
* A `FirstOrder.Language.Structure` interprets the symbols of a given `FirstOrder.Language` in the
context of a given type.
* A `FirstOrder.Language.Hom`, denoted `M →[L] N`, is a map from the `L`-structure `M` to the
`L`-structure `N` that commutes with the interpretations of functions, and which preserves the
interpretations of relations (although only in the forward direction).
* A `FirstOrder.Language.Embedding`, denoted `M ↪[L] N`, is an embedding from the `L`-structure `M`
to the `L`-structure `N` that commutes with the interpretations of functions, and which preserves
the interpretations of relations in both directions.
* A `FirstOrder.Language.Equiv`, denoted `M ≃[L] N`, is an equivalence from the `L`-structure `M`
to the `L`-structure `N` that commutes with the interpretations of functions, and which preserves
the interpretations of relations in both directions.
## References
For the Flypitch project:
- [J. Han, F. van Doorn, *A formal proof of the independence of the continuum hypothesis*]
[flypitch_cpp]
- [J. Han, F. van Doorn, *A formalization of forcing and the unprovability of
the continuum hypothesis*][flypitch_itp]
-/
set_option autoImplicit true
universe u v u' v' w w'
open Cardinal
open Cardinal
namespace FirstOrder
/-! ### Languages and Structures -/
-- intended to be used with explicit universe parameters
/-- A first-order language consists of a type of functions of every natural-number arity and a
type of relations of every natural-number arity. -/
@[nolint checkUnivs]
structure Language where
/-- For every arity, a `Type*` of functions of that arity -/
Functions : ℕ → Type u
/-- For every arity, a `Type*` of relations of that arity -/
Relations : ℕ → Type v
#align first_order.language FirstOrder.Language
/-- Used to define `FirstOrder.Language₂`. -/
--@[simp]
def Sequence₂ (a₀ a₁ a₂ : Type u) : ℕ → Type u
| 0 => a₀
| 1 => a₁
| 2 => a₂
| _ => PEmpty
#align first_order.sequence₂ FirstOrder.Sequence₂
namespace Sequence₂
variable (a₀ a₁ a₂ : Type u)
instance inhabited₀ [h : Inhabited a₀] : Inhabited (Sequence₂ a₀ a₁ a₂ 0) :=
h
#align first_order.sequence₂.inhabited₀ FirstOrder.Sequence₂.inhabited₀
instance inhabited₁ [h : Inhabited a₁] : Inhabited (Sequence₂ a₀ a₁ a₂ 1) :=
h
#align first_order.sequence₂.inhabited₁ FirstOrder.Sequence₂.inhabited₁
instance inhabited₂ [h : Inhabited a₂] : Inhabited (Sequence₂ a₀ a₁ a₂ 2) :=
h
#align first_order.sequence₂.inhabited₂ FirstOrder.Sequence₂.inhabited₂
instance {n : ℕ} : IsEmpty (Sequence₂ a₀ a₁ a₂ (n + 3)) := inferInstanceAs (IsEmpty PEmpty)
@[simp]
theorem lift_mk {i : ℕ} :
Cardinal.lift.{v,u} #(Sequence₂ a₀ a₁ a₂ i)
= #(Sequence₂ (ULift.{v,u} a₀) (ULift.{v,u} a₁) (ULift.{v,u} a₂) i) := by
rcases i with (_ | _ | _ | i) <;>
simp only [Sequence₂, mk_uLift, Nat.succ_ne_zero, IsEmpty.forall_iff, Nat.succ.injEq,
add_eq_zero, OfNat.ofNat_ne_zero, and_false, one_ne_zero, mk_eq_zero, lift_zero]
#align first_order.sequence₂.lift_mk FirstOrder.Sequence₂.lift_mk
@[simp]
theorem sum_card : Cardinal.sum (fun i => #(Sequence₂ a₀ a₁ a₂ i)) = #a₀ + #a₁ + #a₂ := by
rw [sum_nat_eq_add_sum_succ, sum_nat_eq_add_sum_succ, sum_nat_eq_add_sum_succ]
simp [add_assoc, Sequence₂]
#align first_order.sequence₂.sum_card FirstOrder.Sequence₂.sum_card
end Sequence₂
namespace Language
/-- A constructor for languages with only constants, unary and binary functions, and
unary and binary relations. -/
@[simps]
protected def mk₂ (c f₁ f₂ : Type u) (r₁ r₂ : Type v) : Language :=
⟨Sequence₂ c f₁ f₂, Sequence₂ PEmpty r₁ r₂⟩
#align first_order.language.mk₂ FirstOrder.Language.mk₂
/-- The empty language has no symbols. -/
protected def empty : Language :=
⟨fun _ => Empty, fun _ => Empty⟩
#align first_order.language.empty FirstOrder.Language.empty
instance : Inhabited Language :=
⟨Language.empty⟩
/-- The sum of two languages consists of the disjoint union of their symbols. -/
protected def sum (L : Language.{u, v}) (L' : Language.{u', v'}) : Language :=
⟨fun n => Sum (L.Functions n) (L'.Functions n), fun n => Sum (L.Relations n) (L'.Relations n)⟩
#align first_order.language.sum FirstOrder.Language.sum
variable (L : Language.{u, v})
/-- The type of constants in a given language. -/
-- Porting note(#5171): this linter isn't ported yet.
-- @[nolint has_nonempty_instance]
protected def Constants :=
L.Functions 0
#align first_order.language.constants FirstOrder.Language.Constants
@[simp]
theorem constants_mk₂ (c f₁ f₂ : Type u) (r₁ r₂ : Type v) :
(Language.mk₂ c f₁ f₂ r₁ r₂).Constants = c :=
rfl
#align first_order.language.constants_mk₂ FirstOrder.Language.constants_mk₂
/-- The type of symbols in a given language. -/
-- Porting note(#5171): this linter isn't ported yet.
-- @[nolint has_nonempty_instance]
def Symbols :=
Sum (Σl, L.Functions l) (Σl, L.Relations l)
#align first_order.language.symbols FirstOrder.Language.Symbols
/-- The cardinality of a language is the cardinality of its type of symbols. -/
def card : Cardinal :=
#L.Symbols
#align first_order.language.card FirstOrder.Language.card
/-- A language is relational when it has no function symbols. -/
class IsRelational : Prop where
/-- There are no function symbols in the language. -/
empty_functions : ∀ n, IsEmpty (L.Functions n)
#align first_order.language.is_relational FirstOrder.Language.IsRelational
/-- A language is algebraic when it has no relation symbols. -/
class IsAlgebraic : Prop where
/-- There are no relation symbols in the language. -/
empty_relations : ∀ n, IsEmpty (L.Relations n)
#align first_order.language.is_algebraic FirstOrder.Language.IsAlgebraic
variable {L} {L' : Language.{u', v'}}
theorem card_eq_card_functions_add_card_relations :
L.card =
(Cardinal.sum fun l => Cardinal.lift.{v} #(L.Functions l)) +
Cardinal.sum fun l => Cardinal.lift.{u} #(L.Relations l) := by
simp [card, Symbols]
#align first_order.language.card_eq_card_functions_add_card_relations FirstOrder.Language.card_eq_card_functions_add_card_relations
instance [L.IsRelational] {n : ℕ} : IsEmpty (L.Functions n) :=
IsRelational.empty_functions n
instance [L.IsAlgebraic] {n : ℕ} : IsEmpty (L.Relations n) :=
IsAlgebraic.empty_relations n
instance isRelational_of_empty_functions {symb : ℕ → Type*} :
IsRelational ⟨fun _ => Empty, symb⟩ :=
⟨fun _ => instIsEmptyEmpty⟩
#align first_order.language.is_relational_of_empty_functions FirstOrder.Language.isRelational_of_empty_functions
instance isAlgebraic_of_empty_relations {symb : ℕ → Type*} : IsAlgebraic ⟨symb, fun _ => Empty⟩ :=
⟨fun _ => instIsEmptyEmpty⟩
#align first_order.language.is_algebraic_of_empty_relations FirstOrder.Language.isAlgebraic_of_empty_relations
instance isRelational_empty : IsRelational Language.empty :=
Language.isRelational_of_empty_functions
#align first_order.language.is_relational_empty FirstOrder.Language.isRelational_empty
instance isAlgebraic_empty : IsAlgebraic Language.empty :=
Language.isAlgebraic_of_empty_relations
#align first_order.language.is_algebraic_empty FirstOrder.Language.isAlgebraic_empty
instance isRelational_sum [L.IsRelational] [L'.IsRelational] : IsRelational (L.sum L') :=
⟨fun _ => instIsEmptySum⟩
#align first_order.language.is_relational_sum FirstOrder.Language.isRelational_sum
instance isAlgebraic_sum [L.IsAlgebraic] [L'.IsAlgebraic] : IsAlgebraic (L.sum L') :=
⟨fun _ => instIsEmptySum⟩
#align first_order.language.is_algebraic_sum FirstOrder.Language.isAlgebraic_sum
instance isRelational_mk₂ {c f₁ f₂ : Type u} {r₁ r₂ : Type v} [h0 : IsEmpty c] [h1 : IsEmpty f₁]
[h2 : IsEmpty f₂] : IsRelational (Language.mk₂ c f₁ f₂ r₁ r₂) :=
⟨fun n =>
Nat.casesOn n h0 fun n => Nat.casesOn n h1 fun n => Nat.casesOn n h2 fun _ =>
inferInstanceAs (IsEmpty PEmpty)⟩
#align first_order.language.is_relational_mk₂ FirstOrder.Language.isRelational_mk₂
instance isAlgebraic_mk₂ {c f₁ f₂ : Type u} {r₁ r₂ : Type v} [h1 : IsEmpty r₁] [h2 : IsEmpty r₂] :
IsAlgebraic (Language.mk₂ c f₁ f₂ r₁ r₂) :=
⟨fun n =>
Nat.casesOn n (inferInstanceAs (IsEmpty PEmpty)) fun n =>
Nat.casesOn n h1 fun n => Nat.casesOn n h2 fun _ => inferInstanceAs (IsEmpty PEmpty)⟩
#align first_order.language.is_algebraic_mk₂ FirstOrder.Language.isAlgebraic_mk₂
instance subsingleton_mk₂_functions {c f₁ f₂ : Type u} {r₁ r₂ : Type v} [h0 : Subsingleton c]
[h1 : Subsingleton f₁] [h2 : Subsingleton f₂] {n : ℕ} :
Subsingleton ((Language.mk₂ c f₁ f₂ r₁ r₂).Functions n) :=
Nat.casesOn n h0 fun n =>
Nat.casesOn n h1 fun n => Nat.casesOn n h2 fun _ => ⟨fun x => PEmpty.elim x⟩
#align first_order.language.subsingleton_mk₂_functions FirstOrder.Language.subsingleton_mk₂_functions
instance subsingleton_mk₂_relations {c f₁ f₂ : Type u} {r₁ r₂ : Type v} [h1 : Subsingleton r₁]
[h2 : Subsingleton r₂] {n : ℕ} : Subsingleton ((Language.mk₂ c f₁ f₂ r₁ r₂).Relations n) :=
Nat.casesOn n ⟨fun x => PEmpty.elim x⟩ fun n =>
Nat.casesOn n h1 fun n => Nat.casesOn n h2 fun _ => ⟨fun x => PEmpty.elim x⟩
#align first_order.language.subsingleton_mk₂_relations FirstOrder.Language.subsingleton_mk₂_relations
@[simp]
theorem empty_card : Language.empty.card = 0 := by simp [card_eq_card_functions_add_card_relations]
#align first_order.language.empty_card FirstOrder.Language.empty_card
instance isEmpty_empty : IsEmpty Language.empty.Symbols := by
simp only [Language.Symbols, isEmpty_sum, isEmpty_sigma]
exact ⟨fun _ => inferInstance, fun _ => inferInstance⟩
#align first_order.language.is_empty_empty FirstOrder.Language.isEmpty_empty
instance Countable.countable_functions [h : Countable L.Symbols] : Countable (Σl, L.Functions l) :=
@Function.Injective.countable _ _ h _ Sum.inl_injective
#align first_order.language.countable.countable_functions FirstOrder.Language.Countable.countable_functions
@[simp]
theorem card_functions_sum (i : ℕ) :
#((L.sum L').Functions i)
= (Cardinal.lift.{u'} #(L.Functions i) + Cardinal.lift.{u} #(L'.Functions i) : Cardinal) := by
simp [Language.sum]
#align first_order.language.card_functions_sum FirstOrder.Language.card_functions_sum
@[simp]
theorem card_relations_sum (i : ℕ) :
#((L.sum L').Relations i) =
Cardinal.lift.{v'} #(L.Relations i) + Cardinal.lift.{v} #(L'.Relations i) := by
simp [Language.sum]
#align first_order.language.card_relations_sum FirstOrder.Language.card_relations_sum
@[simp]
theorem card_sum :
(L.sum L').card = Cardinal.lift.{max u' v'} L.card + Cardinal.lift.{max u v} L'.card := by
simp only [card_eq_card_functions_add_card_relations, card_functions_sum, card_relations_sum,
sum_add_distrib', lift_add, lift_sum, lift_lift]
simp only [add_assoc, add_comm (Cardinal.sum fun i => (#(L'.Functions i)).lift)]
#align first_order.language.card_sum FirstOrder.Language.card_sum
@[simp]
theorem card_mk₂ (c f₁ f₂ : Type u) (r₁ r₂ : Type v) :
(Language.mk₂ c f₁ f₂ r₁ r₂).card =
Cardinal.lift.{v} #c + Cardinal.lift.{v} #f₁ + Cardinal.lift.{v} #f₂ +
Cardinal.lift.{u} #r₁ + Cardinal.lift.{u} #r₂ := by
simp [card_eq_card_functions_add_card_relations, add_assoc]
#align first_order.language.card_mk₂ FirstOrder.Language.card_mk₂
variable (L) (M : Type w)
/-- A first-order structure on a type `M` consists of interpretations of all the symbols in a given
language. Each function of arity `n` is interpreted as a function sending tuples of length `n`
(modeled as `(Fin n → M)`) to `M`, and a relation of arity `n` is a function from tuples of length
`n` to `Prop`. -/
@[ext]
class Structure where
/-- Interpretation of the function symbols -/
funMap : ∀ {n}, L.Functions n → (Fin n → M) → M
/-- Interpretation of the relation symbols -/
RelMap : ∀ {n}, L.Relations n → (Fin n → M) → Prop
set_option linter.uppercaseLean3 false in
#align first_order.language.Structure FirstOrder.Language.Structure
set_option linter.uppercaseLean3 false in
#align first_order.language.Structure.fun_map FirstOrder.Language.Structure.funMap
set_option linter.uppercaseLean3 false in
#align first_order.language.Structure.rel_map FirstOrder.Language.Structure.RelMap
variable (N : Type w') [L.Structure M] [L.Structure N]
open Structure
/-- Used for defining `FirstOrder.Language.Theory.ModelType.instInhabited`. -/
def Inhabited.trivialStructure {α : Type*} [Inhabited α] : L.Structure α :=
⟨default, default⟩
#align first_order.language.inhabited.trivial_structure FirstOrder.Language.Inhabited.trivialStructure
/-! ### Maps -/
/-- A homomorphism between first-order structures is a function that commutes with the
interpretations of functions and maps tuples in one structure where a given relation is true to
tuples in the second structure where that relation is still true. -/
structure Hom where
/-- The underlying function of a homomorphism of structures -/
toFun : M → N
/-- The homomorphism commutes with the interpretations of the function symbols -/
-- Porting note:
-- The autoparam here used to be `obviously`. We would like to replace it with `aesop`
-- but that isn't currently sufficient.
-- See https://leanprover.zulipchat.com/#narrow/stream/287929-mathlib4/topic/Aesop.20and.20cases
-- If that can be improved, we should change this to `by aesop` and remove the proofs below.
map_fun' : ∀ {n} (f : L.Functions n) (x), toFun (funMap f x) = funMap f (toFun ∘ x) := by
intros; trivial
/-- The homomorphism sends related elements to related elements -/
map_rel' : ∀ {n} (r : L.Relations n) (x), RelMap r x → RelMap r (toFun ∘ x) := by
-- Porting note: see porting note on `Hom.map_fun'`
intros; trivial
#align first_order.language.hom FirstOrder.Language.Hom
@[inherit_doc]
scoped[FirstOrder] notation:25 A " →[" L "] " B => FirstOrder.Language.Hom L A B
/-- An embedding of first-order structures is an embedding that commutes with the
interpretations of functions and relations. -/
structure Embedding extends M ↪ N where
map_fun' : ∀ {n} (f : L.Functions n) (x), toFun (funMap f x) = funMap f (toFun ∘ x) := by
-- Porting note: see porting note on `Hom.map_fun'`
intros; trivial
map_rel' : ∀ {n} (r : L.Relations n) (x), RelMap r (toFun ∘ x) ↔ RelMap r x := by
-- Porting note: see porting note on `Hom.map_fun'`
intros; trivial
#align first_order.language.embedding FirstOrder.Language.Embedding
@[inherit_doc]
scoped[FirstOrder] notation:25 A " ↪[" L "] " B => FirstOrder.Language.Embedding L A B
/-- An equivalence of first-order structures is an equivalence that commutes with the
interpretations of functions and relations. -/
structure Equiv extends M ≃ N where
map_fun' : ∀ {n} (f : L.Functions n) (x), toFun (funMap f x) = funMap f (toFun ∘ x) := by
-- Porting note: see porting note on `Hom.map_fun'`
intros; trivial
map_rel' : ∀ {n} (r : L.Relations n) (x), RelMap r (toFun ∘ x) ↔ RelMap r x := by
-- Porting note: see porting note on `Hom.map_fun'`
intros; trivial
#align first_order.language.equiv FirstOrder.Language.Equiv
@[inherit_doc]
scoped[FirstOrder] notation:25 A " ≃[" L "] " B => FirstOrder.Language.Equiv L A B
-- Porting note: was [L.Structure P] and [L.Structure Q]
-- The former reported an error.
variable {L M N} {P : Type*} [Structure L P] {Q : Type*} [Structure L Q]
-- Porting note (#11445): new definition
/-- Interpretation of a constant symbol -/
@[coe]
def constantMap (c : L.Constants) : M := funMap c default
instance : CoeTC L.Constants M :=
⟨constantMap⟩
theorem funMap_eq_coe_constants {c : L.Constants} {x : Fin 0 → M} : funMap c x = c :=
congr rfl (funext finZeroElim)
#align first_order.language.fun_map_eq_coe_constants FirstOrder.Language.funMap_eq_coe_constants
/-- Given a language with a nonempty type of constants, any structure will be nonempty. This cannot
be a global instance, because `L` becomes a metavariable. -/
theorem nonempty_of_nonempty_constants [h : Nonempty L.Constants] : Nonempty M :=
h.map (↑)
#align first_order.language.nonempty_of_nonempty_constants FirstOrder.Language.nonempty_of_nonempty_constants
/-- The function map for `FirstOrder.Language.Structure₂`. -/
def funMap₂ {c f₁ f₂ : Type u} {r₁ r₂ : Type v} (c' : c → M) (f₁' : f₁ → M → M)
(f₂' : f₂ → M → M → M) : ∀ {n}, (Language.mk₂ c f₁ f₂ r₁ r₂).Functions n → (Fin n → M) → M
| 0, f, _ => c' f
| 1, f, x => f₁' f (x 0)
| 2, f, x => f₂' f (x 0) (x 1)
| _ + 3, f, _ => PEmpty.elim f
#align first_order.language.fun_map₂ FirstOrder.Language.funMap₂
/-- The relation map for `FirstOrder.Language.Structure₂`. -/
def RelMap₂ {c f₁ f₂ : Type u} {r₁ r₂ : Type v} (r₁' : r₁ → Set M) (r₂' : r₂ → M → M → Prop) :
∀ {n}, (Language.mk₂ c f₁ f₂ r₁ r₂).Relations n → (Fin n → M) → Prop
| 0, r, _ => PEmpty.elim r
| 1, r, x => x 0 ∈ r₁' r
| 2, r, x => r₂' r (x 0) (x 1)
| _ + 3, r, _ => PEmpty.elim r
#align first_order.language.rel_map₂ FirstOrder.Language.RelMap₂
/-- A structure constructor to match `FirstOrder.Language₂`. -/
protected def Structure.mk₂ {c f₁ f₂ : Type u} {r₁ r₂ : Type v} (c' : c → M) (f₁' : f₁ → M → M)
(f₂' : f₂ → M → M → M) (r₁' : r₁ → Set M) (r₂' : r₂ → M → M → Prop) :
(Language.mk₂ c f₁ f₂ r₁ r₂).Structure M :=
⟨funMap₂ c' f₁' f₂', RelMap₂ r₁' r₂'⟩
set_option linter.uppercaseLean3 false in
#align first_order.language.Structure.mk₂ FirstOrder.Language.Structure.mk₂
namespace Structure
variable {c f₁ f₂ : Type u} {r₁ r₂ : Type v}
variable {c' : c → M} {f₁' : f₁ → M → M} {f₂' : f₂ → M → M → M}
variable {r₁' : r₁ → Set M} {r₂' : r₂ → M → M → Prop}
@[simp]
theorem funMap_apply₀ (c₀ : c) {x : Fin 0 → M} :
@Structure.funMap _ M (Structure.mk₂ c' f₁' f₂' r₁' r₂') 0 c₀ x = c' c₀ :=
rfl
set_option linter.uppercaseLean3 false in
#align first_order.language.Structure.fun_map_apply₀ FirstOrder.Language.Structure.funMap_apply₀
@[simp]
theorem funMap_apply₁ (f : f₁) (x : M) :
@Structure.funMap _ M (Structure.mk₂ c' f₁' f₂' r₁' r₂') 1 f ![x] = f₁' f x :=
rfl
set_option linter.uppercaseLean3 false in
#align first_order.language.Structure.fun_map_apply₁ FirstOrder.Language.Structure.funMap_apply₁
@[simp]
theorem funMap_apply₂ (f : f₂) (x y : M) :
@Structure.funMap _ M (Structure.mk₂ c' f₁' f₂' r₁' r₂') 2 f ![x, y] = f₂' f x y :=
rfl
set_option linter.uppercaseLean3 false in
#align first_order.language.Structure.fun_map_apply₂ FirstOrder.Language.Structure.funMap_apply₂
@[simp]
theorem relMap_apply₁ (r : r₁) (x : M) :
@Structure.RelMap _ M (Structure.mk₂ c' f₁' f₂' r₁' r₂') 1 r ![x] = (x ∈ r₁' r) :=
rfl
set_option linter.uppercaseLean3 false in
#align first_order.language.Structure.rel_map_apply₁ FirstOrder.Language.Structure.relMap_apply₁
@[simp]
theorem relMap_apply₂ (r : r₂) (x y : M) :
@Structure.RelMap _ M (Structure.mk₂ c' f₁' f₂' r₁' r₂') 2 r ![x, y] = r₂' r x y :=
rfl
set_option linter.uppercaseLean3 false in
#align first_order.language.Structure.rel_map_apply₂ FirstOrder.Language.Structure.relMap_apply₂
end Structure
/-- `HomClass L F M N` states that `F` is a type of `L`-homomorphisms. You should extend this
typeclass when you extend `FirstOrder.Language.Hom`. -/
class HomClass (L : outParam Language) (F M N : Type*)
[FunLike F M N] [L.Structure M] [L.Structure N] : Prop where
map_fun : ∀ (φ : F) {n} (f : L.Functions n) (x), φ (funMap f x) = funMap f (φ ∘ x)
map_rel : ∀ (φ : F) {n} (r : L.Relations n) (x), RelMap r x → RelMap r (φ ∘ x)
#align first_order.language.hom_class FirstOrder.Language.HomClass
/-- `StrongHomClass L F M N` states that `F` is a type of `L`-homomorphisms which preserve
relations in both directions. -/
class StrongHomClass (L : outParam Language) (F M N : Type*)
[FunLike F M N] [L.Structure M] [L.Structure N] : Prop where
map_fun : ∀ (φ : F) {n} (f : L.Functions n) (x), φ (funMap f x) = funMap f (φ ∘ x)
map_rel : ∀ (φ : F) {n} (r : L.Relations n) (x), RelMap r (φ ∘ x) ↔ RelMap r x
#align first_order.language.strong_hom_class FirstOrder.Language.StrongHomClass
-- Porting note: using implicit brackets for `Structure` arguments
instance (priority := 100) StrongHomClass.homClass [L.Structure M]
[L.Structure N] [FunLike F M N] [StrongHomClass L F M N] : HomClass L F M N where
map_fun := StrongHomClass.map_fun
map_rel φ _ R x := (StrongHomClass.map_rel φ R x).2
#align first_order.language.strong_hom_class.hom_class FirstOrder.Language.StrongHomClass.homClass
/-- Not an instance to avoid a loop. -/
theorem HomClass.strongHomClassOfIsAlgebraic [L.IsAlgebraic] {F M N} [L.Structure M] [L.Structure N]
[FunLike F M N] [HomClass L F M N] : StrongHomClass L F M N where
map_fun := HomClass.map_fun
map_rel _ n R _ := (IsAlgebraic.empty_relations n).elim R
#align first_order.language.hom_class.strong_hom_class_of_is_algebraic FirstOrder.Language.HomClass.strongHomClassOfIsAlgebraic
theorem HomClass.map_constants {F M N} [L.Structure M] [L.Structure N] [FunLike F M N]
[HomClass L F M N] (φ : F) (c : L.Constants) : φ c = c :=
(HomClass.map_fun φ c default).trans (congr rfl (funext default))
#align first_order.language.hom_class.map_constants FirstOrder.Language.HomClass.map_constants
attribute [inherit_doc FirstOrder.Language.Hom.map_fun'] FirstOrder.Language.Embedding.map_fun'
FirstOrder.Language.HomClass.map_fun FirstOrder.Language.StrongHomClass.map_fun
FirstOrder.Language.Equiv.map_fun'
attribute [inherit_doc FirstOrder.Language.Hom.map_rel'] FirstOrder.Language.Embedding.map_rel'
FirstOrder.Language.HomClass.map_rel FirstOrder.Language.StrongHomClass.map_rel
FirstOrder.Language.Equiv.map_rel'
namespace Hom
instance instFunLike : FunLike (M →[L] N) M N where
coe := Hom.toFun
coe_injective' f g h := by cases f; cases g; cases h; rfl
#align first_order.language.hom.fun_like FirstOrder.Language.Hom.instFunLike
instance homClass : HomClass L (M →[L] N) M N where
map_fun := map_fun'
map_rel := map_rel'
#align first_order.language.hom.hom_class FirstOrder.Language.Hom.homClass
instance [L.IsAlgebraic] : StrongHomClass L (M →[L] N) M N :=
HomClass.strongHomClassOfIsAlgebraic
instance hasCoeToFun : CoeFun (M →[L] N) fun _ => M → N :=
DFunLike.hasCoeToFun
#align first_order.language.hom.has_coe_to_fun FirstOrder.Language.Hom.hasCoeToFun
@[simp]
theorem toFun_eq_coe {f : M →[L] N} : f.toFun = (f : M → N) :=
rfl
#align first_order.language.hom.to_fun_eq_coe FirstOrder.Language.Hom.toFun_eq_coe
@[ext]
theorem ext ⦃f g : M →[L] N⦄ (h : ∀ x, f x = g x) : f = g :=
DFunLike.ext f g h
#align first_order.language.hom.ext FirstOrder.Language.Hom.ext
theorem ext_iff {f g : M →[L] N} : f = g ↔ ∀ x, f x = g x :=
DFunLike.ext_iff
#align first_order.language.hom.ext_iff FirstOrder.Language.Hom.ext_iff
@[simp]
theorem map_fun (φ : M →[L] N) {n : ℕ} (f : L.Functions n) (x : Fin n → M) :
φ (funMap f x) = funMap f (φ ∘ x) :=
HomClass.map_fun φ f x
#align first_order.language.hom.map_fun FirstOrder.Language.Hom.map_fun
@[simp]
theorem map_constants (φ : M →[L] N) (c : L.Constants) : φ c = c :=
HomClass.map_constants φ c
#align first_order.language.hom.map_constants FirstOrder.Language.Hom.map_constants
@[simp]
theorem map_rel (φ : M →[L] N) {n : ℕ} (r : L.Relations n) (x : Fin n → M) :
RelMap r x → RelMap r (φ ∘ x) :=
HomClass.map_rel φ r x
#align first_order.language.hom.map_rel FirstOrder.Language.Hom.map_rel
variable (L) (M)
/-- The identity map from a structure to itself. -/
@[refl]
def id : M →[L] M where
toFun m := m
#align first_order.language.hom.id FirstOrder.Language.Hom.id
variable {L} {M}
instance : Inhabited (M →[L] M) :=
⟨id L M⟩
@[simp]
theorem id_apply (x : M) : id L M x = x :=
rfl
#align first_order.language.hom.id_apply FirstOrder.Language.Hom.id_apply
/-- Composition of first-order homomorphisms. -/
@[trans]
def comp (hnp : N →[L] P) (hmn : M →[L] N) : M →[L] P where
toFun := hnp ∘ hmn
-- Porting note: should be done by autoparam?
map_fun' _ _ := by simp; rfl
-- Porting note: should be done by autoparam?
map_rel' _ _ h := map_rel _ _ _ (map_rel _ _ _ h)
#align first_order.language.hom.comp FirstOrder.Language.Hom.comp
@[simp]
theorem comp_apply (g : N →[L] P) (f : M →[L] N) (x : M) : g.comp f x = g (f x) :=
rfl
#align first_order.language.hom.comp_apply FirstOrder.Language.Hom.comp_apply
/-- Composition of first-order homomorphisms is associative. -/
theorem comp_assoc (f : M →[L] N) (g : N →[L] P) (h : P →[L] Q) :
(h.comp g).comp f = h.comp (g.comp f) :=
rfl
#align first_order.language.hom.comp_assoc FirstOrder.Language.Hom.comp_assoc
@[simp]
theorem comp_id (f : M →[L] N) : f.comp (id L M) = f :=
rfl
@[simp]
theorem id_comp (f : M →[L] N) : (id L N).comp f = f :=
rfl
end Hom
/-- Any element of a `HomClass` can be realized as a first_order homomorphism. -/
def HomClass.toHom {F M N} [L.Structure M] [L.Structure N] [FunLike F M N]
[HomClass L F M N] : F → M →[L] N := fun φ =>
⟨φ, HomClass.map_fun φ, HomClass.map_rel φ⟩
#align first_order.language.hom_class.to_hom FirstOrder.Language.HomClass.toHom
namespace Embedding
instance funLike : FunLike (M ↪[L] N) M N where
coe f := f.toFun
coe_injective' f g h := by
cases f
cases g
congr
ext x
exact Function.funext_iff.1 h x
instance embeddingLike : EmbeddingLike (M ↪[L] N) M N where
injective' f := f.toEmbedding.injective
#align first_order.language.embedding.embedding_like FirstOrder.Language.Embedding.embeddingLike
instance strongHomClass : StrongHomClass L (M ↪[L] N) M N where
map_fun := map_fun'
map_rel := map_rel'
#align first_order.language.embedding.strong_hom_class FirstOrder.Language.Embedding.strongHomClass
#noalign first_order.language.embedding.has_coe_to_fun -- Porting note: replaced by funLike instance
@[simp]
theorem map_fun (φ : M ↪[L] N) {n : ℕ} (f : L.Functions n) (x : Fin n → M) :
φ (funMap f x) = funMap f (φ ∘ x) :=
HomClass.map_fun φ f x
#align first_order.language.embedding.map_fun FirstOrder.Language.Embedding.map_fun
@[simp]
theorem map_constants (φ : M ↪[L] N) (c : L.Constants) : φ c = c :=
HomClass.map_constants φ c
#align first_order.language.embedding.map_constants FirstOrder.Language.Embedding.map_constants
@[simp]
theorem map_rel (φ : M ↪[L] N) {n : ℕ} (r : L.Relations n) (x : Fin n → M) :
RelMap r (φ ∘ x) ↔ RelMap r x :=
StrongHomClass.map_rel φ r x
#align first_order.language.embedding.map_rel FirstOrder.Language.Embedding.map_rel
/-- A first-order embedding is also a first-order homomorphism. -/
def toHom : (M ↪[L] N) → M →[L] N :=
HomClass.toHom
#align first_order.language.embedding.to_hom FirstOrder.Language.Embedding.toHom
@[simp]
theorem coe_toHom {f : M ↪[L] N} : (f.toHom : M → N) = f :=
rfl
#align first_order.language.embedding.coe_to_hom FirstOrder.Language.Embedding.coe_toHom
theorem coe_injective : @Function.Injective (M ↪[L] N) (M → N) (↑)
| f, g, h => by
cases f
cases g
congr
ext x
exact Function.funext_iff.1 h x
#align first_order.language.embedding.coe_injective FirstOrder.Language.Embedding.coe_injective
@[ext]
theorem ext ⦃f g : M ↪[L] N⦄ (h : ∀ x, f x = g x) : f = g :=
coe_injective (funext h)
#align first_order.language.embedding.ext FirstOrder.Language.Embedding.ext
theorem ext_iff {f g : M ↪[L] N} : f = g ↔ ∀ x, f x = g x :=
⟨fun h _ => h ▸ rfl, fun h => ext h⟩
#align first_order.language.embedding.ext_iff FirstOrder.Language.Embedding.ext_iff
| Mathlib/ModelTheory/Basic.lean | 670 | 673 | theorem toHom_injective : @Function.Injective (M ↪[L] N) (M →[L] N) (·.toHom) := by |
intro f f' h
ext
exact congr_fun (congr_arg (↑) h) _
|
/-
Copyright (c) 2021 Patrick Massot. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Patrick Massot
-/
import Mathlib.Topology.Algebra.Valuation
import Mathlib.Topology.Algebra.WithZeroTopology
import Mathlib.Topology.Algebra.UniformField
#align_import topology.algebra.valued_field from "leanprover-community/mathlib"@"3e0c4d76b6ebe9dfafb67d16f7286d2731ed6064"
/-!
# Valued fields and their completions
In this file we study the topology of a field `K` endowed with a valuation (in our application
to adic spaces, `K` will be the valuation field associated to some valuation on a ring, defined in
valuation.basic).
We already know from valuation.topology that one can build a topology on `K` which
makes it a topological ring.
The first goal is to show `K` is a topological *field*, ie inversion is continuous
at every non-zero element.
The next goal is to prove `K` is a *completable* topological field. This gives us
a completion `hat K` which is a topological field. We also prove that `K` is automatically
separated, so the map from `K` to `hat K` is injective.
Then we extend the valuation given on `K` to a valuation on `hat K`.
-/
open Filter Set
open Topology
section DivisionRing
variable {K : Type*} [DivisionRing K] {Γ₀ : Type*} [LinearOrderedCommGroupWithZero Γ₀]
section ValuationTopologicalDivisionRing
section InversionEstimate
variable (v : Valuation K Γ₀)
-- The following is the main technical lemma ensuring that inversion is continuous
-- in the topology induced by a valuation on a division ring (i.e. the next instance)
-- and the fact that a valued field is completable
-- [BouAC, VI.5.1 Lemme 1]
| Mathlib/Topology/Algebra/ValuedField.lean | 51 | 72 | theorem Valuation.inversion_estimate {x y : K} {γ : Γ₀ˣ} (y_ne : y ≠ 0)
(h : v (x - y) < min (γ * (v y * v y)) (v y)) : v (x⁻¹ - y⁻¹) < γ := by |
have hyp1 : v (x - y) < γ * (v y * v y) := lt_of_lt_of_le h (min_le_left _ _)
have hyp1' : v (x - y) * (v y * v y)⁻¹ < γ := mul_inv_lt_of_lt_mul₀ hyp1
have hyp2 : v (x - y) < v y := lt_of_lt_of_le h (min_le_right _ _)
have key : v x = v y := Valuation.map_eq_of_sub_lt v hyp2
have x_ne : x ≠ 0 := by
intro h
apply y_ne
rw [h, v.map_zero] at key
exact v.zero_iff.1 key.symm
have decomp : x⁻¹ - y⁻¹ = x⁻¹ * (y - x) * y⁻¹ := by
rw [mul_sub_left_distrib, sub_mul, mul_assoc, show y * y⁻¹ = 1 from mul_inv_cancel y_ne,
show x⁻¹ * x = 1 from inv_mul_cancel x_ne, mul_one, one_mul]
calc
v (x⁻¹ - y⁻¹) = v (x⁻¹ * (y - x) * y⁻¹) := by rw [decomp]
_ = v x⁻¹ * (v <| y - x) * v y⁻¹ := by repeat' rw [Valuation.map_mul]
_ = (v x)⁻¹ * (v <| y - x) * (v y)⁻¹ := by rw [map_inv₀, map_inv₀]
_ = (v <| y - x) * (v y * v y)⁻¹ := by rw [mul_assoc, mul_comm, key, mul_assoc, mul_inv_rev]
_ = (v <| y - x) * (v y * v y)⁻¹ := rfl
_ = (v <| x - y) * (v y * v y)⁻¹ := by rw [Valuation.map_sub_swap]
_ < γ := hyp1'
|
/-
Copyright (c) 2018 Robert Y. Lewis. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Robert Y. Lewis, Matthew Robert Ballard
-/
import Mathlib.NumberTheory.Divisors
import Mathlib.Data.Nat.Digits
import Mathlib.Data.Nat.MaxPowDiv
import Mathlib.Data.Nat.Multiplicity
import Mathlib.Tactic.IntervalCases
#align_import number_theory.padics.padic_val from "leanprover-community/mathlib"@"60fa54e778c9e85d930efae172435f42fb0d71f7"
/-!
# `p`-adic Valuation
This file defines the `p`-adic valuation on `ℕ`, `ℤ`, and `ℚ`.
The `p`-adic valuation on `ℚ` is the difference of the multiplicities of `p` in the numerator and
denominator of `q`. This function obeys the standard properties of a valuation, with the appropriate
assumptions on `p`. The `p`-adic valuations on `ℕ` and `ℤ` agree with that on `ℚ`.
The valuation induces a norm on `ℚ`. This norm is defined in padicNorm.lean.
## Notations
This file uses the local notation `/.` for `Rat.mk`.
## Implementation notes
Much, but not all, of this file assumes that `p` is prime. This assumption is inferred automatically
by taking `[Fact p.Prime]` as a type class argument.
## Calculations with `p`-adic valuations
* `padicValNat_factorial`: Legendre's Theorem. The `p`-adic valuation of `n!` is the sum of the
quotients `n / p ^ i`. This sum is expressed over the finset `Ico 1 b` where `b` is any bound
greater than `log p n`. See `Nat.Prime.multiplicity_factorial` for the same result but stated in the
language of prime multiplicity.
* `sub_one_mul_padicValNat_factorial`: Legendre's Theorem. Taking (`p - 1`) times
the `p`-adic valuation of `n!` equals `n` minus the sum of base `p` digits of `n`.
* `padicValNat_choose`: Kummer's Theorem. The `p`-adic valuation of `n.choose k` is the number
of carries when `k` and `n - k` are added in base `p`. This sum is expressed over the finset
`Ico 1 b` where `b` is any bound greater than `log p n`. See `Nat.Prime.multiplicity_choose` for the
same result but stated in the language of prime multiplicity.
* `sub_one_mul_padicValNat_choose_eq_sub_sum_digits`: Kummer's Theorem. Taking (`p - 1`) times the
`p`-adic valuation of the binomial `n` over `k` equals the sum of the digits of `k` plus the sum of
the digits of `n - k` minus the sum of digits of `n`, all base `p`.
## References
* [F. Q. Gouvêa, *p-adic numbers*][gouvea1997]
* [R. Y. Lewis, *A formal proof of Hensel's lemma over the p-adic integers*][lewis2019]
* <https://en.wikipedia.org/wiki/P-adic_number>
## Tags
p-adic, p adic, padic, norm, valuation
-/
universe u
open Nat
open Rat
open multiplicity
/-- For `p ≠ 1`, the `p`-adic valuation of a natural `n ≠ 0` is the largest natural number `k` such
that `p^k` divides `n`. If `n = 0` or `p = 1`, then `padicValNat p q` defaults to `0`. -/
def padicValNat (p : ℕ) (n : ℕ) : ℕ :=
if h : p ≠ 1 ∧ 0 < n then (multiplicity p n).get (multiplicity.finite_nat_iff.2 h) else 0
#align padic_val_nat padicValNat
namespace padicValNat
open multiplicity
variable {p : ℕ}
/-- `padicValNat p 0` is `0` for any `p`. -/
@[simp]
protected theorem zero : padicValNat p 0 = 0 := by simp [padicValNat]
#align padic_val_nat.zero padicValNat.zero
/-- `padicValNat p 1` is `0` for any `p`. -/
@[simp]
protected theorem one : padicValNat p 1 = 0 := by
unfold padicValNat
split_ifs
· simp
· rfl
#align padic_val_nat.one padicValNat.one
/-- If `p ≠ 0` and `p ≠ 1`, then `padicValNat p p` is `1`. -/
@[simp]
theorem self (hp : 1 < p) : padicValNat p p = 1 := by
have neq_one : ¬p = 1 ↔ True := iff_of_true hp.ne' trivial
have eq_zero_false : p = 0 ↔ False := iff_false_intro (zero_lt_one.trans hp).ne'
simp [padicValNat, neq_one, eq_zero_false]
#align padic_val_nat.self padicValNat.self
@[simp]
theorem eq_zero_iff {n : ℕ} : padicValNat p n = 0 ↔ p = 1 ∨ n = 0 ∨ ¬p ∣ n := by
simp only [padicValNat, dite_eq_right_iff, PartENat.get_eq_iff_eq_coe, Nat.cast_zero,
multiplicity_eq_zero, and_imp, pos_iff_ne_zero, Ne, ← or_iff_not_imp_left]
#align padic_val_nat.eq_zero_iff padicValNat.eq_zero_iff
theorem eq_zero_of_not_dvd {n : ℕ} (h : ¬p ∣ n) : padicValNat p n = 0 :=
eq_zero_iff.2 <| Or.inr <| Or.inr h
#align padic_val_nat.eq_zero_of_not_dvd padicValNat.eq_zero_of_not_dvd
open Nat.maxPowDiv
theorem maxPowDiv_eq_multiplicity {p n : ℕ} (hp : 1 < p) (hn : 0 < n) :
p.maxPowDiv n = multiplicity p n := by
apply multiplicity.unique <| pow_dvd p n
intro h
apply Nat.not_lt.mpr <| le_of_dvd hp hn h
simp
theorem maxPowDiv_eq_multiplicity_get {p n : ℕ} (hp : 1 < p) (hn : 0 < n) (h : Finite p n) :
p.maxPowDiv n = (multiplicity p n).get h := by
rw [PartENat.get_eq_iff_eq_coe.mpr]
apply maxPowDiv_eq_multiplicity hp hn|>.symm
/-- Allows for more efficient code for `padicValNat` -/
@[csimp]
theorem padicValNat_eq_maxPowDiv : @padicValNat = @maxPowDiv := by
ext p n
by_cases h : 1 < p ∧ 0 < n
· dsimp [padicValNat]
rw [dif_pos ⟨Nat.ne_of_gt h.1,h.2⟩, maxPowDiv_eq_multiplicity_get h.1 h.2]
· simp only [not_and_or,not_gt_eq,Nat.le_zero] at h
apply h.elim
· intro h
interval_cases p
· simp [Classical.em]
· dsimp [padicValNat, maxPowDiv]
rw [go, if_neg, dif_neg] <;> simp
· intro h
simp [h]
end padicValNat
/-- For `p ≠ 1`, the `p`-adic valuation of an integer `z ≠ 0` is the largest natural number `k` such
that `p^k` divides `z`. If `x = 0` or `p = 1`, then `padicValInt p q` defaults to `0`. -/
def padicValInt (p : ℕ) (z : ℤ) : ℕ :=
padicValNat p z.natAbs
#align padic_val_int padicValInt
namespace padicValInt
open multiplicity
variable {p : ℕ}
theorem of_ne_one_ne_zero {z : ℤ} (hp : p ≠ 1) (hz : z ≠ 0) :
padicValInt p z =
(multiplicity (p : ℤ) z).get
(by
apply multiplicity.finite_int_iff.2
simp [hp, hz]) := by
rw [padicValInt, padicValNat, dif_pos (And.intro hp (Int.natAbs_pos.mpr hz))]
simp only [multiplicity.Int.natAbs p z]
#align padic_val_int.of_ne_one_ne_zero padicValInt.of_ne_one_ne_zero
/-- `padicValInt p 0` is `0` for any `p`. -/
@[simp]
protected theorem zero : padicValInt p 0 = 0 := by simp [padicValInt]
#align padic_val_int.zero padicValInt.zero
/-- `padicValInt p 1` is `0` for any `p`. -/
@[simp]
protected theorem one : padicValInt p 1 = 0 := by simp [padicValInt]
#align padic_val_int.one padicValInt.one
/-- The `p`-adic value of a natural is its `p`-adic value as an integer. -/
@[simp]
theorem of_nat {n : ℕ} : padicValInt p n = padicValNat p n := by simp [padicValInt]
#align padic_val_int.of_nat padicValInt.of_nat
/-- If `p ≠ 0` and `p ≠ 1`, then `padicValInt p p` is `1`. -/
theorem self (hp : 1 < p) : padicValInt p p = 1 := by simp [padicValNat.self hp]
#align padic_val_int.self padicValInt.self
| Mathlib/NumberTheory/Padics/PadicVal.lean | 191 | 193 | theorem eq_zero_of_not_dvd {z : ℤ} (h : ¬(p : ℤ) ∣ z) : padicValInt p z = 0 := by |
rw [padicValInt, padicValNat]
split_ifs <;> simp [multiplicity.Int.natAbs, multiplicity_eq_zero.2 h]
|
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Mario Carneiro
-/
import Mathlib.MeasureTheory.Measure.NullMeasurable
import Mathlib.MeasureTheory.MeasurableSpace.Basic
import Mathlib.Topology.Algebra.Order.LiminfLimsup
#align_import measure_theory.measure.measure_space from "leanprover-community/mathlib"@"343e80208d29d2d15f8050b929aa50fe4ce71b55"
/-!
# Measure spaces
The definition of a measure and a measure space are in `MeasureTheory.MeasureSpaceDef`, with
only a few basic properties. This file provides many more properties of these objects.
This separation allows the measurability tactic to import only the file `MeasureSpaceDef`, and to
be available in `MeasureSpace` (through `MeasurableSpace`).
Given a measurable space `α`, a measure on `α` is a function that sends measurable sets to the
extended nonnegative reals that satisfies the following conditions:
1. `μ ∅ = 0`;
2. `μ` is countably additive. This means that the measure of a countable union of pairwise disjoint
sets is equal to the measure of the individual sets.
Every measure can be canonically extended to an outer measure, so that it assigns values to
all subsets, not just the measurable subsets. On the other hand, a measure that is countably
additive on measurable sets can be restricted to measurable sets to obtain a measure.
In this file a measure is defined to be an outer measure that is countably additive on
measurable sets, with the additional assumption that the outer measure is the canonical
extension of the restricted measure.
Measures on `α` form a complete lattice, and are closed under scalar multiplication with `ℝ≥0∞`.
Given a measure, the null sets are the sets where `μ s = 0`, where `μ` denotes the corresponding
outer measure (so `s` might not be measurable). We can then define the completion of `μ` as the
measure on the least `σ`-algebra that also contains all null sets, by defining the measure to be `0`
on the null sets.
## Main statements
* `completion` is the completion of a measure to all null measurable sets.
* `Measure.ofMeasurable` and `OuterMeasure.toMeasure` are two important ways to define a measure.
## Implementation notes
Given `μ : Measure α`, `μ s` is the value of the *outer measure* applied to `s`.
This conveniently allows us to apply the measure to sets without proving that they are measurable.
We get countable subadditivity for all sets, but only countable additivity for measurable sets.
You often don't want to define a measure via its constructor.
Two ways that are sometimes more convenient:
* `Measure.ofMeasurable` is a way to define a measure by only giving its value on measurable sets
and proving the properties (1) and (2) mentioned above.
* `OuterMeasure.toMeasure` is a way of obtaining a measure from an outer measure by showing that
all measurable sets in the measurable space are Carathéodory measurable.
To prove that two measures are equal, there are multiple options:
* `ext`: two measures are equal if they are equal on all measurable sets.
* `ext_of_generateFrom_of_iUnion`: two measures are equal if they are equal on a π-system generating
the measurable sets, if the π-system contains a spanning increasing sequence of sets where the
measures take finite value (in particular the measures are σ-finite). This is a special case of
the more general `ext_of_generateFrom_of_cover`
* `ext_of_generate_finite`: two finite measures are equal if they are equal on a π-system
generating the measurable sets. This is a special case of `ext_of_generateFrom_of_iUnion` using
`C ∪ {univ}`, but is easier to work with.
A `MeasureSpace` is a class that is a measurable space with a canonical measure.
The measure is denoted `volume`.
## References
* <https://en.wikipedia.org/wiki/Measure_(mathematics)>
* <https://en.wikipedia.org/wiki/Complete_measure>
* <https://en.wikipedia.org/wiki/Almost_everywhere>
## Tags
measure, almost everywhere, measure space, completion, null set, null measurable set
-/
noncomputable section
open Set
open Filter hiding map
open Function MeasurableSpace
open scoped Classical symmDiff
open Topology Filter ENNReal NNReal Interval MeasureTheory
variable {α β γ δ ι R R' : Type*}
namespace MeasureTheory
section
variable {m : MeasurableSpace α} {μ μ₁ μ₂ : Measure α} {s s₁ s₂ t : Set α}
instance ae_isMeasurablyGenerated : IsMeasurablyGenerated (ae μ) :=
⟨fun _s hs =>
let ⟨t, hst, htm, htμ⟩ := exists_measurable_superset_of_null hs
⟨tᶜ, compl_mem_ae_iff.2 htμ, htm.compl, compl_subset_comm.1 hst⟩⟩
#align measure_theory.ae_is_measurably_generated MeasureTheory.ae_isMeasurablyGenerated
/-- See also `MeasureTheory.ae_restrict_uIoc_iff`. -/
theorem ae_uIoc_iff [LinearOrder α] {a b : α} {P : α → Prop} :
(∀ᵐ x ∂μ, x ∈ Ι a b → P x) ↔ (∀ᵐ x ∂μ, x ∈ Ioc a b → P x) ∧ ∀ᵐ x ∂μ, x ∈ Ioc b a → P x := by
simp only [uIoc_eq_union, mem_union, or_imp, eventually_and]
#align measure_theory.ae_uIoc_iff MeasureTheory.ae_uIoc_iff
theorem measure_union (hd : Disjoint s₁ s₂) (h : MeasurableSet s₂) : μ (s₁ ∪ s₂) = μ s₁ + μ s₂ :=
measure_union₀ h.nullMeasurableSet hd.aedisjoint
#align measure_theory.measure_union MeasureTheory.measure_union
theorem measure_union' (hd : Disjoint s₁ s₂) (h : MeasurableSet s₁) : μ (s₁ ∪ s₂) = μ s₁ + μ s₂ :=
measure_union₀' h.nullMeasurableSet hd.aedisjoint
#align measure_theory.measure_union' MeasureTheory.measure_union'
theorem measure_inter_add_diff (s : Set α) (ht : MeasurableSet t) : μ (s ∩ t) + μ (s \ t) = μ s :=
measure_inter_add_diff₀ _ ht.nullMeasurableSet
#align measure_theory.measure_inter_add_diff MeasureTheory.measure_inter_add_diff
theorem measure_diff_add_inter (s : Set α) (ht : MeasurableSet t) : μ (s \ t) + μ (s ∩ t) = μ s :=
(add_comm _ _).trans (measure_inter_add_diff s ht)
#align measure_theory.measure_diff_add_inter MeasureTheory.measure_diff_add_inter
theorem measure_union_add_inter (s : Set α) (ht : MeasurableSet t) :
μ (s ∪ t) + μ (s ∩ t) = μ s + μ t := by
rw [← measure_inter_add_diff (s ∪ t) ht, Set.union_inter_cancel_right, union_diff_right, ←
measure_inter_add_diff s ht]
ac_rfl
#align measure_theory.measure_union_add_inter MeasureTheory.measure_union_add_inter
theorem measure_union_add_inter' (hs : MeasurableSet s) (t : Set α) :
μ (s ∪ t) + μ (s ∩ t) = μ s + μ t := by
rw [union_comm, inter_comm, measure_union_add_inter t hs, add_comm]
#align measure_theory.measure_union_add_inter' MeasureTheory.measure_union_add_inter'
lemma measure_symmDiff_eq (hs : MeasurableSet s) (ht : MeasurableSet t) :
μ (s ∆ t) = μ (s \ t) + μ (t \ s) := by
simpa only [symmDiff_def, sup_eq_union] using measure_union disjoint_sdiff_sdiff (ht.diff hs)
lemma measure_symmDiff_le (s t u : Set α) :
μ (s ∆ u) ≤ μ (s ∆ t) + μ (t ∆ u) :=
le_trans (μ.mono <| symmDiff_triangle s t u) (measure_union_le (s ∆ t) (t ∆ u))
theorem measure_add_measure_compl (h : MeasurableSet s) : μ s + μ sᶜ = μ univ :=
measure_add_measure_compl₀ h.nullMeasurableSet
#align measure_theory.measure_add_measure_compl MeasureTheory.measure_add_measure_compl
theorem measure_biUnion₀ {s : Set β} {f : β → Set α} (hs : s.Countable)
(hd : s.Pairwise (AEDisjoint μ on f)) (h : ∀ b ∈ s, NullMeasurableSet (f b) μ) :
μ (⋃ b ∈ s, f b) = ∑' p : s, μ (f p) := by
haveI := hs.toEncodable
rw [biUnion_eq_iUnion]
exact measure_iUnion₀ (hd.on_injective Subtype.coe_injective fun x => x.2) fun x => h x x.2
#align measure_theory.measure_bUnion₀ MeasureTheory.measure_biUnion₀
theorem measure_biUnion {s : Set β} {f : β → Set α} (hs : s.Countable) (hd : s.PairwiseDisjoint f)
(h : ∀ b ∈ s, MeasurableSet (f b)) : μ (⋃ b ∈ s, f b) = ∑' p : s, μ (f p) :=
measure_biUnion₀ hs hd.aedisjoint fun b hb => (h b hb).nullMeasurableSet
#align measure_theory.measure_bUnion MeasureTheory.measure_biUnion
theorem measure_sUnion₀ {S : Set (Set α)} (hs : S.Countable) (hd : S.Pairwise (AEDisjoint μ))
(h : ∀ s ∈ S, NullMeasurableSet s μ) : μ (⋃₀ S) = ∑' s : S, μ s := by
rw [sUnion_eq_biUnion, measure_biUnion₀ hs hd h]
#align measure_theory.measure_sUnion₀ MeasureTheory.measure_sUnion₀
theorem measure_sUnion {S : Set (Set α)} (hs : S.Countable) (hd : S.Pairwise Disjoint)
(h : ∀ s ∈ S, MeasurableSet s) : μ (⋃₀ S) = ∑' s : S, μ s := by
rw [sUnion_eq_biUnion, measure_biUnion hs hd h]
#align measure_theory.measure_sUnion MeasureTheory.measure_sUnion
theorem measure_biUnion_finset₀ {s : Finset ι} {f : ι → Set α}
(hd : Set.Pairwise (↑s) (AEDisjoint μ on f)) (hm : ∀ b ∈ s, NullMeasurableSet (f b) μ) :
μ (⋃ b ∈ s, f b) = ∑ p ∈ s, μ (f p) := by
rw [← Finset.sum_attach, Finset.attach_eq_univ, ← tsum_fintype]
exact measure_biUnion₀ s.countable_toSet hd hm
#align measure_theory.measure_bUnion_finset₀ MeasureTheory.measure_biUnion_finset₀
theorem measure_biUnion_finset {s : Finset ι} {f : ι → Set α} (hd : PairwiseDisjoint (↑s) f)
(hm : ∀ b ∈ s, MeasurableSet (f b)) : μ (⋃ b ∈ s, f b) = ∑ p ∈ s, μ (f p) :=
measure_biUnion_finset₀ hd.aedisjoint fun b hb => (hm b hb).nullMeasurableSet
#align measure_theory.measure_bUnion_finset MeasureTheory.measure_biUnion_finset
/-- The measure of an a.e. disjoint union (even uncountable) of null-measurable sets is at least
the sum of the measures of the sets. -/
theorem tsum_meas_le_meas_iUnion_of_disjoint₀ {ι : Type*} [MeasurableSpace α] (μ : Measure α)
{As : ι → Set α} (As_mble : ∀ i : ι, NullMeasurableSet (As i) μ)
(As_disj : Pairwise (AEDisjoint μ on As)) : (∑' i, μ (As i)) ≤ μ (⋃ i, As i) := by
rw [ENNReal.tsum_eq_iSup_sum, iSup_le_iff]
intro s
simp only [← measure_biUnion_finset₀ (fun _i _hi _j _hj hij => As_disj hij) fun i _ => As_mble i]
gcongr
exact iUnion_subset fun _ ↦ Subset.rfl
/-- The measure of a disjoint union (even uncountable) of measurable sets is at least the sum of
the measures of the sets. -/
theorem tsum_meas_le_meas_iUnion_of_disjoint {ι : Type*} [MeasurableSpace α] (μ : Measure α)
{As : ι → Set α} (As_mble : ∀ i : ι, MeasurableSet (As i))
(As_disj : Pairwise (Disjoint on As)) : (∑' i, μ (As i)) ≤ μ (⋃ i, As i) :=
tsum_meas_le_meas_iUnion_of_disjoint₀ μ (fun i ↦ (As_mble i).nullMeasurableSet)
(fun _ _ h ↦ Disjoint.aedisjoint (As_disj h))
#align measure_theory.tsum_meas_le_meas_Union_of_disjoint MeasureTheory.tsum_meas_le_meas_iUnion_of_disjoint
/-- If `s` is a countable set, then the measure of its preimage can be found as the sum of measures
of the fibers `f ⁻¹' {y}`. -/
theorem tsum_measure_preimage_singleton {s : Set β} (hs : s.Countable) {f : α → β}
(hf : ∀ y ∈ s, MeasurableSet (f ⁻¹' {y})) : (∑' b : s, μ (f ⁻¹' {↑b})) = μ (f ⁻¹' s) := by
rw [← Set.biUnion_preimage_singleton, measure_biUnion hs (pairwiseDisjoint_fiber f s) hf]
#align measure_theory.tsum_measure_preimage_singleton MeasureTheory.tsum_measure_preimage_singleton
lemma measure_preimage_eq_zero_iff_of_countable {s : Set β} {f : α → β} (hs : s.Countable) :
μ (f ⁻¹' s) = 0 ↔ ∀ x ∈ s, μ (f ⁻¹' {x}) = 0 := by
rw [← biUnion_preimage_singleton, measure_biUnion_null_iff hs]
/-- If `s` is a `Finset`, then the measure of its preimage can be found as the sum of measures
of the fibers `f ⁻¹' {y}`. -/
theorem sum_measure_preimage_singleton (s : Finset β) {f : α → β}
(hf : ∀ y ∈ s, MeasurableSet (f ⁻¹' {y})) : (∑ b ∈ s, μ (f ⁻¹' {b})) = μ (f ⁻¹' ↑s) := by
simp only [← measure_biUnion_finset (pairwiseDisjoint_fiber f s) hf,
Finset.set_biUnion_preimage_singleton]
#align measure_theory.sum_measure_preimage_singleton MeasureTheory.sum_measure_preimage_singleton
theorem measure_diff_null' (h : μ (s₁ ∩ s₂) = 0) : μ (s₁ \ s₂) = μ s₁ :=
measure_congr <| diff_ae_eq_self.2 h
#align measure_theory.measure_diff_null' MeasureTheory.measure_diff_null'
theorem measure_add_diff (hs : MeasurableSet s) (t : Set α) : μ s + μ (t \ s) = μ (s ∪ t) := by
rw [← measure_union' disjoint_sdiff_right hs, union_diff_self]
#align measure_theory.measure_add_diff MeasureTheory.measure_add_diff
theorem measure_diff' (s : Set α) (hm : MeasurableSet t) (h_fin : μ t ≠ ∞) :
μ (s \ t) = μ (s ∪ t) - μ t :=
Eq.symm <| ENNReal.sub_eq_of_add_eq h_fin <| by rw [add_comm, measure_add_diff hm, union_comm]
#align measure_theory.measure_diff' MeasureTheory.measure_diff'
theorem measure_diff (h : s₂ ⊆ s₁) (h₂ : MeasurableSet s₂) (h_fin : μ s₂ ≠ ∞) :
μ (s₁ \ s₂) = μ s₁ - μ s₂ := by rw [measure_diff' _ h₂ h_fin, union_eq_self_of_subset_right h]
#align measure_theory.measure_diff MeasureTheory.measure_diff
theorem le_measure_diff : μ s₁ - μ s₂ ≤ μ (s₁ \ s₂) :=
tsub_le_iff_left.2 <| (measure_le_inter_add_diff μ s₁ s₂).trans <| by
gcongr; apply inter_subset_right
#align measure_theory.le_measure_diff MeasureTheory.le_measure_diff
/-- If the measure of the symmetric difference of two sets is finite,
then one has infinite measure if and only if the other one does. -/
theorem measure_eq_top_iff_of_symmDiff (hμst : μ (s ∆ t) ≠ ∞) : μ s = ∞ ↔ μ t = ∞ := by
suffices h : ∀ u v, μ (u ∆ v) ≠ ∞ → μ u = ∞ → μ v = ∞
from ⟨h s t hμst, h t s (symmDiff_comm s t ▸ hμst)⟩
intro u v hμuv hμu
by_contra! hμv
apply hμuv
rw [Set.symmDiff_def, eq_top_iff]
calc
∞ = μ u - μ v := (WithTop.sub_eq_top_iff.2 ⟨hμu, hμv⟩).symm
_ ≤ μ (u \ v) := le_measure_diff
_ ≤ μ (u \ v ∪ v \ u) := measure_mono subset_union_left
/-- If the measure of the symmetric difference of two sets is finite,
then one has finite measure if and only if the other one does. -/
theorem measure_ne_top_iff_of_symmDiff (hμst : μ (s ∆ t) ≠ ∞) : μ s ≠ ∞ ↔ μ t ≠ ∞ :=
(measure_eq_top_iff_of_symmDiff hμst).ne
theorem measure_diff_lt_of_lt_add (hs : MeasurableSet s) (hst : s ⊆ t) (hs' : μ s ≠ ∞) {ε : ℝ≥0∞}
(h : μ t < μ s + ε) : μ (t \ s) < ε := by
rw [measure_diff hst hs hs']; rw [add_comm] at h
exact ENNReal.sub_lt_of_lt_add (measure_mono hst) h
#align measure_theory.measure_diff_lt_of_lt_add MeasureTheory.measure_diff_lt_of_lt_add
theorem measure_diff_le_iff_le_add (hs : MeasurableSet s) (hst : s ⊆ t) (hs' : μ s ≠ ∞) {ε : ℝ≥0∞} :
μ (t \ s) ≤ ε ↔ μ t ≤ μ s + ε := by rw [measure_diff hst hs hs', tsub_le_iff_left]
#align measure_theory.measure_diff_le_iff_le_add MeasureTheory.measure_diff_le_iff_le_add
theorem measure_eq_measure_of_null_diff {s t : Set α} (hst : s ⊆ t) (h_nulldiff : μ (t \ s) = 0) :
μ s = μ t := measure_congr <|
EventuallyLE.antisymm (HasSubset.Subset.eventuallyLE hst) (ae_le_set.mpr h_nulldiff)
#align measure_theory.measure_eq_measure_of_null_diff MeasureTheory.measure_eq_measure_of_null_diff
theorem measure_eq_measure_of_between_null_diff {s₁ s₂ s₃ : Set α} (h12 : s₁ ⊆ s₂) (h23 : s₂ ⊆ s₃)
(h_nulldiff : μ (s₃ \ s₁) = 0) : μ s₁ = μ s₂ ∧ μ s₂ = μ s₃ := by
have le12 : μ s₁ ≤ μ s₂ := measure_mono h12
have le23 : μ s₂ ≤ μ s₃ := measure_mono h23
have key : μ s₃ ≤ μ s₁ :=
calc
μ s₃ = μ (s₃ \ s₁ ∪ s₁) := by rw [diff_union_of_subset (h12.trans h23)]
_ ≤ μ (s₃ \ s₁) + μ s₁ := measure_union_le _ _
_ = μ s₁ := by simp only [h_nulldiff, zero_add]
exact ⟨le12.antisymm (le23.trans key), le23.antisymm (key.trans le12)⟩
#align measure_theory.measure_eq_measure_of_between_null_diff MeasureTheory.measure_eq_measure_of_between_null_diff
theorem measure_eq_measure_smaller_of_between_null_diff {s₁ s₂ s₃ : Set α} (h12 : s₁ ⊆ s₂)
(h23 : s₂ ⊆ s₃) (h_nulldiff : μ (s₃ \ s₁) = 0) : μ s₁ = μ s₂ :=
(measure_eq_measure_of_between_null_diff h12 h23 h_nulldiff).1
#align measure_theory.measure_eq_measure_smaller_of_between_null_diff MeasureTheory.measure_eq_measure_smaller_of_between_null_diff
theorem measure_eq_measure_larger_of_between_null_diff {s₁ s₂ s₃ : Set α} (h12 : s₁ ⊆ s₂)
(h23 : s₂ ⊆ s₃) (h_nulldiff : μ (s₃ \ s₁) = 0) : μ s₂ = μ s₃ :=
(measure_eq_measure_of_between_null_diff h12 h23 h_nulldiff).2
#align measure_theory.measure_eq_measure_larger_of_between_null_diff MeasureTheory.measure_eq_measure_larger_of_between_null_diff
lemma measure_compl₀ (h : NullMeasurableSet s μ) (hs : μ s ≠ ∞) :
μ sᶜ = μ Set.univ - μ s := by
rw [← measure_add_measure_compl₀ h, ENNReal.add_sub_cancel_left hs]
theorem measure_compl (h₁ : MeasurableSet s) (h_fin : μ s ≠ ∞) : μ sᶜ = μ univ - μ s :=
measure_compl₀ h₁.nullMeasurableSet h_fin
#align measure_theory.measure_compl MeasureTheory.measure_compl
lemma measure_inter_conull' (ht : μ (s \ t) = 0) : μ (s ∩ t) = μ s := by
rw [← diff_compl, measure_diff_null']; rwa [← diff_eq]
lemma measure_inter_conull (ht : μ tᶜ = 0) : μ (s ∩ t) = μ s := by
rw [← diff_compl, measure_diff_null ht]
@[simp]
theorem union_ae_eq_left_iff_ae_subset : (s ∪ t : Set α) =ᵐ[μ] s ↔ t ≤ᵐ[μ] s := by
rw [ae_le_set]
refine
⟨fun h => by simpa only [union_diff_left] using (ae_eq_set.mp h).1, fun h =>
eventuallyLE_antisymm_iff.mpr
⟨by rwa [ae_le_set, union_diff_left],
HasSubset.Subset.eventuallyLE subset_union_left⟩⟩
#align measure_theory.union_ae_eq_left_iff_ae_subset MeasureTheory.union_ae_eq_left_iff_ae_subset
@[simp]
theorem union_ae_eq_right_iff_ae_subset : (s ∪ t : Set α) =ᵐ[μ] t ↔ s ≤ᵐ[μ] t := by
rw [union_comm, union_ae_eq_left_iff_ae_subset]
#align measure_theory.union_ae_eq_right_iff_ae_subset MeasureTheory.union_ae_eq_right_iff_ae_subset
theorem ae_eq_of_ae_subset_of_measure_ge (h₁ : s ≤ᵐ[μ] t) (h₂ : μ t ≤ μ s) (hsm : MeasurableSet s)
(ht : μ t ≠ ∞) : s =ᵐ[μ] t := by
refine eventuallyLE_antisymm_iff.mpr ⟨h₁, ae_le_set.mpr ?_⟩
replace h₂ : μ t = μ s := h₂.antisymm (measure_mono_ae h₁)
replace ht : μ s ≠ ∞ := h₂ ▸ ht
rw [measure_diff' t hsm ht, measure_congr (union_ae_eq_left_iff_ae_subset.mpr h₁), h₂, tsub_self]
#align measure_theory.ae_eq_of_ae_subset_of_measure_ge MeasureTheory.ae_eq_of_ae_subset_of_measure_ge
/-- If `s ⊆ t`, `μ t ≤ μ s`, `μ t ≠ ∞`, and `s` is measurable, then `s =ᵐ[μ] t`. -/
theorem ae_eq_of_subset_of_measure_ge (h₁ : s ⊆ t) (h₂ : μ t ≤ μ s) (hsm : MeasurableSet s)
(ht : μ t ≠ ∞) : s =ᵐ[μ] t :=
ae_eq_of_ae_subset_of_measure_ge (HasSubset.Subset.eventuallyLE h₁) h₂ hsm ht
#align measure_theory.ae_eq_of_subset_of_measure_ge MeasureTheory.ae_eq_of_subset_of_measure_ge
theorem measure_iUnion_congr_of_subset [Countable β] {s : β → Set α} {t : β → Set α}
(hsub : ∀ b, s b ⊆ t b) (h_le : ∀ b, μ (t b) ≤ μ (s b)) : μ (⋃ b, s b) = μ (⋃ b, t b) := by
rcases Classical.em (∃ b, μ (t b) = ∞) with (⟨b, hb⟩ | htop)
· calc
μ (⋃ b, s b) = ∞ := top_unique (hb ▸ (h_le b).trans <| measure_mono <| subset_iUnion _ _)
_ = μ (⋃ b, t b) := Eq.symm <| top_unique <| hb ▸ measure_mono (subset_iUnion _ _)
push_neg at htop
refine le_antisymm (measure_mono (iUnion_mono hsub)) ?_
set M := toMeasurable μ
have H : ∀ b, (M (t b) ∩ M (⋃ b, s b) : Set α) =ᵐ[μ] M (t b) := by
refine fun b => ae_eq_of_subset_of_measure_ge inter_subset_left ?_ ?_ ?_
· calc
μ (M (t b)) = μ (t b) := measure_toMeasurable _
_ ≤ μ (s b) := h_le b
_ ≤ μ (M (t b) ∩ M (⋃ b, s b)) :=
measure_mono <|
subset_inter ((hsub b).trans <| subset_toMeasurable _ _)
((subset_iUnion _ _).trans <| subset_toMeasurable _ _)
· exact (measurableSet_toMeasurable _ _).inter (measurableSet_toMeasurable _ _)
· rw [measure_toMeasurable]
exact htop b
calc
μ (⋃ b, t b) ≤ μ (⋃ b, M (t b)) := measure_mono (iUnion_mono fun b => subset_toMeasurable _ _)
_ = μ (⋃ b, M (t b) ∩ M (⋃ b, s b)) := measure_congr (EventuallyEq.countable_iUnion H).symm
_ ≤ μ (M (⋃ b, s b)) := measure_mono (iUnion_subset fun b => inter_subset_right)
_ = μ (⋃ b, s b) := measure_toMeasurable _
#align measure_theory.measure_Union_congr_of_subset MeasureTheory.measure_iUnion_congr_of_subset
theorem measure_union_congr_of_subset {t₁ t₂ : Set α} (hs : s₁ ⊆ s₂) (hsμ : μ s₂ ≤ μ s₁)
(ht : t₁ ⊆ t₂) (htμ : μ t₂ ≤ μ t₁) : μ (s₁ ∪ t₁) = μ (s₂ ∪ t₂) := by
rw [union_eq_iUnion, union_eq_iUnion]
exact measure_iUnion_congr_of_subset (Bool.forall_bool.2 ⟨ht, hs⟩) (Bool.forall_bool.2 ⟨htμ, hsμ⟩)
#align measure_theory.measure_union_congr_of_subset MeasureTheory.measure_union_congr_of_subset
@[simp]
theorem measure_iUnion_toMeasurable [Countable β] (s : β → Set α) :
μ (⋃ b, toMeasurable μ (s b)) = μ (⋃ b, s b) :=
Eq.symm <|
measure_iUnion_congr_of_subset (fun _b => subset_toMeasurable _ _) fun _b =>
(measure_toMeasurable _).le
#align measure_theory.measure_Union_to_measurable MeasureTheory.measure_iUnion_toMeasurable
theorem measure_biUnion_toMeasurable {I : Set β} (hc : I.Countable) (s : β → Set α) :
μ (⋃ b ∈ I, toMeasurable μ (s b)) = μ (⋃ b ∈ I, s b) := by
haveI := hc.toEncodable
simp only [biUnion_eq_iUnion, measure_iUnion_toMeasurable]
#align measure_theory.measure_bUnion_to_measurable MeasureTheory.measure_biUnion_toMeasurable
@[simp]
theorem measure_toMeasurable_union : μ (toMeasurable μ s ∪ t) = μ (s ∪ t) :=
Eq.symm <|
measure_union_congr_of_subset (subset_toMeasurable _ _) (measure_toMeasurable _).le Subset.rfl
le_rfl
#align measure_theory.measure_to_measurable_union MeasureTheory.measure_toMeasurable_union
@[simp]
theorem measure_union_toMeasurable : μ (s ∪ toMeasurable μ t) = μ (s ∪ t) :=
Eq.symm <|
measure_union_congr_of_subset Subset.rfl le_rfl (subset_toMeasurable _ _)
(measure_toMeasurable _).le
#align measure_theory.measure_union_to_measurable MeasureTheory.measure_union_toMeasurable
theorem sum_measure_le_measure_univ {s : Finset ι} {t : ι → Set α}
(h : ∀ i ∈ s, MeasurableSet (t i)) (H : Set.PairwiseDisjoint (↑s) t) :
(∑ i ∈ s, μ (t i)) ≤ μ (univ : Set α) := by
rw [← measure_biUnion_finset H h]
exact measure_mono (subset_univ _)
#align measure_theory.sum_measure_le_measure_univ MeasureTheory.sum_measure_le_measure_univ
theorem tsum_measure_le_measure_univ {s : ι → Set α} (hs : ∀ i, MeasurableSet (s i))
(H : Pairwise (Disjoint on s)) : (∑' i, μ (s i)) ≤ μ (univ : Set α) := by
rw [ENNReal.tsum_eq_iSup_sum]
exact iSup_le fun s =>
sum_measure_le_measure_univ (fun i _hi => hs i) fun i _hi j _hj hij => H hij
#align measure_theory.tsum_measure_le_measure_univ MeasureTheory.tsum_measure_le_measure_univ
/-- Pigeonhole principle for measure spaces: if `∑' i, μ (s i) > μ univ`, then
one of the intersections `s i ∩ s j` is not empty. -/
theorem exists_nonempty_inter_of_measure_univ_lt_tsum_measure {m : MeasurableSpace α}
(μ : Measure α) {s : ι → Set α} (hs : ∀ i, MeasurableSet (s i))
(H : μ (univ : Set α) < ∑' i, μ (s i)) : ∃ i j, i ≠ j ∧ (s i ∩ s j).Nonempty := by
contrapose! H
apply tsum_measure_le_measure_univ hs
intro i j hij
exact disjoint_iff_inter_eq_empty.mpr (H i j hij)
#align measure_theory.exists_nonempty_inter_of_measure_univ_lt_tsum_measure MeasureTheory.exists_nonempty_inter_of_measure_univ_lt_tsum_measure
/-- Pigeonhole principle for measure spaces: if `s` is a `Finset` and
`∑ i ∈ s, μ (t i) > μ univ`, then one of the intersections `t i ∩ t j` is not empty. -/
theorem exists_nonempty_inter_of_measure_univ_lt_sum_measure {m : MeasurableSpace α} (μ : Measure α)
{s : Finset ι} {t : ι → Set α} (h : ∀ i ∈ s, MeasurableSet (t i))
(H : μ (univ : Set α) < ∑ i ∈ s, μ (t i)) :
∃ i ∈ s, ∃ j ∈ s, ∃ _h : i ≠ j, (t i ∩ t j).Nonempty := by
contrapose! H
apply sum_measure_le_measure_univ h
intro i hi j hj hij
exact disjoint_iff_inter_eq_empty.mpr (H i hi j hj hij)
#align measure_theory.exists_nonempty_inter_of_measure_univ_lt_sum_measure MeasureTheory.exists_nonempty_inter_of_measure_univ_lt_sum_measure
/-- If two sets `s` and `t` are included in a set `u`, and `μ s + μ t > μ u`,
then `s` intersects `t`. Version assuming that `t` is measurable. -/
theorem nonempty_inter_of_measure_lt_add {m : MeasurableSpace α} (μ : Measure α) {s t u : Set α}
(ht : MeasurableSet t) (h's : s ⊆ u) (h't : t ⊆ u) (h : μ u < μ s + μ t) :
(s ∩ t).Nonempty := by
rw [← Set.not_disjoint_iff_nonempty_inter]
contrapose! h
calc
μ s + μ t = μ (s ∪ t) := (measure_union h ht).symm
_ ≤ μ u := measure_mono (union_subset h's h't)
#align measure_theory.nonempty_inter_of_measure_lt_add MeasureTheory.nonempty_inter_of_measure_lt_add
/-- If two sets `s` and `t` are included in a set `u`, and `μ s + μ t > μ u`,
then `s` intersects `t`. Version assuming that `s` is measurable. -/
theorem nonempty_inter_of_measure_lt_add' {m : MeasurableSpace α} (μ : Measure α) {s t u : Set α}
(hs : MeasurableSet s) (h's : s ⊆ u) (h't : t ⊆ u) (h : μ u < μ s + μ t) :
(s ∩ t).Nonempty := by
rw [add_comm] at h
rw [inter_comm]
exact nonempty_inter_of_measure_lt_add μ hs h't h's h
#align measure_theory.nonempty_inter_of_measure_lt_add' MeasureTheory.nonempty_inter_of_measure_lt_add'
/-- Continuity from below: the measure of the union of a directed sequence of (not necessarily
-measurable) sets is the supremum of the measures. -/
theorem measure_iUnion_eq_iSup [Countable ι] {s : ι → Set α} (hd : Directed (· ⊆ ·) s) :
μ (⋃ i, s i) = ⨆ i, μ (s i) := by
cases nonempty_encodable ι
-- WLOG, `ι = ℕ`
generalize ht : Function.extend Encodable.encode s ⊥ = t
replace hd : Directed (· ⊆ ·) t := ht ▸ hd.extend_bot Encodable.encode_injective
suffices μ (⋃ n, t n) = ⨆ n, μ (t n) by
simp only [← ht, Function.apply_extend μ, ← iSup_eq_iUnion,
iSup_extend_bot Encodable.encode_injective, (· ∘ ·), Pi.bot_apply, bot_eq_empty,
measure_empty] at this
exact this.trans (iSup_extend_bot Encodable.encode_injective _)
clear! ι
-- The `≥` inequality is trivial
refine le_antisymm ?_ (iSup_le fun i => measure_mono <| subset_iUnion _ _)
-- Choose `T n ⊇ t n` of the same measure, put `Td n = disjointed T`
set T : ℕ → Set α := fun n => toMeasurable μ (t n)
set Td : ℕ → Set α := disjointed T
have hm : ∀ n, MeasurableSet (Td n) :=
MeasurableSet.disjointed fun n => measurableSet_toMeasurable _ _
calc
μ (⋃ n, t n) ≤ μ (⋃ n, T n) := measure_mono (iUnion_mono fun i => subset_toMeasurable _ _)
_ = μ (⋃ n, Td n) := by rw [iUnion_disjointed]
_ ≤ ∑' n, μ (Td n) := measure_iUnion_le _
_ = ⨆ I : Finset ℕ, ∑ n ∈ I, μ (Td n) := ENNReal.tsum_eq_iSup_sum
_ ≤ ⨆ n, μ (t n) := iSup_le fun I => by
rcases hd.finset_le I with ⟨N, hN⟩
calc
(∑ n ∈ I, μ (Td n)) = μ (⋃ n ∈ I, Td n) :=
(measure_biUnion_finset ((disjoint_disjointed T).set_pairwise I) fun n _ => hm n).symm
_ ≤ μ (⋃ n ∈ I, T n) := measure_mono (iUnion₂_mono fun n _hn => disjointed_subset _ _)
_ = μ (⋃ n ∈ I, t n) := measure_biUnion_toMeasurable I.countable_toSet _
_ ≤ μ (t N) := measure_mono (iUnion₂_subset hN)
_ ≤ ⨆ n, μ (t n) := le_iSup (μ ∘ t) N
#align measure_theory.measure_Union_eq_supr MeasureTheory.measure_iUnion_eq_iSup
/-- Continuity from below: the measure of the union of a sequence of
(not necessarily measurable) sets is the supremum of the measures of the partial unions. -/
theorem measure_iUnion_eq_iSup' {α ι : Type*} [MeasurableSpace α] {μ : Measure α}
[Countable ι] [Preorder ι] [IsDirected ι (· ≤ ·)]
{f : ι → Set α} : μ (⋃ i, f i) = ⨆ i, μ (Accumulate f i) := by
have hd : Directed (· ⊆ ·) (Accumulate f) := by
intro i j
rcases directed_of (· ≤ ·) i j with ⟨k, rik, rjk⟩
exact ⟨k, biUnion_subset_biUnion_left fun l rli ↦ le_trans rli rik,
biUnion_subset_biUnion_left fun l rlj ↦ le_trans rlj rjk⟩
rw [← iUnion_accumulate]
exact measure_iUnion_eq_iSup hd
theorem measure_biUnion_eq_iSup {s : ι → Set α} {t : Set ι} (ht : t.Countable)
(hd : DirectedOn ((· ⊆ ·) on s) t) : μ (⋃ i ∈ t, s i) = ⨆ i ∈ t, μ (s i) := by
haveI := ht.toEncodable
rw [biUnion_eq_iUnion, measure_iUnion_eq_iSup hd.directed_val, ← iSup_subtype'']
#align measure_theory.measure_bUnion_eq_supr MeasureTheory.measure_biUnion_eq_iSup
/-- Continuity from above: the measure of the intersection of a decreasing sequence of measurable
sets is the infimum of the measures. -/
theorem measure_iInter_eq_iInf [Countable ι] {s : ι → Set α} (h : ∀ i, MeasurableSet (s i))
(hd : Directed (· ⊇ ·) s) (hfin : ∃ i, μ (s i) ≠ ∞) : μ (⋂ i, s i) = ⨅ i, μ (s i) := by
rcases hfin with ⟨k, hk⟩
have : ∀ t ⊆ s k, μ t ≠ ∞ := fun t ht => ne_top_of_le_ne_top hk (measure_mono ht)
rw [← ENNReal.sub_sub_cancel hk (iInf_le _ k), ENNReal.sub_iInf, ←
ENNReal.sub_sub_cancel hk (measure_mono (iInter_subset _ k)), ←
measure_diff (iInter_subset _ k) (MeasurableSet.iInter h) (this _ (iInter_subset _ k)),
diff_iInter, measure_iUnion_eq_iSup]
· congr 1
refine le_antisymm (iSup_mono' fun i => ?_) (iSup_mono fun i => ?_)
· rcases hd i k with ⟨j, hji, hjk⟩
use j
rw [← measure_diff hjk (h _) (this _ hjk)]
gcongr
· rw [tsub_le_iff_right, ← measure_union, Set.union_comm]
· exact measure_mono (diff_subset_iff.1 Subset.rfl)
· apply disjoint_sdiff_left
· apply h i
· exact hd.mono_comp _ fun _ _ => diff_subset_diff_right
#align measure_theory.measure_Inter_eq_infi MeasureTheory.measure_iInter_eq_iInf
/-- Continuity from above: the measure of the intersection of a sequence of
measurable sets is the infimum of the measures of the partial intersections. -/
theorem measure_iInter_eq_iInf' {α ι : Type*} [MeasurableSpace α] {μ : Measure α}
[Countable ι] [Preorder ι] [IsDirected ι (· ≤ ·)]
{f : ι → Set α} (h : ∀ i, MeasurableSet (f i)) (hfin : ∃ i, μ (f i) ≠ ∞) :
μ (⋂ i, f i) = ⨅ i, μ (⋂ j ≤ i, f j) := by
let s := fun i ↦ ⋂ j ≤ i, f j
have iInter_eq : ⋂ i, f i = ⋂ i, s i := by
ext x; simp [s]; constructor
· exact fun h _ j _ ↦ h j
· intro h i
rcases directed_of (· ≤ ·) i i with ⟨j, rij, -⟩
exact h j i rij
have ms : ∀ i, MeasurableSet (s i) :=
fun i ↦ MeasurableSet.biInter (countable_univ.mono <| subset_univ _) fun i _ ↦ h i
have hd : Directed (· ⊇ ·) s := by
intro i j
rcases directed_of (· ≤ ·) i j with ⟨k, rik, rjk⟩
exact ⟨k, biInter_subset_biInter_left fun j rji ↦ le_trans rji rik,
biInter_subset_biInter_left fun i rij ↦ le_trans rij rjk⟩
have hfin' : ∃ i, μ (s i) ≠ ∞ := by
rcases hfin with ⟨i, hi⟩
rcases directed_of (· ≤ ·) i i with ⟨j, rij, -⟩
exact ⟨j, ne_top_of_le_ne_top hi <| measure_mono <| biInter_subset_of_mem rij⟩
exact iInter_eq ▸ measure_iInter_eq_iInf ms hd hfin'
/-- Continuity from below: the measure of the union of an increasing sequence of (not necessarily
measurable) sets is the limit of the measures. -/
theorem tendsto_measure_iUnion [Preorder ι] [IsDirected ι (· ≤ ·)] [Countable ι]
{s : ι → Set α} (hm : Monotone s) : Tendsto (μ ∘ s) atTop (𝓝 (μ (⋃ n, s n))) := by
rw [measure_iUnion_eq_iSup hm.directed_le]
exact tendsto_atTop_iSup fun n m hnm => measure_mono <| hm hnm
#align measure_theory.tendsto_measure_Union MeasureTheory.tendsto_measure_iUnion
/-- Continuity from below: the measure of the union of a sequence of (not necessarily measurable)
sets is the limit of the measures of the partial unions. -/
theorem tendsto_measure_iUnion' {α ι : Type*} [MeasurableSpace α] {μ : Measure α} [Countable ι]
[Preorder ι] [IsDirected ι (· ≤ ·)] {f : ι → Set α} :
Tendsto (fun i ↦ μ (Accumulate f i)) atTop (𝓝 (μ (⋃ i, f i))) := by
rw [measure_iUnion_eq_iSup']
exact tendsto_atTop_iSup fun i j hij ↦ by gcongr
/-- Continuity from above: the measure of the intersection of a decreasing sequence of measurable
sets is the limit of the measures. -/
theorem tendsto_measure_iInter [Countable ι] [Preorder ι] [IsDirected ι (· ≤ ·)] {s : ι → Set α}
(hs : ∀ n, MeasurableSet (s n)) (hm : Antitone s) (hf : ∃ i, μ (s i) ≠ ∞) :
Tendsto (μ ∘ s) atTop (𝓝 (μ (⋂ n, s n))) := by
rw [measure_iInter_eq_iInf hs hm.directed_ge hf]
exact tendsto_atTop_iInf fun n m hnm => measure_mono <| hm hnm
#align measure_theory.tendsto_measure_Inter MeasureTheory.tendsto_measure_iInter
/-- Continuity from above: the measure of the intersection of a sequence of measurable
sets such that one has finite measure is the limit of the measures of the partial intersections. -/
theorem tendsto_measure_iInter' {α ι : Type*} [MeasurableSpace α] {μ : Measure α} [Countable ι]
[Preorder ι] [IsDirected ι (· ≤ ·)] {f : ι → Set α} (hm : ∀ i, MeasurableSet (f i))
(hf : ∃ i, μ (f i) ≠ ∞) :
Tendsto (fun i ↦ μ (⋂ j ∈ {j | j ≤ i}, f j)) atTop (𝓝 (μ (⋂ i, f i))) := by
rw [measure_iInter_eq_iInf' hm hf]
exact tendsto_atTop_iInf
fun i j hij ↦ measure_mono <| biInter_subset_biInter_left fun k hki ↦ le_trans hki hij
/-- The measure of the intersection of a decreasing sequence of measurable
sets indexed by a linear order with first countable topology is the limit of the measures. -/
theorem tendsto_measure_biInter_gt {ι : Type*} [LinearOrder ι] [TopologicalSpace ι]
[OrderTopology ι] [DenselyOrdered ι] [FirstCountableTopology ι] {s : ι → Set α}
{a : ι} (hs : ∀ r > a, MeasurableSet (s r)) (hm : ∀ i j, a < i → i ≤ j → s i ⊆ s j)
(hf : ∃ r > a, μ (s r) ≠ ∞) : Tendsto (μ ∘ s) (𝓝[Ioi a] a) (𝓝 (μ (⋂ r > a, s r))) := by
refine tendsto_order.2 ⟨fun l hl => ?_, fun L hL => ?_⟩
· filter_upwards [self_mem_nhdsWithin (s := Ioi a)] with r hr using hl.trans_le
(measure_mono (biInter_subset_of_mem hr))
obtain ⟨u, u_anti, u_pos, u_lim⟩ :
∃ u : ℕ → ι, StrictAnti u ∧ (∀ n : ℕ, a < u n) ∧ Tendsto u atTop (𝓝 a) := by
rcases hf with ⟨r, ar, _⟩
rcases exists_seq_strictAnti_tendsto' ar with ⟨w, w_anti, w_mem, w_lim⟩
exact ⟨w, w_anti, fun n => (w_mem n).1, w_lim⟩
have A : Tendsto (μ ∘ s ∘ u) atTop (𝓝 (μ (⋂ n, s (u n)))) := by
refine tendsto_measure_iInter (fun n => hs _ (u_pos n)) ?_ ?_
· intro m n hmn
exact hm _ _ (u_pos n) (u_anti.antitone hmn)
· rcases hf with ⟨r, rpos, hr⟩
obtain ⟨n, hn⟩ : ∃ n : ℕ, u n < r := ((tendsto_order.1 u_lim).2 r rpos).exists
refine ⟨n, ne_of_lt (lt_of_le_of_lt ?_ hr.lt_top)⟩
exact measure_mono (hm _ _ (u_pos n) hn.le)
have B : ⋂ n, s (u n) = ⋂ r > a, s r := by
apply Subset.antisymm
· simp only [subset_iInter_iff, gt_iff_lt]
intro r rpos
obtain ⟨n, hn⟩ : ∃ n, u n < r := ((tendsto_order.1 u_lim).2 _ rpos).exists
exact Subset.trans (iInter_subset _ n) (hm (u n) r (u_pos n) hn.le)
· simp only [subset_iInter_iff, gt_iff_lt]
intro n
apply biInter_subset_of_mem
exact u_pos n
rw [B] at A
obtain ⟨n, hn⟩ : ∃ n, μ (s (u n)) < L := ((tendsto_order.1 A).2 _ hL).exists
have : Ioc a (u n) ∈ 𝓝[>] a := Ioc_mem_nhdsWithin_Ioi ⟨le_rfl, u_pos n⟩
filter_upwards [this] with r hr using lt_of_le_of_lt (measure_mono (hm _ _ hr.1 hr.2)) hn
#align measure_theory.tendsto_measure_bInter_gt MeasureTheory.tendsto_measure_biInter_gt
/-- One direction of the **Borel-Cantelli lemma** (sometimes called the "*first* Borel-Cantelli
lemma"): if (sᵢ) is a sequence of sets such that `∑ μ sᵢ` is finite, then the limit superior of the
`sᵢ` is a null set.
Note: for the *second* Borel-Cantelli lemma (applying to independent sets in a probability space),
see `ProbabilityTheory.measure_limsup_eq_one`. -/
| Mathlib/MeasureTheory/Measure/MeasureSpace.lean | 652 | 674 | theorem measure_limsup_eq_zero {s : ℕ → Set α} (hs : (∑' i, μ (s i)) ≠ ∞) :
μ (limsup s atTop) = 0 := by |
-- First we replace the sequence `sₙ` with a sequence of measurable sets `tₙ ⊇ sₙ` of the same
-- measure.
set t : ℕ → Set α := fun n => toMeasurable μ (s n)
have ht : (∑' i, μ (t i)) ≠ ∞ := by simpa only [t, measure_toMeasurable] using hs
suffices μ (limsup t atTop) = 0 by
have A : s ≤ t := fun n => subset_toMeasurable μ (s n)
-- TODO default args fail
exact measure_mono_null (limsup_le_limsup (eventually_of_forall (Pi.le_def.mp A))) this
-- Next we unfold `limsup` for sets and replace equality with an inequality
simp only [limsup_eq_iInf_iSup_of_nat', Set.iInf_eq_iInter, Set.iSup_eq_iUnion, ←
nonpos_iff_eq_zero]
-- Finally, we estimate `μ (⋃ i, t (i + n))` by `∑ i', μ (t (i + n))`
refine
le_of_tendsto_of_tendsto'
(tendsto_measure_iInter
(fun i => MeasurableSet.iUnion fun b => measurableSet_toMeasurable _ _) ?_
⟨0, ne_top_of_le_ne_top ht (measure_iUnion_le t)⟩)
(ENNReal.tendsto_sum_nat_add (μ ∘ t) ht) fun n => measure_iUnion_le _
intro n m hnm x
simp only [Set.mem_iUnion]
exact fun ⟨i, hi⟩ => ⟨i + (m - n), by simpa only [add_assoc, tsub_add_cancel_of_le hnm] using hi⟩
|
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Johan Commelin, Mario Carneiro
-/
import Mathlib.Algebra.Algebra.Tower
import Mathlib.Algebra.GroupWithZero.Divisibility
import Mathlib.Algebra.Regular.Pow
import Mathlib.Algebra.MonoidAlgebra.Support
import Mathlib.Data.Finsupp.Antidiagonal
import Mathlib.Order.SymmDiff
import Mathlib.RingTheory.Adjoin.Basic
#align_import data.mv_polynomial.basic from "leanprover-community/mathlib"@"c8734e8953e4b439147bd6f75c2163f6d27cdce6"
/-!
# Multivariate polynomials
This file defines polynomial rings over a base ring (or even semiring),
with variables from a general type `σ` (which could be infinite).
## Important definitions
Let `R` be a commutative ring (or a semiring) and let `σ` be an arbitrary
type. This file creates the type `MvPolynomial σ R`, which mathematicians
might denote $R[X_i : i \in σ]$. It is the type of multivariate
(a.k.a. multivariable) polynomials, with variables
corresponding to the terms in `σ`, and coefficients in `R`.
### Notation
In the definitions below, we use the following notation:
+ `σ : Type*` (indexing the variables)
+ `R : Type*` `[CommSemiring R]` (the coefficients)
+ `s : σ →₀ ℕ`, a function from `σ` to `ℕ` which is zero away from a finite set.
This will give rise to a monomial in `MvPolynomial σ R` which mathematicians might call `X^s`
+ `a : R`
+ `i : σ`, with corresponding monomial `X i`, often denoted `X_i` by mathematicians
+ `p : MvPolynomial σ R`
### Definitions
* `MvPolynomial σ R` : the type of polynomials with variables of type `σ` and coefficients
in the commutative semiring `R`
* `monomial s a` : the monomial which mathematically would be denoted `a * X^s`
* `C a` : the constant polynomial with value `a`
* `X i` : the degree one monomial corresponding to i; mathematically this might be denoted `Xᵢ`.
* `coeff s p` : the coefficient of `s` in `p`.
* `eval₂ (f : R → S₁) (g : σ → S₁) p` : given a semiring homomorphism from `R` to another
semiring `S₁`, and a map `σ → S₁`, evaluates `p` at this valuation, returning a term of type `S₁`.
Note that `eval₂` can be made using `eval` and `map` (see below), and it has been suggested
that sticking to `eval` and `map` might make the code less brittle.
* `eval (g : σ → R) p` : given a map `σ → R`, evaluates `p` at this valuation,
returning a term of type `R`
* `map (f : R → S₁) p` : returns the multivariate polynomial obtained from `p` by the change of
coefficient semiring corresponding to `f`
## Implementation notes
Recall that if `Y` has a zero, then `X →₀ Y` is the type of functions from `X` to `Y` with finite
support, i.e. such that only finitely many elements of `X` get sent to non-zero terms in `Y`.
The definition of `MvPolynomial σ R` is `(σ →₀ ℕ) →₀ R`; here `σ →₀ ℕ` denotes the space of all
monomials in the variables, and the function to `R` sends a monomial to its coefficient in
the polynomial being represented.
## Tags
polynomial, multivariate polynomial, multivariable polynomial
-/
noncomputable section
open Set Function Finsupp AddMonoidAlgebra
open scoped Pointwise
universe u v w x
variable {R : Type u} {S₁ : Type v} {S₂ : Type w} {S₃ : Type x}
/-- Multivariate polynomial, where `σ` is the index set of the variables and
`R` is the coefficient ring -/
def MvPolynomial (σ : Type*) (R : Type*) [CommSemiring R] :=
AddMonoidAlgebra R (σ →₀ ℕ)
#align mv_polynomial MvPolynomial
namespace MvPolynomial
-- Porting note: because of `MvPolynomial.C` and `MvPolynomial.X` this linter throws
-- tons of warnings in this file, and it's easier to just disable them globally in the file
set_option linter.uppercaseLean3 false
variable {σ : Type*} {a a' a₁ a₂ : R} {e : ℕ} {n m : σ} {s : σ →₀ ℕ}
section CommSemiring
section Instances
instance decidableEqMvPolynomial [CommSemiring R] [DecidableEq σ] [DecidableEq R] :
DecidableEq (MvPolynomial σ R) :=
Finsupp.instDecidableEq
#align mv_polynomial.decidable_eq_mv_polynomial MvPolynomial.decidableEqMvPolynomial
instance commSemiring [CommSemiring R] : CommSemiring (MvPolynomial σ R) :=
AddMonoidAlgebra.commSemiring
instance inhabited [CommSemiring R] : Inhabited (MvPolynomial σ R) :=
⟨0⟩
instance distribuMulAction [Monoid R] [CommSemiring S₁] [DistribMulAction R S₁] :
DistribMulAction R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.distribMulAction
instance smulZeroClass [CommSemiring S₁] [SMulZeroClass R S₁] :
SMulZeroClass R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.smulZeroClass
instance faithfulSMul [CommSemiring S₁] [SMulZeroClass R S₁] [FaithfulSMul R S₁] :
FaithfulSMul R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.faithfulSMul
instance module [Semiring R] [CommSemiring S₁] [Module R S₁] : Module R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.module
instance isScalarTower [CommSemiring S₂] [SMul R S₁] [SMulZeroClass R S₂] [SMulZeroClass S₁ S₂]
[IsScalarTower R S₁ S₂] : IsScalarTower R S₁ (MvPolynomial σ S₂) :=
AddMonoidAlgebra.isScalarTower
instance smulCommClass [CommSemiring S₂] [SMulZeroClass R S₂] [SMulZeroClass S₁ S₂]
[SMulCommClass R S₁ S₂] : SMulCommClass R S₁ (MvPolynomial σ S₂) :=
AddMonoidAlgebra.smulCommClass
instance isCentralScalar [CommSemiring S₁] [SMulZeroClass R S₁] [SMulZeroClass Rᵐᵒᵖ S₁]
[IsCentralScalar R S₁] : IsCentralScalar R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.isCentralScalar
instance algebra [CommSemiring R] [CommSemiring S₁] [Algebra R S₁] :
Algebra R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.algebra
instance isScalarTower_right [CommSemiring S₁] [DistribSMul R S₁] [IsScalarTower R S₁ S₁] :
IsScalarTower R (MvPolynomial σ S₁) (MvPolynomial σ S₁) :=
AddMonoidAlgebra.isScalarTower_self _
#align mv_polynomial.is_scalar_tower_right MvPolynomial.isScalarTower_right
instance smulCommClass_right [CommSemiring S₁] [DistribSMul R S₁] [SMulCommClass R S₁ S₁] :
SMulCommClass R (MvPolynomial σ S₁) (MvPolynomial σ S₁) :=
AddMonoidAlgebra.smulCommClass_self _
#align mv_polynomial.smul_comm_class_right MvPolynomial.smulCommClass_right
/-- If `R` is a subsingleton, then `MvPolynomial σ R` has a unique element -/
instance unique [CommSemiring R] [Subsingleton R] : Unique (MvPolynomial σ R) :=
AddMonoidAlgebra.unique
#align mv_polynomial.unique MvPolynomial.unique
end Instances
variable [CommSemiring R] [CommSemiring S₁] {p q : MvPolynomial σ R}
/-- `monomial s a` is the monomial with coefficient `a` and exponents given by `s` -/
def monomial (s : σ →₀ ℕ) : R →ₗ[R] MvPolynomial σ R :=
lsingle s
#align mv_polynomial.monomial MvPolynomial.monomial
theorem single_eq_monomial (s : σ →₀ ℕ) (a : R) : Finsupp.single s a = monomial s a :=
rfl
#align mv_polynomial.single_eq_monomial MvPolynomial.single_eq_monomial
theorem mul_def : p * q = p.sum fun m a => q.sum fun n b => monomial (m + n) (a * b) :=
AddMonoidAlgebra.mul_def
#align mv_polynomial.mul_def MvPolynomial.mul_def
/-- `C a` is the constant polynomial with value `a` -/
def C : R →+* MvPolynomial σ R :=
{ singleZeroRingHom with toFun := monomial 0 }
#align mv_polynomial.C MvPolynomial.C
variable (R σ)
@[simp]
theorem algebraMap_eq : algebraMap R (MvPolynomial σ R) = C :=
rfl
#align mv_polynomial.algebra_map_eq MvPolynomial.algebraMap_eq
variable {R σ}
/-- `X n` is the degree `1` monomial $X_n$. -/
def X (n : σ) : MvPolynomial σ R :=
monomial (Finsupp.single n 1) 1
#align mv_polynomial.X MvPolynomial.X
theorem monomial_left_injective {r : R} (hr : r ≠ 0) :
Function.Injective fun s : σ →₀ ℕ => monomial s r :=
Finsupp.single_left_injective hr
#align mv_polynomial.monomial_left_injective MvPolynomial.monomial_left_injective
@[simp]
theorem monomial_left_inj {s t : σ →₀ ℕ} {r : R} (hr : r ≠ 0) :
monomial s r = monomial t r ↔ s = t :=
Finsupp.single_left_inj hr
#align mv_polynomial.monomial_left_inj MvPolynomial.monomial_left_inj
theorem C_apply : (C a : MvPolynomial σ R) = monomial 0 a :=
rfl
#align mv_polynomial.C_apply MvPolynomial.C_apply
-- Porting note (#10618): `simp` can prove this
theorem C_0 : C 0 = (0 : MvPolynomial σ R) := map_zero _
#align mv_polynomial.C_0 MvPolynomial.C_0
-- Porting note (#10618): `simp` can prove this
theorem C_1 : C 1 = (1 : MvPolynomial σ R) :=
rfl
#align mv_polynomial.C_1 MvPolynomial.C_1
theorem C_mul_monomial : C a * monomial s a' = monomial s (a * a') := by
-- Porting note: this `show` feels like defeq abuse, but I can't find the appropriate lemmas
show AddMonoidAlgebra.single _ _ * AddMonoidAlgebra.single _ _ = AddMonoidAlgebra.single _ _
simp [C_apply, single_mul_single]
#align mv_polynomial.C_mul_monomial MvPolynomial.C_mul_monomial
-- Porting note (#10618): `simp` can prove this
theorem C_add : (C (a + a') : MvPolynomial σ R) = C a + C a' :=
Finsupp.single_add _ _ _
#align mv_polynomial.C_add MvPolynomial.C_add
-- Porting note (#10618): `simp` can prove this
theorem C_mul : (C (a * a') : MvPolynomial σ R) = C a * C a' :=
C_mul_monomial.symm
#align mv_polynomial.C_mul MvPolynomial.C_mul
-- Porting note (#10618): `simp` can prove this
theorem C_pow (a : R) (n : ℕ) : (C (a ^ n) : MvPolynomial σ R) = C a ^ n :=
map_pow _ _ _
#align mv_polynomial.C_pow MvPolynomial.C_pow
theorem C_injective (σ : Type*) (R : Type*) [CommSemiring R] :
Function.Injective (C : R → MvPolynomial σ R) :=
Finsupp.single_injective _
#align mv_polynomial.C_injective MvPolynomial.C_injective
theorem C_surjective {R : Type*} [CommSemiring R] (σ : Type*) [IsEmpty σ] :
Function.Surjective (C : R → MvPolynomial σ R) := by
refine fun p => ⟨p.toFun 0, Finsupp.ext fun a => ?_⟩
simp only [C_apply, ← single_eq_monomial, (Finsupp.ext isEmptyElim (α := σ) : a = 0),
single_eq_same]
rfl
#align mv_polynomial.C_surjective MvPolynomial.C_surjective
@[simp]
theorem C_inj {σ : Type*} (R : Type*) [CommSemiring R] (r s : R) :
(C r : MvPolynomial σ R) = C s ↔ r = s :=
(C_injective σ R).eq_iff
#align mv_polynomial.C_inj MvPolynomial.C_inj
instance nontrivial_of_nontrivial (σ : Type*) (R : Type*) [CommSemiring R] [Nontrivial R] :
Nontrivial (MvPolynomial σ R) :=
inferInstanceAs (Nontrivial <| AddMonoidAlgebra R (σ →₀ ℕ))
instance infinite_of_infinite (σ : Type*) (R : Type*) [CommSemiring R] [Infinite R] :
Infinite (MvPolynomial σ R) :=
Infinite.of_injective C (C_injective _ _)
#align mv_polynomial.infinite_of_infinite MvPolynomial.infinite_of_infinite
instance infinite_of_nonempty (σ : Type*) (R : Type*) [Nonempty σ] [CommSemiring R]
[Nontrivial R] : Infinite (MvPolynomial σ R) :=
Infinite.of_injective ((fun s : σ →₀ ℕ => monomial s 1) ∘ Finsupp.single (Classical.arbitrary σ))
<| (monomial_left_injective one_ne_zero).comp (Finsupp.single_injective _)
#align mv_polynomial.infinite_of_nonempty MvPolynomial.infinite_of_nonempty
theorem C_eq_coe_nat (n : ℕ) : (C ↑n : MvPolynomial σ R) = n := by
induction n <;> simp [Nat.succ_eq_add_one, *]
#align mv_polynomial.C_eq_coe_nat MvPolynomial.C_eq_coe_nat
theorem C_mul' : MvPolynomial.C a * p = a • p :=
(Algebra.smul_def a p).symm
#align mv_polynomial.C_mul' MvPolynomial.C_mul'
theorem smul_eq_C_mul (p : MvPolynomial σ R) (a : R) : a • p = C a * p :=
C_mul'.symm
#align mv_polynomial.smul_eq_C_mul MvPolynomial.smul_eq_C_mul
theorem C_eq_smul_one : (C a : MvPolynomial σ R) = a • (1 : MvPolynomial σ R) := by
rw [← C_mul', mul_one]
#align mv_polynomial.C_eq_smul_one MvPolynomial.C_eq_smul_one
theorem smul_monomial {S₁ : Type*} [SMulZeroClass S₁ R] (r : S₁) :
r • monomial s a = monomial s (r • a) :=
Finsupp.smul_single _ _ _
#align mv_polynomial.smul_monomial MvPolynomial.smul_monomial
theorem X_injective [Nontrivial R] : Function.Injective (X : σ → MvPolynomial σ R) :=
(monomial_left_injective one_ne_zero).comp (Finsupp.single_left_injective one_ne_zero)
#align mv_polynomial.X_injective MvPolynomial.X_injective
@[simp]
theorem X_inj [Nontrivial R] (m n : σ) : X m = (X n : MvPolynomial σ R) ↔ m = n :=
X_injective.eq_iff
#align mv_polynomial.X_inj MvPolynomial.X_inj
theorem monomial_pow : monomial s a ^ e = monomial (e • s) (a ^ e) :=
AddMonoidAlgebra.single_pow e
#align mv_polynomial.monomial_pow MvPolynomial.monomial_pow
@[simp]
theorem monomial_mul {s s' : σ →₀ ℕ} {a b : R} :
monomial s a * monomial s' b = monomial (s + s') (a * b) :=
AddMonoidAlgebra.single_mul_single
#align mv_polynomial.monomial_mul MvPolynomial.monomial_mul
variable (σ R)
/-- `fun s ↦ monomial s 1` as a homomorphism. -/
def monomialOneHom : Multiplicative (σ →₀ ℕ) →* MvPolynomial σ R :=
AddMonoidAlgebra.of _ _
#align mv_polynomial.monomial_one_hom MvPolynomial.monomialOneHom
variable {σ R}
@[simp]
theorem monomialOneHom_apply : monomialOneHom R σ s = (monomial s 1 : MvPolynomial σ R) :=
rfl
#align mv_polynomial.monomial_one_hom_apply MvPolynomial.monomialOneHom_apply
theorem X_pow_eq_monomial : X n ^ e = monomial (Finsupp.single n e) (1 : R) := by
simp [X, monomial_pow]
#align mv_polynomial.X_pow_eq_monomial MvPolynomial.X_pow_eq_monomial
theorem monomial_add_single : monomial (s + Finsupp.single n e) a = monomial s a * X n ^ e := by
rw [X_pow_eq_monomial, monomial_mul, mul_one]
#align mv_polynomial.monomial_add_single MvPolynomial.monomial_add_single
theorem monomial_single_add : monomial (Finsupp.single n e + s) a = X n ^ e * monomial s a := by
rw [X_pow_eq_monomial, monomial_mul, one_mul]
#align mv_polynomial.monomial_single_add MvPolynomial.monomial_single_add
theorem C_mul_X_pow_eq_monomial {s : σ} {a : R} {n : ℕ} :
C a * X s ^ n = monomial (Finsupp.single s n) a := by
rw [← zero_add (Finsupp.single s n), monomial_add_single, C_apply]
#align mv_polynomial.C_mul_X_pow_eq_monomial MvPolynomial.C_mul_X_pow_eq_monomial
theorem C_mul_X_eq_monomial {s : σ} {a : R} : C a * X s = monomial (Finsupp.single s 1) a := by
rw [← C_mul_X_pow_eq_monomial, pow_one]
#align mv_polynomial.C_mul_X_eq_monomial MvPolynomial.C_mul_X_eq_monomial
-- Porting note (#10618): `simp` can prove this
theorem monomial_zero {s : σ →₀ ℕ} : monomial s (0 : R) = 0 :=
Finsupp.single_zero _
#align mv_polynomial.monomial_zero MvPolynomial.monomial_zero
@[simp]
theorem monomial_zero' : (monomial (0 : σ →₀ ℕ) : R → MvPolynomial σ R) = C :=
rfl
#align mv_polynomial.monomial_zero' MvPolynomial.monomial_zero'
@[simp]
theorem monomial_eq_zero {s : σ →₀ ℕ} {b : R} : monomial s b = 0 ↔ b = 0 :=
Finsupp.single_eq_zero
#align mv_polynomial.monomial_eq_zero MvPolynomial.monomial_eq_zero
@[simp]
theorem sum_monomial_eq {A : Type*} [AddCommMonoid A] {u : σ →₀ ℕ} {r : R} {b : (σ →₀ ℕ) → R → A}
(w : b u 0 = 0) : sum (monomial u r) b = b u r :=
Finsupp.sum_single_index w
#align mv_polynomial.sum_monomial_eq MvPolynomial.sum_monomial_eq
@[simp]
theorem sum_C {A : Type*} [AddCommMonoid A] {b : (σ →₀ ℕ) → R → A} (w : b 0 0 = 0) :
sum (C a) b = b 0 a :=
sum_monomial_eq w
#align mv_polynomial.sum_C MvPolynomial.sum_C
theorem monomial_sum_one {α : Type*} (s : Finset α) (f : α → σ →₀ ℕ) :
(monomial (∑ i ∈ s, f i) 1 : MvPolynomial σ R) = ∏ i ∈ s, monomial (f i) 1 :=
map_prod (monomialOneHom R σ) (fun i => Multiplicative.ofAdd (f i)) s
#align mv_polynomial.monomial_sum_one MvPolynomial.monomial_sum_one
theorem monomial_sum_index {α : Type*} (s : Finset α) (f : α → σ →₀ ℕ) (a : R) :
monomial (∑ i ∈ s, f i) a = C a * ∏ i ∈ s, monomial (f i) 1 := by
rw [← monomial_sum_one, C_mul', ← (monomial _).map_smul, smul_eq_mul, mul_one]
#align mv_polynomial.monomial_sum_index MvPolynomial.monomial_sum_index
theorem monomial_finsupp_sum_index {α β : Type*} [Zero β] (f : α →₀ β) (g : α → β → σ →₀ ℕ)
(a : R) : monomial (f.sum g) a = C a * f.prod fun a b => monomial (g a b) 1 :=
monomial_sum_index _ _ _
#align mv_polynomial.monomial_finsupp_sum_index MvPolynomial.monomial_finsupp_sum_index
theorem monomial_eq_monomial_iff {α : Type*} (a₁ a₂ : α →₀ ℕ) (b₁ b₂ : R) :
monomial a₁ b₁ = monomial a₂ b₂ ↔ a₁ = a₂ ∧ b₁ = b₂ ∨ b₁ = 0 ∧ b₂ = 0 :=
Finsupp.single_eq_single_iff _ _ _ _
#align mv_polynomial.monomial_eq_monomial_iff MvPolynomial.monomial_eq_monomial_iff
theorem monomial_eq : monomial s a = C a * (s.prod fun n e => X n ^ e : MvPolynomial σ R) := by
simp only [X_pow_eq_monomial, ← monomial_finsupp_sum_index, Finsupp.sum_single]
#align mv_polynomial.monomial_eq MvPolynomial.monomial_eq
@[simp]
lemma prod_X_pow_eq_monomial : ∏ x ∈ s.support, X x ^ s x = monomial s (1 : R) := by
simp only [monomial_eq, map_one, one_mul, Finsupp.prod]
theorem induction_on_monomial {M : MvPolynomial σ R → Prop} (h_C : ∀ a, M (C a))
(h_X : ∀ p n, M p → M (p * X n)) : ∀ s a, M (monomial s a) := by
intro s a
apply @Finsupp.induction σ ℕ _ _ s
· show M (monomial 0 a)
exact h_C a
· intro n e p _hpn _he ih
have : ∀ e : ℕ, M (monomial p a * X n ^ e) := by
intro e
induction e with
| zero => simp [ih]
| succ e e_ih => simp [ih, pow_succ, (mul_assoc _ _ _).symm, h_X, e_ih]
simp [add_comm, monomial_add_single, this]
#align mv_polynomial.induction_on_monomial MvPolynomial.induction_on_monomial
/-- Analog of `Polynomial.induction_on'`.
To prove something about mv_polynomials,
it suffices to show the condition is closed under taking sums,
and it holds for monomials. -/
@[elab_as_elim]
theorem induction_on' {P : MvPolynomial σ R → Prop} (p : MvPolynomial σ R)
(h1 : ∀ (u : σ →₀ ℕ) (a : R), P (monomial u a))
(h2 : ∀ p q : MvPolynomial σ R, P p → P q → P (p + q)) : P p :=
Finsupp.induction p
(suffices P (monomial 0 0) by rwa [monomial_zero] at this
show P (monomial 0 0) from h1 0 0)
fun a b f _ha _hb hPf => h2 _ _ (h1 _ _) hPf
#align mv_polynomial.induction_on' MvPolynomial.induction_on'
/-- Similar to `MvPolynomial.induction_on` but only a weak form of `h_add` is required. -/
theorem induction_on''' {M : MvPolynomial σ R → Prop} (p : MvPolynomial σ R) (h_C : ∀ a, M (C a))
(h_add_weak :
∀ (a : σ →₀ ℕ) (b : R) (f : (σ →₀ ℕ) →₀ R),
a ∉ f.support → b ≠ 0 → M f → M ((show (σ →₀ ℕ) →₀ R from monomial a b) + f)) :
M p :=
-- Porting note: I had to add the `show ... from ...` above, a type ascription was insufficient.
Finsupp.induction p (C_0.rec <| h_C 0) h_add_weak
#align mv_polynomial.induction_on''' MvPolynomial.induction_on'''
/-- Similar to `MvPolynomial.induction_on` but only a yet weaker form of `h_add` is required. -/
theorem induction_on'' {M : MvPolynomial σ R → Prop} (p : MvPolynomial σ R) (h_C : ∀ a, M (C a))
(h_add_weak :
∀ (a : σ →₀ ℕ) (b : R) (f : (σ →₀ ℕ) →₀ R),
a ∉ f.support → b ≠ 0 → M f → M (monomial a b) →
M ((show (σ →₀ ℕ) →₀ R from monomial a b) + f))
(h_X : ∀ (p : MvPolynomial σ R) (n : σ), M p → M (p * MvPolynomial.X n)) : M p :=
-- Porting note: I had to add the `show ... from ...` above, a type ascription was insufficient.
induction_on''' p h_C fun a b f ha hb hf =>
h_add_weak a b f ha hb hf <| induction_on_monomial h_C h_X a b
#align mv_polynomial.induction_on'' MvPolynomial.induction_on''
/-- Analog of `Polynomial.induction_on`. -/
@[recursor 5]
theorem induction_on {M : MvPolynomial σ R → Prop} (p : MvPolynomial σ R) (h_C : ∀ a, M (C a))
(h_add : ∀ p q, M p → M q → M (p + q)) (h_X : ∀ p n, M p → M (p * X n)) : M p :=
induction_on'' p h_C (fun a b f _ha _hb hf hm => h_add (monomial a b) f hm hf) h_X
#align mv_polynomial.induction_on MvPolynomial.induction_on
theorem ringHom_ext {A : Type*} [Semiring A] {f g : MvPolynomial σ R →+* A}
(hC : ∀ r, f (C r) = g (C r)) (hX : ∀ i, f (X i) = g (X i)) : f = g := by
refine AddMonoidAlgebra.ringHom_ext' ?_ ?_
-- Porting note: this has high priority, but Lean still chooses `RingHom.ext`, why?
-- probably because of the type synonym
· ext x
exact hC _
· apply Finsupp.mulHom_ext'; intros x
-- Porting note: `Finsupp.mulHom_ext'` needs to have increased priority
apply MonoidHom.ext_mnat
exact hX _
#align mv_polynomial.ring_hom_ext MvPolynomial.ringHom_ext
/-- See note [partially-applied ext lemmas]. -/
@[ext 1100]
theorem ringHom_ext' {A : Type*} [Semiring A] {f g : MvPolynomial σ R →+* A}
(hC : f.comp C = g.comp C) (hX : ∀ i, f (X i) = g (X i)) : f = g :=
ringHom_ext (RingHom.ext_iff.1 hC) hX
#align mv_polynomial.ring_hom_ext' MvPolynomial.ringHom_ext'
theorem hom_eq_hom [Semiring S₂] (f g : MvPolynomial σ R →+* S₂) (hC : f.comp C = g.comp C)
(hX : ∀ n : σ, f (X n) = g (X n)) (p : MvPolynomial σ R) : f p = g p :=
RingHom.congr_fun (ringHom_ext' hC hX) p
#align mv_polynomial.hom_eq_hom MvPolynomial.hom_eq_hom
theorem is_id (f : MvPolynomial σ R →+* MvPolynomial σ R) (hC : f.comp C = C)
(hX : ∀ n : σ, f (X n) = X n) (p : MvPolynomial σ R) : f p = p :=
hom_eq_hom f (RingHom.id _) hC hX p
#align mv_polynomial.is_id MvPolynomial.is_id
@[ext 1100]
theorem algHom_ext' {A B : Type*} [CommSemiring A] [CommSemiring B] [Algebra R A] [Algebra R B]
{f g : MvPolynomial σ A →ₐ[R] B}
(h₁ :
f.comp (IsScalarTower.toAlgHom R A (MvPolynomial σ A)) =
g.comp (IsScalarTower.toAlgHom R A (MvPolynomial σ A)))
(h₂ : ∀ i, f (X i) = g (X i)) : f = g :=
AlgHom.coe_ringHom_injective (MvPolynomial.ringHom_ext' (congr_arg AlgHom.toRingHom h₁) h₂)
#align mv_polynomial.alg_hom_ext' MvPolynomial.algHom_ext'
@[ext 1200]
theorem algHom_ext {A : Type*} [Semiring A] [Algebra R A] {f g : MvPolynomial σ R →ₐ[R] A}
(hf : ∀ i : σ, f (X i) = g (X i)) : f = g :=
AddMonoidAlgebra.algHom_ext' (mulHom_ext' fun X : σ => MonoidHom.ext_mnat (hf X))
#align mv_polynomial.alg_hom_ext MvPolynomial.algHom_ext
@[simp]
theorem algHom_C {τ : Type*} (f : MvPolynomial σ R →ₐ[R] MvPolynomial τ R) (r : R) :
f (C r) = C r :=
f.commutes r
#align mv_polynomial.alg_hom_C MvPolynomial.algHom_C
@[simp]
theorem adjoin_range_X : Algebra.adjoin R (range (X : σ → MvPolynomial σ R)) = ⊤ := by
set S := Algebra.adjoin R (range (X : σ → MvPolynomial σ R))
refine top_unique fun p hp => ?_; clear hp
induction p using MvPolynomial.induction_on with
| h_C => exact S.algebraMap_mem _
| h_add p q hp hq => exact S.add_mem hp hq
| h_X p i hp => exact S.mul_mem hp (Algebra.subset_adjoin <| mem_range_self _)
#align mv_polynomial.adjoin_range_X MvPolynomial.adjoin_range_X
@[ext]
theorem linearMap_ext {M : Type*} [AddCommMonoid M] [Module R M] {f g : MvPolynomial σ R →ₗ[R] M}
(h : ∀ s, f ∘ₗ monomial s = g ∘ₗ monomial s) : f = g :=
Finsupp.lhom_ext' h
#align mv_polynomial.linear_map_ext MvPolynomial.linearMap_ext
section Support
/-- The finite set of all `m : σ →₀ ℕ` such that `X^m` has a non-zero coefficient. -/
def support (p : MvPolynomial σ R) : Finset (σ →₀ ℕ) :=
Finsupp.support p
#align mv_polynomial.support MvPolynomial.support
theorem finsupp_support_eq_support (p : MvPolynomial σ R) : Finsupp.support p = p.support :=
rfl
#align mv_polynomial.finsupp_support_eq_support MvPolynomial.finsupp_support_eq_support
theorem support_monomial [h : Decidable (a = 0)] :
(monomial s a).support = if a = 0 then ∅ else {s} := by
rw [← Subsingleton.elim (Classical.decEq R a 0) h]
rfl
-- Porting note: the proof in Lean 3 wasn't fundamentally better and needed `by convert rfl`
-- the issue is the different decidability instances in the `ite` expressions
#align mv_polynomial.support_monomial MvPolynomial.support_monomial
theorem support_monomial_subset : (monomial s a).support ⊆ {s} :=
support_single_subset
#align mv_polynomial.support_monomial_subset MvPolynomial.support_monomial_subset
theorem support_add [DecidableEq σ] : (p + q).support ⊆ p.support ∪ q.support :=
Finsupp.support_add
#align mv_polynomial.support_add MvPolynomial.support_add
theorem support_X [Nontrivial R] : (X n : MvPolynomial σ R).support = {Finsupp.single n 1} := by
classical rw [X, support_monomial, if_neg]; exact one_ne_zero
#align mv_polynomial.support_X MvPolynomial.support_X
theorem support_X_pow [Nontrivial R] (s : σ) (n : ℕ) :
(X s ^ n : MvPolynomial σ R).support = {Finsupp.single s n} := by
classical
rw [X_pow_eq_monomial, support_monomial, if_neg (one_ne_zero' R)]
#align mv_polynomial.support_X_pow MvPolynomial.support_X_pow
@[simp]
theorem support_zero : (0 : MvPolynomial σ R).support = ∅ :=
rfl
#align mv_polynomial.support_zero MvPolynomial.support_zero
theorem support_smul {S₁ : Type*} [SMulZeroClass S₁ R] {a : S₁} {f : MvPolynomial σ R} :
(a • f).support ⊆ f.support :=
Finsupp.support_smul
#align mv_polynomial.support_smul MvPolynomial.support_smul
theorem support_sum {α : Type*} [DecidableEq σ] {s : Finset α} {f : α → MvPolynomial σ R} :
(∑ x ∈ s, f x).support ⊆ s.biUnion fun x => (f x).support :=
Finsupp.support_finset_sum
#align mv_polynomial.support_sum MvPolynomial.support_sum
end Support
section Coeff
/-- The coefficient of the monomial `m` in the multi-variable polynomial `p`. -/
def coeff (m : σ →₀ ℕ) (p : MvPolynomial σ R) : R :=
@DFunLike.coe ((σ →₀ ℕ) →₀ R) _ _ _ p m
-- Porting note: I changed this from `@CoeFun.coe _ _ (MonoidAlgebra.coeFun _ _) p m` because
-- I think it should work better syntactically. They are defeq.
#align mv_polynomial.coeff MvPolynomial.coeff
@[simp]
theorem mem_support_iff {p : MvPolynomial σ R} {m : σ →₀ ℕ} : m ∈ p.support ↔ p.coeff m ≠ 0 := by
simp [support, coeff]
#align mv_polynomial.mem_support_iff MvPolynomial.mem_support_iff
theorem not_mem_support_iff {p : MvPolynomial σ R} {m : σ →₀ ℕ} : m ∉ p.support ↔ p.coeff m = 0 :=
by simp
#align mv_polynomial.not_mem_support_iff MvPolynomial.not_mem_support_iff
theorem sum_def {A} [AddCommMonoid A] {p : MvPolynomial σ R} {b : (σ →₀ ℕ) → R → A} :
p.sum b = ∑ m ∈ p.support, b m (p.coeff m) := by simp [support, Finsupp.sum, coeff]
#align mv_polynomial.sum_def MvPolynomial.sum_def
theorem support_mul [DecidableEq σ] (p q : MvPolynomial σ R) :
(p * q).support ⊆ p.support + q.support :=
AddMonoidAlgebra.support_mul p q
#align mv_polynomial.support_mul MvPolynomial.support_mul
@[ext]
theorem ext (p q : MvPolynomial σ R) : (∀ m, coeff m p = coeff m q) → p = q :=
Finsupp.ext
#align mv_polynomial.ext MvPolynomial.ext
theorem ext_iff (p q : MvPolynomial σ R) : p = q ↔ ∀ m, coeff m p = coeff m q :=
⟨fun h m => by rw [h], ext p q⟩
#align mv_polynomial.ext_iff MvPolynomial.ext_iff
@[simp]
theorem coeff_add (m : σ →₀ ℕ) (p q : MvPolynomial σ R) : coeff m (p + q) = coeff m p + coeff m q :=
add_apply p q m
#align mv_polynomial.coeff_add MvPolynomial.coeff_add
@[simp]
theorem coeff_smul {S₁ : Type*} [SMulZeroClass S₁ R] (m : σ →₀ ℕ) (C : S₁) (p : MvPolynomial σ R) :
coeff m (C • p) = C • coeff m p :=
smul_apply C p m
#align mv_polynomial.coeff_smul MvPolynomial.coeff_smul
@[simp]
theorem coeff_zero (m : σ →₀ ℕ) : coeff m (0 : MvPolynomial σ R) = 0 :=
rfl
#align mv_polynomial.coeff_zero MvPolynomial.coeff_zero
@[simp]
theorem coeff_zero_X (i : σ) : coeff 0 (X i : MvPolynomial σ R) = 0 :=
single_eq_of_ne fun h => by cases Finsupp.single_eq_zero.1 h
#align mv_polynomial.coeff_zero_X MvPolynomial.coeff_zero_X
/-- `MvPolynomial.coeff m` but promoted to an `AddMonoidHom`. -/
@[simps]
def coeffAddMonoidHom (m : σ →₀ ℕ) : MvPolynomial σ R →+ R where
toFun := coeff m
map_zero' := coeff_zero m
map_add' := coeff_add m
#align mv_polynomial.coeff_add_monoid_hom MvPolynomial.coeffAddMonoidHom
variable (R) in
/-- `MvPolynomial.coeff m` but promoted to a `LinearMap`. -/
@[simps]
def lcoeff (m : σ →₀ ℕ) : MvPolynomial σ R →ₗ[R] R where
toFun := coeff m
map_add' := coeff_add m
map_smul' := coeff_smul m
theorem coeff_sum {X : Type*} (s : Finset X) (f : X → MvPolynomial σ R) (m : σ →₀ ℕ) :
coeff m (∑ x ∈ s, f x) = ∑ x ∈ s, coeff m (f x) :=
map_sum (@coeffAddMonoidHom R σ _ _) _ s
#align mv_polynomial.coeff_sum MvPolynomial.coeff_sum
theorem monic_monomial_eq (m) :
monomial m (1 : R) = (m.prod fun n e => X n ^ e : MvPolynomial σ R) := by simp [monomial_eq]
#align mv_polynomial.monic_monomial_eq MvPolynomial.monic_monomial_eq
@[simp]
theorem coeff_monomial [DecidableEq σ] (m n) (a) :
coeff m (monomial n a : MvPolynomial σ R) = if n = m then a else 0 :=
Finsupp.single_apply
#align mv_polynomial.coeff_monomial MvPolynomial.coeff_monomial
@[simp]
theorem coeff_C [DecidableEq σ] (m) (a) :
coeff m (C a : MvPolynomial σ R) = if 0 = m then a else 0 :=
Finsupp.single_apply
#align mv_polynomial.coeff_C MvPolynomial.coeff_C
lemma eq_C_of_isEmpty [IsEmpty σ] (p : MvPolynomial σ R) :
p = C (p.coeff 0) := by
obtain ⟨x, rfl⟩ := C_surjective σ p
simp
theorem coeff_one [DecidableEq σ] (m) : coeff m (1 : MvPolynomial σ R) = if 0 = m then 1 else 0 :=
coeff_C m 1
#align mv_polynomial.coeff_one MvPolynomial.coeff_one
@[simp]
theorem coeff_zero_C (a) : coeff 0 (C a : MvPolynomial σ R) = a :=
single_eq_same
#align mv_polynomial.coeff_zero_C MvPolynomial.coeff_zero_C
@[simp]
theorem coeff_zero_one : coeff 0 (1 : MvPolynomial σ R) = 1 :=
coeff_zero_C 1
#align mv_polynomial.coeff_zero_one MvPolynomial.coeff_zero_one
theorem coeff_X_pow [DecidableEq σ] (i : σ) (m) (k : ℕ) :
coeff m (X i ^ k : MvPolynomial σ R) = if Finsupp.single i k = m then 1 else 0 := by
have := coeff_monomial m (Finsupp.single i k) (1 : R)
rwa [@monomial_eq _ _ (1 : R) (Finsupp.single i k) _, C_1, one_mul, Finsupp.prod_single_index]
at this
exact pow_zero _
#align mv_polynomial.coeff_X_pow MvPolynomial.coeff_X_pow
theorem coeff_X' [DecidableEq σ] (i : σ) (m) :
coeff m (X i : MvPolynomial σ R) = if Finsupp.single i 1 = m then 1 else 0 := by
rw [← coeff_X_pow, pow_one]
#align mv_polynomial.coeff_X' MvPolynomial.coeff_X'
@[simp]
theorem coeff_X (i : σ) : coeff (Finsupp.single i 1) (X i : MvPolynomial σ R) = 1 := by
classical rw [coeff_X', if_pos rfl]
#align mv_polynomial.coeff_X MvPolynomial.coeff_X
@[simp]
theorem coeff_C_mul (m) (a : R) (p : MvPolynomial σ R) : coeff m (C a * p) = a * coeff m p := by
classical
rw [mul_def, sum_C]
· simp (config := { contextual := true }) [sum_def, coeff_sum]
simp
#align mv_polynomial.coeff_C_mul MvPolynomial.coeff_C_mul
theorem coeff_mul [DecidableEq σ] (p q : MvPolynomial σ R) (n : σ →₀ ℕ) :
coeff n (p * q) = ∑ x ∈ Finset.antidiagonal n, coeff x.1 p * coeff x.2 q :=
AddMonoidAlgebra.mul_apply_antidiagonal p q _ _ Finset.mem_antidiagonal
#align mv_polynomial.coeff_mul MvPolynomial.coeff_mul
@[simp]
theorem coeff_mul_monomial (m) (s : σ →₀ ℕ) (r : R) (p : MvPolynomial σ R) :
coeff (m + s) (p * monomial s r) = coeff m p * r :=
AddMonoidAlgebra.mul_single_apply_aux p _ _ _ _ fun _a => add_left_inj _
#align mv_polynomial.coeff_mul_monomial MvPolynomial.coeff_mul_monomial
@[simp]
theorem coeff_monomial_mul (m) (s : σ →₀ ℕ) (r : R) (p : MvPolynomial σ R) :
coeff (s + m) (monomial s r * p) = r * coeff m p :=
AddMonoidAlgebra.single_mul_apply_aux p _ _ _ _ fun _a => add_right_inj _
#align mv_polynomial.coeff_monomial_mul MvPolynomial.coeff_monomial_mul
@[simp]
theorem coeff_mul_X (m) (s : σ) (p : MvPolynomial σ R) :
coeff (m + Finsupp.single s 1) (p * X s) = coeff m p :=
(coeff_mul_monomial _ _ _ _).trans (mul_one _)
#align mv_polynomial.coeff_mul_X MvPolynomial.coeff_mul_X
@[simp]
theorem coeff_X_mul (m) (s : σ) (p : MvPolynomial σ R) :
coeff (Finsupp.single s 1 + m) (X s * p) = coeff m p :=
(coeff_monomial_mul _ _ _ _).trans (one_mul _)
#align mv_polynomial.coeff_X_mul MvPolynomial.coeff_X_mul
lemma coeff_single_X_pow [DecidableEq σ] (s s' : σ) (n n' : ℕ) :
(X (R := R) s ^ n).coeff (Finsupp.single s' n')
= if s = s' ∧ n = n' ∨ n = 0 ∧ n' = 0 then 1 else 0 := by
simp only [coeff_X_pow, single_eq_single_iff]
@[simp]
lemma coeff_single_X [DecidableEq σ] (s s' : σ) (n : ℕ) :
(X s).coeff (R := R) (Finsupp.single s' n) = if n = 1 ∧ s = s' then 1 else 0 := by
simpa [eq_comm, and_comm] using coeff_single_X_pow s s' 1 n
@[simp]
theorem support_mul_X (s : σ) (p : MvPolynomial σ R) :
(p * X s).support = p.support.map (addRightEmbedding (Finsupp.single s 1)) :=
AddMonoidAlgebra.support_mul_single p _ (by simp) _
#align mv_polynomial.support_mul_X MvPolynomial.support_mul_X
@[simp]
theorem support_X_mul (s : σ) (p : MvPolynomial σ R) :
(X s * p).support = p.support.map (addLeftEmbedding (Finsupp.single s 1)) :=
AddMonoidAlgebra.support_single_mul p _ (by simp) _
#align mv_polynomial.support_X_mul MvPolynomial.support_X_mul
@[simp]
theorem support_smul_eq {S₁ : Type*} [Semiring S₁] [Module S₁ R] [NoZeroSMulDivisors S₁ R] {a : S₁}
(h : a ≠ 0) (p : MvPolynomial σ R) : (a • p).support = p.support :=
Finsupp.support_smul_eq h
#align mv_polynomial.support_smul_eq MvPolynomial.support_smul_eq
theorem support_sdiff_support_subset_support_add [DecidableEq σ] (p q : MvPolynomial σ R) :
p.support \ q.support ⊆ (p + q).support := by
intro m hm
simp only [Classical.not_not, mem_support_iff, Finset.mem_sdiff, Ne] at hm
simp [hm.2, hm.1]
#align mv_polynomial.support_sdiff_support_subset_support_add MvPolynomial.support_sdiff_support_subset_support_add
open scoped symmDiff in
theorem support_symmDiff_support_subset_support_add [DecidableEq σ] (p q : MvPolynomial σ R) :
p.support ∆ q.support ⊆ (p + q).support := by
rw [symmDiff_def, Finset.sup_eq_union]
apply Finset.union_subset
· exact support_sdiff_support_subset_support_add p q
· rw [add_comm]
exact support_sdiff_support_subset_support_add q p
#align mv_polynomial.support_symm_diff_support_subset_support_add MvPolynomial.support_symmDiff_support_subset_support_add
theorem coeff_mul_monomial' (m) (s : σ →₀ ℕ) (r : R) (p : MvPolynomial σ R) :
coeff m (p * monomial s r) = if s ≤ m then coeff (m - s) p * r else 0 := by
classical
split_ifs with h
· conv_rhs => rw [← coeff_mul_monomial _ s]
congr with t
rw [tsub_add_cancel_of_le h]
· contrapose! h
rw [← mem_support_iff] at h
obtain ⟨j, -, rfl⟩ : ∃ j ∈ support p, j + s = m := by
simpa [Finset.add_singleton]
using Finset.add_subset_add_left support_monomial_subset <| support_mul _ _ h
exact le_add_left le_rfl
#align mv_polynomial.coeff_mul_monomial' MvPolynomial.coeff_mul_monomial'
theorem coeff_monomial_mul' (m) (s : σ →₀ ℕ) (r : R) (p : MvPolynomial σ R) :
coeff m (monomial s r * p) = if s ≤ m then r * coeff (m - s) p else 0 := by
-- note that if we allow `R` to be non-commutative we will have to duplicate the proof above.
rw [mul_comm, mul_comm r]
exact coeff_mul_monomial' _ _ _ _
#align mv_polynomial.coeff_monomial_mul' MvPolynomial.coeff_monomial_mul'
theorem coeff_mul_X' [DecidableEq σ] (m) (s : σ) (p : MvPolynomial σ R) :
coeff m (p * X s) = if s ∈ m.support then coeff (m - Finsupp.single s 1) p else 0 := by
refine (coeff_mul_monomial' _ _ _ _).trans ?_
simp_rw [Finsupp.single_le_iff, Finsupp.mem_support_iff, Nat.succ_le_iff, pos_iff_ne_zero,
mul_one]
#align mv_polynomial.coeff_mul_X' MvPolynomial.coeff_mul_X'
theorem coeff_X_mul' [DecidableEq σ] (m) (s : σ) (p : MvPolynomial σ R) :
coeff m (X s * p) = if s ∈ m.support then coeff (m - Finsupp.single s 1) p else 0 := by
refine (coeff_monomial_mul' _ _ _ _).trans ?_
simp_rw [Finsupp.single_le_iff, Finsupp.mem_support_iff, Nat.succ_le_iff, pos_iff_ne_zero,
one_mul]
#align mv_polynomial.coeff_X_mul' MvPolynomial.coeff_X_mul'
theorem eq_zero_iff {p : MvPolynomial σ R} : p = 0 ↔ ∀ d, coeff d p = 0 := by
rw [ext_iff]
simp only [coeff_zero]
#align mv_polynomial.eq_zero_iff MvPolynomial.eq_zero_iff
theorem ne_zero_iff {p : MvPolynomial σ R} : p ≠ 0 ↔ ∃ d, coeff d p ≠ 0 := by
rw [Ne, eq_zero_iff]
push_neg
rfl
#align mv_polynomial.ne_zero_iff MvPolynomial.ne_zero_iff
@[simp]
theorem X_ne_zero [Nontrivial R] (s : σ) :
X (R := R) s ≠ 0 := by
rw [ne_zero_iff]
use Finsupp.single s 1
simp only [coeff_X, ne_eq, one_ne_zero, not_false_eq_true]
@[simp]
theorem support_eq_empty {p : MvPolynomial σ R} : p.support = ∅ ↔ p = 0 :=
Finsupp.support_eq_empty
#align mv_polynomial.support_eq_empty MvPolynomial.support_eq_empty
@[simp]
lemma support_nonempty {p : MvPolynomial σ R} : p.support.Nonempty ↔ p ≠ 0 := by
rw [Finset.nonempty_iff_ne_empty, ne_eq, support_eq_empty]
theorem exists_coeff_ne_zero {p : MvPolynomial σ R} (h : p ≠ 0) : ∃ d, coeff d p ≠ 0 :=
ne_zero_iff.mp h
#align mv_polynomial.exists_coeff_ne_zero MvPolynomial.exists_coeff_ne_zero
theorem C_dvd_iff_dvd_coeff (r : R) (φ : MvPolynomial σ R) : C r ∣ φ ↔ ∀ i, r ∣ φ.coeff i := by
constructor
· rintro ⟨φ, rfl⟩ c
rw [coeff_C_mul]
apply dvd_mul_right
· intro h
choose C hc using h
classical
let c' : (σ →₀ ℕ) → R := fun i => if i ∈ φ.support then C i else 0
let ψ : MvPolynomial σ R := ∑ i ∈ φ.support, monomial i (c' i)
use ψ
apply MvPolynomial.ext
intro i
simp only [ψ, c', coeff_C_mul, coeff_sum, coeff_monomial, Finset.sum_ite_eq']
split_ifs with hi
· rw [hc]
· rw [not_mem_support_iff] at hi
rwa [mul_zero]
#align mv_polynomial.C_dvd_iff_dvd_coeff MvPolynomial.C_dvd_iff_dvd_coeff
@[simp] lemma isRegular_X : IsRegular (X n : MvPolynomial σ R) := by
suffices IsLeftRegular (X n : MvPolynomial σ R) from
⟨this, this.right_of_commute <| Commute.all _⟩
intro P Q (hPQ : (X n) * P = (X n) * Q)
ext i
rw [← coeff_X_mul i n P, hPQ, coeff_X_mul i n Q]
@[simp] lemma isRegular_X_pow (k : ℕ) : IsRegular (X n ^ k : MvPolynomial σ R) := isRegular_X.pow k
@[simp] lemma isRegular_prod_X (s : Finset σ) :
IsRegular (∏ n ∈ s, X n : MvPolynomial σ R) :=
IsRegular.prod fun _ _ ↦ isRegular_X
/-- The finset of nonzero coefficients of a multivariate polynomial. -/
def coeffs (p : MvPolynomial σ R) : Finset R :=
letI := Classical.decEq R
Finset.image p.coeff p.support
@[simp]
lemma coeffs_zero : coeffs (0 : MvPolynomial σ R) = ∅ :=
rfl
lemma coeffs_one : coeffs (1 : MvPolynomial σ R) ⊆ {1} := by
classical
rw [coeffs, Finset.image_subset_iff]
simp_all [coeff_one]
@[nontriviality]
lemma coeffs_eq_empty_of_subsingleton [Subsingleton R] (p : MvPolynomial σ R) : p.coeffs = ∅ := by
simpa [coeffs] using Subsingleton.eq_zero p
@[simp]
lemma coeffs_one_of_nontrivial [Nontrivial R] : coeffs (1 : MvPolynomial σ R) = {1} := by
apply Finset.Subset.antisymm coeffs_one
simp only [coeffs, Finset.singleton_subset_iff, Finset.mem_image]
exact ⟨0, by simp⟩
lemma mem_coeffs_iff {p : MvPolynomial σ R} {c : R} :
c ∈ p.coeffs ↔ ∃ n ∈ p.support, c = p.coeff n := by
simp [coeffs, eq_comm, (Finset.mem_image)]
lemma coeff_mem_coeffs {p : MvPolynomial σ R} (m : σ →₀ ℕ)
(h : p.coeff m ≠ 0) : p.coeff m ∈ p.coeffs :=
letI := Classical.decEq R
Finset.mem_image_of_mem p.coeff (mem_support_iff.mpr h)
lemma zero_not_mem_coeffs (p : MvPolynomial σ R) : 0 ∉ p.coeffs := by
intro hz
obtain ⟨n, hnsupp, hn⟩ := mem_coeffs_iff.mp hz
exact (mem_support_iff.mp hnsupp) hn.symm
end Coeff
section ConstantCoeff
/-- `constantCoeff p` returns the constant term of the polynomial `p`, defined as `coeff 0 p`.
This is a ring homomorphism.
-/
def constantCoeff : MvPolynomial σ R →+* R where
toFun := coeff 0
map_one' := by simp [AddMonoidAlgebra.one_def]
map_mul' := by classical simp [coeff_mul, Finsupp.support_single_ne_zero]
map_zero' := coeff_zero _
map_add' := coeff_add _
#align mv_polynomial.constant_coeff MvPolynomial.constantCoeff
theorem constantCoeff_eq : (constantCoeff : MvPolynomial σ R → R) = coeff 0 :=
rfl
#align mv_polynomial.constant_coeff_eq MvPolynomial.constantCoeff_eq
variable (σ)
@[simp]
theorem constantCoeff_C (r : R) : constantCoeff (C r : MvPolynomial σ R) = r := by
classical simp [constantCoeff_eq]
#align mv_polynomial.constant_coeff_C MvPolynomial.constantCoeff_C
variable {σ}
variable (R)
@[simp]
theorem constantCoeff_X (i : σ) : constantCoeff (X i : MvPolynomial σ R) = 0 := by
simp [constantCoeff_eq]
#align mv_polynomial.constant_coeff_X MvPolynomial.constantCoeff_X
variable {R}
/- porting note: increased priority because otherwise `simp` time outs when trying to simplify
the left-hand side. `simpNF` linter indicated this and it was verified. -/
@[simp 1001]
theorem constantCoeff_smul {R : Type*} [SMulZeroClass R S₁] (a : R) (f : MvPolynomial σ S₁) :
constantCoeff (a • f) = a • constantCoeff f :=
rfl
#align mv_polynomial.constant_coeff_smul MvPolynomial.constantCoeff_smul
theorem constantCoeff_monomial [DecidableEq σ] (d : σ →₀ ℕ) (r : R) :
constantCoeff (monomial d r) = if d = 0 then r else 0 := by
rw [constantCoeff_eq, coeff_monomial]
#align mv_polynomial.constant_coeff_monomial MvPolynomial.constantCoeff_monomial
variable (σ R)
@[simp]
theorem constantCoeff_comp_C : constantCoeff.comp (C : R →+* MvPolynomial σ R) = RingHom.id R := by
ext x
exact constantCoeff_C σ x
#align mv_polynomial.constant_coeff_comp_C MvPolynomial.constantCoeff_comp_C
theorem constantCoeff_comp_algebraMap :
constantCoeff.comp (algebraMap R (MvPolynomial σ R)) = RingHom.id R :=
constantCoeff_comp_C _ _
#align mv_polynomial.constant_coeff_comp_algebra_map MvPolynomial.constantCoeff_comp_algebraMap
end ConstantCoeff
section AsSum
@[simp]
theorem support_sum_monomial_coeff (p : MvPolynomial σ R) :
(∑ v ∈ p.support, monomial v (coeff v p)) = p :=
Finsupp.sum_single p
#align mv_polynomial.support_sum_monomial_coeff MvPolynomial.support_sum_monomial_coeff
theorem as_sum (p : MvPolynomial σ R) : p = ∑ v ∈ p.support, monomial v (coeff v p) :=
(support_sum_monomial_coeff p).symm
#align mv_polynomial.as_sum MvPolynomial.as_sum
end AsSum
section Eval₂
variable (f : R →+* S₁) (g : σ → S₁)
/-- Evaluate a polynomial `p` given a valuation `g` of all the variables
and a ring hom `f` from the scalar ring to the target -/
def eval₂ (p : MvPolynomial σ R) : S₁ :=
p.sum fun s a => f a * s.prod fun n e => g n ^ e
#align mv_polynomial.eval₂ MvPolynomial.eval₂
theorem eval₂_eq (g : R →+* S₁) (X : σ → S₁) (f : MvPolynomial σ R) :
f.eval₂ g X = ∑ d ∈ f.support, g (f.coeff d) * ∏ i ∈ d.support, X i ^ d i :=
rfl
#align mv_polynomial.eval₂_eq MvPolynomial.eval₂_eq
theorem eval₂_eq' [Fintype σ] (g : R →+* S₁) (X : σ → S₁) (f : MvPolynomial σ R) :
f.eval₂ g X = ∑ d ∈ f.support, g (f.coeff d) * ∏ i, X i ^ d i := by
simp only [eval₂_eq, ← Finsupp.prod_pow]
rfl
#align mv_polynomial.eval₂_eq' MvPolynomial.eval₂_eq'
@[simp]
theorem eval₂_zero : (0 : MvPolynomial σ R).eval₂ f g = 0 :=
Finsupp.sum_zero_index
#align mv_polynomial.eval₂_zero MvPolynomial.eval₂_zero
section
@[simp]
theorem eval₂_add : (p + q).eval₂ f g = p.eval₂ f g + q.eval₂ f g := by
classical exact Finsupp.sum_add_index (by simp [f.map_zero]) (by simp [add_mul, f.map_add])
#align mv_polynomial.eval₂_add MvPolynomial.eval₂_add
@[simp]
theorem eval₂_monomial : (monomial s a).eval₂ f g = f a * s.prod fun n e => g n ^ e :=
Finsupp.sum_single_index (by simp [f.map_zero])
#align mv_polynomial.eval₂_monomial MvPolynomial.eval₂_monomial
@[simp]
theorem eval₂_C (a) : (C a).eval₂ f g = f a := by
rw [C_apply, eval₂_monomial, prod_zero_index, mul_one]
#align mv_polynomial.eval₂_C MvPolynomial.eval₂_C
@[simp]
theorem eval₂_one : (1 : MvPolynomial σ R).eval₂ f g = 1 :=
(eval₂_C _ _ _).trans f.map_one
#align mv_polynomial.eval₂_one MvPolynomial.eval₂_one
@[simp]
theorem eval₂_X (n) : (X n).eval₂ f g = g n := by
simp [eval₂_monomial, f.map_one, X, prod_single_index, pow_one]
#align mv_polynomial.eval₂_X MvPolynomial.eval₂_X
theorem eval₂_mul_monomial :
∀ {s a}, (p * monomial s a).eval₂ f g = p.eval₂ f g * f a * s.prod fun n e => g n ^ e := by
classical
apply MvPolynomial.induction_on p
· intro a' s a
simp [C_mul_monomial, eval₂_monomial, f.map_mul]
· intro p q ih_p ih_q
simp [add_mul, eval₂_add, ih_p, ih_q]
· intro p n ih s a
exact
calc (p * X n * monomial s a).eval₂ f g
_ = (p * monomial (Finsupp.single n 1 + s) a).eval₂ f g := by
rw [monomial_single_add, pow_one, mul_assoc]
_ = (p * monomial (Finsupp.single n 1) 1).eval₂ f g * f a * s.prod fun n e => g n ^ e := by
simp [ih, prod_single_index, prod_add_index, pow_one, pow_add, mul_assoc, mul_left_comm,
f.map_one]
#align mv_polynomial.eval₂_mul_monomial MvPolynomial.eval₂_mul_monomial
theorem eval₂_mul_C : (p * C a).eval₂ f g = p.eval₂ f g * f a :=
(eval₂_mul_monomial _ _).trans <| by simp
#align mv_polynomial.eval₂_mul_C MvPolynomial.eval₂_mul_C
@[simp]
theorem eval₂_mul : ∀ {p}, (p * q).eval₂ f g = p.eval₂ f g * q.eval₂ f g := by
apply MvPolynomial.induction_on q
· simp [eval₂_C, eval₂_mul_C]
· simp (config := { contextual := true }) [mul_add, eval₂_add]
· simp (config := { contextual := true }) [X, eval₂_monomial, eval₂_mul_monomial, ← mul_assoc]
#align mv_polynomial.eval₂_mul MvPolynomial.eval₂_mul
@[simp]
theorem eval₂_pow {p : MvPolynomial σ R} : ∀ {n : ℕ}, (p ^ n).eval₂ f g = p.eval₂ f g ^ n
| 0 => by
rw [pow_zero, pow_zero]
exact eval₂_one _ _
| n + 1 => by rw [pow_add, pow_one, pow_add, pow_one, eval₂_mul, eval₂_pow]
#align mv_polynomial.eval₂_pow MvPolynomial.eval₂_pow
/-- `MvPolynomial.eval₂` as a `RingHom`. -/
def eval₂Hom (f : R →+* S₁) (g : σ → S₁) : MvPolynomial σ R →+* S₁ where
toFun := eval₂ f g
map_one' := eval₂_one _ _
map_mul' _ _ := eval₂_mul _ _
map_zero' := eval₂_zero f g
map_add' _ _ := eval₂_add _ _
#align mv_polynomial.eval₂_hom MvPolynomial.eval₂Hom
@[simp]
theorem coe_eval₂Hom (f : R →+* S₁) (g : σ → S₁) : ⇑(eval₂Hom f g) = eval₂ f g :=
rfl
#align mv_polynomial.coe_eval₂_hom MvPolynomial.coe_eval₂Hom
theorem eval₂Hom_congr {f₁ f₂ : R →+* S₁} {g₁ g₂ : σ → S₁} {p₁ p₂ : MvPolynomial σ R} :
f₁ = f₂ → g₁ = g₂ → p₁ = p₂ → eval₂Hom f₁ g₁ p₁ = eval₂Hom f₂ g₂ p₂ := by
rintro rfl rfl rfl; rfl
#align mv_polynomial.eval₂_hom_congr MvPolynomial.eval₂Hom_congr
end
@[simp]
theorem eval₂Hom_C (f : R →+* S₁) (g : σ → S₁) (r : R) : eval₂Hom f g (C r) = f r :=
eval₂_C f g r
#align mv_polynomial.eval₂_hom_C MvPolynomial.eval₂Hom_C
@[simp]
theorem eval₂Hom_X' (f : R →+* S₁) (g : σ → S₁) (i : σ) : eval₂Hom f g (X i) = g i :=
eval₂_X f g i
#align mv_polynomial.eval₂_hom_X' MvPolynomial.eval₂Hom_X'
@[simp]
theorem comp_eval₂Hom [CommSemiring S₂] (f : R →+* S₁) (g : σ → S₁) (φ : S₁ →+* S₂) :
φ.comp (eval₂Hom f g) = eval₂Hom (φ.comp f) fun i => φ (g i) := by
apply MvPolynomial.ringHom_ext
· intro r
rw [RingHom.comp_apply, eval₂Hom_C, eval₂Hom_C, RingHom.comp_apply]
· intro i
rw [RingHom.comp_apply, eval₂Hom_X', eval₂Hom_X']
#align mv_polynomial.comp_eval₂_hom MvPolynomial.comp_eval₂Hom
theorem map_eval₂Hom [CommSemiring S₂] (f : R →+* S₁) (g : σ → S₁) (φ : S₁ →+* S₂)
(p : MvPolynomial σ R) : φ (eval₂Hom f g p) = eval₂Hom (φ.comp f) (fun i => φ (g i)) p := by
rw [← comp_eval₂Hom]
rfl
#align mv_polynomial.map_eval₂_hom MvPolynomial.map_eval₂Hom
theorem eval₂Hom_monomial (f : R →+* S₁) (g : σ → S₁) (d : σ →₀ ℕ) (r : R) :
eval₂Hom f g (monomial d r) = f r * d.prod fun i k => g i ^ k := by
simp only [monomial_eq, RingHom.map_mul, eval₂Hom_C, Finsupp.prod, map_prod,
RingHom.map_pow, eval₂Hom_X']
#align mv_polynomial.eval₂_hom_monomial MvPolynomial.eval₂Hom_monomial
section
theorem eval₂_comp_left {S₂} [CommSemiring S₂] (k : S₁ →+* S₂) (f : R →+* S₁) (g : σ → S₁) (p) :
k (eval₂ f g p) = eval₂ (k.comp f) (k ∘ g) p := by
apply MvPolynomial.induction_on p <;>
simp (config := { contextual := true }) [eval₂_add, k.map_add, eval₂_mul, k.map_mul]
#align mv_polynomial.eval₂_comp_left MvPolynomial.eval₂_comp_left
end
@[simp]
theorem eval₂_eta (p : MvPolynomial σ R) : eval₂ C X p = p := by
apply MvPolynomial.induction_on p <;>
simp (config := { contextual := true }) [eval₂_add, eval₂_mul]
#align mv_polynomial.eval₂_eta MvPolynomial.eval₂_eta
theorem eval₂_congr (g₁ g₂ : σ → S₁)
(h : ∀ {i : σ} {c : σ →₀ ℕ}, i ∈ c.support → coeff c p ≠ 0 → g₁ i = g₂ i) :
p.eval₂ f g₁ = p.eval₂ f g₂ := by
apply Finset.sum_congr rfl
intro C hc; dsimp; congr 1
apply Finset.prod_congr rfl
intro i hi; dsimp; congr 1
apply h hi
rwa [Finsupp.mem_support_iff] at hc
#align mv_polynomial.eval₂_congr MvPolynomial.eval₂_congr
theorem eval₂_sum (s : Finset S₂) (p : S₂ → MvPolynomial σ R) :
eval₂ f g (∑ x ∈ s, p x) = ∑ x ∈ s, eval₂ f g (p x) :=
map_sum (eval₂Hom f g) _ s
#align mv_polynomial.eval₂_sum MvPolynomial.eval₂_sum
@[to_additive existing (attr := simp)]
theorem eval₂_prod (s : Finset S₂) (p : S₂ → MvPolynomial σ R) :
eval₂ f g (∏ x ∈ s, p x) = ∏ x ∈ s, eval₂ f g (p x) :=
map_prod (eval₂Hom f g) _ s
#align mv_polynomial.eval₂_prod MvPolynomial.eval₂_prod
theorem eval₂_assoc (q : S₂ → MvPolynomial σ R) (p : MvPolynomial S₂ R) :
eval₂ f (fun t => eval₂ f g (q t)) p = eval₂ f g (eval₂ C q p) := by
show _ = eval₂Hom f g (eval₂ C q p)
rw [eval₂_comp_left (eval₂Hom f g)]; congr with a; simp
#align mv_polynomial.eval₂_assoc MvPolynomial.eval₂_assoc
end Eval₂
section Eval
variable {f : σ → R}
/-- Evaluate a polynomial `p` given a valuation `f` of all the variables -/
def eval (f : σ → R) : MvPolynomial σ R →+* R :=
eval₂Hom (RingHom.id _) f
#align mv_polynomial.eval MvPolynomial.eval
theorem eval_eq (X : σ → R) (f : MvPolynomial σ R) :
eval X f = ∑ d ∈ f.support, f.coeff d * ∏ i ∈ d.support, X i ^ d i :=
rfl
#align mv_polynomial.eval_eq MvPolynomial.eval_eq
theorem eval_eq' [Fintype σ] (X : σ → R) (f : MvPolynomial σ R) :
eval X f = ∑ d ∈ f.support, f.coeff d * ∏ i, X i ^ d i :=
eval₂_eq' (RingHom.id R) X f
#align mv_polynomial.eval_eq' MvPolynomial.eval_eq'
theorem eval_monomial : eval f (monomial s a) = a * s.prod fun n e => f n ^ e :=
eval₂_monomial _ _
#align mv_polynomial.eval_monomial MvPolynomial.eval_monomial
@[simp]
theorem eval_C : ∀ a, eval f (C a) = a :=
eval₂_C _ _
#align mv_polynomial.eval_C MvPolynomial.eval_C
@[simp]
theorem eval_X : ∀ n, eval f (X n) = f n :=
eval₂_X _ _
#align mv_polynomial.eval_X MvPolynomial.eval_X
@[simp]
theorem smul_eval (x) (p : MvPolynomial σ R) (s) : eval x (s • p) = s * eval x p := by
rw [smul_eq_C_mul, (eval x).map_mul, eval_C]
#align mv_polynomial.smul_eval MvPolynomial.smul_eval
theorem eval_add : eval f (p + q) = eval f p + eval f q :=
eval₂_add _ _
theorem eval_mul : eval f (p * q) = eval f p * eval f q :=
eval₂_mul _ _
theorem eval_pow : ∀ n, eval f (p ^ n) = eval f p ^ n :=
fun _ => eval₂_pow _ _
theorem eval_sum {ι : Type*} (s : Finset ι) (f : ι → MvPolynomial σ R) (g : σ → R) :
eval g (∑ i ∈ s, f i) = ∑ i ∈ s, eval g (f i) :=
map_sum (eval g) _ _
#align mv_polynomial.eval_sum MvPolynomial.eval_sum
@[to_additive existing]
theorem eval_prod {ι : Type*} (s : Finset ι) (f : ι → MvPolynomial σ R) (g : σ → R) :
eval g (∏ i ∈ s, f i) = ∏ i ∈ s, eval g (f i) :=
map_prod (eval g) _ _
#align mv_polynomial.eval_prod MvPolynomial.eval_prod
theorem eval_assoc {τ} (f : σ → MvPolynomial τ R) (g : τ → R) (p : MvPolynomial σ R) :
eval (eval g ∘ f) p = eval g (eval₂ C f p) := by
rw [eval₂_comp_left (eval g)]
unfold eval; simp only [coe_eval₂Hom]
congr with a; simp
#align mv_polynomial.eval_assoc MvPolynomial.eval_assoc
@[simp]
theorem eval₂_id {g : σ → R} (p : MvPolynomial σ R) : eval₂ (RingHom.id _) g p = eval g p :=
rfl
#align mv_polynomial.eval₂_id MvPolynomial.eval₂_id
| Mathlib/Algebra/MvPolynomial/Basic.lean | 1,270 | 1,278 | theorem eval_eval₂ {S τ : Type*} {x : τ → S} [CommSemiring R] [CommSemiring S]
(f : R →+* MvPolynomial τ S) (g : σ → MvPolynomial τ S) (p : MvPolynomial σ R) :
eval x (eval₂ f g p) = eval₂ ((eval x).comp f) (fun s => eval x (g s)) p := by |
apply induction_on p
· simp
· intro p q hp hq
simp [hp, hq]
· intro p n hp
simp [hp]
|
/-
Copyright (c) 2019 Kenny Lau. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kenny Lau
-/
import Mathlib.Algebra.Polynomial.Expand
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Matrix.Charpoly.LinearMap
import Mathlib.RingTheory.Adjoin.FG
import Mathlib.RingTheory.FiniteType
import Mathlib.RingTheory.Polynomial.ScaleRoots
import Mathlib.RingTheory.Polynomial.Tower
import Mathlib.RingTheory.TensorProduct.Basic
#align_import ring_theory.integral_closure from "leanprover-community/mathlib"@"641b6a82006416ec431b2987b354af9311fed4f2"
/-!
# Integral closure of a subring.
If A is an R-algebra then `a : A` is integral over R if it is a root of a monic polynomial
with coefficients in R. Enough theory is developed to prove that integral elements
form a sub-R-algebra of A.
## Main definitions
Let `R` be a `CommRing` and let `A` be an R-algebra.
* `RingHom.IsIntegralElem (f : R →+* A) (x : A)` : `x` is integral with respect to the map `f`,
* `IsIntegral (x : A)` : `x` is integral over `R`, i.e., is a root of a monic polynomial with
coefficients in `R`.
* `integralClosure R A` : the integral closure of `R` in `A`, regarded as a sub-`R`-algebra of `A`.
-/
open scoped Classical
open Polynomial Submodule
section Ring
variable {R S A : Type*}
variable [CommRing R] [Ring A] [Ring S] (f : R →+* S)
/-- An element `x` of `A` is said to be integral over `R` with respect to `f`
if it is a root of a monic polynomial `p : R[X]` evaluated under `f` -/
def RingHom.IsIntegralElem (f : R →+* A) (x : A) :=
∃ p : R[X], Monic p ∧ eval₂ f x p = 0
#align ring_hom.is_integral_elem RingHom.IsIntegralElem
/-- A ring homomorphism `f : R →+* A` is said to be integral
if every element `A` is integral with respect to the map `f` -/
def RingHom.IsIntegral (f : R →+* A) :=
∀ x : A, f.IsIntegralElem x
#align ring_hom.is_integral RingHom.IsIntegral
variable [Algebra R A] (R)
/-- An element `x` of an algebra `A` over a commutative ring `R` is said to be *integral*,
if it is a root of some monic polynomial `p : R[X]`.
Equivalently, the element is integral over `R` with respect to the induced `algebraMap` -/
def IsIntegral (x : A) : Prop :=
(algebraMap R A).IsIntegralElem x
#align is_integral IsIntegral
variable (A)
/-- An algebra is integral if every element of the extension is integral over the base ring -/
protected class Algebra.IsIntegral : Prop :=
isIntegral : ∀ x : A, IsIntegral R x
#align algebra.is_integral Algebra.IsIntegral
variable {R A}
lemma Algebra.isIntegral_def : Algebra.IsIntegral R A ↔ ∀ x : A, IsIntegral R x :=
⟨fun ⟨h⟩ ↦ h, fun h ↦ ⟨h⟩⟩
theorem RingHom.isIntegralElem_map {x : R} : f.IsIntegralElem (f x) :=
⟨X - C x, monic_X_sub_C _, by simp⟩
#align ring_hom.is_integral_map RingHom.isIntegralElem_map
theorem isIntegral_algebraMap {x : R} : IsIntegral R (algebraMap R A x) :=
(algebraMap R A).isIntegralElem_map
#align is_integral_algebra_map isIntegral_algebraMap
end Ring
section
variable {R A B S : Type*}
variable [CommRing R] [CommRing A] [Ring B] [CommRing S]
variable [Algebra R A] [Algebra R B] (f : R →+* S)
theorem IsIntegral.map {B C F : Type*} [Ring B] [Ring C] [Algebra R B] [Algebra A B] [Algebra R C]
[IsScalarTower R A B] [Algebra A C] [IsScalarTower R A C] {b : B}
[FunLike F B C] [AlgHomClass F A B C] (f : F)
(hb : IsIntegral R b) : IsIntegral R (f b) := by
obtain ⟨P, hP⟩ := hb
refine ⟨P, hP.1, ?_⟩
rw [← aeval_def, ← aeval_map_algebraMap A,
aeval_algHom_apply, aeval_map_algebraMap, aeval_def, hP.2, _root_.map_zero]
#align map_is_integral IsIntegral.map
theorem IsIntegral.map_of_comp_eq {R S T U : Type*} [CommRing R] [Ring S]
[CommRing T] [Ring U] [Algebra R S] [Algebra T U] (φ : R →+* T) (ψ : S →+* U)
(h : (algebraMap T U).comp φ = ψ.comp (algebraMap R S)) {a : S} (ha : IsIntegral R a) :
IsIntegral T (ψ a) :=
let ⟨p, hp⟩ := ha
⟨p.map φ, hp.1.map _, by
rw [← eval_map, map_map, h, ← map_map, eval_map, eval₂_at_apply, eval_map, hp.2, ψ.map_zero]⟩
#align is_integral_map_of_comp_eq_of_is_integral IsIntegral.map_of_comp_eq
section
variable {A B : Type*} [Ring A] [Ring B] [Algebra R A] [Algebra R B]
variable (f : A →ₐ[R] B) (hf : Function.Injective f)
theorem isIntegral_algHom_iff {x : A} : IsIntegral R (f x) ↔ IsIntegral R x := by
refine ⟨fun ⟨p, hp, hx⟩ ↦ ⟨p, hp, ?_⟩, IsIntegral.map f⟩
rwa [← f.comp_algebraMap, ← AlgHom.coe_toRingHom, ← hom_eval₂, AlgHom.coe_toRingHom,
map_eq_zero_iff f hf] at hx
#align is_integral_alg_hom_iff isIntegral_algHom_iff
theorem Algebra.IsIntegral.of_injective [Algebra.IsIntegral R B] : Algebra.IsIntegral R A :=
⟨fun _ ↦ (isIntegral_algHom_iff f hf).mp (isIntegral _)⟩
end
@[simp]
theorem isIntegral_algEquiv {A B : Type*} [Ring A] [Ring B] [Algebra R A] [Algebra R B]
(f : A ≃ₐ[R] B) {x : A} : IsIntegral R (f x) ↔ IsIntegral R x :=
⟨fun h ↦ by simpa using h.map f.symm, IsIntegral.map f⟩
#align is_integral_alg_equiv isIntegral_algEquiv
/-- If `R → A → B` is an algebra tower,
then if the entire tower is an integral extension so is `A → B`. -/
theorem IsIntegral.tower_top [Algebra A B] [IsScalarTower R A B] {x : B}
(hx : IsIntegral R x) : IsIntegral A x :=
let ⟨p, hp, hpx⟩ := hx
⟨p.map <| algebraMap R A, hp.map _, by rw [← aeval_def, aeval_map_algebraMap, aeval_def, hpx]⟩
#align is_integral_of_is_scalar_tower IsIntegral.tower_top
#align is_integral_tower_top_of_is_integral IsIntegral.tower_top
theorem map_isIntegral_int {B C F : Type*} [Ring B] [Ring C] {b : B}
[FunLike F B C] [RingHomClass F B C] (f : F)
(hb : IsIntegral ℤ b) : IsIntegral ℤ (f b) :=
hb.map (f : B →+* C).toIntAlgHom
#align map_is_integral_int map_isIntegral_int
theorem IsIntegral.of_subring {x : B} (T : Subring R) (hx : IsIntegral T x) : IsIntegral R x :=
hx.tower_top
#align is_integral_of_subring IsIntegral.of_subring
protected theorem IsIntegral.algebraMap [Algebra A B] [IsScalarTower R A B] {x : A}
(h : IsIntegral R x) : IsIntegral R (algebraMap A B x) := by
rcases h with ⟨f, hf, hx⟩
use f, hf
rw [IsScalarTower.algebraMap_eq R A B, ← hom_eval₂, hx, RingHom.map_zero]
#align is_integral.algebra_map IsIntegral.algebraMap
theorem isIntegral_algebraMap_iff [Algebra A B] [IsScalarTower R A B] {x : A}
(hAB : Function.Injective (algebraMap A B)) :
IsIntegral R (algebraMap A B x) ↔ IsIntegral R x :=
isIntegral_algHom_iff (IsScalarTower.toAlgHom R A B) hAB
#align is_integral_algebra_map_iff isIntegral_algebraMap_iff
theorem isIntegral_iff_isIntegral_closure_finite {r : B} :
IsIntegral R r ↔ ∃ s : Set R, s.Finite ∧ IsIntegral (Subring.closure s) r := by
constructor <;> intro hr
· rcases hr with ⟨p, hmp, hpr⟩
refine ⟨_, Finset.finite_toSet _, p.restriction, monic_restriction.2 hmp, ?_⟩
rw [← aeval_def, ← aeval_map_algebraMap R r p.restriction, map_restriction, aeval_def, hpr]
rcases hr with ⟨s, _, hsr⟩
exact hsr.of_subring _
#align is_integral_iff_is_integral_closure_finite isIntegral_iff_isIntegral_closure_finite
theorem Submodule.span_range_natDegree_eq_adjoin {R A} [CommRing R] [Semiring A] [Algebra R A]
{x : A} {f : R[X]} (hf : f.Monic) (hfx : aeval x f = 0) :
span R (Finset.image (x ^ ·) (Finset.range (natDegree f))) =
Subalgebra.toSubmodule (Algebra.adjoin R {x}) := by
nontriviality A
have hf1 : f ≠ 1 := by rintro rfl; simp [one_ne_zero' A] at hfx
refine (span_le.mpr fun s hs ↦ ?_).antisymm fun r hr ↦ ?_
· rcases Finset.mem_image.1 hs with ⟨k, -, rfl⟩
exact (Algebra.adjoin R {x}).pow_mem (Algebra.subset_adjoin rfl) k
rw [Subalgebra.mem_toSubmodule, Algebra.adjoin_singleton_eq_range_aeval] at hr
rcases (aeval x).mem_range.mp hr with ⟨p, rfl⟩
rw [← modByMonic_add_div p hf, map_add, map_mul, hfx,
zero_mul, add_zero, ← sum_C_mul_X_pow_eq (p %ₘ f), aeval_def, eval₂_sum, sum_def]
refine sum_mem fun k hkq ↦ ?_
rw [C_mul_X_pow_eq_monomial, eval₂_monomial, ← Algebra.smul_def]
exact smul_mem _ _ (subset_span <| Finset.mem_image_of_mem _ <| Finset.mem_range.mpr <|
(le_natDegree_of_mem_supp _ hkq).trans_lt <| natDegree_modByMonic_lt p hf hf1)
theorem IsIntegral.fg_adjoin_singleton {x : B} (hx : IsIntegral R x) :
(Algebra.adjoin R {x}).toSubmodule.FG := by
rcases hx with ⟨f, hfm, hfx⟩
use (Finset.range <| f.natDegree).image (x ^ ·)
exact span_range_natDegree_eq_adjoin hfm (by rwa [aeval_def])
theorem fg_adjoin_of_finite {s : Set A} (hfs : s.Finite) (his : ∀ x ∈ s, IsIntegral R x) :
(Algebra.adjoin R s).toSubmodule.FG :=
Set.Finite.induction_on hfs
(fun _ =>
⟨{1},
Submodule.ext fun x => by
rw [Algebra.adjoin_empty, Finset.coe_singleton, ← one_eq_span, Algebra.toSubmodule_bot]⟩)
(fun {a s} _ _ ih his => by
rw [← Set.union_singleton, Algebra.adjoin_union_coe_submodule]
exact
FG.mul (ih fun i hi => his i <| Set.mem_insert_of_mem a hi)
(his a <| Set.mem_insert a s).fg_adjoin_singleton)
his
#align fg_adjoin_of_finite fg_adjoin_of_finite
theorem isNoetherian_adjoin_finset [IsNoetherianRing R] (s : Finset A)
(hs : ∀ x ∈ s, IsIntegral R x) : IsNoetherian R (Algebra.adjoin R (s : Set A)) :=
isNoetherian_of_fg_of_noetherian _ (fg_adjoin_of_finite s.finite_toSet hs)
#align is_noetherian_adjoin_finset isNoetherian_adjoin_finset
instance Module.End.isIntegral {M : Type*} [AddCommGroup M] [Module R M] [Module.Finite R M] :
Algebra.IsIntegral R (Module.End R M) :=
⟨LinearMap.exists_monic_and_aeval_eq_zero R⟩
#align module.End.is_integral Module.End.isIntegral
variable (R)
theorem IsIntegral.of_finite [Module.Finite R B] (x : B) : IsIntegral R x :=
(isIntegral_algHom_iff (Algebra.lmul R B) Algebra.lmul_injective).mp
(Algebra.IsIntegral.isIntegral _)
variable (B)
instance Algebra.IsIntegral.of_finite [Module.Finite R B] : Algebra.IsIntegral R B :=
⟨.of_finite R⟩
#align algebra.is_integral.of_finite Algebra.IsIntegral.of_finite
variable {R B}
/-- If `S` is a sub-`R`-algebra of `A` and `S` is finitely-generated as an `R`-module,
then all elements of `S` are integral over `R`. -/
theorem IsIntegral.of_mem_of_fg {A} [Ring A] [Algebra R A] (S : Subalgebra R A)
(HS : S.toSubmodule.FG) (x : A) (hx : x ∈ S) : IsIntegral R x :=
have : Module.Finite R S := ⟨(fg_top _).mpr HS⟩
(isIntegral_algHom_iff S.val Subtype.val_injective).mpr (.of_finite R (⟨x, hx⟩ : S))
#align is_integral_of_mem_of_fg IsIntegral.of_mem_of_fg
theorem isIntegral_of_noetherian (_ : IsNoetherian R B) (x : B) : IsIntegral R x :=
.of_finite R x
#align is_integral_of_noetherian isIntegral_of_noetherian
theorem isIntegral_of_submodule_noetherian (S : Subalgebra R B)
(H : IsNoetherian R (Subalgebra.toSubmodule S)) (x : B) (hx : x ∈ S) : IsIntegral R x :=
.of_mem_of_fg _ ((fg_top _).mp <| H.noetherian _) _ hx
#align is_integral_of_submodule_noetherian isIntegral_of_submodule_noetherian
/-- Suppose `A` is an `R`-algebra, `M` is an `A`-module such that `a • m ≠ 0` for all non-zero `a`
and `m`. If `x : A` fixes a nontrivial f.g. `R`-submodule `N` of `M`, then `x` is `R`-integral. -/
theorem isIntegral_of_smul_mem_submodule {M : Type*} [AddCommGroup M] [Module R M] [Module A M]
[IsScalarTower R A M] [NoZeroSMulDivisors A M] (N : Submodule R M) (hN : N ≠ ⊥) (hN' : N.FG)
(x : A) (hx : ∀ n ∈ N, x • n ∈ N) : IsIntegral R x := by
let A' : Subalgebra R A :=
{ carrier := { x | ∀ n ∈ N, x • n ∈ N }
mul_mem' := fun {a b} ha hb n hn => smul_smul a b n ▸ ha _ (hb _ hn)
one_mem' := fun n hn => (one_smul A n).symm ▸ hn
add_mem' := fun {a b} ha hb n hn => (add_smul a b n).symm ▸ N.add_mem (ha _ hn) (hb _ hn)
zero_mem' := fun n _hn => (zero_smul A n).symm ▸ N.zero_mem
algebraMap_mem' := fun r n hn => (algebraMap_smul A r n).symm ▸ N.smul_mem r hn }
let f : A' →ₐ[R] Module.End R N :=
AlgHom.ofLinearMap
{ toFun := fun x => (DistribMulAction.toLinearMap R M x).restrict x.prop
-- Porting note: was
-- `fun x y => LinearMap.ext fun n => Subtype.ext <| add_smul x y n`
map_add' := by intros x y; ext; exact add_smul _ _ _
-- Porting note: was
-- `fun r s => LinearMap.ext fun n => Subtype.ext <| smul_assoc r s n`
map_smul' := by intros r s; ext; apply smul_assoc }
-- Porting note: the next two lines were
--`(LinearMap.ext fun n => Subtype.ext <| one_smul _ _) fun x y =>`
--`LinearMap.ext fun n => Subtype.ext <| mul_smul x y n`
(by ext; apply one_smul)
(by intros x y; ext; apply mul_smul)
obtain ⟨a, ha₁, ha₂⟩ : ∃ a ∈ N, a ≠ (0 : M) := by
by_contra! h'
apply hN
rwa [eq_bot_iff]
have : Function.Injective f := by
show Function.Injective f.toLinearMap
rw [← LinearMap.ker_eq_bot, eq_bot_iff]
intro s hs
have : s.1 • a = 0 := congr_arg Subtype.val (LinearMap.congr_fun hs ⟨a, ha₁⟩)
exact Subtype.ext ((eq_zero_or_eq_zero_of_smul_eq_zero this).resolve_right ha₂)
show IsIntegral R (A'.val ⟨x, hx⟩)
rw [isIntegral_algHom_iff A'.val Subtype.val_injective, ← isIntegral_algHom_iff f this]
haveI : Module.Finite R N := by rwa [Module.finite_def, Submodule.fg_top]
apply Algebra.IsIntegral.isIntegral
#align is_integral_of_smul_mem_submodule isIntegral_of_smul_mem_submodule
variable {f}
theorem RingHom.Finite.to_isIntegral (h : f.Finite) : f.IsIntegral :=
letI := f.toAlgebra
fun _ ↦ IsIntegral.of_mem_of_fg ⊤ h.1 _ trivial
#align ring_hom.finite.to_is_integral RingHom.Finite.to_isIntegral
alias RingHom.IsIntegral.of_finite := RingHom.Finite.to_isIntegral
#align ring_hom.is_integral.of_finite RingHom.IsIntegral.of_finite
/-- The [Kurosh problem](https://en.wikipedia.org/wiki/Kurosh_problem) asks to show that
this is still true when `A` is not necessarily commutative and `R` is a field, but it has
been solved in the negative. See https://arxiv.org/pdf/1706.02383.pdf for criteria for a
finitely generated algebraic (= integral) algebra over a field to be finite dimensional.
This could be an `instance`, but we tend to go from `Module.Finite` to `IsIntegral`/`IsAlgebraic`,
and making it an instance will cause the search to be complicated a lot.
-/
theorem Algebra.IsIntegral.finite [Algebra.IsIntegral R A] [h' : Algebra.FiniteType R A] :
Module.Finite R A :=
have ⟨s, hs⟩ := h'
⟨by apply hs ▸ fg_adjoin_of_finite s.finite_toSet fun x _ ↦ Algebra.IsIntegral.isIntegral x⟩
#align algebra.is_integral.finite Algebra.IsIntegral.finite
/-- finite = integral + finite type -/
theorem Algebra.finite_iff_isIntegral_and_finiteType :
Module.Finite R A ↔ Algebra.IsIntegral R A ∧ Algebra.FiniteType R A :=
⟨fun _ ↦ ⟨⟨.of_finite R⟩, inferInstance⟩, fun ⟨h, _⟩ ↦ h.finite⟩
#align algebra.finite_iff_is_integral_and_finite_type Algebra.finite_iff_isIntegral_and_finiteType
theorem RingHom.IsIntegral.to_finite (h : f.IsIntegral) (h' : f.FiniteType) : f.Finite :=
let _ := f.toAlgebra
let _ : Algebra.IsIntegral R S := ⟨h⟩
Algebra.IsIntegral.finite (h' := h')
#align ring_hom.is_integral.to_finite RingHom.IsIntegral.to_finite
alias RingHom.Finite.of_isIntegral_of_finiteType := RingHom.IsIntegral.to_finite
#align ring_hom.finite.of_is_integral_of_finite_type RingHom.Finite.of_isIntegral_of_finiteType
/-- finite = integral + finite type -/
theorem RingHom.finite_iff_isIntegral_and_finiteType : f.Finite ↔ f.IsIntegral ∧ f.FiniteType :=
⟨fun h ↦ ⟨h.to_isIntegral, h.to_finiteType⟩, fun ⟨h, h'⟩ ↦ h.to_finite h'⟩
#align ring_hom.finite_iff_is_integral_and_finite_type RingHom.finite_iff_isIntegral_and_finiteType
variable (f)
theorem RingHom.IsIntegralElem.of_mem_closure {x y z : S} (hx : f.IsIntegralElem x)
(hy : f.IsIntegralElem y) (hz : z ∈ Subring.closure ({x, y} : Set S)) : f.IsIntegralElem z := by
letI : Algebra R S := f.toAlgebra
have := (IsIntegral.fg_adjoin_singleton hx).mul (IsIntegral.fg_adjoin_singleton hy)
rw [← Algebra.adjoin_union_coe_submodule, Set.singleton_union] at this
exact
IsIntegral.of_mem_of_fg (Algebra.adjoin R {x, y}) this z
(Algebra.mem_adjoin_iff.2 <| Subring.closure_mono Set.subset_union_right hz)
#align ring_hom.is_integral_of_mem_closure RingHom.IsIntegralElem.of_mem_closure
nonrec theorem IsIntegral.of_mem_closure {x y z : A} (hx : IsIntegral R x) (hy : IsIntegral R y)
(hz : z ∈ Subring.closure ({x, y} : Set A)) : IsIntegral R z :=
hx.of_mem_closure (algebraMap R A) hy hz
#align is_integral_of_mem_closure IsIntegral.of_mem_closure
variable (f : R →+* B)
theorem RingHom.isIntegralElem_zero : f.IsIntegralElem 0 :=
f.map_zero ▸ f.isIntegralElem_map
#align ring_hom.is_integral_zero RingHom.isIntegralElem_zero
theorem isIntegral_zero : IsIntegral R (0 : B) :=
(algebraMap R B).isIntegralElem_zero
#align is_integral_zero isIntegral_zero
theorem RingHom.isIntegralElem_one : f.IsIntegralElem 1 :=
f.map_one ▸ f.isIntegralElem_map
#align ring_hom.is_integral_one RingHom.isIntegralElem_one
theorem isIntegral_one : IsIntegral R (1 : B) :=
(algebraMap R B).isIntegralElem_one
#align is_integral_one isIntegral_one
theorem RingHom.IsIntegralElem.add (f : R →+* S) {x y : S}
(hx : f.IsIntegralElem x) (hy : f.IsIntegralElem y) :
f.IsIntegralElem (x + y) :=
hx.of_mem_closure f hy <|
Subring.add_mem _ (Subring.subset_closure (Or.inl rfl)) (Subring.subset_closure (Or.inr rfl))
#align ring_hom.is_integral_add RingHom.IsIntegralElem.add
nonrec theorem IsIntegral.add {x y : A} (hx : IsIntegral R x) (hy : IsIntegral R y) :
IsIntegral R (x + y) :=
hx.add (algebraMap R A) hy
#align is_integral_add IsIntegral.add
variable (f : R →+* S)
-- can be generalized to noncommutative S.
theorem RingHom.IsIntegralElem.neg {x : S} (hx : f.IsIntegralElem x) : f.IsIntegralElem (-x) :=
hx.of_mem_closure f hx (Subring.neg_mem _ (Subring.subset_closure (Or.inl rfl)))
#align ring_hom.is_integral_neg RingHom.IsIntegralElem.neg
theorem IsIntegral.neg {x : B} (hx : IsIntegral R x) : IsIntegral R (-x) :=
.of_mem_of_fg _ hx.fg_adjoin_singleton _ (Subalgebra.neg_mem _ <| Algebra.subset_adjoin rfl)
#align is_integral_neg IsIntegral.neg
| Mathlib/RingTheory/IntegralClosure.lean | 398 | 400 | theorem RingHom.IsIntegralElem.sub {x y : S} (hx : f.IsIntegralElem x) (hy : f.IsIntegralElem y) :
f.IsIntegralElem (x - y) := by |
simpa only [sub_eq_add_neg] using hx.add f (hy.neg f)
|
/-
Copyright (c) 2021 Jordan Brown, Thomas Browning, Patrick Lutz. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jordan Brown, Thomas Browning, Patrick Lutz
-/
import Mathlib.Data.Fin.VecNotation
import Mathlib.GroupTheory.Abelianization
import Mathlib.GroupTheory.Perm.ViaEmbedding
import Mathlib.GroupTheory.Subgroup.Simple
import Mathlib.SetTheory.Cardinal.Basic
#align_import group_theory.solvable from "leanprover-community/mathlib"@"dc6c365e751e34d100e80fe6e314c3c3e0fd2988"
/-!
# Solvable Groups
In this file we introduce the notion of a solvable group. We define a solvable group as one whose
derived series is eventually trivial. This requires defining the commutator of two subgroups and
the derived series of a group.
## Main definitions
* `derivedSeries G n` : the `n`th term in the derived series of `G`, defined by iterating
`general_commutator` starting with the top subgroup
* `IsSolvable G` : the group `G` is solvable
-/
open Subgroup
variable {G G' : Type*} [Group G] [Group G'] {f : G →* G'}
section derivedSeries
variable (G)
/-- The derived series of the group `G`, obtained by starting from the subgroup `⊤` and repeatedly
taking the commutator of the previous subgroup with itself for `n` times. -/
def derivedSeries : ℕ → Subgroup G
| 0 => ⊤
| n + 1 => ⁅derivedSeries n, derivedSeries n⁆
#align derived_series derivedSeries
@[simp]
theorem derivedSeries_zero : derivedSeries G 0 = ⊤ :=
rfl
#align derived_series_zero derivedSeries_zero
@[simp]
theorem derivedSeries_succ (n : ℕ) :
derivedSeries G (n + 1) = ⁅derivedSeries G n, derivedSeries G n⁆ :=
rfl
#align derived_series_succ derivedSeries_succ
-- Porting note: had to provide inductive hypothesis explicitly
theorem derivedSeries_normal (n : ℕ) : (derivedSeries G n).Normal := by
induction' n with n ih
· exact (⊤ : Subgroup G).normal_of_characteristic
· exact @Subgroup.commutator_normal G _ (derivedSeries G n) (derivedSeries G n) ih ih
#align derived_series_normal derivedSeries_normal
-- Porting note: higher simp priority to restore Lean 3 behavior
@[simp 1100]
theorem derivedSeries_one : derivedSeries G 1 = commutator G :=
rfl
#align derived_series_one derivedSeries_one
end derivedSeries
section CommutatorMap
section DerivedSeriesMap
variable (f)
| Mathlib/GroupTheory/Solvable.lean | 76 | 80 | theorem map_derivedSeries_le_derivedSeries (n : ℕ) :
(derivedSeries G n).map f ≤ derivedSeries G' n := by |
induction' n with n ih
· exact le_top
· simp only [derivedSeries_succ, map_commutator, commutator_mono, ih]
|
/-
Copyright (c) 2022 Eric Wieser. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Eric Wieser
-/
import Mathlib.Analysis.NormedSpace.Exponential
import Mathlib.Analysis.Matrix
import Mathlib.LinearAlgebra.Matrix.ZPow
import Mathlib.LinearAlgebra.Matrix.Hermitian
import Mathlib.LinearAlgebra.Matrix.Symmetric
import Mathlib.Topology.UniformSpace.Matrix
#align_import analysis.normed_space.matrix_exponential from "leanprover-community/mathlib"@"1e3201306d4d9eb1fd54c60d7c4510ad5126f6f9"
/-!
# Lemmas about the matrix exponential
In this file, we provide results about `exp` on `Matrix`s over a topological or normed algebra.
Note that generic results over all topological spaces such as `NormedSpace.exp_zero`
can be used on matrices without issue, so are not repeated here.
The topological results specific to matrices are:
* `Matrix.exp_transpose`
* `Matrix.exp_conjTranspose`
* `Matrix.exp_diagonal`
* `Matrix.exp_blockDiagonal`
* `Matrix.exp_blockDiagonal'`
Lemmas like `NormedSpace.exp_add_of_commute` require a canonical norm on the type;
while there are multiple sensible choices for the norm of a `Matrix` (`Matrix.normedAddCommGroup`,
`Matrix.frobeniusNormedAddCommGroup`, `Matrix.linftyOpNormedAddCommGroup`), none of them
are canonical. In an application where a particular norm is chosen using
`attribute [local instance]`, then the usual lemmas about `NormedSpace.exp` are fine.
When choosing a norm is undesirable, the results in this file can be used.
In this file, we copy across the lemmas about `NormedSpace.exp`,
but hide the requirement for a norm inside the proof.
* `Matrix.exp_add_of_commute`
* `Matrix.exp_sum_of_commute`
* `Matrix.exp_nsmul`
* `Matrix.isUnit_exp`
* `Matrix.exp_units_conj`
* `Matrix.exp_units_conj'`
Additionally, we prove some results about `matrix.has_inv` and `matrix.div_inv_monoid`, as the
results for general rings are instead stated about `Ring.inverse`:
* `Matrix.exp_neg`
* `Matrix.exp_zsmul`
* `Matrix.exp_conj`
* `Matrix.exp_conj'`
## TODO
* Show that `Matrix.det (exp 𝕂 A) = exp 𝕂 (Matrix.trace A)`
## References
* https://en.wikipedia.org/wiki/Matrix_exponential
-/
open scoped Matrix
open NormedSpace -- For `exp`.
variable (𝕂 : Type*) {m n p : Type*} {n' : m → Type*} {𝔸 : Type*}
namespace Matrix
section Topological
section Ring
variable [Fintype m] [DecidableEq m] [Fintype n] [DecidableEq n] [∀ i, Fintype (n' i)]
[∀ i, DecidableEq (n' i)] [Field 𝕂] [Ring 𝔸] [TopologicalSpace 𝔸] [TopologicalRing 𝔸]
[Algebra 𝕂 𝔸] [T2Space 𝔸]
theorem exp_diagonal (v : m → 𝔸) : exp 𝕂 (diagonal v) = diagonal (exp 𝕂 v) := by
simp_rw [exp_eq_tsum, diagonal_pow, ← diagonal_smul, ← diagonal_tsum]
#align matrix.exp_diagonal Matrix.exp_diagonal
theorem exp_blockDiagonal (v : m → Matrix n n 𝔸) :
exp 𝕂 (blockDiagonal v) = blockDiagonal (exp 𝕂 v) := by
simp_rw [exp_eq_tsum, ← blockDiagonal_pow, ← blockDiagonal_smul, ← blockDiagonal_tsum]
#align matrix.exp_block_diagonal Matrix.exp_blockDiagonal
theorem exp_blockDiagonal' (v : ∀ i, Matrix (n' i) (n' i) 𝔸) :
exp 𝕂 (blockDiagonal' v) = blockDiagonal' (exp 𝕂 v) := by
simp_rw [exp_eq_tsum, ← blockDiagonal'_pow, ← blockDiagonal'_smul, ← blockDiagonal'_tsum]
#align matrix.exp_block_diagonal' Matrix.exp_blockDiagonal'
theorem exp_conjTranspose [StarRing 𝔸] [ContinuousStar 𝔸] (A : Matrix m m 𝔸) :
exp 𝕂 Aᴴ = (exp 𝕂 A)ᴴ :=
(star_exp A).symm
#align matrix.exp_conj_transpose Matrix.exp_conjTranspose
theorem IsHermitian.exp [StarRing 𝔸] [ContinuousStar 𝔸] {A : Matrix m m 𝔸} (h : A.IsHermitian) :
(exp 𝕂 A).IsHermitian :=
(exp_conjTranspose _ _).symm.trans <| congr_arg _ h
#align matrix.is_hermitian.exp Matrix.IsHermitian.exp
end Ring
section CommRing
variable [Fintype m] [DecidableEq m] [Field 𝕂] [CommRing 𝔸] [TopologicalSpace 𝔸] [TopologicalRing 𝔸]
[Algebra 𝕂 𝔸] [T2Space 𝔸]
theorem exp_transpose (A : Matrix m m 𝔸) : exp 𝕂 Aᵀ = (exp 𝕂 A)ᵀ := by
simp_rw [exp_eq_tsum, transpose_tsum, transpose_smul, transpose_pow]
#align matrix.exp_transpose Matrix.exp_transpose
theorem IsSymm.exp {A : Matrix m m 𝔸} (h : A.IsSymm) : (exp 𝕂 A).IsSymm :=
(exp_transpose _ _).symm.trans <| congr_arg _ h
#align matrix.is_symm.exp Matrix.IsSymm.exp
end CommRing
end Topological
section Normed
variable [RCLike 𝕂] [Fintype m] [DecidableEq m] [Fintype n] [DecidableEq n] [∀ i, Fintype (n' i)]
[∀ i, DecidableEq (n' i)] [NormedRing 𝔸] [NormedAlgebra 𝕂 𝔸] [CompleteSpace 𝔸]
nonrec theorem exp_add_of_commute (A B : Matrix m m 𝔸) (h : Commute A B) :
exp 𝕂 (A + B) = exp 𝕂 A * exp 𝕂 B := by
letI : SeminormedRing (Matrix m m 𝔸) := Matrix.linftyOpSemiNormedRing
letI : NormedRing (Matrix m m 𝔸) := Matrix.linftyOpNormedRing
letI : NormedAlgebra 𝕂 (Matrix m m 𝔸) := Matrix.linftyOpNormedAlgebra
exact exp_add_of_commute h
#align matrix.exp_add_of_commute Matrix.exp_add_of_commute
nonrec theorem exp_sum_of_commute {ι} (s : Finset ι) (f : ι → Matrix m m 𝔸)
(h : (s : Set ι).Pairwise fun i j => Commute (f i) (f j)) :
exp 𝕂 (∑ i ∈ s, f i) =
s.noncommProd (fun i => exp 𝕂 (f i)) fun i hi j hj _ => (h.of_refl hi hj).exp 𝕂 := by
letI : SeminormedRing (Matrix m m 𝔸) := Matrix.linftyOpSemiNormedRing
letI : NormedRing (Matrix m m 𝔸) := Matrix.linftyOpNormedRing
letI : NormedAlgebra 𝕂 (Matrix m m 𝔸) := Matrix.linftyOpNormedAlgebra
exact exp_sum_of_commute s f h
#align matrix.exp_sum_of_commute Matrix.exp_sum_of_commute
nonrec theorem exp_nsmul (n : ℕ) (A : Matrix m m 𝔸) : exp 𝕂 (n • A) = exp 𝕂 A ^ n := by
letI : SeminormedRing (Matrix m m 𝔸) := Matrix.linftyOpSemiNormedRing
letI : NormedRing (Matrix m m 𝔸) := Matrix.linftyOpNormedRing
letI : NormedAlgebra 𝕂 (Matrix m m 𝔸) := Matrix.linftyOpNormedAlgebra
exact exp_nsmul n A
#align matrix.exp_nsmul Matrix.exp_nsmul
nonrec theorem isUnit_exp (A : Matrix m m 𝔸) : IsUnit (exp 𝕂 A) := by
letI : SeminormedRing (Matrix m m 𝔸) := Matrix.linftyOpSemiNormedRing
letI : NormedRing (Matrix m m 𝔸) := Matrix.linftyOpNormedRing
letI : NormedAlgebra 𝕂 (Matrix m m 𝔸) := Matrix.linftyOpNormedAlgebra
exact isUnit_exp _ A
#align matrix.is_unit_exp Matrix.isUnit_exp
-- TODO(mathlib4#6607): fix elaboration so `val` isn't needed
nonrec theorem exp_units_conj (U : (Matrix m m 𝔸)ˣ) (A : Matrix m m 𝔸) :
exp 𝕂 (U.val * A * (U⁻¹).val) = U.val * exp 𝕂 A * (U⁻¹).val := by
letI : SeminormedRing (Matrix m m 𝔸) := Matrix.linftyOpSemiNormedRing
letI : NormedRing (Matrix m m 𝔸) := Matrix.linftyOpNormedRing
letI : NormedAlgebra 𝕂 (Matrix m m 𝔸) := Matrix.linftyOpNormedAlgebra
exact exp_units_conj _ U A
#align matrix.exp_units_conj Matrix.exp_units_conj
-- TODO(mathlib4#6607): fix elaboration so `val` isn't needed
theorem exp_units_conj' (U : (Matrix m m 𝔸)ˣ) (A : Matrix m m 𝔸) :
exp 𝕂 ((U⁻¹).val * A * U.val) = (U⁻¹).val * exp 𝕂 A * U.val :=
exp_units_conj 𝕂 U⁻¹ A
#align matrix.exp_units_conj' Matrix.exp_units_conj'
end Normed
section NormedComm
variable [RCLike 𝕂] [Fintype m] [DecidableEq m] [Fintype n] [DecidableEq n] [∀ i, Fintype (n' i)]
[∀ i, DecidableEq (n' i)] [NormedCommRing 𝔸] [NormedAlgebra 𝕂 𝔸] [CompleteSpace 𝔸]
theorem exp_neg (A : Matrix m m 𝔸) : exp 𝕂 (-A) = (exp 𝕂 A)⁻¹ := by
rw [nonsing_inv_eq_ring_inverse]
letI : SeminormedRing (Matrix m m 𝔸) := Matrix.linftyOpSemiNormedRing
letI : NormedRing (Matrix m m 𝔸) := Matrix.linftyOpNormedRing
letI : NormedAlgebra 𝕂 (Matrix m m 𝔸) := Matrix.linftyOpNormedAlgebra
exact (Ring.inverse_exp _ A).symm
#align matrix.exp_neg Matrix.exp_neg
| Mathlib/Analysis/NormedSpace/MatrixExponential.lean | 190 | 194 | theorem exp_zsmul (z : ℤ) (A : Matrix m m 𝔸) : exp 𝕂 (z • A) = exp 𝕂 A ^ z := by |
obtain ⟨n, rfl | rfl⟩ := z.eq_nat_or_neg
· rw [zpow_natCast, natCast_zsmul, exp_nsmul]
· have : IsUnit (exp 𝕂 A).det := (Matrix.isUnit_iff_isUnit_det _).mp (isUnit_exp _ _)
rw [Matrix.zpow_neg this, zpow_natCast, neg_smul, exp_neg, natCast_zsmul, exp_nsmul]
|
/-
Copyright (c) 2022 Andrew Yang. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Andrew Yang
-/
import Mathlib.Topology.Sets.Closeds
#align_import topology.noetherian_space from "leanprover-community/mathlib"@"dc6c365e751e34d100e80fe6e314c3c3e0fd2988"
/-!
# Noetherian space
A Noetherian space is a topological space that satisfies any of the following equivalent conditions:
- `WellFounded ((· > ·) : TopologicalSpace.Opens α → TopologicalSpace.Opens α → Prop)`
- `WellFounded ((· < ·) : TopologicalSpace.Closeds α → TopologicalSpace.Closeds α → Prop)`
- `∀ s : Set α, IsCompact s`
- `∀ s : TopologicalSpace.Opens α, IsCompact s`
The first is chosen as the definition, and the equivalence is shown in
`TopologicalSpace.noetherianSpace_TFAE`.
Many examples of noetherian spaces come from algebraic topology. For example, the underlying space
of a noetherian scheme (e.g., the spectrum of a noetherian ring) is noetherian.
## Main Results
- `TopologicalSpace.NoetherianSpace.set`: Every subspace of a noetherian space is noetherian.
- `TopologicalSpace.NoetherianSpace.isCompact`: Every set in a noetherian space is a compact set.
- `TopologicalSpace.noetherianSpace_TFAE`: Describes the equivalent definitions of noetherian
spaces.
- `TopologicalSpace.NoetherianSpace.range`: The image of a noetherian space under a continuous map
is noetherian.
- `TopologicalSpace.NoetherianSpace.iUnion`: The finite union of noetherian spaces is noetherian.
- `TopologicalSpace.NoetherianSpace.discrete`: A noetherian and Hausdorff space is discrete.
- `TopologicalSpace.NoetherianSpace.exists_finset_irreducible`: Every closed subset of a noetherian
space is a finite union of irreducible closed subsets.
- `TopologicalSpace.NoetherianSpace.finite_irreducibleComponents`: The number of irreducible
components of a noetherian space is finite.
-/
variable (α β : Type*) [TopologicalSpace α] [TopologicalSpace β]
namespace TopologicalSpace
/-- Type class for noetherian spaces. It is defined to be spaces whose open sets satisfies ACC. -/
@[mk_iff]
class NoetherianSpace : Prop where
wellFounded_opens : WellFounded ((· > ·) : Opens α → Opens α → Prop)
#align topological_space.noetherian_space TopologicalSpace.NoetherianSpace
theorem noetherianSpace_iff_opens : NoetherianSpace α ↔ ∀ s : Opens α, IsCompact (s : Set α) := by
rw [noetherianSpace_iff, CompleteLattice.wellFounded_iff_isSupFiniteCompact,
CompleteLattice.isSupFiniteCompact_iff_all_elements_compact]
exact forall_congr' Opens.isCompactElement_iff
#align topological_space.noetherian_space_iff_opens TopologicalSpace.noetherianSpace_iff_opens
instance (priority := 100) NoetherianSpace.compactSpace [h : NoetherianSpace α] : CompactSpace α :=
⟨(noetherianSpace_iff_opens α).mp h ⊤⟩
#align topological_space.noetherian_space.compact_space TopologicalSpace.NoetherianSpace.compactSpace
variable {α β}
/-- In a Noetherian space, all sets are compact. -/
protected theorem NoetherianSpace.isCompact [NoetherianSpace α] (s : Set α) : IsCompact s := by
refine isCompact_iff_finite_subcover.2 fun U hUo hs => ?_
rcases ((noetherianSpace_iff_opens α).mp ‹_› ⟨⋃ i, U i, isOpen_iUnion hUo⟩).elim_finite_subcover U
hUo Set.Subset.rfl with ⟨t, ht⟩
exact ⟨t, hs.trans ht⟩
#align topological_space.noetherian_space.is_compact TopologicalSpace.NoetherianSpace.isCompact
-- Porting note: fixed NS
protected theorem _root_.Inducing.noetherianSpace [NoetherianSpace α] {i : β → α}
(hi : Inducing i) : NoetherianSpace β :=
(noetherianSpace_iff_opens _).2 fun _ => hi.isCompact_iff.2 (NoetherianSpace.isCompact _)
#align topological_space.inducing.noetherian_space Inducing.noetherianSpace
/-- [Stacks: Lemma 0052 (1)](https://stacks.math.columbia.edu/tag/0052)-/
instance NoetherianSpace.set [NoetherianSpace α] (s : Set α) : NoetherianSpace s :=
inducing_subtype_val.noetherianSpace
#align topological_space.noetherian_space.set TopologicalSpace.NoetherianSpace.set
variable (α)
open List in
theorem noetherianSpace_TFAE :
TFAE [NoetherianSpace α,
WellFounded fun s t : Closeds α => s < t,
∀ s : Set α, IsCompact s,
∀ s : Opens α, IsCompact (s : Set α)] := by
tfae_have 1 ↔ 2
· refine (noetherianSpace_iff α).trans (Opens.compl_bijective.2.wellFounded_iff ?_)
exact (@OrderIso.compl (Set α)).lt_iff_lt.symm
tfae_have 1 ↔ 4
· exact noetherianSpace_iff_opens α
tfae_have 1 → 3
· exact @NoetherianSpace.isCompact α _
tfae_have 3 → 4
· exact fun h s => h s
tfae_finish
#align topological_space.noetherian_space_tfae TopologicalSpace.noetherianSpace_TFAE
variable {α}
theorem noetherianSpace_iff_isCompact : NoetherianSpace α ↔ ∀ s : Set α, IsCompact s :=
(noetherianSpace_TFAE α).out 0 2
theorem NoetherianSpace.wellFounded_closeds [NoetherianSpace α] :
WellFounded fun s t : Closeds α => s < t :=
Iff.mp ((noetherianSpace_TFAE α).out 0 1) ‹_›
instance {α} : NoetherianSpace (CofiniteTopology α) := by
simp only [noetherianSpace_iff_isCompact, isCompact_iff_ultrafilter_le_nhds,
CofiniteTopology.nhds_eq, Ultrafilter.le_sup_iff, Filter.le_principal_iff]
intro s f hs
rcases f.le_cofinite_or_eq_pure with (hf | ⟨a, rfl⟩)
· rcases Filter.nonempty_of_mem hs with ⟨a, ha⟩
exact ⟨a, ha, Or.inr hf⟩
· exact ⟨a, hs, Or.inl le_rfl⟩
theorem noetherianSpace_of_surjective [NoetherianSpace α] (f : α → β) (hf : Continuous f)
(hf' : Function.Surjective f) : NoetherianSpace β :=
noetherianSpace_iff_isCompact.2 <| (Set.image_surjective.mpr hf').forall.2 fun s =>
(NoetherianSpace.isCompact s).image hf
#align topological_space.noetherian_space_of_surjective TopologicalSpace.noetherianSpace_of_surjective
theorem noetherianSpace_iff_of_homeomorph (f : α ≃ₜ β) : NoetherianSpace α ↔ NoetherianSpace β :=
⟨fun _ => noetherianSpace_of_surjective f f.continuous f.surjective,
fun _ => noetherianSpace_of_surjective f.symm f.symm.continuous f.symm.surjective⟩
#align topological_space.noetherian_space_iff_of_homeomorph TopologicalSpace.noetherianSpace_iff_of_homeomorph
theorem NoetherianSpace.range [NoetherianSpace α] (f : α → β) (hf : Continuous f) :
NoetherianSpace (Set.range f) :=
noetherianSpace_of_surjective (Set.rangeFactorization f) (hf.subtype_mk _)
Set.surjective_onto_range
#align topological_space.noetherian_space.range TopologicalSpace.NoetherianSpace.range
theorem noetherianSpace_set_iff (s : Set α) :
NoetherianSpace s ↔ ∀ t, t ⊆ s → IsCompact t := by
simp only [noetherianSpace_iff_isCompact, embedding_subtype_val.isCompact_iff,
Subtype.forall_set_subtype]
#align topological_space.noetherian_space_set_iff TopologicalSpace.noetherianSpace_set_iff
@[simp]
theorem noetherian_univ_iff : NoetherianSpace (Set.univ : Set α) ↔ NoetherianSpace α :=
noetherianSpace_iff_of_homeomorph (Homeomorph.Set.univ α)
#align topological_space.noetherian_univ_iff TopologicalSpace.noetherian_univ_iff
theorem NoetherianSpace.iUnion {ι : Type*} (f : ι → Set α) [Finite ι]
[hf : ∀ i, NoetherianSpace (f i)] : NoetherianSpace (⋃ i, f i) := by
simp_rw [noetherianSpace_set_iff] at hf ⊢
intro t ht
rw [← Set.inter_eq_left.mpr ht, Set.inter_iUnion]
exact isCompact_iUnion fun i => hf i _ Set.inter_subset_right
#align topological_space.noetherian_space.Union TopologicalSpace.NoetherianSpace.iUnion
-- This is not an instance since it makes a loop with `t2_space_discrete`.
theorem NoetherianSpace.discrete [NoetherianSpace α] [T2Space α] : DiscreteTopology α :=
⟨eq_bot_iff.mpr fun _ _ => isClosed_compl_iff.mp (NoetherianSpace.isCompact _).isClosed⟩
#align topological_space.noetherian_space.discrete TopologicalSpace.NoetherianSpace.discrete
attribute [local instance] NoetherianSpace.discrete
/-- Spaces that are both Noetherian and Hausdorff are finite. -/
theorem NoetherianSpace.finite [NoetherianSpace α] [T2Space α] : Finite α :=
Finite.of_finite_univ (NoetherianSpace.isCompact Set.univ).finite_of_discrete
#align topological_space.noetherian_space.finite TopologicalSpace.NoetherianSpace.finite
instance (priority := 100) Finite.to_noetherianSpace [Finite α] : NoetherianSpace α :=
⟨Finite.wellFounded_of_trans_of_irrefl _⟩
#align topological_space.finite.to_noetherian_space TopologicalSpace.Finite.to_noetherianSpace
/-- In a Noetherian space, every closed set is a finite union of irreducible closed sets. -/
| Mathlib/Topology/NoetherianSpace.lean | 175 | 191 | theorem NoetherianSpace.exists_finite_set_closeds_irreducible [NoetherianSpace α] (s : Closeds α) :
∃ S : Set (Closeds α), S.Finite ∧ (∀ t ∈ S, IsIrreducible (t : Set α)) ∧ s = sSup S := by |
apply wellFounded_closeds.induction s; clear s
intro s H
rcases eq_or_ne s ⊥ with rfl | h₀
· use ∅; simp
· by_cases h₁ : IsPreirreducible (s : Set α)
· replace h₁ : IsIrreducible (s : Set α) := ⟨Closeds.coe_nonempty.2 h₀, h₁⟩
use {s}; simp [h₁]
· simp only [isPreirreducible_iff_closed_union_closed, not_forall, not_or] at h₁
obtain ⟨z₁, z₂, hz₁, hz₂, h, hz₁', hz₂'⟩ := h₁
lift z₁ to Closeds α using hz₁
lift z₂ to Closeds α using hz₂
rcases H (s ⊓ z₁) (inf_lt_left.2 hz₁') with ⟨S₁, hSf₁, hS₁, h₁⟩
rcases H (s ⊓ z₂) (inf_lt_left.2 hz₂') with ⟨S₂, hSf₂, hS₂, h₂⟩
refine ⟨S₁ ∪ S₂, hSf₁.union hSf₂, Set.union_subset_iff.2 ⟨hS₁, hS₂⟩, ?_⟩
rwa [sSup_union, ← h₁, ← h₂, ← inf_sup_left, left_eq_inf]
|
/-
Copyright (c) 2021 Kexing Ying. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kexing Ying
-/
import Mathlib.MeasureTheory.Decomposition.SignedHahn
import Mathlib.MeasureTheory.Measure.MutuallySingular
#align_import measure_theory.decomposition.jordan from "leanprover-community/mathlib"@"70a4f2197832bceab57d7f41379b2592d1110570"
/-!
# Jordan decomposition
This file proves the existence and uniqueness of the Jordan decomposition for signed measures.
The Jordan decomposition theorem states that, given a signed measure `s`, there exists a
unique pair of mutually singular measures `μ` and `ν`, such that `s = μ - ν`.
The Jordan decomposition theorem for measures is a corollary of the Hahn decomposition theorem and
is useful for the Lebesgue decomposition theorem.
## Main definitions
* `MeasureTheory.JordanDecomposition`: a Jordan decomposition of a measurable space is a
pair of mutually singular finite measures. We say `j` is a Jordan decomposition of a signed
measure `s` if `s = j.posPart - j.negPart`.
* `MeasureTheory.SignedMeasure.toJordanDecomposition`: the Jordan decomposition of a
signed measure.
* `MeasureTheory.SignedMeasure.toJordanDecompositionEquiv`: is the `Equiv` between
`MeasureTheory.SignedMeasure` and `MeasureTheory.JordanDecomposition` formed by
`MeasureTheory.SignedMeasure.toJordanDecomposition`.
## Main results
* `MeasureTheory.SignedMeasure.toSignedMeasure_toJordanDecomposition` : the Jordan
decomposition theorem.
* `MeasureTheory.JordanDecomposition.toSignedMeasure_injective` : the Jordan decomposition of a
signed measure is unique.
## Tags
Jordan decomposition theorem
-/
noncomputable section
open scoped Classical MeasureTheory ENNReal NNReal
variable {α β : Type*} [MeasurableSpace α]
namespace MeasureTheory
/-- A Jordan decomposition of a measurable space is a pair of mutually singular,
finite measures. -/
@[ext]
structure JordanDecomposition (α : Type*) [MeasurableSpace α] where
(posPart negPart : Measure α)
[posPart_finite : IsFiniteMeasure posPart]
[negPart_finite : IsFiniteMeasure negPart]
mutuallySingular : posPart ⟂ₘ negPart
#align measure_theory.jordan_decomposition MeasureTheory.JordanDecomposition
#align measure_theory.jordan_decomposition.pos_part MeasureTheory.JordanDecomposition.posPart
#align measure_theory.jordan_decomposition.neg_part MeasureTheory.JordanDecomposition.negPart
#align measure_theory.jordan_decomposition.pos_part_finite MeasureTheory.JordanDecomposition.posPart_finite
#align measure_theory.jordan_decomposition.neg_part_finite MeasureTheory.JordanDecomposition.negPart_finite
#align measure_theory.jordan_decomposition.mutually_singular MeasureTheory.JordanDecomposition.mutuallySingular
attribute [instance] JordanDecomposition.posPart_finite
attribute [instance] JordanDecomposition.negPart_finite
namespace JordanDecomposition
open Measure VectorMeasure
variable (j : JordanDecomposition α)
instance instZero : Zero (JordanDecomposition α) where zero := ⟨0, 0, MutuallySingular.zero_right⟩
#align measure_theory.jordan_decomposition.has_zero MeasureTheory.JordanDecomposition.instZero
instance instInhabited : Inhabited (JordanDecomposition α) where default := 0
#align measure_theory.jordan_decomposition.inhabited MeasureTheory.JordanDecomposition.instInhabited
instance instInvolutiveNeg : InvolutiveNeg (JordanDecomposition α) where
neg j := ⟨j.negPart, j.posPart, j.mutuallySingular.symm⟩
neg_neg _ := JordanDecomposition.ext _ _ rfl rfl
#align measure_theory.jordan_decomposition.has_involutive_neg MeasureTheory.JordanDecomposition.instInvolutiveNeg
instance instSMul : SMul ℝ≥0 (JordanDecomposition α) where
smul r j :=
⟨r • j.posPart, r • j.negPart,
MutuallySingular.smul _ (MutuallySingular.smul _ j.mutuallySingular.symm).symm⟩
#align measure_theory.jordan_decomposition.has_smul MeasureTheory.JordanDecomposition.instSMul
instance instSMulReal : SMul ℝ (JordanDecomposition α) where
smul r j := if 0 ≤ r then r.toNNReal • j else -((-r).toNNReal • j)
#align measure_theory.jordan_decomposition.has_smul_real MeasureTheory.JordanDecomposition.instSMulReal
@[simp]
theorem zero_posPart : (0 : JordanDecomposition α).posPart = 0 :=
rfl
#align measure_theory.jordan_decomposition.zero_pos_part MeasureTheory.JordanDecomposition.zero_posPart
@[simp]
theorem zero_negPart : (0 : JordanDecomposition α).negPart = 0 :=
rfl
#align measure_theory.jordan_decomposition.zero_neg_part MeasureTheory.JordanDecomposition.zero_negPart
@[simp]
theorem neg_posPart : (-j).posPart = j.negPart :=
rfl
#align measure_theory.jordan_decomposition.neg_pos_part MeasureTheory.JordanDecomposition.neg_posPart
@[simp]
theorem neg_negPart : (-j).negPart = j.posPart :=
rfl
#align measure_theory.jordan_decomposition.neg_neg_part MeasureTheory.JordanDecomposition.neg_negPart
@[simp]
theorem smul_posPart (r : ℝ≥0) : (r • j).posPart = r • j.posPart :=
rfl
#align measure_theory.jordan_decomposition.smul_pos_part MeasureTheory.JordanDecomposition.smul_posPart
@[simp]
theorem smul_negPart (r : ℝ≥0) : (r • j).negPart = r • j.negPart :=
rfl
#align measure_theory.jordan_decomposition.smul_neg_part MeasureTheory.JordanDecomposition.smul_negPart
theorem real_smul_def (r : ℝ) (j : JordanDecomposition α) :
r • j = if 0 ≤ r then r.toNNReal • j else -((-r).toNNReal • j) :=
rfl
#align measure_theory.jordan_decomposition.real_smul_def MeasureTheory.JordanDecomposition.real_smul_def
@[simp]
theorem coe_smul (r : ℝ≥0) : (r : ℝ) • j = r • j := by
-- Porting note: replaced `show`
rw [real_smul_def, if_pos (NNReal.coe_nonneg r), Real.toNNReal_coe]
#align measure_theory.jordan_decomposition.coe_smul MeasureTheory.JordanDecomposition.coe_smul
theorem real_smul_nonneg (r : ℝ) (hr : 0 ≤ r) : r • j = r.toNNReal • j :=
dif_pos hr
#align measure_theory.jordan_decomposition.real_smul_nonneg MeasureTheory.JordanDecomposition.real_smul_nonneg
theorem real_smul_neg (r : ℝ) (hr : r < 0) : r • j = -((-r).toNNReal • j) :=
dif_neg (not_le.2 hr)
#align measure_theory.jordan_decomposition.real_smul_neg MeasureTheory.JordanDecomposition.real_smul_neg
theorem real_smul_posPart_nonneg (r : ℝ) (hr : 0 ≤ r) :
(r • j).posPart = r.toNNReal • j.posPart := by
rw [real_smul_def, ← smul_posPart, if_pos hr]
#align measure_theory.jordan_decomposition.real_smul_pos_part_nonneg MeasureTheory.JordanDecomposition.real_smul_posPart_nonneg
theorem real_smul_negPart_nonneg (r : ℝ) (hr : 0 ≤ r) :
(r • j).negPart = r.toNNReal • j.negPart := by
rw [real_smul_def, ← smul_negPart, if_pos hr]
#align measure_theory.jordan_decomposition.real_smul_neg_part_nonneg MeasureTheory.JordanDecomposition.real_smul_negPart_nonneg
theorem real_smul_posPart_neg (r : ℝ) (hr : r < 0) :
(r • j).posPart = (-r).toNNReal • j.negPart := by
rw [real_smul_def, ← smul_negPart, if_neg (not_le.2 hr), neg_posPart]
#align measure_theory.jordan_decomposition.real_smul_pos_part_neg MeasureTheory.JordanDecomposition.real_smul_posPart_neg
theorem real_smul_negPart_neg (r : ℝ) (hr : r < 0) :
(r • j).negPart = (-r).toNNReal • j.posPart := by
rw [real_smul_def, ← smul_posPart, if_neg (not_le.2 hr), neg_negPart]
#align measure_theory.jordan_decomposition.real_smul_neg_part_neg MeasureTheory.JordanDecomposition.real_smul_negPart_neg
/-- The signed measure associated with a Jordan decomposition. -/
def toSignedMeasure : SignedMeasure α :=
j.posPart.toSignedMeasure - j.negPart.toSignedMeasure
#align measure_theory.jordan_decomposition.to_signed_measure MeasureTheory.JordanDecomposition.toSignedMeasure
theorem toSignedMeasure_zero : (0 : JordanDecomposition α).toSignedMeasure = 0 := by
ext1 i hi
-- Porting note: replaced `erw` by adding further lemmas
rw [toSignedMeasure, toSignedMeasure_sub_apply hi, zero_posPart, zero_negPart, sub_self,
VectorMeasure.coe_zero, Pi.zero_apply]
#align measure_theory.jordan_decomposition.to_signed_measure_zero MeasureTheory.JordanDecomposition.toSignedMeasure_zero
theorem toSignedMeasure_neg : (-j).toSignedMeasure = -j.toSignedMeasure := by
ext1 i hi
-- Porting note: removed `rfl` after the `rw` by adding further steps.
rw [neg_apply, toSignedMeasure, toSignedMeasure, toSignedMeasure_sub_apply hi,
toSignedMeasure_sub_apply hi, neg_sub, neg_posPart, neg_negPart]
#align measure_theory.jordan_decomposition.to_signed_measure_neg MeasureTheory.JordanDecomposition.toSignedMeasure_neg
theorem toSignedMeasure_smul (r : ℝ≥0) : (r • j).toSignedMeasure = r • j.toSignedMeasure := by
ext1 i hi
rw [VectorMeasure.smul_apply, toSignedMeasure, toSignedMeasure,
toSignedMeasure_sub_apply hi, toSignedMeasure_sub_apply hi, smul_sub, smul_posPart,
smul_negPart, ← ENNReal.toReal_smul, ← ENNReal.toReal_smul, Measure.smul_apply,
Measure.smul_apply]
#align measure_theory.jordan_decomposition.to_signed_measure_smul MeasureTheory.JordanDecomposition.toSignedMeasure_smul
/-- A Jordan decomposition provides a Hahn decomposition. -/
theorem exists_compl_positive_negative :
∃ S : Set α,
MeasurableSet S ∧
j.toSignedMeasure ≤[S] 0 ∧
0 ≤[Sᶜ] j.toSignedMeasure ∧ j.posPart S = 0 ∧ j.negPart Sᶜ = 0 := by
obtain ⟨S, hS₁, hS₂, hS₃⟩ := j.mutuallySingular
refine ⟨S, hS₁, ?_, ?_, hS₂, hS₃⟩
· refine restrict_le_restrict_of_subset_le _ _ fun A hA hA₁ => ?_
rw [toSignedMeasure, toSignedMeasure_sub_apply hA,
show j.posPart A = 0 from nonpos_iff_eq_zero.1 (hS₂ ▸ measure_mono hA₁), ENNReal.zero_toReal,
zero_sub, neg_le, zero_apply, neg_zero]
exact ENNReal.toReal_nonneg
· refine restrict_le_restrict_of_subset_le _ _ fun A hA hA₁ => ?_
rw [toSignedMeasure, toSignedMeasure_sub_apply hA,
show j.negPart A = 0 from nonpos_iff_eq_zero.1 (hS₃ ▸ measure_mono hA₁), ENNReal.zero_toReal,
sub_zero]
exact ENNReal.toReal_nonneg
#align measure_theory.jordan_decomposition.exists_compl_positive_negative MeasureTheory.JordanDecomposition.exists_compl_positive_negative
end JordanDecomposition
namespace SignedMeasure
open scoped Classical
open JordanDecomposition Measure Set VectorMeasure
variable {s : SignedMeasure α} {μ ν : Measure α} [IsFiniteMeasure μ] [IsFiniteMeasure ν]
/-- Given a signed measure `s`, `s.toJordanDecomposition` is the Jordan decomposition `j`,
such that `s = j.toSignedMeasure`. This property is known as the Jordan decomposition
theorem, and is shown by
`MeasureTheory.SignedMeasure.toSignedMeasure_toJordanDecomposition`. -/
def toJordanDecomposition (s : SignedMeasure α) : JordanDecomposition α :=
let i := s.exists_compl_positive_negative.choose
let hi := s.exists_compl_positive_negative.choose_spec
{ posPart := s.toMeasureOfZeroLE i hi.1 hi.2.1
negPart := s.toMeasureOfLEZero iᶜ hi.1.compl hi.2.2
posPart_finite := inferInstance
negPart_finite := inferInstance
mutuallySingular := by
refine ⟨iᶜ, hi.1.compl, ?_, ?_⟩
-- Porting note: added `← NNReal.eq_iff`
· rw [toMeasureOfZeroLE_apply _ _ hi.1 hi.1.compl]; simp [← NNReal.eq_iff]
· rw [toMeasureOfLEZero_apply _ _ hi.1.compl hi.1.compl.compl]; simp [← NNReal.eq_iff] }
#align measure_theory.signed_measure.to_jordan_decomposition MeasureTheory.SignedMeasure.toJordanDecomposition
theorem toJordanDecomposition_spec (s : SignedMeasure α) :
∃ (i : Set α) (hi₁ : MeasurableSet i) (hi₂ : 0 ≤[i] s) (hi₃ : s ≤[iᶜ] 0),
s.toJordanDecomposition.posPart = s.toMeasureOfZeroLE i hi₁ hi₂ ∧
s.toJordanDecomposition.negPart = s.toMeasureOfLEZero iᶜ hi₁.compl hi₃ := by
set i := s.exists_compl_positive_negative.choose
obtain ⟨hi₁, hi₂, hi₃⟩ := s.exists_compl_positive_negative.choose_spec
exact ⟨i, hi₁, hi₂, hi₃, rfl, rfl⟩
#align measure_theory.signed_measure.to_jordan_decomposition_spec MeasureTheory.SignedMeasure.toJordanDecomposition_spec
/-- **The Jordan decomposition theorem**: Given a signed measure `s`, there exists a pair of
mutually singular measures `μ` and `ν` such that `s = μ - ν`. In this case, the measures `μ`
and `ν` are given by `s.toJordanDecomposition.posPart` and
`s.toJordanDecomposition.negPart` respectively.
Note that we use `MeasureTheory.JordanDecomposition.toSignedMeasure` to represent the
signed measure corresponding to
`s.toJordanDecomposition.posPart - s.toJordanDecomposition.negPart`. -/
@[simp]
theorem toSignedMeasure_toJordanDecomposition (s : SignedMeasure α) :
s.toJordanDecomposition.toSignedMeasure = s := by
obtain ⟨i, hi₁, hi₂, hi₃, hμ, hν⟩ := s.toJordanDecomposition_spec
simp only [JordanDecomposition.toSignedMeasure, hμ, hν]
ext k hk
rw [toSignedMeasure_sub_apply hk, toMeasureOfZeroLE_apply _ hi₂ hi₁ hk,
toMeasureOfLEZero_apply _ hi₃ hi₁.compl hk]
simp only [ENNReal.coe_toReal, NNReal.coe_mk, ENNReal.some_eq_coe, sub_neg_eq_add]
rw [← of_union _ (MeasurableSet.inter hi₁ hk) (MeasurableSet.inter hi₁.compl hk),
Set.inter_comm i, Set.inter_comm iᶜ, Set.inter_union_compl _ _]
exact (disjoint_compl_right.inf_left _).inf_right _
#align measure_theory.signed_measure.to_signed_measure_to_jordan_decomposition MeasureTheory.SignedMeasure.toSignedMeasure_toJordanDecomposition
section
variable {u v w : Set α}
/-- A subset `v` of a null-set `w` has zero measure if `w` is a subset of a positive set `u`. -/
theorem subset_positive_null_set (hu : MeasurableSet u) (hv : MeasurableSet v)
(hw : MeasurableSet w) (hsu : 0 ≤[u] s) (hw₁ : s w = 0) (hw₂ : w ⊆ u) (hwt : v ⊆ w) :
s v = 0 := by
have : s v + s (w \ v) = 0 := by
rw [← hw₁, ← of_union Set.disjoint_sdiff_right hv (hw.diff hv), Set.union_diff_self,
Set.union_eq_self_of_subset_left hwt]
have h₁ := nonneg_of_zero_le_restrict _ (restrict_le_restrict_subset _ _ hu hsu (hwt.trans hw₂))
have h₂ : 0 ≤ s (w \ v) :=
nonneg_of_zero_le_restrict _
(restrict_le_restrict_subset _ _ hu hsu (diff_subset.trans hw₂))
linarith
#align measure_theory.signed_measure.subset_positive_null_set MeasureTheory.SignedMeasure.subset_positive_null_set
/-- A subset `v` of a null-set `w` has zero measure if `w` is a subset of a negative set `u`. -/
theorem subset_negative_null_set (hu : MeasurableSet u) (hv : MeasurableSet v)
(hw : MeasurableSet w) (hsu : s ≤[u] 0) (hw₁ : s w = 0) (hw₂ : w ⊆ u) (hwt : v ⊆ w) :
s v = 0 := by
rw [← s.neg_le_neg_iff _ hu, neg_zero] at hsu
have := subset_positive_null_set hu hv hw hsu
simp only [Pi.neg_apply, neg_eq_zero, coe_neg] at this
exact this hw₁ hw₂ hwt
#align measure_theory.signed_measure.subset_negative_null_set MeasureTheory.SignedMeasure.subset_negative_null_set
open scoped symmDiff
/-- If the symmetric difference of two positive sets is a null-set, then so are the differences
between the two sets. -/
theorem of_diff_eq_zero_of_symmDiff_eq_zero_positive (hu : MeasurableSet u) (hv : MeasurableSet v)
(hsu : 0 ≤[u] s) (hsv : 0 ≤[v] s) (hs : s (u ∆ v) = 0) : s (u \ v) = 0 ∧ s (v \ u) = 0 := by
rw [restrict_le_restrict_iff] at hsu hsv
on_goal 1 =>
have a := hsu (hu.diff hv) diff_subset
have b := hsv (hv.diff hu) diff_subset
erw [of_union (Set.disjoint_of_subset_left diff_subset disjoint_sdiff_self_right)
(hu.diff hv) (hv.diff hu)] at hs
rw [zero_apply] at a b
constructor
all_goals first | linarith | assumption
#align measure_theory.signed_measure.of_diff_eq_zero_of_symm_diff_eq_zero_positive MeasureTheory.SignedMeasure.of_diff_eq_zero_of_symmDiff_eq_zero_positive
/-- If the symmetric difference of two negative sets is a null-set, then so are the differences
between the two sets. -/
theorem of_diff_eq_zero_of_symmDiff_eq_zero_negative (hu : MeasurableSet u) (hv : MeasurableSet v)
(hsu : s ≤[u] 0) (hsv : s ≤[v] 0) (hs : s (u ∆ v) = 0) : s (u \ v) = 0 ∧ s (v \ u) = 0 := by
rw [← s.neg_le_neg_iff _ hu, neg_zero] at hsu
rw [← s.neg_le_neg_iff _ hv, neg_zero] at hsv
have := of_diff_eq_zero_of_symmDiff_eq_zero_positive hu hv hsu hsv
simp only [Pi.neg_apply, neg_eq_zero, coe_neg] at this
exact this hs
#align measure_theory.signed_measure.of_diff_eq_zero_of_symm_diff_eq_zero_negative MeasureTheory.SignedMeasure.of_diff_eq_zero_of_symmDiff_eq_zero_negative
theorem of_inter_eq_of_symmDiff_eq_zero_positive (hu : MeasurableSet u) (hv : MeasurableSet v)
(hw : MeasurableSet w) (hsu : 0 ≤[u] s) (hsv : 0 ≤[v] s) (hs : s (u ∆ v) = 0) :
s (w ∩ u) = s (w ∩ v) := by
have hwuv : s ((w ∩ u) ∆ (w ∩ v)) = 0 := by
refine
subset_positive_null_set (hu.union hv) ((hw.inter hu).symmDiff (hw.inter hv))
(hu.symmDiff hv) (restrict_le_restrict_union _ _ hu hsu hv hsv) hs
Set.symmDiff_subset_union ?_
rw [← Set.inter_symmDiff_distrib_left]
exact Set.inter_subset_right
obtain ⟨huv, hvu⟩ :=
of_diff_eq_zero_of_symmDiff_eq_zero_positive (hw.inter hu) (hw.inter hv)
(restrict_le_restrict_subset _ _ hu hsu (w.inter_subset_right))
(restrict_le_restrict_subset _ _ hv hsv (w.inter_subset_right)) hwuv
rw [← of_diff_of_diff_eq_zero (hw.inter hu) (hw.inter hv) hvu, huv, zero_add]
#align measure_theory.signed_measure.of_inter_eq_of_symm_diff_eq_zero_positive MeasureTheory.SignedMeasure.of_inter_eq_of_symmDiff_eq_zero_positive
theorem of_inter_eq_of_symmDiff_eq_zero_negative (hu : MeasurableSet u) (hv : MeasurableSet v)
(hw : MeasurableSet w) (hsu : s ≤[u] 0) (hsv : s ≤[v] 0) (hs : s (u ∆ v) = 0) :
s (w ∩ u) = s (w ∩ v) := by
rw [← s.neg_le_neg_iff _ hu, neg_zero] at hsu
rw [← s.neg_le_neg_iff _ hv, neg_zero] at hsv
have := of_inter_eq_of_symmDiff_eq_zero_positive hu hv hw hsu hsv
simp only [Pi.neg_apply, neg_inj, neg_eq_zero, coe_neg] at this
exact this hs
#align measure_theory.signed_measure.of_inter_eq_of_symm_diff_eq_zero_negative MeasureTheory.SignedMeasure.of_inter_eq_of_symmDiff_eq_zero_negative
end
end SignedMeasure
namespace JordanDecomposition
open Measure VectorMeasure SignedMeasure Function
private theorem eq_of_posPart_eq_posPart {j₁ j₂ : JordanDecomposition α}
(hj : j₁.posPart = j₂.posPart) (hj' : j₁.toSignedMeasure = j₂.toSignedMeasure) : j₁ = j₂ := by
ext1
· exact hj
· rw [← toSignedMeasure_eq_toSignedMeasure_iff]
-- Porting note: golfed
unfold toSignedMeasure at hj'
simp_rw [hj, sub_right_inj] at hj'
exact hj'
/-- The Jordan decomposition of a signed measure is unique. -/
theorem toSignedMeasure_injective : Injective <| @JordanDecomposition.toSignedMeasure α _ := by
/- The main idea is that two Jordan decompositions of a signed measure provide two
Hahn decompositions for that measure. Then, from `of_symmDiff_compl_positive_negative`,
the symmetric difference of the two Hahn decompositions has measure zero, thus, allowing us to
show the equality of the underlying measures of the Jordan decompositions. -/
intro j₁ j₂ hj
-- obtain the two Hahn decompositions from the Jordan decompositions
obtain ⟨S, hS₁, hS₂, hS₃, hS₄, hS₅⟩ := j₁.exists_compl_positive_negative
obtain ⟨T, hT₁, hT₂, hT₃, hT₄, hT₅⟩ := j₂.exists_compl_positive_negative
rw [← hj] at hT₂ hT₃
-- the symmetric differences of the two Hahn decompositions have measure zero
obtain ⟨hST₁, -⟩ :=
of_symmDiff_compl_positive_negative hS₁.compl hT₁.compl ⟨hS₃, (compl_compl S).symm ▸ hS₂⟩
⟨hT₃, (compl_compl T).symm ▸ hT₂⟩
-- it suffices to show the Jordan decompositions have the same positive parts
refine eq_of_posPart_eq_posPart ?_ hj
ext1 i hi
-- we see that the positive parts of the two Jordan decompositions are equal to their
-- associated signed measures restricted on their associated Hahn decompositions
have hμ₁ : (j₁.posPart i).toReal = j₁.toSignedMeasure (i ∩ Sᶜ) := by
rw [toSignedMeasure, toSignedMeasure_sub_apply (hi.inter hS₁.compl),
show j₁.negPart (i ∩ Sᶜ) = 0 from
nonpos_iff_eq_zero.1 (hS₅ ▸ measure_mono Set.inter_subset_right),
ENNReal.zero_toReal, sub_zero]
conv_lhs => rw [← Set.inter_union_compl i S]
rw [measure_union,
show j₁.posPart (i ∩ S) = 0 from
nonpos_iff_eq_zero.1 (hS₄ ▸ measure_mono Set.inter_subset_right),
zero_add]
· refine
Set.disjoint_of_subset_left Set.inter_subset_right
(Set.disjoint_of_subset_right Set.inter_subset_right disjoint_compl_right)
· exact hi.inter hS₁.compl
have hμ₂ : (j₂.posPart i).toReal = j₂.toSignedMeasure (i ∩ Tᶜ) := by
rw [toSignedMeasure, toSignedMeasure_sub_apply (hi.inter hT₁.compl),
show j₂.negPart (i ∩ Tᶜ) = 0 from
nonpos_iff_eq_zero.1 (hT₅ ▸ measure_mono Set.inter_subset_right),
ENNReal.zero_toReal, sub_zero]
conv_lhs => rw [← Set.inter_union_compl i T]
rw [measure_union,
show j₂.posPart (i ∩ T) = 0 from
nonpos_iff_eq_zero.1 (hT₄ ▸ measure_mono Set.inter_subset_right),
zero_add]
· exact
Set.disjoint_of_subset_left Set.inter_subset_right
(Set.disjoint_of_subset_right Set.inter_subset_right disjoint_compl_right)
· exact hi.inter hT₁.compl
-- since the two signed measures associated with the Jordan decompositions are the same,
-- and the symmetric difference of the Hahn decompositions have measure zero, the result follows
rw [← ENNReal.toReal_eq_toReal (measure_ne_top _ _) (measure_ne_top _ _), hμ₁, hμ₂, ← hj]
exact of_inter_eq_of_symmDiff_eq_zero_positive hS₁.compl hT₁.compl hi hS₃ hT₃ hST₁
#align measure_theory.jordan_decomposition.to_signed_measure_injective MeasureTheory.JordanDecomposition.toSignedMeasure_injective
@[simp]
theorem toJordanDecomposition_toSignedMeasure (j : JordanDecomposition α) :
j.toSignedMeasure.toJordanDecomposition = j :=
(@toSignedMeasure_injective _ _ j j.toSignedMeasure.toJordanDecomposition (by simp)).symm
#align measure_theory.jordan_decomposition.to_jordan_decomposition_to_signed_measure MeasureTheory.JordanDecomposition.toJordanDecomposition_toSignedMeasure
end JordanDecomposition
namespace SignedMeasure
open JordanDecomposition
/-- `MeasureTheory.SignedMeasure.toJordanDecomposition` and
`MeasureTheory.JordanDecomposition.toSignedMeasure` form an `Equiv`. -/
@[simps apply symm_apply]
def toJordanDecompositionEquiv (α : Type*) [MeasurableSpace α] :
SignedMeasure α ≃ JordanDecomposition α where
toFun := toJordanDecomposition
invFun := toSignedMeasure
left_inv := toSignedMeasure_toJordanDecomposition
right_inv := toJordanDecomposition_toSignedMeasure
#align measure_theory.signed_measure.to_jordan_decomposition_equiv MeasureTheory.SignedMeasure.toJordanDecompositionEquiv
#align measure_theory.signed_measure.to_jordan_decomposition_equiv_apply MeasureTheory.SignedMeasure.toJordanDecompositionEquiv_apply
#align measure_theory.signed_measure.to_jordan_decomposition_equiv_symm_apply MeasureTheory.SignedMeasure.toJordanDecompositionEquiv_symm_apply
theorem toJordanDecomposition_zero : (0 : SignedMeasure α).toJordanDecomposition = 0 := by
apply toSignedMeasure_injective
simp [toSignedMeasure_zero]
#align measure_theory.signed_measure.to_jordan_decomposition_zero MeasureTheory.SignedMeasure.toJordanDecomposition_zero
theorem toJordanDecomposition_neg (s : SignedMeasure α) :
(-s).toJordanDecomposition = -s.toJordanDecomposition := by
apply toSignedMeasure_injective
simp [toSignedMeasure_neg]
#align measure_theory.signed_measure.to_jordan_decomposition_neg MeasureTheory.SignedMeasure.toJordanDecomposition_neg
theorem toJordanDecomposition_smul (s : SignedMeasure α) (r : ℝ≥0) :
(r • s).toJordanDecomposition = r • s.toJordanDecomposition := by
apply toSignedMeasure_injective
simp [toSignedMeasure_smul]
#align measure_theory.signed_measure.to_jordan_decomposition_smul MeasureTheory.SignedMeasure.toJordanDecomposition_smul
private theorem toJordanDecomposition_smul_real_nonneg (s : SignedMeasure α) (r : ℝ)
(hr : 0 ≤ r) : (r • s).toJordanDecomposition = r • s.toJordanDecomposition := by
lift r to ℝ≥0 using hr
rw [JordanDecomposition.coe_smul, ← toJordanDecomposition_smul]
rfl
theorem toJordanDecomposition_smul_real (s : SignedMeasure α) (r : ℝ) :
(r • s).toJordanDecomposition = r • s.toJordanDecomposition := by
by_cases hr : 0 ≤ r
· exact toJordanDecomposition_smul_real_nonneg s r hr
· ext1
· rw [real_smul_posPart_neg _ _ (not_le.1 hr),
show r • s = -(-r • s) by rw [neg_smul, neg_neg], toJordanDecomposition_neg, neg_posPart,
toJordanDecomposition_smul_real_nonneg, ← smul_negPart, real_smul_nonneg]
all_goals exact Left.nonneg_neg_iff.2 (le_of_lt (not_le.1 hr))
· rw [real_smul_negPart_neg _ _ (not_le.1 hr),
show r • s = -(-r • s) by rw [neg_smul, neg_neg], toJordanDecomposition_neg, neg_negPart,
toJordanDecomposition_smul_real_nonneg, ← smul_posPart, real_smul_nonneg]
all_goals exact Left.nonneg_neg_iff.2 (le_of_lt (not_le.1 hr))
#align measure_theory.signed_measure.to_jordan_decomposition_smul_real MeasureTheory.SignedMeasure.toJordanDecomposition_smul_real
theorem toJordanDecomposition_eq {s : SignedMeasure α} {j : JordanDecomposition α}
(h : s = j.toSignedMeasure) : s.toJordanDecomposition = j := by
rw [h, toJordanDecomposition_toSignedMeasure]
#align measure_theory.signed_measure.to_jordan_decomposition_eq MeasureTheory.SignedMeasure.toJordanDecomposition_eq
/-- The total variation of a signed measure. -/
def totalVariation (s : SignedMeasure α) : Measure α :=
s.toJordanDecomposition.posPart + s.toJordanDecomposition.negPart
#align measure_theory.signed_measure.total_variation MeasureTheory.SignedMeasure.totalVariation
theorem totalVariation_zero : (0 : SignedMeasure α).totalVariation = 0 := by
simp [totalVariation, toJordanDecomposition_zero]
#align measure_theory.signed_measure.total_variation_zero MeasureTheory.SignedMeasure.totalVariation_zero
theorem totalVariation_neg (s : SignedMeasure α) : (-s).totalVariation = s.totalVariation := by
simp [totalVariation, toJordanDecomposition_neg, add_comm]
#align measure_theory.signed_measure.total_variation_neg MeasureTheory.SignedMeasure.totalVariation_neg
theorem null_of_totalVariation_zero (s : SignedMeasure α) {i : Set α}
(hs : s.totalVariation i = 0) : s i = 0 := by
rw [totalVariation, Measure.coe_add, Pi.add_apply, add_eq_zero_iff] at hs
rw [← toSignedMeasure_toJordanDecomposition s, toSignedMeasure, VectorMeasure.coe_sub,
Pi.sub_apply, Measure.toSignedMeasure_apply, Measure.toSignedMeasure_apply]
by_cases hi : MeasurableSet i
· rw [if_pos hi, if_pos hi]; simp [hs.1, hs.2]
· simp [if_neg hi]
#align measure_theory.signed_measure.null_of_total_variation_zero MeasureTheory.SignedMeasure.null_of_totalVariation_zero
theorem absolutelyContinuous_ennreal_iff (s : SignedMeasure α) (μ : VectorMeasure α ℝ≥0∞) :
s ≪ᵥ μ ↔ s.totalVariation ≪ μ.ennrealToMeasure := by
constructor <;> intro h
· refine Measure.AbsolutelyContinuous.mk fun S hS₁ hS₂ => ?_
obtain ⟨i, hi₁, hi₂, hi₃, hpos, hneg⟩ := s.toJordanDecomposition_spec
rw [totalVariation, Measure.add_apply, hpos, hneg, toMeasureOfZeroLE_apply _ _ _ hS₁,
toMeasureOfLEZero_apply _ _ _ hS₁]
rw [← VectorMeasure.AbsolutelyContinuous.ennrealToMeasure] at h
-- Porting note: added `← NNReal.eq_iff`
simp [h (measure_mono_null (i.inter_subset_right) hS₂),
h (measure_mono_null (iᶜ.inter_subset_right) hS₂), ← NNReal.eq_iff]
· refine VectorMeasure.AbsolutelyContinuous.mk fun S hS₁ hS₂ => ?_
rw [← VectorMeasure.ennrealToMeasure_apply hS₁] at hS₂
exact null_of_totalVariation_zero s (h hS₂)
#align measure_theory.signed_measure.absolutely_continuous_ennreal_iff MeasureTheory.SignedMeasure.absolutelyContinuous_ennreal_iff
| Mathlib/MeasureTheory/Decomposition/Jordan.lean | 535 | 546 | theorem totalVariation_absolutelyContinuous_iff (s : SignedMeasure α) (μ : Measure α) :
s.totalVariation ≪ μ ↔
s.toJordanDecomposition.posPart ≪ μ ∧ s.toJordanDecomposition.negPart ≪ μ := by |
constructor <;> intro h
· constructor
all_goals
refine Measure.AbsolutelyContinuous.mk fun S _ hS₂ => ?_
have := h hS₂
rw [totalVariation, Measure.add_apply, add_eq_zero_iff] at this
exacts [this.1, this.2]
· refine Measure.AbsolutelyContinuous.mk fun S _ hS₂ => ?_
rw [totalVariation, Measure.add_apply, h.1 hS₂, h.2 hS₂, add_zero]
|
/-
Copyright (c) 2019 Abhimanyu Pallavi Sudhir. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Abhimanyu Pallavi Sudhir
-/
import Mathlib.Order.Filter.FilterProduct
import Mathlib.Analysis.SpecificLimits.Basic
#align_import data.real.hyperreal from "leanprover-community/mathlib"@"f2ce6086713c78a7f880485f7917ea547a215982"
/-!
# Construction of the hyperreal numbers as an ultraproduct of real sequences.
-/
open scoped Classical
open Filter Germ Topology
/-- Hyperreal numbers on the ultrafilter extending the cofinite filter -/
def Hyperreal : Type :=
Germ (hyperfilter ℕ : Filter ℕ) ℝ deriving Inhabited
#align hyperreal Hyperreal
namespace Hyperreal
@[inherit_doc] notation "ℝ*" => Hyperreal
noncomputable instance : LinearOrderedField ℝ* :=
inferInstanceAs (LinearOrderedField (Germ _ _))
/-- Natural embedding `ℝ → ℝ*`. -/
@[coe] def ofReal : ℝ → ℝ* := const
noncomputable instance : CoeTC ℝ ℝ* := ⟨ofReal⟩
@[simp, norm_cast]
theorem coe_eq_coe {x y : ℝ} : (x : ℝ*) = y ↔ x = y :=
Germ.const_inj
#align hyperreal.coe_eq_coe Hyperreal.coe_eq_coe
theorem coe_ne_coe {x y : ℝ} : (x : ℝ*) ≠ y ↔ x ≠ y :=
coe_eq_coe.not
#align hyperreal.coe_ne_coe Hyperreal.coe_ne_coe
@[simp, norm_cast]
theorem coe_eq_zero {x : ℝ} : (x : ℝ*) = 0 ↔ x = 0 :=
coe_eq_coe
#align hyperreal.coe_eq_zero Hyperreal.coe_eq_zero
@[simp, norm_cast]
theorem coe_eq_one {x : ℝ} : (x : ℝ*) = 1 ↔ x = 1 :=
coe_eq_coe
#align hyperreal.coe_eq_one Hyperreal.coe_eq_one
@[norm_cast]
theorem coe_ne_zero {x : ℝ} : (x : ℝ*) ≠ 0 ↔ x ≠ 0 :=
coe_ne_coe
#align hyperreal.coe_ne_zero Hyperreal.coe_ne_zero
@[norm_cast]
theorem coe_ne_one {x : ℝ} : (x : ℝ*) ≠ 1 ↔ x ≠ 1 :=
coe_ne_coe
#align hyperreal.coe_ne_one Hyperreal.coe_ne_one
@[simp, norm_cast]
theorem coe_one : ↑(1 : ℝ) = (1 : ℝ*) :=
rfl
#align hyperreal.coe_one Hyperreal.coe_one
@[simp, norm_cast]
theorem coe_zero : ↑(0 : ℝ) = (0 : ℝ*) :=
rfl
#align hyperreal.coe_zero Hyperreal.coe_zero
@[simp, norm_cast]
theorem coe_inv (x : ℝ) : ↑x⁻¹ = (x⁻¹ : ℝ*) :=
rfl
#align hyperreal.coe_inv Hyperreal.coe_inv
@[simp, norm_cast]
theorem coe_neg (x : ℝ) : ↑(-x) = (-x : ℝ*) :=
rfl
#align hyperreal.coe_neg Hyperreal.coe_neg
@[simp, norm_cast]
theorem coe_add (x y : ℝ) : ↑(x + y) = (x + y : ℝ*) :=
rfl
#align hyperreal.coe_add Hyperreal.coe_add
#noalign hyperreal.coe_bit0
#noalign hyperreal.coe_bit1
-- See note [no_index around OfNat.ofNat]
@[simp, norm_cast]
theorem coe_ofNat (n : ℕ) [n.AtLeastTwo] :
((no_index (OfNat.ofNat n : ℝ)) : ℝ*) = OfNat.ofNat n :=
rfl
@[simp, norm_cast]
theorem coe_mul (x y : ℝ) : ↑(x * y) = (x * y : ℝ*) :=
rfl
#align hyperreal.coe_mul Hyperreal.coe_mul
@[simp, norm_cast]
theorem coe_div (x y : ℝ) : ↑(x / y) = (x / y : ℝ*) :=
rfl
#align hyperreal.coe_div Hyperreal.coe_div
@[simp, norm_cast]
theorem coe_sub (x y : ℝ) : ↑(x - y) = (x - y : ℝ*) :=
rfl
#align hyperreal.coe_sub Hyperreal.coe_sub
@[simp, norm_cast]
theorem coe_le_coe {x y : ℝ} : (x : ℝ*) ≤ y ↔ x ≤ y :=
Germ.const_le_iff
#align hyperreal.coe_le_coe Hyperreal.coe_le_coe
@[simp, norm_cast]
theorem coe_lt_coe {x y : ℝ} : (x : ℝ*) < y ↔ x < y :=
Germ.const_lt_iff
#align hyperreal.coe_lt_coe Hyperreal.coe_lt_coe
@[simp, norm_cast]
theorem coe_nonneg {x : ℝ} : 0 ≤ (x : ℝ*) ↔ 0 ≤ x :=
coe_le_coe
#align hyperreal.coe_nonneg Hyperreal.coe_nonneg
@[simp, norm_cast]
theorem coe_pos {x : ℝ} : 0 < (x : ℝ*) ↔ 0 < x :=
coe_lt_coe
#align hyperreal.coe_pos Hyperreal.coe_pos
@[simp, norm_cast]
theorem coe_abs (x : ℝ) : ((|x| : ℝ) : ℝ*) = |↑x| :=
const_abs x
#align hyperreal.coe_abs Hyperreal.coe_abs
@[simp, norm_cast]
theorem coe_max (x y : ℝ) : ((max x y : ℝ) : ℝ*) = max ↑x ↑y :=
Germ.const_max _ _
#align hyperreal.coe_max Hyperreal.coe_max
@[simp, norm_cast]
theorem coe_min (x y : ℝ) : ((min x y : ℝ) : ℝ*) = min ↑x ↑y :=
Germ.const_min _ _
#align hyperreal.coe_min Hyperreal.coe_min
/-- Construct a hyperreal number from a sequence of real numbers. -/
def ofSeq (f : ℕ → ℝ) : ℝ* := (↑f : Germ (hyperfilter ℕ : Filter ℕ) ℝ)
#align hyperreal.of_seq Hyperreal.ofSeq
-- Porting note (#10756): new lemma
theorem ofSeq_surjective : Function.Surjective ofSeq := Quot.exists_rep
theorem ofSeq_lt_ofSeq {f g : ℕ → ℝ} : ofSeq f < ofSeq g ↔ ∀ᶠ n in hyperfilter ℕ, f n < g n :=
Germ.coe_lt
/-- A sample infinitesimal hyperreal-/
noncomputable def epsilon : ℝ* :=
ofSeq fun n => n⁻¹
#align hyperreal.epsilon Hyperreal.epsilon
/-- A sample infinite hyperreal-/
noncomputable def omega : ℝ* := ofSeq Nat.cast
#align hyperreal.omega Hyperreal.omega
@[inherit_doc] scoped notation "ε" => Hyperreal.epsilon
@[inherit_doc] scoped notation "ω" => Hyperreal.omega
@[simp]
theorem inv_omega : ω⁻¹ = ε :=
rfl
#align hyperreal.inv_omega Hyperreal.inv_omega
@[simp]
theorem inv_epsilon : ε⁻¹ = ω :=
@inv_inv _ _ ω
#align hyperreal.inv_epsilon Hyperreal.inv_epsilon
theorem omega_pos : 0 < ω :=
Germ.coe_pos.2 <| Nat.hyperfilter_le_atTop <| (eventually_gt_atTop 0).mono fun _ ↦
Nat.cast_pos.2
#align hyperreal.omega_pos Hyperreal.omega_pos
theorem epsilon_pos : 0 < ε :=
inv_pos_of_pos omega_pos
#align hyperreal.epsilon_pos Hyperreal.epsilon_pos
theorem epsilon_ne_zero : ε ≠ 0 :=
epsilon_pos.ne'
#align hyperreal.epsilon_ne_zero Hyperreal.epsilon_ne_zero
theorem omega_ne_zero : ω ≠ 0 :=
omega_pos.ne'
#align hyperreal.omega_ne_zero Hyperreal.omega_ne_zero
theorem epsilon_mul_omega : ε * ω = 1 :=
@inv_mul_cancel _ _ ω omega_ne_zero
#align hyperreal.epsilon_mul_omega Hyperreal.epsilon_mul_omega
theorem lt_of_tendsto_zero_of_pos {f : ℕ → ℝ} (hf : Tendsto f atTop (𝓝 0)) :
∀ {r : ℝ}, 0 < r → ofSeq f < (r : ℝ*) := fun hr ↦
ofSeq_lt_ofSeq.2 <| (hf.eventually <| gt_mem_nhds hr).filter_mono Nat.hyperfilter_le_atTop
#align hyperreal.lt_of_tendsto_zero_of_pos Hyperreal.lt_of_tendsto_zero_of_pos
theorem neg_lt_of_tendsto_zero_of_pos {f : ℕ → ℝ} (hf : Tendsto f atTop (𝓝 0)) :
∀ {r : ℝ}, 0 < r → (-r : ℝ*) < ofSeq f := fun hr =>
have hg := hf.neg
neg_lt_of_neg_lt (by rw [neg_zero] at hg; exact lt_of_tendsto_zero_of_pos hg hr)
#align hyperreal.neg_lt_of_tendsto_zero_of_pos Hyperreal.neg_lt_of_tendsto_zero_of_pos
theorem gt_of_tendsto_zero_of_neg {f : ℕ → ℝ} (hf : Tendsto f atTop (𝓝 0)) :
∀ {r : ℝ}, r < 0 → (r : ℝ*) < ofSeq f := fun {r} hr => by
rw [← neg_neg r, coe_neg]; exact neg_lt_of_tendsto_zero_of_pos hf (neg_pos.mpr hr)
#align hyperreal.gt_of_tendsto_zero_of_neg Hyperreal.gt_of_tendsto_zero_of_neg
theorem epsilon_lt_pos (x : ℝ) : 0 < x → ε < x :=
lt_of_tendsto_zero_of_pos tendsto_inverse_atTop_nhds_zero_nat
#align hyperreal.epsilon_lt_pos Hyperreal.epsilon_lt_pos
/-- Standard part predicate -/
def IsSt (x : ℝ*) (r : ℝ) :=
∀ δ : ℝ, 0 < δ → (r - δ : ℝ*) < x ∧ x < r + δ
#align hyperreal.is_st Hyperreal.IsSt
/-- Standard part function: like a "round" to ℝ instead of ℤ -/
noncomputable def st : ℝ* → ℝ := fun x => if h : ∃ r, IsSt x r then Classical.choose h else 0
#align hyperreal.st Hyperreal.st
/-- A hyperreal number is infinitesimal if its standard part is 0 -/
def Infinitesimal (x : ℝ*) :=
IsSt x 0
#align hyperreal.infinitesimal Hyperreal.Infinitesimal
/-- A hyperreal number is positive infinite if it is larger than all real numbers -/
def InfinitePos (x : ℝ*) :=
∀ r : ℝ, ↑r < x
#align hyperreal.infinite_pos Hyperreal.InfinitePos
/-- A hyperreal number is negative infinite if it is smaller than all real numbers -/
def InfiniteNeg (x : ℝ*) :=
∀ r : ℝ, x < r
#align hyperreal.infinite_neg Hyperreal.InfiniteNeg
/-- A hyperreal number is infinite if it is infinite positive or infinite negative -/
def Infinite (x : ℝ*) :=
InfinitePos x ∨ InfiniteNeg x
#align hyperreal.infinite Hyperreal.Infinite
/-!
### Some facts about `st`
-/
theorem isSt_ofSeq_iff_tendsto {f : ℕ → ℝ} {r : ℝ} :
IsSt (ofSeq f) r ↔ Tendsto f (hyperfilter ℕ) (𝓝 r) :=
Iff.trans (forall₂_congr fun _ _ ↦ (ofSeq_lt_ofSeq.and ofSeq_lt_ofSeq).trans eventually_and.symm)
(nhds_basis_Ioo_pos _).tendsto_right_iff.symm
theorem isSt_iff_tendsto {x : ℝ*} {r : ℝ} : IsSt x r ↔ x.Tendsto (𝓝 r) := by
rcases ofSeq_surjective x with ⟨f, rfl⟩
exact isSt_ofSeq_iff_tendsto
theorem isSt_of_tendsto {f : ℕ → ℝ} {r : ℝ} (hf : Tendsto f atTop (𝓝 r)) : IsSt (ofSeq f) r :=
isSt_ofSeq_iff_tendsto.2 <| hf.mono_left Nat.hyperfilter_le_atTop
#align hyperreal.is_st_of_tendsto Hyperreal.isSt_of_tendsto
-- Porting note: moved up, renamed
protected theorem IsSt.lt {x y : ℝ*} {r s : ℝ} (hxr : IsSt x r) (hys : IsSt y s) (hrs : r < s) :
x < y := by
rcases ofSeq_surjective x with ⟨f, rfl⟩
rcases ofSeq_surjective y with ⟨g, rfl⟩
rw [isSt_ofSeq_iff_tendsto] at hxr hys
exact ofSeq_lt_ofSeq.2 <| hxr.eventually_lt hys hrs
#align hyperreal.lt_of_is_st_lt Hyperreal.IsSt.lt
theorem IsSt.unique {x : ℝ*} {r s : ℝ} (hr : IsSt x r) (hs : IsSt x s) : r = s := by
rcases ofSeq_surjective x with ⟨f, rfl⟩
rw [isSt_ofSeq_iff_tendsto] at hr hs
exact tendsto_nhds_unique hr hs
#align hyperreal.is_st_unique Hyperreal.IsSt.unique
theorem IsSt.st_eq {x : ℝ*} {r : ℝ} (hxr : IsSt x r) : st x = r := by
have h : ∃ r, IsSt x r := ⟨r, hxr⟩
rw [st, dif_pos h]
exact (Classical.choose_spec h).unique hxr
#align hyperreal.st_of_is_st Hyperreal.IsSt.st_eq
theorem IsSt.not_infinite {x : ℝ*} {r : ℝ} (h : IsSt x r) : ¬Infinite x := fun hi ↦
hi.elim (fun hp ↦ lt_asymm (h 1 one_pos).2 (hp (r + 1))) fun hn ↦
lt_asymm (h 1 one_pos).1 (hn (r - 1))
theorem not_infinite_of_exists_st {x : ℝ*} : (∃ r : ℝ, IsSt x r) → ¬Infinite x := fun ⟨_r, hr⟩ =>
hr.not_infinite
#align hyperreal.not_infinite_of_exists_st Hyperreal.not_infinite_of_exists_st
theorem Infinite.st_eq {x : ℝ*} (hi : Infinite x) : st x = 0 :=
dif_neg fun ⟨_r, hr⟩ ↦ hr.not_infinite hi
#align hyperreal.st_infinite Hyperreal.Infinite.st_eq
theorem isSt_sSup {x : ℝ*} (hni : ¬Infinite x) : IsSt x (sSup { y : ℝ | (y : ℝ*) < x }) :=
let S : Set ℝ := { y : ℝ | (y : ℝ*) < x }
let R : ℝ := sSup S
let ⟨r₁, hr₁⟩ := not_forall.mp (not_or.mp hni).2
let ⟨r₂, hr₂⟩ := not_forall.mp (not_or.mp hni).1
have HR₁ : S.Nonempty :=
⟨r₁ - 1, lt_of_lt_of_le (coe_lt_coe.2 <| sub_one_lt _) (not_lt.mp hr₁)⟩
have HR₂ : BddAbove S :=
⟨r₂, fun _y hy => le_of_lt (coe_lt_coe.1 (lt_of_lt_of_le hy (not_lt.mp hr₂)))⟩
fun δ hδ =>
⟨lt_of_not_le fun c =>
have hc : ∀ y ∈ S, y ≤ R - δ := fun _y hy =>
coe_le_coe.1 <| le_of_lt <| lt_of_lt_of_le hy c
not_lt_of_le (csSup_le HR₁ hc) <| sub_lt_self R hδ,
lt_of_not_le fun c =>
have hc : ↑(R + δ / 2) < x :=
lt_of_lt_of_le (add_lt_add_left (coe_lt_coe.2 (half_lt_self hδ)) R) c
not_lt_of_le (le_csSup HR₂ hc) <| (lt_add_iff_pos_right _).mpr <| half_pos hδ⟩
#align hyperreal.is_st_Sup Hyperreal.isSt_sSup
theorem exists_st_of_not_infinite {x : ℝ*} (hni : ¬Infinite x) : ∃ r : ℝ, IsSt x r :=
⟨sSup { y : ℝ | (y : ℝ*) < x }, isSt_sSup hni⟩
#align hyperreal.exists_st_of_not_infinite Hyperreal.exists_st_of_not_infinite
theorem st_eq_sSup {x : ℝ*} : st x = sSup { y : ℝ | (y : ℝ*) < x } := by
rcases _root_.em (Infinite x) with (hx|hx)
· rw [hx.st_eq]
cases hx with
| inl hx =>
convert Real.sSup_univ.symm
exact Set.eq_univ_of_forall hx
| inr hx =>
convert Real.sSup_empty.symm
exact Set.eq_empty_of_forall_not_mem fun y hy ↦ hy.out.not_lt (hx _)
· exact (isSt_sSup hx).st_eq
#align hyperreal.st_eq_Sup Hyperreal.st_eq_sSup
theorem exists_st_iff_not_infinite {x : ℝ*} : (∃ r : ℝ, IsSt x r) ↔ ¬Infinite x :=
⟨not_infinite_of_exists_st, exists_st_of_not_infinite⟩
#align hyperreal.exists_st_iff_not_infinite Hyperreal.exists_st_iff_not_infinite
theorem infinite_iff_not_exists_st {x : ℝ*} : Infinite x ↔ ¬∃ r : ℝ, IsSt x r :=
iff_not_comm.mp exists_st_iff_not_infinite
#align hyperreal.infinite_iff_not_exists_st Hyperreal.infinite_iff_not_exists_st
theorem IsSt.isSt_st {x : ℝ*} {r : ℝ} (hxr : IsSt x r) : IsSt x (st x) := by
rwa [hxr.st_eq]
#align hyperreal.is_st_st_of_is_st Hyperreal.IsSt.isSt_st
theorem isSt_st_of_exists_st {x : ℝ*} (hx : ∃ r : ℝ, IsSt x r) : IsSt x (st x) :=
let ⟨_r, hr⟩ := hx; hr.isSt_st
#align hyperreal.is_st_st_of_exists_st Hyperreal.isSt_st_of_exists_st
theorem isSt_st' {x : ℝ*} (hx : ¬Infinite x) : IsSt x (st x) :=
(isSt_sSup hx).isSt_st
#align hyperreal.is_st_st' Hyperreal.isSt_st'
theorem isSt_st {x : ℝ*} (hx : st x ≠ 0) : IsSt x (st x) :=
isSt_st' <| mt Infinite.st_eq hx
#align hyperreal.is_st_st Hyperreal.isSt_st
theorem isSt_refl_real (r : ℝ) : IsSt r r := isSt_ofSeq_iff_tendsto.2 tendsto_const_nhds
#align hyperreal.is_st_refl_real Hyperreal.isSt_refl_real
theorem st_id_real (r : ℝ) : st r = r := (isSt_refl_real r).st_eq
#align hyperreal.st_id_real Hyperreal.st_id_real
theorem eq_of_isSt_real {r s : ℝ} : IsSt r s → r = s :=
(isSt_refl_real r).unique
#align hyperreal.eq_of_is_st_real Hyperreal.eq_of_isSt_real
theorem isSt_real_iff_eq {r s : ℝ} : IsSt r s ↔ r = s :=
⟨eq_of_isSt_real, fun hrs => hrs ▸ isSt_refl_real r⟩
#align hyperreal.is_st_real_iff_eq Hyperreal.isSt_real_iff_eq
theorem isSt_symm_real {r s : ℝ} : IsSt r s ↔ IsSt s r := by
rw [isSt_real_iff_eq, isSt_real_iff_eq, eq_comm]
#align hyperreal.is_st_symm_real Hyperreal.isSt_symm_real
theorem isSt_trans_real {r s t : ℝ} : IsSt r s → IsSt s t → IsSt r t := by
rw [isSt_real_iff_eq, isSt_real_iff_eq, isSt_real_iff_eq]; exact Eq.trans
#align hyperreal.is_st_trans_real Hyperreal.isSt_trans_real
theorem isSt_inj_real {r₁ r₂ s : ℝ} (h1 : IsSt r₁ s) (h2 : IsSt r₂ s) : r₁ = r₂ :=
Eq.trans (eq_of_isSt_real h1) (eq_of_isSt_real h2).symm
#align hyperreal.is_st_inj_real Hyperreal.isSt_inj_real
theorem isSt_iff_abs_sub_lt_delta {x : ℝ*} {r : ℝ} : IsSt x r ↔ ∀ δ : ℝ, 0 < δ → |x - ↑r| < δ := by
simp only [abs_sub_lt_iff, sub_lt_iff_lt_add, IsSt, and_comm, add_comm]
#align hyperreal.is_st_iff_abs_sub_lt_delta Hyperreal.isSt_iff_abs_sub_lt_delta
theorem IsSt.map {x : ℝ*} {r : ℝ} (hxr : IsSt x r) {f : ℝ → ℝ} (hf : ContinuousAt f r) :
IsSt (x.map f) (f r) := by
rcases ofSeq_surjective x with ⟨g, rfl⟩
exact isSt_ofSeq_iff_tendsto.2 <| hf.tendsto.comp (isSt_ofSeq_iff_tendsto.1 hxr)
theorem IsSt.map₂ {x y : ℝ*} {r s : ℝ} (hxr : IsSt x r) (hys : IsSt y s) {f : ℝ → ℝ → ℝ}
(hf : ContinuousAt (Function.uncurry f) (r, s)) : IsSt (x.map₂ f y) (f r s) := by
rcases ofSeq_surjective x with ⟨x, rfl⟩
rcases ofSeq_surjective y with ⟨y, rfl⟩
rw [isSt_ofSeq_iff_tendsto] at hxr hys
exact isSt_ofSeq_iff_tendsto.2 <| hf.tendsto.comp (hxr.prod_mk_nhds hys)
theorem IsSt.add {x y : ℝ*} {r s : ℝ} (hxr : IsSt x r) (hys : IsSt y s) :
IsSt (x + y) (r + s) := hxr.map₂ hys continuous_add.continuousAt
#align hyperreal.is_st_add Hyperreal.IsSt.add
theorem IsSt.neg {x : ℝ*} {r : ℝ} (hxr : IsSt x r) : IsSt (-x) (-r) :=
hxr.map continuous_neg.continuousAt
#align hyperreal.is_st_neg Hyperreal.IsSt.neg
theorem IsSt.sub {x y : ℝ*} {r s : ℝ} (hxr : IsSt x r) (hys : IsSt y s) : IsSt (x - y) (r - s) :=
hxr.map₂ hys continuous_sub.continuousAt
#align hyperreal.is_st_sub Hyperreal.IsSt.sub
theorem IsSt.le {x y : ℝ*} {r s : ℝ} (hrx : IsSt x r) (hsy : IsSt y s) (hxy : x ≤ y) : r ≤ s :=
not_lt.1 fun h ↦ hxy.not_lt <| hsy.lt hrx h
#align hyperreal.is_st_le_of_le Hyperreal.IsSt.le
theorem st_le_of_le {x y : ℝ*} (hix : ¬Infinite x) (hiy : ¬Infinite y) : x ≤ y → st x ≤ st y :=
(isSt_st' hix).le (isSt_st' hiy)
#align hyperreal.st_le_of_le Hyperreal.st_le_of_le
theorem lt_of_st_lt {x y : ℝ*} (hix : ¬Infinite x) (hiy : ¬Infinite y) : st x < st y → x < y :=
(isSt_st' hix).lt (isSt_st' hiy)
#align hyperreal.lt_of_st_lt Hyperreal.lt_of_st_lt
/-!
### Basic lemmas about infinite
-/
theorem infinitePos_def {x : ℝ*} : InfinitePos x ↔ ∀ r : ℝ, ↑r < x := Iff.rfl
#align hyperreal.infinite_pos_def Hyperreal.infinitePos_def
theorem infiniteNeg_def {x : ℝ*} : InfiniteNeg x ↔ ∀ r : ℝ, x < r := Iff.rfl
#align hyperreal.infinite_neg_def Hyperreal.infiniteNeg_def
theorem InfinitePos.pos {x : ℝ*} (hip : InfinitePos x) : 0 < x := hip 0
#align hyperreal.pos_of_infinite_pos Hyperreal.InfinitePos.pos
theorem InfiniteNeg.lt_zero {x : ℝ*} : InfiniteNeg x → x < 0 := fun hin => hin 0
#align hyperreal.neg_of_infinite_neg Hyperreal.InfiniteNeg.lt_zero
theorem Infinite.ne_zero {x : ℝ*} (hI : Infinite x) : x ≠ 0 :=
hI.elim (fun hip => hip.pos.ne') fun hin => hin.lt_zero.ne
#align hyperreal.ne_zero_of_infinite Hyperreal.Infinite.ne_zero
theorem not_infinite_zero : ¬Infinite 0 := fun hI => hI.ne_zero rfl
#align hyperreal.not_infinite_zero Hyperreal.not_infinite_zero
theorem InfiniteNeg.not_infinitePos {x : ℝ*} : InfiniteNeg x → ¬InfinitePos x := fun hn hp =>
(hn 0).not_lt (hp 0)
#align hyperreal.not_infinite_pos_of_infinite_neg Hyperreal.InfiniteNeg.not_infinitePos
theorem InfinitePos.not_infiniteNeg {x : ℝ*} (hp : InfinitePos x) : ¬InfiniteNeg x := fun hn ↦
hn.not_infinitePos hp
#align hyperreal.not_infinite_neg_of_infinite_pos Hyperreal.InfinitePos.not_infiniteNeg
theorem InfinitePos.neg {x : ℝ*} : InfinitePos x → InfiniteNeg (-x) := fun hp r =>
neg_lt.mp (hp (-r))
#align hyperreal.infinite_neg_neg_of_infinite_pos Hyperreal.InfinitePos.neg
theorem InfiniteNeg.neg {x : ℝ*} : InfiniteNeg x → InfinitePos (-x) := fun hp r =>
lt_neg.mp (hp (-r))
#align hyperreal.infinite_pos_neg_of_infinite_neg Hyperreal.InfiniteNeg.neg
-- Porting note: swapped LHS with RHS; added @[simp]
@[simp] theorem infiniteNeg_neg {x : ℝ*} : InfiniteNeg (-x) ↔ InfinitePos x :=
⟨fun hin => neg_neg x ▸ hin.neg, InfinitePos.neg⟩
#align hyperreal.infinite_pos_iff_infinite_neg_neg Hyperreal.infiniteNeg_negₓ
-- Porting note: swapped LHS with RHS; added @[simp]
@[simp] theorem infinitePos_neg {x : ℝ*} : InfinitePos (-x) ↔ InfiniteNeg x :=
⟨fun hin => neg_neg x ▸ hin.neg, InfiniteNeg.neg⟩
#align hyperreal.infinite_neg_iff_infinite_pos_neg Hyperreal.infinitePos_negₓ
-- Porting note: swapped LHS with RHS; added @[simp]
@[simp] theorem infinite_neg {x : ℝ*} : Infinite (-x) ↔ Infinite x :=
or_comm.trans <| infiniteNeg_neg.or infinitePos_neg
#align hyperreal.infinite_iff_infinite_neg Hyperreal.infinite_negₓ
nonrec theorem Infinitesimal.not_infinite {x : ℝ*} (h : Infinitesimal x) : ¬Infinite x :=
h.not_infinite
#align hyperreal.not_infinite_of_infinitesimal Hyperreal.Infinitesimal.not_infinite
theorem Infinite.not_infinitesimal {x : ℝ*} (h : Infinite x) : ¬Infinitesimal x := fun h' ↦
h'.not_infinite h
#align hyperreal.not_infinitesimal_of_infinite Hyperreal.Infinite.not_infinitesimal
theorem InfinitePos.not_infinitesimal {x : ℝ*} (h : InfinitePos x) : ¬Infinitesimal x :=
Infinite.not_infinitesimal (Or.inl h)
#align hyperreal.not_infinitesimal_of_infinite_pos Hyperreal.InfinitePos.not_infinitesimal
theorem InfiniteNeg.not_infinitesimal {x : ℝ*} (h : InfiniteNeg x) : ¬Infinitesimal x :=
Infinite.not_infinitesimal (Or.inr h)
#align hyperreal.not_infinitesimal_of_infinite_neg Hyperreal.InfiniteNeg.not_infinitesimal
theorem infinitePos_iff_infinite_and_pos {x : ℝ*} : InfinitePos x ↔ Infinite x ∧ 0 < x :=
⟨fun hip => ⟨Or.inl hip, hip 0⟩, fun ⟨hi, hp⟩ =>
hi.casesOn (fun hip => hip) fun hin => False.elim (not_lt_of_lt hp (hin 0))⟩
#align hyperreal.infinite_pos_iff_infinite_and_pos Hyperreal.infinitePos_iff_infinite_and_pos
theorem infiniteNeg_iff_infinite_and_neg {x : ℝ*} : InfiniteNeg x ↔ Infinite x ∧ x < 0 :=
⟨fun hip => ⟨Or.inr hip, hip 0⟩, fun ⟨hi, hp⟩ =>
hi.casesOn (fun hin => False.elim (not_lt_of_lt hp (hin 0))) fun hip => hip⟩
#align hyperreal.infinite_neg_iff_infinite_and_neg Hyperreal.infiniteNeg_iff_infinite_and_neg
theorem infinitePos_iff_infinite_of_nonneg {x : ℝ*} (hp : 0 ≤ x) : InfinitePos x ↔ Infinite x :=
.symm <| or_iff_left fun h ↦ h.lt_zero.not_le hp
#align hyperreal.infinite_pos_iff_infinite_of_nonneg Hyperreal.infinitePos_iff_infinite_of_nonneg
theorem infinitePos_iff_infinite_of_pos {x : ℝ*} (hp : 0 < x) : InfinitePos x ↔ Infinite x :=
infinitePos_iff_infinite_of_nonneg hp.le
#align hyperreal.infinite_pos_iff_infinite_of_pos Hyperreal.infinitePos_iff_infinite_of_pos
theorem infiniteNeg_iff_infinite_of_neg {x : ℝ*} (hn : x < 0) : InfiniteNeg x ↔ Infinite x :=
.symm <| or_iff_right fun h ↦ h.pos.not_lt hn
#align hyperreal.infinite_neg_iff_infinite_of_neg Hyperreal.infiniteNeg_iff_infinite_of_neg
theorem infinitePos_abs_iff_infinite_abs {x : ℝ*} : InfinitePos |x| ↔ Infinite |x| :=
infinitePos_iff_infinite_of_nonneg (abs_nonneg _)
#align hyperreal.infinite_pos_abs_iff_infinite_abs Hyperreal.infinitePos_abs_iff_infinite_abs
-- Porting note: swapped LHS with RHS; added @[simp]
@[simp] theorem infinite_abs_iff {x : ℝ*} : Infinite |x| ↔ Infinite x := by
cases le_total 0 x <;> simp [*, abs_of_nonneg, abs_of_nonpos, infinite_neg]
#align hyperreal.infinite_iff_infinite_abs Hyperreal.infinite_abs_iffₓ
-- Porting note: swapped LHS with RHS;
-- Porting note (#11215): TODO: make it a `simp` lemma
@[simp] theorem infinitePos_abs_iff_infinite {x : ℝ*} : InfinitePos |x| ↔ Infinite x :=
infinitePos_abs_iff_infinite_abs.trans infinite_abs_iff
#align hyperreal.infinite_iff_infinite_pos_abs Hyperreal.infinitePos_abs_iff_infiniteₓ
theorem infinite_iff_abs_lt_abs {x : ℝ*} : Infinite x ↔ ∀ r : ℝ, (|r| : ℝ*) < |x| :=
infinitePos_abs_iff_infinite.symm.trans ⟨fun hI r => coe_abs r ▸ hI |r|, fun hR r =>
(le_abs_self _).trans_lt (hR r)⟩
#align hyperreal.infinite_iff_abs_lt_abs Hyperreal.infinite_iff_abs_lt_abs
theorem infinitePos_add_not_infiniteNeg {x y : ℝ*} :
InfinitePos x → ¬InfiniteNeg y → InfinitePos (x + y) := by
intro hip hnin r
cases' not_forall.mp hnin with r₂ hr₂
convert add_lt_add_of_lt_of_le (hip (r + -r₂)) (not_lt.mp hr₂) using 1
simp
#align hyperreal.infinite_pos_add_not_infinite_neg Hyperreal.infinitePos_add_not_infiniteNeg
theorem not_infiniteNeg_add_infinitePos {x y : ℝ*} :
¬InfiniteNeg x → InfinitePos y → InfinitePos (x + y) := fun hx hy =>
add_comm y x ▸ infinitePos_add_not_infiniteNeg hy hx
#align hyperreal.not_infinite_neg_add_infinite_pos Hyperreal.not_infiniteNeg_add_infinitePos
theorem infiniteNeg_add_not_infinitePos {x y : ℝ*} :
InfiniteNeg x → ¬InfinitePos y → InfiniteNeg (x + y) := by
rw [← infinitePos_neg, ← infinitePos_neg, ← @infiniteNeg_neg y, neg_add]
exact infinitePos_add_not_infiniteNeg
#align hyperreal.infinite_neg_add_not_infinite_pos Hyperreal.infiniteNeg_add_not_infinitePos
theorem not_infinitePos_add_infiniteNeg {x y : ℝ*} :
¬InfinitePos x → InfiniteNeg y → InfiniteNeg (x + y) := fun hx hy =>
add_comm y x ▸ infiniteNeg_add_not_infinitePos hy hx
#align hyperreal.not_infinite_pos_add_infinite_neg Hyperreal.not_infinitePos_add_infiniteNeg
theorem infinitePos_add_infinitePos {x y : ℝ*} :
InfinitePos x → InfinitePos y → InfinitePos (x + y) := fun hx hy =>
infinitePos_add_not_infiniteNeg hx hy.not_infiniteNeg
#align hyperreal.infinite_pos_add_infinite_pos Hyperreal.infinitePos_add_infinitePos
theorem infiniteNeg_add_infiniteNeg {x y : ℝ*} :
InfiniteNeg x → InfiniteNeg y → InfiniteNeg (x + y) := fun hx hy =>
infiniteNeg_add_not_infinitePos hx hy.not_infinitePos
#align hyperreal.infinite_neg_add_infinite_neg Hyperreal.infiniteNeg_add_infiniteNeg
theorem infinitePos_add_not_infinite {x y : ℝ*} :
InfinitePos x → ¬Infinite y → InfinitePos (x + y) := fun hx hy =>
infinitePos_add_not_infiniteNeg hx (not_or.mp hy).2
#align hyperreal.infinite_pos_add_not_infinite Hyperreal.infinitePos_add_not_infinite
theorem infiniteNeg_add_not_infinite {x y : ℝ*} :
InfiniteNeg x → ¬Infinite y → InfiniteNeg (x + y) := fun hx hy =>
infiniteNeg_add_not_infinitePos hx (not_or.mp hy).1
#align hyperreal.infinite_neg_add_not_infinite Hyperreal.infiniteNeg_add_not_infinite
theorem infinitePos_of_tendsto_top {f : ℕ → ℝ} (hf : Tendsto f atTop atTop) :
InfinitePos (ofSeq f) := fun r =>
have hf' := tendsto_atTop_atTop.mp hf
let ⟨i, hi⟩ := hf' (r + 1)
have hi' : ∀ a : ℕ, f a < r + 1 → a < i := fun a => lt_imp_lt_of_le_imp_le (hi a)
have hS : { a : ℕ | r < f a }ᶜ ⊆ { a : ℕ | a ≤ i } := by
simp only [Set.compl_setOf, not_lt]
exact fun a har => le_of_lt (hi' a (lt_of_le_of_lt har (lt_add_one _)))
Germ.coe_lt.2 <| mem_hyperfilter_of_finite_compl <| (Set.finite_le_nat _).subset hS
#align hyperreal.infinite_pos_of_tendsto_top Hyperreal.infinitePos_of_tendsto_top
theorem infiniteNeg_of_tendsto_bot {f : ℕ → ℝ} (hf : Tendsto f atTop atBot) :
InfiniteNeg (ofSeq f) := fun r =>
have hf' := tendsto_atTop_atBot.mp hf
let ⟨i, hi⟩ := hf' (r - 1)
have hi' : ∀ a : ℕ, r - 1 < f a → a < i := fun a => lt_imp_lt_of_le_imp_le (hi a)
have hS : { a : ℕ | f a < r }ᶜ ⊆ { a : ℕ | a ≤ i } := by
simp only [Set.compl_setOf, not_lt]
exact fun a har => le_of_lt (hi' a (lt_of_lt_of_le (sub_one_lt _) har))
Germ.coe_lt.2 <| mem_hyperfilter_of_finite_compl <| (Set.finite_le_nat _).subset hS
#align hyperreal.infinite_neg_of_tendsto_bot Hyperreal.infiniteNeg_of_tendsto_bot
theorem not_infinite_neg {x : ℝ*} : ¬Infinite x → ¬Infinite (-x) := mt infinite_neg.mp
#align hyperreal.not_infinite_neg Hyperreal.not_infinite_neg
theorem not_infinite_add {x y : ℝ*} (hx : ¬Infinite x) (hy : ¬Infinite y) : ¬Infinite (x + y) :=
have ⟨r, hr⟩ := exists_st_of_not_infinite hx
have ⟨s, hs⟩ := exists_st_of_not_infinite hy
not_infinite_of_exists_st <| ⟨r + s, hr.add hs⟩
#align hyperreal.not_infinite_add Hyperreal.not_infinite_add
theorem not_infinite_iff_exist_lt_gt {x : ℝ*} : ¬Infinite x ↔ ∃ r s : ℝ, (r : ℝ*) < x ∧ x < s :=
⟨fun hni ↦ let ⟨r, hr⟩ := exists_st_of_not_infinite hni; ⟨r - 1, r + 1, hr 1 one_pos⟩,
fun ⟨r, s, hr, hs⟩ hi ↦ hi.elim (fun hp ↦ (hp s).not_lt hs) (fun hn ↦ (hn r).not_lt hr)⟩
#align hyperreal.not_infinite_iff_exist_lt_gt Hyperreal.not_infinite_iff_exist_lt_gt
theorem not_infinite_real (r : ℝ) : ¬Infinite r := by
rw [not_infinite_iff_exist_lt_gt]
exact ⟨r - 1, r + 1, coe_lt_coe.2 <| sub_one_lt r, coe_lt_coe.2 <| lt_add_one r⟩
#align hyperreal.not_infinite_real Hyperreal.not_infinite_real
theorem Infinite.ne_real {x : ℝ*} : Infinite x → ∀ r : ℝ, x ≠ r := fun hi r hr =>
not_infinite_real r <| @Eq.subst _ Infinite _ _ hr hi
#align hyperreal.not_real_of_infinite Hyperreal.Infinite.ne_real
/-!
### Facts about `st` that require some infinite machinery
-/
theorem IsSt.mul {x y : ℝ*} {r s : ℝ} (hxr : IsSt x r) (hys : IsSt y s) : IsSt (x * y) (r * s) :=
hxr.map₂ hys continuous_mul.continuousAt
#align hyperreal.is_st_mul Hyperreal.IsSt.mul
--AN INFINITE LEMMA THAT REQUIRES SOME MORE ST MACHINERY
theorem not_infinite_mul {x y : ℝ*} (hx : ¬Infinite x) (hy : ¬Infinite y) : ¬Infinite (x * y) :=
have ⟨_r, hr⟩ := exists_st_of_not_infinite hx
have ⟨_s, hs⟩ := exists_st_of_not_infinite hy
(hr.mul hs).not_infinite
#align hyperreal.not_infinite_mul Hyperreal.not_infinite_mul
---
theorem st_add {x y : ℝ*} (hx : ¬Infinite x) (hy : ¬Infinite y) : st (x + y) = st x + st y :=
(isSt_st' (not_infinite_add hx hy)).unique ((isSt_st' hx).add (isSt_st' hy))
#align hyperreal.st_add Hyperreal.st_add
theorem st_neg (x : ℝ*) : st (-x) = -st x :=
if h : Infinite x then by
rw [h.st_eq, (infinite_neg.2 h).st_eq, neg_zero]
else (isSt_st' (not_infinite_neg h)).unique (isSt_st' h).neg
#align hyperreal.st_neg Hyperreal.st_neg
theorem st_mul {x y : ℝ*} (hx : ¬Infinite x) (hy : ¬Infinite y) : st (x * y) = st x * st y :=
have hx' := isSt_st' hx
have hy' := isSt_st' hy
have hxy := isSt_st' (not_infinite_mul hx hy)
hxy.unique (hx'.mul hy')
#align hyperreal.st_mul Hyperreal.st_mul
/-!
### Basic lemmas about infinitesimal
-/
theorem infinitesimal_def {x : ℝ*} : Infinitesimal x ↔ ∀ r : ℝ, 0 < r → -(r : ℝ*) < x ∧ x < r := by
simp [Infinitesimal, IsSt]
#align hyperreal.infinitesimal_def Hyperreal.infinitesimal_def
theorem lt_of_pos_of_infinitesimal {x : ℝ*} : Infinitesimal x → ∀ r : ℝ, 0 < r → x < r :=
fun hi r hr => ((infinitesimal_def.mp hi) r hr).2
#align hyperreal.lt_of_pos_of_infinitesimal Hyperreal.lt_of_pos_of_infinitesimal
theorem lt_neg_of_pos_of_infinitesimal {x : ℝ*} : Infinitesimal x → ∀ r : ℝ, 0 < r → -↑r < x :=
fun hi r hr => ((infinitesimal_def.mp hi) r hr).1
#align hyperreal.lt_neg_of_pos_of_infinitesimal Hyperreal.lt_neg_of_pos_of_infinitesimal
theorem gt_of_neg_of_infinitesimal {x : ℝ*} (hi : Infinitesimal x) (r : ℝ) (hr : r < 0) : ↑r < x :=
neg_neg r ▸ (infinitesimal_def.1 hi (-r) (neg_pos.2 hr)).1
#align hyperreal.gt_of_neg_of_infinitesimal Hyperreal.gt_of_neg_of_infinitesimal
theorem abs_lt_real_iff_infinitesimal {x : ℝ*} : Infinitesimal x ↔ ∀ r : ℝ, r ≠ 0 → |x| < |↑r| :=
⟨fun hi r hr ↦ abs_lt.mpr (coe_abs r ▸ infinitesimal_def.mp hi |r| (abs_pos.2 hr)), fun hR ↦
infinitesimal_def.mpr fun r hr => abs_lt.mp <| (abs_of_pos <| coe_pos.2 hr) ▸ hR r <| hr.ne'⟩
#align hyperreal.abs_lt_real_iff_infinitesimal Hyperreal.abs_lt_real_iff_infinitesimal
theorem infinitesimal_zero : Infinitesimal 0 := isSt_refl_real 0
#align hyperreal.infinitesimal_zero Hyperreal.infinitesimal_zero
theorem Infinitesimal.eq_zero {r : ℝ} : Infinitesimal r → r = 0 := eq_of_isSt_real
#align hyperreal.zero_of_infinitesimal_real Hyperreal.Infinitesimal.eq_zero
-- Porting note: swapped LHS with RHS; added `@[simp]`
@[simp] theorem infinitesimal_real_iff {r : ℝ} : Infinitesimal r ↔ r = 0 :=
isSt_real_iff_eq
#align hyperreal.zero_iff_infinitesimal_real Hyperreal.infinitesimal_real_iff
nonrec theorem Infinitesimal.add {x y : ℝ*} (hx : Infinitesimal x) (hy : Infinitesimal y) :
Infinitesimal (x + y) := by simpa only [add_zero] using hx.add hy
#align hyperreal.infinitesimal_add Hyperreal.Infinitesimal.add
nonrec theorem Infinitesimal.neg {x : ℝ*} (hx : Infinitesimal x) : Infinitesimal (-x) := by
simpa only [neg_zero] using hx.neg
#align hyperreal.infinitesimal_neg Hyperreal.Infinitesimal.neg
-- Porting note: swapped LHS and RHS, added `@[simp]`
@[simp] theorem infinitesimal_neg {x : ℝ*} : Infinitesimal (-x) ↔ Infinitesimal x :=
⟨fun h => neg_neg x ▸ h.neg, Infinitesimal.neg⟩
#align hyperreal.infinitesimal_neg_iff Hyperreal.infinitesimal_negₓ
nonrec theorem Infinitesimal.mul {x y : ℝ*} (hx : Infinitesimal x) (hy : Infinitesimal y) :
Infinitesimal (x * y) := by simpa only [mul_zero] using hx.mul hy
#align hyperreal.infinitesimal_mul Hyperreal.Infinitesimal.mul
theorem infinitesimal_of_tendsto_zero {f : ℕ → ℝ} (h : Tendsto f atTop (𝓝 0)) :
Infinitesimal (ofSeq f) :=
isSt_of_tendsto h
#align hyperreal.infinitesimal_of_tendsto_zero Hyperreal.infinitesimal_of_tendsto_zero
theorem infinitesimal_epsilon : Infinitesimal ε :=
infinitesimal_of_tendsto_zero tendsto_inverse_atTop_nhds_zero_nat
#align hyperreal.infinitesimal_epsilon Hyperreal.infinitesimal_epsilon
theorem not_real_of_infinitesimal_ne_zero (x : ℝ*) : Infinitesimal x → x ≠ 0 → ∀ r : ℝ, x ≠ r :=
fun hi hx r hr =>
hx <| hr.trans <| coe_eq_zero.2 <| IsSt.unique (hr.symm ▸ isSt_refl_real r : IsSt x r) hi
#align hyperreal.not_real_of_infinitesimal_ne_zero Hyperreal.not_real_of_infinitesimal_ne_zero
theorem IsSt.infinitesimal_sub {x : ℝ*} {r : ℝ} (hxr : IsSt x r) : Infinitesimal (x - ↑r) := by
simpa only [sub_self] using hxr.sub (isSt_refl_real r)
#align hyperreal.infinitesimal_sub_is_st Hyperreal.IsSt.infinitesimal_sub
theorem infinitesimal_sub_st {x : ℝ*} (hx : ¬Infinite x) : Infinitesimal (x - ↑(st x)) :=
(isSt_st' hx).infinitesimal_sub
#align hyperreal.infinitesimal_sub_st Hyperreal.infinitesimal_sub_st
theorem infinitePos_iff_infinitesimal_inv_pos {x : ℝ*} :
InfinitePos x ↔ Infinitesimal x⁻¹ ∧ 0 < x⁻¹ :=
⟨fun hip =>
⟨infinitesimal_def.mpr fun r hr =>
⟨lt_trans (coe_lt_coe.2 (neg_neg_of_pos hr)) (inv_pos.2 (hip 0)),
(inv_lt (coe_lt_coe.2 hr) (hip 0)).mp (by convert hip r⁻¹)⟩,
inv_pos.2 <| hip 0⟩,
fun ⟨hi, hp⟩ r =>
@_root_.by_cases (r = 0) (↑r < x) (fun h => Eq.substr h (inv_pos.mp hp)) fun h =>
lt_of_le_of_lt (coe_le_coe.2 (le_abs_self r))
((inv_lt_inv (inv_pos.mp hp) (coe_lt_coe.2 (abs_pos.2 h))).mp
((infinitesimal_def.mp hi) |r|⁻¹ (inv_pos.2 (abs_pos.2 h))).2)⟩
#align hyperreal.infinite_pos_iff_infinitesimal_inv_pos Hyperreal.infinitePos_iff_infinitesimal_inv_pos
theorem infiniteNeg_iff_infinitesimal_inv_neg {x : ℝ*} :
InfiniteNeg x ↔ Infinitesimal x⁻¹ ∧ x⁻¹ < 0 := by
rw [← infinitePos_neg, infinitePos_iff_infinitesimal_inv_pos, inv_neg, neg_pos, infinitesimal_neg]
#align hyperreal.infinite_neg_iff_infinitesimal_inv_neg Hyperreal.infiniteNeg_iff_infinitesimal_inv_neg
theorem infinitesimal_inv_of_infinite {x : ℝ*} : Infinite x → Infinitesimal x⁻¹ := fun hi =>
Or.casesOn hi (fun hip => (infinitePos_iff_infinitesimal_inv_pos.mp hip).1) fun hin =>
(infiniteNeg_iff_infinitesimal_inv_neg.mp hin).1
#align hyperreal.infinitesimal_inv_of_infinite Hyperreal.infinitesimal_inv_of_infinite
theorem infinite_of_infinitesimal_inv {x : ℝ*} (h0 : x ≠ 0) (hi : Infinitesimal x⁻¹) :
Infinite x := by
cases' lt_or_gt_of_ne h0 with hn hp
· exact Or.inr (infiniteNeg_iff_infinitesimal_inv_neg.mpr ⟨hi, inv_lt_zero.mpr hn⟩)
· exact Or.inl (infinitePos_iff_infinitesimal_inv_pos.mpr ⟨hi, inv_pos.mpr hp⟩)
#align hyperreal.infinite_of_infinitesimal_inv Hyperreal.infinite_of_infinitesimal_inv
theorem infinite_iff_infinitesimal_inv {x : ℝ*} (h0 : x ≠ 0) : Infinite x ↔ Infinitesimal x⁻¹ :=
⟨infinitesimal_inv_of_infinite, infinite_of_infinitesimal_inv h0⟩
#align hyperreal.infinite_iff_infinitesimal_inv Hyperreal.infinite_iff_infinitesimal_inv
theorem infinitesimal_pos_iff_infinitePos_inv {x : ℝ*} :
InfinitePos x⁻¹ ↔ Infinitesimal x ∧ 0 < x :=
infinitePos_iff_infinitesimal_inv_pos.trans <| by rw [inv_inv]
#align hyperreal.infinitesimal_pos_iff_infinite_pos_inv Hyperreal.infinitesimal_pos_iff_infinitePos_inv
theorem infinitesimal_neg_iff_infiniteNeg_inv {x : ℝ*} :
InfiniteNeg x⁻¹ ↔ Infinitesimal x ∧ x < 0 :=
infiniteNeg_iff_infinitesimal_inv_neg.trans <| by rw [inv_inv]
#align hyperreal.infinitesimal_neg_iff_infinite_neg_inv Hyperreal.infinitesimal_neg_iff_infiniteNeg_inv
theorem infinitesimal_iff_infinite_inv {x : ℝ*} (h : x ≠ 0) : Infinitesimal x ↔ Infinite x⁻¹ :=
Iff.trans (by rw [inv_inv]) (infinite_iff_infinitesimal_inv (inv_ne_zero h)).symm
#align hyperreal.infinitesimal_iff_infinite_inv Hyperreal.infinitesimal_iff_infinite_inv
/-!
### `Hyperreal.st` stuff that requires infinitesimal machinery
-/
theorem IsSt.inv {x : ℝ*} {r : ℝ} (hi : ¬Infinitesimal x) (hr : IsSt x r) : IsSt x⁻¹ r⁻¹ :=
hr.map <| continuousAt_inv₀ <| by rintro rfl; exact hi hr
#align hyperreal.is_st_inv Hyperreal.IsSt.inv
theorem st_inv (x : ℝ*) : st x⁻¹ = (st x)⁻¹ := by
by_cases h0 : x = 0
· rw [h0, inv_zero, ← coe_zero, st_id_real, inv_zero]
by_cases h1 : Infinitesimal x
· rw [((infinitesimal_iff_infinite_inv h0).mp h1).st_eq, h1.st_eq, inv_zero]
by_cases h2 : Infinite x
· rw [(infinitesimal_inv_of_infinite h2).st_eq, h2.st_eq, inv_zero]
exact ((isSt_st' h2).inv h1).st_eq
#align hyperreal.st_inv Hyperreal.st_inv
/-!
### Infinite stuff that requires infinitesimal machinery
-/
theorem infinitePos_omega : InfinitePos ω :=
infinitePos_iff_infinitesimal_inv_pos.mpr ⟨infinitesimal_epsilon, epsilon_pos⟩
#align hyperreal.infinite_pos_omega Hyperreal.infinitePos_omega
theorem infinite_omega : Infinite ω :=
(infinite_iff_infinitesimal_inv omega_ne_zero).mpr infinitesimal_epsilon
#align hyperreal.infinite_omega Hyperreal.infinite_omega
theorem infinitePos_mul_of_infinitePos_not_infinitesimal_pos {x y : ℝ*} :
InfinitePos x → ¬Infinitesimal y → 0 < y → InfinitePos (x * y) := fun hx hy₁ hy₂ r => by
have hy₁' := not_forall.mp (mt infinitesimal_def.2 hy₁)
let ⟨r₁, hy₁''⟩ := hy₁'
have hyr : 0 < r₁ ∧ ↑r₁ ≤ y := by
rwa [Classical.not_imp, ← abs_lt, not_lt, abs_of_pos hy₂] at hy₁''
rw [← div_mul_cancel₀ r (ne_of_gt hyr.1), coe_mul]
exact mul_lt_mul (hx (r / r₁)) hyr.2 (coe_lt_coe.2 hyr.1) (le_of_lt (hx 0))
#align hyperreal.infinite_pos_mul_of_infinite_pos_not_infinitesimal_pos Hyperreal.infinitePos_mul_of_infinitePos_not_infinitesimal_pos
theorem infinitePos_mul_of_not_infinitesimal_pos_infinitePos {x y : ℝ*} :
¬Infinitesimal x → 0 < x → InfinitePos y → InfinitePos (x * y) := fun hx hp hy =>
mul_comm y x ▸ infinitePos_mul_of_infinitePos_not_infinitesimal_pos hy hx hp
#align hyperreal.infinite_pos_mul_of_not_infinitesimal_pos_infinite_pos Hyperreal.infinitePos_mul_of_not_infinitesimal_pos_infinitePos
| Mathlib/Data/Real/Hyperreal.lean | 831 | 834 | theorem infinitePos_mul_of_infiniteNeg_not_infinitesimal_neg {x y : ℝ*} :
InfiniteNeg x → ¬Infinitesimal y → y < 0 → InfinitePos (x * y) := by |
rw [← infinitePos_neg, ← neg_pos, ← neg_mul_neg, ← infinitesimal_neg]
exact infinitePos_mul_of_infinitePos_not_infinitesimal_pos
|
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Jeremy Avigad, Yury Kudryashov, Patrick Massot
-/
import Mathlib.Algebra.BigOperators.Group.Finset
import Mathlib.Algebra.Order.Field.Defs
import Mathlib.Algebra.Order.Group.Instances
import Mathlib.Algebra.Order.Group.MinMax
import Mathlib.Algebra.Order.Ring.Basic
import Mathlib.Data.Finset.Preimage
import Mathlib.Order.Interval.Set.Disjoint
import Mathlib.Order.Interval.Set.OrderIso
import Mathlib.Order.ConditionallyCompleteLattice.Basic
import Mathlib.Order.Filter.Bases
#align_import order.filter.at_top_bot from "leanprover-community/mathlib"@"1f0096e6caa61e9c849ec2adbd227e960e9dff58"
/-!
# `Filter.atTop` and `Filter.atBot` filters on preorders, monoids and groups.
In this file we define the filters
* `Filter.atTop`: corresponds to `n → +∞`;
* `Filter.atBot`: corresponds to `n → -∞`.
Then we prove many lemmas like “if `f → +∞`, then `f ± c → +∞`”.
-/
set_option autoImplicit true
variable {ι ι' α β γ : Type*}
open Set
namespace Filter
/-- `atTop` is the filter representing the limit `→ ∞` on an ordered set.
It is generated by the collection of up-sets `{b | a ≤ b}`.
(The preorder need not have a top element for this to be well defined,
and indeed is trivial when a top element exists.) -/
def atTop [Preorder α] : Filter α :=
⨅ a, 𝓟 (Ici a)
#align filter.at_top Filter.atTop
/-- `atBot` is the filter representing the limit `→ -∞` on an ordered set.
It is generated by the collection of down-sets `{b | b ≤ a}`.
(The preorder need not have a bottom element for this to be well defined,
and indeed is trivial when a bottom element exists.) -/
def atBot [Preorder α] : Filter α :=
⨅ a, 𝓟 (Iic a)
#align filter.at_bot Filter.atBot
theorem mem_atTop [Preorder α] (a : α) : { b : α | a ≤ b } ∈ @atTop α _ :=
mem_iInf_of_mem a <| Subset.refl _
#align filter.mem_at_top Filter.mem_atTop
theorem Ici_mem_atTop [Preorder α] (a : α) : Ici a ∈ (atTop : Filter α) :=
mem_atTop a
#align filter.Ici_mem_at_top Filter.Ici_mem_atTop
theorem Ioi_mem_atTop [Preorder α] [NoMaxOrder α] (x : α) : Ioi x ∈ (atTop : Filter α) :=
let ⟨z, hz⟩ := exists_gt x
mem_of_superset (mem_atTop z) fun _ h => lt_of_lt_of_le hz h
#align filter.Ioi_mem_at_top Filter.Ioi_mem_atTop
theorem mem_atBot [Preorder α] (a : α) : { b : α | b ≤ a } ∈ @atBot α _ :=
mem_iInf_of_mem a <| Subset.refl _
#align filter.mem_at_bot Filter.mem_atBot
theorem Iic_mem_atBot [Preorder α] (a : α) : Iic a ∈ (atBot : Filter α) :=
mem_atBot a
#align filter.Iic_mem_at_bot Filter.Iic_mem_atBot
theorem Iio_mem_atBot [Preorder α] [NoMinOrder α] (x : α) : Iio x ∈ (atBot : Filter α) :=
let ⟨z, hz⟩ := exists_lt x
mem_of_superset (mem_atBot z) fun _ h => lt_of_le_of_lt h hz
#align filter.Iio_mem_at_bot Filter.Iio_mem_atBot
theorem disjoint_atBot_principal_Ioi [Preorder α] (x : α) : Disjoint atBot (𝓟 (Ioi x)) :=
disjoint_of_disjoint_of_mem (Iic_disjoint_Ioi le_rfl) (Iic_mem_atBot x) (mem_principal_self _)
#align filter.disjoint_at_bot_principal_Ioi Filter.disjoint_atBot_principal_Ioi
theorem disjoint_atTop_principal_Iio [Preorder α] (x : α) : Disjoint atTop (𝓟 (Iio x)) :=
@disjoint_atBot_principal_Ioi αᵒᵈ _ _
#align filter.disjoint_at_top_principal_Iio Filter.disjoint_atTop_principal_Iio
theorem disjoint_atTop_principal_Iic [Preorder α] [NoMaxOrder α] (x : α) :
Disjoint atTop (𝓟 (Iic x)) :=
disjoint_of_disjoint_of_mem (Iic_disjoint_Ioi le_rfl).symm (Ioi_mem_atTop x)
(mem_principal_self _)
#align filter.disjoint_at_top_principal_Iic Filter.disjoint_atTop_principal_Iic
theorem disjoint_atBot_principal_Ici [Preorder α] [NoMinOrder α] (x : α) :
Disjoint atBot (𝓟 (Ici x)) :=
@disjoint_atTop_principal_Iic αᵒᵈ _ _ _
#align filter.disjoint_at_bot_principal_Ici Filter.disjoint_atBot_principal_Ici
theorem disjoint_pure_atTop [Preorder α] [NoMaxOrder α] (x : α) : Disjoint (pure x) atTop :=
Disjoint.symm <| (disjoint_atTop_principal_Iic x).mono_right <| le_principal_iff.2 <|
mem_pure.2 right_mem_Iic
#align filter.disjoint_pure_at_top Filter.disjoint_pure_atTop
theorem disjoint_pure_atBot [Preorder α] [NoMinOrder α] (x : α) : Disjoint (pure x) atBot :=
@disjoint_pure_atTop αᵒᵈ _ _ _
#align filter.disjoint_pure_at_bot Filter.disjoint_pure_atBot
theorem not_tendsto_const_atTop [Preorder α] [NoMaxOrder α] (x : α) (l : Filter β) [l.NeBot] :
¬Tendsto (fun _ => x) l atTop :=
tendsto_const_pure.not_tendsto (disjoint_pure_atTop x)
#align filter.not_tendsto_const_at_top Filter.not_tendsto_const_atTop
theorem not_tendsto_const_atBot [Preorder α] [NoMinOrder α] (x : α) (l : Filter β) [l.NeBot] :
¬Tendsto (fun _ => x) l atBot :=
tendsto_const_pure.not_tendsto (disjoint_pure_atBot x)
#align filter.not_tendsto_const_at_bot Filter.not_tendsto_const_atBot
theorem disjoint_atBot_atTop [PartialOrder α] [Nontrivial α] :
Disjoint (atBot : Filter α) atTop := by
rcases exists_pair_ne α with ⟨x, y, hne⟩
by_cases hle : x ≤ y
· refine disjoint_of_disjoint_of_mem ?_ (Iic_mem_atBot x) (Ici_mem_atTop y)
exact Iic_disjoint_Ici.2 (hle.lt_of_ne hne).not_le
· refine disjoint_of_disjoint_of_mem ?_ (Iic_mem_atBot y) (Ici_mem_atTop x)
exact Iic_disjoint_Ici.2 hle
#align filter.disjoint_at_bot_at_top Filter.disjoint_atBot_atTop
theorem disjoint_atTop_atBot [PartialOrder α] [Nontrivial α] : Disjoint (atTop : Filter α) atBot :=
disjoint_atBot_atTop.symm
#align filter.disjoint_at_top_at_bot Filter.disjoint_atTop_atBot
theorem hasAntitoneBasis_atTop [Nonempty α] [Preorder α] [IsDirected α (· ≤ ·)] :
(@atTop α _).HasAntitoneBasis Ici :=
.iInf_principal fun _ _ ↦ Ici_subset_Ici.2
theorem atTop_basis [Nonempty α] [SemilatticeSup α] : (@atTop α _).HasBasis (fun _ => True) Ici :=
hasAntitoneBasis_atTop.1
#align filter.at_top_basis Filter.atTop_basis
theorem atTop_eq_generate_Ici [SemilatticeSup α] : atTop = generate (range (Ici (α := α))) := by
rcases isEmpty_or_nonempty α with hα|hα
· simp only [eq_iff_true_of_subsingleton]
· simp [(atTop_basis (α := α)).eq_generate, range]
theorem atTop_basis' [SemilatticeSup α] (a : α) : (@atTop α _).HasBasis (fun x => a ≤ x) Ici :=
⟨fun _ =>
(@atTop_basis α ⟨a⟩ _).mem_iff.trans
⟨fun ⟨x, _, hx⟩ => ⟨x ⊔ a, le_sup_right, fun _y hy => hx (le_trans le_sup_left hy)⟩,
fun ⟨x, _, hx⟩ => ⟨x, trivial, hx⟩⟩⟩
#align filter.at_top_basis' Filter.atTop_basis'
theorem atBot_basis [Nonempty α] [SemilatticeInf α] : (@atBot α _).HasBasis (fun _ => True) Iic :=
@atTop_basis αᵒᵈ _ _
#align filter.at_bot_basis Filter.atBot_basis
theorem atBot_basis' [SemilatticeInf α] (a : α) : (@atBot α _).HasBasis (fun x => x ≤ a) Iic :=
@atTop_basis' αᵒᵈ _ _
#align filter.at_bot_basis' Filter.atBot_basis'
@[instance]
theorem atTop_neBot [Nonempty α] [SemilatticeSup α] : NeBot (atTop : Filter α) :=
atTop_basis.neBot_iff.2 fun _ => nonempty_Ici
#align filter.at_top_ne_bot Filter.atTop_neBot
@[instance]
theorem atBot_neBot [Nonempty α] [SemilatticeInf α] : NeBot (atBot : Filter α) :=
@atTop_neBot αᵒᵈ _ _
#align filter.at_bot_ne_bot Filter.atBot_neBot
@[simp]
theorem mem_atTop_sets [Nonempty α] [SemilatticeSup α] {s : Set α} :
s ∈ (atTop : Filter α) ↔ ∃ a : α, ∀ b ≥ a, b ∈ s :=
atTop_basis.mem_iff.trans <| exists_congr fun _ => true_and_iff _
#align filter.mem_at_top_sets Filter.mem_atTop_sets
@[simp]
theorem mem_atBot_sets [Nonempty α] [SemilatticeInf α] {s : Set α} :
s ∈ (atBot : Filter α) ↔ ∃ a : α, ∀ b ≤ a, b ∈ s :=
@mem_atTop_sets αᵒᵈ _ _ _
#align filter.mem_at_bot_sets Filter.mem_atBot_sets
@[simp]
theorem eventually_atTop [SemilatticeSup α] [Nonempty α] {p : α → Prop} :
(∀ᶠ x in atTop, p x) ↔ ∃ a, ∀ b ≥ a, p b :=
mem_atTop_sets
#align filter.eventually_at_top Filter.eventually_atTop
@[simp]
theorem eventually_atBot [SemilatticeInf α] [Nonempty α] {p : α → Prop} :
(∀ᶠ x in atBot, p x) ↔ ∃ a, ∀ b ≤ a, p b :=
mem_atBot_sets
#align filter.eventually_at_bot Filter.eventually_atBot
theorem eventually_ge_atTop [Preorder α] (a : α) : ∀ᶠ x in atTop, a ≤ x :=
mem_atTop a
#align filter.eventually_ge_at_top Filter.eventually_ge_atTop
theorem eventually_le_atBot [Preorder α] (a : α) : ∀ᶠ x in atBot, x ≤ a :=
mem_atBot a
#align filter.eventually_le_at_bot Filter.eventually_le_atBot
theorem eventually_gt_atTop [Preorder α] [NoMaxOrder α] (a : α) : ∀ᶠ x in atTop, a < x :=
Ioi_mem_atTop a
#align filter.eventually_gt_at_top Filter.eventually_gt_atTop
theorem eventually_ne_atTop [Preorder α] [NoMaxOrder α] (a : α) : ∀ᶠ x in atTop, x ≠ a :=
(eventually_gt_atTop a).mono fun _ => ne_of_gt
#align filter.eventually_ne_at_top Filter.eventually_ne_atTop
protected theorem Tendsto.eventually_gt_atTop [Preorder β] [NoMaxOrder β] {f : α → β} {l : Filter α}
(hf : Tendsto f l atTop) (c : β) : ∀ᶠ x in l, c < f x :=
hf.eventually (eventually_gt_atTop c)
#align filter.tendsto.eventually_gt_at_top Filter.Tendsto.eventually_gt_atTop
protected theorem Tendsto.eventually_ge_atTop [Preorder β] {f : α → β} {l : Filter α}
(hf : Tendsto f l atTop) (c : β) : ∀ᶠ x in l, c ≤ f x :=
hf.eventually (eventually_ge_atTop c)
#align filter.tendsto.eventually_ge_at_top Filter.Tendsto.eventually_ge_atTop
protected theorem Tendsto.eventually_ne_atTop [Preorder β] [NoMaxOrder β] {f : α → β} {l : Filter α}
(hf : Tendsto f l atTop) (c : β) : ∀ᶠ x in l, f x ≠ c :=
hf.eventually (eventually_ne_atTop c)
#align filter.tendsto.eventually_ne_at_top Filter.Tendsto.eventually_ne_atTop
protected theorem Tendsto.eventually_ne_atTop' [Preorder β] [NoMaxOrder β] {f : α → β}
{l : Filter α} (hf : Tendsto f l atTop) (c : α) : ∀ᶠ x in l, x ≠ c :=
(hf.eventually_ne_atTop (f c)).mono fun _ => ne_of_apply_ne f
#align filter.tendsto.eventually_ne_at_top' Filter.Tendsto.eventually_ne_atTop'
theorem eventually_lt_atBot [Preorder α] [NoMinOrder α] (a : α) : ∀ᶠ x in atBot, x < a :=
Iio_mem_atBot a
#align filter.eventually_lt_at_bot Filter.eventually_lt_atBot
theorem eventually_ne_atBot [Preorder α] [NoMinOrder α] (a : α) : ∀ᶠ x in atBot, x ≠ a :=
(eventually_lt_atBot a).mono fun _ => ne_of_lt
#align filter.eventually_ne_at_bot Filter.eventually_ne_atBot
protected theorem Tendsto.eventually_lt_atBot [Preorder β] [NoMinOrder β] {f : α → β} {l : Filter α}
(hf : Tendsto f l atBot) (c : β) : ∀ᶠ x in l, f x < c :=
hf.eventually (eventually_lt_atBot c)
#align filter.tendsto.eventually_lt_at_bot Filter.Tendsto.eventually_lt_atBot
protected theorem Tendsto.eventually_le_atBot [Preorder β] {f : α → β} {l : Filter α}
(hf : Tendsto f l atBot) (c : β) : ∀ᶠ x in l, f x ≤ c :=
hf.eventually (eventually_le_atBot c)
#align filter.tendsto.eventually_le_at_bot Filter.Tendsto.eventually_le_atBot
protected theorem Tendsto.eventually_ne_atBot [Preorder β] [NoMinOrder β] {f : α → β} {l : Filter α}
(hf : Tendsto f l atBot) (c : β) : ∀ᶠ x in l, f x ≠ c :=
hf.eventually (eventually_ne_atBot c)
#align filter.tendsto.eventually_ne_at_bot Filter.Tendsto.eventually_ne_atBot
theorem eventually_forall_ge_atTop [Preorder α] {p : α → Prop} :
(∀ᶠ x in atTop, ∀ y, x ≤ y → p y) ↔ ∀ᶠ x in atTop, p x := by
refine ⟨fun h ↦ h.mono fun x hx ↦ hx x le_rfl, fun h ↦ ?_⟩
rcases (hasBasis_iInf_principal_finite _).eventually_iff.1 h with ⟨S, hSf, hS⟩
refine mem_iInf_of_iInter hSf (V := fun x ↦ Ici x.1) (fun _ ↦ Subset.rfl) fun x hx y hy ↦ ?_
simp only [mem_iInter] at hS hx
exact hS fun z hz ↦ le_trans (hx ⟨z, hz⟩) hy
theorem eventually_forall_le_atBot [Preorder α] {p : α → Prop} :
(∀ᶠ x in atBot, ∀ y, y ≤ x → p y) ↔ ∀ᶠ x in atBot, p x :=
eventually_forall_ge_atTop (α := αᵒᵈ)
theorem Tendsto.eventually_forall_ge_atTop {α β : Type*} [Preorder β] {l : Filter α}
{p : β → Prop} {f : α → β} (hf : Tendsto f l atTop) (h_evtl : ∀ᶠ x in atTop, p x) :
∀ᶠ x in l, ∀ y, f x ≤ y → p y := by
rw [← Filter.eventually_forall_ge_atTop] at h_evtl; exact (h_evtl.comap f).filter_mono hf.le_comap
theorem Tendsto.eventually_forall_le_atBot {α β : Type*} [Preorder β] {l : Filter α}
{p : β → Prop} {f : α → β} (hf : Tendsto f l atBot) (h_evtl : ∀ᶠ x in atBot, p x) :
∀ᶠ x in l, ∀ y, y ≤ f x → p y := by
rw [← Filter.eventually_forall_le_atBot] at h_evtl; exact (h_evtl.comap f).filter_mono hf.le_comap
theorem atTop_basis_Ioi [Nonempty α] [SemilatticeSup α] [NoMaxOrder α] :
(@atTop α _).HasBasis (fun _ => True) Ioi :=
atTop_basis.to_hasBasis (fun a ha => ⟨a, ha, Ioi_subset_Ici_self⟩) fun a ha =>
(exists_gt a).imp fun _b hb => ⟨ha, Ici_subset_Ioi.2 hb⟩
#align filter.at_top_basis_Ioi Filter.atTop_basis_Ioi
lemma atTop_basis_Ioi' [SemilatticeSup α] [NoMaxOrder α] (a : α) : atTop.HasBasis (a < ·) Ioi :=
have : Nonempty α := ⟨a⟩
atTop_basis_Ioi.to_hasBasis (fun b _ ↦
let ⟨c, hc⟩ := exists_gt (a ⊔ b)
⟨c, le_sup_left.trans_lt hc, Ioi_subset_Ioi <| le_sup_right.trans hc.le⟩) fun b _ ↦
⟨b, trivial, Subset.rfl⟩
theorem atTop_countable_basis [Nonempty α] [SemilatticeSup α] [Countable α] :
HasCountableBasis (atTop : Filter α) (fun _ => True) Ici :=
{ atTop_basis with countable := to_countable _ }
#align filter.at_top_countable_basis Filter.atTop_countable_basis
theorem atBot_countable_basis [Nonempty α] [SemilatticeInf α] [Countable α] :
HasCountableBasis (atBot : Filter α) (fun _ => True) Iic :=
{ atBot_basis with countable := to_countable _ }
#align filter.at_bot_countable_basis Filter.atBot_countable_basis
instance (priority := 200) atTop.isCountablyGenerated [Preorder α] [Countable α] :
(atTop : Filter <| α).IsCountablyGenerated :=
isCountablyGenerated_seq _
#align filter.at_top.is_countably_generated Filter.atTop.isCountablyGenerated
instance (priority := 200) atBot.isCountablyGenerated [Preorder α] [Countable α] :
(atBot : Filter <| α).IsCountablyGenerated :=
isCountablyGenerated_seq _
#align filter.at_bot.is_countably_generated Filter.atBot.isCountablyGenerated
theorem _root_.IsTop.atTop_eq [Preorder α] {a : α} (ha : IsTop a) : atTop = 𝓟 (Ici a) :=
(iInf_le _ _).antisymm <| le_iInf fun b ↦ principal_mono.2 <| Ici_subset_Ici.2 <| ha b
theorem _root_.IsBot.atBot_eq [Preorder α] {a : α} (ha : IsBot a) : atBot = 𝓟 (Iic a) :=
ha.toDual.atTop_eq
theorem OrderTop.atTop_eq (α) [PartialOrder α] [OrderTop α] : (atTop : Filter α) = pure ⊤ := by
rw [isTop_top.atTop_eq, Ici_top, principal_singleton]
#align filter.order_top.at_top_eq Filter.OrderTop.atTop_eq
theorem OrderBot.atBot_eq (α) [PartialOrder α] [OrderBot α] : (atBot : Filter α) = pure ⊥ :=
@OrderTop.atTop_eq αᵒᵈ _ _
#align filter.order_bot.at_bot_eq Filter.OrderBot.atBot_eq
@[nontriviality]
theorem Subsingleton.atTop_eq (α) [Subsingleton α] [Preorder α] : (atTop : Filter α) = ⊤ := by
refine top_unique fun s hs x => ?_
rw [atTop, ciInf_subsingleton x, mem_principal] at hs
exact hs left_mem_Ici
#align filter.subsingleton.at_top_eq Filter.Subsingleton.atTop_eq
@[nontriviality]
theorem Subsingleton.atBot_eq (α) [Subsingleton α] [Preorder α] : (atBot : Filter α) = ⊤ :=
@Subsingleton.atTop_eq αᵒᵈ _ _
#align filter.subsingleton.at_bot_eq Filter.Subsingleton.atBot_eq
theorem tendsto_atTop_pure [PartialOrder α] [OrderTop α] (f : α → β) :
Tendsto f atTop (pure <| f ⊤) :=
(OrderTop.atTop_eq α).symm ▸ tendsto_pure_pure _ _
#align filter.tendsto_at_top_pure Filter.tendsto_atTop_pure
theorem tendsto_atBot_pure [PartialOrder α] [OrderBot α] (f : α → β) :
Tendsto f atBot (pure <| f ⊥) :=
@tendsto_atTop_pure αᵒᵈ _ _ _ _
#align filter.tendsto_at_bot_pure Filter.tendsto_atBot_pure
theorem Eventually.exists_forall_of_atTop [SemilatticeSup α] [Nonempty α] {p : α → Prop}
(h : ∀ᶠ x in atTop, p x) : ∃ a, ∀ b ≥ a, p b :=
eventually_atTop.mp h
#align filter.eventually.exists_forall_of_at_top Filter.Eventually.exists_forall_of_atTop
theorem Eventually.exists_forall_of_atBot [SemilatticeInf α] [Nonempty α] {p : α → Prop}
(h : ∀ᶠ x in atBot, p x) : ∃ a, ∀ b ≤ a, p b :=
eventually_atBot.mp h
#align filter.eventually.exists_forall_of_at_bot Filter.Eventually.exists_forall_of_atBot
lemma exists_eventually_atTop [SemilatticeSup α] [Nonempty α] {r : α → β → Prop} :
(∃ b, ∀ᶠ a in atTop, r a b) ↔ ∀ᶠ a₀ in atTop, ∃ b, ∀ a ≥ a₀, r a b := by
simp_rw [eventually_atTop, ← exists_swap (α := α)]
exact exists_congr fun a ↦ .symm <| forall_ge_iff <| Monotone.exists fun _ _ _ hb H n hn ↦
H n (hb.trans hn)
lemma exists_eventually_atBot [SemilatticeInf α] [Nonempty α] {r : α → β → Prop} :
(∃ b, ∀ᶠ a in atBot, r a b) ↔ ∀ᶠ a₀ in atBot, ∃ b, ∀ a ≤ a₀, r a b := by
simp_rw [eventually_atBot, ← exists_swap (α := α)]
exact exists_congr fun a ↦ .symm <| forall_le_iff <| Antitone.exists fun _ _ _ hb H n hn ↦
H n (hn.trans hb)
theorem frequently_atTop [SemilatticeSup α] [Nonempty α] {p : α → Prop} :
(∃ᶠ x in atTop, p x) ↔ ∀ a, ∃ b ≥ a, p b :=
atTop_basis.frequently_iff.trans <| by simp
#align filter.frequently_at_top Filter.frequently_atTop
theorem frequently_atBot [SemilatticeInf α] [Nonempty α] {p : α → Prop} :
(∃ᶠ x in atBot, p x) ↔ ∀ a, ∃ b ≤ a, p b :=
@frequently_atTop αᵒᵈ _ _ _
#align filter.frequently_at_bot Filter.frequently_atBot
theorem frequently_atTop' [SemilatticeSup α] [Nonempty α] [NoMaxOrder α] {p : α → Prop} :
(∃ᶠ x in atTop, p x) ↔ ∀ a, ∃ b > a, p b :=
atTop_basis_Ioi.frequently_iff.trans <| by simp
#align filter.frequently_at_top' Filter.frequently_atTop'
theorem frequently_atBot' [SemilatticeInf α] [Nonempty α] [NoMinOrder α] {p : α → Prop} :
(∃ᶠ x in atBot, p x) ↔ ∀ a, ∃ b < a, p b :=
@frequently_atTop' αᵒᵈ _ _ _ _
#align filter.frequently_at_bot' Filter.frequently_atBot'
theorem Frequently.forall_exists_of_atTop [SemilatticeSup α] [Nonempty α] {p : α → Prop}
(h : ∃ᶠ x in atTop, p x) : ∀ a, ∃ b ≥ a, p b :=
frequently_atTop.mp h
#align filter.frequently.forall_exists_of_at_top Filter.Frequently.forall_exists_of_atTop
theorem Frequently.forall_exists_of_atBot [SemilatticeInf α] [Nonempty α] {p : α → Prop}
(h : ∃ᶠ x in atBot, p x) : ∀ a, ∃ b ≤ a, p b :=
frequently_atBot.mp h
#align filter.frequently.forall_exists_of_at_bot Filter.Frequently.forall_exists_of_atBot
theorem map_atTop_eq [Nonempty α] [SemilatticeSup α] {f : α → β} :
atTop.map f = ⨅ a, 𝓟 (f '' { a' | a ≤ a' }) :=
(atTop_basis.map f).eq_iInf
#align filter.map_at_top_eq Filter.map_atTop_eq
theorem map_atBot_eq [Nonempty α] [SemilatticeInf α] {f : α → β} :
atBot.map f = ⨅ a, 𝓟 (f '' { a' | a' ≤ a }) :=
@map_atTop_eq αᵒᵈ _ _ _ _
#align filter.map_at_bot_eq Filter.map_atBot_eq
theorem tendsto_atTop [Preorder β] {m : α → β} {f : Filter α} :
Tendsto m f atTop ↔ ∀ b, ∀ᶠ a in f, b ≤ m a := by
simp only [atTop, tendsto_iInf, tendsto_principal, mem_Ici]
#align filter.tendsto_at_top Filter.tendsto_atTop
theorem tendsto_atBot [Preorder β] {m : α → β} {f : Filter α} :
Tendsto m f atBot ↔ ∀ b, ∀ᶠ a in f, m a ≤ b :=
@tendsto_atTop α βᵒᵈ _ m f
#align filter.tendsto_at_bot Filter.tendsto_atBot
theorem tendsto_atTop_mono' [Preorder β] (l : Filter α) ⦃f₁ f₂ : α → β⦄ (h : f₁ ≤ᶠ[l] f₂)
(h₁ : Tendsto f₁ l atTop) : Tendsto f₂ l atTop :=
tendsto_atTop.2 fun b => by filter_upwards [tendsto_atTop.1 h₁ b, h] with x using le_trans
#align filter.tendsto_at_top_mono' Filter.tendsto_atTop_mono'
theorem tendsto_atBot_mono' [Preorder β] (l : Filter α) ⦃f₁ f₂ : α → β⦄ (h : f₁ ≤ᶠ[l] f₂) :
Tendsto f₂ l atBot → Tendsto f₁ l atBot :=
@tendsto_atTop_mono' _ βᵒᵈ _ _ _ _ h
#align filter.tendsto_at_bot_mono' Filter.tendsto_atBot_mono'
theorem tendsto_atTop_mono [Preorder β] {l : Filter α} {f g : α → β} (h : ∀ n, f n ≤ g n) :
Tendsto f l atTop → Tendsto g l atTop :=
tendsto_atTop_mono' l <| eventually_of_forall h
#align filter.tendsto_at_top_mono Filter.tendsto_atTop_mono
theorem tendsto_atBot_mono [Preorder β] {l : Filter α} {f g : α → β} (h : ∀ n, f n ≤ g n) :
Tendsto g l atBot → Tendsto f l atBot :=
@tendsto_atTop_mono _ βᵒᵈ _ _ _ _ h
#align filter.tendsto_at_bot_mono Filter.tendsto_atBot_mono
lemma atTop_eq_generate_of_forall_exists_le [LinearOrder α] {s : Set α} (hs : ∀ x, ∃ y ∈ s, x ≤ y) :
(atTop : Filter α) = generate (Ici '' s) := by
rw [atTop_eq_generate_Ici]
apply le_antisymm
· rw [le_generate_iff]
rintro - ⟨y, -, rfl⟩
exact mem_generate_of_mem ⟨y, rfl⟩
· rw [le_generate_iff]
rintro - ⟨x, -, -, rfl⟩
rcases hs x with ⟨y, ys, hy⟩
have A : Ici y ∈ generate (Ici '' s) := mem_generate_of_mem (mem_image_of_mem _ ys)
have B : Ici y ⊆ Ici x := Ici_subset_Ici.2 hy
exact sets_of_superset (generate (Ici '' s)) A B
lemma atTop_eq_generate_of_not_bddAbove [LinearOrder α] {s : Set α} (hs : ¬ BddAbove s) :
(atTop : Filter α) = generate (Ici '' s) := by
refine atTop_eq_generate_of_forall_exists_le fun x ↦ ?_
obtain ⟨y, hy, hy'⟩ := not_bddAbove_iff.mp hs x
exact ⟨y, hy, hy'.le⟩
end Filter
namespace OrderIso
open Filter
variable [Preorder α] [Preorder β]
@[simp]
theorem comap_atTop (e : α ≃o β) : comap e atTop = atTop := by
simp [atTop, ← e.surjective.iInf_comp]
#align order_iso.comap_at_top OrderIso.comap_atTop
@[simp]
theorem comap_atBot (e : α ≃o β) : comap e atBot = atBot :=
e.dual.comap_atTop
#align order_iso.comap_at_bot OrderIso.comap_atBot
@[simp]
theorem map_atTop (e : α ≃o β) : map (e : α → β) atTop = atTop := by
rw [← e.comap_atTop, map_comap_of_surjective e.surjective]
#align order_iso.map_at_top OrderIso.map_atTop
@[simp]
theorem map_atBot (e : α ≃o β) : map (e : α → β) atBot = atBot :=
e.dual.map_atTop
#align order_iso.map_at_bot OrderIso.map_atBot
theorem tendsto_atTop (e : α ≃o β) : Tendsto e atTop atTop :=
e.map_atTop.le
#align order_iso.tendsto_at_top OrderIso.tendsto_atTop
theorem tendsto_atBot (e : α ≃o β) : Tendsto e atBot atBot :=
e.map_atBot.le
#align order_iso.tendsto_at_bot OrderIso.tendsto_atBot
@[simp]
| Mathlib/Order/Filter/AtTopBot.lean | 493 | 495 | theorem tendsto_atTop_iff {l : Filter γ} {f : γ → α} (e : α ≃o β) :
Tendsto (fun x => e (f x)) l atTop ↔ Tendsto f l atTop := by |
rw [← e.comap_atTop, tendsto_comap_iff, Function.comp_def]
|
/-
Copyright (c) 2018 Robert Y. Lewis. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Robert Y. Lewis, Chris Hughes
-/
import Mathlib.Algebra.Associated
import Mathlib.Algebra.BigOperators.Group.Finset
import Mathlib.Algebra.SMulWithZero
import Mathlib.Data.Nat.PartENat
import Mathlib.Tactic.Linarith
#align_import ring_theory.multiplicity from "leanprover-community/mathlib"@"e8638a0fcaf73e4500469f368ef9494e495099b3"
/-!
# Multiplicity of a divisor
For a commutative monoid, this file introduces the notion of multiplicity of a divisor and proves
several basic results on it.
## Main definitions
* `multiplicity a b`: for two elements `a` and `b` of a commutative monoid returns the largest
number `n` such that `a ^ n ∣ b` or infinity, written `⊤`, if `a ^ n ∣ b` for all natural numbers
`n`.
* `multiplicity.Finite a b`: a predicate denoting that the multiplicity of `a` in `b` is finite.
-/
variable {α β : Type*}
open Nat Part
/-- `multiplicity a b` returns the largest natural number `n` such that
`a ^ n ∣ b`, as a `PartENat` or natural with infinity. If `∀ n, a ^ n ∣ b`,
then it returns `⊤`-/
def multiplicity [Monoid α] [DecidableRel ((· ∣ ·) : α → α → Prop)] (a b : α) : PartENat :=
PartENat.find fun n => ¬a ^ (n + 1) ∣ b
#align multiplicity multiplicity
namespace multiplicity
section Monoid
variable [Monoid α] [Monoid β]
/-- `multiplicity.Finite a b` indicates that the multiplicity of `a` in `b` is finite. -/
abbrev Finite (a b : α) : Prop :=
∃ n : ℕ, ¬a ^ (n + 1) ∣ b
#align multiplicity.finite multiplicity.Finite
theorem finite_iff_dom [DecidableRel ((· ∣ ·) : α → α → Prop)] {a b : α} :
Finite a b ↔ (multiplicity a b).Dom :=
Iff.rfl
#align multiplicity.finite_iff_dom multiplicity.finite_iff_dom
theorem finite_def {a b : α} : Finite a b ↔ ∃ n : ℕ, ¬a ^ (n + 1) ∣ b :=
Iff.rfl
#align multiplicity.finite_def multiplicity.finite_def
theorem not_dvd_one_of_finite_one_right {a : α} : Finite a 1 → ¬a ∣ 1 := fun ⟨n, hn⟩ ⟨d, hd⟩ =>
hn ⟨d ^ (n + 1), (pow_mul_pow_eq_one (n + 1) hd.symm).symm⟩
#align multiplicity.not_dvd_one_of_finite_one_right multiplicity.not_dvd_one_of_finite_one_right
@[norm_cast]
theorem Int.natCast_multiplicity (a b : ℕ) : multiplicity (a : ℤ) (b : ℤ) = multiplicity a b := by
apply Part.ext'
· rw [← @finite_iff_dom ℕ, @finite_def ℕ, ← @finite_iff_dom ℤ, @finite_def ℤ]
norm_cast
· intro h1 h2
apply _root_.le_antisymm <;>
· apply Nat.find_mono
norm_cast
simp
#align multiplicity.int.coe_nat_multiplicity multiplicity.Int.natCast_multiplicity
@[deprecated (since := "2024-04-05")] alias Int.coe_nat_multiplicity := Int.natCast_multiplicity
theorem not_finite_iff_forall {a b : α} : ¬Finite a b ↔ ∀ n : ℕ, a ^ n ∣ b :=
⟨fun h n =>
Nat.casesOn n
(by
rw [_root_.pow_zero]
exact one_dvd _)
(by simpa [Finite, Classical.not_not] using h),
by simp [Finite, multiplicity, Classical.not_not]; tauto⟩
#align multiplicity.not_finite_iff_forall multiplicity.not_finite_iff_forall
theorem not_unit_of_finite {a b : α} (h : Finite a b) : ¬IsUnit a :=
let ⟨n, hn⟩ := h
hn ∘ IsUnit.dvd ∘ IsUnit.pow (n + 1)
#align multiplicity.not_unit_of_finite multiplicity.not_unit_of_finite
theorem finite_of_finite_mul_right {a b c : α} : Finite a (b * c) → Finite a b := fun ⟨n, hn⟩ =>
⟨n, fun h => hn (h.trans (dvd_mul_right _ _))⟩
#align multiplicity.finite_of_finite_mul_right multiplicity.finite_of_finite_mul_right
variable [DecidableRel ((· ∣ ·) : α → α → Prop)] [DecidableRel ((· ∣ ·) : β → β → Prop)]
theorem pow_dvd_of_le_multiplicity {a b : α} {k : ℕ} :
(k : PartENat) ≤ multiplicity a b → a ^ k ∣ b := by
rw [← PartENat.some_eq_natCast]
exact
Nat.casesOn k
(fun _ => by
rw [_root_.pow_zero]
exact one_dvd _)
fun k ⟨_, h₂⟩ => by_contradiction fun hk => Nat.find_min _ (lt_of_succ_le (h₂ ⟨k, hk⟩)) hk
#align multiplicity.pow_dvd_of_le_multiplicity multiplicity.pow_dvd_of_le_multiplicity
theorem pow_multiplicity_dvd {a b : α} (h : Finite a b) : a ^ get (multiplicity a b) h ∣ b :=
pow_dvd_of_le_multiplicity (by rw [PartENat.natCast_get])
#align multiplicity.pow_multiplicity_dvd multiplicity.pow_multiplicity_dvd
theorem is_greatest {a b : α} {m : ℕ} (hm : multiplicity a b < m) : ¬a ^ m ∣ b := fun h => by
rw [PartENat.lt_coe_iff] at hm; exact Nat.find_spec hm.fst ((pow_dvd_pow _ hm.snd).trans h)
#align multiplicity.is_greatest multiplicity.is_greatest
theorem is_greatest' {a b : α} {m : ℕ} (h : Finite a b) (hm : get (multiplicity a b) h < m) :
¬a ^ m ∣ b :=
is_greatest (by rwa [← PartENat.coe_lt_coe, PartENat.natCast_get] at hm)
#align multiplicity.is_greatest' multiplicity.is_greatest'
theorem pos_of_dvd {a b : α} (hfin : Finite a b) (hdiv : a ∣ b) :
0 < (multiplicity a b).get hfin := by
refine zero_lt_iff.2 fun h => ?_
simpa [hdiv] using is_greatest' hfin (lt_one_iff.mpr h)
#align multiplicity.pos_of_dvd multiplicity.pos_of_dvd
theorem unique {a b : α} {k : ℕ} (hk : a ^ k ∣ b) (hsucc : ¬a ^ (k + 1) ∣ b) :
(k : PartENat) = multiplicity a b :=
le_antisymm (le_of_not_gt fun hk' => is_greatest hk' hk) <| by
have : Finite a b := ⟨k, hsucc⟩
rw [PartENat.le_coe_iff]
exact ⟨this, Nat.find_min' _ hsucc⟩
#align multiplicity.unique multiplicity.unique
theorem unique' {a b : α} {k : ℕ} (hk : a ^ k ∣ b) (hsucc : ¬a ^ (k + 1) ∣ b) :
k = get (multiplicity a b) ⟨k, hsucc⟩ := by
rw [← PartENat.natCast_inj, PartENat.natCast_get, unique hk hsucc]
#align multiplicity.unique' multiplicity.unique'
theorem le_multiplicity_of_pow_dvd {a b : α} {k : ℕ} (hk : a ^ k ∣ b) :
(k : PartENat) ≤ multiplicity a b :=
le_of_not_gt fun hk' => is_greatest hk' hk
#align multiplicity.le_multiplicity_of_pow_dvd multiplicity.le_multiplicity_of_pow_dvd
theorem pow_dvd_iff_le_multiplicity {a b : α} {k : ℕ} :
a ^ k ∣ b ↔ (k : PartENat) ≤ multiplicity a b :=
⟨le_multiplicity_of_pow_dvd, pow_dvd_of_le_multiplicity⟩
#align multiplicity.pow_dvd_iff_le_multiplicity multiplicity.pow_dvd_iff_le_multiplicity
theorem multiplicity_lt_iff_not_dvd {a b : α} {k : ℕ} :
multiplicity a b < (k : PartENat) ↔ ¬a ^ k ∣ b := by rw [pow_dvd_iff_le_multiplicity, not_le]
#align multiplicity.multiplicity_lt_iff_neg_dvd multiplicity.multiplicity_lt_iff_not_dvd
theorem eq_coe_iff {a b : α} {n : ℕ} :
multiplicity a b = (n : PartENat) ↔ a ^ n ∣ b ∧ ¬a ^ (n + 1) ∣ b := by
rw [← PartENat.some_eq_natCast]
exact
⟨fun h =>
let ⟨h₁, h₂⟩ := eq_some_iff.1 h
h₂ ▸ ⟨pow_multiplicity_dvd _, is_greatest (by
rw [PartENat.lt_coe_iff]
exact ⟨h₁, lt_succ_self _⟩)⟩,
fun h => eq_some_iff.2 ⟨⟨n, h.2⟩, Eq.symm <| unique' h.1 h.2⟩⟩
#align multiplicity.eq_coe_iff multiplicity.eq_coe_iff
theorem eq_top_iff {a b : α} : multiplicity a b = ⊤ ↔ ∀ n : ℕ, a ^ n ∣ b :=
(PartENat.find_eq_top_iff _).trans <| by
simp only [Classical.not_not]
exact
⟨fun h n =>
Nat.casesOn n
(by
rw [_root_.pow_zero]
exact one_dvd _)
fun n => h _,
fun h n => h _⟩
#align multiplicity.eq_top_iff multiplicity.eq_top_iff
@[simp]
theorem isUnit_left {a : α} (b : α) (ha : IsUnit a) : multiplicity a b = ⊤ :=
eq_top_iff.2 fun _ => IsUnit.dvd (ha.pow _)
#align multiplicity.is_unit_left multiplicity.isUnit_left
-- @[simp] Porting note (#10618): simp can prove this
theorem one_left (b : α) : multiplicity 1 b = ⊤ :=
isUnit_left b isUnit_one
#align multiplicity.one_left multiplicity.one_left
@[simp]
theorem get_one_right {a : α} (ha : Finite a 1) : get (multiplicity a 1) ha = 0 := by
rw [PartENat.get_eq_iff_eq_coe, eq_coe_iff, _root_.pow_zero]
simp [not_dvd_one_of_finite_one_right ha]
#align multiplicity.get_one_right multiplicity.get_one_right
-- @[simp] Porting note (#10618): simp can prove this
theorem unit_left (a : α) (u : αˣ) : multiplicity (u : α) a = ⊤ :=
isUnit_left a u.isUnit
#align multiplicity.unit_left multiplicity.unit_left
| Mathlib/RingTheory/Multiplicity.lean | 202 | 204 | theorem multiplicity_eq_zero {a b : α} : multiplicity a b = 0 ↔ ¬a ∣ b := by |
rw [← Nat.cast_zero, eq_coe_iff]
simp only [_root_.pow_zero, isUnit_one, IsUnit.dvd, zero_add, pow_one, true_and]
|
/-
Copyright (c) 2020 Riccardo Brasca. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Riccardo Brasca
-/
import Mathlib.RingTheory.Polynomial.Cyclotomic.Roots
import Mathlib.Data.ZMod.Algebra
#align_import ring_theory.polynomial.cyclotomic.expand from "leanprover-community/mathlib"@"0723536a0522d24fc2f159a096fb3304bef77472"
/-!
# Cyclotomic polynomials and `expand`.
We gather results relating cyclotomic polynomials and `expand`.
## Main results
* `Polynomial.cyclotomic_expand_eq_cyclotomic_mul` : If `p` is a prime such that `¬ p ∣ n`, then
`expand R p (cyclotomic n R) = (cyclotomic (n * p) R) * (cyclotomic n R)`.
* `Polynomial.cyclotomic_expand_eq_cyclotomic` : If `p` is a prime such that `p ∣ n`, then
`expand R p (cyclotomic n R) = cyclotomic (p * n) R`.
* `Polynomial.cyclotomic_mul_prime_eq_pow_of_not_dvd` : If `R` is of characteristic `p` and
`¬p ∣ n`, then `cyclotomic (n * p) R = (cyclotomic n R) ^ (p - 1)`.
* `Polynomial.cyclotomic_mul_prime_dvd_eq_pow` : If `R` is of characteristic `p` and `p ∣ n`, then
`cyclotomic (n * p) R = (cyclotomic n R) ^ p`.
* `Polynomial.cyclotomic_mul_prime_pow_eq` : If `R` is of characteristic `p` and `¬p ∣ m`, then
`cyclotomic (p ^ k * m) R = (cyclotomic m R) ^ (p ^ k - p ^ (k - 1))`.
-/
namespace Polynomial
/-- If `p` is a prime such that `¬ p ∣ n`, then
`expand R p (cyclotomic n R) = (cyclotomic (n * p) R) * (cyclotomic n R)`. -/
@[simp]
theorem cyclotomic_expand_eq_cyclotomic_mul {p n : ℕ} (hp : Nat.Prime p) (hdiv : ¬p ∣ n)
(R : Type*) [CommRing R] :
expand R p (cyclotomic n R) = cyclotomic (n * p) R * cyclotomic n R := by
rcases Nat.eq_zero_or_pos n with (rfl | hnpos)
· simp
haveI := NeZero.of_pos hnpos
suffices expand ℤ p (cyclotomic n ℤ) = cyclotomic (n * p) ℤ * cyclotomic n ℤ by
rw [← map_cyclotomic_int, ← map_expand, this, Polynomial.map_mul, map_cyclotomic_int,
map_cyclotomic]
refine eq_of_monic_of_dvd_of_natDegree_le ((cyclotomic.monic _ ℤ).mul (cyclotomic.monic _ ℤ))
((cyclotomic.monic n ℤ).expand hp.pos) ?_ ?_
· refine (IsPrimitive.Int.dvd_iff_map_cast_dvd_map_cast _ _
(IsPrimitive.mul (cyclotomic.isPrimitive (n * p) ℤ) (cyclotomic.isPrimitive n ℤ))
((cyclotomic.monic n ℤ).expand hp.pos).isPrimitive).2 ?_
rw [Polynomial.map_mul, map_cyclotomic_int, map_cyclotomic_int, map_expand, map_cyclotomic_int]
refine IsCoprime.mul_dvd (cyclotomic.isCoprime_rat fun h => ?_) ?_ ?_
· replace h : n * p = n * 1 := by simp [h]
exact Nat.Prime.ne_one hp (mul_left_cancel₀ hnpos.ne' h)
· have hpos : 0 < n * p := mul_pos hnpos hp.pos
have hprim := Complex.isPrimitiveRoot_exp _ hpos.ne'
rw [cyclotomic_eq_minpoly_rat hprim hpos]
refine minpoly.dvd ℚ _ ?_
rw [aeval_def, ← eval_map, map_expand, map_cyclotomic, expand_eval, ← IsRoot.def,
@isRoot_cyclotomic_iff]
convert IsPrimitiveRoot.pow_of_dvd hprim hp.ne_zero (dvd_mul_left p n)
rw [Nat.mul_div_cancel _ (Nat.Prime.pos hp)]
· have hprim := Complex.isPrimitiveRoot_exp _ hnpos.ne.symm
rw [cyclotomic_eq_minpoly_rat hprim hnpos]
refine minpoly.dvd ℚ _ ?_
rw [aeval_def, ← eval_map, map_expand, expand_eval, ← IsRoot.def, ←
cyclotomic_eq_minpoly_rat hprim hnpos, map_cyclotomic, @isRoot_cyclotomic_iff]
exact IsPrimitiveRoot.pow_of_prime hprim hp hdiv
· rw [natDegree_expand, natDegree_cyclotomic,
natDegree_mul (cyclotomic_ne_zero _ ℤ) (cyclotomic_ne_zero _ ℤ), natDegree_cyclotomic,
natDegree_cyclotomic, mul_comm n,
Nat.totient_mul ((Nat.Prime.coprime_iff_not_dvd hp).2 hdiv), Nat.totient_prime hp,
mul_comm (p - 1), ← Nat.mul_succ, Nat.sub_one, Nat.succ_pred_eq_of_pos hp.pos]
#align polynomial.cyclotomic_expand_eq_cyclotomic_mul Polynomial.cyclotomic_expand_eq_cyclotomic_mul
/-- If `p` is a prime such that `p ∣ n`, then
`expand R p (cyclotomic n R) = cyclotomic (p * n) R`. -/
@[simp]
| Mathlib/RingTheory/Polynomial/Cyclotomic/Expand.lean | 78 | 96 | theorem cyclotomic_expand_eq_cyclotomic {p n : ℕ} (hp : Nat.Prime p) (hdiv : p ∣ n) (R : Type*)
[CommRing R] : expand R p (cyclotomic n R) = cyclotomic (n * p) R := by |
rcases n.eq_zero_or_pos with (rfl | hzero)
· simp
haveI := NeZero.of_pos hzero
suffices expand ℤ p (cyclotomic n ℤ) = cyclotomic (n * p) ℤ by
rw [← map_cyclotomic_int, ← map_expand, this, map_cyclotomic_int]
refine eq_of_monic_of_dvd_of_natDegree_le (cyclotomic.monic _ ℤ)
((cyclotomic.monic n ℤ).expand hp.pos) ?_ ?_
· have hpos := Nat.mul_pos hzero hp.pos
have hprim := Complex.isPrimitiveRoot_exp _ hpos.ne.symm
rw [cyclotomic_eq_minpoly hprim hpos]
refine minpoly.isIntegrallyClosed_dvd (hprim.isIntegral hpos) ?_
rw [aeval_def, ← eval_map, map_expand, map_cyclotomic, expand_eval, ← IsRoot.def,
@isRoot_cyclotomic_iff]
convert IsPrimitiveRoot.pow_of_dvd hprim hp.ne_zero (dvd_mul_left p n)
rw [Nat.mul_div_cancel _ hp.pos]
· rw [natDegree_expand, natDegree_cyclotomic, natDegree_cyclotomic, mul_comm n,
Nat.totient_mul_of_prime_of_dvd hp hdiv, mul_comm]
|
/-
Copyright (c) 2019 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Yakov Pechersky
-/
import Mathlib.Data.List.Nodup
import Mathlib.Data.List.Zip
import Mathlib.Data.Nat.Defs
import Mathlib.Data.List.Infix
#align_import data.list.rotate from "leanprover-community/mathlib"@"f694c7dead66f5d4c80f446c796a5aad14707f0e"
/-!
# List rotation
This file proves basic results about `List.rotate`, the list rotation.
## Main declarations
* `List.IsRotated l₁ l₂`: States that `l₁` is a rotated version of `l₂`.
* `List.cyclicPermutations l`: The list of all cyclic permutants of `l`, up to the length of `l`.
## Tags
rotated, rotation, permutation, cycle
-/
universe u
variable {α : Type u}
open Nat Function
namespace List
theorem rotate_mod (l : List α) (n : ℕ) : l.rotate (n % l.length) = l.rotate n := by simp [rotate]
#align list.rotate_mod List.rotate_mod
@[simp]
theorem rotate_nil (n : ℕ) : ([] : List α).rotate n = [] := by simp [rotate]
#align list.rotate_nil List.rotate_nil
@[simp]
theorem rotate_zero (l : List α) : l.rotate 0 = l := by simp [rotate]
#align list.rotate_zero List.rotate_zero
-- Porting note: removing simp, simp can prove it
theorem rotate'_nil (n : ℕ) : ([] : List α).rotate' n = [] := by cases n <;> rfl
#align list.rotate'_nil List.rotate'_nil
@[simp]
theorem rotate'_zero (l : List α) : l.rotate' 0 = l := by cases l <;> rfl
#align list.rotate'_zero List.rotate'_zero
theorem rotate'_cons_succ (l : List α) (a : α) (n : ℕ) :
(a :: l : List α).rotate' n.succ = (l ++ [a]).rotate' n := by simp [rotate']
#align list.rotate'_cons_succ List.rotate'_cons_succ
@[simp]
theorem length_rotate' : ∀ (l : List α) (n : ℕ), (l.rotate' n).length = l.length
| [], _ => by simp
| a :: l, 0 => rfl
| a :: l, n + 1 => by rw [List.rotate', length_rotate' (l ++ [a]) n]; simp
#align list.length_rotate' List.length_rotate'
theorem rotate'_eq_drop_append_take :
∀ {l : List α} {n : ℕ}, n ≤ l.length → l.rotate' n = l.drop n ++ l.take n
| [], n, h => by simp [drop_append_of_le_length h]
| l, 0, h => by simp [take_append_of_le_length h]
| a :: l, n + 1, h => by
have hnl : n ≤ l.length := le_of_succ_le_succ h
have hnl' : n ≤ (l ++ [a]).length := by
rw [length_append, length_cons, List.length]; exact le_of_succ_le h
rw [rotate'_cons_succ, rotate'_eq_drop_append_take hnl', drop, take,
drop_append_of_le_length hnl, take_append_of_le_length hnl]; simp
#align list.rotate'_eq_drop_append_take List.rotate'_eq_drop_append_take
theorem rotate'_rotate' : ∀ (l : List α) (n m : ℕ), (l.rotate' n).rotate' m = l.rotate' (n + m)
| a :: l, 0, m => by simp
| [], n, m => by simp
| a :: l, n + 1, m => by
rw [rotate'_cons_succ, rotate'_rotate' _ n, Nat.add_right_comm, ← rotate'_cons_succ,
Nat.succ_eq_add_one]
#align list.rotate'_rotate' List.rotate'_rotate'
@[simp]
theorem rotate'_length (l : List α) : rotate' l l.length = l := by
rw [rotate'_eq_drop_append_take le_rfl]; simp
#align list.rotate'_length List.rotate'_length
@[simp]
theorem rotate'_length_mul (l : List α) : ∀ n : ℕ, l.rotate' (l.length * n) = l
| 0 => by simp
| n + 1 =>
calc
l.rotate' (l.length * (n + 1)) =
(l.rotate' (l.length * n)).rotate' (l.rotate' (l.length * n)).length := by
simp [-rotate'_length, Nat.mul_succ, rotate'_rotate']
_ = l := by rw [rotate'_length, rotate'_length_mul l n]
#align list.rotate'_length_mul List.rotate'_length_mul
theorem rotate'_mod (l : List α) (n : ℕ) : l.rotate' (n % l.length) = l.rotate' n :=
calc
l.rotate' (n % l.length) =
(l.rotate' (n % l.length)).rotate' ((l.rotate' (n % l.length)).length * (n / l.length)) :=
by rw [rotate'_length_mul]
_ = l.rotate' n := by rw [rotate'_rotate', length_rotate', Nat.mod_add_div]
#align list.rotate'_mod List.rotate'_mod
theorem rotate_eq_rotate' (l : List α) (n : ℕ) : l.rotate n = l.rotate' n :=
if h : l.length = 0 then by simp_all [length_eq_zero]
else by
rw [← rotate'_mod,
rotate'_eq_drop_append_take (le_of_lt (Nat.mod_lt _ (Nat.pos_of_ne_zero h)))];
simp [rotate]
#align list.rotate_eq_rotate' List.rotate_eq_rotate'
theorem rotate_cons_succ (l : List α) (a : α) (n : ℕ) :
(a :: l : List α).rotate (n + 1) = (l ++ [a]).rotate n := by
rw [rotate_eq_rotate', rotate_eq_rotate', rotate'_cons_succ]
#align list.rotate_cons_succ List.rotate_cons_succ
@[simp]
theorem mem_rotate : ∀ {l : List α} {a : α} {n : ℕ}, a ∈ l.rotate n ↔ a ∈ l
| [], _, n => by simp
| a :: l, _, 0 => by simp
| a :: l, _, n + 1 => by simp [rotate_cons_succ, mem_rotate, or_comm]
#align list.mem_rotate List.mem_rotate
@[simp]
theorem length_rotate (l : List α) (n : ℕ) : (l.rotate n).length = l.length := by
rw [rotate_eq_rotate', length_rotate']
#align list.length_rotate List.length_rotate
@[simp]
theorem rotate_replicate (a : α) (n : ℕ) (k : ℕ) : (replicate n a).rotate k = replicate n a :=
eq_replicate.2 ⟨by rw [length_rotate, length_replicate], fun b hb =>
eq_of_mem_replicate <| mem_rotate.1 hb⟩
#align list.rotate_replicate List.rotate_replicate
theorem rotate_eq_drop_append_take {l : List α} {n : ℕ} :
n ≤ l.length → l.rotate n = l.drop n ++ l.take n := by
rw [rotate_eq_rotate']; exact rotate'_eq_drop_append_take
#align list.rotate_eq_drop_append_take List.rotate_eq_drop_append_take
theorem rotate_eq_drop_append_take_mod {l : List α} {n : ℕ} :
l.rotate n = l.drop (n % l.length) ++ l.take (n % l.length) := by
rcases l.length.zero_le.eq_or_lt with hl | hl
· simp [eq_nil_of_length_eq_zero hl.symm]
rw [← rotate_eq_drop_append_take (n.mod_lt hl).le, rotate_mod]
#align list.rotate_eq_drop_append_take_mod List.rotate_eq_drop_append_take_mod
@[simp]
theorem rotate_append_length_eq (l l' : List α) : (l ++ l').rotate l.length = l' ++ l := by
rw [rotate_eq_rotate']
induction l generalizing l'
· simp
· simp_all [rotate']
#align list.rotate_append_length_eq List.rotate_append_length_eq
theorem rotate_rotate (l : List α) (n m : ℕ) : (l.rotate n).rotate m = l.rotate (n + m) := by
rw [rotate_eq_rotate', rotate_eq_rotate', rotate_eq_rotate', rotate'_rotate']
#align list.rotate_rotate List.rotate_rotate
@[simp]
theorem rotate_length (l : List α) : rotate l l.length = l := by
rw [rotate_eq_rotate', rotate'_length]
#align list.rotate_length List.rotate_length
@[simp]
theorem rotate_length_mul (l : List α) (n : ℕ) : l.rotate (l.length * n) = l := by
rw [rotate_eq_rotate', rotate'_length_mul]
#align list.rotate_length_mul List.rotate_length_mul
theorem rotate_perm (l : List α) (n : ℕ) : l.rotate n ~ l := by
rw [rotate_eq_rotate']
induction' n with n hn generalizing l
· simp
· cases' l with hd tl
· simp
· rw [rotate'_cons_succ]
exact (hn _).trans (perm_append_singleton _ _)
#align list.rotate_perm List.rotate_perm
@[simp]
theorem nodup_rotate {l : List α} {n : ℕ} : Nodup (l.rotate n) ↔ Nodup l :=
(rotate_perm l n).nodup_iff
#align list.nodup_rotate List.nodup_rotate
@[simp]
theorem rotate_eq_nil_iff {l : List α} {n : ℕ} : l.rotate n = [] ↔ l = [] := by
induction' n with n hn generalizing l
· simp
· cases' l with hd tl
· simp
· simp [rotate_cons_succ, hn]
#align list.rotate_eq_nil_iff List.rotate_eq_nil_iff
@[simp]
theorem nil_eq_rotate_iff {l : List α} {n : ℕ} : [] = l.rotate n ↔ [] = l := by
rw [eq_comm, rotate_eq_nil_iff, eq_comm]
#align list.nil_eq_rotate_iff List.nil_eq_rotate_iff
@[simp]
theorem rotate_singleton (x : α) (n : ℕ) : [x].rotate n = [x] :=
rotate_replicate x 1 n
#align list.rotate_singleton List.rotate_singleton
theorem zipWith_rotate_distrib {β γ : Type*} (f : α → β → γ) (l : List α) (l' : List β) (n : ℕ)
(h : l.length = l'.length) :
(zipWith f l l').rotate n = zipWith f (l.rotate n) (l'.rotate n) := by
rw [rotate_eq_drop_append_take_mod, rotate_eq_drop_append_take_mod,
rotate_eq_drop_append_take_mod, h, zipWith_append, ← zipWith_distrib_drop, ←
zipWith_distrib_take, List.length_zipWith, h, min_self]
rw [length_drop, length_drop, h]
#align list.zip_with_rotate_distrib List.zipWith_rotate_distrib
attribute [local simp] rotate_cons_succ
-- Porting note: removing @[simp], simp can prove it
theorem zipWith_rotate_one {β : Type*} (f : α → α → β) (x y : α) (l : List α) :
zipWith f (x :: y :: l) ((x :: y :: l).rotate 1) = f x y :: zipWith f (y :: l) (l ++ [x]) := by
simp
#align list.zip_with_rotate_one List.zipWith_rotate_one
theorem get?_rotate {l : List α} {n m : ℕ} (hml : m < l.length) :
(l.rotate n).get? m = l.get? ((m + n) % l.length) := by
rw [rotate_eq_drop_append_take_mod]
rcases lt_or_le m (l.drop (n % l.length)).length with hm | hm
· rw [get?_append hm, get?_drop, ← add_mod_mod]
rw [length_drop, Nat.lt_sub_iff_add_lt] at hm
rw [mod_eq_of_lt hm, Nat.add_comm]
· have hlt : n % length l < length l := mod_lt _ (m.zero_le.trans_lt hml)
rw [get?_append_right hm, get?_take, length_drop]
· congr 1
rw [length_drop] at hm
have hm' := Nat.sub_le_iff_le_add'.1 hm
have : n % length l + m - length l < length l := by
rw [Nat.sub_lt_iff_lt_add' hm']
exact Nat.add_lt_add hlt hml
conv_rhs => rw [Nat.add_comm m, ← mod_add_mod, mod_eq_sub_mod hm', mod_eq_of_lt this]
rw [← Nat.add_right_inj, ← Nat.add_sub_assoc, Nat.add_sub_sub_cancel, Nat.add_sub_cancel',
Nat.add_comm]
exacts [hm', hlt.le, hm]
· rwa [Nat.sub_lt_iff_lt_add hm, length_drop, Nat.sub_add_cancel hlt.le]
#align list.nth_rotate List.get?_rotate
-- Porting note (#10756): new lemma
theorem get_rotate (l : List α) (n : ℕ) (k : Fin (l.rotate n).length) :
(l.rotate n).get k =
l.get ⟨(k + n) % l.length, mod_lt _ (length_rotate l n ▸ k.1.zero_le.trans_lt k.2)⟩ := by
rw [← Option.some_inj, ← get?_eq_get, ← get?_eq_get, get?_rotate]
exact k.2.trans_eq (length_rotate _ _)
theorem head?_rotate {l : List α} {n : ℕ} (h : n < l.length) : head? (l.rotate n) = l.get? n := by
rw [← get?_zero, get?_rotate (n.zero_le.trans_lt h), Nat.zero_add, Nat.mod_eq_of_lt h]
#align list.head'_rotate List.head?_rotate
-- Porting note: moved down from its original location below `get_rotate` so that the
-- non-deprecated lemma does not use the deprecated version
set_option linter.deprecated false in
@[deprecated get_rotate (since := "2023-01-13")]
theorem nthLe_rotate (l : List α) (n k : ℕ) (hk : k < (l.rotate n).length) :
(l.rotate n).nthLe k hk =
l.nthLe ((k + n) % l.length) (mod_lt _ (length_rotate l n ▸ k.zero_le.trans_lt hk)) :=
get_rotate l n ⟨k, hk⟩
#align list.nth_le_rotate List.nthLe_rotate
set_option linter.deprecated false in
theorem nthLe_rotate_one (l : List α) (k : ℕ) (hk : k < (l.rotate 1).length) :
(l.rotate 1).nthLe k hk =
l.nthLe ((k + 1) % l.length) (mod_lt _ (length_rotate l 1 ▸ k.zero_le.trans_lt hk)) :=
nthLe_rotate l 1 k hk
#align list.nth_le_rotate_one List.nthLe_rotate_one
-- Porting note (#10756): new lemma
/-- A version of `List.get_rotate` that represents `List.get l` in terms of
`List.get (List.rotate l n)`, not vice versa. Can be used instead of rewriting `List.get_rotate`
from right to left. -/
theorem get_eq_get_rotate (l : List α) (n : ℕ) (k : Fin l.length) :
l.get k = (l.rotate n).get ⟨(l.length - n % l.length + k) % l.length,
(Nat.mod_lt _ (k.1.zero_le.trans_lt k.2)).trans_eq (length_rotate _ _).symm⟩ := by
rw [get_rotate]
refine congr_arg l.get (Fin.eq_of_val_eq ?_)
simp only [mod_add_mod]
rw [← add_mod_mod, Nat.add_right_comm, Nat.sub_add_cancel, add_mod_left, mod_eq_of_lt]
exacts [k.2, (mod_lt _ (k.1.zero_le.trans_lt k.2)).le]
set_option linter.deprecated false in
/-- A variant of `List.nthLe_rotate` useful for rewrites from right to left. -/
@[deprecated get_eq_get_rotate]
theorem nthLe_rotate' (l : List α) (n k : ℕ) (hk : k < l.length) :
(l.rotate n).nthLe ((l.length - n % l.length + k) % l.length)
((Nat.mod_lt _ (k.zero_le.trans_lt hk)).trans_le (length_rotate _ _).ge) =
l.nthLe k hk :=
(get_eq_get_rotate l n ⟨k, hk⟩).symm
#align list.nth_le_rotate' List.nthLe_rotate'
theorem rotate_eq_self_iff_eq_replicate [hα : Nonempty α] :
∀ {l : List α}, (∀ n, l.rotate n = l) ↔ ∃ a, l = replicate l.length a
| [] => by simp
| a :: l => ⟨fun h => ⟨a, ext_get (length_replicate _ _).symm fun n h₁ h₂ => by
rw [get_replicate, ← Option.some_inj, ← get?_eq_get, ← head?_rotate h₁, h, head?_cons]⟩,
fun ⟨b, hb⟩ n => by rw [hb, rotate_replicate]⟩
#align list.rotate_eq_self_iff_eq_replicate List.rotate_eq_self_iff_eq_replicate
theorem rotate_one_eq_self_iff_eq_replicate [Nonempty α] {l : List α} :
l.rotate 1 = l ↔ ∃ a : α, l = List.replicate l.length a :=
⟨fun h =>
rotate_eq_self_iff_eq_replicate.mp fun n =>
Nat.rec l.rotate_zero (fun n hn => by rwa [Nat.succ_eq_add_one, ← l.rotate_rotate, hn]) n,
fun h => rotate_eq_self_iff_eq_replicate.mpr h 1⟩
#align list.rotate_one_eq_self_iff_eq_replicate List.rotate_one_eq_self_iff_eq_replicate
theorem rotate_injective (n : ℕ) : Function.Injective fun l : List α => l.rotate n := by
rintro l l' (h : l.rotate n = l'.rotate n)
have hle : l.length = l'.length := (l.length_rotate n).symm.trans (h.symm ▸ l'.length_rotate n)
rw [rotate_eq_drop_append_take_mod, rotate_eq_drop_append_take_mod] at h
obtain ⟨hd, ht⟩ := append_inj h (by simp_all)
rw [← take_append_drop _ l, ht, hd, take_append_drop]
#align list.rotate_injective List.rotate_injective
@[simp]
theorem rotate_eq_rotate {l l' : List α} {n : ℕ} : l.rotate n = l'.rotate n ↔ l = l' :=
(rotate_injective n).eq_iff
#align list.rotate_eq_rotate List.rotate_eq_rotate
theorem rotate_eq_iff {l l' : List α} {n : ℕ} :
l.rotate n = l' ↔ l = l'.rotate (l'.length - n % l'.length) := by
rw [← @rotate_eq_rotate _ l _ n, rotate_rotate, ← rotate_mod l', add_mod]
rcases l'.length.zero_le.eq_or_lt with hl | hl
· rw [eq_nil_of_length_eq_zero hl.symm, rotate_nil]
· rcases (Nat.zero_le (n % l'.length)).eq_or_lt with hn | hn
· simp [← hn]
· rw [mod_eq_of_lt (Nat.sub_lt hl hn), Nat.sub_add_cancel, mod_self, rotate_zero]
exact (Nat.mod_lt _ hl).le
#align list.rotate_eq_iff List.rotate_eq_iff
@[simp]
theorem rotate_eq_singleton_iff {l : List α} {n : ℕ} {x : α} : l.rotate n = [x] ↔ l = [x] := by
rw [rotate_eq_iff, rotate_singleton]
#align list.rotate_eq_singleton_iff List.rotate_eq_singleton_iff
@[simp]
theorem singleton_eq_rotate_iff {l : List α} {n : ℕ} {x : α} : [x] = l.rotate n ↔ [x] = l := by
rw [eq_comm, rotate_eq_singleton_iff, eq_comm]
#align list.singleton_eq_rotate_iff List.singleton_eq_rotate_iff
theorem reverse_rotate (l : List α) (n : ℕ) :
(l.rotate n).reverse = l.reverse.rotate (l.length - n % l.length) := by
rw [← length_reverse l, ← rotate_eq_iff]
induction' n with n hn generalizing l
· simp
· cases' l with hd tl
· simp
· rw [rotate_cons_succ, ← rotate_rotate, hn]
simp
#align list.reverse_rotate List.reverse_rotate
theorem rotate_reverse (l : List α) (n : ℕ) :
l.reverse.rotate n = (l.rotate (l.length - n % l.length)).reverse := by
rw [← reverse_reverse l]
simp_rw [reverse_rotate, reverse_reverse, rotate_eq_iff, rotate_rotate, length_rotate,
length_reverse]
rw [← length_reverse l]
let k := n % l.reverse.length
cases' hk' : k with k'
· simp_all! [k, length_reverse, ← rotate_rotate]
· cases' l with x l
· simp
· rw [Nat.mod_eq_of_lt, Nat.sub_add_cancel, rotate_length]
· exact Nat.sub_le _ _
· exact Nat.sub_lt (by simp) (by simp_all! [k])
#align list.rotate_reverse List.rotate_reverse
theorem map_rotate {β : Type*} (f : α → β) (l : List α) (n : ℕ) :
map f (l.rotate n) = (map f l).rotate n := by
induction' n with n hn IH generalizing l
· simp
· cases' l with hd tl
· simp
· simp [hn]
#align list.map_rotate List.map_rotate
theorem Nodup.rotate_congr {l : List α} (hl : l.Nodup) (hn : l ≠ []) (i j : ℕ)
(h : l.rotate i = l.rotate j) : i % l.length = j % l.length := by
rw [← rotate_mod l i, ← rotate_mod l j] at h
simpa only [head?_rotate, mod_lt, length_pos_of_ne_nil hn, get?_eq_get, Option.some_inj,
hl.get_inj_iff, Fin.ext_iff] using congr_arg head? h
#align list.nodup.rotate_congr List.Nodup.rotate_congr
theorem Nodup.rotate_congr_iff {l : List α} (hl : l.Nodup) {i j : ℕ} :
l.rotate i = l.rotate j ↔ i % l.length = j % l.length ∨ l = [] := by
rcases eq_or_ne l [] with rfl | hn
· simp
· simp only [hn, or_false]
refine ⟨hl.rotate_congr hn _ _, fun h ↦ ?_⟩
rw [← rotate_mod, h, rotate_mod]
theorem Nodup.rotate_eq_self_iff {l : List α} (hl : l.Nodup) {n : ℕ} :
l.rotate n = l ↔ n % l.length = 0 ∨ l = [] := by
rw [← zero_mod, ← hl.rotate_congr_iff, rotate_zero]
#align list.nodup.rotate_eq_self_iff List.Nodup.rotate_eq_self_iff
section IsRotated
variable (l l' : List α)
/-- `IsRotated l₁ l₂` or `l₁ ~r l₂` asserts that `l₁` and `l₂` are cyclic permutations
of each other. This is defined by claiming that `∃ n, l.rotate n = l'`. -/
def IsRotated : Prop :=
∃ n, l.rotate n = l'
#align list.is_rotated List.IsRotated
@[inherit_doc List.IsRotated]
infixr:1000 " ~r " => IsRotated
variable {l l'}
@[refl]
theorem IsRotated.refl (l : List α) : l ~r l :=
⟨0, by simp⟩
#align list.is_rotated.refl List.IsRotated.refl
@[symm]
theorem IsRotated.symm (h : l ~r l') : l' ~r l := by
obtain ⟨n, rfl⟩ := h
cases' l with hd tl
· exists 0
· use (hd :: tl).length * n - n
rw [rotate_rotate, Nat.add_sub_cancel', rotate_length_mul]
exact Nat.le_mul_of_pos_left _ (by simp)
#align list.is_rotated.symm List.IsRotated.symm
theorem isRotated_comm : l ~r l' ↔ l' ~r l :=
⟨IsRotated.symm, IsRotated.symm⟩
#align list.is_rotated_comm List.isRotated_comm
@[simp]
protected theorem IsRotated.forall (l : List α) (n : ℕ) : l.rotate n ~r l :=
IsRotated.symm ⟨n, rfl⟩
#align list.is_rotated.forall List.IsRotated.forall
@[trans]
theorem IsRotated.trans : ∀ {l l' l'' : List α}, l ~r l' → l' ~r l'' → l ~r l''
| _, _, _, ⟨n, rfl⟩, ⟨m, rfl⟩ => ⟨n + m, by rw [rotate_rotate]⟩
#align list.is_rotated.trans List.IsRotated.trans
theorem IsRotated.eqv : Equivalence (@IsRotated α) :=
Equivalence.mk IsRotated.refl IsRotated.symm IsRotated.trans
#align list.is_rotated.eqv List.IsRotated.eqv
/-- The relation `List.IsRotated l l'` forms a `Setoid` of cycles. -/
def IsRotated.setoid (α : Type*) : Setoid (List α) where
r := IsRotated
iseqv := IsRotated.eqv
#align list.is_rotated.setoid List.IsRotated.setoid
theorem IsRotated.perm (h : l ~r l') : l ~ l' :=
Exists.elim h fun _ hl => hl ▸ (rotate_perm _ _).symm
#align list.is_rotated.perm List.IsRotated.perm
theorem IsRotated.nodup_iff (h : l ~r l') : Nodup l ↔ Nodup l' :=
h.perm.nodup_iff
#align list.is_rotated.nodup_iff List.IsRotated.nodup_iff
theorem IsRotated.mem_iff (h : l ~r l') {a : α} : a ∈ l ↔ a ∈ l' :=
h.perm.mem_iff
#align list.is_rotated.mem_iff List.IsRotated.mem_iff
@[simp]
theorem isRotated_nil_iff : l ~r [] ↔ l = [] :=
⟨fun ⟨n, hn⟩ => by simpa using hn, fun h => h ▸ by rfl⟩
#align list.is_rotated_nil_iff List.isRotated_nil_iff
@[simp]
theorem isRotated_nil_iff' : [] ~r l ↔ [] = l := by
rw [isRotated_comm, isRotated_nil_iff, eq_comm]
#align list.is_rotated_nil_iff' List.isRotated_nil_iff'
@[simp]
theorem isRotated_singleton_iff {x : α} : l ~r [x] ↔ l = [x] :=
⟨fun ⟨n, hn⟩ => by simpa using hn, fun h => h ▸ by rfl⟩
#align list.is_rotated_singleton_iff List.isRotated_singleton_iff
@[simp]
theorem isRotated_singleton_iff' {x : α} : [x] ~r l ↔ [x] = l := by
rw [isRotated_comm, isRotated_singleton_iff, eq_comm]
#align list.is_rotated_singleton_iff' List.isRotated_singleton_iff'
theorem isRotated_concat (hd : α) (tl : List α) : (tl ++ [hd]) ~r (hd :: tl) :=
IsRotated.symm ⟨1, by simp⟩
#align list.is_rotated_concat List.isRotated_concat
theorem isRotated_append : (l ++ l') ~r (l' ++ l) :=
⟨l.length, by simp⟩
#align list.is_rotated_append List.isRotated_append
theorem IsRotated.reverse (h : l ~r l') : l.reverse ~r l'.reverse := by
obtain ⟨n, rfl⟩ := h
exact ⟨_, (reverse_rotate _ _).symm⟩
#align list.is_rotated.reverse List.IsRotated.reverse
theorem isRotated_reverse_comm_iff : l.reverse ~r l' ↔ l ~r l'.reverse := by
constructor <;>
· intro h
simpa using h.reverse
#align list.is_rotated_reverse_comm_iff List.isRotated_reverse_comm_iff
@[simp]
theorem isRotated_reverse_iff : l.reverse ~r l'.reverse ↔ l ~r l' := by
simp [isRotated_reverse_comm_iff]
#align list.is_rotated_reverse_iff List.isRotated_reverse_iff
theorem isRotated_iff_mod : l ~r l' ↔ ∃ n ≤ l.length, l.rotate n = l' := by
refine ⟨fun h => ?_, fun ⟨n, _, h⟩ => ⟨n, h⟩⟩
obtain ⟨n, rfl⟩ := h
cases' l with hd tl
· simp
· refine ⟨n % (hd :: tl).length, ?_, rotate_mod _ _⟩
refine (Nat.mod_lt _ ?_).le
simp
#align list.is_rotated_iff_mod List.isRotated_iff_mod
theorem isRotated_iff_mem_map_range : l ~r l' ↔ l' ∈ (List.range (l.length + 1)).map l.rotate := by
simp_rw [mem_map, mem_range, isRotated_iff_mod]
exact
⟨fun ⟨n, hn, h⟩ => ⟨n, Nat.lt_succ_of_le hn, h⟩,
fun ⟨n, hn, h⟩ => ⟨n, Nat.le_of_lt_succ hn, h⟩⟩
#align list.is_rotated_iff_mem_map_range List.isRotated_iff_mem_map_range
-- Porting note: @[congr] only works for equality.
-- @[congr]
theorem IsRotated.map {β : Type*} {l₁ l₂ : List α} (h : l₁ ~r l₂) (f : α → β) :
map f l₁ ~r map f l₂ := by
obtain ⟨n, rfl⟩ := h
rw [map_rotate]
use n
#align list.is_rotated.map List.IsRotated.map
/-- List of all cyclic permutations of `l`.
The `cyclicPermutations` of a nonempty list `l` will always contain `List.length l` elements.
This implies that under certain conditions, there are duplicates in `List.cyclicPermutations l`.
The `n`th entry is equal to `l.rotate n`, proven in `List.get_cyclicPermutations`.
The proof that every cyclic permutant of `l` is in the list is `List.mem_cyclicPermutations_iff`.
cyclicPermutations [1, 2, 3, 2, 4] =
[[1, 2, 3, 2, 4], [2, 3, 2, 4, 1], [3, 2, 4, 1, 2],
[2, 4, 1, 2, 3], [4, 1, 2, 3, 2]] -/
def cyclicPermutations : List α → List (List α)
| [] => [[]]
| l@(_ :: _) => dropLast (zipWith (· ++ ·) (tails l) (inits l))
#align list.cyclic_permutations List.cyclicPermutations
@[simp]
theorem cyclicPermutations_nil : cyclicPermutations ([] : List α) = [[]] :=
rfl
#align list.cyclic_permutations_nil List.cyclicPermutations_nil
theorem cyclicPermutations_cons (x : α) (l : List α) :
cyclicPermutations (x :: l) = dropLast (zipWith (· ++ ·) (tails (x :: l)) (inits (x :: l))) :=
rfl
#align list.cyclic_permutations_cons List.cyclicPermutations_cons
theorem cyclicPermutations_of_ne_nil (l : List α) (h : l ≠ []) :
cyclicPermutations l = dropLast (zipWith (· ++ ·) (tails l) (inits l)) := by
obtain ⟨hd, tl, rfl⟩ := exists_cons_of_ne_nil h
exact cyclicPermutations_cons _ _
#align list.cyclic_permutations_of_ne_nil List.cyclicPermutations_of_ne_nil
theorem length_cyclicPermutations_cons (x : α) (l : List α) :
length (cyclicPermutations (x :: l)) = length l + 1 := by simp [cyclicPermutations_cons]
#align list.length_cyclic_permutations_cons List.length_cyclicPermutations_cons
@[simp]
theorem length_cyclicPermutations_of_ne_nil (l : List α) (h : l ≠ []) :
length (cyclicPermutations l) = length l := by simp [cyclicPermutations_of_ne_nil _ h]
#align list.length_cyclic_permutations_of_ne_nil List.length_cyclicPermutations_of_ne_nil
@[simp]
theorem cyclicPermutations_ne_nil : ∀ l : List α, cyclicPermutations l ≠ []
| a::l, h => by simpa using congr_arg length h
@[simp]
theorem get_cyclicPermutations (l : List α) (n : Fin (length (cyclicPermutations l))) :
(cyclicPermutations l).get n = l.rotate n := by
cases l with
| nil => simp
| cons a l =>
simp only [cyclicPermutations_cons, get_dropLast, get_zipWith, get_tails, get_inits]
rw [rotate_eq_drop_append_take (by simpa using n.2.le)]
#align list.nth_le_cyclic_permutations List.get_cyclicPermutations
@[simp]
| Mathlib/Data/List/Rotate.lean | 596 | 599 | theorem head_cyclicPermutations (l : List α) :
(cyclicPermutations l).head (cyclicPermutations_ne_nil l) = l := by |
have h : 0 < length (cyclicPermutations l) := length_pos_of_ne_nil (cyclicPermutations_ne_nil _)
rw [← get_mk_zero h, get_cyclicPermutations, Fin.val_mk, rotate_zero]
|
/-
Copyright (c) 2021 Johan Commelin. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johan Commelin
-/
import Mathlib.Algebra.Polynomial.BigOperators
import Mathlib.Algebra.Polynomial.Derivative
import Mathlib.Data.Nat.Choose.Cast
import Mathlib.Data.Nat.Choose.Vandermonde
import Mathlib.Tactic.FieldSimp
#align_import data.polynomial.hasse_deriv from "leanprover-community/mathlib"@"a148d797a1094ab554ad4183a4ad6f130358ef64"
/-!
# Hasse derivative of polynomials
The `k`th Hasse derivative of a polynomial `∑ a_i X^i` is `∑ (i.choose k) a_i X^(i-k)`.
It is a variant of the usual derivative, and satisfies `k! * (hasseDeriv k f) = derivative^[k] f`.
The main benefit is that is gives an atomic way of talking about expressions such as
`(derivative^[k] f).eval r / k!`, that occur in Taylor expansions, for example.
## Main declarations
In the following, we write `D k` for the `k`-th Hasse derivative `hasse_deriv k`.
* `Polynomial.hasseDeriv`: the `k`-th Hasse derivative of a polynomial
* `Polynomial.hasseDeriv_zero`: the `0`th Hasse derivative is the identity
* `Polynomial.hasseDeriv_one`: the `1`st Hasse derivative is the usual derivative
* `Polynomial.factorial_smul_hasseDeriv`: the identity `k! • (D k f) = derivative^[k] f`
* `Polynomial.hasseDeriv_comp`: the identity `(D k).comp (D l) = (k+l).choose k • D (k+l)`
* `Polynomial.hasseDeriv_mul`:
the "Leibniz rule" `D k (f * g) = ∑ ij ∈ antidiagonal k, D ij.1 f * D ij.2 g`
For the identity principle, see `Polynomial.eq_zero_of_hasseDeriv_eq_zero`
in `Data/Polynomial/Taylor.lean`.
## Reference
https://math.fontein.de/2009/08/12/the-hasse-derivative/
-/
noncomputable section
namespace Polynomial
open Nat Polynomial
open Function
variable {R : Type*} [Semiring R] (k : ℕ) (f : R[X])
/-- The `k`th Hasse derivative of a polynomial `∑ a_i X^i` is `∑ (i.choose k) a_i X^(i-k)`.
It satisfies `k! * (hasse_deriv k f) = derivative^[k] f`. -/
def hasseDeriv (k : ℕ) : R[X] →ₗ[R] R[X] :=
lsum fun i => monomial (i - k) ∘ₗ DistribMulAction.toLinearMap R R (i.choose k)
#align polynomial.hasse_deriv Polynomial.hasseDeriv
theorem hasseDeriv_apply :
hasseDeriv k f = f.sum fun i r => monomial (i - k) (↑(i.choose k) * r) := by
dsimp [hasseDeriv]
congr; ext; congr
apply nsmul_eq_mul
#align polynomial.hasse_deriv_apply Polynomial.hasseDeriv_apply
theorem hasseDeriv_coeff (n : ℕ) :
(hasseDeriv k f).coeff n = (n + k).choose k * f.coeff (n + k) := by
rw [hasseDeriv_apply, coeff_sum, sum_def, Finset.sum_eq_single (n + k), coeff_monomial]
· simp only [if_true, add_tsub_cancel_right, eq_self_iff_true]
· intro i _hi hink
rw [coeff_monomial]
by_cases hik : i < k
· simp only [Nat.choose_eq_zero_of_lt hik, ite_self, Nat.cast_zero, zero_mul]
· push_neg at hik
rw [if_neg]
contrapose! hink
exact (tsub_eq_iff_eq_add_of_le hik).mp hink
· intro h
simp only [not_mem_support_iff.mp h, monomial_zero_right, mul_zero, coeff_zero]
#align polynomial.hasse_deriv_coeff Polynomial.hasseDeriv_coeff
theorem hasseDeriv_zero' : hasseDeriv 0 f = f := by
simp only [hasseDeriv_apply, tsub_zero, Nat.choose_zero_right, Nat.cast_one, one_mul,
sum_monomial_eq]
#align polynomial.hasse_deriv_zero' Polynomial.hasseDeriv_zero'
@[simp]
theorem hasseDeriv_zero : @hasseDeriv R _ 0 = LinearMap.id :=
LinearMap.ext <| hasseDeriv_zero'
#align polynomial.hasse_deriv_zero Polynomial.hasseDeriv_zero
theorem hasseDeriv_eq_zero_of_lt_natDegree (p : R[X]) (n : ℕ) (h : p.natDegree < n) :
hasseDeriv n p = 0 := by
rw [hasseDeriv_apply, sum_def]
refine Finset.sum_eq_zero fun x hx => ?_
simp [Nat.choose_eq_zero_of_lt ((le_natDegree_of_mem_supp _ hx).trans_lt h)]
#align polynomial.hasse_deriv_eq_zero_of_lt_nat_degree Polynomial.hasseDeriv_eq_zero_of_lt_natDegree
theorem hasseDeriv_one' : hasseDeriv 1 f = derivative f := by
simp only [hasseDeriv_apply, derivative_apply, ← C_mul_X_pow_eq_monomial, Nat.choose_one_right,
(Nat.cast_commute _ _).eq]
#align polynomial.hasse_deriv_one' Polynomial.hasseDeriv_one'
@[simp]
theorem hasseDeriv_one : @hasseDeriv R _ 1 = derivative :=
LinearMap.ext <| hasseDeriv_one'
#align polynomial.hasse_deriv_one Polynomial.hasseDeriv_one
@[simp]
theorem hasseDeriv_monomial (n : ℕ) (r : R) :
hasseDeriv k (monomial n r) = monomial (n - k) (↑(n.choose k) * r) := by
ext i
simp only [hasseDeriv_coeff, coeff_monomial]
by_cases hnik : n = i + k
· rw [if_pos hnik, if_pos, ← hnik]
apply tsub_eq_of_eq_add_rev
rwa [add_comm]
· rw [if_neg hnik, mul_zero]
by_cases hkn : k ≤ n
· rw [← tsub_eq_iff_eq_add_of_le hkn] at hnik
rw [if_neg hnik]
· push_neg at hkn
rw [Nat.choose_eq_zero_of_lt hkn, Nat.cast_zero, zero_mul, ite_self]
#align polynomial.hasse_deriv_monomial Polynomial.hasseDeriv_monomial
theorem hasseDeriv_C (r : R) (hk : 0 < k) : hasseDeriv k (C r) = 0 := by
rw [← monomial_zero_left, hasseDeriv_monomial, Nat.choose_eq_zero_of_lt hk, Nat.cast_zero,
zero_mul, monomial_zero_right]
set_option linter.uppercaseLean3 false in
#align polynomial.hasse_deriv_C Polynomial.hasseDeriv_C
theorem hasseDeriv_apply_one (hk : 0 < k) : hasseDeriv k (1 : R[X]) = 0 := by
rw [← C_1, hasseDeriv_C k _ hk]
#align polynomial.hasse_deriv_apply_one Polynomial.hasseDeriv_apply_one
theorem hasseDeriv_X (hk : 1 < k) : hasseDeriv k (X : R[X]) = 0 := by
rw [← monomial_one_one_eq_X, hasseDeriv_monomial, Nat.choose_eq_zero_of_lt hk, Nat.cast_zero,
zero_mul, monomial_zero_right]
set_option linter.uppercaseLean3 false in
#align polynomial.hasse_deriv_X Polynomial.hasseDeriv_X
theorem factorial_smul_hasseDeriv : ⇑(k ! • @hasseDeriv R _ k) = (@derivative R _)^[k] := by
induction' k with k ih
· rw [hasseDeriv_zero, factorial_zero, iterate_zero, one_smul, LinearMap.id_coe]
ext f n : 2
rw [iterate_succ_apply', ← ih]
simp only [LinearMap.smul_apply, coeff_smul, LinearMap.map_smul_of_tower, coeff_derivative,
hasseDeriv_coeff, ← @choose_symm_add _ k]
simp only [nsmul_eq_mul, factorial_succ, mul_assoc, succ_eq_add_one, ← add_assoc,
add_right_comm n 1 k, ← cast_succ]
rw [← (cast_commute (n + 1) (f.coeff (n + k + 1))).eq]
simp only [← mul_assoc]
norm_cast
congr 2
rw [mul_comm (k+1) _, mul_assoc, mul_assoc]
congr 1
have : n + k + 1 = n + (k + 1) := by apply add_assoc
rw [← choose_symm_of_eq_add this, choose_succ_right_eq, mul_comm]
congr
rw [add_assoc, add_tsub_cancel_left]
#align polynomial.factorial_smul_hasse_deriv Polynomial.factorial_smul_hasseDeriv
theorem hasseDeriv_comp (k l : ℕ) :
(@hasseDeriv R _ k).comp (hasseDeriv l) = (k + l).choose k • hasseDeriv (k + l) := by
ext i : 2
simp only [LinearMap.smul_apply, comp_apply, LinearMap.coe_comp, smul_monomial, hasseDeriv_apply,
mul_one, monomial_eq_zero_iff, sum_monomial_index, mul_zero, ←
tsub_add_eq_tsub_tsub, add_comm l k]
rw_mod_cast [nsmul_eq_mul]
rw [← Nat.cast_mul]
congr 2
by_cases hikl : i < k + l
· rw [choose_eq_zero_of_lt hikl, mul_zero]
by_cases hil : i < l
· rw [choose_eq_zero_of_lt hil, mul_zero]
· push_neg at hil
rw [← tsub_lt_iff_right hil] at hikl
rw [choose_eq_zero_of_lt hikl, zero_mul]
push_neg at hikl
apply @cast_injective ℚ
have h1 : l ≤ i := le_of_add_le_right hikl
have h2 : k ≤ i - l := le_tsub_of_add_le_right hikl
have h3 : k ≤ k + l := le_self_add
push_cast
rw [cast_choose ℚ h1, cast_choose ℚ h2, cast_choose ℚ h3, cast_choose ℚ hikl]
rw [show i - (k + l) = i - l - k by rw [add_comm]; apply tsub_add_eq_tsub_tsub]
simp only [add_tsub_cancel_left]
field_simp; ring
#align polynomial.hasse_deriv_comp Polynomial.hasseDeriv_comp
theorem natDegree_hasseDeriv_le (p : R[X]) (n : ℕ) :
natDegree (hasseDeriv n p) ≤ natDegree p - n := by
classical
rw [hasseDeriv_apply, sum_def]
refine (natDegree_sum_le _ _).trans ?_
simp_rw [Function.comp, natDegree_monomial]
rw [Finset.fold_ite, Finset.fold_const]
· simp only [ite_self, max_eq_right, zero_le', Finset.fold_max_le, true_and_iff, and_imp,
tsub_le_iff_right, mem_support_iff, Ne, Finset.mem_filter]
intro x hx hx'
have hxp : x ≤ p.natDegree := le_natDegree_of_ne_zero hx
have hxn : n ≤ x := by
contrapose! hx'
simp [Nat.choose_eq_zero_of_lt hx']
rwa [tsub_add_cancel_of_le (hxn.trans hxp)]
· simp
#align polynomial.nat_degree_hasse_deriv_le Polynomial.natDegree_hasseDeriv_le
theorem natDegree_hasseDeriv [NoZeroSMulDivisors ℕ R] (p : R[X]) (n : ℕ) :
natDegree (hasseDeriv n p) = natDegree p - n := by
cases' lt_or_le p.natDegree n with hn hn
· simpa [hasseDeriv_eq_zero_of_lt_natDegree, hn] using (tsub_eq_zero_of_le hn.le).symm
· refine map_natDegree_eq_sub ?_ ?_
· exact fun h => hasseDeriv_eq_zero_of_lt_natDegree _ _
· classical
simp only [ite_eq_right_iff, Ne, natDegree_monomial, hasseDeriv_monomial]
intro k c c0 hh
-- this is where we use the `smul_eq_zero` from `NoZeroSMulDivisors`
rw [← nsmul_eq_mul, smul_eq_zero, Nat.choose_eq_zero_iff] at hh
exact (tsub_eq_zero_of_le (Or.resolve_right hh c0).le).symm
#align polynomial.nat_degree_hasse_deriv Polynomial.natDegree_hasseDeriv
section
open AddMonoidHom Finset.Nat
open Finset (antidiagonal mem_antidiagonal)
| Mathlib/Algebra/Polynomial/HasseDeriv.lean | 230 | 264 | theorem hasseDeriv_mul (f g : R[X]) :
hasseDeriv k (f * g) = ∑ ij ∈ antidiagonal k, hasseDeriv ij.1 f * hasseDeriv ij.2 g := by |
let D k := (@hasseDeriv R _ k).toAddMonoidHom
let Φ := @AddMonoidHom.mul R[X] _
show
(compHom (D k)).comp Φ f g =
∑ ij ∈ antidiagonal k, ((compHom.comp ((compHom Φ) (D ij.1))).flip (D ij.2) f) g
simp only [← finset_sum_apply]
congr 2
clear f g
ext m r n s : 4
simp only [Φ, D, finset_sum_apply, coe_mulLeft, coe_comp, flip_apply, Function.comp_apply,
hasseDeriv_monomial, LinearMap.toAddMonoidHom_coe, compHom_apply_apply,
coe_mul, monomial_mul_monomial]
have aux :
∀ x : ℕ × ℕ,
x ∈ antidiagonal k →
monomial (m - x.1 + (n - x.2)) (↑(m.choose x.1) * r * (↑(n.choose x.2) * s)) =
monomial (m + n - k) (↑(m.choose x.1) * ↑(n.choose x.2) * (r * s)) := by
intro x hx
rw [mem_antidiagonal] at hx
subst hx
by_cases hm : m < x.1
· simp only [Nat.choose_eq_zero_of_lt hm, Nat.cast_zero, zero_mul,
monomial_zero_right]
by_cases hn : n < x.2
· simp only [Nat.choose_eq_zero_of_lt hn, Nat.cast_zero, zero_mul,
mul_zero, monomial_zero_right]
push_neg at hm hn
rw [tsub_add_eq_add_tsub hm, ← add_tsub_assoc_of_le hn, ← tsub_add_eq_tsub_tsub,
add_comm x.2 x.1, mul_assoc, ← mul_assoc r, ← (Nat.cast_commute _ r).eq, mul_assoc, mul_assoc]
rw [Finset.sum_congr rfl aux]
rw [← map_sum, ← Finset.sum_mul]
congr
rw_mod_cast [← Nat.add_choose_eq]
|
/-
Copyright (c) 2022 Yury G. Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury G. Kudryashov
-/
import Mathlib.Analysis.Asymptotics.Asymptotics
import Mathlib.Analysis.NormedSpace.Basic
#align_import analysis.asymptotics.theta from "leanprover-community/mathlib"@"f2ce6086713c78a7f880485f7917ea547a215982"
/-!
# Asymptotic equivalence up to a constant
In this file we define `Asymptotics.IsTheta l f g` (notation: `f =Θ[l] g`) as
`f =O[l] g ∧ g =O[l] f`, then prove basic properties of this equivalence relation.
-/
open Filter
open Topology
namespace Asymptotics
set_option linter.uppercaseLean3 false -- is_Theta
variable {α : Type*} {β : Type*} {E : Type*} {F : Type*} {G : Type*} {E' : Type*}
{F' : Type*} {G' : Type*} {E'' : Type*} {F'' : Type*} {G'' : Type*} {R : Type*}
{R' : Type*} {𝕜 : Type*} {𝕜' : Type*}
variable [Norm E] [Norm F] [Norm G]
variable [SeminormedAddCommGroup E'] [SeminormedAddCommGroup F'] [SeminormedAddCommGroup G']
[NormedAddCommGroup E''] [NormedAddCommGroup F''] [NormedAddCommGroup G''] [SeminormedRing R]
[SeminormedRing R']
variable [NormedField 𝕜] [NormedField 𝕜']
variable {c c' c₁ c₂ : ℝ} {f : α → E} {g : α → F} {k : α → G}
variable {f' : α → E'} {g' : α → F'} {k' : α → G'}
variable {f'' : α → E''} {g'' : α → F''}
variable {l l' : Filter α}
/-- We say that `f` is `Θ(g)` along a filter `l` (notation: `f =Θ[l] g`) if `f =O[l] g` and
`g =O[l] f`. -/
def IsTheta (l : Filter α) (f : α → E) (g : α → F) : Prop :=
IsBigO l f g ∧ IsBigO l g f
#align asymptotics.is_Theta Asymptotics.IsTheta
@[inherit_doc]
notation:100 f " =Θ[" l "] " g:100 => IsTheta l f g
theorem IsBigO.antisymm (h₁ : f =O[l] g) (h₂ : g =O[l] f) : f =Θ[l] g :=
⟨h₁, h₂⟩
#align asymptotics.is_O.antisymm Asymptotics.IsBigO.antisymm
lemma IsTheta.isBigO (h : f =Θ[l] g) : f =O[l] g := h.1
lemma IsTheta.isBigO_symm (h : f =Θ[l] g) : g =O[l] f := h.2
@[refl]
theorem isTheta_refl (f : α → E) (l : Filter α) : f =Θ[l] f :=
⟨isBigO_refl _ _, isBigO_refl _ _⟩
#align asymptotics.is_Theta_refl Asymptotics.isTheta_refl
theorem isTheta_rfl : f =Θ[l] f :=
isTheta_refl _ _
#align asymptotics.is_Theta_rfl Asymptotics.isTheta_rfl
@[symm]
nonrec theorem IsTheta.symm (h : f =Θ[l] g) : g =Θ[l] f :=
h.symm
#align asymptotics.is_Theta.symm Asymptotics.IsTheta.symm
theorem isTheta_comm : f =Θ[l] g ↔ g =Θ[l] f :=
⟨fun h ↦ h.symm, fun h ↦ h.symm⟩
#align asymptotics.is_Theta_comm Asymptotics.isTheta_comm
@[trans]
theorem IsTheta.trans {f : α → E} {g : α → F'} {k : α → G} (h₁ : f =Θ[l] g) (h₂ : g =Θ[l] k) :
f =Θ[l] k :=
⟨h₁.1.trans h₂.1, h₂.2.trans h₁.2⟩
#align asymptotics.is_Theta.trans Asymptotics.IsTheta.trans
-- Porting note (#10754): added instance
instance : Trans (α := α → E) (β := α → F') (γ := α → G) (IsTheta l) (IsTheta l) (IsTheta l) :=
⟨IsTheta.trans⟩
@[trans]
theorem IsBigO.trans_isTheta {f : α → E} {g : α → F'} {k : α → G} (h₁ : f =O[l] g)
(h₂ : g =Θ[l] k) : f =O[l] k :=
h₁.trans h₂.1
#align asymptotics.is_O.trans_is_Theta Asymptotics.IsBigO.trans_isTheta
-- Porting note (#10754): added instance
instance : Trans (α := α → E) (β := α → F') (γ := α → G) (IsBigO l) (IsTheta l) (IsBigO l) :=
⟨IsBigO.trans_isTheta⟩
@[trans]
theorem IsTheta.trans_isBigO {f : α → E} {g : α → F'} {k : α → G} (h₁ : f =Θ[l] g)
(h₂ : g =O[l] k) : f =O[l] k :=
h₁.1.trans h₂
#align asymptotics.is_Theta.trans_is_O Asymptotics.IsTheta.trans_isBigO
-- Porting note (#10754): added instance
instance : Trans (α := α → E) (β := α → F') (γ := α → G) (IsTheta l) (IsBigO l) (IsBigO l) :=
⟨IsTheta.trans_isBigO⟩
@[trans]
theorem IsLittleO.trans_isTheta {f : α → E} {g : α → F} {k : α → G'} (h₁ : f =o[l] g)
(h₂ : g =Θ[l] k) : f =o[l] k :=
h₁.trans_isBigO h₂.1
#align asymptotics.is_o.trans_is_Theta Asymptotics.IsLittleO.trans_isTheta
-- Porting note (#10754): added instance
instance : Trans (α := α → E) (β := α → F') (γ := α → G') (IsLittleO l) (IsTheta l) (IsLittleO l) :=
⟨IsLittleO.trans_isTheta⟩
@[trans]
theorem IsTheta.trans_isLittleO {f : α → E} {g : α → F'} {k : α → G} (h₁ : f =Θ[l] g)
(h₂ : g =o[l] k) : f =o[l] k :=
h₁.1.trans_isLittleO h₂
#align asymptotics.is_Theta.trans_is_o Asymptotics.IsTheta.trans_isLittleO
-- Porting note (#10754): added instance
instance : Trans (α := α → E) (β := α → F') (γ := α → G) (IsTheta l) (IsLittleO l) (IsLittleO l) :=
⟨IsTheta.trans_isLittleO⟩
@[trans]
theorem IsTheta.trans_eventuallyEq {f : α → E} {g₁ g₂ : α → F} (h : f =Θ[l] g₁) (hg : g₁ =ᶠ[l] g₂) :
f =Θ[l] g₂ :=
⟨h.1.trans_eventuallyEq hg, hg.symm.trans_isBigO h.2⟩
#align asymptotics.is_Theta.trans_eventually_eq Asymptotics.IsTheta.trans_eventuallyEq
-- Porting note (#10754): added instance
instance : Trans (α := α → E) (β := α → F) (γ := α → F) (IsTheta l) (EventuallyEq l) (IsTheta l) :=
⟨IsTheta.trans_eventuallyEq⟩
@[trans]
theorem _root_.Filter.EventuallyEq.trans_isTheta {f₁ f₂ : α → E} {g : α → F} (hf : f₁ =ᶠ[l] f₂)
(h : f₂ =Θ[l] g) : f₁ =Θ[l] g :=
⟨hf.trans_isBigO h.1, h.2.trans_eventuallyEq hf.symm⟩
#align filter.eventually_eq.trans_is_Theta Filter.EventuallyEq.trans_isTheta
-- Porting note (#10754): added instance
instance : Trans (α := α → E) (β := α → E) (γ := α → F) (EventuallyEq l) (IsTheta l) (IsTheta l) :=
⟨EventuallyEq.trans_isTheta⟩
lemma _root_.Filter.EventuallyEq.isTheta {f g : α → E} (h : f =ᶠ[l] g) : f =Θ[l] g :=
h.trans_isTheta isTheta_rfl
@[simp]
theorem isTheta_norm_left : (fun x ↦ ‖f' x‖) =Θ[l] g ↔ f' =Θ[l] g := by simp [IsTheta]
#align asymptotics.is_Theta_norm_left Asymptotics.isTheta_norm_left
@[simp]
| Mathlib/Analysis/Asymptotics/Theta.lean | 155 | 155 | theorem isTheta_norm_right : (f =Θ[l] fun x ↦ ‖g' x‖) ↔ f =Θ[l] g' := by | simp [IsTheta]
|
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Mario Carneiro, Yury Kudryashov
-/
import Mathlib.Topology.Order.IsLUB
/-!
# Order topology on a densely ordered set
-/
open Set Filter TopologicalSpace Topology Function
open OrderDual (toDual ofDual)
variable {α β γ : Type*}
section DenselyOrdered
variable [TopologicalSpace α] [LinearOrder α] [OrderTopology α] [DenselyOrdered α] {a b : α}
{s : Set α}
/-- The closure of the interval `(a, +∞)` is the closed interval `[a, +∞)`, unless `a` is a top
element. -/
theorem closure_Ioi' {a : α} (h : (Ioi a).Nonempty) : closure (Ioi a) = Ici a := by
apply Subset.antisymm
· exact closure_minimal Ioi_subset_Ici_self isClosed_Ici
· rw [← diff_subset_closure_iff, Ici_diff_Ioi_same, singleton_subset_iff]
exact isGLB_Ioi.mem_closure h
#align closure_Ioi' closure_Ioi'
/-- The closure of the interval `(a, +∞)` is the closed interval `[a, +∞)`. -/
@[simp]
theorem closure_Ioi (a : α) [NoMaxOrder α] : closure (Ioi a) = Ici a :=
closure_Ioi' nonempty_Ioi
#align closure_Ioi closure_Ioi
/-- The closure of the interval `(-∞, a)` is the closed interval `(-∞, a]`, unless `a` is a bottom
element. -/
theorem closure_Iio' (h : (Iio a).Nonempty) : closure (Iio a) = Iic a :=
closure_Ioi' (α := αᵒᵈ) h
#align closure_Iio' closure_Iio'
/-- The closure of the interval `(-∞, a)` is the interval `(-∞, a]`. -/
@[simp]
theorem closure_Iio (a : α) [NoMinOrder α] : closure (Iio a) = Iic a :=
closure_Iio' nonempty_Iio
#align closure_Iio closure_Iio
/-- The closure of the open interval `(a, b)` is the closed interval `[a, b]`. -/
@[simp]
theorem closure_Ioo {a b : α} (hab : a ≠ b) : closure (Ioo a b) = Icc a b := by
apply Subset.antisymm
· exact closure_minimal Ioo_subset_Icc_self isClosed_Icc
· cases' hab.lt_or_lt with hab hab
· rw [← diff_subset_closure_iff, Icc_diff_Ioo_same hab.le]
have hab' : (Ioo a b).Nonempty := nonempty_Ioo.2 hab
simp only [insert_subset_iff, singleton_subset_iff]
exact ⟨(isGLB_Ioo hab).mem_closure hab', (isLUB_Ioo hab).mem_closure hab'⟩
· rw [Icc_eq_empty_of_lt hab]
exact empty_subset _
#align closure_Ioo closure_Ioo
/-- The closure of the interval `(a, b]` is the closed interval `[a, b]`. -/
@[simp]
theorem closure_Ioc {a b : α} (hab : a ≠ b) : closure (Ioc a b) = Icc a b := by
apply Subset.antisymm
· exact closure_minimal Ioc_subset_Icc_self isClosed_Icc
· apply Subset.trans _ (closure_mono Ioo_subset_Ioc_self)
rw [closure_Ioo hab]
#align closure_Ioc closure_Ioc
/-- The closure of the interval `[a, b)` is the closed interval `[a, b]`. -/
@[simp]
theorem closure_Ico {a b : α} (hab : a ≠ b) : closure (Ico a b) = Icc a b := by
apply Subset.antisymm
· exact closure_minimal Ico_subset_Icc_self isClosed_Icc
· apply Subset.trans _ (closure_mono Ioo_subset_Ico_self)
rw [closure_Ioo hab]
#align closure_Ico closure_Ico
@[simp]
theorem interior_Ici' {a : α} (ha : (Iio a).Nonempty) : interior (Ici a) = Ioi a := by
rw [← compl_Iio, interior_compl, closure_Iio' ha, compl_Iic]
#align interior_Ici' interior_Ici'
theorem interior_Ici [NoMinOrder α] {a : α} : interior (Ici a) = Ioi a :=
interior_Ici' nonempty_Iio
#align interior_Ici interior_Ici
@[simp]
theorem interior_Iic' {a : α} (ha : (Ioi a).Nonempty) : interior (Iic a) = Iio a :=
interior_Ici' (α := αᵒᵈ) ha
#align interior_Iic' interior_Iic'
theorem interior_Iic [NoMaxOrder α] {a : α} : interior (Iic a) = Iio a :=
interior_Iic' nonempty_Ioi
#align interior_Iic interior_Iic
@[simp]
theorem interior_Icc [NoMinOrder α] [NoMaxOrder α] {a b : α} : interior (Icc a b) = Ioo a b := by
rw [← Ici_inter_Iic, interior_inter, interior_Ici, interior_Iic, Ioi_inter_Iio]
#align interior_Icc interior_Icc
@[simp]
theorem Icc_mem_nhds_iff [NoMinOrder α] [NoMaxOrder α] {a b x : α} :
Icc a b ∈ 𝓝 x ↔ x ∈ Ioo a b := by
rw [← interior_Icc, mem_interior_iff_mem_nhds]
@[simp]
theorem interior_Ico [NoMinOrder α] {a b : α} : interior (Ico a b) = Ioo a b := by
rw [← Ici_inter_Iio, interior_inter, interior_Ici, interior_Iio, Ioi_inter_Iio]
#align interior_Ico interior_Ico
@[simp]
theorem Ico_mem_nhds_iff [NoMinOrder α] {a b x : α} : Ico a b ∈ 𝓝 x ↔ x ∈ Ioo a b := by
rw [← interior_Ico, mem_interior_iff_mem_nhds]
@[simp]
theorem interior_Ioc [NoMaxOrder α] {a b : α} : interior (Ioc a b) = Ioo a b := by
rw [← Ioi_inter_Iic, interior_inter, interior_Ioi, interior_Iic, Ioi_inter_Iio]
#align interior_Ioc interior_Ioc
@[simp]
theorem Ioc_mem_nhds_iff [NoMaxOrder α] {a b x : α} : Ioc a b ∈ 𝓝 x ↔ x ∈ Ioo a b := by
rw [← interior_Ioc, mem_interior_iff_mem_nhds]
theorem closure_interior_Icc {a b : α} (h : a ≠ b) : closure (interior (Icc a b)) = Icc a b :=
(closure_minimal interior_subset isClosed_Icc).antisymm <|
calc
Icc a b = closure (Ioo a b) := (closure_Ioo h).symm
_ ⊆ closure (interior (Icc a b)) :=
closure_mono (interior_maximal Ioo_subset_Icc_self isOpen_Ioo)
#align closure_interior_Icc closure_interior_Icc
theorem Ioc_subset_closure_interior (a b : α) : Ioc a b ⊆ closure (interior (Ioc a b)) := by
rcases eq_or_ne a b with (rfl | h)
· simp
· calc
Ioc a b ⊆ Icc a b := Ioc_subset_Icc_self
_ = closure (Ioo a b) := (closure_Ioo h).symm
_ ⊆ closure (interior (Ioc a b)) :=
closure_mono (interior_maximal Ioo_subset_Ioc_self isOpen_Ioo)
#align Ioc_subset_closure_interior Ioc_subset_closure_interior
theorem Ico_subset_closure_interior (a b : α) : Ico a b ⊆ closure (interior (Ico a b)) := by
simpa only [dual_Ioc] using Ioc_subset_closure_interior (OrderDual.toDual b) (OrderDual.toDual a)
#align Ico_subset_closure_interior Ico_subset_closure_interior
@[simp]
theorem frontier_Ici' {a : α} (ha : (Iio a).Nonempty) : frontier (Ici a) = {a} := by
simp [frontier, ha]
#align frontier_Ici' frontier_Ici'
theorem frontier_Ici [NoMinOrder α] {a : α} : frontier (Ici a) = {a} :=
frontier_Ici' nonempty_Iio
#align frontier_Ici frontier_Ici
@[simp]
theorem frontier_Iic' {a : α} (ha : (Ioi a).Nonempty) : frontier (Iic a) = {a} := by
simp [frontier, ha]
#align frontier_Iic' frontier_Iic'
theorem frontier_Iic [NoMaxOrder α] {a : α} : frontier (Iic a) = {a} :=
frontier_Iic' nonempty_Ioi
#align frontier_Iic frontier_Iic
@[simp]
theorem frontier_Ioi' {a : α} (ha : (Ioi a).Nonempty) : frontier (Ioi a) = {a} := by
simp [frontier, closure_Ioi' ha, Iic_diff_Iio, Icc_self]
#align frontier_Ioi' frontier_Ioi'
theorem frontier_Ioi [NoMaxOrder α] {a : α} : frontier (Ioi a) = {a} :=
frontier_Ioi' nonempty_Ioi
#align frontier_Ioi frontier_Ioi
@[simp]
theorem frontier_Iio' {a : α} (ha : (Iio a).Nonempty) : frontier (Iio a) = {a} := by
simp [frontier, closure_Iio' ha, Iic_diff_Iio, Icc_self]
#align frontier_Iio' frontier_Iio'
theorem frontier_Iio [NoMinOrder α] {a : α} : frontier (Iio a) = {a} :=
frontier_Iio' nonempty_Iio
#align frontier_Iio frontier_Iio
@[simp]
theorem frontier_Icc [NoMinOrder α] [NoMaxOrder α] {a b : α} (h : a ≤ b) :
frontier (Icc a b) = {a, b} := by simp [frontier, h, Icc_diff_Ioo_same]
#align frontier_Icc frontier_Icc
@[simp]
theorem frontier_Ioo {a b : α} (h : a < b) : frontier (Ioo a b) = {a, b} := by
rw [frontier, closure_Ioo h.ne, interior_Ioo, Icc_diff_Ioo_same h.le]
#align frontier_Ioo frontier_Ioo
@[simp]
theorem frontier_Ico [NoMinOrder α] {a b : α} (h : a < b) : frontier (Ico a b) = {a, b} := by
rw [frontier, closure_Ico h.ne, interior_Ico, Icc_diff_Ioo_same h.le]
#align frontier_Ico frontier_Ico
@[simp]
theorem frontier_Ioc [NoMaxOrder α] {a b : α} (h : a < b) : frontier (Ioc a b) = {a, b} := by
rw [frontier, closure_Ioc h.ne, interior_Ioc, Icc_diff_Ioo_same h.le]
#align frontier_Ioc frontier_Ioc
theorem nhdsWithin_Ioi_neBot' {a b : α} (H₁ : (Ioi a).Nonempty) (H₂ : a ≤ b) :
NeBot (𝓝[Ioi a] b) :=
mem_closure_iff_nhdsWithin_neBot.1 <| by rwa [closure_Ioi' H₁]
#align nhds_within_Ioi_ne_bot' nhdsWithin_Ioi_neBot'
theorem nhdsWithin_Ioi_neBot [NoMaxOrder α] {a b : α} (H : a ≤ b) : NeBot (𝓝[Ioi a] b) :=
nhdsWithin_Ioi_neBot' nonempty_Ioi H
#align nhds_within_Ioi_ne_bot nhdsWithin_Ioi_neBot
theorem nhdsWithin_Ioi_self_neBot' {a : α} (H : (Ioi a).Nonempty) : NeBot (𝓝[>] a) :=
nhdsWithin_Ioi_neBot' H (le_refl a)
#align nhds_within_Ioi_self_ne_bot' nhdsWithin_Ioi_self_neBot'
instance nhdsWithin_Ioi_self_neBot [NoMaxOrder α] (a : α) : NeBot (𝓝[>] a) :=
nhdsWithin_Ioi_neBot (le_refl a)
#align nhds_within_Ioi_self_ne_bot nhdsWithin_Ioi_self_neBot
theorem nhdsWithin_Iio_neBot' {b c : α} (H₁ : (Iio c).Nonempty) (H₂ : b ≤ c) :
NeBot (𝓝[Iio c] b) :=
mem_closure_iff_nhdsWithin_neBot.1 <| by rwa [closure_Iio' H₁]
#align nhds_within_Iio_ne_bot' nhdsWithin_Iio_neBot'
theorem nhdsWithin_Iio_neBot [NoMinOrder α] {a b : α} (H : a ≤ b) : NeBot (𝓝[Iio b] a) :=
nhdsWithin_Iio_neBot' nonempty_Iio H
#align nhds_within_Iio_ne_bot nhdsWithin_Iio_neBot
theorem nhdsWithin_Iio_self_neBot' {b : α} (H : (Iio b).Nonempty) : NeBot (𝓝[<] b) :=
nhdsWithin_Iio_neBot' H (le_refl b)
#align nhds_within_Iio_self_ne_bot' nhdsWithin_Iio_self_neBot'
instance nhdsWithin_Iio_self_neBot [NoMinOrder α] (a : α) : NeBot (𝓝[<] a) :=
nhdsWithin_Iio_neBot (le_refl a)
#align nhds_within_Iio_self_ne_bot nhdsWithin_Iio_self_neBot
theorem right_nhdsWithin_Ico_neBot {a b : α} (H : a < b) : NeBot (𝓝[Ico a b] b) :=
(isLUB_Ico H).nhdsWithin_neBot (nonempty_Ico.2 H)
#align right_nhds_within_Ico_ne_bot right_nhdsWithin_Ico_neBot
theorem left_nhdsWithin_Ioc_neBot {a b : α} (H : a < b) : NeBot (𝓝[Ioc a b] a) :=
(isGLB_Ioc H).nhdsWithin_neBot (nonempty_Ioc.2 H)
#align left_nhds_within_Ioc_ne_bot left_nhdsWithin_Ioc_neBot
theorem left_nhdsWithin_Ioo_neBot {a b : α} (H : a < b) : NeBot (𝓝[Ioo a b] a) :=
(isGLB_Ioo H).nhdsWithin_neBot (nonempty_Ioo.2 H)
#align left_nhds_within_Ioo_ne_bot left_nhdsWithin_Ioo_neBot
theorem right_nhdsWithin_Ioo_neBot {a b : α} (H : a < b) : NeBot (𝓝[Ioo a b] b) :=
(isLUB_Ioo H).nhdsWithin_neBot (nonempty_Ioo.2 H)
#align right_nhds_within_Ioo_ne_bot right_nhdsWithin_Ioo_neBot
theorem comap_coe_nhdsWithin_Iio_of_Ioo_subset (hb : s ⊆ Iio b)
(hs : s.Nonempty → ∃ a < b, Ioo a b ⊆ s) : comap ((↑) : s → α) (𝓝[<] b) = atTop := by
nontriviality
haveI : Nonempty s := nontrivial_iff_nonempty.1 ‹_›
rcases hs (nonempty_subtype.1 ‹_›) with ⟨a, h, hs⟩
ext u; constructor
· rintro ⟨t, ht, hts⟩
obtain ⟨x, ⟨hxa : a ≤ x, hxb : x < b⟩, hxt : Ioo x b ⊆ t⟩ :=
(mem_nhdsWithin_Iio_iff_exists_mem_Ico_Ioo_subset h).mp ht
obtain ⟨y, hxy, hyb⟩ := exists_between hxb
refine mem_of_superset (mem_atTop ⟨y, hs ⟨hxa.trans_lt hxy, hyb⟩⟩) ?_
rintro ⟨z, hzs⟩ (hyz : y ≤ z)
exact hts (hxt ⟨hxy.trans_le hyz, hb hzs⟩)
· intro hu
obtain ⟨x : s, hx : ∀ z, x ≤ z → z ∈ u⟩ := mem_atTop_sets.1 hu
exact ⟨Ioo x b, Ioo_mem_nhdsWithin_Iio' (hb x.2), fun z hz => hx _ hz.1.le⟩
#align comap_coe_nhds_within_Iio_of_Ioo_subset comap_coe_nhdsWithin_Iio_of_Ioo_subset
set_option backward.isDefEq.lazyWhnfCore false in -- See https://github.com/leanprover-community/mathlib4/issues/12534
theorem comap_coe_nhdsWithin_Ioi_of_Ioo_subset (ha : s ⊆ Ioi a)
(hs : s.Nonempty → ∃ b > a, Ioo a b ⊆ s) : comap ((↑) : s → α) (𝓝[>] a) = atBot :=
comap_coe_nhdsWithin_Iio_of_Ioo_subset (show ofDual ⁻¹' s ⊆ Iio (toDual a) from ha) fun h => by
simpa only [OrderDual.exists, dual_Ioo] using hs h
#align comap_coe_nhds_within_Ioi_of_Ioo_subset comap_coe_nhdsWithin_Ioi_of_Ioo_subset
theorem map_coe_atTop_of_Ioo_subset (hb : s ⊆ Iio b) (hs : ∀ a' < b, ∃ a < b, Ioo a b ⊆ s) :
map ((↑) : s → α) atTop = 𝓝[<] b := by
rcases eq_empty_or_nonempty (Iio b) with (hb' | ⟨a, ha⟩)
· have : IsEmpty s := ⟨fun x => hb'.subset (hb x.2)⟩
rw [filter_eq_bot_of_isEmpty atTop, Filter.map_bot, hb', nhdsWithin_empty]
· rw [← comap_coe_nhdsWithin_Iio_of_Ioo_subset hb fun _ => hs a ha, map_comap_of_mem]
rw [Subtype.range_val]
exact (mem_nhdsWithin_Iio_iff_exists_Ioo_subset' ha).2 (hs a ha)
#align map_coe_at_top_of_Ioo_subset map_coe_atTop_of_Ioo_subset
theorem map_coe_atBot_of_Ioo_subset (ha : s ⊆ Ioi a) (hs : ∀ b' > a, ∃ b > a, Ioo a b ⊆ s) :
map ((↑) : s → α) atBot = 𝓝[>] a := by
-- the elaborator gets stuck without `(... : _)`
refine (map_coe_atTop_of_Ioo_subset (show ofDual ⁻¹' s ⊆ Iio (toDual a) from ha)
fun b' hb' => ?_ : _)
simpa only [OrderDual.exists, dual_Ioo] using hs b' hb'
#align map_coe_at_bot_of_Ioo_subset map_coe_atBot_of_Ioo_subset
/-- The `atTop` filter for an open interval `Ioo a b` comes from the left-neighbourhoods filter at
the right endpoint in the ambient order. -/
theorem comap_coe_Ioo_nhdsWithin_Iio (a b : α) : comap ((↑) : Ioo a b → α) (𝓝[<] b) = atTop :=
comap_coe_nhdsWithin_Iio_of_Ioo_subset Ioo_subset_Iio_self fun h =>
⟨a, nonempty_Ioo.1 h, Subset.refl _⟩
#align comap_coe_Ioo_nhds_within_Iio comap_coe_Ioo_nhdsWithin_Iio
/-- The `atBot` filter for an open interval `Ioo a b` comes from the right-neighbourhoods filter at
the left endpoint in the ambient order. -/
theorem comap_coe_Ioo_nhdsWithin_Ioi (a b : α) : comap ((↑) : Ioo a b → α) (𝓝[>] a) = atBot :=
comap_coe_nhdsWithin_Ioi_of_Ioo_subset Ioo_subset_Ioi_self fun h =>
⟨b, nonempty_Ioo.1 h, Subset.refl _⟩
#align comap_coe_Ioo_nhds_within_Ioi comap_coe_Ioo_nhdsWithin_Ioi
theorem comap_coe_Ioi_nhdsWithin_Ioi (a : α) : comap ((↑) : Ioi a → α) (𝓝[>] a) = atBot :=
comap_coe_nhdsWithin_Ioi_of_Ioo_subset (Subset.refl _) fun ⟨x, hx⟩ => ⟨x, hx, Ioo_subset_Ioi_self⟩
#align comap_coe_Ioi_nhds_within_Ioi comap_coe_Ioi_nhdsWithin_Ioi
theorem comap_coe_Iio_nhdsWithin_Iio (a : α) : comap ((↑) : Iio a → α) (𝓝[<] a) = atTop :=
comap_coe_Ioi_nhdsWithin_Ioi (α := αᵒᵈ) a
#align comap_coe_Iio_nhds_within_Iio comap_coe_Iio_nhdsWithin_Iio
@[simp]
theorem map_coe_Ioo_atTop {a b : α} (h : a < b) : map ((↑) : Ioo a b → α) atTop = 𝓝[<] b :=
map_coe_atTop_of_Ioo_subset Ioo_subset_Iio_self fun _ _ => ⟨_, h, Subset.refl _⟩
#align map_coe_Ioo_at_top map_coe_Ioo_atTop
@[simp]
theorem map_coe_Ioo_atBot {a b : α} (h : a < b) : map ((↑) : Ioo a b → α) atBot = 𝓝[>] a :=
map_coe_atBot_of_Ioo_subset Ioo_subset_Ioi_self fun _ _ => ⟨_, h, Subset.refl _⟩
#align map_coe_Ioo_at_bot map_coe_Ioo_atBot
@[simp]
theorem map_coe_Ioi_atBot (a : α) : map ((↑) : Ioi a → α) atBot = 𝓝[>] a :=
map_coe_atBot_of_Ioo_subset (Subset.refl _) fun b hb => ⟨b, hb, Ioo_subset_Ioi_self⟩
#align map_coe_Ioi_at_bot map_coe_Ioi_atBot
@[simp]
theorem map_coe_Iio_atTop (a : α) : map ((↑) : Iio a → α) atTop = 𝓝[<] a :=
map_coe_Ioi_atBot (α := αᵒᵈ) _
#align map_coe_Iio_at_top map_coe_Iio_atTop
variable {l : Filter β} {f : α → β}
@[simp]
theorem tendsto_comp_coe_Ioo_atTop (h : a < b) :
Tendsto (fun x : Ioo a b => f x) atTop l ↔ Tendsto f (𝓝[<] b) l := by
rw [← map_coe_Ioo_atTop h, tendsto_map'_iff]; rfl
#align tendsto_comp_coe_Ioo_at_top tendsto_comp_coe_Ioo_atTop
@[simp]
theorem tendsto_comp_coe_Ioo_atBot (h : a < b) :
Tendsto (fun x : Ioo a b => f x) atBot l ↔ Tendsto f (𝓝[>] a) l := by
rw [← map_coe_Ioo_atBot h, tendsto_map'_iff]; rfl
#align tendsto_comp_coe_Ioo_at_bot tendsto_comp_coe_Ioo_atBot
-- Porting note (#11215): TODO: `simpNF` claims that `simp` can't use
-- this lemma to simplify LHS but it can
@[simp, nolint simpNF]
theorem tendsto_comp_coe_Ioi_atBot :
Tendsto (fun x : Ioi a => f x) atBot l ↔ Tendsto f (𝓝[>] a) l := by
rw [← map_coe_Ioi_atBot, tendsto_map'_iff]; rfl
#align tendsto_comp_coe_Ioi_at_bot tendsto_comp_coe_Ioi_atBot
-- Porting note (#11215): TODO: `simpNF` claims that `simp` can't use
-- this lemma to simplify LHS but it can
@[simp, nolint simpNF]
theorem tendsto_comp_coe_Iio_atTop :
Tendsto (fun x : Iio a => f x) atTop l ↔ Tendsto f (𝓝[<] a) l := by
rw [← map_coe_Iio_atTop, tendsto_map'_iff]; rfl
#align tendsto_comp_coe_Iio_at_top tendsto_comp_coe_Iio_atTop
@[simp]
theorem tendsto_Ioo_atTop {f : β → Ioo a b} :
Tendsto f l atTop ↔ Tendsto (fun x => (f x : α)) l (𝓝[<] b) := by
rw [← comap_coe_Ioo_nhdsWithin_Iio, tendsto_comap_iff]; rfl
#align tendsto_Ioo_at_top tendsto_Ioo_atTop
@[simp]
theorem tendsto_Ioo_atBot {f : β → Ioo a b} :
Tendsto f l atBot ↔ Tendsto (fun x => (f x : α)) l (𝓝[>] a) := by
rw [← comap_coe_Ioo_nhdsWithin_Ioi, tendsto_comap_iff]; rfl
#align tendsto_Ioo_at_bot tendsto_Ioo_atBot
@[simp]
theorem tendsto_Ioi_atBot {f : β → Ioi a} :
Tendsto f l atBot ↔ Tendsto (fun x => (f x : α)) l (𝓝[>] a) := by
rw [← comap_coe_Ioi_nhdsWithin_Ioi, tendsto_comap_iff]; rfl
#align tendsto_Ioi_at_bot tendsto_Ioi_atBot
@[simp]
theorem tendsto_Iio_atTop {f : β → Iio a} :
Tendsto f l atTop ↔ Tendsto (fun x => (f x : α)) l (𝓝[<] a) := by
rw [← comap_coe_Iio_nhdsWithin_Iio, tendsto_comap_iff]; rfl
#align tendsto_Iio_at_top tendsto_Iio_atTop
instance (x : α) [Nontrivial α] : NeBot (𝓝[≠] x) := by
refine forall_mem_nonempty_iff_neBot.1 fun s hs => ?_
obtain ⟨u, u_open, xu, us⟩ : ∃ u : Set α, IsOpen u ∧ x ∈ u ∧ u ∩ {x}ᶜ ⊆ s := mem_nhdsWithin.1 hs
obtain ⟨a, b, a_lt_b, hab⟩ : ∃ a b : α, a < b ∧ Ioo a b ⊆ u := u_open.exists_Ioo_subset ⟨x, xu⟩
obtain ⟨y, hy⟩ : ∃ y, a < y ∧ y < b := exists_between a_lt_b
rcases ne_or_eq x y with (xy | rfl)
· exact ⟨y, us ⟨hab hy, xy.symm⟩⟩
obtain ⟨z, hz⟩ : ∃ z, a < z ∧ z < x := exists_between hy.1
exact ⟨z, us ⟨hab ⟨hz.1, hz.2.trans hy.2⟩, hz.2.ne⟩⟩
/-- Let `s` be a dense set in a nontrivial dense linear order `α`. If `s` is a
separable space (e.g., if `α` has a second countable topology), then there exists a countable
dense subset `t ⊆ s` such that `t` does not contain bottom/top elements of `α`. -/
| Mathlib/Topology/Order/DenselyOrdered.lean | 408 | 417 | theorem Dense.exists_countable_dense_subset_no_bot_top [Nontrivial α] {s : Set α} [SeparableSpace s]
(hs : Dense s) :
∃ t, t ⊆ s ∧ t.Countable ∧ Dense t ∧ (∀ x, IsBot x → x ∉ t) ∧ ∀ x, IsTop x → x ∉ t := by |
rcases hs.exists_countable_dense_subset with ⟨t, hts, htc, htd⟩
refine ⟨t \ ({ x | IsBot x } ∪ { x | IsTop x }), ?_, ?_, ?_, fun x hx => ?_, fun x hx => ?_⟩
· exact diff_subset.trans hts
· exact htc.mono diff_subset
· exact htd.diff_finite ((subsingleton_isBot α).finite.union (subsingleton_isTop α).finite)
· simp [hx]
· simp [hx]
|
/-
Copyright (c) 2022 Pim Otte. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kyle Miller, Pim Otte
-/
import Mathlib.Algebra.BigOperators.Fin
import Mathlib.Data.Nat.Choose.Sum
import Mathlib.Data.Nat.Factorial.BigOperators
import Mathlib.Data.Fin.VecNotation
import Mathlib.Data.Finset.Sym
import Mathlib.Data.Finsupp.Multiset
#align_import data.nat.choose.multinomial from "leanprover-community/mathlib"@"2738d2ca56cbc63be80c3bd48e9ed90ad94e947d"
/-!
# Multinomial
This file defines the multinomial coefficient and several small lemma's for manipulating it.
## Main declarations
- `Nat.multinomial`: the multinomial coefficient
## Main results
- `Finset.sum_pow`: The expansion of `(s.sum x) ^ n` using multinomial coefficients
-/
open Finset
open scoped Nat
namespace Nat
variable {α : Type*} (s : Finset α) (f : α → ℕ) {a b : α} (n : ℕ)
/-- The multinomial coefficient. Gives the number of strings consisting of symbols
from `s`, where `c ∈ s` appears with multiplicity `f c`.
Defined as `(∑ i ∈ s, f i)! / ∏ i ∈ s, (f i)!`.
-/
def multinomial : ℕ :=
(∑ i ∈ s, f i)! / ∏ i ∈ s, (f i)!
#align nat.multinomial Nat.multinomial
theorem multinomial_pos : 0 < multinomial s f :=
Nat.div_pos (le_of_dvd (factorial_pos _) (prod_factorial_dvd_factorial_sum s f))
(prod_factorial_pos s f)
#align nat.multinomial_pos Nat.multinomial_pos
theorem multinomial_spec : (∏ i ∈ s, (f i)!) * multinomial s f = (∑ i ∈ s, f i)! :=
Nat.mul_div_cancel' (prod_factorial_dvd_factorial_sum s f)
#align nat.multinomial_spec Nat.multinomial_spec
@[simp] lemma multinomial_empty : multinomial ∅ f = 1 := by simp [multinomial]
#align nat.multinomial_nil Nat.multinomial_empty
@[deprecated (since := "2024-06-01")] alias multinomial_nil := multinomial_empty
variable {s f}
lemma multinomial_cons (ha : a ∉ s) (f : α → ℕ) :
multinomial (s.cons a ha) f = (f a + ∑ i ∈ s, f i).choose (f a) * multinomial s f := by
rw [multinomial, Nat.div_eq_iff_eq_mul_left _ (prod_factorial_dvd_factorial_sum _ _), prod_cons,
multinomial, mul_assoc, mul_left_comm _ (f a)!,
Nat.div_mul_cancel (prod_factorial_dvd_factorial_sum _ _), ← mul_assoc, Nat.choose_symm_add,
Nat.add_choose_mul_factorial_mul_factorial, Finset.sum_cons]
positivity
lemma multinomial_insert [DecidableEq α] (ha : a ∉ s) (f : α → ℕ) :
multinomial (insert a s) f = (f a + ∑ i ∈ s, f i).choose (f a) * multinomial s f := by
rw [← cons_eq_insert _ _ ha, multinomial_cons]
#align nat.multinomial_insert Nat.multinomial_insert
@[simp] lemma multinomial_singleton (a : α) (f : α → ℕ) : multinomial {a} f = 1 := by
rw [← cons_empty, multinomial_cons]; simp
#align nat.multinomial_singleton Nat.multinomial_singleton
@[simp]
theorem multinomial_insert_one [DecidableEq α] (h : a ∉ s) (h₁ : f a = 1) :
multinomial (insert a s) f = (s.sum f).succ * multinomial s f := by
simp only [multinomial, one_mul, factorial]
rw [Finset.sum_insert h, Finset.prod_insert h, h₁, add_comm, ← succ_eq_add_one, factorial_succ]
simp only [factorial_one, one_mul, Function.comp_apply, factorial, mul_one, ← one_eq_succ_zero]
rw [Nat.mul_div_assoc _ (prod_factorial_dvd_factorial_sum _ _)]
#align nat.multinomial_insert_one Nat.multinomial_insert_one
theorem multinomial_congr {f g : α → ℕ} (h : ∀ a ∈ s, f a = g a) :
multinomial s f = multinomial s g := by
simp only [multinomial]; congr 1
· rw [Finset.sum_congr rfl h]
· exact Finset.prod_congr rfl fun a ha => by rw [h a ha]
#align nat.multinomial_congr Nat.multinomial_congr
/-! ### Connection to binomial coefficients
When `Nat.multinomial` is applied to a `Finset` of two elements `{a, b}`, the
result a binomial coefficient. We use `binomial` in the names of lemmas that
involves `Nat.multinomial {a, b}`.
-/
theorem binomial_eq [DecidableEq α] (h : a ≠ b) :
multinomial {a, b} f = (f a + f b)! / ((f a)! * (f b)!) := by
simp [multinomial, Finset.sum_pair h, Finset.prod_pair h]
#align nat.binomial_eq Nat.binomial_eq
theorem binomial_eq_choose [DecidableEq α] (h : a ≠ b) :
multinomial {a, b} f = (f a + f b).choose (f a) := by
simp [binomial_eq h, choose_eq_factorial_div_factorial (Nat.le_add_right _ _)]
#align nat.binomial_eq_choose Nat.binomial_eq_choose
theorem binomial_spec [DecidableEq α] (hab : a ≠ b) :
(f a)! * (f b)! * multinomial {a, b} f = (f a + f b)! := by
simpa [Finset.sum_pair hab, Finset.prod_pair hab] using multinomial_spec {a, b} f
#align nat.binomial_spec Nat.binomial_spec
@[simp]
theorem binomial_one [DecidableEq α] (h : a ≠ b) (h₁ : f a = 1) :
multinomial {a, b} f = (f b).succ := by
simp [multinomial_insert_one (Finset.not_mem_singleton.mpr h) h₁]
#align nat.binomial_one Nat.binomial_one
theorem binomial_succ_succ [DecidableEq α] (h : a ≠ b) :
multinomial {a, b} (Function.update (Function.update f a (f a).succ) b (f b).succ) =
multinomial {a, b} (Function.update f a (f a).succ) +
multinomial {a, b} (Function.update f b (f b).succ) := by
simp only [binomial_eq_choose, Function.update_apply,
h, Ne, ite_true, ite_false, not_false_eq_true]
rw [if_neg h.symm]
rw [add_succ, choose_succ_succ, succ_add_eq_add_succ]
ring
#align nat.binomial_succ_succ Nat.binomial_succ_succ
theorem succ_mul_binomial [DecidableEq α] (h : a ≠ b) :
(f a + f b).succ * multinomial {a, b} f =
(f a).succ * multinomial {a, b} (Function.update f a (f a).succ) := by
rw [binomial_eq_choose h, binomial_eq_choose h, mul_comm (f a).succ, Function.update_same,
Function.update_noteq (ne_comm.mp h)]
rw [succ_mul_choose_eq (f a + f b) (f a), succ_add (f a) (f b)]
#align nat.succ_mul_binomial Nat.succ_mul_binomial
/-! ### Simple cases -/
theorem multinomial_univ_two (a b : ℕ) :
multinomial Finset.univ ![a, b] = (a + b)! / (a ! * b !) := by
rw [multinomial, Fin.sum_univ_two, Fin.prod_univ_two, Matrix.cons_val_zero, Matrix.cons_val_one,
Matrix.head_cons]
#align nat.multinomial_univ_two Nat.multinomial_univ_two
theorem multinomial_univ_three (a b c : ℕ) :
multinomial Finset.univ ![a, b, c] = (a + b + c)! / (a ! * b ! * c !) := by
rw [multinomial, Fin.sum_univ_three, Fin.prod_univ_three]
rfl
#align nat.multinomial_univ_three Nat.multinomial_univ_three
end Nat
/-! ### Alternative definitions -/
namespace Finsupp
variable {α : Type*}
/-- Alternative multinomial definition based on a finsupp, using the support
for the big operations
-/
def multinomial (f : α →₀ ℕ) : ℕ :=
(f.sum fun _ => id)! / f.prod fun _ n => n !
#align finsupp.multinomial Finsupp.multinomial
theorem multinomial_eq (f : α →₀ ℕ) : f.multinomial = Nat.multinomial f.support f :=
rfl
#align finsupp.multinomial_eq Finsupp.multinomial_eq
theorem multinomial_update (a : α) (f : α →₀ ℕ) :
f.multinomial = (f.sum fun _ => id).choose (f a) * (f.update a 0).multinomial := by
simp only [multinomial_eq]
classical
by_cases h : a ∈ f.support
· rw [← Finset.insert_erase h, Nat.multinomial_insert (Finset.not_mem_erase a _),
Finset.add_sum_erase _ f h, support_update_zero]
congr 1
exact Nat.multinomial_congr fun _ h ↦ (Function.update_noteq (mem_erase.1 h).1 0 f).symm
rw [not_mem_support_iff] at h
rw [h, Nat.choose_zero_right, one_mul, ← h, update_self]
#align finsupp.multinomial_update Finsupp.multinomial_update
end Finsupp
namespace Multiset
variable {α : Type*}
/-- Alternative definition of multinomial based on `Multiset` delegating to the
finsupp definition
-/
def multinomial [DecidableEq α] (m : Multiset α) : ℕ :=
m.toFinsupp.multinomial
#align multiset.multinomial Multiset.multinomial
theorem multinomial_filter_ne [DecidableEq α] (a : α) (m : Multiset α) :
m.multinomial = m.card.choose (m.count a) * (m.filter (a ≠ ·)).multinomial := by
dsimp only [multinomial]
convert Finsupp.multinomial_update a _
· rw [← Finsupp.card_toMultiset, m.toFinsupp_toMultiset]
· ext1 a
rw [toFinsupp_apply, count_filter, Finsupp.coe_update]
split_ifs with h
· rw [Function.update_noteq h.symm, toFinsupp_apply]
· rw [not_ne_iff.1 h, Function.update_same]
#align multiset.multinomial_filter_ne Multiset.multinomial_filter_ne
@[simp]
theorem multinomial_zero [DecidableEq α] : multinomial (0 : Multiset α) = 1 := by
simp [multinomial, Finsupp.multinomial]
end Multiset
namespace Finset
/-! ### Multinomial theorem -/
variable {α : Type*} [DecidableEq α] (s : Finset α) {R : Type*}
/-- The multinomial theorem
Proof is by induction on the number of summands.
-/
| Mathlib/Data/Nat/Choose/Multinomial.lean | 231 | 267 | theorem sum_pow_of_commute [Semiring R] (x : α → R)
(hc : (s : Set α).Pairwise fun i j => Commute (x i) (x j)) :
∀ n,
s.sum x ^ n =
∑ k : s.sym n,
k.1.1.multinomial *
(k.1.1.map <| x).noncommProd
(Multiset.map_set_pairwise <| hc.mono <| mem_sym_iff.1 k.2) := by |
induction' s using Finset.induction with a s ha ih
· rw [sum_empty]
rintro (_ | n)
-- Porting note: Lean cannot infer this instance by itself
· haveI : Subsingleton (Sym α 0) := Unique.instSubsingleton
rw [_root_.pow_zero, Fintype.sum_subsingleton]
swap
-- Porting note: Lean cannot infer this instance by itself
· have : Zero (Sym α 0) := Sym.instZeroSym
exact ⟨0, by simp [eq_iff_true_of_subsingleton]⟩
convert (@one_mul R _ _).symm
convert @Nat.cast_one R _
simp
· rw [_root_.pow_succ, mul_zero]
-- Porting note: Lean cannot infer this instance by itself
haveI : IsEmpty (Finset.sym (∅ : Finset α) n.succ) := Finset.instIsEmpty
apply (Fintype.sum_empty _).symm
intro n; specialize ih (hc.mono <| s.subset_insert a)
rw [sum_insert ha, (Commute.sum_right s _ _ _).add_pow, sum_range]; swap
· exact fun _ hb => hc (mem_insert_self a s) (mem_insert_of_mem hb)
(ne_of_mem_of_not_mem hb ha).symm
· simp_rw [ih, mul_sum, sum_mul, sum_sigma', univ_sigma_univ]
refine (Fintype.sum_equiv (symInsertEquiv ha) _ _ fun m => ?_).symm
rw [m.1.1.multinomial_filter_ne a]
conv in m.1.1.map _ => rw [← m.1.1.filter_add_not (a = ·), Multiset.map_add]
simp_rw [Multiset.noncommProd_add, m.1.1.filter_eq, Multiset.map_replicate, m.1.2]
rw [Multiset.noncommProd_eq_pow_card _ _ _ fun _ => Multiset.eq_of_mem_replicate]
rw [Multiset.card_replicate, Nat.cast_mul, mul_assoc, Nat.cast_comm]
congr 1; simp_rw [← mul_assoc, Nat.cast_comm]; rfl
|
/-
Copyright (c) 2024 Jz Pan. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jz Pan
-/
import Mathlib.FieldTheory.SeparableClosure
import Mathlib.Algebra.CharP.IntermediateField
/-!
# Purely inseparable extension and relative perfect closure
This file contains basics about purely inseparable extensions and the relative perfect closure
of fields.
## Main definitions
- `IsPurelyInseparable`: typeclass for purely inseparable field extensions: an algebraic extension
`E / F` is purely inseparable if and only if the minimal polynomial of every element of `E ∖ F`
is not separable.
- `perfectClosure`: the relative perfect closure of `F` in `E`, it consists of the elements
`x` of `E` such that there exists a natural number `n` such that `x ^ (ringExpChar F) ^ n`
is contained in `F`, where `ringExpChar F` is the exponential characteristic of `F`.
It is also the maximal purely inseparable subextension of `E / F` (`le_perfectClosure_iff`).
## Main results
- `IsPurelyInseparable.surjective_algebraMap_of_isSeparable`,
`IsPurelyInseparable.bijective_algebraMap_of_isSeparable`,
`IntermediateField.eq_bot_of_isPurelyInseparable_of_isSeparable`:
if `E / F` is both purely inseparable and separable, then `algebraMap F E` is surjective
(hence bijective). In particular, if an intermediate field of `E / F` is both purely inseparable
and separable, then it is equal to `F`.
- `isPurelyInseparable_iff_pow_mem`: a field extension `E / F` of exponential characteristic `q` is
purely inseparable if and only if for every element `x` of `E`, there exists a natural number `n`
such that `x ^ (q ^ n)` is contained in `F`.
- `IsPurelyInseparable.trans`: if `E / F` and `K / E` are both purely inseparable extensions, then
`K / F` is also purely inseparable.
- `isPurelyInseparable_iff_natSepDegree_eq_one`: `E / F` is purely inseparable if and only if for
every element `x` of `E`, its minimal polynomial has separable degree one.
- `isPurelyInseparable_iff_minpoly_eq_X_pow_sub_C`: a field extension `E / F` of exponential
characteristic `q` is purely inseparable if and only if for every element `x` of `E`, the minimal
polynomial of `x` over `F` is of form `X ^ (q ^ n) - y` for some natural number `n` and some
element `y` of `F`.
- `isPurelyInseparable_iff_minpoly_eq_X_sub_C_pow`: a field extension `E / F` of exponential
characteristic `q` is purely inseparable if and only if for every element `x` of `E`, the minimal
polynomial of `x` over `F` is of form `(X - x) ^ (q ^ n)` for some natural number `n`.
- `isPurelyInseparable_iff_finSepDegree_eq_one`: an algebraic extension is purely inseparable
if and only if it has finite separable degree (`Field.finSepDegree`) one.
**TODO:** remove the algebraic assumption.
- `IsPurelyInseparable.normal`: a purely inseparable extension is normal.
- `separableClosure.isPurelyInseparable`: if `E / F` is algebraic, then `E` is purely inseparable
over the separable closure of `F` in `E`.
- `separableClosure_le_iff`: if `E / F` is algebraic, then an intermediate field of `E / F` contains
the separable closure of `F` in `E` if and only if `E` is purely inseparable over it.
- `eq_separableClosure_iff`: if `E / F` is algebraic, then an intermediate field of `E / F` is equal
to the separable closure of `F` in `E` if and only if it is separable over `F`, and `E`
is purely inseparable over it.
- `le_perfectClosure_iff`: an intermediate field of `E / F` is contained in the relative perfect
closure of `F` in `E` if and only if it is purely inseparable over `F`.
- `perfectClosure.perfectRing`, `perfectClosure.perfectField`: if `E` is a perfect field, then the
(relative) perfect closure `perfectClosure F E` is perfect.
- `IsPurelyInseparable.injective_comp_algebraMap`: if `E / F` is purely inseparable, then for any
reduced ring `L`, the map `(E →+* L) → (F →+* L)` induced by `algebraMap F E` is injective.
In particular, a purely inseparable field extension is an epimorphism in the category of fields.
- `IntermediateField.isPurelyInseparable_adjoin_iff_pow_mem`: if `F` is of exponential
characteristic `q`, then `F(S) / F` is a purely inseparable extension if and only if for any
`x ∈ S`, `x ^ (q ^ n)` is contained in `F` for some `n : ℕ`.
- `Field.finSepDegree_eq`: if `E / F` is algebraic, then the `Field.finSepDegree F E` is equal to
`Field.sepDegree F E` as a natural number. This means that the cardinality of `Field.Emb F E`
and the degree of `(separableClosure F E) / F` are both finite or infinite, and when they are
finite, they coincide.
- `Field.finSepDegree_mul_finInsepDegree`: the finite separable degree multiply by the finite
inseparable degree is equal to the (finite) field extension degree.
- `Field.lift_sepDegree_mul_lift_sepDegree_of_isAlgebraic`: the separable degrees satisfy the
tower law: $[E:F]_s [K:E]_s = [K:F]_s$.
- `IntermediateField.sepDegree_adjoin_eq_of_isAlgebraic_of_isPurelyInseparable`,
`IntermediateField.sepDegree_adjoin_eq_of_isAlgebraic_of_isPurelyInseparable'`:
if `K / E / F` is a field extension tower, such that `E / F` is purely inseparable, then
for any subset `S` of `K` such that `F(S) / F` is algebraic, the `E(S) / E` and `F(S) / F` have
the same separable degree. In particular, if `S` is an intermediate field of `K / F` such that
`S / F` is algebraic, the `E(S) / E` and `S / F` have the same separable degree.
- `minpoly.map_eq_of_separable_of_isPurelyInseparable`: if `K / E / F` is a field extension tower,
such that `E / F` is purely inseparable, then for any element `x` of `K` separable over `F`,
it has the same minimal polynomials over `F` and over `E`.
- `Polynomial.Separable.map_irreducible_of_isPurelyInseparable`: if `E / F` is purely inseparable,
`f` is a separable irreducible polynomial over `F`, then it is also irreducible over `E`.
## Tags
separable degree, degree, separable closure, purely inseparable
## TODO
- `IsPurelyInseparable.of_injective_comp_algebraMap`: if `L` is an algebraically closed field
containing `E`, such that the map `(E →+* L) → (F →+* L)` induced by `algebraMap F E` is
injective, then `E / F` is purely inseparable. As a corollary, epimorphisms in the category of
fields must be purely inseparable extensions. Need to use the fact that `Emb F E` is infinite
(or just not a singleton) when `E / F` is (purely) transcendental.
- Restate some intermediate result in terms of linearly disjointness.
- Prove that the inseparable degrees satisfy the tower law: $[E:F]_i [K:E]_i = [K:F]_i$.
Probably an argument using linearly disjointness is needed.
-/
open FiniteDimensional Polynomial IntermediateField Field
noncomputable section
universe u v w
variable (F : Type u) (E : Type v) [Field F] [Field E] [Algebra F E]
variable (K : Type w) [Field K] [Algebra F K]
section IsPurelyInseparable
/-- Typeclass for purely inseparable field extensions: an algebraic extension `E / F` is purely
inseparable if and only if the minimal polynomial of every element of `E ∖ F` is not separable. -/
class IsPurelyInseparable : Prop where
isIntegral : Algebra.IsIntegral F E
inseparable' (x : E) : (minpoly F x).Separable → x ∈ (algebraMap F E).range
attribute [instance] IsPurelyInseparable.isIntegral
variable {E} in
theorem IsPurelyInseparable.isIntegral' [IsPurelyInseparable F E] (x : E) : IsIntegral F x :=
Algebra.IsIntegral.isIntegral _
theorem IsPurelyInseparable.isAlgebraic [IsPurelyInseparable F E] :
Algebra.IsAlgebraic F E := inferInstance
variable {E}
theorem IsPurelyInseparable.inseparable [IsPurelyInseparable F E] :
∀ x : E, (minpoly F x).Separable → x ∈ (algebraMap F E).range :=
IsPurelyInseparable.inseparable'
variable {F K}
theorem isPurelyInseparable_iff : IsPurelyInseparable F E ↔ ∀ x : E,
IsIntegral F x ∧ ((minpoly F x).Separable → x ∈ (algebraMap F E).range) :=
⟨fun h x ↦ ⟨h.isIntegral' x, h.inseparable' x⟩, fun h ↦ ⟨⟨fun x ↦ (h x).1⟩, fun x ↦ (h x).2⟩⟩
/-- Transfer `IsPurelyInseparable` across an `AlgEquiv`. -/
theorem AlgEquiv.isPurelyInseparable (e : K ≃ₐ[F] E) [IsPurelyInseparable F K] :
IsPurelyInseparable F E := by
refine ⟨⟨fun _ ↦ by rw [← isIntegral_algEquiv e.symm]; exact IsPurelyInseparable.isIntegral' F _⟩,
fun x h ↦ ?_⟩
rw [← minpoly.algEquiv_eq e.symm] at h
simpa only [RingHom.mem_range, algebraMap_eq_apply] using IsPurelyInseparable.inseparable F _ h
theorem AlgEquiv.isPurelyInseparable_iff (e : K ≃ₐ[F] E) :
IsPurelyInseparable F K ↔ IsPurelyInseparable F E :=
⟨fun _ ↦ e.isPurelyInseparable, fun _ ↦ e.symm.isPurelyInseparable⟩
/-- If `E / F` is an algebraic extension, `F` is separably closed,
then `E / F` is purely inseparable. -/
theorem Algebra.IsAlgebraic.isPurelyInseparable_of_isSepClosed [Algebra.IsAlgebraic F E]
[IsSepClosed F] : IsPurelyInseparable F E :=
⟨inferInstance, fun x h ↦ minpoly.mem_range_of_degree_eq_one F x <|
IsSepClosed.degree_eq_one_of_irreducible F (minpoly.irreducible
(Algebra.IsIntegral.isIntegral _)) h⟩
variable (F E K)
/-- If `E / F` is both purely inseparable and separable, then `algebraMap F E` is surjective. -/
theorem IsPurelyInseparable.surjective_algebraMap_of_isSeparable
[IsPurelyInseparable F E] [IsSeparable F E] : Function.Surjective (algebraMap F E) :=
fun x ↦ IsPurelyInseparable.inseparable F x (IsSeparable.separable F x)
/-- If `E / F` is both purely inseparable and separable, then `algebraMap F E` is bijective. -/
theorem IsPurelyInseparable.bijective_algebraMap_of_isSeparable
[IsPurelyInseparable F E] [IsSeparable F E] : Function.Bijective (algebraMap F E) :=
⟨(algebraMap F E).injective, surjective_algebraMap_of_isSeparable F E⟩
variable {F E} in
/-- If an intermediate field of `E / F` is both purely inseparable and separable, then it is equal
to `F`. -/
theorem IntermediateField.eq_bot_of_isPurelyInseparable_of_isSeparable (L : IntermediateField F E)
[IsPurelyInseparable F L] [IsSeparable F L] : L = ⊥ := bot_unique fun x hx ↦ by
obtain ⟨y, hy⟩ := IsPurelyInseparable.surjective_algebraMap_of_isSeparable F L ⟨x, hx⟩
exact ⟨y, congr_arg (algebraMap L E) hy⟩
/-- If `E / F` is purely inseparable, then the separable closure of `F` in `E` is
equal to `F`. -/
theorem separableClosure.eq_bot_of_isPurelyInseparable [IsPurelyInseparable F E] :
separableClosure F E = ⊥ :=
bot_unique fun x h ↦ IsPurelyInseparable.inseparable F x (mem_separableClosure_iff.1 h)
variable {F E} in
/-- If `E / F` is an algebraic extension, then the separable closure of `F` in `E` is
equal to `F` if and only if `E / F` is purely inseparable. -/
theorem separableClosure.eq_bot_iff [Algebra.IsAlgebraic F E] :
separableClosure F E = ⊥ ↔ IsPurelyInseparable F E :=
⟨fun h ↦ isPurelyInseparable_iff.2 fun x ↦ ⟨Algebra.IsIntegral.isIntegral x, fun hs ↦ by
simpa only [h] using mem_separableClosure_iff.2 hs⟩, fun _ ↦ eq_bot_of_isPurelyInseparable F E⟩
instance isPurelyInseparable_self : IsPurelyInseparable F F :=
⟨inferInstance, fun x _ ↦ ⟨x, rfl⟩⟩
variable {E}
/-- A field extension `E / F` of exponential characteristic `q` is purely inseparable
if and only if for every element `x` of `E`, there exists a natural number `n` such that
`x ^ (q ^ n)` is contained in `F`. -/
theorem isPurelyInseparable_iff_pow_mem (q : ℕ) [ExpChar F q] :
IsPurelyInseparable F E ↔ ∀ x : E, ∃ n : ℕ, x ^ q ^ n ∈ (algebraMap F E).range := by
rw [isPurelyInseparable_iff]
refine ⟨fun h x ↦ ?_, fun h x ↦ ?_⟩
· obtain ⟨g, h1, n, h2⟩ := (minpoly.irreducible (h x).1).hasSeparableContraction q
exact ⟨n, (h _).2 <| h1.of_dvd <| minpoly.dvd F _ <| by
simpa only [expand_aeval, minpoly.aeval] using congr_arg (aeval x) h2⟩
have hdeg := (minpoly.natSepDegree_eq_one_iff_pow_mem q).2 (h x)
have halg : IsIntegral F x := by_contra fun h' ↦ by
simp only [minpoly.eq_zero h', natSepDegree_zero, zero_ne_one] at hdeg
refine ⟨halg, fun hsep ↦ ?_⟩
rw [hsep.natSepDegree_eq_natDegree, ← adjoin.finrank halg,
IntermediateField.finrank_eq_one_iff] at hdeg
simpa only [hdeg] using mem_adjoin_simple_self F x
theorem IsPurelyInseparable.pow_mem (q : ℕ) [ExpChar F q] [IsPurelyInseparable F E] (x : E) :
∃ n : ℕ, x ^ q ^ n ∈ (algebraMap F E).range :=
(isPurelyInseparable_iff_pow_mem F q).1 ‹_› x
end IsPurelyInseparable
section perfectClosure
/-- The relative perfect closure of `F` in `E`, consists of the elements `x` of `E` such that there
exists a natural number `n` such that `x ^ (ringExpChar F) ^ n` is contained in `F`, where
`ringExpChar F` is the exponential characteristic of `F`. It is also the maximal purely inseparable
subextension of `E / F` (`le_perfectClosure_iff`). -/
def perfectClosure : IntermediateField F E where
carrier := {x : E | ∃ n : ℕ, x ^ (ringExpChar F) ^ n ∈ (algebraMap F E).range}
add_mem' := by
rintro x y ⟨n, hx⟩ ⟨m, hy⟩
use n + m
have := expChar_of_injective_algebraMap (algebraMap F E).injective (ringExpChar F)
rw [add_pow_expChar_pow, pow_add, pow_mul, mul_comm (_ ^ n), pow_mul]
exact add_mem (pow_mem hx _) (pow_mem hy _)
mul_mem' := by
rintro x y ⟨n, hx⟩ ⟨m, hy⟩
use n + m
rw [mul_pow, pow_add, pow_mul, mul_comm (_ ^ n), pow_mul]
exact mul_mem (pow_mem hx _) (pow_mem hy _)
inv_mem' := by
rintro x ⟨n, hx⟩
use n; rw [inv_pow]
apply inv_mem (id hx : _ ∈ (⊥ : IntermediateField F E))
algebraMap_mem' := fun x ↦ ⟨0, by rw [pow_zero, pow_one]; exact ⟨x, rfl⟩⟩
variable {F E}
theorem mem_perfectClosure_iff {x : E} :
x ∈ perfectClosure F E ↔ ∃ n : ℕ, x ^ (ringExpChar F) ^ n ∈ (algebraMap F E).range := Iff.rfl
theorem mem_perfectClosure_iff_pow_mem (q : ℕ) [ExpChar F q] {x : E} :
x ∈ perfectClosure F E ↔ ∃ n : ℕ, x ^ q ^ n ∈ (algebraMap F E).range := by
rw [mem_perfectClosure_iff, ringExpChar.eq F q]
/-- An element is contained in the relative perfect closure if and only if its mininal polynomial
has separable degree one. -/
theorem mem_perfectClosure_iff_natSepDegree_eq_one {x : E} :
x ∈ perfectClosure F E ↔ (minpoly F x).natSepDegree = 1 := by
rw [mem_perfectClosure_iff, minpoly.natSepDegree_eq_one_iff_pow_mem (ringExpChar F)]
/-- A field extension `E / F` is purely inseparable if and only if the relative perfect closure of
`F` in `E` is equal to `E`. -/
theorem isPurelyInseparable_iff_perfectClosure_eq_top :
IsPurelyInseparable F E ↔ perfectClosure F E = ⊤ := by
rw [isPurelyInseparable_iff_pow_mem F (ringExpChar F)]
exact ⟨fun H ↦ top_unique fun x _ ↦ H x, fun H _ ↦ H.ge trivial⟩
variable (F E)
/-- The relative perfect closure of `F` in `E` is purely inseparable over `F`. -/
instance perfectClosure.isPurelyInseparable : IsPurelyInseparable F (perfectClosure F E) := by
rw [isPurelyInseparable_iff_pow_mem F (ringExpChar F)]
exact fun ⟨_, n, y, h⟩ ↦ ⟨n, y, (algebraMap _ E).injective h⟩
/-- The relative perfect closure of `F` in `E` is algebraic over `F`. -/
instance perfectClosure.isAlgebraic : Algebra.IsAlgebraic F (perfectClosure F E) :=
IsPurelyInseparable.isAlgebraic F _
/-- If `E / F` is separable, then the perfect closure of `F` in `E` is equal to `F`. Note that
the converse is not necessarily true (see https://math.stackexchange.com/a/3009197)
even when `E / F` is algebraic. -/
theorem perfectClosure.eq_bot_of_isSeparable [IsSeparable F E] : perfectClosure F E = ⊥ :=
haveI := isSeparable_tower_bot_of_isSeparable F (perfectClosure F E) E
eq_bot_of_isPurelyInseparable_of_isSeparable _
/-- An intermediate field of `E / F` is contained in the relative perfect closure of `F` in `E`
if it is purely inseparable over `F`. -/
theorem le_perfectClosure (L : IntermediateField F E) [h : IsPurelyInseparable F L] :
L ≤ perfectClosure F E := by
rw [isPurelyInseparable_iff_pow_mem F (ringExpChar F)] at h
intro x hx
obtain ⟨n, y, hy⟩ := h ⟨x, hx⟩
exact ⟨n, y, congr_arg (algebraMap L E) hy⟩
/-- An intermediate field of `E / F` is contained in the relative perfect closure of `F` in `E`
if and only if it is purely inseparable over `F`. -/
theorem le_perfectClosure_iff (L : IntermediateField F E) :
L ≤ perfectClosure F E ↔ IsPurelyInseparable F L := by
refine ⟨fun h ↦ (isPurelyInseparable_iff_pow_mem F (ringExpChar F)).2 fun x ↦ ?_,
fun _ ↦ le_perfectClosure F E L⟩
obtain ⟨n, y, hy⟩ := h x.2
exact ⟨n, y, (algebraMap L E).injective hy⟩
theorem separableClosure_inf_perfectClosure : separableClosure F E ⊓ perfectClosure F E = ⊥ :=
haveI := (le_separableClosure_iff F E _).mp (inf_le_left (b := perfectClosure F E))
haveI := (le_perfectClosure_iff F E _).mp (inf_le_right (a := separableClosure F E))
eq_bot_of_isPurelyInseparable_of_isSeparable _
section map
variable {F E K}
/-- If `i` is an `F`-algebra homomorphism from `E` to `K`, then `i x` is contained in
`perfectClosure F K` if and only if `x` is contained in `perfectClosure F E`. -/
theorem map_mem_perfectClosure_iff (i : E →ₐ[F] K) {x : E} :
i x ∈ perfectClosure F K ↔ x ∈ perfectClosure F E := by
simp_rw [mem_perfectClosure_iff]
refine ⟨fun ⟨n, y, h⟩ ↦ ⟨n, y, ?_⟩, fun ⟨n, y, h⟩ ↦ ⟨n, y, ?_⟩⟩
· apply_fun i using i.injective
rwa [AlgHom.commutes, map_pow]
simpa only [AlgHom.commutes, map_pow] using congr_arg i h
/-- If `i` is an `F`-algebra homomorphism from `E` to `K`, then the preimage of `perfectClosure F K`
under the map `i` is equal to `perfectClosure F E`. -/
theorem perfectClosure.comap_eq_of_algHom (i : E →ₐ[F] K) :
(perfectClosure F K).comap i = perfectClosure F E := by
ext x
exact map_mem_perfectClosure_iff i
/-- If `i` is an `F`-algebra homomorphism from `E` to `K`, then the image of `perfectClosure F E`
under the map `i` is contained in `perfectClosure F K`. -/
theorem perfectClosure.map_le_of_algHom (i : E →ₐ[F] K) :
(perfectClosure F E).map i ≤ perfectClosure F K :=
map_le_iff_le_comap.mpr (perfectClosure.comap_eq_of_algHom i).ge
/-- If `i` is an `F`-algebra isomorphism of `E` and `K`, then the image of `perfectClosure F E`
under the map `i` is equal to in `perfectClosure F K`. -/
theorem perfectClosure.map_eq_of_algEquiv (i : E ≃ₐ[F] K) :
(perfectClosure F E).map i.toAlgHom = perfectClosure F K :=
(map_le_of_algHom i.toAlgHom).antisymm (fun x hx ↦ ⟨i.symm x,
(map_mem_perfectClosure_iff i.symm.toAlgHom).2 hx, i.right_inv x⟩)
/-- If `E` and `K` are isomorphic as `F`-algebras, then `perfectClosure F E` and
`perfectClosure F K` are also isomorphic as `F`-algebras. -/
def perfectClosure.algEquivOfAlgEquiv (i : E ≃ₐ[F] K) :
perfectClosure F E ≃ₐ[F] perfectClosure F K :=
(intermediateFieldMap i _).trans (equivOfEq (map_eq_of_algEquiv i))
alias AlgEquiv.perfectClosure := perfectClosure.algEquivOfAlgEquiv
end map
/-- If `E` is a perfect field of exponential characteristic `p`, then the (relative) perfect closure
`perfectClosure F E` is perfect. -/
instance perfectClosure.perfectRing (p : ℕ) [ExpChar E p]
[PerfectRing E p] : PerfectRing (perfectClosure F E) p := .ofSurjective _ p fun x ↦ by
haveI := RingHom.expChar _ (algebraMap F E).injective p
obtain ⟨x', hx⟩ := surjective_frobenius E p x.1
obtain ⟨n, y, hy⟩ := (mem_perfectClosure_iff_pow_mem p).1 x.2
rw [frobenius_def] at hx
rw [← hx, ← pow_mul, ← pow_succ'] at hy
exact ⟨⟨x', (mem_perfectClosure_iff_pow_mem p).2 ⟨n + 1, y, hy⟩⟩, by
simp_rw [frobenius_def, SubmonoidClass.mk_pow, hx]⟩
/-- If `E` is a perfect field, then the (relative) perfect closure
`perfectClosure F E` is perfect. -/
instance perfectClosure.perfectField [PerfectField E] : PerfectField (perfectClosure F E) :=
PerfectRing.toPerfectField _ (ringExpChar E)
end perfectClosure
section IsPurelyInseparable
/-- If `K / E / F` is a field extension tower such that `K / F` is purely inseparable,
then `E / F` is also purely inseparable. -/
theorem IsPurelyInseparable.tower_bot [Algebra E K] [IsScalarTower F E K]
[IsPurelyInseparable F K] : IsPurelyInseparable F E := by
refine ⟨⟨fun x ↦ (isIntegral' F (algebraMap E K x)).tower_bot_of_field⟩, fun x h ↦ ?_⟩
rw [← minpoly.algebraMap_eq (algebraMap E K).injective] at h
obtain ⟨y, h⟩ := inseparable F _ h
exact ⟨y, (algebraMap E K).injective (h.symm ▸ (IsScalarTower.algebraMap_apply F E K y).symm)⟩
/-- If `K / E / F` is a field extension tower such that `K / F` is purely inseparable,
then `K / E` is also purely inseparable. -/
theorem IsPurelyInseparable.tower_top [Algebra E K] [IsScalarTower F E K]
[h : IsPurelyInseparable F K] : IsPurelyInseparable E K := by
obtain ⟨q, _⟩ := ExpChar.exists F
haveI := expChar_of_injective_algebraMap (algebraMap F E).injective q
rw [isPurelyInseparable_iff_pow_mem _ q] at h ⊢
intro x
obtain ⟨n, y, h⟩ := h x
exact ⟨n, (algebraMap F E) y, h.symm ▸ (IsScalarTower.algebraMap_apply F E K y).symm⟩
/-- If `E / F` and `K / E` are both purely inseparable extensions, then `K / F` is also
purely inseparable. -/
theorem IsPurelyInseparable.trans [Algebra E K] [IsScalarTower F E K]
[h1 : IsPurelyInseparable F E] [h2 : IsPurelyInseparable E K] : IsPurelyInseparable F K := by
obtain ⟨q, _⟩ := ExpChar.exists F
haveI := expChar_of_injective_algebraMap (algebraMap F E).injective q
rw [isPurelyInseparable_iff_pow_mem _ q] at h1 h2 ⊢
intro x
obtain ⟨n, y, h2⟩ := h2 x
obtain ⟨m, z, h1⟩ := h1 y
refine ⟨n + m, z, ?_⟩
rw [IsScalarTower.algebraMap_apply F E K, h1, map_pow, h2, ← pow_mul, ← pow_add]
variable {E}
/-- A field extension `E / F` is purely inseparable if and only if for every element `x` of `E`,
its minimal polynomial has separable degree one. -/
theorem isPurelyInseparable_iff_natSepDegree_eq_one :
IsPurelyInseparable F E ↔ ∀ x : E, (minpoly F x).natSepDegree = 1 := by
obtain ⟨q, _⟩ := ExpChar.exists F
simp_rw [isPurelyInseparable_iff_pow_mem F q, minpoly.natSepDegree_eq_one_iff_pow_mem q]
theorem IsPurelyInseparable.natSepDegree_eq_one [IsPurelyInseparable F E] (x : E) :
(minpoly F x).natSepDegree = 1 :=
(isPurelyInseparable_iff_natSepDegree_eq_one F).1 ‹_› x
/-- A field extension `E / F` of exponential characteristic `q` is purely inseparable
if and only if for every element `x` of `E`, the minimal polynomial of `x` over `F` is of form
`X ^ (q ^ n) - y` for some natural number `n` and some element `y` of `F`. -/
theorem isPurelyInseparable_iff_minpoly_eq_X_pow_sub_C (q : ℕ) [hF : ExpChar F q] :
IsPurelyInseparable F E ↔ ∀ x : E, ∃ (n : ℕ) (y : F), minpoly F x = X ^ q ^ n - C y := by
simp_rw [isPurelyInseparable_iff_natSepDegree_eq_one,
minpoly.natSepDegree_eq_one_iff_eq_X_pow_sub_C q]
theorem IsPurelyInseparable.minpoly_eq_X_pow_sub_C (q : ℕ) [ExpChar F q] [IsPurelyInseparable F E]
(x : E) : ∃ (n : ℕ) (y : F), minpoly F x = X ^ q ^ n - C y :=
(isPurelyInseparable_iff_minpoly_eq_X_pow_sub_C F q).1 ‹_› x
/-- A field extension `E / F` of exponential characteristic `q` is purely inseparable
if and only if for every element `x` of `E`, the minimal polynomial of `x` over `F` is of form
`(X - x) ^ (q ^ n)` for some natural number `n`. -/
theorem isPurelyInseparable_iff_minpoly_eq_X_sub_C_pow (q : ℕ) [hF : ExpChar F q] :
IsPurelyInseparable F E ↔
∀ x : E, ∃ n : ℕ, (minpoly F x).map (algebraMap F E) = (X - C x) ^ q ^ n := by
simp_rw [isPurelyInseparable_iff_natSepDegree_eq_one,
minpoly.natSepDegree_eq_one_iff_eq_X_sub_C_pow q]
theorem IsPurelyInseparable.minpoly_eq_X_sub_C_pow (q : ℕ) [ExpChar F q] [IsPurelyInseparable F E]
(x : E) : ∃ n : ℕ, (minpoly F x).map (algebraMap F E) = (X - C x) ^ q ^ n :=
(isPurelyInseparable_iff_minpoly_eq_X_sub_C_pow F q).1 ‹_› x
variable (E)
-- TODO: remove `halg` assumption
variable {F E} in
/-- If an algebraic extension has finite separable degree one, then it is purely inseparable. -/
theorem isPurelyInseparable_of_finSepDegree_eq_one [Algebra.IsAlgebraic F E]
(hdeg : finSepDegree F E = 1) : IsPurelyInseparable F E := by
rw [isPurelyInseparable_iff]
refine fun x ↦ ⟨Algebra.IsIntegral.isIntegral x, fun hsep ↦ ?_⟩
have : Algebra.IsAlgebraic F⟮x⟯ E := Algebra.IsAlgebraic.tower_top (K := F) F⟮x⟯
have := finSepDegree_mul_finSepDegree_of_isAlgebraic F F⟮x⟯ E
rw [hdeg, mul_eq_one, (finSepDegree_adjoin_simple_eq_finrank_iff F E x
(Algebra.IsAlgebraic.isAlgebraic x)).2 hsep,
IntermediateField.finrank_eq_one_iff] at this
simpa only [this.1] using mem_adjoin_simple_self F x
/-- If `E / F` is purely inseparable, then for any reduced ring `L`, the map `(E →+* L) → (F →+* L)`
induced by `algebraMap F E` is injective. In particular, a purely inseparable field extension
is an epimorphism in the category of fields. -/
theorem IsPurelyInseparable.injective_comp_algebraMap [IsPurelyInseparable F E]
(L : Type w) [CommRing L] [IsReduced L] :
Function.Injective fun f : E →+* L ↦ f.comp (algebraMap F E) := fun f g heq ↦ by
ext x
let q := ringExpChar F
obtain ⟨n, y, h⟩ := IsPurelyInseparable.pow_mem F q x
replace heq := congr($heq y)
simp_rw [RingHom.comp_apply, h, map_pow] at heq
nontriviality L
haveI := expChar_of_injective_ringHom (f.comp (algebraMap F E)).injective q
exact iterateFrobenius_inj L q n heq
/-- If `E / F` is purely inseparable, then for any reduced `F`-algebra `L`, there exists at most one
`F`-algebra homomorphism from `E` to `L`. -/
instance instSubsingletonAlgHomOfIsPurelyInseparable [IsPurelyInseparable F E] (L : Type w)
[CommRing L] [IsReduced L] [Algebra F L] : Subsingleton (E →ₐ[F] L) where
allEq f g := AlgHom.coe_ringHom_injective <|
IsPurelyInseparable.injective_comp_algebraMap F E L (by simp_rw [AlgHom.comp_algebraMap])
instance instUniqueAlgHomOfIsPurelyInseparable [IsPurelyInseparable F E] (L : Type w)
[CommRing L] [IsReduced L] [Algebra F L] [Algebra E L] [IsScalarTower F E L] :
Unique (E →ₐ[F] L) := uniqueOfSubsingleton (IsScalarTower.toAlgHom F E L)
/-- If `E / F` is purely inseparable, then `Field.Emb F E` has exactly one element. -/
instance instUniqueEmbOfIsPurelyInseparable [IsPurelyInseparable F E] :
Unique (Emb F E) := instUniqueAlgHomOfIsPurelyInseparable F E _
/-- A purely inseparable extension has finite separable degree one. -/
theorem IsPurelyInseparable.finSepDegree_eq_one [IsPurelyInseparable F E] :
finSepDegree F E = 1 := Nat.card_unique
/-- A purely inseparable extension has separable degree one. -/
theorem IsPurelyInseparable.sepDegree_eq_one [IsPurelyInseparable F E] :
sepDegree F E = 1 := by
rw [sepDegree, separableClosure.eq_bot_of_isPurelyInseparable, IntermediateField.rank_bot]
/-- A purely inseparable extension has inseparable degree equal to degree. -/
theorem IsPurelyInseparable.insepDegree_eq [IsPurelyInseparable F E] :
insepDegree F E = Module.rank F E := by
rw [insepDegree, separableClosure.eq_bot_of_isPurelyInseparable, rank_bot']
/-- A purely inseparable extension has finite inseparable degree equal to degree. -/
theorem IsPurelyInseparable.finInsepDegree_eq [IsPurelyInseparable F E] :
finInsepDegree F E = finrank F E := congr(Cardinal.toNat $(insepDegree_eq F E))
-- TODO: remove `halg` assumption
/-- An algebraic extension is purely inseparable if and only if it has finite separable
degree one. -/
theorem isPurelyInseparable_iff_finSepDegree_eq_one [Algebra.IsAlgebraic F E] :
IsPurelyInseparable F E ↔ finSepDegree F E = 1 :=
⟨fun _ ↦ IsPurelyInseparable.finSepDegree_eq_one F E,
fun h ↦ isPurelyInseparable_of_finSepDegree_eq_one h⟩
variable {F E} in
/-- An algebraic extension is purely inseparable if and only if all of its finite dimensional
subextensions are purely inseparable. -/
theorem isPurelyInseparable_iff_fd_isPurelyInseparable [Algebra.IsAlgebraic F E] :
IsPurelyInseparable F E ↔
∀ L : IntermediateField F E, FiniteDimensional F L → IsPurelyInseparable F L := by
refine ⟨fun _ _ _ ↦ IsPurelyInseparable.tower_bot F _ E,
fun h ↦ isPurelyInseparable_iff.2 fun x ↦ ?_⟩
have hx : IsIntegral F x := Algebra.IsIntegral.isIntegral x
refine ⟨hx, fun _ ↦ ?_⟩
obtain ⟨y, h⟩ := (h _ (adjoin.finiteDimensional hx)).inseparable' _ <|
show Separable (minpoly F (AdjoinSimple.gen F x)) by rwa [minpoly_eq]
exact ⟨y, congr_arg (algebraMap _ E) h⟩
/-- A purely inseparable extension is normal. -/
instance IsPurelyInseparable.normal [IsPurelyInseparable F E] : Normal F E where
toIsAlgebraic := isAlgebraic F E
splits' x := by
obtain ⟨n, h⟩ := IsPurelyInseparable.minpoly_eq_X_sub_C_pow F (ringExpChar F) x
rw [← splits_id_iff_splits, h]
exact splits_pow _ (splits_X_sub_C _) _
/-- If `E / F` is algebraic, then `E` is purely inseparable over the
separable closure of `F` in `E`. -/
theorem separableClosure.isPurelyInseparable [Algebra.IsAlgebraic F E] :
IsPurelyInseparable (separableClosure F E) E := isPurelyInseparable_iff.2 fun x ↦ by
set L := separableClosure F E
refine ⟨(IsAlgebraic.tower_top L (Algebra.IsAlgebraic.isAlgebraic (R := F) x)).isIntegral,
fun h ↦ ?_⟩
haveI := (isSeparable_adjoin_simple_iff_separable L E).2 h
haveI : IsSeparable F (restrictScalars F L⟮x⟯) := IsSeparable.trans F L L⟮x⟯
have hx : x ∈ restrictScalars F L⟮x⟯ := mem_adjoin_simple_self _ x
exact ⟨⟨x, mem_separableClosure_iff.2 <| separable_of_mem_isSeparable F E hx⟩, rfl⟩
/-- An intermediate field of `E / F` contains the separable closure of `F` in `E`
if `E` is purely inseparable over it. -/
theorem separableClosure_le (L : IntermediateField F E)
[h : IsPurelyInseparable L E] : separableClosure F E ≤ L := fun x hx ↦ by
obtain ⟨y, rfl⟩ := h.inseparable' _ <| (mem_separableClosure_iff.1 hx).map_minpoly L
exact y.2
/-- If `E / F` is algebraic, then an intermediate field of `E / F` contains the
separable closure of `F` in `E` if and only if `E` is purely inseparable over it. -/
theorem separableClosure_le_iff [Algebra.IsAlgebraic F E] (L : IntermediateField F E) :
separableClosure F E ≤ L ↔ IsPurelyInseparable L E := by
refine ⟨fun h ↦ ?_, fun _ ↦ separableClosure_le F E L⟩
have := separableClosure.isPurelyInseparable F E
letI := (inclusion h).toAlgebra
letI : SMul (separableClosure F E) L := Algebra.toSMul
haveI : IsScalarTower (separableClosure F E) L E := IsScalarTower.of_algebraMap_eq (congrFun rfl)
exact IsPurelyInseparable.tower_top (separableClosure F E) L E
/-- If an intermediate field of `E / F` is separable over `F`, and `E` is purely inseparable
over it, then it is equal to the separable closure of `F` in `E`. -/
theorem eq_separableClosure (L : IntermediateField F E)
[IsSeparable F L] [IsPurelyInseparable L E] : L = separableClosure F E :=
le_antisymm (le_separableClosure F E L) (separableClosure_le F E L)
open separableClosure in
/-- If `E / F` is algebraic, then an intermediate field of `E / F` is equal to the separable closure
of `F` in `E` if and only if it is separable over `F`, and `E` is purely inseparable
over it. -/
theorem eq_separableClosure_iff [Algebra.IsAlgebraic F E] (L : IntermediateField F E) :
L = separableClosure F E ↔ IsSeparable F L ∧ IsPurelyInseparable L E :=
⟨by rintro rfl; exact ⟨isSeparable F E, isPurelyInseparable F E⟩,
fun ⟨_, _⟩ ↦ eq_separableClosure F E L⟩
-- TODO: prove it
set_option linter.unusedVariables false in
/-- If `L` is an algebraically closed field containing `E`, such that the map
`(E →+* L) → (F →+* L)` induced by `algebraMap F E` is injective, then `E / F` is
purely inseparable. As a corollary, epimorphisms in the category of fields must be
purely inseparable extensions. -/
proof_wanted IsPurelyInseparable.of_injective_comp_algebraMap (L : Type w) [Field L] [IsAlgClosed L]
(hn : Nonempty (E →+* L)) (h : Function.Injective fun f : E →+* L ↦ f.comp (algebraMap F E)) :
IsPurelyInseparable F E
end IsPurelyInseparable
namespace IntermediateField
instance isPurelyInseparable_bot : IsPurelyInseparable F (⊥ : IntermediateField F E) :=
(botEquiv F E).symm.isPurelyInseparable
/-- `F⟮x⟯ / F` is a purely inseparable extension if and only if the mininal polynomial of `x`
has separable degree one. -/
| Mathlib/FieldTheory/PurelyInseparable.lean | 633 | 635 | theorem isPurelyInseparable_adjoin_simple_iff_natSepDegree_eq_one {x : E} :
IsPurelyInseparable F F⟮x⟯ ↔ (minpoly F x).natSepDegree = 1 := by |
rw [← le_perfectClosure_iff, adjoin_simple_le_iff, mem_perfectClosure_iff_natSepDegree_eq_one]
|
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Mario Carneiro, Patrick Massot
-/
import Mathlib.GroupTheory.GroupAction.ConjAct
import Mathlib.GroupTheory.GroupAction.Quotient
import Mathlib.GroupTheory.QuotientGroup
import Mathlib.Topology.Algebra.Monoid
import Mathlib.Topology.Algebra.Constructions
#align_import topology.algebra.group.basic from "leanprover-community/mathlib"@"3b1890e71632be9e3b2086ab512c3259a7e9a3ef"
/-!
# Topological groups
This file defines the following typeclasses:
* `TopologicalGroup`, `TopologicalAddGroup`: multiplicative and additive topological groups,
i.e., groups with continuous `(*)` and `(⁻¹)` / `(+)` and `(-)`;
* `ContinuousSub G` means that `G` has a continuous subtraction operation.
There is an instance deducing `ContinuousSub` from `TopologicalGroup` but we use a separate
typeclass because, e.g., `ℕ` and `ℝ≥0` have continuous subtraction but are not additive groups.
We also define `Homeomorph` versions of several `Equiv`s: `Homeomorph.mulLeft`,
`Homeomorph.mulRight`, `Homeomorph.inv`, and prove a few facts about neighbourhood filters in
groups.
## Tags
topological space, group, topological group
-/
open scoped Classical
open Set Filter TopologicalSpace Function Topology Pointwise MulOpposite
universe u v w x
variable {G : Type w} {H : Type x} {α : Type u} {β : Type v}
section ContinuousMulGroup
/-!
### Groups with continuous multiplication
In this section we prove a few statements about groups with continuous `(*)`.
-/
variable [TopologicalSpace G] [Group G] [ContinuousMul G]
/-- Multiplication from the left in a topological group as a homeomorphism. -/
@[to_additive "Addition from the left in a topological additive group as a homeomorphism."]
protected def Homeomorph.mulLeft (a : G) : G ≃ₜ G :=
{ Equiv.mulLeft a with
continuous_toFun := continuous_const.mul continuous_id
continuous_invFun := continuous_const.mul continuous_id }
#align homeomorph.mul_left Homeomorph.mulLeft
#align homeomorph.add_left Homeomorph.addLeft
@[to_additive (attr := simp)]
theorem Homeomorph.coe_mulLeft (a : G) : ⇑(Homeomorph.mulLeft a) = (a * ·) :=
rfl
#align homeomorph.coe_mul_left Homeomorph.coe_mulLeft
#align homeomorph.coe_add_left Homeomorph.coe_addLeft
@[to_additive]
theorem Homeomorph.mulLeft_symm (a : G) : (Homeomorph.mulLeft a).symm = Homeomorph.mulLeft a⁻¹ := by
ext
rfl
#align homeomorph.mul_left_symm Homeomorph.mulLeft_symm
#align homeomorph.add_left_symm Homeomorph.addLeft_symm
@[to_additive]
lemma isOpenMap_mul_left (a : G) : IsOpenMap (a * ·) := (Homeomorph.mulLeft a).isOpenMap
#align is_open_map_mul_left isOpenMap_mul_left
#align is_open_map_add_left isOpenMap_add_left
@[to_additive IsOpen.left_addCoset]
theorem IsOpen.leftCoset {U : Set G} (h : IsOpen U) (x : G) : IsOpen (x • U) :=
isOpenMap_mul_left x _ h
#align is_open.left_coset IsOpen.leftCoset
#align is_open.left_add_coset IsOpen.left_addCoset
@[to_additive]
lemma isClosedMap_mul_left (a : G) : IsClosedMap (a * ·) := (Homeomorph.mulLeft a).isClosedMap
#align is_closed_map_mul_left isClosedMap_mul_left
#align is_closed_map_add_left isClosedMap_add_left
@[to_additive IsClosed.left_addCoset]
theorem IsClosed.leftCoset {U : Set G} (h : IsClosed U) (x : G) : IsClosed (x • U) :=
isClosedMap_mul_left x _ h
#align is_closed.left_coset IsClosed.leftCoset
#align is_closed.left_add_coset IsClosed.left_addCoset
/-- Multiplication from the right in a topological group as a homeomorphism. -/
@[to_additive "Addition from the right in a topological additive group as a homeomorphism."]
protected def Homeomorph.mulRight (a : G) : G ≃ₜ G :=
{ Equiv.mulRight a with
continuous_toFun := continuous_id.mul continuous_const
continuous_invFun := continuous_id.mul continuous_const }
#align homeomorph.mul_right Homeomorph.mulRight
#align homeomorph.add_right Homeomorph.addRight
@[to_additive (attr := simp)]
lemma Homeomorph.coe_mulRight (a : G) : ⇑(Homeomorph.mulRight a) = (· * a) := rfl
#align homeomorph.coe_mul_right Homeomorph.coe_mulRight
#align homeomorph.coe_add_right Homeomorph.coe_addRight
@[to_additive]
theorem Homeomorph.mulRight_symm (a : G) :
(Homeomorph.mulRight a).symm = Homeomorph.mulRight a⁻¹ := by
ext
rfl
#align homeomorph.mul_right_symm Homeomorph.mulRight_symm
#align homeomorph.add_right_symm Homeomorph.addRight_symm
@[to_additive]
theorem isOpenMap_mul_right (a : G) : IsOpenMap (· * a) :=
(Homeomorph.mulRight a).isOpenMap
#align is_open_map_mul_right isOpenMap_mul_right
#align is_open_map_add_right isOpenMap_add_right
@[to_additive IsOpen.right_addCoset]
theorem IsOpen.rightCoset {U : Set G} (h : IsOpen U) (x : G) : IsOpen (op x • U) :=
isOpenMap_mul_right x _ h
#align is_open.right_coset IsOpen.rightCoset
#align is_open.right_add_coset IsOpen.right_addCoset
@[to_additive]
theorem isClosedMap_mul_right (a : G) : IsClosedMap (· * a) :=
(Homeomorph.mulRight a).isClosedMap
#align is_closed_map_mul_right isClosedMap_mul_right
#align is_closed_map_add_right isClosedMap_add_right
@[to_additive IsClosed.right_addCoset]
theorem IsClosed.rightCoset {U : Set G} (h : IsClosed U) (x : G) : IsClosed (op x • U) :=
isClosedMap_mul_right x _ h
#align is_closed.right_coset IsClosed.rightCoset
#align is_closed.right_add_coset IsClosed.right_addCoset
@[to_additive]
theorem discreteTopology_of_isOpen_singleton_one (h : IsOpen ({1} : Set G)) :
DiscreteTopology G := by
rw [← singletons_open_iff_discrete]
intro g
suffices {g} = (g⁻¹ * ·) ⁻¹' {1} by
rw [this]
exact (continuous_mul_left g⁻¹).isOpen_preimage _ h
simp only [mul_one, Set.preimage_mul_left_singleton, eq_self_iff_true, inv_inv,
Set.singleton_eq_singleton_iff]
#align discrete_topology_of_open_singleton_one discreteTopology_of_isOpen_singleton_one
#align discrete_topology_of_open_singleton_zero discreteTopology_of_isOpen_singleton_zero
@[to_additive]
theorem discreteTopology_iff_isOpen_singleton_one : DiscreteTopology G ↔ IsOpen ({1} : Set G) :=
⟨fun h => forall_open_iff_discrete.mpr h {1}, discreteTopology_of_isOpen_singleton_one⟩
#align discrete_topology_iff_open_singleton_one discreteTopology_iff_isOpen_singleton_one
#align discrete_topology_iff_open_singleton_zero discreteTopology_iff_isOpen_singleton_zero
end ContinuousMulGroup
/-!
### `ContinuousInv` and `ContinuousNeg`
-/
/-- Basic hypothesis to talk about a topological additive group. A topological additive group
over `M`, for example, is obtained by requiring the instances `AddGroup M` and
`ContinuousAdd M` and `ContinuousNeg M`. -/
class ContinuousNeg (G : Type u) [TopologicalSpace G] [Neg G] : Prop where
continuous_neg : Continuous fun a : G => -a
#align has_continuous_neg ContinuousNeg
-- Porting note: added
attribute [continuity] ContinuousNeg.continuous_neg
/-- Basic hypothesis to talk about a topological group. A topological group over `M`, for example,
is obtained by requiring the instances `Group M` and `ContinuousMul M` and
`ContinuousInv M`. -/
@[to_additive (attr := continuity)]
class ContinuousInv (G : Type u) [TopologicalSpace G] [Inv G] : Prop where
continuous_inv : Continuous fun a : G => a⁻¹
#align has_continuous_inv ContinuousInv
--#align has_continuous_neg ContinuousNeg
-- Porting note: added
attribute [continuity] ContinuousInv.continuous_inv
export ContinuousInv (continuous_inv)
export ContinuousNeg (continuous_neg)
section ContinuousInv
variable [TopologicalSpace G] [Inv G] [ContinuousInv G]
@[to_additive]
protected theorem Specializes.inv {x y : G} (h : x ⤳ y) : (x⁻¹) ⤳ (y⁻¹) :=
h.map continuous_inv
@[to_additive]
protected theorem Inseparable.inv {x y : G} (h : Inseparable x y) : Inseparable (x⁻¹) (y⁻¹) :=
h.map continuous_inv
@[to_additive]
protected theorem Specializes.zpow {G : Type*} [DivInvMonoid G] [TopologicalSpace G]
[ContinuousMul G] [ContinuousInv G] {x y : G} (h : x ⤳ y) : ∀ m : ℤ, (x ^ m) ⤳ (y ^ m)
| .ofNat n => by simpa using h.pow n
| .negSucc n => by simpa using (h.pow (n + 1)).inv
@[to_additive]
protected theorem Inseparable.zpow {G : Type*} [DivInvMonoid G] [TopologicalSpace G]
[ContinuousMul G] [ContinuousInv G] {x y : G} (h : Inseparable x y) (m : ℤ) :
Inseparable (x ^ m) (y ^ m) :=
(h.specializes.zpow m).antisymm (h.specializes'.zpow m)
@[to_additive]
instance : ContinuousInv (ULift G) :=
⟨continuous_uLift_up.comp (continuous_inv.comp continuous_uLift_down)⟩
@[to_additive]
theorem continuousOn_inv {s : Set G} : ContinuousOn Inv.inv s :=
continuous_inv.continuousOn
#align continuous_on_inv continuousOn_inv
#align continuous_on_neg continuousOn_neg
@[to_additive]
theorem continuousWithinAt_inv {s : Set G} {x : G} : ContinuousWithinAt Inv.inv s x :=
continuous_inv.continuousWithinAt
#align continuous_within_at_inv continuousWithinAt_inv
#align continuous_within_at_neg continuousWithinAt_neg
@[to_additive]
theorem continuousAt_inv {x : G} : ContinuousAt Inv.inv x :=
continuous_inv.continuousAt
#align continuous_at_inv continuousAt_inv
#align continuous_at_neg continuousAt_neg
@[to_additive]
theorem tendsto_inv (a : G) : Tendsto Inv.inv (𝓝 a) (𝓝 a⁻¹) :=
continuousAt_inv
#align tendsto_inv tendsto_inv
#align tendsto_neg tendsto_neg
/-- If a function converges to a value in a multiplicative topological group, then its inverse
converges to the inverse of this value. For the version in normed fields assuming additionally
that the limit is nonzero, use `Tendsto.inv'`. -/
@[to_additive
"If a function converges to a value in an additive topological group, then its
negation converges to the negation of this value."]
theorem Filter.Tendsto.inv {f : α → G} {l : Filter α} {y : G} (h : Tendsto f l (𝓝 y)) :
Tendsto (fun x => (f x)⁻¹) l (𝓝 y⁻¹) :=
(continuous_inv.tendsto y).comp h
#align filter.tendsto.inv Filter.Tendsto.inv
#align filter.tendsto.neg Filter.Tendsto.neg
variable [TopologicalSpace α] {f : α → G} {s : Set α} {x : α}
@[to_additive (attr := continuity, fun_prop)]
theorem Continuous.inv (hf : Continuous f) : Continuous fun x => (f x)⁻¹ :=
continuous_inv.comp hf
#align continuous.inv Continuous.inv
#align continuous.neg Continuous.neg
@[to_additive (attr := fun_prop)]
theorem ContinuousAt.inv (hf : ContinuousAt f x) : ContinuousAt (fun x => (f x)⁻¹) x :=
continuousAt_inv.comp hf
#align continuous_at.inv ContinuousAt.inv
#align continuous_at.neg ContinuousAt.neg
@[to_additive (attr := fun_prop)]
theorem ContinuousOn.inv (hf : ContinuousOn f s) : ContinuousOn (fun x => (f x)⁻¹) s :=
continuous_inv.comp_continuousOn hf
#align continuous_on.inv ContinuousOn.inv
#align continuous_on.neg ContinuousOn.neg
@[to_additive]
theorem ContinuousWithinAt.inv (hf : ContinuousWithinAt f s x) :
ContinuousWithinAt (fun x => (f x)⁻¹) s x :=
Filter.Tendsto.inv hf
#align continuous_within_at.inv ContinuousWithinAt.inv
#align continuous_within_at.neg ContinuousWithinAt.neg
@[to_additive]
instance Prod.continuousInv [TopologicalSpace H] [Inv H] [ContinuousInv H] :
ContinuousInv (G × H) :=
⟨continuous_inv.fst'.prod_mk continuous_inv.snd'⟩
variable {ι : Type*}
@[to_additive]
instance Pi.continuousInv {C : ι → Type*} [∀ i, TopologicalSpace (C i)] [∀ i, Inv (C i)]
[∀ i, ContinuousInv (C i)] : ContinuousInv (∀ i, C i) where
continuous_inv := continuous_pi fun i => (continuous_apply i).inv
#align pi.has_continuous_inv Pi.continuousInv
#align pi.has_continuous_neg Pi.continuousNeg
/-- A version of `Pi.continuousInv` for non-dependent functions. It is needed because sometimes
Lean fails to use `Pi.continuousInv` for non-dependent functions. -/
@[to_additive
"A version of `Pi.continuousNeg` for non-dependent functions. It is needed
because sometimes Lean fails to use `Pi.continuousNeg` for non-dependent functions."]
instance Pi.has_continuous_inv' : ContinuousInv (ι → G) :=
Pi.continuousInv
#align pi.has_continuous_inv' Pi.has_continuous_inv'
#align pi.has_continuous_neg' Pi.has_continuous_neg'
@[to_additive]
instance (priority := 100) continuousInv_of_discreteTopology [TopologicalSpace H] [Inv H]
[DiscreteTopology H] : ContinuousInv H :=
⟨continuous_of_discreteTopology⟩
#align has_continuous_inv_of_discrete_topology continuousInv_of_discreteTopology
#align has_continuous_neg_of_discrete_topology continuousNeg_of_discreteTopology
section PointwiseLimits
variable (G₁ G₂ : Type*) [TopologicalSpace G₂] [T2Space G₂]
@[to_additive]
theorem isClosed_setOf_map_inv [Inv G₁] [Inv G₂] [ContinuousInv G₂] :
IsClosed { f : G₁ → G₂ | ∀ x, f x⁻¹ = (f x)⁻¹ } := by
simp only [setOf_forall]
exact isClosed_iInter fun i => isClosed_eq (continuous_apply _) (continuous_apply _).inv
#align is_closed_set_of_map_inv isClosed_setOf_map_inv
#align is_closed_set_of_map_neg isClosed_setOf_map_neg
end PointwiseLimits
instance [TopologicalSpace H] [Inv H] [ContinuousInv H] : ContinuousNeg (Additive H) where
continuous_neg := @continuous_inv H _ _ _
instance [TopologicalSpace H] [Neg H] [ContinuousNeg H] : ContinuousInv (Multiplicative H) where
continuous_inv := @continuous_neg H _ _ _
end ContinuousInv
section ContinuousInvolutiveInv
variable [TopologicalSpace G] [InvolutiveInv G] [ContinuousInv G] {s : Set G}
@[to_additive]
theorem IsCompact.inv (hs : IsCompact s) : IsCompact s⁻¹ := by
rw [← image_inv]
exact hs.image continuous_inv
#align is_compact.inv IsCompact.inv
#align is_compact.neg IsCompact.neg
variable (G)
/-- Inversion in a topological group as a homeomorphism. -/
@[to_additive "Negation in a topological group as a homeomorphism."]
protected def Homeomorph.inv (G : Type*) [TopologicalSpace G] [InvolutiveInv G]
[ContinuousInv G] : G ≃ₜ G :=
{ Equiv.inv G with
continuous_toFun := continuous_inv
continuous_invFun := continuous_inv }
#align homeomorph.inv Homeomorph.inv
#align homeomorph.neg Homeomorph.neg
@[to_additive (attr := simp)]
lemma Homeomorph.coe_inv {G : Type*} [TopologicalSpace G] [InvolutiveInv G] [ContinuousInv G] :
⇑(Homeomorph.inv G) = Inv.inv := rfl
@[to_additive]
theorem isOpenMap_inv : IsOpenMap (Inv.inv : G → G) :=
(Homeomorph.inv _).isOpenMap
#align is_open_map_inv isOpenMap_inv
#align is_open_map_neg isOpenMap_neg
@[to_additive]
theorem isClosedMap_inv : IsClosedMap (Inv.inv : G → G) :=
(Homeomorph.inv _).isClosedMap
#align is_closed_map_inv isClosedMap_inv
#align is_closed_map_neg isClosedMap_neg
variable {G}
@[to_additive]
theorem IsOpen.inv (hs : IsOpen s) : IsOpen s⁻¹ :=
hs.preimage continuous_inv
#align is_open.inv IsOpen.inv
#align is_open.neg IsOpen.neg
@[to_additive]
theorem IsClosed.inv (hs : IsClosed s) : IsClosed s⁻¹ :=
hs.preimage continuous_inv
#align is_closed.inv IsClosed.inv
#align is_closed.neg IsClosed.neg
@[to_additive]
theorem inv_closure : ∀ s : Set G, (closure s)⁻¹ = closure s⁻¹ :=
(Homeomorph.inv G).preimage_closure
#align inv_closure inv_closure
#align neg_closure neg_closure
end ContinuousInvolutiveInv
section LatticeOps
variable {ι' : Sort*} [Inv G]
@[to_additive]
theorem continuousInv_sInf {ts : Set (TopologicalSpace G)}
(h : ∀ t ∈ ts, @ContinuousInv G t _) : @ContinuousInv G (sInf ts) _ :=
letI := sInf ts
{ continuous_inv :=
continuous_sInf_rng.2 fun t ht =>
continuous_sInf_dom ht (@ContinuousInv.continuous_inv G t _ (h t ht)) }
#align has_continuous_inv_Inf continuousInv_sInf
#align has_continuous_neg_Inf continuousNeg_sInf
@[to_additive]
theorem continuousInv_iInf {ts' : ι' → TopologicalSpace G}
(h' : ∀ i, @ContinuousInv G (ts' i) _) : @ContinuousInv G (⨅ i, ts' i) _ := by
rw [← sInf_range]
exact continuousInv_sInf (Set.forall_mem_range.mpr h')
#align has_continuous_inv_infi continuousInv_iInf
#align has_continuous_neg_infi continuousNeg_iInf
@[to_additive]
theorem continuousInv_inf {t₁ t₂ : TopologicalSpace G} (h₁ : @ContinuousInv G t₁ _)
(h₂ : @ContinuousInv G t₂ _) : @ContinuousInv G (t₁ ⊓ t₂) _ := by
rw [inf_eq_iInf]
refine continuousInv_iInf fun b => ?_
cases b <;> assumption
#align has_continuous_inv_inf continuousInv_inf
#align has_continuous_neg_inf continuousNeg_inf
end LatticeOps
@[to_additive]
theorem Inducing.continuousInv {G H : Type*} [Inv G] [Inv H] [TopologicalSpace G]
[TopologicalSpace H] [ContinuousInv H] {f : G → H} (hf : Inducing f)
(hf_inv : ∀ x, f x⁻¹ = (f x)⁻¹) : ContinuousInv G :=
⟨hf.continuous_iff.2 <| by simpa only [(· ∘ ·), hf_inv] using hf.continuous.inv⟩
#align inducing.has_continuous_inv Inducing.continuousInv
#align inducing.has_continuous_neg Inducing.continuousNeg
section TopologicalGroup
/-!
### Topological groups
A topological group is a group in which the multiplication and inversion operations are
continuous. Topological additive groups are defined in the same way. Equivalently, we can require
that the division operation `x y ↦ x * y⁻¹` (resp., subtraction) is continuous.
-/
-- Porting note (#11215): TODO should this docstring be extended
-- to match the multiplicative version?
/-- A topological (additive) group is a group in which the addition and negation operations are
continuous. -/
class TopologicalAddGroup (G : Type u) [TopologicalSpace G] [AddGroup G] extends
ContinuousAdd G, ContinuousNeg G : Prop
#align topological_add_group TopologicalAddGroup
/-- A topological group is a group in which the multiplication and inversion operations are
continuous.
When you declare an instance that does not already have a `UniformSpace` instance,
you should also provide an instance of `UniformSpace` and `UniformGroup` using
`TopologicalGroup.toUniformSpace` and `topologicalCommGroup_isUniform`. -/
-- Porting note: check that these ↑ names exist once they've been ported in the future.
@[to_additive]
class TopologicalGroup (G : Type*) [TopologicalSpace G] [Group G] extends ContinuousMul G,
ContinuousInv G : Prop
#align topological_group TopologicalGroup
--#align topological_add_group TopologicalAddGroup
section Conj
instance ConjAct.units_continuousConstSMul {M} [Monoid M] [TopologicalSpace M]
[ContinuousMul M] : ContinuousConstSMul (ConjAct Mˣ) M :=
⟨fun _ => (continuous_const.mul continuous_id).mul continuous_const⟩
#align conj_act.units_has_continuous_const_smul ConjAct.units_continuousConstSMul
variable [TopologicalSpace G] [Inv G] [Mul G] [ContinuousMul G]
/-- Conjugation is jointly continuous on `G × G` when both `mul` and `inv` are continuous. -/
@[to_additive
"Conjugation is jointly continuous on `G × G` when both `add` and `neg` are continuous."]
theorem TopologicalGroup.continuous_conj_prod [ContinuousInv G] :
Continuous fun g : G × G => g.fst * g.snd * g.fst⁻¹ :=
continuous_mul.mul (continuous_inv.comp continuous_fst)
#align topological_group.continuous_conj_prod TopologicalGroup.continuous_conj_prod
#align topological_add_group.continuous_conj_sum TopologicalAddGroup.continuous_conj_sum
/-- Conjugation by a fixed element is continuous when `mul` is continuous. -/
@[to_additive (attr := continuity)
"Conjugation by a fixed element is continuous when `add` is continuous."]
theorem TopologicalGroup.continuous_conj (g : G) : Continuous fun h : G => g * h * g⁻¹ :=
(continuous_mul_right g⁻¹).comp (continuous_mul_left g)
#align topological_group.continuous_conj TopologicalGroup.continuous_conj
#align topological_add_group.continuous_conj TopologicalAddGroup.continuous_conj
/-- Conjugation acting on fixed element of the group is continuous when both `mul` and
`inv` are continuous. -/
@[to_additive (attr := continuity)
"Conjugation acting on fixed element of the additive group is continuous when both
`add` and `neg` are continuous."]
theorem TopologicalGroup.continuous_conj' [ContinuousInv G] (h : G) :
Continuous fun g : G => g * h * g⁻¹ :=
(continuous_mul_right h).mul continuous_inv
#align topological_group.continuous_conj' TopologicalGroup.continuous_conj'
#align topological_add_group.continuous_conj' TopologicalAddGroup.continuous_conj'
end Conj
variable [TopologicalSpace G] [Group G] [TopologicalGroup G] [TopologicalSpace α] {f : α → G}
{s : Set α} {x : α}
instance : TopologicalGroup (ULift G) where
section ZPow
@[to_additive (attr := continuity)]
theorem continuous_zpow : ∀ z : ℤ, Continuous fun a : G => a ^ z
| Int.ofNat n => by simpa using continuous_pow n
| Int.negSucc n => by simpa using (continuous_pow (n + 1)).inv
#align continuous_zpow continuous_zpow
#align continuous_zsmul continuous_zsmul
instance AddGroup.continuousConstSMul_int {A} [AddGroup A] [TopologicalSpace A]
[TopologicalAddGroup A] : ContinuousConstSMul ℤ A :=
⟨continuous_zsmul⟩
#align add_group.has_continuous_const_smul_int AddGroup.continuousConstSMul_int
instance AddGroup.continuousSMul_int {A} [AddGroup A] [TopologicalSpace A]
[TopologicalAddGroup A] : ContinuousSMul ℤ A :=
⟨continuous_prod_of_discrete_left.mpr continuous_zsmul⟩
#align add_group.has_continuous_smul_int AddGroup.continuousSMul_int
@[to_additive (attr := continuity, fun_prop)]
theorem Continuous.zpow {f : α → G} (h : Continuous f) (z : ℤ) : Continuous fun b => f b ^ z :=
(continuous_zpow z).comp h
#align continuous.zpow Continuous.zpow
#align continuous.zsmul Continuous.zsmul
@[to_additive]
theorem continuousOn_zpow {s : Set G} (z : ℤ) : ContinuousOn (fun x => x ^ z) s :=
(continuous_zpow z).continuousOn
#align continuous_on_zpow continuousOn_zpow
#align continuous_on_zsmul continuousOn_zsmul
@[to_additive]
theorem continuousAt_zpow (x : G) (z : ℤ) : ContinuousAt (fun x => x ^ z) x :=
(continuous_zpow z).continuousAt
#align continuous_at_zpow continuousAt_zpow
#align continuous_at_zsmul continuousAt_zsmul
@[to_additive]
theorem Filter.Tendsto.zpow {α} {l : Filter α} {f : α → G} {x : G} (hf : Tendsto f l (𝓝 x))
(z : ℤ) : Tendsto (fun x => f x ^ z) l (𝓝 (x ^ z)) :=
(continuousAt_zpow _ _).tendsto.comp hf
#align filter.tendsto.zpow Filter.Tendsto.zpow
#align filter.tendsto.zsmul Filter.Tendsto.zsmul
@[to_additive]
theorem ContinuousWithinAt.zpow {f : α → G} {x : α} {s : Set α} (hf : ContinuousWithinAt f s x)
(z : ℤ) : ContinuousWithinAt (fun x => f x ^ z) s x :=
Filter.Tendsto.zpow hf z
#align continuous_within_at.zpow ContinuousWithinAt.zpow
#align continuous_within_at.zsmul ContinuousWithinAt.zsmul
@[to_additive (attr := fun_prop)]
theorem ContinuousAt.zpow {f : α → G} {x : α} (hf : ContinuousAt f x) (z : ℤ) :
ContinuousAt (fun x => f x ^ z) x :=
Filter.Tendsto.zpow hf z
#align continuous_at.zpow ContinuousAt.zpow
#align continuous_at.zsmul ContinuousAt.zsmul
@[to_additive (attr := fun_prop)]
theorem ContinuousOn.zpow {f : α → G} {s : Set α} (hf : ContinuousOn f s) (z : ℤ) :
ContinuousOn (fun x => f x ^ z) s := fun x hx => (hf x hx).zpow z
#align continuous_on.zpow ContinuousOn.zpow
#align continuous_on.zsmul ContinuousOn.zsmul
end ZPow
section OrderedCommGroup
variable [TopologicalSpace H] [OrderedCommGroup H] [ContinuousInv H]
@[to_additive]
theorem tendsto_inv_nhdsWithin_Ioi {a : H} : Tendsto Inv.inv (𝓝[>] a) (𝓝[<] a⁻¹) :=
(continuous_inv.tendsto a).inf <| by simp [tendsto_principal_principal]
#align tendsto_inv_nhds_within_Ioi tendsto_inv_nhdsWithin_Ioi
#align tendsto_neg_nhds_within_Ioi tendsto_neg_nhdsWithin_Ioi
@[to_additive]
theorem tendsto_inv_nhdsWithin_Iio {a : H} : Tendsto Inv.inv (𝓝[<] a) (𝓝[>] a⁻¹) :=
(continuous_inv.tendsto a).inf <| by simp [tendsto_principal_principal]
#align tendsto_inv_nhds_within_Iio tendsto_inv_nhdsWithin_Iio
#align tendsto_neg_nhds_within_Iio tendsto_neg_nhdsWithin_Iio
@[to_additive]
theorem tendsto_inv_nhdsWithin_Ioi_inv {a : H} : Tendsto Inv.inv (𝓝[>] a⁻¹) (𝓝[<] a) := by
simpa only [inv_inv] using @tendsto_inv_nhdsWithin_Ioi _ _ _ _ a⁻¹
#align tendsto_inv_nhds_within_Ioi_inv tendsto_inv_nhdsWithin_Ioi_inv
#align tendsto_neg_nhds_within_Ioi_neg tendsto_neg_nhdsWithin_Ioi_neg
@[to_additive]
theorem tendsto_inv_nhdsWithin_Iio_inv {a : H} : Tendsto Inv.inv (𝓝[<] a⁻¹) (𝓝[>] a) := by
simpa only [inv_inv] using @tendsto_inv_nhdsWithin_Iio _ _ _ _ a⁻¹
#align tendsto_inv_nhds_within_Iio_inv tendsto_inv_nhdsWithin_Iio_inv
#align tendsto_neg_nhds_within_Iio_neg tendsto_neg_nhdsWithin_Iio_neg
@[to_additive]
theorem tendsto_inv_nhdsWithin_Ici {a : H} : Tendsto Inv.inv (𝓝[≥] a) (𝓝[≤] a⁻¹) :=
(continuous_inv.tendsto a).inf <| by simp [tendsto_principal_principal]
#align tendsto_inv_nhds_within_Ici tendsto_inv_nhdsWithin_Ici
#align tendsto_neg_nhds_within_Ici tendsto_neg_nhdsWithin_Ici
@[to_additive]
theorem tendsto_inv_nhdsWithin_Iic {a : H} : Tendsto Inv.inv (𝓝[≤] a) (𝓝[≥] a⁻¹) :=
(continuous_inv.tendsto a).inf <| by simp [tendsto_principal_principal]
#align tendsto_inv_nhds_within_Iic tendsto_inv_nhdsWithin_Iic
#align tendsto_neg_nhds_within_Iic tendsto_neg_nhdsWithin_Iic
@[to_additive]
theorem tendsto_inv_nhdsWithin_Ici_inv {a : H} : Tendsto Inv.inv (𝓝[≥] a⁻¹) (𝓝[≤] a) := by
simpa only [inv_inv] using @tendsto_inv_nhdsWithin_Ici _ _ _ _ a⁻¹
#align tendsto_inv_nhds_within_Ici_inv tendsto_inv_nhdsWithin_Ici_inv
#align tendsto_neg_nhds_within_Ici_neg tendsto_neg_nhdsWithin_Ici_neg
@[to_additive]
theorem tendsto_inv_nhdsWithin_Iic_inv {a : H} : Tendsto Inv.inv (𝓝[≤] a⁻¹) (𝓝[≥] a) := by
simpa only [inv_inv] using @tendsto_inv_nhdsWithin_Iic _ _ _ _ a⁻¹
#align tendsto_inv_nhds_within_Iic_inv tendsto_inv_nhdsWithin_Iic_inv
#align tendsto_neg_nhds_within_Iic_neg tendsto_neg_nhdsWithin_Iic_neg
end OrderedCommGroup
@[to_additive]
instance [TopologicalSpace H] [Group H] [TopologicalGroup H] : TopologicalGroup (G × H) where
continuous_inv := continuous_inv.prod_map continuous_inv
@[to_additive]
instance Pi.topologicalGroup {C : β → Type*} [∀ b, TopologicalSpace (C b)] [∀ b, Group (C b)]
[∀ b, TopologicalGroup (C b)] : TopologicalGroup (∀ b, C b) where
continuous_inv := continuous_pi fun i => (continuous_apply i).inv
#align pi.topological_group Pi.topologicalGroup
#align pi.topological_add_group Pi.topologicalAddGroup
open MulOpposite
@[to_additive]
instance [Inv α] [ContinuousInv α] : ContinuousInv αᵐᵒᵖ :=
opHomeomorph.symm.inducing.continuousInv unop_inv
/-- If multiplication is continuous in `α`, then it also is in `αᵐᵒᵖ`. -/
@[to_additive "If addition is continuous in `α`, then it also is in `αᵃᵒᵖ`."]
instance [Group α] [TopologicalGroup α] : TopologicalGroup αᵐᵒᵖ where
variable (G)
@[to_additive]
theorem nhds_one_symm : comap Inv.inv (𝓝 (1 : G)) = 𝓝 (1 : G) :=
((Homeomorph.inv G).comap_nhds_eq _).trans (congr_arg nhds inv_one)
#align nhds_one_symm nhds_one_symm
#align nhds_zero_symm nhds_zero_symm
@[to_additive]
theorem nhds_one_symm' : map Inv.inv (𝓝 (1 : G)) = 𝓝 (1 : G) :=
((Homeomorph.inv G).map_nhds_eq _).trans (congr_arg nhds inv_one)
#align nhds_one_symm' nhds_one_symm'
#align nhds_zero_symm' nhds_zero_symm'
@[to_additive]
theorem inv_mem_nhds_one {S : Set G} (hS : S ∈ (𝓝 1 : Filter G)) : S⁻¹ ∈ 𝓝 (1 : G) := by
rwa [← nhds_one_symm'] at hS
#align inv_mem_nhds_one inv_mem_nhds_one
#align neg_mem_nhds_zero neg_mem_nhds_zero
/-- The map `(x, y) ↦ (x, x * y)` as a homeomorphism. This is a shear mapping. -/
@[to_additive "The map `(x, y) ↦ (x, x + y)` as a homeomorphism. This is a shear mapping."]
protected def Homeomorph.shearMulRight : G × G ≃ₜ G × G :=
{ Equiv.prodShear (Equiv.refl _) Equiv.mulLeft with
continuous_toFun := continuous_fst.prod_mk continuous_mul
continuous_invFun := continuous_fst.prod_mk <| continuous_fst.inv.mul continuous_snd }
#align homeomorph.shear_mul_right Homeomorph.shearMulRight
#align homeomorph.shear_add_right Homeomorph.shearAddRight
@[to_additive (attr := simp)]
theorem Homeomorph.shearMulRight_coe :
⇑(Homeomorph.shearMulRight G) = fun z : G × G => (z.1, z.1 * z.2) :=
rfl
#align homeomorph.shear_mul_right_coe Homeomorph.shearMulRight_coe
#align homeomorph.shear_add_right_coe Homeomorph.shearAddRight_coe
@[to_additive (attr := simp)]
theorem Homeomorph.shearMulRight_symm_coe :
⇑(Homeomorph.shearMulRight G).symm = fun z : G × G => (z.1, z.1⁻¹ * z.2) :=
rfl
#align homeomorph.shear_mul_right_symm_coe Homeomorph.shearMulRight_symm_coe
#align homeomorph.shear_add_right_symm_coe Homeomorph.shearAddRight_symm_coe
variable {G}
@[to_additive]
protected theorem Inducing.topologicalGroup {F : Type*} [Group H] [TopologicalSpace H]
[FunLike F H G] [MonoidHomClass F H G] (f : F) (hf : Inducing f) : TopologicalGroup H :=
{ toContinuousMul := hf.continuousMul _
toContinuousInv := hf.continuousInv (map_inv f) }
#align inducing.topological_group Inducing.topologicalGroup
#align inducing.topological_add_group Inducing.topologicalAddGroup
@[to_additive]
-- Porting note: removed `protected` (needs to be in namespace)
theorem topologicalGroup_induced {F : Type*} [Group H] [FunLike F H G] [MonoidHomClass F H G]
(f : F) :
@TopologicalGroup H (induced f ‹_›) _ :=
letI := induced f ‹_›
Inducing.topologicalGroup f ⟨rfl⟩
#align topological_group_induced topologicalGroup_induced
#align topological_add_group_induced topologicalAddGroup_induced
namespace Subgroup
@[to_additive]
instance (S : Subgroup G) : TopologicalGroup S :=
Inducing.topologicalGroup S.subtype inducing_subtype_val
end Subgroup
/-- The (topological-space) closure of a subgroup of a topological group is
itself a subgroup. -/
@[to_additive
"The (topological-space) closure of an additive subgroup of an additive topological group is
itself an additive subgroup."]
def Subgroup.topologicalClosure (s : Subgroup G) : Subgroup G :=
{ s.toSubmonoid.topologicalClosure with
carrier := _root_.closure (s : Set G)
inv_mem' := fun {g} hg => by simpa only [← Set.mem_inv, inv_closure, inv_coe_set] using hg }
#align subgroup.topological_closure Subgroup.topologicalClosure
#align add_subgroup.topological_closure AddSubgroup.topologicalClosure
@[to_additive (attr := simp)]
theorem Subgroup.topologicalClosure_coe {s : Subgroup G} :
(s.topologicalClosure : Set G) = _root_.closure s :=
rfl
#align subgroup.topological_closure_coe Subgroup.topologicalClosure_coe
#align add_subgroup.topological_closure_coe AddSubgroup.topologicalClosure_coe
@[to_additive]
theorem Subgroup.le_topologicalClosure (s : Subgroup G) : s ≤ s.topologicalClosure :=
_root_.subset_closure
#align subgroup.le_topological_closure Subgroup.le_topologicalClosure
#align add_subgroup.le_topological_closure AddSubgroup.le_topologicalClosure
@[to_additive]
theorem Subgroup.isClosed_topologicalClosure (s : Subgroup G) :
IsClosed (s.topologicalClosure : Set G) := isClosed_closure
#align subgroup.is_closed_topological_closure Subgroup.isClosed_topologicalClosure
#align add_subgroup.is_closed_topological_closure AddSubgroup.isClosed_topologicalClosure
@[to_additive]
theorem Subgroup.topologicalClosure_minimal (s : Subgroup G) {t : Subgroup G} (h : s ≤ t)
(ht : IsClosed (t : Set G)) : s.topologicalClosure ≤ t :=
closure_minimal h ht
#align subgroup.topological_closure_minimal Subgroup.topologicalClosure_minimal
#align add_subgroup.topological_closure_minimal AddSubgroup.topologicalClosure_minimal
@[to_additive]
theorem DenseRange.topologicalClosure_map_subgroup [Group H] [TopologicalSpace H]
[TopologicalGroup H] {f : G →* H} (hf : Continuous f) (hf' : DenseRange f) {s : Subgroup G}
(hs : s.topologicalClosure = ⊤) : (s.map f).topologicalClosure = ⊤ := by
rw [SetLike.ext'_iff] at hs ⊢
simp only [Subgroup.topologicalClosure_coe, Subgroup.coe_top, ← dense_iff_closure_eq] at hs ⊢
exact hf'.dense_image hf hs
#align dense_range.topological_closure_map_subgroup DenseRange.topologicalClosure_map_subgroup
#align dense_range.topological_closure_map_add_subgroup DenseRange.topologicalClosure_map_addSubgroup
/-- The topological closure of a normal subgroup is normal. -/
@[to_additive "The topological closure of a normal additive subgroup is normal."]
theorem Subgroup.is_normal_topologicalClosure {G : Type*} [TopologicalSpace G] [Group G]
[TopologicalGroup G] (N : Subgroup G) [N.Normal] : (Subgroup.topologicalClosure N).Normal where
conj_mem n hn g := by
apply map_mem_closure (TopologicalGroup.continuous_conj g) hn
exact fun m hm => Subgroup.Normal.conj_mem inferInstance m hm g
#align subgroup.is_normal_topological_closure Subgroup.is_normal_topologicalClosure
#align add_subgroup.is_normal_topological_closure AddSubgroup.is_normal_topologicalClosure
@[to_additive]
theorem mul_mem_connectedComponent_one {G : Type*} [TopologicalSpace G] [MulOneClass G]
[ContinuousMul G] {g h : G} (hg : g ∈ connectedComponent (1 : G))
(hh : h ∈ connectedComponent (1 : G)) : g * h ∈ connectedComponent (1 : G) := by
rw [connectedComponent_eq hg]
have hmul : g ∈ connectedComponent (g * h) := by
apply Continuous.image_connectedComponent_subset (continuous_mul_left g)
rw [← connectedComponent_eq hh]
exact ⟨(1 : G), mem_connectedComponent, by simp only [mul_one]⟩
simpa [← connectedComponent_eq hmul] using mem_connectedComponent
#align mul_mem_connected_component_one mul_mem_connectedComponent_one
#align add_mem_connected_component_zero add_mem_connectedComponent_zero
@[to_additive]
theorem inv_mem_connectedComponent_one {G : Type*} [TopologicalSpace G] [Group G]
[TopologicalGroup G] {g : G} (hg : g ∈ connectedComponent (1 : G)) :
g⁻¹ ∈ connectedComponent (1 : G) := by
rw [← inv_one]
exact
Continuous.image_connectedComponent_subset continuous_inv _
((Set.mem_image _ _ _).mp ⟨g, hg, rfl⟩)
#align inv_mem_connected_component_one inv_mem_connectedComponent_one
#align neg_mem_connected_component_zero neg_mem_connectedComponent_zero
/-- The connected component of 1 is a subgroup of `G`. -/
@[to_additive "The connected component of 0 is a subgroup of `G`."]
def Subgroup.connectedComponentOfOne (G : Type*) [TopologicalSpace G] [Group G]
[TopologicalGroup G] : Subgroup G where
carrier := connectedComponent (1 : G)
one_mem' := mem_connectedComponent
mul_mem' hg hh := mul_mem_connectedComponent_one hg hh
inv_mem' hg := inv_mem_connectedComponent_one hg
#align subgroup.connected_component_of_one Subgroup.connectedComponentOfOne
#align add_subgroup.connected_component_of_zero AddSubgroup.connectedComponentOfZero
/-- If a subgroup of a topological group is commutative, then so is its topological closure. -/
@[to_additive
"If a subgroup of an additive topological group is commutative, then so is its
topological closure."]
def Subgroup.commGroupTopologicalClosure [T2Space G] (s : Subgroup G)
(hs : ∀ x y : s, x * y = y * x) : CommGroup s.topologicalClosure :=
{ s.topologicalClosure.toGroup, s.toSubmonoid.commMonoidTopologicalClosure hs with }
#align subgroup.comm_group_topological_closure Subgroup.commGroupTopologicalClosure
#align add_subgroup.add_comm_group_topological_closure AddSubgroup.addCommGroupTopologicalClosure
variable (G) in
@[to_additive]
lemma Subgroup.coe_topologicalClosure_bot :
((⊥ : Subgroup G).topologicalClosure : Set G) = _root_.closure ({1} : Set G) := by simp
@[to_additive exists_nhds_half_neg]
theorem exists_nhds_split_inv {s : Set G} (hs : s ∈ 𝓝 (1 : G)) :
∃ V ∈ 𝓝 (1 : G), ∀ v ∈ V, ∀ w ∈ V, v / w ∈ s := by
have : (fun p : G × G => p.1 * p.2⁻¹) ⁻¹' s ∈ 𝓝 ((1, 1) : G × G) :=
continuousAt_fst.mul continuousAt_snd.inv (by simpa)
simpa only [div_eq_mul_inv, nhds_prod_eq, mem_prod_self_iff, prod_subset_iff, mem_preimage] using
this
#align exists_nhds_split_inv exists_nhds_split_inv
#align exists_nhds_half_neg exists_nhds_half_neg
@[to_additive]
theorem nhds_translation_mul_inv (x : G) : comap (· * x⁻¹) (𝓝 1) = 𝓝 x :=
((Homeomorph.mulRight x⁻¹).comap_nhds_eq 1).trans <| show 𝓝 (1 * x⁻¹⁻¹) = 𝓝 x by simp
#align nhds_translation_mul_inv nhds_translation_mul_inv
#align nhds_translation_add_neg nhds_translation_add_neg
@[to_additive (attr := simp)]
theorem map_mul_left_nhds (x y : G) : map (x * ·) (𝓝 y) = 𝓝 (x * y) :=
(Homeomorph.mulLeft x).map_nhds_eq y
#align map_mul_left_nhds map_mul_left_nhds
#align map_add_left_nhds map_add_left_nhds
@[to_additive]
| Mathlib/Topology/Algebra/Group/Basic.lean | 859 | 859 | theorem map_mul_left_nhds_one (x : G) : map (x * ·) (𝓝 1) = 𝓝 x := by | simp
|
/-
Copyright (c) 2020 Nicolò Cavalleri. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Nicolò Cavalleri
-/
import Mathlib.Geometry.Manifold.Algebra.Monoid
#align_import geometry.manifold.algebra.lie_group from "leanprover-community/mathlib"@"f9ec187127cc5b381dfcf5f4a22dacca4c20b63d"
/-!
# Lie groups
A Lie group is a group that is also a smooth manifold, in which the group operations of
multiplication and inversion are smooth maps. Smoothness of the group multiplication means that
multiplication is a smooth mapping of the product manifold `G` × `G` into `G`.
Note that, since a manifold here is not second-countable and Hausdorff a Lie group here is not
guaranteed to be second-countable (even though it can be proved it is Hausdorff). Note also that Lie
groups here are not necessarily finite dimensional.
## Main definitions
* `LieAddGroup I G` : a Lie additive group where `G` is a manifold on the model with corners `I`.
* `LieGroup I G` : a Lie multiplicative group where `G` is a manifold on the model with corners `I`.
* `SmoothInv₀`: typeclass for smooth manifolds with `0` and `Inv` such that inversion is a smooth
map at each non-zero point. This includes complete normed fields and (multiplicative) Lie groups.
## Main results
* `ContMDiff.inv`, `ContMDiff.div` and variants: point-wise inversion and division of maps `M → G`
is smooth
* `ContMDiff.inv₀` and variants: if `SmoothInv₀ N`, point-wise inversion of smooth maps `f : M → N`
is smooth at all points at which `f` doesn't vanish.
* `ContMDiff.div₀` and variants: if also `SmoothMul N` (i.e., `N` is a Lie group except possibly
for smoothness of inversion at `0`), similar results hold for point-wise division.
* `normedSpaceLieAddGroup` : a normed vector space over a nontrivially normed field
is an additive Lie group.
* `Instances/UnitsOfNormedAlgebra` shows that the group of units of a complete normed `𝕜`-algebra
is a multiplicative Lie group.
## Implementation notes
A priori, a Lie group here is a manifold with corners.
The definition of Lie group cannot require `I : ModelWithCorners 𝕜 E E` with the same space as the
model space and as the model vector space, as one might hope, beause in the product situation,
the model space is `ModelProd E E'` and the model vector space is `E × E'`, which are not the same,
so the definition does not apply. Hence the definition should be more general, allowing
`I : ModelWithCorners 𝕜 E H`.
-/
noncomputable section
open scoped Manifold
-- See note [Design choices about smooth algebraic structures]
/-- An additive Lie group is a group and a smooth manifold at the same time in which
the addition and negation operations are smooth. -/
class LieAddGroup {𝕜 : Type*} [NontriviallyNormedField 𝕜] {H : Type*} [TopologicalSpace H]
{E : Type*} [NormedAddCommGroup E] [NormedSpace 𝕜 E] (I : ModelWithCorners 𝕜 E H) (G : Type*)
[AddGroup G] [TopologicalSpace G] [ChartedSpace H G] extends SmoothAdd I G : Prop where
/-- Negation is smooth in an additive Lie group. -/
smooth_neg : Smooth I I fun a : G => -a
#align lie_add_group LieAddGroup
-- See note [Design choices about smooth algebraic structures]
/-- A (multiplicative) Lie group is a group and a smooth manifold at the same time in which
the multiplication and inverse operations are smooth. -/
@[to_additive]
class LieGroup {𝕜 : Type*} [NontriviallyNormedField 𝕜] {H : Type*} [TopologicalSpace H]
{E : Type*} [NormedAddCommGroup E] [NormedSpace 𝕜 E] (I : ModelWithCorners 𝕜 E H) (G : Type*)
[Group G] [TopologicalSpace G] [ChartedSpace H G] extends SmoothMul I G : Prop where
/-- Inversion is smooth in a Lie group. -/
smooth_inv : Smooth I I fun a : G => a⁻¹
#align lie_group LieGroup
/-!
### Smoothness of inversion, negation, division and subtraction
Let `f : M → G` be a `C^n` or smooth functions into a Lie group, then `f` is point-wise
invertible with smooth inverse `f`. If `f` and `g` are two such functions, the quotient
`f / g` (i.e., the point-wise product of `f` and the point-wise inverse of `g`) is also smooth. -/
section PointwiseDivision
variable {𝕜 : Type*} [NontriviallyNormedField 𝕜] {H : Type*} [TopologicalSpace H] {E : Type*}
[NormedAddCommGroup E] [NormedSpace 𝕜 E] {I : ModelWithCorners 𝕜 E H} {F : Type*}
[NormedAddCommGroup F] [NormedSpace 𝕜 F] {J : ModelWithCorners 𝕜 F F} {G : Type*}
[TopologicalSpace G] [ChartedSpace H G] [Group G] [LieGroup I G] {E' : Type*}
[NormedAddCommGroup E'] [NormedSpace 𝕜 E'] {H' : Type*} [TopologicalSpace H']
{I' : ModelWithCorners 𝕜 E' H'} {M : Type*} [TopologicalSpace M] [ChartedSpace H' M]
{E'' : Type*} [NormedAddCommGroup E''] [NormedSpace 𝕜 E''] {H'' : Type*} [TopologicalSpace H'']
{I'' : ModelWithCorners 𝕜 E'' H''} {M' : Type*} [TopologicalSpace M'] [ChartedSpace H'' M']
{n : ℕ∞}
section
variable (I)
/-- In a Lie group, inversion is a smooth map. -/
@[to_additive "In an additive Lie group, inversion is a smooth map."]
theorem smooth_inv : Smooth I I fun x : G => x⁻¹ :=
LieGroup.smooth_inv
#align smooth_inv smooth_inv
#align smooth_neg smooth_neg
/-- A Lie group is a topological group. This is not an instance for technical reasons,
see note [Design choices about smooth algebraic structures]. -/
@[to_additive "An additive Lie group is an additive topological group. This is not an instance for
technical reasons, see note [Design choices about smooth algebraic structures]."]
theorem topologicalGroup_of_lieGroup : TopologicalGroup G :=
{ continuousMul_of_smooth I with continuous_inv := (smooth_inv I).continuous }
#align topological_group_of_lie_group topologicalGroup_of_lieGroup
#align topological_add_group_of_lie_add_group topologicalAddGroup_of_lieAddGroup
end
@[to_additive]
theorem ContMDiffWithinAt.inv {f : M → G} {s : Set M} {x₀ : M}
(hf : ContMDiffWithinAt I' I n f s x₀) : ContMDiffWithinAt I' I n (fun x => (f x)⁻¹) s x₀ :=
((smooth_inv I).of_le le_top).contMDiffAt.contMDiffWithinAt.comp x₀ hf <| Set.mapsTo_univ _ _
#align cont_mdiff_within_at.inv ContMDiffWithinAt.inv
#align cont_mdiff_within_at.neg ContMDiffWithinAt.neg
@[to_additive]
theorem ContMDiffAt.inv {f : M → G} {x₀ : M} (hf : ContMDiffAt I' I n f x₀) :
ContMDiffAt I' I n (fun x => (f x)⁻¹) x₀ :=
((smooth_inv I).of_le le_top).contMDiffAt.comp x₀ hf
#align cont_mdiff_at.inv ContMDiffAt.inv
#align cont_mdiff_at.neg ContMDiffAt.neg
@[to_additive]
theorem ContMDiffOn.inv {f : M → G} {s : Set M} (hf : ContMDiffOn I' I n f s) :
ContMDiffOn I' I n (fun x => (f x)⁻¹) s := fun x hx => (hf x hx).inv
#align cont_mdiff_on.inv ContMDiffOn.inv
#align cont_mdiff_on.neg ContMDiffOn.neg
@[to_additive]
theorem ContMDiff.inv {f : M → G} (hf : ContMDiff I' I n f) : ContMDiff I' I n fun x => (f x)⁻¹ :=
fun x => (hf x).inv
#align cont_mdiff.inv ContMDiff.inv
#align cont_mdiff.neg ContMDiff.neg
@[to_additive]
nonrec theorem SmoothWithinAt.inv {f : M → G} {s : Set M} {x₀ : M}
(hf : SmoothWithinAt I' I f s x₀) : SmoothWithinAt I' I (fun x => (f x)⁻¹) s x₀ :=
hf.inv
#align smooth_within_at.inv SmoothWithinAt.inv
#align smooth_within_at.neg SmoothWithinAt.neg
@[to_additive]
nonrec theorem SmoothAt.inv {f : M → G} {x₀ : M} (hf : SmoothAt I' I f x₀) :
SmoothAt I' I (fun x => (f x)⁻¹) x₀ :=
hf.inv
#align smooth_at.inv SmoothAt.inv
#align smooth_at.neg SmoothAt.neg
@[to_additive]
nonrec theorem SmoothOn.inv {f : M → G} {s : Set M} (hf : SmoothOn I' I f s) :
SmoothOn I' I (fun x => (f x)⁻¹) s :=
hf.inv
#align smooth_on.inv SmoothOn.inv
#align smooth_on.neg SmoothOn.neg
@[to_additive]
nonrec theorem Smooth.inv {f : M → G} (hf : Smooth I' I f) : Smooth I' I fun x => (f x)⁻¹ :=
hf.inv
#align smooth.inv Smooth.inv
#align smooth.neg Smooth.neg
@[to_additive]
theorem ContMDiffWithinAt.div {f g : M → G} {s : Set M} {x₀ : M}
(hf : ContMDiffWithinAt I' I n f s x₀) (hg : ContMDiffWithinAt I' I n g s x₀) :
ContMDiffWithinAt I' I n (fun x => f x / g x) s x₀ := by
simp_rw [div_eq_mul_inv]; exact hf.mul hg.inv
#align cont_mdiff_within_at.div ContMDiffWithinAt.div
#align cont_mdiff_within_at.sub ContMDiffWithinAt.sub
@[to_additive]
theorem ContMDiffAt.div {f g : M → G} {x₀ : M} (hf : ContMDiffAt I' I n f x₀)
(hg : ContMDiffAt I' I n g x₀) : ContMDiffAt I' I n (fun x => f x / g x) x₀ := by
simp_rw [div_eq_mul_inv]; exact hf.mul hg.inv
#align cont_mdiff_at.div ContMDiffAt.div
#align cont_mdiff_at.sub ContMDiffAt.sub
@[to_additive]
theorem ContMDiffOn.div {f g : M → G} {s : Set M} (hf : ContMDiffOn I' I n f s)
(hg : ContMDiffOn I' I n g s) : ContMDiffOn I' I n (fun x => f x / g x) s := by
simp_rw [div_eq_mul_inv]; exact hf.mul hg.inv
#align cont_mdiff_on.div ContMDiffOn.div
#align cont_mdiff_on.sub ContMDiffOn.sub
@[to_additive]
theorem ContMDiff.div {f g : M → G} (hf : ContMDiff I' I n f) (hg : ContMDiff I' I n g) :
ContMDiff I' I n fun x => f x / g x := by simp_rw [div_eq_mul_inv]; exact hf.mul hg.inv
#align cont_mdiff.div ContMDiff.div
#align cont_mdiff.sub ContMDiff.sub
@[to_additive]
nonrec theorem SmoothWithinAt.div {f g : M → G} {s : Set M} {x₀ : M}
(hf : SmoothWithinAt I' I f s x₀) (hg : SmoothWithinAt I' I g s x₀) :
SmoothWithinAt I' I (fun x => f x / g x) s x₀ :=
hf.div hg
#align smooth_within_at.div SmoothWithinAt.div
#align smooth_within_at.sub SmoothWithinAt.sub
@[to_additive]
nonrec theorem SmoothAt.div {f g : M → G} {x₀ : M} (hf : SmoothAt I' I f x₀)
(hg : SmoothAt I' I g x₀) : SmoothAt I' I (fun x => f x / g x) x₀ :=
hf.div hg
#align smooth_at.div SmoothAt.div
#align smooth_at.sub SmoothAt.sub
@[to_additive]
nonrec theorem SmoothOn.div {f g : M → G} {s : Set M} (hf : SmoothOn I' I f s)
(hg : SmoothOn I' I g s) : SmoothOn I' I (f / g) s :=
hf.div hg
#align smooth_on.div SmoothOn.div
#align smooth_on.sub SmoothOn.sub
@[to_additive]
nonrec theorem Smooth.div {f g : M → G} (hf : Smooth I' I f) (hg : Smooth I' I g) :
Smooth I' I (f / g) :=
hf.div hg
#align smooth.div Smooth.div
#align smooth.sub Smooth.sub
end PointwiseDivision
/-! Binary product of Lie groups -/
section Product
-- Instance of product group
@[to_additive]
instance {𝕜 : Type*} [NontriviallyNormedField 𝕜] {H : Type*} [TopologicalSpace H] {E : Type*}
[NormedAddCommGroup E] [NormedSpace 𝕜 E] {I : ModelWithCorners 𝕜 E H} {G : Type*}
[TopologicalSpace G] [ChartedSpace H G] [Group G] [LieGroup I G] {E' : Type*}
[NormedAddCommGroup E'] [NormedSpace 𝕜 E'] {H' : Type*} [TopologicalSpace H']
{I' : ModelWithCorners 𝕜 E' H'} {G' : Type*} [TopologicalSpace G'] [ChartedSpace H' G']
[Group G'] [LieGroup I' G'] : LieGroup (I.prod I') (G × G') :=
{ SmoothMul.prod _ _ _ _ with smooth_inv := smooth_fst.inv.prod_mk smooth_snd.inv }
end Product
/-! ### Normed spaces are Lie groups -/
instance normedSpaceLieAddGroup {𝕜 : Type*} [NontriviallyNormedField 𝕜] {E : Type*}
[NormedAddCommGroup E] [NormedSpace 𝕜 E] : LieAddGroup 𝓘(𝕜, E) E where
smooth_neg := contDiff_neg.contMDiff
#align normed_space_lie_add_group normedSpaceLieAddGroup
/-! ## Smooth manifolds with smooth inversion away from zero
Typeclass for smooth manifolds with `0` and `Inv` such that inversion is smooth at all non-zero
points. (This includes multiplicative Lie groups, but also complete normed semifields.)
Point-wise inversion is smooth when the function/denominator is non-zero. -/
section SmoothInv₀
-- See note [Design choices about smooth algebraic structures]
/-- A smooth manifold with `0` and `Inv` such that `fun x ↦ x⁻¹` is smooth at all nonzero points.
Any complete normed (semi)field has this property. -/
class SmoothInv₀ {𝕜 : Type*} [NontriviallyNormedField 𝕜] {H : Type*} [TopologicalSpace H]
{E : Type*} [NormedAddCommGroup E] [NormedSpace 𝕜 E] (I : ModelWithCorners 𝕜 E H) (G : Type*)
[Inv G] [Zero G] [TopologicalSpace G] [ChartedSpace H G] : Prop where
/-- Inversion is smooth away from `0`. -/
smoothAt_inv₀ : ∀ ⦃x : G⦄, x ≠ 0 → SmoothAt I I (fun y ↦ y⁻¹) x
instance {𝕜 : Type*} [NontriviallyNormedField 𝕜] [CompleteSpace 𝕜] : SmoothInv₀ 𝓘(𝕜) 𝕜 :=
{ smoothAt_inv₀ := by
intro x hx
change ContMDiffAt 𝓘(𝕜) 𝓘(𝕜) ⊤ Inv.inv x
rw [contMDiffAt_iff_contDiffAt]
exact contDiffAt_inv 𝕜 hx }
variable {𝕜 : Type*} [NontriviallyNormedField 𝕜] {H : Type*} [TopologicalSpace H] {E : Type*}
[NormedAddCommGroup E] [NormedSpace 𝕜 E] (I : ModelWithCorners 𝕜 E H) {G : Type*}
[TopologicalSpace G] [ChartedSpace H G] [Inv G] [Zero G] [SmoothInv₀ I G] {E' : Type*}
[NormedAddCommGroup E'] [NormedSpace 𝕜 E'] {H' : Type*} [TopologicalSpace H']
{I' : ModelWithCorners 𝕜 E' H'} {M : Type*} [TopologicalSpace M] [ChartedSpace H' M]
{n : ℕ∞} {f g : M → G}
theorem smoothAt_inv₀ {x : G} (hx : x ≠ 0) : SmoothAt I I (fun y ↦ y⁻¹) x :=
SmoothInv₀.smoothAt_inv₀ hx
/-- In a manifold with smooth inverse away from `0`, the inverse is continuous away from `0`.
This is not an instance for technical reasons, see
note [Design choices about smooth algebraic structures]. -/
theorem hasContinuousInv₀_of_hasSmoothInv₀ : HasContinuousInv₀ G :=
{ continuousAt_inv₀ := fun _ hx ↦ (smoothAt_inv₀ I hx).continuousAt }
theorem SmoothOn_inv₀ : SmoothOn I I (Inv.inv : G → G) {0}ᶜ := fun _x hx =>
(smoothAt_inv₀ I hx).smoothWithinAt
variable {I} {s : Set M} {a : M}
theorem ContMDiffWithinAt.inv₀ (hf : ContMDiffWithinAt I' I n f s a) (ha : f a ≠ 0) :
ContMDiffWithinAt I' I n (fun x => (f x)⁻¹) s a :=
(smoothAt_inv₀ I ha).contMDiffAt.comp_contMDiffWithinAt a hf
theorem ContMDiffAt.inv₀ (hf : ContMDiffAt I' I n f a) (ha : f a ≠ 0) :
ContMDiffAt I' I n (fun x ↦ (f x)⁻¹) a :=
(smoothAt_inv₀ I ha).contMDiffAt.comp a hf
theorem ContMDiff.inv₀ (hf : ContMDiff I' I n f) (h0 : ∀ x, f x ≠ 0) :
ContMDiff I' I n (fun x ↦ (f x)⁻¹) :=
fun x ↦ ContMDiffAt.inv₀ (hf x) (h0 x)
theorem ContMDiffOn.inv₀ (hf : ContMDiffOn I' I n f s) (h0 : ∀ x ∈ s, f x ≠ 0) :
ContMDiffOn I' I n (fun x => (f x)⁻¹) s :=
fun x hx ↦ ContMDiffWithinAt.inv₀ (hf x hx) (h0 x hx)
theorem SmoothWithinAt.inv₀ (hf : SmoothWithinAt I' I f s a) (ha : f a ≠ 0) :
SmoothWithinAt I' I (fun x => (f x)⁻¹) s a :=
ContMDiffWithinAt.inv₀ hf ha
theorem SmoothAt.inv₀ (hf : SmoothAt I' I f a) (ha : f a ≠ 0) :
SmoothAt I' I (fun x => (f x)⁻¹) a :=
ContMDiffAt.inv₀ hf ha
theorem Smooth.inv₀ (hf : Smooth I' I f) (h0 : ∀ x, f x ≠ 0) : Smooth I' I fun x => (f x)⁻¹ :=
ContMDiff.inv₀ hf h0
theorem SmoothOn.inv₀ (hf : SmoothOn I' I f s) (h0 : ∀ x ∈ s, f x ≠ 0) :
SmoothOn I' I (fun x => (f x)⁻¹) s :=
ContMDiffOn.inv₀ hf h0
end SmoothInv₀
/-! ### Point-wise division of smooth functions
If `[SmoothMul I N]` and `[SmoothInv₀ I N]`, point-wise division of smooth functions `f : M → N`
is smooth whenever the denominator is non-zero. (This includes `N` being a completely normed field.)
-/
section Div
variable {𝕜 : Type*} [NontriviallyNormedField 𝕜] {H : Type*} [TopologicalSpace H] {E : Type*}
[NormedAddCommGroup E] [NormedSpace 𝕜 E] {I : ModelWithCorners 𝕜 E H} {G : Type*}
[TopologicalSpace G] [ChartedSpace H G] [GroupWithZero G] [SmoothInv₀ I G] [SmoothMul I G]
{E' : Type*} [NormedAddCommGroup E'] [NormedSpace 𝕜 E'] {H' : Type*} [TopologicalSpace H']
{I' : ModelWithCorners 𝕜 E' H'} {M : Type*} [TopologicalSpace M] [ChartedSpace H' M]
{f g : M → G} {s : Set M} {a : M} {n : ℕ∞}
theorem ContMDiffWithinAt.div₀
(hf : ContMDiffWithinAt I' I n f s a) (hg : ContMDiffWithinAt I' I n g s a) (h₀ : g a ≠ 0) :
ContMDiffWithinAt I' I n (f / g) s a := by
simpa [div_eq_mul_inv] using hf.mul (hg.inv₀ h₀)
| Mathlib/Geometry/Manifold/Algebra/LieGroup.lean | 347 | 349 | theorem ContMDiffOn.div₀ (hf : ContMDiffOn I' I n f s) (hg : ContMDiffOn I' I n g s)
(h₀ : ∀ x ∈ s, g x ≠ 0) : ContMDiffOn I' I n (f / g) s := by |
simpa [div_eq_mul_inv] using hf.mul (hg.inv₀ h₀)
|
/-
Copyright (c) 2015 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro
-/
import Mathlib.Data.List.Range
import Mathlib.Data.Multiset.Range
#align_import data.multiset.nodup from "leanprover-community/mathlib"@"f694c7dead66f5d4c80f446c796a5aad14707f0e"
/-!
# The `Nodup` predicate for multisets without duplicate elements.
-/
namespace Multiset
open Function List
variable {α β γ : Type*} {r : α → α → Prop} {s t : Multiset α} {a : α}
-- nodup
/-- `Nodup s` means that `s` has no duplicates, i.e. the multiplicity of
any element is at most 1. -/
def Nodup (s : Multiset α) : Prop :=
Quot.liftOn s List.Nodup fun _ _ p => propext p.nodup_iff
#align multiset.nodup Multiset.Nodup
@[simp]
theorem coe_nodup {l : List α} : @Nodup α l ↔ l.Nodup :=
Iff.rfl
#align multiset.coe_nodup Multiset.coe_nodup
@[simp]
theorem nodup_zero : @Nodup α 0 :=
Pairwise.nil
#align multiset.nodup_zero Multiset.nodup_zero
@[simp]
theorem nodup_cons {a : α} {s : Multiset α} : Nodup (a ::ₘ s) ↔ a ∉ s ∧ Nodup s :=
Quot.induction_on s fun _ => List.nodup_cons
#align multiset.nodup_cons Multiset.nodup_cons
theorem Nodup.cons (m : a ∉ s) (n : Nodup s) : Nodup (a ::ₘ s) :=
nodup_cons.2 ⟨m, n⟩
#align multiset.nodup.cons Multiset.Nodup.cons
@[simp]
theorem nodup_singleton : ∀ a : α, Nodup ({a} : Multiset α) :=
List.nodup_singleton
#align multiset.nodup_singleton Multiset.nodup_singleton
theorem Nodup.of_cons (h : Nodup (a ::ₘ s)) : Nodup s :=
(nodup_cons.1 h).2
#align multiset.nodup.of_cons Multiset.Nodup.of_cons
theorem Nodup.not_mem (h : Nodup (a ::ₘ s)) : a ∉ s :=
(nodup_cons.1 h).1
#align multiset.nodup.not_mem Multiset.Nodup.not_mem
theorem nodup_of_le {s t : Multiset α} (h : s ≤ t) : Nodup t → Nodup s :=
Multiset.leInductionOn h fun {_ _} => Nodup.sublist
#align multiset.nodup_of_le Multiset.nodup_of_le
theorem not_nodup_pair : ∀ a : α, ¬Nodup (a ::ₘ a ::ₘ 0) :=
List.not_nodup_pair
#align multiset.not_nodup_pair Multiset.not_nodup_pair
theorem nodup_iff_le {s : Multiset α} : Nodup s ↔ ∀ a : α, ¬a ::ₘ a ::ₘ 0 ≤ s :=
Quot.induction_on s fun _ =>
nodup_iff_sublist.trans <| forall_congr' fun a => not_congr (@replicate_le_coe _ a 2 _).symm
#align multiset.nodup_iff_le Multiset.nodup_iff_le
theorem nodup_iff_ne_cons_cons {s : Multiset α} : s.Nodup ↔ ∀ a t, s ≠ a ::ₘ a ::ₘ t :=
nodup_iff_le.trans
⟨fun h a t s_eq => h a (s_eq.symm ▸ cons_le_cons a (cons_le_cons a (zero_le _))), fun h a le =>
let ⟨t, s_eq⟩ := le_iff_exists_add.mp le
h a t (by rwa [cons_add, cons_add, zero_add] at s_eq)⟩
#align multiset.nodup_iff_ne_cons_cons Multiset.nodup_iff_ne_cons_cons
theorem nodup_iff_count_le_one [DecidableEq α] {s : Multiset α} : Nodup s ↔ ∀ a, count a s ≤ 1 :=
Quot.induction_on s fun _l => by
simp only [quot_mk_to_coe'', coe_nodup, mem_coe, coe_count]
exact List.nodup_iff_count_le_one
#align multiset.nodup_iff_count_le_one Multiset.nodup_iff_count_le_one
theorem nodup_iff_count_eq_one [DecidableEq α] : Nodup s ↔ ∀ a ∈ s, count a s = 1 :=
Quot.induction_on s fun _l => by simpa using List.nodup_iff_count_eq_one
@[simp]
theorem count_eq_one_of_mem [DecidableEq α] {a : α} {s : Multiset α} (d : Nodup s) (h : a ∈ s) :
count a s = 1 :=
nodup_iff_count_eq_one.mp d a h
#align multiset.count_eq_one_of_mem Multiset.count_eq_one_of_mem
theorem count_eq_of_nodup [DecidableEq α] {a : α} {s : Multiset α} (d : Nodup s) :
count a s = if a ∈ s then 1 else 0 := by
split_ifs with h
· exact count_eq_one_of_mem d h
· exact count_eq_zero_of_not_mem h
#align multiset.count_eq_of_nodup Multiset.count_eq_of_nodup
theorem nodup_iff_pairwise {α} {s : Multiset α} : Nodup s ↔ Pairwise (· ≠ ·) s :=
Quotient.inductionOn s fun _ => (pairwise_coe_iff_pairwise fun _ _ => Ne.symm).symm
#align multiset.nodup_iff_pairwise Multiset.nodup_iff_pairwise
protected theorem Nodup.pairwise : (∀ a ∈ s, ∀ b ∈ s, a ≠ b → r a b) → Nodup s → Pairwise r s :=
Quotient.inductionOn s fun l h hl => ⟨l, rfl, hl.imp_of_mem fun {a b} ha hb => h a ha b hb⟩
#align multiset.nodup.pairwise Multiset.Nodup.pairwise
theorem Pairwise.forall (H : Symmetric r) (hs : Pairwise r s) :
∀ ⦃a⦄, a ∈ s → ∀ ⦃b⦄, b ∈ s → a ≠ b → r a b :=
let ⟨_, hl₁, hl₂⟩ := hs
hl₁.symm ▸ hl₂.forall H
#align multiset.pairwise.forall Multiset.Pairwise.forall
theorem nodup_add {s t : Multiset α} : Nodup (s + t) ↔ Nodup s ∧ Nodup t ∧ Disjoint s t :=
Quotient.inductionOn₂ s t fun _ _ => nodup_append
#align multiset.nodup_add Multiset.nodup_add
theorem disjoint_of_nodup_add {s t : Multiset α} (d : Nodup (s + t)) : Disjoint s t :=
(nodup_add.1 d).2.2
#align multiset.disjoint_of_nodup_add Multiset.disjoint_of_nodup_add
theorem Nodup.add_iff (d₁ : Nodup s) (d₂ : Nodup t) : Nodup (s + t) ↔ Disjoint s t := by
simp [nodup_add, d₁, d₂]
#align multiset.nodup.add_iff Multiset.Nodup.add_iff
theorem Nodup.of_map (f : α → β) : Nodup (map f s) → Nodup s :=
Quot.induction_on s fun _ => List.Nodup.of_map f
#align multiset.nodup.of_map Multiset.Nodup.of_map
theorem Nodup.map_on {f : α → β} :
(∀ x ∈ s, ∀ y ∈ s, f x = f y → x = y) → Nodup s → Nodup (map f s) :=
Quot.induction_on s fun _ => List.Nodup.map_on
#align multiset.nodup.map_on Multiset.Nodup.map_on
theorem Nodup.map {f : α → β} {s : Multiset α} (hf : Injective f) : Nodup s → Nodup (map f s) :=
Nodup.map_on fun _ _ _ _ h => hf h
#align multiset.nodup.map Multiset.Nodup.map
theorem nodup_map_iff_of_inj_on {f : α → β} (d : ∀ x ∈ s, ∀ y ∈ s, f x = f y → x = y) :
Nodup (map f s) ↔ Nodup s :=
⟨Nodup.of_map _, fun h => h.map_on d⟩
theorem nodup_map_iff_of_injective {f : α → β} (d : Function.Injective f) :
Nodup (map f s) ↔ Nodup s :=
⟨Nodup.of_map _, fun h => h.map d⟩
theorem inj_on_of_nodup_map {f : α → β} {s : Multiset α} :
Nodup (map f s) → ∀ x ∈ s, ∀ y ∈ s, f x = f y → x = y :=
Quot.induction_on s fun _ => List.inj_on_of_nodup_map
#align multiset.inj_on_of_nodup_map Multiset.inj_on_of_nodup_map
theorem nodup_map_iff_inj_on {f : α → β} {s : Multiset α} (d : Nodup s) :
Nodup (map f s) ↔ ∀ x ∈ s, ∀ y ∈ s, f x = f y → x = y :=
⟨inj_on_of_nodup_map, fun h => d.map_on h⟩
#align multiset.nodup_map_iff_inj_on Multiset.nodup_map_iff_inj_on
theorem Nodup.filter (p : α → Prop) [DecidablePred p] {s} : Nodup s → Nodup (filter p s) :=
Quot.induction_on s fun _ => List.Nodup.filter (p ·)
#align multiset.nodup.filter Multiset.Nodup.filter
@[simp]
theorem nodup_attach {s : Multiset α} : Nodup (attach s) ↔ Nodup s :=
Quot.induction_on s fun _ => List.nodup_attach
#align multiset.nodup_attach Multiset.nodup_attach
protected alias ⟨_, Nodup.attach⟩ := nodup_attach
theorem Nodup.pmap {p : α → Prop} {f : ∀ a, p a → β} {s : Multiset α} {H}
(hf : ∀ a ha b hb, f a ha = f b hb → a = b) : Nodup s → Nodup (pmap f s H) :=
Quot.induction_on s (fun _ _ => List.Nodup.pmap hf) H
#align multiset.nodup.pmap Multiset.Nodup.pmap
instance nodupDecidable [DecidableEq α] (s : Multiset α) : Decidable (Nodup s) :=
Quotient.recOnSubsingleton s fun l => l.nodupDecidable
#align multiset.nodup_decidable Multiset.nodupDecidable
theorem Nodup.erase_eq_filter [DecidableEq α] (a : α) {s} :
Nodup s → s.erase a = Multiset.filter (· ≠ a) s :=
Quot.induction_on s fun _ d =>
congr_arg ((↑) : List α → Multiset α) <| List.Nodup.erase_eq_filter d a
#align multiset.nodup.erase_eq_filter Multiset.Nodup.erase_eq_filter
theorem Nodup.erase [DecidableEq α] (a : α) {l} : Nodup l → Nodup (l.erase a) :=
nodup_of_le (erase_le _ _)
#align multiset.nodup.erase Multiset.Nodup.erase
theorem Nodup.mem_erase_iff [DecidableEq α] {a b : α} {l} (d : Nodup l) :
a ∈ l.erase b ↔ a ≠ b ∧ a ∈ l := by
rw [d.erase_eq_filter b, mem_filter, and_comm]
#align multiset.nodup.mem_erase_iff Multiset.Nodup.mem_erase_iff
theorem Nodup.not_mem_erase [DecidableEq α] {a : α} {s} (h : Nodup s) : a ∉ s.erase a := fun ha =>
(h.mem_erase_iff.1 ha).1 rfl
#align multiset.nodup.not_mem_erase Multiset.Nodup.not_mem_erase
protected theorem Nodup.filterMap (f : α → Option β) (H : ∀ a a' b, b ∈ f a → b ∈ f a' → a = a') :
Nodup s → Nodup (filterMap f s) :=
Quot.induction_on s fun _ => List.Nodup.filterMap H
#align multiset.nodup.filter_map Multiset.Nodup.filterMap
theorem nodup_range (n : ℕ) : Nodup (range n) :=
List.nodup_range _
#align multiset.nodup_range Multiset.nodup_range
theorem Nodup.inter_left [DecidableEq α] (t) : Nodup s → Nodup (s ∩ t) :=
nodup_of_le <| inter_le_left _ _
#align multiset.nodup.inter_left Multiset.Nodup.inter_left
theorem Nodup.inter_right [DecidableEq α] (s) : Nodup t → Nodup (s ∩ t) :=
nodup_of_le <| inter_le_right _ _
#align multiset.nodup.inter_right Multiset.Nodup.inter_right
@[simp]
theorem nodup_union [DecidableEq α] {s t : Multiset α} : Nodup (s ∪ t) ↔ Nodup s ∧ Nodup t :=
⟨fun h => ⟨nodup_of_le (le_union_left _ _) h, nodup_of_le (le_union_right _ _) h⟩, fun ⟨h₁, h₂⟩ =>
nodup_iff_count_le_one.2 fun a => by
rw [count_union]
exact max_le (nodup_iff_count_le_one.1 h₁ a) (nodup_iff_count_le_one.1 h₂ a)⟩
#align multiset.nodup_union Multiset.nodup_union
theorem Nodup.ext {s t : Multiset α} : Nodup s → Nodup t → (s = t ↔ ∀ a, a ∈ s ↔ a ∈ t) :=
Quotient.inductionOn₂ s t fun _ _ d₁ d₂ => Quotient.eq.trans <| perm_ext_iff_of_nodup d₁ d₂
#align multiset.nodup.ext Multiset.Nodup.ext
theorem le_iff_subset {s t : Multiset α} : Nodup s → (s ≤ t ↔ s ⊆ t) :=
Quotient.inductionOn₂ s t fun _ _ d => ⟨subset_of_le, d.subperm⟩
#align multiset.le_iff_subset Multiset.le_iff_subset
theorem range_le {m n : ℕ} : range m ≤ range n ↔ m ≤ n :=
(le_iff_subset (nodup_range _)).trans range_subset
#align multiset.range_le Multiset.range_le
theorem mem_sub_of_nodup [DecidableEq α] {a : α} {s t : Multiset α} (d : Nodup s) :
a ∈ s - t ↔ a ∈ s ∧ a ∉ t :=
⟨fun h =>
⟨mem_of_le tsub_le_self h, fun h' => by
refine count_eq_zero.1 ?_ h
rw [count_sub a s t, Nat.sub_eq_zero_iff_le]
exact le_trans (nodup_iff_count_le_one.1 d _) (count_pos.2 h')⟩,
fun ⟨h₁, h₂⟩ => Or.resolve_right (mem_add.1 <| mem_of_le le_tsub_add h₁) h₂⟩
#align multiset.mem_sub_of_nodup Multiset.mem_sub_of_nodup
| Mathlib/Data/Multiset/Nodup.lean | 246 | 257 | theorem map_eq_map_of_bij_of_nodup (f : α → γ) (g : β → γ) {s : Multiset α} {t : Multiset β}
(hs : s.Nodup) (ht : t.Nodup) (i : ∀ a ∈ s, β) (hi : ∀ a ha, i a ha ∈ t)
(i_inj : ∀ a₁ ha₁ a₂ ha₂, i a₁ ha₁ = i a₂ ha₂ → a₁ = a₂)
(i_surj : ∀ b ∈ t, ∃ a ha, i a ha = b) (h : ∀ a ha, f a = g (i a ha)) : s.map f = t.map g := by |
have : t = s.attach.map fun x => i x.1 x.2 := by
rw [ht.ext]
· aesop
· exact hs.attach.map fun x y hxy ↦ Subtype.ext <| i_inj _ x.2 _ y.2 hxy
calc
s.map f = s.pmap (fun x _ => f x) fun _ => id := by rw [pmap_eq_map]
_ = s.attach.map fun x => f x.1 := by rw [pmap_eq_map_attach]
_ = t.map g := by rw [this, Multiset.map_map]; exact map_congr rfl fun x _ => h _ _
|
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Johan Commelin, Mario Carneiro
-/
import Mathlib.Algebra.Algebra.Tower
import Mathlib.Algebra.GroupWithZero.Divisibility
import Mathlib.Algebra.Regular.Pow
import Mathlib.Algebra.MonoidAlgebra.Support
import Mathlib.Data.Finsupp.Antidiagonal
import Mathlib.Order.SymmDiff
import Mathlib.RingTheory.Adjoin.Basic
#align_import data.mv_polynomial.basic from "leanprover-community/mathlib"@"c8734e8953e4b439147bd6f75c2163f6d27cdce6"
/-!
# Multivariate polynomials
This file defines polynomial rings over a base ring (or even semiring),
with variables from a general type `σ` (which could be infinite).
## Important definitions
Let `R` be a commutative ring (or a semiring) and let `σ` be an arbitrary
type. This file creates the type `MvPolynomial σ R`, which mathematicians
might denote $R[X_i : i \in σ]$. It is the type of multivariate
(a.k.a. multivariable) polynomials, with variables
corresponding to the terms in `σ`, and coefficients in `R`.
### Notation
In the definitions below, we use the following notation:
+ `σ : Type*` (indexing the variables)
+ `R : Type*` `[CommSemiring R]` (the coefficients)
+ `s : σ →₀ ℕ`, a function from `σ` to `ℕ` which is zero away from a finite set.
This will give rise to a monomial in `MvPolynomial σ R` which mathematicians might call `X^s`
+ `a : R`
+ `i : σ`, with corresponding monomial `X i`, often denoted `X_i` by mathematicians
+ `p : MvPolynomial σ R`
### Definitions
* `MvPolynomial σ R` : the type of polynomials with variables of type `σ` and coefficients
in the commutative semiring `R`
* `monomial s a` : the monomial which mathematically would be denoted `a * X^s`
* `C a` : the constant polynomial with value `a`
* `X i` : the degree one monomial corresponding to i; mathematically this might be denoted `Xᵢ`.
* `coeff s p` : the coefficient of `s` in `p`.
* `eval₂ (f : R → S₁) (g : σ → S₁) p` : given a semiring homomorphism from `R` to another
semiring `S₁`, and a map `σ → S₁`, evaluates `p` at this valuation, returning a term of type `S₁`.
Note that `eval₂` can be made using `eval` and `map` (see below), and it has been suggested
that sticking to `eval` and `map` might make the code less brittle.
* `eval (g : σ → R) p` : given a map `σ → R`, evaluates `p` at this valuation,
returning a term of type `R`
* `map (f : R → S₁) p` : returns the multivariate polynomial obtained from `p` by the change of
coefficient semiring corresponding to `f`
## Implementation notes
Recall that if `Y` has a zero, then `X →₀ Y` is the type of functions from `X` to `Y` with finite
support, i.e. such that only finitely many elements of `X` get sent to non-zero terms in `Y`.
The definition of `MvPolynomial σ R` is `(σ →₀ ℕ) →₀ R`; here `σ →₀ ℕ` denotes the space of all
monomials in the variables, and the function to `R` sends a monomial to its coefficient in
the polynomial being represented.
## Tags
polynomial, multivariate polynomial, multivariable polynomial
-/
noncomputable section
open Set Function Finsupp AddMonoidAlgebra
open scoped Pointwise
universe u v w x
variable {R : Type u} {S₁ : Type v} {S₂ : Type w} {S₃ : Type x}
/-- Multivariate polynomial, where `σ` is the index set of the variables and
`R` is the coefficient ring -/
def MvPolynomial (σ : Type*) (R : Type*) [CommSemiring R] :=
AddMonoidAlgebra R (σ →₀ ℕ)
#align mv_polynomial MvPolynomial
namespace MvPolynomial
-- Porting note: because of `MvPolynomial.C` and `MvPolynomial.X` this linter throws
-- tons of warnings in this file, and it's easier to just disable them globally in the file
set_option linter.uppercaseLean3 false
variable {σ : Type*} {a a' a₁ a₂ : R} {e : ℕ} {n m : σ} {s : σ →₀ ℕ}
section CommSemiring
section Instances
instance decidableEqMvPolynomial [CommSemiring R] [DecidableEq σ] [DecidableEq R] :
DecidableEq (MvPolynomial σ R) :=
Finsupp.instDecidableEq
#align mv_polynomial.decidable_eq_mv_polynomial MvPolynomial.decidableEqMvPolynomial
instance commSemiring [CommSemiring R] : CommSemiring (MvPolynomial σ R) :=
AddMonoidAlgebra.commSemiring
instance inhabited [CommSemiring R] : Inhabited (MvPolynomial σ R) :=
⟨0⟩
instance distribuMulAction [Monoid R] [CommSemiring S₁] [DistribMulAction R S₁] :
DistribMulAction R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.distribMulAction
instance smulZeroClass [CommSemiring S₁] [SMulZeroClass R S₁] :
SMulZeroClass R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.smulZeroClass
instance faithfulSMul [CommSemiring S₁] [SMulZeroClass R S₁] [FaithfulSMul R S₁] :
FaithfulSMul R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.faithfulSMul
instance module [Semiring R] [CommSemiring S₁] [Module R S₁] : Module R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.module
instance isScalarTower [CommSemiring S₂] [SMul R S₁] [SMulZeroClass R S₂] [SMulZeroClass S₁ S₂]
[IsScalarTower R S₁ S₂] : IsScalarTower R S₁ (MvPolynomial σ S₂) :=
AddMonoidAlgebra.isScalarTower
instance smulCommClass [CommSemiring S₂] [SMulZeroClass R S₂] [SMulZeroClass S₁ S₂]
[SMulCommClass R S₁ S₂] : SMulCommClass R S₁ (MvPolynomial σ S₂) :=
AddMonoidAlgebra.smulCommClass
instance isCentralScalar [CommSemiring S₁] [SMulZeroClass R S₁] [SMulZeroClass Rᵐᵒᵖ S₁]
[IsCentralScalar R S₁] : IsCentralScalar R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.isCentralScalar
instance algebra [CommSemiring R] [CommSemiring S₁] [Algebra R S₁] :
Algebra R (MvPolynomial σ S₁) :=
AddMonoidAlgebra.algebra
instance isScalarTower_right [CommSemiring S₁] [DistribSMul R S₁] [IsScalarTower R S₁ S₁] :
IsScalarTower R (MvPolynomial σ S₁) (MvPolynomial σ S₁) :=
AddMonoidAlgebra.isScalarTower_self _
#align mv_polynomial.is_scalar_tower_right MvPolynomial.isScalarTower_right
instance smulCommClass_right [CommSemiring S₁] [DistribSMul R S₁] [SMulCommClass R S₁ S₁] :
SMulCommClass R (MvPolynomial σ S₁) (MvPolynomial σ S₁) :=
AddMonoidAlgebra.smulCommClass_self _
#align mv_polynomial.smul_comm_class_right MvPolynomial.smulCommClass_right
/-- If `R` is a subsingleton, then `MvPolynomial σ R` has a unique element -/
instance unique [CommSemiring R] [Subsingleton R] : Unique (MvPolynomial σ R) :=
AddMonoidAlgebra.unique
#align mv_polynomial.unique MvPolynomial.unique
end Instances
variable [CommSemiring R] [CommSemiring S₁] {p q : MvPolynomial σ R}
/-- `monomial s a` is the monomial with coefficient `a` and exponents given by `s` -/
def monomial (s : σ →₀ ℕ) : R →ₗ[R] MvPolynomial σ R :=
lsingle s
#align mv_polynomial.monomial MvPolynomial.monomial
theorem single_eq_monomial (s : σ →₀ ℕ) (a : R) : Finsupp.single s a = monomial s a :=
rfl
#align mv_polynomial.single_eq_monomial MvPolynomial.single_eq_monomial
theorem mul_def : p * q = p.sum fun m a => q.sum fun n b => monomial (m + n) (a * b) :=
AddMonoidAlgebra.mul_def
#align mv_polynomial.mul_def MvPolynomial.mul_def
/-- `C a` is the constant polynomial with value `a` -/
def C : R →+* MvPolynomial σ R :=
{ singleZeroRingHom with toFun := monomial 0 }
#align mv_polynomial.C MvPolynomial.C
variable (R σ)
@[simp]
theorem algebraMap_eq : algebraMap R (MvPolynomial σ R) = C :=
rfl
#align mv_polynomial.algebra_map_eq MvPolynomial.algebraMap_eq
variable {R σ}
/-- `X n` is the degree `1` monomial $X_n$. -/
def X (n : σ) : MvPolynomial σ R :=
monomial (Finsupp.single n 1) 1
#align mv_polynomial.X MvPolynomial.X
theorem monomial_left_injective {r : R} (hr : r ≠ 0) :
Function.Injective fun s : σ →₀ ℕ => monomial s r :=
Finsupp.single_left_injective hr
#align mv_polynomial.monomial_left_injective MvPolynomial.monomial_left_injective
@[simp]
theorem monomial_left_inj {s t : σ →₀ ℕ} {r : R} (hr : r ≠ 0) :
monomial s r = monomial t r ↔ s = t :=
Finsupp.single_left_inj hr
#align mv_polynomial.monomial_left_inj MvPolynomial.monomial_left_inj
theorem C_apply : (C a : MvPolynomial σ R) = monomial 0 a :=
rfl
#align mv_polynomial.C_apply MvPolynomial.C_apply
-- Porting note (#10618): `simp` can prove this
theorem C_0 : C 0 = (0 : MvPolynomial σ R) := map_zero _
#align mv_polynomial.C_0 MvPolynomial.C_0
-- Porting note (#10618): `simp` can prove this
theorem C_1 : C 1 = (1 : MvPolynomial σ R) :=
rfl
#align mv_polynomial.C_1 MvPolynomial.C_1
theorem C_mul_monomial : C a * monomial s a' = monomial s (a * a') := by
-- Porting note: this `show` feels like defeq abuse, but I can't find the appropriate lemmas
show AddMonoidAlgebra.single _ _ * AddMonoidAlgebra.single _ _ = AddMonoidAlgebra.single _ _
simp [C_apply, single_mul_single]
#align mv_polynomial.C_mul_monomial MvPolynomial.C_mul_monomial
-- Porting note (#10618): `simp` can prove this
theorem C_add : (C (a + a') : MvPolynomial σ R) = C a + C a' :=
Finsupp.single_add _ _ _
#align mv_polynomial.C_add MvPolynomial.C_add
-- Porting note (#10618): `simp` can prove this
theorem C_mul : (C (a * a') : MvPolynomial σ R) = C a * C a' :=
C_mul_monomial.symm
#align mv_polynomial.C_mul MvPolynomial.C_mul
-- Porting note (#10618): `simp` can prove this
theorem C_pow (a : R) (n : ℕ) : (C (a ^ n) : MvPolynomial σ R) = C a ^ n :=
map_pow _ _ _
#align mv_polynomial.C_pow MvPolynomial.C_pow
theorem C_injective (σ : Type*) (R : Type*) [CommSemiring R] :
Function.Injective (C : R → MvPolynomial σ R) :=
Finsupp.single_injective _
#align mv_polynomial.C_injective MvPolynomial.C_injective
theorem C_surjective {R : Type*} [CommSemiring R] (σ : Type*) [IsEmpty σ] :
Function.Surjective (C : R → MvPolynomial σ R) := by
refine fun p => ⟨p.toFun 0, Finsupp.ext fun a => ?_⟩
simp only [C_apply, ← single_eq_monomial, (Finsupp.ext isEmptyElim (α := σ) : a = 0),
single_eq_same]
rfl
#align mv_polynomial.C_surjective MvPolynomial.C_surjective
@[simp]
theorem C_inj {σ : Type*} (R : Type*) [CommSemiring R] (r s : R) :
(C r : MvPolynomial σ R) = C s ↔ r = s :=
(C_injective σ R).eq_iff
#align mv_polynomial.C_inj MvPolynomial.C_inj
instance nontrivial_of_nontrivial (σ : Type*) (R : Type*) [CommSemiring R] [Nontrivial R] :
Nontrivial (MvPolynomial σ R) :=
inferInstanceAs (Nontrivial <| AddMonoidAlgebra R (σ →₀ ℕ))
instance infinite_of_infinite (σ : Type*) (R : Type*) [CommSemiring R] [Infinite R] :
Infinite (MvPolynomial σ R) :=
Infinite.of_injective C (C_injective _ _)
#align mv_polynomial.infinite_of_infinite MvPolynomial.infinite_of_infinite
instance infinite_of_nonempty (σ : Type*) (R : Type*) [Nonempty σ] [CommSemiring R]
[Nontrivial R] : Infinite (MvPolynomial σ R) :=
Infinite.of_injective ((fun s : σ →₀ ℕ => monomial s 1) ∘ Finsupp.single (Classical.arbitrary σ))
<| (monomial_left_injective one_ne_zero).comp (Finsupp.single_injective _)
#align mv_polynomial.infinite_of_nonempty MvPolynomial.infinite_of_nonempty
theorem C_eq_coe_nat (n : ℕ) : (C ↑n : MvPolynomial σ R) = n := by
induction n <;> simp [Nat.succ_eq_add_one, *]
#align mv_polynomial.C_eq_coe_nat MvPolynomial.C_eq_coe_nat
theorem C_mul' : MvPolynomial.C a * p = a • p :=
(Algebra.smul_def a p).symm
#align mv_polynomial.C_mul' MvPolynomial.C_mul'
theorem smul_eq_C_mul (p : MvPolynomial σ R) (a : R) : a • p = C a * p :=
C_mul'.symm
#align mv_polynomial.smul_eq_C_mul MvPolynomial.smul_eq_C_mul
theorem C_eq_smul_one : (C a : MvPolynomial σ R) = a • (1 : MvPolynomial σ R) := by
rw [← C_mul', mul_one]
#align mv_polynomial.C_eq_smul_one MvPolynomial.C_eq_smul_one
theorem smul_monomial {S₁ : Type*} [SMulZeroClass S₁ R] (r : S₁) :
r • monomial s a = monomial s (r • a) :=
Finsupp.smul_single _ _ _
#align mv_polynomial.smul_monomial MvPolynomial.smul_monomial
theorem X_injective [Nontrivial R] : Function.Injective (X : σ → MvPolynomial σ R) :=
(monomial_left_injective one_ne_zero).comp (Finsupp.single_left_injective one_ne_zero)
#align mv_polynomial.X_injective MvPolynomial.X_injective
@[simp]
theorem X_inj [Nontrivial R] (m n : σ) : X m = (X n : MvPolynomial σ R) ↔ m = n :=
X_injective.eq_iff
#align mv_polynomial.X_inj MvPolynomial.X_inj
theorem monomial_pow : monomial s a ^ e = monomial (e • s) (a ^ e) :=
AddMonoidAlgebra.single_pow e
#align mv_polynomial.monomial_pow MvPolynomial.monomial_pow
@[simp]
theorem monomial_mul {s s' : σ →₀ ℕ} {a b : R} :
monomial s a * monomial s' b = monomial (s + s') (a * b) :=
AddMonoidAlgebra.single_mul_single
#align mv_polynomial.monomial_mul MvPolynomial.monomial_mul
variable (σ R)
/-- `fun s ↦ monomial s 1` as a homomorphism. -/
def monomialOneHom : Multiplicative (σ →₀ ℕ) →* MvPolynomial σ R :=
AddMonoidAlgebra.of _ _
#align mv_polynomial.monomial_one_hom MvPolynomial.monomialOneHom
variable {σ R}
@[simp]
theorem monomialOneHom_apply : monomialOneHom R σ s = (monomial s 1 : MvPolynomial σ R) :=
rfl
#align mv_polynomial.monomial_one_hom_apply MvPolynomial.monomialOneHom_apply
theorem X_pow_eq_monomial : X n ^ e = monomial (Finsupp.single n e) (1 : R) := by
simp [X, monomial_pow]
#align mv_polynomial.X_pow_eq_monomial MvPolynomial.X_pow_eq_monomial
theorem monomial_add_single : monomial (s + Finsupp.single n e) a = monomial s a * X n ^ e := by
rw [X_pow_eq_monomial, monomial_mul, mul_one]
#align mv_polynomial.monomial_add_single MvPolynomial.monomial_add_single
theorem monomial_single_add : monomial (Finsupp.single n e + s) a = X n ^ e * monomial s a := by
rw [X_pow_eq_monomial, monomial_mul, one_mul]
#align mv_polynomial.monomial_single_add MvPolynomial.monomial_single_add
theorem C_mul_X_pow_eq_monomial {s : σ} {a : R} {n : ℕ} :
C a * X s ^ n = monomial (Finsupp.single s n) a := by
rw [← zero_add (Finsupp.single s n), monomial_add_single, C_apply]
#align mv_polynomial.C_mul_X_pow_eq_monomial MvPolynomial.C_mul_X_pow_eq_monomial
theorem C_mul_X_eq_monomial {s : σ} {a : R} : C a * X s = monomial (Finsupp.single s 1) a := by
rw [← C_mul_X_pow_eq_monomial, pow_one]
#align mv_polynomial.C_mul_X_eq_monomial MvPolynomial.C_mul_X_eq_monomial
-- Porting note (#10618): `simp` can prove this
theorem monomial_zero {s : σ →₀ ℕ} : monomial s (0 : R) = 0 :=
Finsupp.single_zero _
#align mv_polynomial.monomial_zero MvPolynomial.monomial_zero
@[simp]
theorem monomial_zero' : (monomial (0 : σ →₀ ℕ) : R → MvPolynomial σ R) = C :=
rfl
#align mv_polynomial.monomial_zero' MvPolynomial.monomial_zero'
@[simp]
theorem monomial_eq_zero {s : σ →₀ ℕ} {b : R} : monomial s b = 0 ↔ b = 0 :=
Finsupp.single_eq_zero
#align mv_polynomial.monomial_eq_zero MvPolynomial.monomial_eq_zero
@[simp]
theorem sum_monomial_eq {A : Type*} [AddCommMonoid A] {u : σ →₀ ℕ} {r : R} {b : (σ →₀ ℕ) → R → A}
(w : b u 0 = 0) : sum (monomial u r) b = b u r :=
Finsupp.sum_single_index w
#align mv_polynomial.sum_monomial_eq MvPolynomial.sum_monomial_eq
@[simp]
theorem sum_C {A : Type*} [AddCommMonoid A] {b : (σ →₀ ℕ) → R → A} (w : b 0 0 = 0) :
sum (C a) b = b 0 a :=
sum_monomial_eq w
#align mv_polynomial.sum_C MvPolynomial.sum_C
theorem monomial_sum_one {α : Type*} (s : Finset α) (f : α → σ →₀ ℕ) :
(monomial (∑ i ∈ s, f i) 1 : MvPolynomial σ R) = ∏ i ∈ s, monomial (f i) 1 :=
map_prod (monomialOneHom R σ) (fun i => Multiplicative.ofAdd (f i)) s
#align mv_polynomial.monomial_sum_one MvPolynomial.monomial_sum_one
theorem monomial_sum_index {α : Type*} (s : Finset α) (f : α → σ →₀ ℕ) (a : R) :
monomial (∑ i ∈ s, f i) a = C a * ∏ i ∈ s, monomial (f i) 1 := by
rw [← monomial_sum_one, C_mul', ← (monomial _).map_smul, smul_eq_mul, mul_one]
#align mv_polynomial.monomial_sum_index MvPolynomial.monomial_sum_index
theorem monomial_finsupp_sum_index {α β : Type*} [Zero β] (f : α →₀ β) (g : α → β → σ →₀ ℕ)
(a : R) : monomial (f.sum g) a = C a * f.prod fun a b => monomial (g a b) 1 :=
monomial_sum_index _ _ _
#align mv_polynomial.monomial_finsupp_sum_index MvPolynomial.monomial_finsupp_sum_index
theorem monomial_eq_monomial_iff {α : Type*} (a₁ a₂ : α →₀ ℕ) (b₁ b₂ : R) :
monomial a₁ b₁ = monomial a₂ b₂ ↔ a₁ = a₂ ∧ b₁ = b₂ ∨ b₁ = 0 ∧ b₂ = 0 :=
Finsupp.single_eq_single_iff _ _ _ _
#align mv_polynomial.monomial_eq_monomial_iff MvPolynomial.monomial_eq_monomial_iff
theorem monomial_eq : monomial s a = C a * (s.prod fun n e => X n ^ e : MvPolynomial σ R) := by
simp only [X_pow_eq_monomial, ← monomial_finsupp_sum_index, Finsupp.sum_single]
#align mv_polynomial.monomial_eq MvPolynomial.monomial_eq
@[simp]
lemma prod_X_pow_eq_monomial : ∏ x ∈ s.support, X x ^ s x = monomial s (1 : R) := by
simp only [monomial_eq, map_one, one_mul, Finsupp.prod]
theorem induction_on_monomial {M : MvPolynomial σ R → Prop} (h_C : ∀ a, M (C a))
(h_X : ∀ p n, M p → M (p * X n)) : ∀ s a, M (monomial s a) := by
intro s a
apply @Finsupp.induction σ ℕ _ _ s
· show M (monomial 0 a)
exact h_C a
· intro n e p _hpn _he ih
have : ∀ e : ℕ, M (monomial p a * X n ^ e) := by
intro e
induction e with
| zero => simp [ih]
| succ e e_ih => simp [ih, pow_succ, (mul_assoc _ _ _).symm, h_X, e_ih]
simp [add_comm, monomial_add_single, this]
#align mv_polynomial.induction_on_monomial MvPolynomial.induction_on_monomial
/-- Analog of `Polynomial.induction_on'`.
To prove something about mv_polynomials,
it suffices to show the condition is closed under taking sums,
and it holds for monomials. -/
@[elab_as_elim]
theorem induction_on' {P : MvPolynomial σ R → Prop} (p : MvPolynomial σ R)
(h1 : ∀ (u : σ →₀ ℕ) (a : R), P (monomial u a))
(h2 : ∀ p q : MvPolynomial σ R, P p → P q → P (p + q)) : P p :=
Finsupp.induction p
(suffices P (monomial 0 0) by rwa [monomial_zero] at this
show P (monomial 0 0) from h1 0 0)
fun a b f _ha _hb hPf => h2 _ _ (h1 _ _) hPf
#align mv_polynomial.induction_on' MvPolynomial.induction_on'
/-- Similar to `MvPolynomial.induction_on` but only a weak form of `h_add` is required. -/
theorem induction_on''' {M : MvPolynomial σ R → Prop} (p : MvPolynomial σ R) (h_C : ∀ a, M (C a))
(h_add_weak :
∀ (a : σ →₀ ℕ) (b : R) (f : (σ →₀ ℕ) →₀ R),
a ∉ f.support → b ≠ 0 → M f → M ((show (σ →₀ ℕ) →₀ R from monomial a b) + f)) :
M p :=
-- Porting note: I had to add the `show ... from ...` above, a type ascription was insufficient.
Finsupp.induction p (C_0.rec <| h_C 0) h_add_weak
#align mv_polynomial.induction_on''' MvPolynomial.induction_on'''
/-- Similar to `MvPolynomial.induction_on` but only a yet weaker form of `h_add` is required. -/
theorem induction_on'' {M : MvPolynomial σ R → Prop} (p : MvPolynomial σ R) (h_C : ∀ a, M (C a))
(h_add_weak :
∀ (a : σ →₀ ℕ) (b : R) (f : (σ →₀ ℕ) →₀ R),
a ∉ f.support → b ≠ 0 → M f → M (monomial a b) →
M ((show (σ →₀ ℕ) →₀ R from monomial a b) + f))
(h_X : ∀ (p : MvPolynomial σ R) (n : σ), M p → M (p * MvPolynomial.X n)) : M p :=
-- Porting note: I had to add the `show ... from ...` above, a type ascription was insufficient.
induction_on''' p h_C fun a b f ha hb hf =>
h_add_weak a b f ha hb hf <| induction_on_monomial h_C h_X a b
#align mv_polynomial.induction_on'' MvPolynomial.induction_on''
/-- Analog of `Polynomial.induction_on`. -/
@[recursor 5]
theorem induction_on {M : MvPolynomial σ R → Prop} (p : MvPolynomial σ R) (h_C : ∀ a, M (C a))
(h_add : ∀ p q, M p → M q → M (p + q)) (h_X : ∀ p n, M p → M (p * X n)) : M p :=
induction_on'' p h_C (fun a b f _ha _hb hf hm => h_add (monomial a b) f hm hf) h_X
#align mv_polynomial.induction_on MvPolynomial.induction_on
theorem ringHom_ext {A : Type*} [Semiring A] {f g : MvPolynomial σ R →+* A}
(hC : ∀ r, f (C r) = g (C r)) (hX : ∀ i, f (X i) = g (X i)) : f = g := by
refine AddMonoidAlgebra.ringHom_ext' ?_ ?_
-- Porting note: this has high priority, but Lean still chooses `RingHom.ext`, why?
-- probably because of the type synonym
· ext x
exact hC _
· apply Finsupp.mulHom_ext'; intros x
-- Porting note: `Finsupp.mulHom_ext'` needs to have increased priority
apply MonoidHom.ext_mnat
exact hX _
#align mv_polynomial.ring_hom_ext MvPolynomial.ringHom_ext
/-- See note [partially-applied ext lemmas]. -/
@[ext 1100]
theorem ringHom_ext' {A : Type*} [Semiring A] {f g : MvPolynomial σ R →+* A}
(hC : f.comp C = g.comp C) (hX : ∀ i, f (X i) = g (X i)) : f = g :=
ringHom_ext (RingHom.ext_iff.1 hC) hX
#align mv_polynomial.ring_hom_ext' MvPolynomial.ringHom_ext'
theorem hom_eq_hom [Semiring S₂] (f g : MvPolynomial σ R →+* S₂) (hC : f.comp C = g.comp C)
(hX : ∀ n : σ, f (X n) = g (X n)) (p : MvPolynomial σ R) : f p = g p :=
RingHom.congr_fun (ringHom_ext' hC hX) p
#align mv_polynomial.hom_eq_hom MvPolynomial.hom_eq_hom
theorem is_id (f : MvPolynomial σ R →+* MvPolynomial σ R) (hC : f.comp C = C)
(hX : ∀ n : σ, f (X n) = X n) (p : MvPolynomial σ R) : f p = p :=
hom_eq_hom f (RingHom.id _) hC hX p
#align mv_polynomial.is_id MvPolynomial.is_id
@[ext 1100]
theorem algHom_ext' {A B : Type*} [CommSemiring A] [CommSemiring B] [Algebra R A] [Algebra R B]
{f g : MvPolynomial σ A →ₐ[R] B}
(h₁ :
f.comp (IsScalarTower.toAlgHom R A (MvPolynomial σ A)) =
g.comp (IsScalarTower.toAlgHom R A (MvPolynomial σ A)))
(h₂ : ∀ i, f (X i) = g (X i)) : f = g :=
AlgHom.coe_ringHom_injective (MvPolynomial.ringHom_ext' (congr_arg AlgHom.toRingHom h₁) h₂)
#align mv_polynomial.alg_hom_ext' MvPolynomial.algHom_ext'
@[ext 1200]
theorem algHom_ext {A : Type*} [Semiring A] [Algebra R A] {f g : MvPolynomial σ R →ₐ[R] A}
(hf : ∀ i : σ, f (X i) = g (X i)) : f = g :=
AddMonoidAlgebra.algHom_ext' (mulHom_ext' fun X : σ => MonoidHom.ext_mnat (hf X))
#align mv_polynomial.alg_hom_ext MvPolynomial.algHom_ext
@[simp]
theorem algHom_C {τ : Type*} (f : MvPolynomial σ R →ₐ[R] MvPolynomial τ R) (r : R) :
f (C r) = C r :=
f.commutes r
#align mv_polynomial.alg_hom_C MvPolynomial.algHom_C
@[simp]
theorem adjoin_range_X : Algebra.adjoin R (range (X : σ → MvPolynomial σ R)) = ⊤ := by
set S := Algebra.adjoin R (range (X : σ → MvPolynomial σ R))
refine top_unique fun p hp => ?_; clear hp
induction p using MvPolynomial.induction_on with
| h_C => exact S.algebraMap_mem _
| h_add p q hp hq => exact S.add_mem hp hq
| h_X p i hp => exact S.mul_mem hp (Algebra.subset_adjoin <| mem_range_self _)
#align mv_polynomial.adjoin_range_X MvPolynomial.adjoin_range_X
@[ext]
theorem linearMap_ext {M : Type*} [AddCommMonoid M] [Module R M] {f g : MvPolynomial σ R →ₗ[R] M}
(h : ∀ s, f ∘ₗ monomial s = g ∘ₗ monomial s) : f = g :=
Finsupp.lhom_ext' h
#align mv_polynomial.linear_map_ext MvPolynomial.linearMap_ext
section Support
/-- The finite set of all `m : σ →₀ ℕ` such that `X^m` has a non-zero coefficient. -/
def support (p : MvPolynomial σ R) : Finset (σ →₀ ℕ) :=
Finsupp.support p
#align mv_polynomial.support MvPolynomial.support
theorem finsupp_support_eq_support (p : MvPolynomial σ R) : Finsupp.support p = p.support :=
rfl
#align mv_polynomial.finsupp_support_eq_support MvPolynomial.finsupp_support_eq_support
theorem support_monomial [h : Decidable (a = 0)] :
(monomial s a).support = if a = 0 then ∅ else {s} := by
rw [← Subsingleton.elim (Classical.decEq R a 0) h]
rfl
-- Porting note: the proof in Lean 3 wasn't fundamentally better and needed `by convert rfl`
-- the issue is the different decidability instances in the `ite` expressions
#align mv_polynomial.support_monomial MvPolynomial.support_monomial
theorem support_monomial_subset : (monomial s a).support ⊆ {s} :=
support_single_subset
#align mv_polynomial.support_monomial_subset MvPolynomial.support_monomial_subset
theorem support_add [DecidableEq σ] : (p + q).support ⊆ p.support ∪ q.support :=
Finsupp.support_add
#align mv_polynomial.support_add MvPolynomial.support_add
theorem support_X [Nontrivial R] : (X n : MvPolynomial σ R).support = {Finsupp.single n 1} := by
classical rw [X, support_monomial, if_neg]; exact one_ne_zero
#align mv_polynomial.support_X MvPolynomial.support_X
theorem support_X_pow [Nontrivial R] (s : σ) (n : ℕ) :
(X s ^ n : MvPolynomial σ R).support = {Finsupp.single s n} := by
classical
rw [X_pow_eq_monomial, support_monomial, if_neg (one_ne_zero' R)]
#align mv_polynomial.support_X_pow MvPolynomial.support_X_pow
@[simp]
theorem support_zero : (0 : MvPolynomial σ R).support = ∅ :=
rfl
#align mv_polynomial.support_zero MvPolynomial.support_zero
theorem support_smul {S₁ : Type*} [SMulZeroClass S₁ R] {a : S₁} {f : MvPolynomial σ R} :
(a • f).support ⊆ f.support :=
Finsupp.support_smul
#align mv_polynomial.support_smul MvPolynomial.support_smul
theorem support_sum {α : Type*} [DecidableEq σ] {s : Finset α} {f : α → MvPolynomial σ R} :
(∑ x ∈ s, f x).support ⊆ s.biUnion fun x => (f x).support :=
Finsupp.support_finset_sum
#align mv_polynomial.support_sum MvPolynomial.support_sum
end Support
section Coeff
/-- The coefficient of the monomial `m` in the multi-variable polynomial `p`. -/
def coeff (m : σ →₀ ℕ) (p : MvPolynomial σ R) : R :=
@DFunLike.coe ((σ →₀ ℕ) →₀ R) _ _ _ p m
-- Porting note: I changed this from `@CoeFun.coe _ _ (MonoidAlgebra.coeFun _ _) p m` because
-- I think it should work better syntactically. They are defeq.
#align mv_polynomial.coeff MvPolynomial.coeff
@[simp]
theorem mem_support_iff {p : MvPolynomial σ R} {m : σ →₀ ℕ} : m ∈ p.support ↔ p.coeff m ≠ 0 := by
simp [support, coeff]
#align mv_polynomial.mem_support_iff MvPolynomial.mem_support_iff
theorem not_mem_support_iff {p : MvPolynomial σ R} {m : σ →₀ ℕ} : m ∉ p.support ↔ p.coeff m = 0 :=
by simp
#align mv_polynomial.not_mem_support_iff MvPolynomial.not_mem_support_iff
theorem sum_def {A} [AddCommMonoid A] {p : MvPolynomial σ R} {b : (σ →₀ ℕ) → R → A} :
p.sum b = ∑ m ∈ p.support, b m (p.coeff m) := by simp [support, Finsupp.sum, coeff]
#align mv_polynomial.sum_def MvPolynomial.sum_def
theorem support_mul [DecidableEq σ] (p q : MvPolynomial σ R) :
(p * q).support ⊆ p.support + q.support :=
AddMonoidAlgebra.support_mul p q
#align mv_polynomial.support_mul MvPolynomial.support_mul
@[ext]
theorem ext (p q : MvPolynomial σ R) : (∀ m, coeff m p = coeff m q) → p = q :=
Finsupp.ext
#align mv_polynomial.ext MvPolynomial.ext
theorem ext_iff (p q : MvPolynomial σ R) : p = q ↔ ∀ m, coeff m p = coeff m q :=
⟨fun h m => by rw [h], ext p q⟩
#align mv_polynomial.ext_iff MvPolynomial.ext_iff
@[simp]
theorem coeff_add (m : σ →₀ ℕ) (p q : MvPolynomial σ R) : coeff m (p + q) = coeff m p + coeff m q :=
add_apply p q m
#align mv_polynomial.coeff_add MvPolynomial.coeff_add
@[simp]
theorem coeff_smul {S₁ : Type*} [SMulZeroClass S₁ R] (m : σ →₀ ℕ) (C : S₁) (p : MvPolynomial σ R) :
coeff m (C • p) = C • coeff m p :=
smul_apply C p m
#align mv_polynomial.coeff_smul MvPolynomial.coeff_smul
@[simp]
theorem coeff_zero (m : σ →₀ ℕ) : coeff m (0 : MvPolynomial σ R) = 0 :=
rfl
#align mv_polynomial.coeff_zero MvPolynomial.coeff_zero
@[simp]
theorem coeff_zero_X (i : σ) : coeff 0 (X i : MvPolynomial σ R) = 0 :=
single_eq_of_ne fun h => by cases Finsupp.single_eq_zero.1 h
#align mv_polynomial.coeff_zero_X MvPolynomial.coeff_zero_X
/-- `MvPolynomial.coeff m` but promoted to an `AddMonoidHom`. -/
@[simps]
def coeffAddMonoidHom (m : σ →₀ ℕ) : MvPolynomial σ R →+ R where
toFun := coeff m
map_zero' := coeff_zero m
map_add' := coeff_add m
#align mv_polynomial.coeff_add_monoid_hom MvPolynomial.coeffAddMonoidHom
variable (R) in
/-- `MvPolynomial.coeff m` but promoted to a `LinearMap`. -/
@[simps]
def lcoeff (m : σ →₀ ℕ) : MvPolynomial σ R →ₗ[R] R where
toFun := coeff m
map_add' := coeff_add m
map_smul' := coeff_smul m
theorem coeff_sum {X : Type*} (s : Finset X) (f : X → MvPolynomial σ R) (m : σ →₀ ℕ) :
coeff m (∑ x ∈ s, f x) = ∑ x ∈ s, coeff m (f x) :=
map_sum (@coeffAddMonoidHom R σ _ _) _ s
#align mv_polynomial.coeff_sum MvPolynomial.coeff_sum
theorem monic_monomial_eq (m) :
monomial m (1 : R) = (m.prod fun n e => X n ^ e : MvPolynomial σ R) := by simp [monomial_eq]
#align mv_polynomial.monic_monomial_eq MvPolynomial.monic_monomial_eq
@[simp]
theorem coeff_monomial [DecidableEq σ] (m n) (a) :
coeff m (monomial n a : MvPolynomial σ R) = if n = m then a else 0 :=
Finsupp.single_apply
#align mv_polynomial.coeff_monomial MvPolynomial.coeff_monomial
@[simp]
theorem coeff_C [DecidableEq σ] (m) (a) :
coeff m (C a : MvPolynomial σ R) = if 0 = m then a else 0 :=
Finsupp.single_apply
#align mv_polynomial.coeff_C MvPolynomial.coeff_C
lemma eq_C_of_isEmpty [IsEmpty σ] (p : MvPolynomial σ R) :
p = C (p.coeff 0) := by
obtain ⟨x, rfl⟩ := C_surjective σ p
simp
theorem coeff_one [DecidableEq σ] (m) : coeff m (1 : MvPolynomial σ R) = if 0 = m then 1 else 0 :=
coeff_C m 1
#align mv_polynomial.coeff_one MvPolynomial.coeff_one
@[simp]
theorem coeff_zero_C (a) : coeff 0 (C a : MvPolynomial σ R) = a :=
single_eq_same
#align mv_polynomial.coeff_zero_C MvPolynomial.coeff_zero_C
@[simp]
theorem coeff_zero_one : coeff 0 (1 : MvPolynomial σ R) = 1 :=
coeff_zero_C 1
#align mv_polynomial.coeff_zero_one MvPolynomial.coeff_zero_one
theorem coeff_X_pow [DecidableEq σ] (i : σ) (m) (k : ℕ) :
coeff m (X i ^ k : MvPolynomial σ R) = if Finsupp.single i k = m then 1 else 0 := by
have := coeff_monomial m (Finsupp.single i k) (1 : R)
rwa [@monomial_eq _ _ (1 : R) (Finsupp.single i k) _, C_1, one_mul, Finsupp.prod_single_index]
at this
exact pow_zero _
#align mv_polynomial.coeff_X_pow MvPolynomial.coeff_X_pow
theorem coeff_X' [DecidableEq σ] (i : σ) (m) :
coeff m (X i : MvPolynomial σ R) = if Finsupp.single i 1 = m then 1 else 0 := by
rw [← coeff_X_pow, pow_one]
#align mv_polynomial.coeff_X' MvPolynomial.coeff_X'
@[simp]
theorem coeff_X (i : σ) : coeff (Finsupp.single i 1) (X i : MvPolynomial σ R) = 1 := by
classical rw [coeff_X', if_pos rfl]
#align mv_polynomial.coeff_X MvPolynomial.coeff_X
@[simp]
theorem coeff_C_mul (m) (a : R) (p : MvPolynomial σ R) : coeff m (C a * p) = a * coeff m p := by
classical
rw [mul_def, sum_C]
· simp (config := { contextual := true }) [sum_def, coeff_sum]
simp
#align mv_polynomial.coeff_C_mul MvPolynomial.coeff_C_mul
theorem coeff_mul [DecidableEq σ] (p q : MvPolynomial σ R) (n : σ →₀ ℕ) :
coeff n (p * q) = ∑ x ∈ Finset.antidiagonal n, coeff x.1 p * coeff x.2 q :=
AddMonoidAlgebra.mul_apply_antidiagonal p q _ _ Finset.mem_antidiagonal
#align mv_polynomial.coeff_mul MvPolynomial.coeff_mul
@[simp]
theorem coeff_mul_monomial (m) (s : σ →₀ ℕ) (r : R) (p : MvPolynomial σ R) :
coeff (m + s) (p * monomial s r) = coeff m p * r :=
AddMonoidAlgebra.mul_single_apply_aux p _ _ _ _ fun _a => add_left_inj _
#align mv_polynomial.coeff_mul_monomial MvPolynomial.coeff_mul_monomial
@[simp]
theorem coeff_monomial_mul (m) (s : σ →₀ ℕ) (r : R) (p : MvPolynomial σ R) :
coeff (s + m) (monomial s r * p) = r * coeff m p :=
AddMonoidAlgebra.single_mul_apply_aux p _ _ _ _ fun _a => add_right_inj _
#align mv_polynomial.coeff_monomial_mul MvPolynomial.coeff_monomial_mul
@[simp]
theorem coeff_mul_X (m) (s : σ) (p : MvPolynomial σ R) :
coeff (m + Finsupp.single s 1) (p * X s) = coeff m p :=
(coeff_mul_monomial _ _ _ _).trans (mul_one _)
#align mv_polynomial.coeff_mul_X MvPolynomial.coeff_mul_X
@[simp]
theorem coeff_X_mul (m) (s : σ) (p : MvPolynomial σ R) :
coeff (Finsupp.single s 1 + m) (X s * p) = coeff m p :=
(coeff_monomial_mul _ _ _ _).trans (one_mul _)
#align mv_polynomial.coeff_X_mul MvPolynomial.coeff_X_mul
lemma coeff_single_X_pow [DecidableEq σ] (s s' : σ) (n n' : ℕ) :
(X (R := R) s ^ n).coeff (Finsupp.single s' n')
= if s = s' ∧ n = n' ∨ n = 0 ∧ n' = 0 then 1 else 0 := by
simp only [coeff_X_pow, single_eq_single_iff]
@[simp]
lemma coeff_single_X [DecidableEq σ] (s s' : σ) (n : ℕ) :
(X s).coeff (R := R) (Finsupp.single s' n) = if n = 1 ∧ s = s' then 1 else 0 := by
simpa [eq_comm, and_comm] using coeff_single_X_pow s s' 1 n
@[simp]
theorem support_mul_X (s : σ) (p : MvPolynomial σ R) :
(p * X s).support = p.support.map (addRightEmbedding (Finsupp.single s 1)) :=
AddMonoidAlgebra.support_mul_single p _ (by simp) _
#align mv_polynomial.support_mul_X MvPolynomial.support_mul_X
@[simp]
theorem support_X_mul (s : σ) (p : MvPolynomial σ R) :
(X s * p).support = p.support.map (addLeftEmbedding (Finsupp.single s 1)) :=
AddMonoidAlgebra.support_single_mul p _ (by simp) _
#align mv_polynomial.support_X_mul MvPolynomial.support_X_mul
@[simp]
theorem support_smul_eq {S₁ : Type*} [Semiring S₁] [Module S₁ R] [NoZeroSMulDivisors S₁ R] {a : S₁}
(h : a ≠ 0) (p : MvPolynomial σ R) : (a • p).support = p.support :=
Finsupp.support_smul_eq h
#align mv_polynomial.support_smul_eq MvPolynomial.support_smul_eq
theorem support_sdiff_support_subset_support_add [DecidableEq σ] (p q : MvPolynomial σ R) :
p.support \ q.support ⊆ (p + q).support := by
intro m hm
simp only [Classical.not_not, mem_support_iff, Finset.mem_sdiff, Ne] at hm
simp [hm.2, hm.1]
#align mv_polynomial.support_sdiff_support_subset_support_add MvPolynomial.support_sdiff_support_subset_support_add
open scoped symmDiff in
theorem support_symmDiff_support_subset_support_add [DecidableEq σ] (p q : MvPolynomial σ R) :
p.support ∆ q.support ⊆ (p + q).support := by
rw [symmDiff_def, Finset.sup_eq_union]
apply Finset.union_subset
· exact support_sdiff_support_subset_support_add p q
· rw [add_comm]
exact support_sdiff_support_subset_support_add q p
#align mv_polynomial.support_symm_diff_support_subset_support_add MvPolynomial.support_symmDiff_support_subset_support_add
theorem coeff_mul_monomial' (m) (s : σ →₀ ℕ) (r : R) (p : MvPolynomial σ R) :
coeff m (p * monomial s r) = if s ≤ m then coeff (m - s) p * r else 0 := by
classical
split_ifs with h
· conv_rhs => rw [← coeff_mul_monomial _ s]
congr with t
rw [tsub_add_cancel_of_le h]
· contrapose! h
rw [← mem_support_iff] at h
obtain ⟨j, -, rfl⟩ : ∃ j ∈ support p, j + s = m := by
simpa [Finset.add_singleton]
using Finset.add_subset_add_left support_monomial_subset <| support_mul _ _ h
exact le_add_left le_rfl
#align mv_polynomial.coeff_mul_monomial' MvPolynomial.coeff_mul_monomial'
theorem coeff_monomial_mul' (m) (s : σ →₀ ℕ) (r : R) (p : MvPolynomial σ R) :
coeff m (monomial s r * p) = if s ≤ m then r * coeff (m - s) p else 0 := by
-- note that if we allow `R` to be non-commutative we will have to duplicate the proof above.
rw [mul_comm, mul_comm r]
exact coeff_mul_monomial' _ _ _ _
#align mv_polynomial.coeff_monomial_mul' MvPolynomial.coeff_monomial_mul'
theorem coeff_mul_X' [DecidableEq σ] (m) (s : σ) (p : MvPolynomial σ R) :
coeff m (p * X s) = if s ∈ m.support then coeff (m - Finsupp.single s 1) p else 0 := by
refine (coeff_mul_monomial' _ _ _ _).trans ?_
simp_rw [Finsupp.single_le_iff, Finsupp.mem_support_iff, Nat.succ_le_iff, pos_iff_ne_zero,
mul_one]
#align mv_polynomial.coeff_mul_X' MvPolynomial.coeff_mul_X'
theorem coeff_X_mul' [DecidableEq σ] (m) (s : σ) (p : MvPolynomial σ R) :
coeff m (X s * p) = if s ∈ m.support then coeff (m - Finsupp.single s 1) p else 0 := by
refine (coeff_monomial_mul' _ _ _ _).trans ?_
simp_rw [Finsupp.single_le_iff, Finsupp.mem_support_iff, Nat.succ_le_iff, pos_iff_ne_zero,
one_mul]
#align mv_polynomial.coeff_X_mul' MvPolynomial.coeff_X_mul'
theorem eq_zero_iff {p : MvPolynomial σ R} : p = 0 ↔ ∀ d, coeff d p = 0 := by
rw [ext_iff]
simp only [coeff_zero]
#align mv_polynomial.eq_zero_iff MvPolynomial.eq_zero_iff
theorem ne_zero_iff {p : MvPolynomial σ R} : p ≠ 0 ↔ ∃ d, coeff d p ≠ 0 := by
rw [Ne, eq_zero_iff]
push_neg
rfl
#align mv_polynomial.ne_zero_iff MvPolynomial.ne_zero_iff
@[simp]
theorem X_ne_zero [Nontrivial R] (s : σ) :
X (R := R) s ≠ 0 := by
rw [ne_zero_iff]
use Finsupp.single s 1
simp only [coeff_X, ne_eq, one_ne_zero, not_false_eq_true]
@[simp]
theorem support_eq_empty {p : MvPolynomial σ R} : p.support = ∅ ↔ p = 0 :=
Finsupp.support_eq_empty
#align mv_polynomial.support_eq_empty MvPolynomial.support_eq_empty
@[simp]
lemma support_nonempty {p : MvPolynomial σ R} : p.support.Nonempty ↔ p ≠ 0 := by
rw [Finset.nonempty_iff_ne_empty, ne_eq, support_eq_empty]
theorem exists_coeff_ne_zero {p : MvPolynomial σ R} (h : p ≠ 0) : ∃ d, coeff d p ≠ 0 :=
ne_zero_iff.mp h
#align mv_polynomial.exists_coeff_ne_zero MvPolynomial.exists_coeff_ne_zero
theorem C_dvd_iff_dvd_coeff (r : R) (φ : MvPolynomial σ R) : C r ∣ φ ↔ ∀ i, r ∣ φ.coeff i := by
constructor
· rintro ⟨φ, rfl⟩ c
rw [coeff_C_mul]
apply dvd_mul_right
· intro h
choose C hc using h
classical
let c' : (σ →₀ ℕ) → R := fun i => if i ∈ φ.support then C i else 0
let ψ : MvPolynomial σ R := ∑ i ∈ φ.support, monomial i (c' i)
use ψ
apply MvPolynomial.ext
intro i
simp only [ψ, c', coeff_C_mul, coeff_sum, coeff_monomial, Finset.sum_ite_eq']
split_ifs with hi
· rw [hc]
· rw [not_mem_support_iff] at hi
rwa [mul_zero]
#align mv_polynomial.C_dvd_iff_dvd_coeff MvPolynomial.C_dvd_iff_dvd_coeff
@[simp] lemma isRegular_X : IsRegular (X n : MvPolynomial σ R) := by
suffices IsLeftRegular (X n : MvPolynomial σ R) from
⟨this, this.right_of_commute <| Commute.all _⟩
intro P Q (hPQ : (X n) * P = (X n) * Q)
ext i
rw [← coeff_X_mul i n P, hPQ, coeff_X_mul i n Q]
@[simp] lemma isRegular_X_pow (k : ℕ) : IsRegular (X n ^ k : MvPolynomial σ R) := isRegular_X.pow k
@[simp] lemma isRegular_prod_X (s : Finset σ) :
IsRegular (∏ n ∈ s, X n : MvPolynomial σ R) :=
IsRegular.prod fun _ _ ↦ isRegular_X
/-- The finset of nonzero coefficients of a multivariate polynomial. -/
def coeffs (p : MvPolynomial σ R) : Finset R :=
letI := Classical.decEq R
Finset.image p.coeff p.support
@[simp]
lemma coeffs_zero : coeffs (0 : MvPolynomial σ R) = ∅ :=
rfl
lemma coeffs_one : coeffs (1 : MvPolynomial σ R) ⊆ {1} := by
classical
rw [coeffs, Finset.image_subset_iff]
simp_all [coeff_one]
@[nontriviality]
lemma coeffs_eq_empty_of_subsingleton [Subsingleton R] (p : MvPolynomial σ R) : p.coeffs = ∅ := by
simpa [coeffs] using Subsingleton.eq_zero p
@[simp]
lemma coeffs_one_of_nontrivial [Nontrivial R] : coeffs (1 : MvPolynomial σ R) = {1} := by
apply Finset.Subset.antisymm coeffs_one
simp only [coeffs, Finset.singleton_subset_iff, Finset.mem_image]
exact ⟨0, by simp⟩
lemma mem_coeffs_iff {p : MvPolynomial σ R} {c : R} :
c ∈ p.coeffs ↔ ∃ n ∈ p.support, c = p.coeff n := by
simp [coeffs, eq_comm, (Finset.mem_image)]
lemma coeff_mem_coeffs {p : MvPolynomial σ R} (m : σ →₀ ℕ)
(h : p.coeff m ≠ 0) : p.coeff m ∈ p.coeffs :=
letI := Classical.decEq R
Finset.mem_image_of_mem p.coeff (mem_support_iff.mpr h)
lemma zero_not_mem_coeffs (p : MvPolynomial σ R) : 0 ∉ p.coeffs := by
intro hz
obtain ⟨n, hnsupp, hn⟩ := mem_coeffs_iff.mp hz
exact (mem_support_iff.mp hnsupp) hn.symm
end Coeff
section ConstantCoeff
/-- `constantCoeff p` returns the constant term of the polynomial `p`, defined as `coeff 0 p`.
This is a ring homomorphism.
-/
def constantCoeff : MvPolynomial σ R →+* R where
toFun := coeff 0
map_one' := by simp [AddMonoidAlgebra.one_def]
map_mul' := by classical simp [coeff_mul, Finsupp.support_single_ne_zero]
map_zero' := coeff_zero _
map_add' := coeff_add _
#align mv_polynomial.constant_coeff MvPolynomial.constantCoeff
theorem constantCoeff_eq : (constantCoeff : MvPolynomial σ R → R) = coeff 0 :=
rfl
#align mv_polynomial.constant_coeff_eq MvPolynomial.constantCoeff_eq
variable (σ)
@[simp]
theorem constantCoeff_C (r : R) : constantCoeff (C r : MvPolynomial σ R) = r := by
classical simp [constantCoeff_eq]
#align mv_polynomial.constant_coeff_C MvPolynomial.constantCoeff_C
variable {σ}
variable (R)
@[simp]
theorem constantCoeff_X (i : σ) : constantCoeff (X i : MvPolynomial σ R) = 0 := by
simp [constantCoeff_eq]
#align mv_polynomial.constant_coeff_X MvPolynomial.constantCoeff_X
variable {R}
/- porting note: increased priority because otherwise `simp` time outs when trying to simplify
the left-hand side. `simpNF` linter indicated this and it was verified. -/
@[simp 1001]
theorem constantCoeff_smul {R : Type*} [SMulZeroClass R S₁] (a : R) (f : MvPolynomial σ S₁) :
constantCoeff (a • f) = a • constantCoeff f :=
rfl
#align mv_polynomial.constant_coeff_smul MvPolynomial.constantCoeff_smul
theorem constantCoeff_monomial [DecidableEq σ] (d : σ →₀ ℕ) (r : R) :
constantCoeff (monomial d r) = if d = 0 then r else 0 := by
rw [constantCoeff_eq, coeff_monomial]
#align mv_polynomial.constant_coeff_monomial MvPolynomial.constantCoeff_monomial
variable (σ R)
@[simp]
theorem constantCoeff_comp_C : constantCoeff.comp (C : R →+* MvPolynomial σ R) = RingHom.id R := by
ext x
exact constantCoeff_C σ x
#align mv_polynomial.constant_coeff_comp_C MvPolynomial.constantCoeff_comp_C
theorem constantCoeff_comp_algebraMap :
constantCoeff.comp (algebraMap R (MvPolynomial σ R)) = RingHom.id R :=
constantCoeff_comp_C _ _
#align mv_polynomial.constant_coeff_comp_algebra_map MvPolynomial.constantCoeff_comp_algebraMap
end ConstantCoeff
section AsSum
@[simp]
theorem support_sum_monomial_coeff (p : MvPolynomial σ R) :
(∑ v ∈ p.support, monomial v (coeff v p)) = p :=
Finsupp.sum_single p
#align mv_polynomial.support_sum_monomial_coeff MvPolynomial.support_sum_monomial_coeff
theorem as_sum (p : MvPolynomial σ R) : p = ∑ v ∈ p.support, monomial v (coeff v p) :=
(support_sum_monomial_coeff p).symm
#align mv_polynomial.as_sum MvPolynomial.as_sum
end AsSum
section Eval₂
variable (f : R →+* S₁) (g : σ → S₁)
/-- Evaluate a polynomial `p` given a valuation `g` of all the variables
and a ring hom `f` from the scalar ring to the target -/
def eval₂ (p : MvPolynomial σ R) : S₁ :=
p.sum fun s a => f a * s.prod fun n e => g n ^ e
#align mv_polynomial.eval₂ MvPolynomial.eval₂
theorem eval₂_eq (g : R →+* S₁) (X : σ → S₁) (f : MvPolynomial σ R) :
f.eval₂ g X = ∑ d ∈ f.support, g (f.coeff d) * ∏ i ∈ d.support, X i ^ d i :=
rfl
#align mv_polynomial.eval₂_eq MvPolynomial.eval₂_eq
theorem eval₂_eq' [Fintype σ] (g : R →+* S₁) (X : σ → S₁) (f : MvPolynomial σ R) :
f.eval₂ g X = ∑ d ∈ f.support, g (f.coeff d) * ∏ i, X i ^ d i := by
simp only [eval₂_eq, ← Finsupp.prod_pow]
rfl
#align mv_polynomial.eval₂_eq' MvPolynomial.eval₂_eq'
@[simp]
theorem eval₂_zero : (0 : MvPolynomial σ R).eval₂ f g = 0 :=
Finsupp.sum_zero_index
#align mv_polynomial.eval₂_zero MvPolynomial.eval₂_zero
section
@[simp]
theorem eval₂_add : (p + q).eval₂ f g = p.eval₂ f g + q.eval₂ f g := by
classical exact Finsupp.sum_add_index (by simp [f.map_zero]) (by simp [add_mul, f.map_add])
#align mv_polynomial.eval₂_add MvPolynomial.eval₂_add
@[simp]
theorem eval₂_monomial : (monomial s a).eval₂ f g = f a * s.prod fun n e => g n ^ e :=
Finsupp.sum_single_index (by simp [f.map_zero])
#align mv_polynomial.eval₂_monomial MvPolynomial.eval₂_monomial
@[simp]
theorem eval₂_C (a) : (C a).eval₂ f g = f a := by
rw [C_apply, eval₂_monomial, prod_zero_index, mul_one]
#align mv_polynomial.eval₂_C MvPolynomial.eval₂_C
@[simp]
theorem eval₂_one : (1 : MvPolynomial σ R).eval₂ f g = 1 :=
(eval₂_C _ _ _).trans f.map_one
#align mv_polynomial.eval₂_one MvPolynomial.eval₂_one
@[simp]
theorem eval₂_X (n) : (X n).eval₂ f g = g n := by
simp [eval₂_monomial, f.map_one, X, prod_single_index, pow_one]
#align mv_polynomial.eval₂_X MvPolynomial.eval₂_X
theorem eval₂_mul_monomial :
∀ {s a}, (p * monomial s a).eval₂ f g = p.eval₂ f g * f a * s.prod fun n e => g n ^ e := by
classical
apply MvPolynomial.induction_on p
· intro a' s a
simp [C_mul_monomial, eval₂_monomial, f.map_mul]
· intro p q ih_p ih_q
simp [add_mul, eval₂_add, ih_p, ih_q]
· intro p n ih s a
exact
calc (p * X n * monomial s a).eval₂ f g
_ = (p * monomial (Finsupp.single n 1 + s) a).eval₂ f g := by
rw [monomial_single_add, pow_one, mul_assoc]
_ = (p * monomial (Finsupp.single n 1) 1).eval₂ f g * f a * s.prod fun n e => g n ^ e := by
simp [ih, prod_single_index, prod_add_index, pow_one, pow_add, mul_assoc, mul_left_comm,
f.map_one]
#align mv_polynomial.eval₂_mul_monomial MvPolynomial.eval₂_mul_monomial
theorem eval₂_mul_C : (p * C a).eval₂ f g = p.eval₂ f g * f a :=
(eval₂_mul_monomial _ _).trans <| by simp
#align mv_polynomial.eval₂_mul_C MvPolynomial.eval₂_mul_C
@[simp]
| Mathlib/Algebra/MvPolynomial/Basic.lean | 1,086 | 1,090 | theorem eval₂_mul : ∀ {p}, (p * q).eval₂ f g = p.eval₂ f g * q.eval₂ f g := by |
apply MvPolynomial.induction_on q
· simp [eval₂_C, eval₂_mul_C]
· simp (config := { contextual := true }) [mul_add, eval₂_add]
· simp (config := { contextual := true }) [X, eval₂_monomial, eval₂_mul_monomial, ← mul_assoc]
|
/-
Copyright (c) 2018 Mario Carneiro. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro
-/
import Mathlib.Algebra.Ring.Divisibility.Basic
import Mathlib.Init.Data.Ordering.Lemmas
import Mathlib.SetTheory.Ordinal.Principal
import Mathlib.Tactic.NormNum
#align_import set_theory.ordinal.notation from "leanprover-community/mathlib"@"b67044ba53af18680e1dd246861d9584e968495d"
/-!
# Ordinal notation
Constructive ordinal arithmetic for ordinals below `ε₀`.
We define a type `ONote`, with constructors `0 : ONote` and `ONote.oadd e n a` representing
`ω ^ e * n + a`.
We say that `o` is in Cantor normal form - `ONote.NF o` - if either `o = 0` or
`o = ω ^ e * n + a` with `a < ω ^ e` and `a` in Cantor normal form.
The type `NONote` is the type of ordinals below `ε₀` in Cantor normal form.
Various operations (addition, subtraction, multiplication, power function)
are defined on `ONote` and `NONote`.
-/
set_option linter.uppercaseLean3 false
open Ordinal Order
-- Porting note: the generated theorem is warned by `simpNF`.
set_option genSizeOfSpec false in
/-- Recursive definition of an ordinal notation. `zero` denotes the
ordinal 0, and `oadd e n a` is intended to refer to `ω^e * n + a`.
For this to be valid Cantor normal form, we must have the exponents
decrease to the right, but we can't state this condition until we've
defined `repr`, so it is a separate definition `NF`. -/
inductive ONote : Type
| zero : ONote
| oadd : ONote → ℕ+ → ONote → ONote
deriving DecidableEq
#align onote ONote
compile_inductive% ONote
namespace ONote
/-- Notation for 0 -/
instance : Zero ONote :=
⟨zero⟩
@[simp]
theorem zero_def : zero = 0 :=
rfl
#align onote.zero_def ONote.zero_def
instance : Inhabited ONote :=
⟨0⟩
/-- Notation for 1 -/
instance : One ONote :=
⟨oadd 0 1 0⟩
/-- Notation for ω -/
def omega : ONote :=
oadd 1 1 0
#align onote.omega ONote.omega
/-- The ordinal denoted by a notation -/
@[simp]
noncomputable def repr : ONote → Ordinal.{0}
| 0 => 0
| oadd e n a => ω ^ repr e * n + repr a
#align onote.repr ONote.repr
/-- Auxiliary definition to print an ordinal notation -/
def toStringAux1 (e : ONote) (n : ℕ) (s : String) : String :=
if e = 0 then toString n
else (if e = 1 then "ω" else "ω^(" ++ s ++ ")") ++ if n = 1 then "" else "*" ++ toString n
#align onote.to_string_aux1 ONote.toStringAux1
/-- Print an ordinal notation -/
def toString : ONote → String
| zero => "0"
| oadd e n 0 => toStringAux1 e n (toString e)
| oadd e n a => toStringAux1 e n (toString e) ++ " + " ++ toString a
#align onote.to_string ONote.toString
open Lean in
/-- Print an ordinal notation -/
def repr' (prec : ℕ) : ONote → Format
| zero => "0"
| oadd e n a =>
Repr.addAppParen
("oadd " ++ (repr' max_prec e) ++ " " ++ Nat.repr (n : ℕ) ++ " " ++ (repr' max_prec a))
prec
#align onote.repr' ONote.repr
instance : ToString ONote :=
⟨toString⟩
instance : Repr ONote where
reprPrec o prec := repr' prec o
instance : Preorder ONote where
le x y := repr x ≤ repr y
lt x y := repr x < repr y
le_refl _ := @le_refl Ordinal _ _
le_trans _ _ _ := @le_trans Ordinal _ _ _ _
lt_iff_le_not_le _ _ := @lt_iff_le_not_le Ordinal _ _ _
theorem lt_def {x y : ONote} : x < y ↔ repr x < repr y :=
Iff.rfl
#align onote.lt_def ONote.lt_def
theorem le_def {x y : ONote} : x ≤ y ↔ repr x ≤ repr y :=
Iff.rfl
#align onote.le_def ONote.le_def
instance : WellFoundedRelation ONote :=
⟨(· < ·), InvImage.wf repr Ordinal.lt_wf⟩
/-- Convert a `Nat` into an ordinal -/
@[coe]
def ofNat : ℕ → ONote
| 0 => 0
| Nat.succ n => oadd 0 n.succPNat 0
#align onote.of_nat ONote.ofNat
-- Porting note (#11467): during the port we marked these lemmas with `@[eqns]`
-- to emulate the old Lean 3 behaviour.
@[simp] theorem ofNat_zero : ofNat 0 = 0 :=
rfl
@[simp] theorem ofNat_succ (n) : ofNat (Nat.succ n) = oadd 0 n.succPNat 0 :=
rfl
instance nat (n : ℕ) : OfNat ONote n where
ofNat := ofNat n
@[simp 1200]
theorem ofNat_one : ofNat 1 = 1 :=
rfl
#align onote.of_nat_one ONote.ofNat_one
@[simp]
theorem repr_ofNat (n : ℕ) : repr (ofNat n) = n := by cases n <;> simp
#align onote.repr_of_nat ONote.repr_ofNat
-- @[simp] -- Porting note (#10618): simp can prove this
theorem repr_one : repr (ofNat 1) = (1 : ℕ) := repr_ofNat 1
#align onote.repr_one ONote.repr_one
theorem omega_le_oadd (e n a) : ω ^ repr e ≤ repr (oadd e n a) := by
refine le_trans ?_ (le_add_right _ _)
simpa using (Ordinal.mul_le_mul_iff_left <| opow_pos (repr e) omega_pos).2 (natCast_le.2 n.2)
#align onote.omega_le_oadd ONote.omega_le_oadd
theorem oadd_pos (e n a) : 0 < oadd e n a :=
@lt_of_lt_of_le _ _ _ (ω ^ repr e) _ (opow_pos (repr e) omega_pos) (omega_le_oadd e n a)
#align onote.oadd_pos ONote.oadd_pos
/-- Compare ordinal notations -/
def cmp : ONote → ONote → Ordering
| 0, 0 => Ordering.eq
| _, 0 => Ordering.gt
| 0, _ => Ordering.lt
| _o₁@(oadd e₁ n₁ a₁), _o₂@(oadd e₂ n₂ a₂) =>
(cmp e₁ e₂).orElse <| (_root_.cmp (n₁ : ℕ) n₂).orElse (cmp a₁ a₂)
#align onote.cmp ONote.cmp
theorem eq_of_cmp_eq : ∀ {o₁ o₂}, cmp o₁ o₂ = Ordering.eq → o₁ = o₂
| 0, 0, _ => rfl
| oadd e n a, 0, h => by injection h
| 0, oadd e n a, h => by injection h
| oadd e₁ n₁ a₁, oadd e₂ n₂ a₂, h => by
revert h; simp only [cmp]
cases h₁ : cmp e₁ e₂ <;> intro h <;> try cases h
obtain rfl := eq_of_cmp_eq h₁
revert h; cases h₂ : _root_.cmp (n₁ : ℕ) n₂ <;> intro h <;> try cases h
obtain rfl := eq_of_cmp_eq h
rw [_root_.cmp, cmpUsing_eq_eq] at h₂
obtain rfl := Subtype.eq (eq_of_incomp h₂)
simp
#align onote.eq_of_cmp_eq ONote.eq_of_cmp_eq
protected theorem zero_lt_one : (0 : ONote) < 1 := by
simp only [lt_def, repr, opow_zero, Nat.succPNat_coe, Nat.cast_one, mul_one, add_zero,
zero_lt_one]
#align onote.zero_lt_one ONote.zero_lt_one
/-- `NFBelow o b` says that `o` is a normal form ordinal notation
satisfying `repr o < ω ^ b`. -/
inductive NFBelow : ONote → Ordinal.{0} → Prop
| zero {b} : NFBelow 0 b
| oadd' {e n a eb b} : NFBelow e eb → NFBelow a (repr e) → repr e < b → NFBelow (oadd e n a) b
#align onote.NF_below ONote.NFBelow
/-- A normal form ordinal notation has the form
ω ^ a₁ * n₁ + ω ^ a₂ * n₂ + ... ω ^ aₖ * nₖ
where `a₁ > a₂ > ... > aₖ` and all the `aᵢ` are
also in normal form.
We will essentially only be interested in normal form
ordinal notations, but to avoid complicating the algorithms
we define everything over general ordinal notations and
only prove correctness with normal form as an invariant. -/
class NF (o : ONote) : Prop where
out : Exists (NFBelow o)
#align onote.NF ONote.NF
instance NF.zero : NF 0 :=
⟨⟨0, NFBelow.zero⟩⟩
#align onote.NF.zero ONote.NF.zero
theorem NFBelow.oadd {e n a b} : NF e → NFBelow a (repr e) → repr e < b → NFBelow (oadd e n a) b
| ⟨⟨_, h⟩⟩ => NFBelow.oadd' h
#align onote.NF_below.oadd ONote.NFBelow.oadd
theorem NFBelow.fst {e n a b} (h : NFBelow (ONote.oadd e n a) b) : NF e := by
cases' h with _ _ _ _ eb _ h₁ h₂ h₃; exact ⟨⟨_, h₁⟩⟩
#align onote.NF_below.fst ONote.NFBelow.fst
theorem NF.fst {e n a} : NF (oadd e n a) → NF e
| ⟨⟨_, h⟩⟩ => h.fst
#align onote.NF.fst ONote.NF.fst
theorem NFBelow.snd {e n a b} (h : NFBelow (ONote.oadd e n a) b) : NFBelow a (repr e) := by
cases' h with _ _ _ _ eb _ h₁ h₂ h₃; exact h₂
#align onote.NF_below.snd ONote.NFBelow.snd
theorem NF.snd' {e n a} : NF (oadd e n a) → NFBelow a (repr e)
| ⟨⟨_, h⟩⟩ => h.snd
#align onote.NF.snd' ONote.NF.snd'
theorem NF.snd {e n a} (h : NF (oadd e n a)) : NF a :=
⟨⟨_, h.snd'⟩⟩
#align onote.NF.snd ONote.NF.snd
theorem NF.oadd {e a} (h₁ : NF e) (n) (h₂ : NFBelow a (repr e)) : NF (oadd e n a) :=
⟨⟨_, NFBelow.oadd h₁ h₂ (lt_succ _)⟩⟩
#align onote.NF.oadd ONote.NF.oadd
instance NF.oadd_zero (e n) [h : NF e] : NF (ONote.oadd e n 0) :=
h.oadd _ NFBelow.zero
#align onote.NF.oadd_zero ONote.NF.oadd_zero
theorem NFBelow.lt {e n a b} (h : NFBelow (ONote.oadd e n a) b) : repr e < b := by
cases' h with _ _ _ _ eb _ h₁ h₂ h₃; exact h₃
#align onote.NF_below.lt ONote.NFBelow.lt
theorem NFBelow_zero : ∀ {o}, NFBelow o 0 ↔ o = 0
| 0 => ⟨fun _ => rfl, fun _ => NFBelow.zero⟩
| oadd _ _ _ =>
⟨fun h => (not_le_of_lt h.lt).elim (Ordinal.zero_le _), fun e => e.symm ▸ NFBelow.zero⟩
#align onote.NF_below_zero ONote.NFBelow_zero
theorem NF.zero_of_zero {e n a} (h : NF (ONote.oadd e n a)) (e0 : e = 0) : a = 0 := by
simpa [e0, NFBelow_zero] using h.snd'
#align onote.NF.zero_of_zero ONote.NF.zero_of_zero
theorem NFBelow.repr_lt {o b} (h : NFBelow o b) : repr o < ω ^ b := by
induction' h with _ e n a eb b h₁ h₂ h₃ _ IH
· exact opow_pos _ omega_pos
· rw [repr]
apply ((add_lt_add_iff_left _).2 IH).trans_le
rw [← mul_succ]
apply (mul_le_mul_left' (succ_le_of_lt (nat_lt_omega _)) _).trans
rw [← opow_succ]
exact opow_le_opow_right omega_pos (succ_le_of_lt h₃)
#align onote.NF_below.repr_lt ONote.NFBelow.repr_lt
theorem NFBelow.mono {o b₁ b₂} (bb : b₁ ≤ b₂) (h : NFBelow o b₁) : NFBelow o b₂ := by
induction' h with _ e n a eb b h₁ h₂ h₃ _ _ <;> constructor
exacts [h₁, h₂, lt_of_lt_of_le h₃ bb]
#align onote.NF_below.mono ONote.NFBelow.mono
theorem NF.below_of_lt {e n a b} (H : repr e < b) :
NF (ONote.oadd e n a) → NFBelow (ONote.oadd e n a) b
| ⟨⟨b', h⟩⟩ => by (cases' h with _ _ _ _ eb _ h₁ h₂ h₃; exact NFBelow.oadd' h₁ h₂ H)
#align onote.NF.below_of_lt ONote.NF.below_of_lt
theorem NF.below_of_lt' : ∀ {o b}, repr o < ω ^ b → NF o → NFBelow o b
| 0, _, _, _ => NFBelow.zero
| ONote.oadd _ _ _, _, H, h =>
h.below_of_lt <|
(opow_lt_opow_iff_right one_lt_omega).1 <| lt_of_le_of_lt (omega_le_oadd _ _ _) H
#align onote.NF.below_of_lt' ONote.NF.below_of_lt'
theorem nfBelow_ofNat : ∀ n, NFBelow (ofNat n) 1
| 0 => NFBelow.zero
| Nat.succ _ => NFBelow.oadd NF.zero NFBelow.zero zero_lt_one
#align onote.NF_below_of_nat ONote.nfBelow_ofNat
instance nf_ofNat (n) : NF (ofNat n) :=
⟨⟨_, nfBelow_ofNat n⟩⟩
#align onote.NF_of_nat ONote.nf_ofNat
instance nf_one : NF 1 := by rw [← ofNat_one]; infer_instance
#align onote.NF_one ONote.nf_one
theorem oadd_lt_oadd_1 {e₁ n₁ o₁ e₂ n₂ o₂} (h₁ : NF (oadd e₁ n₁ o₁)) (h : e₁ < e₂) :
oadd e₁ n₁ o₁ < oadd e₂ n₂ o₂ :=
@lt_of_lt_of_le _ _ (repr (oadd e₁ n₁ o₁)) _ _
(NF.below_of_lt h h₁).repr_lt (omega_le_oadd e₂ n₂ o₂)
#align onote.oadd_lt_oadd_1 ONote.oadd_lt_oadd_1
theorem oadd_lt_oadd_2 {e o₁ o₂ : ONote} {n₁ n₂ : ℕ+} (h₁ : NF (oadd e n₁ o₁)) (h : (n₁ : ℕ) < n₂) :
oadd e n₁ o₁ < oadd e n₂ o₂ := by
simp only [lt_def, repr]
refine lt_of_lt_of_le ((add_lt_add_iff_left _).2 h₁.snd'.repr_lt) (le_trans ?_ (le_add_right _ _))
rwa [← mul_succ,Ordinal.mul_le_mul_iff_left (opow_pos _ omega_pos), succ_le_iff, natCast_lt]
#align onote.oadd_lt_oadd_2 ONote.oadd_lt_oadd_2
theorem oadd_lt_oadd_3 {e n a₁ a₂} (h : a₁ < a₂) : oadd e n a₁ < oadd e n a₂ := by
rw [lt_def]; unfold repr
exact @add_lt_add_left _ _ _ _ (repr a₁) _ h _
#align onote.oadd_lt_oadd_3 ONote.oadd_lt_oadd_3
theorem cmp_compares : ∀ (a b : ONote) [NF a] [NF b], (cmp a b).Compares a b
| 0, 0, _, _ => rfl
| oadd e n a, 0, _, _ => oadd_pos _ _ _
| 0, oadd e n a, _, _ => oadd_pos _ _ _
| o₁@(oadd e₁ n₁ a₁), o₂@(oadd e₂ n₂ a₂), h₁, h₂ => by -- TODO: golf
rw [cmp]
have IHe := @cmp_compares _ _ h₁.fst h₂.fst
simp only [Ordering.Compares, gt_iff_lt] at IHe; revert IHe
cases cmp e₁ e₂
case lt => intro IHe; exact oadd_lt_oadd_1 h₁ IHe
case gt => intro IHe; exact oadd_lt_oadd_1 h₂ IHe
case eq =>
intro IHe; dsimp at IHe; subst IHe
unfold _root_.cmp; cases nh : cmpUsing (· < ·) (n₁ : ℕ) n₂ <;>
rw [cmpUsing, ite_eq_iff, not_lt] at nh
case lt =>
cases' nh with nh nh
· exact oadd_lt_oadd_2 h₁ nh.left
· rw [ite_eq_iff] at nh; cases' nh.right with nh nh <;> cases nh <;> contradiction
case gt =>
cases' nh with nh nh
· cases nh; contradiction
· cases' nh with _ nh
rw [ite_eq_iff] at nh; cases' nh with nh nh
· exact oadd_lt_oadd_2 h₂ nh.left
· cases nh; contradiction
cases' nh with nh nh
· cases nh; contradiction
cases' nh with nhl nhr
rw [ite_eq_iff] at nhr
cases' nhr with nhr nhr
· cases nhr; contradiction
obtain rfl := Subtype.eq (eq_of_incomp ⟨(not_lt_of_ge nhl), nhr.left⟩)
have IHa := @cmp_compares _ _ h₁.snd h₂.snd
revert IHa; cases cmp a₁ a₂ <;> intro IHa <;> dsimp at IHa
case lt => exact oadd_lt_oadd_3 IHa
case gt => exact oadd_lt_oadd_3 IHa
subst IHa; exact rfl
#align onote.cmp_compares ONote.cmp_compares
theorem repr_inj {a b} [NF a] [NF b] : repr a = repr b ↔ a = b :=
⟨fun e => match cmp a b, cmp_compares a b with
| Ordering.lt, (h : repr a < repr b) => (ne_of_lt h e).elim
| Ordering.gt, (h : repr a > repr b)=> (ne_of_gt h e).elim
| Ordering.eq, h => h,
congr_arg _⟩
#align onote.repr_inj ONote.repr_inj
theorem NF.of_dvd_omega_opow {b e n a} (h : NF (ONote.oadd e n a))
(d : ω ^ b ∣ repr (ONote.oadd e n a)) :
b ≤ repr e ∧ ω ^ b ∣ repr a := by
have := mt repr_inj.1 (fun h => by injection h : ONote.oadd e n a ≠ 0)
have L := le_of_not_lt fun l => not_le_of_lt (h.below_of_lt l).repr_lt (le_of_dvd this d)
simp only [repr] at d
exact ⟨L, (dvd_add_iff <| (opow_dvd_opow _ L).mul_right _).1 d⟩
#align onote.NF.of_dvd_omega_opow ONote.NF.of_dvd_omega_opow
theorem NF.of_dvd_omega {e n a} (h : NF (ONote.oadd e n a)) :
ω ∣ repr (ONote.oadd e n a) → repr e ≠ 0 ∧ ω ∣ repr a := by
(rw [← opow_one ω, ← one_le_iff_ne_zero]; exact h.of_dvd_omega_opow)
#align onote.NF.of_dvd_omega ONote.NF.of_dvd_omega
/-- `TopBelow b o` asserts that the largest exponent in `o`, if
it exists, is less than `b`. This is an auxiliary definition
for decidability of `NF`. -/
def TopBelow (b : ONote) : ONote → Prop
| 0 => True
| oadd e _ _ => cmp e b = Ordering.lt
#align onote.top_below ONote.TopBelow
instance decidableTopBelow : DecidableRel TopBelow := by
intro b o
cases o <;> delta TopBelow <;> infer_instance
#align onote.decidable_top_below ONote.decidableTopBelow
theorem nfBelow_iff_topBelow {b} [NF b] : ∀ {o}, NFBelow o (repr b) ↔ NF o ∧ TopBelow b o
| 0 => ⟨fun h => ⟨⟨⟨_, h⟩⟩, trivial⟩, fun _ => NFBelow.zero⟩
| oadd _ _ _ =>
⟨fun h => ⟨⟨⟨_, h⟩⟩, (@cmp_compares _ b h.fst _).eq_lt.2 h.lt⟩, fun ⟨h₁, h₂⟩ =>
h₁.below_of_lt <| (@cmp_compares _ b h₁.fst _).eq_lt.1 h₂⟩
#align onote.NF_below_iff_top_below ONote.nfBelow_iff_topBelow
instance decidableNF : DecidablePred NF
| 0 => isTrue NF.zero
| oadd e n a => by
have := decidableNF e
have := decidableNF a
apply decidable_of_iff (NF e ∧ NF a ∧ TopBelow e a)
rw [← and_congr_right fun h => @nfBelow_iff_topBelow _ h _]
exact ⟨fun ⟨h₁, h₂⟩ => NF.oadd h₁ n h₂, fun h => ⟨h.fst, h.snd'⟩⟩
#align onote.decidable_NF ONote.decidableNF
/-- Auxiliary definition for `add` -/
def addAux (e : ONote) (n : ℕ+) (o : ONote) : ONote :=
match o with
| 0 => oadd e n 0
| o'@(oadd e' n' a') =>
match cmp e e' with
| Ordering.lt => o'
| Ordering.eq => oadd e (n + n') a'
| Ordering.gt => oadd e n o'
/-- Addition of ordinal notations (correct only for normal input) -/
def add : ONote → ONote → ONote
| 0, o => o
| oadd e n a, o => addAux e n (add a o)
#align onote.add ONote.add
instance : Add ONote :=
⟨add⟩
@[simp]
theorem zero_add (o : ONote) : 0 + o = o :=
rfl
#align onote.zero_add ONote.zero_add
theorem oadd_add (e n a o) : oadd e n a + o = addAux e n (a + o) :=
rfl
#align onote.oadd_add ONote.oadd_add
/-- Subtraction of ordinal notations (correct only for normal input) -/
def sub : ONote → ONote → ONote
| 0, _ => 0
| o, 0 => o
| o₁@(oadd e₁ n₁ a₁), oadd e₂ n₂ a₂ =>
match cmp e₁ e₂ with
| Ordering.lt => 0
| Ordering.gt => o₁
| Ordering.eq =>
match (n₁ : ℕ) - n₂ with
| 0 => if n₁ = n₂ then sub a₁ a₂ else 0
| Nat.succ k => oadd e₁ k.succPNat a₁
#align onote.sub ONote.sub
instance : Sub ONote :=
⟨sub⟩
theorem add_nfBelow {b} : ∀ {o₁ o₂}, NFBelow o₁ b → NFBelow o₂ b → NFBelow (o₁ + o₂) b
| 0, _, _, h₂ => h₂
| oadd e n a, o, h₁, h₂ => by
have h' := add_nfBelow (h₁.snd.mono <| le_of_lt h₁.lt) h₂
simp [oadd_add]; revert h'; cases' a + o with e' n' a' <;> intro h'
· exact NFBelow.oadd h₁.fst NFBelow.zero h₁.lt
have : ((e.cmp e').Compares e e') := @cmp_compares _ _ h₁.fst h'.fst
cases h: cmp e e' <;> dsimp [addAux] <;> simp [h]
· exact h'
· simp [h] at this
subst e'
exact NFBelow.oadd h'.fst h'.snd h'.lt
· simp [h] at this
exact NFBelow.oadd h₁.fst (NF.below_of_lt this ⟨⟨_, h'⟩⟩) h₁.lt
#align onote.add_NF_below ONote.add_nfBelow
instance add_nf (o₁ o₂) : ∀ [NF o₁] [NF o₂], NF (o₁ + o₂)
| ⟨⟨b₁, h₁⟩⟩, ⟨⟨b₂, h₂⟩⟩ =>
⟨(le_total b₁ b₂).elim (fun h => ⟨b₂, add_nfBelow (h₁.mono h) h₂⟩) fun h =>
⟨b₁, add_nfBelow h₁ (h₂.mono h)⟩⟩
#align onote.add_NF ONote.add_nf
@[simp]
theorem repr_add : ∀ (o₁ o₂) [NF o₁] [NF o₂], repr (o₁ + o₂) = repr o₁ + repr o₂
| 0, o, _, _ => by simp
| oadd e n a, o, h₁, h₂ => by
haveI := h₁.snd; have h' := repr_add a o
conv_lhs at h' => simp [HAdd.hAdd, Add.add]
have nf := ONote.add_nf a o
conv at nf => simp [HAdd.hAdd, Add.add]
conv in _ + o => simp [HAdd.hAdd, Add.add]
cases' h : add a o with e' n' a' <;>
simp only [Add.add, add, addAux, h'.symm, h, add_assoc, repr] at nf h₁ ⊢
have := h₁.fst; haveI := nf.fst; have ee := cmp_compares e e'
cases he: cmp e e' <;> simp only [he, Ordering.compares_gt, Ordering.compares_lt,
Ordering.compares_eq, repr, gt_iff_lt, PNat.add_coe, Nat.cast_add] at ee ⊢
· rw [← add_assoc, @add_absorp _ (repr e') (ω ^ repr e' * (n' : ℕ))]
· have := (h₁.below_of_lt ee).repr_lt
unfold repr at this
cases he': e' <;> simp only [he', zero_def, opow_zero, repr, gt_iff_lt] at this ⊢ <;>
exact lt_of_le_of_lt (le_add_right _ _) this
· simpa using (Ordinal.mul_le_mul_iff_left <| opow_pos (repr e') omega_pos).2
(natCast_le.2 n'.pos)
· rw [ee, ← add_assoc, ← mul_add]
#align onote.repr_add ONote.repr_add
theorem sub_nfBelow : ∀ {o₁ o₂ b}, NFBelow o₁ b → NF o₂ → NFBelow (o₁ - o₂) b
| 0, o, b, _, h₂ => by cases o <;> exact NFBelow.zero
| oadd _ _ _, 0, _, h₁, _ => h₁
| oadd e₁ n₁ a₁, oadd e₂ n₂ a₂, b, h₁, h₂ => by
have h' := sub_nfBelow h₁.snd h₂.snd
simp only [HSub.hSub, Sub.sub, sub] at h' ⊢
have := @cmp_compares _ _ h₁.fst h₂.fst
cases h : cmp e₁ e₂ <;> simp [sub]
· apply NFBelow.zero
· simp only [h, Ordering.compares_eq] at this
subst e₂
cases (n₁ : ℕ) - n₂ <;> simp [sub]
· by_cases en : n₁ = n₂ <;> simp [en]
· exact h'.mono (le_of_lt h₁.lt)
· exact NFBelow.zero
· exact NFBelow.oadd h₁.fst h₁.snd h₁.lt
· exact h₁
#align onote.sub_NF_below ONote.sub_nfBelow
instance sub_nf (o₁ o₂) : ∀ [NF o₁] [NF o₂], NF (o₁ - o₂)
| ⟨⟨b₁, h₁⟩⟩, h₂ => ⟨⟨b₁, sub_nfBelow h₁ h₂⟩⟩
#align onote.sub_NF ONote.sub_nf
@[simp]
theorem repr_sub : ∀ (o₁ o₂) [NF o₁] [NF o₂], repr (o₁ - o₂) = repr o₁ - repr o₂
| 0, o, _, h₂ => by cases o <;> exact (Ordinal.zero_sub _).symm
| oadd e n a, 0, _, _ => (Ordinal.sub_zero _).symm
| oadd e₁ n₁ a₁, oadd e₂ n₂ a₂, h₁, h₂ => by
haveI := h₁.snd; haveI := h₂.snd; have h' := repr_sub a₁ a₂
conv_lhs at h' => dsimp [HSub.hSub, Sub.sub, sub]
conv_lhs => dsimp only [HSub.hSub, Sub.sub]; dsimp only [sub]
have ee := @cmp_compares _ _ h₁.fst h₂.fst
cases h : cmp e₁ e₂ <;> simp only [h] at ee
· rw [Ordinal.sub_eq_zero_iff_le.2]
· rfl
exact le_of_lt (oadd_lt_oadd_1 h₁ ee)
· change e₁ = e₂ at ee
subst e₂
dsimp only
cases mn : (n₁ : ℕ) - n₂ <;> dsimp only
· by_cases en : n₁ = n₂
· simpa [en]
· simp only [en, ite_false]
exact
(Ordinal.sub_eq_zero_iff_le.2 <|
le_of_lt <|
oadd_lt_oadd_2 h₁ <|
lt_of_le_of_ne (tsub_eq_zero_iff_le.1 mn) (mt PNat.eq en)).symm
· simp [Nat.succPNat]
rw [(tsub_eq_iff_eq_add_of_le <| le_of_lt <| Nat.lt_of_sub_eq_succ mn).1 mn, add_comm,
Nat.cast_add, mul_add, add_assoc, add_sub_add_cancel]
refine
(Ordinal.sub_eq_of_add_eq <|
add_absorp h₂.snd'.repr_lt <| le_trans ?_ (le_add_right _ _)).symm
simpa using mul_le_mul_left' (natCast_le.2 <| Nat.succ_pos _) _
· exact
(Ordinal.sub_eq_of_add_eq <|
add_absorp (h₂.below_of_lt ee).repr_lt <| omega_le_oadd _ _ _).symm
#align onote.repr_sub ONote.repr_sub
/-- Multiplication of ordinal notations (correct only for normal input) -/
def mul : ONote → ONote → ONote
| 0, _ => 0
| _, 0 => 0
| o₁@(oadd e₁ n₁ a₁), oadd e₂ n₂ a₂ =>
if e₂ = 0 then oadd e₁ (n₁ * n₂) a₁ else oadd (e₁ + e₂) n₂ (mul o₁ a₂)
#align onote.mul ONote.mul
instance : Mul ONote :=
⟨mul⟩
instance : MulZeroClass ONote where
mul := (· * ·)
zero := 0
zero_mul o := by cases o <;> rfl
mul_zero o := by cases o <;> rfl
theorem oadd_mul (e₁ n₁ a₁ e₂ n₂ a₂) :
oadd e₁ n₁ a₁ * oadd e₂ n₂ a₂ =
if e₂ = 0 then oadd e₁ (n₁ * n₂) a₁ else oadd (e₁ + e₂) n₂ (oadd e₁ n₁ a₁ * a₂) :=
rfl
#align onote.oadd_mul ONote.oadd_mul
theorem oadd_mul_nfBelow {e₁ n₁ a₁ b₁} (h₁ : NFBelow (oadd e₁ n₁ a₁) b₁) :
∀ {o₂ b₂}, NFBelow o₂ b₂ → NFBelow (oadd e₁ n₁ a₁ * o₂) (repr e₁ + b₂)
| 0, b₂, _ => NFBelow.zero
| oadd e₂ n₂ a₂, b₂, h₂ => by
have IH := oadd_mul_nfBelow h₁ h₂.snd
by_cases e0 : e₂ = 0 <;> simp [e0, oadd_mul]
· apply NFBelow.oadd h₁.fst h₁.snd
simpa using (add_lt_add_iff_left (repr e₁)).2 (lt_of_le_of_lt (Ordinal.zero_le _) h₂.lt)
· haveI := h₁.fst
haveI := h₂.fst
apply NFBelow.oadd
· infer_instance
· rwa [repr_add]
· rw [repr_add, add_lt_add_iff_left]
exact h₂.lt
#align onote.oadd_mul_NF_below ONote.oadd_mul_nfBelow
instance mul_nf : ∀ (o₁ o₂) [NF o₁] [NF o₂], NF (o₁ * o₂)
| 0, o, _, h₂ => by cases o <;> exact NF.zero
| oadd e n a, o, ⟨⟨b₁, hb₁⟩⟩, ⟨⟨b₂, hb₂⟩⟩ => ⟨⟨_, oadd_mul_nfBelow hb₁ hb₂⟩⟩
#align onote.mul_NF ONote.mul_nf
@[simp]
theorem repr_mul : ∀ (o₁ o₂) [NF o₁] [NF o₂], repr (o₁ * o₂) = repr o₁ * repr o₂
| 0, o, _, h₂ => by cases o <;> exact (zero_mul _).symm
| oadd e₁ n₁ a₁, 0, _, _ => (mul_zero _).symm
| oadd e₁ n₁ a₁, oadd e₂ n₂ a₂, h₁, h₂ => by
have IH : repr (mul _ _) = _ := @repr_mul _ _ h₁ h₂.snd
conv =>
lhs
simp [(· * ·)]
have ao : repr a₁ + ω ^ repr e₁ * (n₁ : ℕ) = ω ^ repr e₁ * (n₁ : ℕ) := by
apply add_absorp h₁.snd'.repr_lt
simpa using (Ordinal.mul_le_mul_iff_left <| opow_pos _ omega_pos).2 (natCast_le.2 n₁.2)
by_cases e0 : e₂ = 0 <;> simp [e0, mul]
· cases' Nat.exists_eq_succ_of_ne_zero n₂.ne_zero with x xe
simp only [xe, h₂.zero_of_zero e0, repr, add_zero]
rw [natCast_succ x, add_mul_succ _ ao, mul_assoc]
· haveI := h₁.fst
haveI := h₂.fst
simp only [Mul.mul, mul, e0, ite_false, repr.eq_2, repr_add, opow_add, IH, repr, mul_add]
rw [← mul_assoc]
congr 2
have := mt repr_inj.1 e0
rw [add_mul_limit ao (opow_isLimit_left omega_isLimit this), mul_assoc,
mul_omega_dvd (natCast_pos.2 n₁.pos) (nat_lt_omega _)]
simpa using opow_dvd_opow ω (one_le_iff_ne_zero.2 this)
#align onote.repr_mul ONote.repr_mul
/-- Calculate division and remainder of `o` mod ω.
`split' o = (a, n)` means `o = ω * a + n`. -/
def split' : ONote → ONote × ℕ
| 0 => (0, 0)
| oadd e n a =>
if e = 0 then (0, n)
else
let (a', m) := split' a
(oadd (e - 1) n a', m)
#align onote.split' ONote.split'
/-- Calculate division and remainder of `o` mod ω.
`split o = (a, n)` means `o = a + n`, where `ω ∣ a`. -/
def split : ONote → ONote × ℕ
| 0 => (0, 0)
| oadd e n a =>
if e = 0 then (0, n)
else
let (a', m) := split a
(oadd e n a', m)
#align onote.split ONote.split
/-- `scale x o` is the ordinal notation for `ω ^ x * o`. -/
def scale (x : ONote) : ONote → ONote
| 0 => 0
| oadd e n a => oadd (x + e) n (scale x a)
#align onote.scale ONote.scale
/-- `mulNat o n` is the ordinal notation for `o * n`. -/
def mulNat : ONote → ℕ → ONote
| 0, _ => 0
| _, 0 => 0
| oadd e n a, m + 1 => oadd e (n * m.succPNat) a
#align onote.mul_nat ONote.mulNat
/-- Auxiliary definition to compute the ordinal notation for the ordinal
exponentiation in `opow` -/
def opowAux (e a0 a : ONote) : ℕ → ℕ → ONote
| _, 0 => 0
| 0, m + 1 => oadd e m.succPNat 0
| k + 1, m => scale (e + mulNat a0 k) a + (opowAux e a0 a k m)
#align onote.opow_aux ONote.opowAux
/-- Auxiliary definition to compute the ordinal notation for the ordinal
exponentiation in `opow` -/
def opowAux2 (o₂ : ONote) (o₁ : ONote × ℕ) : ONote :=
match o₁ with
| (0, 0) => if o₂ = 0 then 1 else 0
| (0, 1) => 1
| (0, m + 1) =>
let (b', k) := split' o₂
oadd b' (m.succPNat ^ k) 0
| (a@(oadd a0 _ _), m) =>
match split o₂ with
| (b, 0) => oadd (a0 * b) 1 0
| (b, k + 1) =>
let eb := a0 * b
scale (eb + mulNat a0 k) a + opowAux eb a0 (mulNat a m) k m
/-- `opow o₁ o₂` calculates the ordinal notation for
the ordinal exponential `o₁ ^ o₂`. -/
def opow (o₁ o₂ : ONote) : ONote := opowAux2 o₂ (split o₁)
#align onote.opow ONote.opow
instance : Pow ONote ONote :=
⟨opow⟩
theorem opow_def (o₁ o₂ : ONote) : o₁ ^ o₂ = opowAux2 o₂ (split o₁) :=
rfl
#align onote.opow_def ONote.opow_def
theorem split_eq_scale_split' : ∀ {o o' m} [NF o], split' o = (o', m) → split o = (scale 1 o', m)
| 0, o', m, _, p => by injection p; substs o' m; rfl
| oadd e n a, o', m, h, p => by
by_cases e0 : e = 0 <;> simp [e0, split, split'] at p ⊢
· rcases p with ⟨rfl, rfl⟩
exact ⟨rfl, rfl⟩
· revert p
cases' h' : split' a with a' m'
haveI := h.fst
haveI := h.snd
simp only [split_eq_scale_split' h', and_imp]
have : 1 + (e - 1) = e := by
refine repr_inj.1 ?_
simp only [repr_add, repr, opow_zero, Nat.succPNat_coe, Nat.cast_one, mul_one, add_zero,
repr_sub]
have := mt repr_inj.1 e0
refine Ordinal.add_sub_cancel_of_le ?_
have := one_le_iff_ne_zero.2 this
exact this
intros
substs o' m
simp [scale, this]
#align onote.split_eq_scale_split' ONote.split_eq_scale_split'
theorem nf_repr_split' : ∀ {o o' m} [NF o], split' o = (o', m) → NF o' ∧ repr o = ω * repr o' + m
| 0, o', m, _, p => by injection p; substs o' m; simp [NF.zero]
| oadd e n a, o', m, h, p => by
by_cases e0 : e = 0 <;> simp [e0, split, split'] at p ⊢
· rcases p with ⟨rfl, rfl⟩
simp [h.zero_of_zero e0, NF.zero]
· revert p
cases' h' : split' a with a' m'
haveI := h.fst
haveI := h.snd
cases' nf_repr_split' h' with IH₁ IH₂
simp only [IH₂, and_imp]
intros
substs o' m
have : (ω : Ordinal.{0}) ^ repr e = ω ^ (1 : Ordinal.{0}) * ω ^ (repr e - 1) := by
have := mt repr_inj.1 e0
rw [← opow_add, Ordinal.add_sub_cancel_of_le (one_le_iff_ne_zero.2 this)]
refine ⟨NF.oadd (by infer_instance) _ ?_, ?_⟩
· simp at this ⊢
refine
IH₁.below_of_lt'
((Ordinal.mul_lt_mul_iff_left omega_pos).1 <| lt_of_le_of_lt (le_add_right _ m') ?_)
rw [← this, ← IH₂]
exact h.snd'.repr_lt
· rw [this]
simp [mul_add, mul_assoc, add_assoc]
#align onote.NF_repr_split' ONote.nf_repr_split'
theorem scale_eq_mul (x) [NF x] : ∀ (o) [NF o], scale x o = oadd x 1 0 * o
| 0, _ => rfl
| oadd e n a, h => by
simp only [HMul.hMul]; simp only [scale]
haveI := h.snd
by_cases e0 : e = 0
· simp_rw [scale_eq_mul]
simp [Mul.mul, mul, scale_eq_mul, e0, h.zero_of_zero,
show x + 0 = x from repr_inj.1 (by simp)]
· simp [e0, Mul.mul, mul, scale_eq_mul, (· * ·)]
#align onote.scale_eq_mul ONote.scale_eq_mul
instance nf_scale (x) [NF x] (o) [NF o] : NF (scale x o) := by
rw [scale_eq_mul]
infer_instance
#align onote.NF_scale ONote.nf_scale
@[simp]
theorem repr_scale (x) [NF x] (o) [NF o] : repr (scale x o) = ω ^ repr x * repr o := by
simp only [scale_eq_mul, repr_mul, repr, PNat.one_coe, Nat.cast_one, mul_one, add_zero]
#align onote.repr_scale ONote.repr_scale
theorem nf_repr_split {o o' m} [NF o] (h : split o = (o', m)) : NF o' ∧ repr o = repr o' + m := by
cases' e : split' o with a n
cases' nf_repr_split' e with s₁ s₂
rw [split_eq_scale_split' e] at h
injection h; substs o' n
simp only [repr_scale, repr, opow_zero, Nat.succPNat_coe, Nat.cast_one, mul_one, add_zero,
opow_one, s₂.symm, and_true]
infer_instance
#align onote.NF_repr_split ONote.nf_repr_split
theorem split_dvd {o o' m} [NF o] (h : split o = (o', m)) : ω ∣ repr o' := by
cases' e : split' o with a n
rw [split_eq_scale_split' e] at h
injection h; subst o'
cases nf_repr_split' e; simp
#align onote.split_dvd ONote.split_dvd
theorem split_add_lt {o e n a m} [NF o] (h : split o = (oadd e n a, m)) :
repr a + m < ω ^ repr e := by
cases' nf_repr_split h with h₁ h₂
cases' h₁.of_dvd_omega (split_dvd h) with e0 d
apply principal_add_omega_opow _ h₁.snd'.repr_lt (lt_of_lt_of_le (nat_lt_omega _) _)
simpa using opow_le_opow_right omega_pos (one_le_iff_ne_zero.2 e0)
#align onote.split_add_lt ONote.split_add_lt
@[simp]
theorem mulNat_eq_mul (n o) : mulNat o n = o * ofNat n := by cases o <;> cases n <;> rfl
#align onote.mul_nat_eq_mul ONote.mulNat_eq_mul
instance nf_mulNat (o) [NF o] (n) : NF (mulNat o n) := by simp; exact ONote.mul_nf o (ofNat n)
#align onote.NF_mul_nat ONote.nf_mulNat
instance nf_opowAux (e a0 a) [NF e] [NF a0] [NF a] : ∀ k m, NF (opowAux e a0 a k m) := by
intro k m
unfold opowAux
cases' m with m m
· cases k <;> exact NF.zero
cases' k with k k
· exact NF.oadd_zero _ _
· haveI := nf_opowAux e a0 a k
simp only [Nat.succ_ne_zero m, IsEmpty.forall_iff, mulNat_eq_mul]; infer_instance
#align onote.NF_opow_aux ONote.nf_opowAux
instance nf_opow (o₁ o₂) [NF o₁] [NF o₂] : NF (o₁ ^ o₂) := by
cases' e₁ : split o₁ with a m
have na := (nf_repr_split e₁).1
cases' e₂ : split' o₂ with b' k
haveI := (nf_repr_split' e₂).1
cases' a with a0 n a'
· cases' m with m
· by_cases o₂ = 0 <;> simp only [(· ^ ·), Pow.pow, pow, opow, opowAux2, *] <;> decide
· by_cases m = 0
· simp only [(· ^ ·), Pow.pow, pow, opow, opowAux2, *, zero_def]
decide
· simp only [(· ^ ·), Pow.pow, pow, opow, opowAux2, mulNat_eq_mul, ofNat, *]
infer_instance
· simp [(· ^ ·),Pow.pow,pow, opow, opowAux2, e₁, e₂, split_eq_scale_split' e₂]
have := na.fst
cases' k with k <;> simp
· infer_instance
· cases k <;> cases m <;> infer_instance
#align onote.NF_opow ONote.nf_opow
theorem scale_opowAux (e a0 a : ONote) [NF e] [NF a0] [NF a] :
∀ k m, repr (opowAux e a0 a k m) = ω ^ repr e * repr (opowAux 0 a0 a k m)
| 0, m => by cases m <;> simp [opowAux]
| k + 1, m => by
by_cases h : m = 0
· simp [h, opowAux, mul_add, opow_add, mul_assoc, scale_opowAux _ _ _ k]
· -- Porting note: rewrote proof
rw [opowAux]; swap
· assumption
rw [opowAux]; swap
· assumption
rw [repr_add, repr_scale, scale_opowAux _ _ _ k]
simp only [repr_add, repr_scale, opow_add, mul_assoc, zero_add, mul_add]
#align onote.scale_opow_aux ONote.scale_opowAux
theorem repr_opow_aux₁ {e a} [Ne : NF e] [Na : NF a] {a' : Ordinal} (e0 : repr e ≠ 0)
(h : a' < (ω : Ordinal.{0}) ^ repr e) (aa : repr a = a') (n : ℕ+) :
((ω : Ordinal.{0}) ^ repr e * (n : ℕ) + a') ^ (ω : Ordinal.{0}) =
(ω ^ repr e) ^ (ω : Ordinal.{0}) := by
subst aa
have No := Ne.oadd n (Na.below_of_lt' h)
have := omega_le_oadd e n a
rw [repr] at this
refine le_antisymm ?_ (opow_le_opow_left _ this)
apply (opow_le_of_limit ((opow_pos _ omega_pos).trans_le this).ne' omega_isLimit).2
intro b l
have := (No.below_of_lt (lt_succ _)).repr_lt
rw [repr] at this
apply (opow_le_opow_left b <| this.le).trans
rw [← opow_mul, ← opow_mul]
apply opow_le_opow_right omega_pos
rcases le_or_lt ω (repr e) with h | h
· apply (mul_le_mul_left' (le_succ b) _).trans
rw [← add_one_eq_succ, add_mul_succ _ (one_add_of_omega_le h), add_one_eq_succ, succ_le_iff,
Ordinal.mul_lt_mul_iff_left (Ordinal.pos_iff_ne_zero.2 e0)]
exact omega_isLimit.2 _ l
· apply (principal_mul_omega (omega_isLimit.2 _ h) l).le.trans
simpa using mul_le_mul_right' (one_le_iff_ne_zero.2 e0) ω
#align onote.repr_opow_aux₁ ONote.repr_opow_aux₁
section
-- Porting note: `R'` is used in the proof but marked as an unused variable.
set_option linter.unusedVariables false in
theorem repr_opow_aux₂ {a0 a'} [N0 : NF a0] [Na' : NF a'] (m : ℕ) (d : ω ∣ repr a')
(e0 : repr a0 ≠ 0) (h : repr a' + m < (ω ^ repr a0)) (n : ℕ+) (k : ℕ) :
let R := repr (opowAux 0 a0 (oadd a0 n a' * ofNat m) k m)
(k ≠ 0 → R < ((ω ^ repr a0) ^ succ (k : Ordinal))) ∧
((ω ^ repr a0) ^ (k : Ordinal)) * ((ω ^ repr a0) * (n : ℕ) + repr a') + R =
((ω ^ repr a0) * (n : ℕ) + repr a' + m) ^ succ (k : Ordinal) := by
intro R'
haveI No : NF (oadd a0 n a') :=
N0.oadd n (Na'.below_of_lt' <| lt_of_le_of_lt (le_add_right _ _) h)
induction' k with k IH
· cases m <;> simp [R', opowAux]
-- rename R => R'
let R := repr (opowAux 0 a0 (oadd a0 n a' * ofNat m) k m)
let ω0 := ω ^ repr a0
let α' := ω0 * n + repr a'
change (k ≠ 0 → R < (ω0 ^ succ (k : Ordinal))) ∧ (ω0 ^ (k : Ordinal)) * α' + R
= (α' + m) ^ (succ ↑k : Ordinal) at IH
have RR : R' = ω0 ^ (k : Ordinal) * (α' * m) + R := by
by_cases h : m = 0
· simp only [R, R', h, ONote.ofNat, Nat.cast_zero, zero_add, ONote.repr, mul_zero,
ONote.opowAux, add_zero]
· simp only [R', ONote.repr_scale, ONote.repr, ONote.mulNat_eq_mul, ONote.opowAux,
ONote.repr_ofNat, ONote.repr_mul, ONote.repr_add, Ordinal.opow_mul, ONote.zero_add]
have α0 : 0 < α' := by simpa [lt_def, repr] using oadd_pos a0 n a'
have ω00 : 0 < ω0 ^ (k : Ordinal) := opow_pos _ (opow_pos _ omega_pos)
have Rl : R < ω ^ (repr a0 * succ ↑k) := by
by_cases k0 : k = 0
· simp [R, k0]
refine lt_of_lt_of_le ?_ (opow_le_opow_right omega_pos (one_le_iff_ne_zero.2 e0))
cases' m with m <;> simp [opowAux, omega_pos]
rw [← add_one_eq_succ, ← Nat.cast_succ]
apply nat_lt_omega
· rw [opow_mul]
exact IH.1 k0
refine ⟨fun _ => ?_, ?_⟩
· rw [RR, ← opow_mul _ _ (succ k.succ)]
have e0 := Ordinal.pos_iff_ne_zero.2 e0
have rr0 : 0 < repr a0 + repr a0 := lt_of_lt_of_le e0 (le_add_left _ _)
apply principal_add_omega_opow
· simp [opow_mul, opow_add, mul_assoc]
rw [Ordinal.mul_lt_mul_iff_left ω00, ← Ordinal.opow_add]
have : _ < ω ^ (repr a0 + repr a0) := (No.below_of_lt ?_).repr_lt
· exact mul_lt_omega_opow rr0 this (nat_lt_omega _)
· simpa using (add_lt_add_iff_left (repr a0)).2 e0
· exact
lt_of_lt_of_le Rl
(opow_le_opow_right omega_pos <|
mul_le_mul_left' (succ_le_succ_iff.2 (natCast_le.2 (le_of_lt k.lt_succ_self))) _)
calc
(ω0 ^ (k.succ : Ordinal)) * α' + R'
_ = (ω0 ^ succ (k : Ordinal)) * α' + ((ω0 ^ (k : Ordinal)) * α' * m + R) := by
rw [natCast_succ, RR, ← mul_assoc]
_ = ((ω0 ^ (k : Ordinal)) * α' + R) * α' + ((ω0 ^ (k : Ordinal)) * α' + R) * m := ?_
_ = (α' + m) ^ succ (k.succ : Ordinal) := by rw [← mul_add, natCast_succ, opow_succ, IH.2]
congr 1
· have αd : ω ∣ α' :=
dvd_add (dvd_mul_of_dvd_left (by simpa using opow_dvd_opow ω (one_le_iff_ne_zero.2 e0)) _) d
rw [mul_add (ω0 ^ (k : Ordinal)), add_assoc, ← mul_assoc, ← opow_succ,
add_mul_limit _ (isLimit_iff_omega_dvd.2 ⟨ne_of_gt α0, αd⟩), mul_assoc,
@mul_omega_dvd n (natCast_pos.2 n.pos) (nat_lt_omega _) _ αd]
apply @add_absorp _ (repr a0 * succ ↑k)
· refine principal_add_omega_opow _ ?_ Rl
rw [opow_mul, opow_succ, Ordinal.mul_lt_mul_iff_left ω00]
exact No.snd'.repr_lt
· have := mul_le_mul_left' (one_le_iff_pos.2 <| natCast_pos.2 n.pos) (ω0 ^ succ (k : Ordinal))
rw [opow_mul]
simpa [-opow_succ]
· cases m
· have : R = 0 := by cases k <;> simp [R, opowAux]
simp [this]
· rw [natCast_succ, add_mul_succ]
apply add_absorp Rl
rw [opow_mul, opow_succ]
apply mul_le_mul_left'
simpa [repr] using omega_le_oadd a0 n a'
#align onote.repr_opow_aux₂ ONote.repr_opow_aux₂
end
theorem repr_opow (o₁ o₂) [NF o₁] [NF o₂] : repr (o₁ ^ o₂) = repr o₁ ^ repr o₂ := by
cases' e₁ : split o₁ with a m
cases' nf_repr_split e₁ with N₁ r₁
cases' a with a0 n a'
· cases' m with m
· by_cases h : o₂ = 0 <;> simp [opow_def, opowAux2, opow, e₁, h, r₁]
have := mt repr_inj.1 h
rw [zero_opow this]
· cases' e₂ : split' o₂ with b' k
cases' nf_repr_split' e₂ with _ r₂
by_cases h : m = 0
· simp [opow_def, opow, e₁, h, r₁, e₂, r₂, ← Nat.one_eq_succ_zero]
simp only [opow_def, opowAux2, opow, e₁, h, r₁, e₂, r₂, repr,
opow_zero, Nat.succPNat_coe, Nat.cast_succ, Nat.cast_zero, _root_.zero_add, mul_one,
add_zero, one_opow, npow_eq_pow]
rw [opow_add, opow_mul, opow_omega, add_one_eq_succ]
· congr
conv_lhs =>
dsimp [(· ^ ·)]
simp [Pow.pow, opow, Ordinal.succ_ne_zero]
· simpa [Nat.one_le_iff_ne_zero]
· rw [← Nat.cast_succ, lt_omega]
exact ⟨_, rfl⟩
· haveI := N₁.fst
haveI := N₁.snd
cases' N₁.of_dvd_omega (split_dvd e₁) with a00 ad
have al := split_add_lt e₁
have aa : repr (a' + ofNat m) = repr a' + m := by
simp only [eq_self_iff_true, ONote.repr_ofNat, ONote.repr_add]
cases' e₂ : split' o₂ with b' k
cases' nf_repr_split' e₂ with _ r₂
simp only [opow_def, opow, e₁, r₁, split_eq_scale_split' e₂, opowAux2, repr]
cases' k with k
· simp [r₂, opow_mul, repr_opow_aux₁ a00 al aa, add_assoc]
· simp? [r₂, opow_add, opow_mul, mul_assoc, add_assoc, -repr] says
simp only [mulNat_eq_mul, repr_add, repr_scale, repr_mul, repr_ofNat, opow_add, opow_mul,
mul_assoc, add_assoc, r₂, Nat.cast_add, Nat.cast_one, add_one_eq_succ, opow_succ]
simp only [repr, opow_zero, Nat.succPNat_coe, Nat.cast_one, mul_one, add_zero, opow_one]
rw [repr_opow_aux₁ a00 al aa, scale_opowAux]
simp only [repr_mul, repr_scale, repr, opow_zero, Nat.succPNat_coe, Nat.cast_one, mul_one,
add_zero, opow_one, opow_mul]
rw [← mul_add, ← add_assoc ((ω : Ordinal.{0}) ^ repr a0 * (n : ℕ))]
congr 1
rw [← opow_succ]
exact (repr_opow_aux₂ _ ad a00 al _ _).2
#align onote.repr_opow ONote.repr_opow
/-- Given an ordinal, returns `inl none` for `0`, `inl (some a)` for `a+1`, and
`inr f` for a limit ordinal `a`, where `f i` is a sequence converging to `a`. -/
def fundamentalSequence : ONote → Sum (Option ONote) (ℕ → ONote)
| zero => Sum.inl none
| oadd a m b =>
match fundamentalSequence b with
| Sum.inr f => Sum.inr fun i => oadd a m (f i)
| Sum.inl (some b') => Sum.inl (some (oadd a m b'))
| Sum.inl none =>
match fundamentalSequence a, m.natPred with
| Sum.inl none, 0 => Sum.inl (some zero)
| Sum.inl none, m + 1 => Sum.inl (some (oadd zero m.succPNat zero))
| Sum.inl (some a'), 0 => Sum.inr fun i => oadd a' i.succPNat zero
| Sum.inl (some a'), m + 1 => Sum.inr fun i => oadd a m.succPNat (oadd a' i.succPNat zero)
| Sum.inr f, 0 => Sum.inr fun i => oadd (f i) 1 zero
| Sum.inr f, m + 1 => Sum.inr fun i => oadd a m.succPNat (oadd (f i) 1 zero)
#align onote.fundamental_sequence ONote.fundamentalSequence
private theorem exists_lt_add {α} [hα : Nonempty α] {o : Ordinal} {f : α → Ordinal}
(H : ∀ ⦃a⦄, a < o → ∃ i, a < f i) {b : Ordinal} ⦃a⦄ (h : a < b + o) : ∃ i, a < b + f i := by
cases' lt_or_le a b with h h'
· obtain ⟨i⟩ := id hα
exact ⟨i, h.trans_le (le_add_right _ _)⟩
· rw [← Ordinal.add_sub_cancel_of_le h', add_lt_add_iff_left] at h
refine (H h).imp fun i H => ?_
rwa [← Ordinal.add_sub_cancel_of_le h', add_lt_add_iff_left]
private theorem exists_lt_mul_omega' {o : Ordinal} ⦃a⦄ (h : a < o * ω) :
∃ i : ℕ, a < o * ↑i + o := by
obtain ⟨i, hi, h'⟩ := (lt_mul_of_limit omega_isLimit).1 h
obtain ⟨i, rfl⟩ := lt_omega.1 hi
exact ⟨i, h'.trans_le (le_add_right _ _)⟩
private theorem exists_lt_omega_opow' {α} {o b : Ordinal} (hb : 1 < b) (ho : o.IsLimit)
{f : α → Ordinal} (H : ∀ ⦃a⦄, a < o → ∃ i, a < f i) ⦃a⦄ (h : a < b ^ o) :
∃ i, a < b ^ f i := by
obtain ⟨d, hd, h'⟩ := (lt_opow_of_limit (zero_lt_one.trans hb).ne' ho).1 h
exact (H hd).imp fun i hi => h'.trans <| (opow_lt_opow_iff_right hb).2 hi
/-- The property satisfied by `fundamentalSequence o`:
* `inl none` means `o = 0`
* `inl (some a)` means `o = succ a`
* `inr f` means `o` is a limit ordinal and `f` is a
strictly increasing sequence which converges to `o` -/
def FundamentalSequenceProp (o : ONote) : Sum (Option ONote) (ℕ → ONote) → Prop
| Sum.inl none => o = 0
| Sum.inl (some a) => o.repr = succ a.repr ∧ (o.NF → a.NF)
| Sum.inr f =>
o.repr.IsLimit ∧
(∀ i, f i < f (i + 1) ∧ f i < o ∧ (o.NF → (f i).NF)) ∧ ∀ a, a < o.repr → ∃ i, a < (f i).repr
#align onote.fundamental_sequence_prop ONote.FundamentalSequenceProp
theorem fundamentalSequenceProp_inl_none (o) :
FundamentalSequenceProp o (Sum.inl none) ↔ o = 0 :=
Iff.rfl
theorem fundamentalSequenceProp_inl_some (o a) :
FundamentalSequenceProp o (Sum.inl (some a)) ↔ o.repr = succ a.repr ∧ (o.NF → a.NF) :=
Iff.rfl
theorem fundamentalSequenceProp_inr (o f) :
FundamentalSequenceProp o (Sum.inr f) ↔
o.repr.IsLimit ∧
(∀ i, f i < f (i + 1) ∧ f i < o ∧ (o.NF → (f i).NF)) ∧
∀ a, a < o.repr → ∃ i, a < (f i).repr :=
Iff.rfl
attribute
[eqns
fundamentalSequenceProp_inl_none
fundamentalSequenceProp_inl_some
fundamentalSequenceProp_inr]
FundamentalSequenceProp
theorem fundamentalSequence_has_prop (o) : FundamentalSequenceProp o (fundamentalSequence o) := by
induction' o with a m b iha ihb; · exact rfl
rw [fundamentalSequence]
rcases e : b.fundamentalSequence with (⟨_ | b'⟩ | f) <;>
simp only [FundamentalSequenceProp] <;>
rw [e, FundamentalSequenceProp] at ihb
· rcases e : a.fundamentalSequence with (⟨_ | a'⟩ | f) <;> cases' e' : m.natPred with m' <;>
simp only [FundamentalSequenceProp] <;>
rw [e, FundamentalSequenceProp] at iha <;>
(try rw [show m = 1 by
have := PNat.natPred_add_one m; rw [e'] at this; exact PNat.coe_inj.1 this.symm]) <;>
(try rw [show m = (m' + 1).succPNat by
rw [← e', ← PNat.coe_inj, Nat.succPNat_coe, ← Nat.add_one, PNat.natPred_add_one]]) <;>
simp only [repr, iha, ihb, opow_lt_opow_iff_right one_lt_omega, add_lt_add_iff_left, add_zero,
eq_self_iff_true, lt_add_iff_pos_right, lt_def, mul_one, Nat.cast_zero, Nat.cast_succ,
Nat.succPNat_coe, opow_succ, opow_zero, mul_add_one, PNat.one_coe, succ_zero,
true_and_iff, _root_.zero_add, zero_def]
· decide
· exact ⟨rfl, inferInstance⟩
· have := opow_pos (repr a') omega_pos
refine
⟨mul_isLimit this omega_isLimit, fun i =>
⟨this, ?_, fun H => @NF.oadd_zero _ _ (iha.2 H.fst)⟩, exists_lt_mul_omega'⟩
rw [← mul_succ, ← natCast_succ, Ordinal.mul_lt_mul_iff_left this]
apply nat_lt_omega
· have := opow_pos (repr a') omega_pos
refine
⟨add_isLimit _ (mul_isLimit this omega_isLimit), fun i => ⟨this, ?_, ?_⟩,
exists_lt_add exists_lt_mul_omega'⟩
· rw [← mul_succ, ← natCast_succ, Ordinal.mul_lt_mul_iff_left this]
apply nat_lt_omega
· refine fun H => H.fst.oadd _ (NF.below_of_lt' ?_ (@NF.oadd_zero _ _ (iha.2 H.fst)))
rw [repr, ← zero_def, repr, add_zero, iha.1, opow_succ, Ordinal.mul_lt_mul_iff_left this]
apply nat_lt_omega
· rcases iha with ⟨h1, h2, h3⟩
refine ⟨opow_isLimit one_lt_omega h1, fun i => ?_, exists_lt_omega_opow' one_lt_omega h1 h3⟩
obtain ⟨h4, h5, h6⟩ := h2 i
exact ⟨h4, h5, fun H => @NF.oadd_zero _ _ (h6 H.fst)⟩
· rcases iha with ⟨h1, h2, h3⟩
refine
⟨add_isLimit _ (opow_isLimit one_lt_omega h1), fun i => ?_,
exists_lt_add (exists_lt_omega_opow' one_lt_omega h1 h3)⟩
obtain ⟨h4, h5, h6⟩ := h2 i
refine ⟨h4, h5, fun H => H.fst.oadd _ (NF.below_of_lt' ?_ (@NF.oadd_zero _ _ (h6 H.fst)))⟩
rwa [repr, ← zero_def, repr, add_zero, PNat.one_coe, Nat.cast_one, mul_one,
opow_lt_opow_iff_right one_lt_omega]
· refine ⟨by
rw [repr, ihb.1, add_succ, repr], fun H => H.fst.oadd _ (NF.below_of_lt' ?_ (ihb.2 H.snd))⟩
have := H.snd'.repr_lt
rw [ihb.1] at this
exact (lt_succ _).trans this
· rcases ihb with ⟨h1, h2, h3⟩
simp only [repr]
exact
⟨Ordinal.add_isLimit _ h1, fun i =>
⟨oadd_lt_oadd_3 (h2 i).1, oadd_lt_oadd_3 (h2 i).2.1, fun H =>
H.fst.oadd _ (NF.below_of_lt' (lt_trans (h2 i).2.1 H.snd'.repr_lt) ((h2 i).2.2 H.snd))⟩,
exists_lt_add h3⟩
#align onote.fundamental_sequence_has_prop ONote.fundamentalSequence_has_prop
/-- The fast growing hierarchy for ordinal notations `< ε₀`. This is a sequence of
functions `ℕ → ℕ` indexed by ordinals, with the definition:
* `f_0(n) = n + 1`
* `f_(α+1)(n) = f_α^[n](n)`
* `f_α(n) = f_(α[n])(n)` where `α` is a limit ordinal
and `α[i]` is the fundamental sequence converging to `α` -/
def fastGrowing : ONote → ℕ → ℕ
| o =>
match fundamentalSequence o, fundamentalSequence_has_prop o with
| Sum.inl none, _ => Nat.succ
| Sum.inl (some a), h =>
have : a < o := by rw [lt_def, h.1]; apply lt_succ
fun i => (fastGrowing a)^[i] i
| Sum.inr f, h => fun i =>
have : f i < o := (h.2.1 i).2.1
fastGrowing (f i) i
termination_by o => o
#align onote.fast_growing ONote.fastGrowing
-- Porting note: the bug of the linter, should be fixed.
@[nolint unusedHavesSuffices]
theorem fastGrowing_def {o : ONote} {x} (e : fundamentalSequence o = x) :
fastGrowing o =
match
(motive := (x : Option ONote ⊕ (ℕ → ONote)) → FundamentalSequenceProp o x → ℕ → ℕ)
x, e ▸ fundamentalSequence_has_prop o with
| Sum.inl none, _ => Nat.succ
| Sum.inl (some a), _ =>
fun i => (fastGrowing a)^[i] i
| Sum.inr f, _ => fun i =>
fastGrowing (f i) i := by
subst x
rw [fastGrowing]
#align onote.fast_growing_def ONote.fastGrowing_def
theorem fastGrowing_zero' (o : ONote) (h : fundamentalSequence o = Sum.inl none) :
fastGrowing o = Nat.succ := by
rw [fastGrowing_def h]
#align onote.fast_growing_zero' ONote.fastGrowing_zero'
theorem fastGrowing_succ (o) {a} (h : fundamentalSequence o = Sum.inl (some a)) :
fastGrowing o = fun i => (fastGrowing a)^[i] i := by
rw [fastGrowing_def h]
#align onote.fast_growing_succ ONote.fastGrowing_succ
theorem fastGrowing_limit (o) {f} (h : fundamentalSequence o = Sum.inr f) :
fastGrowing o = fun i => fastGrowing (f i) i := by
rw [fastGrowing_def h]
#align onote.fast_growing_limit ONote.fastGrowing_limit
@[simp]
theorem fastGrowing_zero : fastGrowing 0 = Nat.succ :=
fastGrowing_zero' _ rfl
#align onote.fast_growing_zero ONote.fastGrowing_zero
@[simp]
theorem fastGrowing_one : fastGrowing 1 = fun n => 2 * n := by
rw [@fastGrowing_succ 1 0 rfl]; funext i; rw [two_mul, fastGrowing_zero]
suffices ∀ a b, Nat.succ^[a] b = b + a from this _ _
intro a b; induction a <;> simp [*, Function.iterate_succ', Nat.add_assoc, -Function.iterate_succ]
#align onote.fast_growing_one ONote.fastGrowing_one
section
@[simp]
theorem fastGrowing_two : fastGrowing 2 = fun n => (2 ^ n) * n := by
rw [@fastGrowing_succ 2 1 rfl]; funext i; rw [fastGrowing_one]
suffices ∀ a b, (fun n : ℕ => 2 * n)^[a] b = (2 ^ a) * b from this _ _
intro a b; induction a <;>
simp [*, Function.iterate_succ, pow_succ, mul_assoc, -Function.iterate_succ]
#align onote.fast_growing_two ONote.fastGrowing_two
end
/-- We can extend the fast growing hierarchy one more step to `ε₀` itself,
using `ω^(ω^...^ω^0)` as the fundamental sequence converging to `ε₀` (which is not an `ONote`).
Extending the fast growing hierarchy beyond this requires a definition of fundamental sequence
for larger ordinals. -/
def fastGrowingε₀ (i : ℕ) : ℕ :=
fastGrowing ((fun a => a.oadd 1 0)^[i] 0) i
#align onote.fast_growing_ε₀ ONote.fastGrowingε₀
theorem fastGrowingε₀_zero : fastGrowingε₀ 0 = 1 := by simp [fastGrowingε₀]
#align onote.fast_growing_ε₀_zero ONote.fastGrowingε₀_zero
theorem fastGrowingε₀_one : fastGrowingε₀ 1 = 2 := by
simp [fastGrowingε₀, show oadd 0 1 0 = 1 from rfl]
#align onote.fast_growing_ε₀_one ONote.fastGrowingε₀_one
| Mathlib/SetTheory/Ordinal/Notation.lean | 1,240 | 1,242 | theorem fastGrowingε₀_two : fastGrowingε₀ 2 = 2048 := by |
norm_num [fastGrowingε₀, show oadd 0 1 0 = 1 from rfl, @fastGrowing_limit (oadd 1 1 0) _ rfl,
show oadd 0 (2 : Nat).succPNat 0 = 3 from rfl, @fastGrowing_succ 3 2 rfl]
|
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl
-/
import Mathlib.Algebra.BigOperators.Group.Finset
import Mathlib.Algebra.Order.BigOperators.Group.Multiset
import Mathlib.Tactic.NormNum.Basic
import Mathlib.Tactic.Positivity.Core
#align_import algebra.big_operators.order from "leanprover-community/mathlib"@"65a1391a0106c9204fe45bc73a039f056558cb83"
/-!
# Big operators on a finset in ordered groups
This file contains the results concerning the interaction of multiset big operators with ordered
groups/monoids.
-/
open Function
variable {ι α β M N G k R : Type*}
namespace Finset
section OrderedCommMonoid
variable [CommMonoid M] [OrderedCommMonoid N]
/-- Let `{x | p x}` be a subsemigroup of a commutative monoid `M`. Let `f : M → N` be a map
submultiplicative on `{x | p x}`, i.e., `p x → p y → f (x * y) ≤ f x * f y`. Let `g i`, `i ∈ s`, be
a nonempty finite family of elements of `M` such that `∀ i ∈ s, p (g i)`. Then
`f (∏ x ∈ s, g x) ≤ ∏ x ∈ s, f (g x)`. -/
@[to_additive le_sum_nonempty_of_subadditive_on_pred]
theorem le_prod_nonempty_of_submultiplicative_on_pred (f : M → N) (p : M → Prop)
(h_mul : ∀ x y, p x → p y → f (x * y) ≤ f x * f y) (hp_mul : ∀ x y, p x → p y → p (x * y))
(g : ι → M) (s : Finset ι) (hs_nonempty : s.Nonempty) (hs : ∀ i ∈ s, p (g i)) :
f (∏ i ∈ s, g i) ≤ ∏ i ∈ s, f (g i) := by
refine le_trans
(Multiset.le_prod_nonempty_of_submultiplicative_on_pred f p h_mul hp_mul _ ?_ ?_) ?_
· simp [hs_nonempty.ne_empty]
· exact Multiset.forall_mem_map_iff.mpr hs
rw [Multiset.map_map]
rfl
#align finset.le_prod_nonempty_of_submultiplicative_on_pred Finset.le_prod_nonempty_of_submultiplicative_on_pred
#align finset.le_sum_nonempty_of_subadditive_on_pred Finset.le_sum_nonempty_of_subadditive_on_pred
/-- Let `{x | p x}` be an additive subsemigroup of an additive commutative monoid `M`. Let
`f : M → N` be a map subadditive on `{x | p x}`, i.e., `p x → p y → f (x + y) ≤ f x + f y`. Let
`g i`, `i ∈ s`, be a nonempty finite family of elements of `M` such that `∀ i ∈ s, p (g i)`. Then
`f (∑ i ∈ s, g i) ≤ ∑ i ∈ s, f (g i)`. -/
add_decl_doc le_sum_nonempty_of_subadditive_on_pred
/-- If `f : M → N` is a submultiplicative function, `f (x * y) ≤ f x * f y` and `g i`, `i ∈ s`, is a
nonempty finite family of elements of `M`, then `f (∏ i ∈ s, g i) ≤ ∏ i ∈ s, f (g i)`. -/
@[to_additive le_sum_nonempty_of_subadditive]
theorem le_prod_nonempty_of_submultiplicative (f : M → N) (h_mul : ∀ x y, f (x * y) ≤ f x * f y)
{s : Finset ι} (hs : s.Nonempty) (g : ι → M) : f (∏ i ∈ s, g i) ≤ ∏ i ∈ s, f (g i) :=
le_prod_nonempty_of_submultiplicative_on_pred f (fun _ ↦ True) (fun x y _ _ ↦ h_mul x y)
(fun _ _ _ _ ↦ trivial) g s hs fun _ _ ↦ trivial
#align finset.le_prod_nonempty_of_submultiplicative Finset.le_prod_nonempty_of_submultiplicative
#align finset.le_sum_nonempty_of_subadditive Finset.le_sum_nonempty_of_subadditive
/-- If `f : M → N` is a subadditive function, `f (x + y) ≤ f x + f y` and `g i`, `i ∈ s`, is a
nonempty finite family of elements of `M`, then `f (∑ i ∈ s, g i) ≤ ∑ i ∈ s, f (g i)`. -/
add_decl_doc le_sum_nonempty_of_subadditive
/-- Let `{x | p x}` be a subsemigroup of a commutative monoid `M`. Let `f : M → N` be a map
such that `f 1 = 1` and `f` is submultiplicative on `{x | p x}`, i.e.,
`p x → p y → f (x * y) ≤ f x * f y`. Let `g i`, `i ∈ s`, be a finite family of elements of `M` such
that `∀ i ∈ s, p (g i)`. Then `f (∏ i ∈ s, g i) ≤ ∏ i ∈ s, f (g i)`. -/
@[to_additive le_sum_of_subadditive_on_pred]
theorem le_prod_of_submultiplicative_on_pred (f : M → N) (p : M → Prop) (h_one : f 1 = 1)
(h_mul : ∀ x y, p x → p y → f (x * y) ≤ f x * f y) (hp_mul : ∀ x y, p x → p y → p (x * y))
(g : ι → M) {s : Finset ι} (hs : ∀ i ∈ s, p (g i)) : f (∏ i ∈ s, g i) ≤ ∏ i ∈ s, f (g i) := by
rcases eq_empty_or_nonempty s with (rfl | hs_nonempty)
· simp [h_one]
· exact le_prod_nonempty_of_submultiplicative_on_pred f p h_mul hp_mul g s hs_nonempty hs
#align finset.le_prod_of_submultiplicative_on_pred Finset.le_prod_of_submultiplicative_on_pred
#align finset.le_sum_of_subadditive_on_pred Finset.le_sum_of_subadditive_on_pred
/-- Let `{x | p x}` be a subsemigroup of a commutative additive monoid `M`. Let `f : M → N` be a map
such that `f 0 = 0` and `f` is subadditive on `{x | p x}`, i.e. `p x → p y → f (x + y) ≤ f x + f y`.
Let `g i`, `i ∈ s`, be a finite family of elements of `M` such that `∀ i ∈ s, p (g i)`. Then
`f (∑ x ∈ s, g x) ≤ ∑ x ∈ s, f (g x)`. -/
add_decl_doc le_sum_of_subadditive_on_pred
/-- If `f : M → N` is a submultiplicative function, `f (x * y) ≤ f x * f y`, `f 1 = 1`, and `g i`,
`i ∈ s`, is a finite family of elements of `M`, then `f (∏ i ∈ s, g i) ≤ ∏ i ∈ s, f (g i)`. -/
@[to_additive le_sum_of_subadditive]
theorem le_prod_of_submultiplicative (f : M → N) (h_one : f 1 = 1)
(h_mul : ∀ x y, f (x * y) ≤ f x * f y) (s : Finset ι) (g : ι → M) :
f (∏ i ∈ s, g i) ≤ ∏ i ∈ s, f (g i) := by
refine le_trans (Multiset.le_prod_of_submultiplicative f h_one h_mul _) ?_
rw [Multiset.map_map]
rfl
#align finset.le_prod_of_submultiplicative Finset.le_prod_of_submultiplicative
#align finset.le_sum_of_subadditive Finset.le_sum_of_subadditive
/-- If `f : M → N` is a subadditive function, `f (x + y) ≤ f x + f y`, `f 0 = 0`, and `g i`,
`i ∈ s`, is a finite family of elements of `M`, then `f (∑ i ∈ s, g i) ≤ ∑ i ∈ s, f (g i)`. -/
add_decl_doc le_sum_of_subadditive
variable {f g : ι → N} {s t : Finset ι}
/-- In an ordered commutative monoid, if each factor `f i` of one finite product is less than or
equal to the corresponding factor `g i` of another finite product, then
`∏ i ∈ s, f i ≤ ∏ i ∈ s, g i`. -/
@[to_additive sum_le_sum]
theorem prod_le_prod' (h : ∀ i ∈ s, f i ≤ g i) : ∏ i ∈ s, f i ≤ ∏ i ∈ s, g i :=
Multiset.prod_map_le_prod_map f g h
#align finset.prod_le_prod' Finset.prod_le_prod'
#align finset.sum_le_sum Finset.sum_le_sum
/-- In an ordered additive commutative monoid, if each summand `f i` of one finite sum is less than
or equal to the corresponding summand `g i` of another finite sum, then
`∑ i ∈ s, f i ≤ ∑ i ∈ s, g i`. -/
add_decl_doc sum_le_sum
/-- In an ordered commutative monoid, if each factor `f i` of one finite product is less than or
equal to the corresponding factor `g i` of another finite product, then `s.prod f ≤ s.prod g`.
This is a variant (beta-reduced) version of the standard lemma `Finset.prod_le_prod'`, convenient
for the `gcongr` tactic. -/
@[to_additive (attr := gcongr) GCongr.sum_le_sum]
theorem _root_.GCongr.prod_le_prod' (h : ∀ i ∈ s, f i ≤ g i) : s.prod f ≤ s.prod g :=
s.prod_le_prod' h
/-- In an ordered additive commutative monoid, if each summand `f i` of one finite sum is less than
or equal to the corresponding summand `g i` of another finite sum, then `s.sum f ≤ s.sum g`.
This is a variant (beta-reduced) version of the standard lemma `Finset.sum_le_sum`, convenient
for the `gcongr` tactic. -/
add_decl_doc GCongr.sum_le_sum
@[to_additive sum_nonneg]
theorem one_le_prod' (h : ∀ i ∈ s, 1 ≤ f i) : 1 ≤ ∏ i ∈ s, f i :=
le_trans (by rw [prod_const_one]) (prod_le_prod' h)
#align finset.one_le_prod' Finset.one_le_prod'
#align finset.sum_nonneg Finset.sum_nonneg
@[to_additive Finset.sum_nonneg']
theorem one_le_prod'' (h : ∀ i : ι, 1 ≤ f i) : 1 ≤ ∏ i ∈ s, f i :=
Finset.one_le_prod' fun i _ ↦ h i
#align finset.one_le_prod'' Finset.one_le_prod''
#align finset.sum_nonneg' Finset.sum_nonneg'
@[to_additive sum_nonpos]
theorem prod_le_one' (h : ∀ i ∈ s, f i ≤ 1) : ∏ i ∈ s, f i ≤ 1 :=
(prod_le_prod' h).trans_eq (by rw [prod_const_one])
#align finset.prod_le_one' Finset.prod_le_one'
#align finset.sum_nonpos Finset.sum_nonpos
@[to_additive sum_le_sum_of_subset_of_nonneg]
theorem prod_le_prod_of_subset_of_one_le' (h : s ⊆ t) (hf : ∀ i ∈ t, i ∉ s → 1 ≤ f i) :
∏ i ∈ s, f i ≤ ∏ i ∈ t, f i := by
classical calc
∏ i ∈ s, f i ≤ (∏ i ∈ t \ s, f i) * ∏ i ∈ s, f i :=
le_mul_of_one_le_left' <| one_le_prod' <| by simpa only [mem_sdiff, and_imp]
_ = ∏ i ∈ t \ s ∪ s, f i := (prod_union sdiff_disjoint).symm
_ = ∏ i ∈ t, f i := by rw [sdiff_union_of_subset h]
#align finset.prod_le_prod_of_subset_of_one_le' Finset.prod_le_prod_of_subset_of_one_le'
#align finset.sum_le_sum_of_subset_of_nonneg Finset.sum_le_sum_of_subset_of_nonneg
@[to_additive sum_mono_set_of_nonneg]
theorem prod_mono_set_of_one_le' (hf : ∀ x, 1 ≤ f x) : Monotone fun s ↦ ∏ x ∈ s, f x :=
fun _ _ hst ↦ prod_le_prod_of_subset_of_one_le' hst fun x _ _ ↦ hf x
#align finset.prod_mono_set_of_one_le' Finset.prod_mono_set_of_one_le'
#align finset.sum_mono_set_of_nonneg Finset.sum_mono_set_of_nonneg
@[to_additive sum_le_univ_sum_of_nonneg]
theorem prod_le_univ_prod_of_one_le' [Fintype ι] {s : Finset ι} (w : ∀ x, 1 ≤ f x) :
∏ x ∈ s, f x ≤ ∏ x, f x :=
prod_le_prod_of_subset_of_one_le' (subset_univ s) fun a _ _ ↦ w a
#align finset.prod_le_univ_prod_of_one_le' Finset.prod_le_univ_prod_of_one_le'
#align finset.sum_le_univ_sum_of_nonneg Finset.sum_le_univ_sum_of_nonneg
-- Porting note (#11215): TODO -- The two next lemmas give the same lemma in additive version
@[to_additive sum_eq_zero_iff_of_nonneg]
| Mathlib/Algebra/Order/BigOperators/Group/Finset.lean | 180 | 188 | theorem prod_eq_one_iff_of_one_le' :
(∀ i ∈ s, 1 ≤ f i) → ((∏ i ∈ s, f i) = 1 ↔ ∀ i ∈ s, f i = 1) := by |
classical
refine Finset.induction_on s
(fun _ ↦ ⟨fun _ _ h ↦ False.elim (Finset.not_mem_empty _ h), fun _ ↦ rfl⟩) ?_
intro a s ha ih H
have : ∀ i ∈ s, 1 ≤ f i := fun _ ↦ H _ ∘ mem_insert_of_mem
rw [prod_insert ha, mul_eq_one_iff' (H _ <| mem_insert_self _ _) (one_le_prod' this),
forall_mem_insert, ih this]
|
/-
Copyright (c) 2018 Sébastien Gouëzel. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Sébastien Gouëzel
-/
import Mathlib.Topology.MetricSpace.Antilipschitz
#align_import topology.metric_space.isometry from "leanprover-community/mathlib"@"b1859b6d4636fdbb78c5d5cefd24530653cfd3eb"
/-!
# Isometries
We define isometries, i.e., maps between emetric spaces that preserve
the edistance (on metric spaces, these are exactly the maps that preserve distances),
and prove their basic properties. We also introduce isometric bijections.
Since a lot of elementary properties don't require `eq_of_dist_eq_zero` we start setting up the
theory for `PseudoMetricSpace` and we specialize to `MetricSpace` when needed.
-/
noncomputable section
universe u v w
variable {ι : Type*} {α : Type u} {β : Type v} {γ : Type w}
open Function Set
open scoped Topology ENNReal
/-- An isometry (also known as isometric embedding) is a map preserving the edistance
between pseudoemetric spaces, or equivalently the distance between pseudometric space. -/
def Isometry [PseudoEMetricSpace α] [PseudoEMetricSpace β] (f : α → β) : Prop :=
∀ x1 x2 : α, edist (f x1) (f x2) = edist x1 x2
#align isometry Isometry
/-- On pseudometric spaces, a map is an isometry if and only if it preserves nonnegative
distances. -/
theorem isometry_iff_nndist_eq [PseudoMetricSpace α] [PseudoMetricSpace β] {f : α → β} :
Isometry f ↔ ∀ x y, nndist (f x) (f y) = nndist x y := by
simp only [Isometry, edist_nndist, ENNReal.coe_inj]
#align isometry_iff_nndist_eq isometry_iff_nndist_eq
/-- On pseudometric spaces, a map is an isometry if and only if it preserves distances. -/
theorem isometry_iff_dist_eq [PseudoMetricSpace α] [PseudoMetricSpace β] {f : α → β} :
Isometry f ↔ ∀ x y, dist (f x) (f y) = dist x y := by
simp only [isometry_iff_nndist_eq, ← coe_nndist, NNReal.coe_inj]
#align isometry_iff_dist_eq isometry_iff_dist_eq
/-- An isometry preserves distances. -/
alias ⟨Isometry.dist_eq, _⟩ := isometry_iff_dist_eq
#align isometry.dist_eq Isometry.dist_eq
/-- A map that preserves distances is an isometry -/
alias ⟨_, Isometry.of_dist_eq⟩ := isometry_iff_dist_eq
#align isometry.of_dist_eq Isometry.of_dist_eq
/-- An isometry preserves non-negative distances. -/
alias ⟨Isometry.nndist_eq, _⟩ := isometry_iff_nndist_eq
#align isometry.nndist_eq Isometry.nndist_eq
/-- A map that preserves non-negative distances is an isometry. -/
alias ⟨_, Isometry.of_nndist_eq⟩ := isometry_iff_nndist_eq
#align isometry.of_nndist_eq Isometry.of_nndist_eq
namespace Isometry
section PseudoEmetricIsometry
variable [PseudoEMetricSpace α] [PseudoEMetricSpace β] [PseudoEMetricSpace γ]
variable {f : α → β} {x y z : α} {s : Set α}
/-- An isometry preserves edistances. -/
theorem edist_eq (hf : Isometry f) (x y : α) : edist (f x) (f y) = edist x y :=
hf x y
#align isometry.edist_eq Isometry.edist_eq
theorem lipschitz (h : Isometry f) : LipschitzWith 1 f :=
LipschitzWith.of_edist_le fun x y => (h x y).le
#align isometry.lipschitz Isometry.lipschitz
theorem antilipschitz (h : Isometry f) : AntilipschitzWith 1 f := fun x y => by
simp only [h x y, ENNReal.coe_one, one_mul, le_refl]
#align isometry.antilipschitz Isometry.antilipschitz
/-- Any map on a subsingleton is an isometry -/
@[nontriviality]
theorem _root_.isometry_subsingleton [Subsingleton α] : Isometry f := fun x y => by
rw [Subsingleton.elim x y]; simp
#align isometry_subsingleton isometry_subsingleton
/-- The identity is an isometry -/
theorem _root_.isometry_id : Isometry (id : α → α) := fun _ _ => rfl
#align isometry_id isometry_id
theorem prod_map {δ} [PseudoEMetricSpace δ] {f : α → β} {g : γ → δ} (hf : Isometry f)
(hg : Isometry g) : Isometry (Prod.map f g) := fun x y => by
simp only [Prod.edist_eq, hf.edist_eq, hg.edist_eq, Prod.map_apply]
#align isometry.prod_map Isometry.prod_map
theorem _root_.isometry_dcomp {ι} [Fintype ι] {α β : ι → Type*} [∀ i, PseudoEMetricSpace (α i)]
[∀ i, PseudoEMetricSpace (β i)] (f : ∀ i, α i → β i) (hf : ∀ i, Isometry (f i)) :
Isometry (fun g : (i : ι) → α i => fun i => f i (g i)) := fun x y => by
simp only [edist_pi_def, (hf _).edist_eq]
#align isometry_dcomp isometry_dcomp
/-- The composition of isometries is an isometry. -/
theorem comp {g : β → γ} {f : α → β} (hg : Isometry g) (hf : Isometry f) : Isometry (g ∘ f) :=
fun _ _ => (hg _ _).trans (hf _ _)
#align isometry.comp Isometry.comp
/-- An isometry from a metric space is a uniform continuous map -/
protected theorem uniformContinuous (hf : Isometry f) : UniformContinuous f :=
hf.lipschitz.uniformContinuous
#align isometry.uniform_continuous Isometry.uniformContinuous
/-- An isometry from a metric space is a uniform inducing map -/
protected theorem uniformInducing (hf : Isometry f) : UniformInducing f :=
hf.antilipschitz.uniformInducing hf.uniformContinuous
#align isometry.uniform_inducing Isometry.uniformInducing
theorem tendsto_nhds_iff {ι : Type*} {f : α → β} {g : ι → α} {a : Filter ι} {b : α}
(hf : Isometry f) : Filter.Tendsto g a (𝓝 b) ↔ Filter.Tendsto (f ∘ g) a (𝓝 (f b)) :=
hf.uniformInducing.inducing.tendsto_nhds_iff
#align isometry.tendsto_nhds_iff Isometry.tendsto_nhds_iff
/-- An isometry is continuous. -/
protected theorem continuous (hf : Isometry f) : Continuous f :=
hf.lipschitz.continuous
#align isometry.continuous Isometry.continuous
/-- The right inverse of an isometry is an isometry. -/
theorem right_inv {f : α → β} {g : β → α} (h : Isometry f) (hg : RightInverse g f) : Isometry g :=
fun x y => by rw [← h, hg _, hg _]
#align isometry.right_inv Isometry.right_inv
theorem preimage_emetric_closedBall (h : Isometry f) (x : α) (r : ℝ≥0∞) :
f ⁻¹' EMetric.closedBall (f x) r = EMetric.closedBall x r := by
ext y
simp [h.edist_eq]
#align isometry.preimage_emetric_closed_ball Isometry.preimage_emetric_closedBall
theorem preimage_emetric_ball (h : Isometry f) (x : α) (r : ℝ≥0∞) :
f ⁻¹' EMetric.ball (f x) r = EMetric.ball x r := by
ext y
simp [h.edist_eq]
#align isometry.preimage_emetric_ball Isometry.preimage_emetric_ball
/-- Isometries preserve the diameter in pseudoemetric spaces. -/
theorem ediam_image (hf : Isometry f) (s : Set α) : EMetric.diam (f '' s) = EMetric.diam s :=
eq_of_forall_ge_iff fun d => by simp only [EMetric.diam_le_iff, forall_mem_image, hf.edist_eq]
#align isometry.ediam_image Isometry.ediam_image
theorem ediam_range (hf : Isometry f) : EMetric.diam (range f) = EMetric.diam (univ : Set α) := by
rw [← image_univ]
exact hf.ediam_image univ
#align isometry.ediam_range Isometry.ediam_range
theorem mapsTo_emetric_ball (hf : Isometry f) (x : α) (r : ℝ≥0∞) :
MapsTo f (EMetric.ball x r) (EMetric.ball (f x) r) :=
(hf.preimage_emetric_ball x r).ge
#align isometry.maps_to_emetric_ball Isometry.mapsTo_emetric_ball
theorem mapsTo_emetric_closedBall (hf : Isometry f) (x : α) (r : ℝ≥0∞) :
MapsTo f (EMetric.closedBall x r) (EMetric.closedBall (f x) r) :=
(hf.preimage_emetric_closedBall x r).ge
#align isometry.maps_to_emetric_closed_ball Isometry.mapsTo_emetric_closedBall
/-- The injection from a subtype is an isometry -/
theorem _root_.isometry_subtype_coe {s : Set α} : Isometry ((↑) : s → α) := fun _ _ => rfl
#align isometry_subtype_coe isometry_subtype_coe
theorem comp_continuousOn_iff {γ} [TopologicalSpace γ] (hf : Isometry f) {g : γ → α} {s : Set γ} :
ContinuousOn (f ∘ g) s ↔ ContinuousOn g s :=
hf.uniformInducing.inducing.continuousOn_iff.symm
#align isometry.comp_continuous_on_iff Isometry.comp_continuousOn_iff
theorem comp_continuous_iff {γ} [TopologicalSpace γ] (hf : Isometry f) {g : γ → α} :
Continuous (f ∘ g) ↔ Continuous g :=
hf.uniformInducing.inducing.continuous_iff.symm
#align isometry.comp_continuous_iff Isometry.comp_continuous_iff
end PseudoEmetricIsometry
--section
section EmetricIsometry
variable [EMetricSpace α] [PseudoEMetricSpace β] {f : α → β}
/-- An isometry from an emetric space is injective -/
protected theorem injective (h : Isometry f) : Injective f :=
h.antilipschitz.injective
#align isometry.injective Isometry.injective
/-- An isometry from an emetric space is a uniform embedding -/
protected theorem uniformEmbedding (hf : Isometry f) : UniformEmbedding f :=
hf.antilipschitz.uniformEmbedding hf.lipschitz.uniformContinuous
#align isometry.uniform_embedding Isometry.uniformEmbedding
/-- An isometry from an emetric space is an embedding -/
protected theorem embedding (hf : Isometry f) : Embedding f :=
hf.uniformEmbedding.embedding
#align isometry.embedding Isometry.embedding
/-- An isometry from a complete emetric space is a closed embedding -/
theorem closedEmbedding [CompleteSpace α] [EMetricSpace γ] {f : α → γ} (hf : Isometry f) :
ClosedEmbedding f :=
hf.antilipschitz.closedEmbedding hf.lipschitz.uniformContinuous
#align isometry.closed_embedding Isometry.closedEmbedding
end EmetricIsometry
--section
section PseudoMetricIsometry
variable [PseudoMetricSpace α] [PseudoMetricSpace β] {f : α → β}
/-- An isometry preserves the diameter in pseudometric spaces. -/
theorem diam_image (hf : Isometry f) (s : Set α) : Metric.diam (f '' s) = Metric.diam s := by
rw [Metric.diam, Metric.diam, hf.ediam_image]
#align isometry.diam_image Isometry.diam_image
theorem diam_range (hf : Isometry f) : Metric.diam (range f) = Metric.diam (univ : Set α) := by
rw [← image_univ]
exact hf.diam_image univ
#align isometry.diam_range Isometry.diam_range
theorem preimage_setOf_dist (hf : Isometry f) (x : α) (p : ℝ → Prop) :
f ⁻¹' { y | p (dist y (f x)) } = { y | p (dist y x) } := by
ext y
simp [hf.dist_eq]
#align isometry.preimage_set_of_dist Isometry.preimage_setOf_dist
theorem preimage_closedBall (hf : Isometry f) (x : α) (r : ℝ) :
f ⁻¹' Metric.closedBall (f x) r = Metric.closedBall x r :=
hf.preimage_setOf_dist x (· ≤ r)
#align isometry.preimage_closed_ball Isometry.preimage_closedBall
theorem preimage_ball (hf : Isometry f) (x : α) (r : ℝ) :
f ⁻¹' Metric.ball (f x) r = Metric.ball x r :=
hf.preimage_setOf_dist x (· < r)
#align isometry.preimage_ball Isometry.preimage_ball
theorem preimage_sphere (hf : Isometry f) (x : α) (r : ℝ) :
f ⁻¹' Metric.sphere (f x) r = Metric.sphere x r :=
hf.preimage_setOf_dist x (· = r)
#align isometry.preimage_sphere Isometry.preimage_sphere
theorem mapsTo_ball (hf : Isometry f) (x : α) (r : ℝ) :
MapsTo f (Metric.ball x r) (Metric.ball (f x) r) :=
(hf.preimage_ball x r).ge
#align isometry.maps_to_ball Isometry.mapsTo_ball
theorem mapsTo_sphere (hf : Isometry f) (x : α) (r : ℝ) :
MapsTo f (Metric.sphere x r) (Metric.sphere (f x) r) :=
(hf.preimage_sphere x r).ge
#align isometry.maps_to_sphere Isometry.mapsTo_sphere
theorem mapsTo_closedBall (hf : Isometry f) (x : α) (r : ℝ) :
MapsTo f (Metric.closedBall x r) (Metric.closedBall (f x) r) :=
(hf.preimage_closedBall x r).ge
#align isometry.maps_to_closed_ball Isometry.mapsTo_closedBall
end PseudoMetricIsometry
-- section
end Isometry
-- namespace
/-- A uniform embedding from a uniform space to a metric space is an isometry with respect to the
induced metric space structure on the source space. -/
theorem UniformEmbedding.to_isometry {α β} [UniformSpace α] [MetricSpace β] {f : α → β}
(h : UniformEmbedding f) : (letI := h.comapMetricSpace f; Isometry f) :=
let _ := h.comapMetricSpace f
Isometry.of_dist_eq fun _ _ => rfl
#align uniform_embedding.to_isometry UniformEmbedding.to_isometry
/-- An embedding from a topological space to a metric space is an isometry with respect to the
induced metric space structure on the source space. -/
theorem Embedding.to_isometry {α β} [TopologicalSpace α] [MetricSpace β] {f : α → β}
(h : Embedding f) : (letI := h.comapMetricSpace f; Isometry f) :=
let _ := h.comapMetricSpace f
Isometry.of_dist_eq fun _ _ => rfl
#align embedding.to_isometry Embedding.to_isometry
-- such a bijection need not exist
/-- `α` and `β` are isometric if there is an isometric bijection between them. -/
-- Porting note(#5171): was @[nolint has_nonempty_instance]
structure IsometryEquiv (α : Type u) (β : Type v) [PseudoEMetricSpace α] [PseudoEMetricSpace β]
extends α ≃ β where
isometry_toFun : Isometry toFun
#align isometry_equiv IsometryEquiv
@[inherit_doc]
infixl:25 " ≃ᵢ " => IsometryEquiv
namespace IsometryEquiv
section PseudoEMetricSpace
variable [PseudoEMetricSpace α] [PseudoEMetricSpace β] [PseudoEMetricSpace γ]
-- Porting note (#11215): TODO: add `IsometryEquivClass`
theorem toEquiv_injective : Injective (toEquiv : (α ≃ᵢ β) → (α ≃ β))
| ⟨_, _⟩, ⟨_, _⟩, rfl => rfl
#align isometry_equiv.to_equiv_inj IsometryEquiv.toEquiv_injective
@[simp] theorem toEquiv_inj {e₁ e₂ : α ≃ᵢ β} : e₁.toEquiv = e₂.toEquiv ↔ e₁ = e₂ :=
toEquiv_injective.eq_iff
instance : EquivLike (α ≃ᵢ β) α β where
coe e := e.toEquiv
inv e := e.toEquiv.symm
left_inv e := e.left_inv
right_inv e := e.right_inv
coe_injective' _ _ h _ := toEquiv_injective <| DFunLike.ext' h
theorem coe_eq_toEquiv (h : α ≃ᵢ β) (a : α) : h a = h.toEquiv a := rfl
#align isometry_equiv.coe_eq_to_equiv IsometryEquiv.coe_eq_toEquiv
@[simp] theorem coe_toEquiv (h : α ≃ᵢ β) : ⇑h.toEquiv = h := rfl
#align isometry_equiv.coe_to_equiv IsometryEquiv.coe_toEquiv
@[simp] theorem coe_mk (e : α ≃ β) (h) : ⇑(mk e h) = e := rfl
protected theorem isometry (h : α ≃ᵢ β) : Isometry h :=
h.isometry_toFun
#align isometry_equiv.isometry IsometryEquiv.isometry
protected theorem bijective (h : α ≃ᵢ β) : Bijective h :=
h.toEquiv.bijective
#align isometry_equiv.bijective IsometryEquiv.bijective
protected theorem injective (h : α ≃ᵢ β) : Injective h :=
h.toEquiv.injective
#align isometry_equiv.injective IsometryEquiv.injective
protected theorem surjective (h : α ≃ᵢ β) : Surjective h :=
h.toEquiv.surjective
#align isometry_equiv.surjective IsometryEquiv.surjective
protected theorem edist_eq (h : α ≃ᵢ β) (x y : α) : edist (h x) (h y) = edist x y :=
h.isometry.edist_eq x y
#align isometry_equiv.edist_eq IsometryEquiv.edist_eq
protected theorem dist_eq {α β : Type*} [PseudoMetricSpace α] [PseudoMetricSpace β] (h : α ≃ᵢ β)
(x y : α) : dist (h x) (h y) = dist x y :=
h.isometry.dist_eq x y
#align isometry_equiv.dist_eq IsometryEquiv.dist_eq
protected theorem nndist_eq {α β : Type*} [PseudoMetricSpace α] [PseudoMetricSpace β] (h : α ≃ᵢ β)
(x y : α) : nndist (h x) (h y) = nndist x y :=
h.isometry.nndist_eq x y
#align isometry_equiv.nndist_eq IsometryEquiv.nndist_eq
protected theorem continuous (h : α ≃ᵢ β) : Continuous h :=
h.isometry.continuous
#align isometry_equiv.continuous IsometryEquiv.continuous
@[simp]
theorem ediam_image (h : α ≃ᵢ β) (s : Set α) : EMetric.diam (h '' s) = EMetric.diam s :=
h.isometry.ediam_image s
#align isometry_equiv.ediam_image IsometryEquiv.ediam_image
@[ext]
theorem ext ⦃h₁ h₂ : α ≃ᵢ β⦄ (H : ∀ x, h₁ x = h₂ x) : h₁ = h₂ :=
DFunLike.ext _ _ H
#align isometry_equiv.ext IsometryEquiv.ext
/-- Alternative constructor for isometric bijections,
taking as input an isometry, and a right inverse. -/
def mk' {α : Type u} [EMetricSpace α] (f : α → β) (g : β → α) (hfg : ∀ x, f (g x) = x)
(hf : Isometry f) : α ≃ᵢ β where
toFun := f
invFun := g
left_inv _ := hf.injective <| hfg _
right_inv := hfg
isometry_toFun := hf
#align isometry_equiv.mk' IsometryEquiv.mk'
/-- The identity isometry of a space. -/
protected def refl (α : Type*) [PseudoEMetricSpace α] : α ≃ᵢ α :=
{ Equiv.refl α with isometry_toFun := isometry_id }
#align isometry_equiv.refl IsometryEquiv.refl
/-- The composition of two isometric isomorphisms, as an isometric isomorphism. -/
protected def trans (h₁ : α ≃ᵢ β) (h₂ : β ≃ᵢ γ) : α ≃ᵢ γ :=
{ Equiv.trans h₁.toEquiv h₂.toEquiv with
isometry_toFun := h₂.isometry_toFun.comp h₁.isometry_toFun }
#align isometry_equiv.trans IsometryEquiv.trans
@[simp]
theorem trans_apply (h₁ : α ≃ᵢ β) (h₂ : β ≃ᵢ γ) (x : α) : h₁.trans h₂ x = h₂ (h₁ x) :=
rfl
#align isometry_equiv.trans_apply IsometryEquiv.trans_apply
/-- The inverse of an isometric isomorphism, as an isometric isomorphism. -/
protected def symm (h : α ≃ᵢ β) : β ≃ᵢ α where
isometry_toFun := h.isometry.right_inv h.right_inv
toEquiv := h.toEquiv.symm
#align isometry_equiv.symm IsometryEquiv.symm
/-- See Note [custom simps projection]. We need to specify this projection explicitly in this case,
because it is a composition of multiple projections. -/
def Simps.apply (h : α ≃ᵢ β) : α → β := h
#align isometry_equiv.simps.apply IsometryEquiv.Simps.apply
/-- See Note [custom simps projection] -/
def Simps.symm_apply (h : α ≃ᵢ β) : β → α :=
h.symm
#align isometry_equiv.simps.symm_apply IsometryEquiv.Simps.symm_apply
initialize_simps_projections IsometryEquiv (toEquiv_toFun → apply, toEquiv_invFun → symm_apply)
@[simp]
theorem symm_symm (h : α ≃ᵢ β) : h.symm.symm = h := rfl
#align isometry_equiv.symm_symm IsometryEquiv.symm_symm
theorem symm_bijective : Bijective (IsometryEquiv.symm : (α ≃ᵢ β) → β ≃ᵢ α) :=
Function.bijective_iff_has_inverse.mpr ⟨_, symm_symm, symm_symm⟩
@[simp]
theorem apply_symm_apply (h : α ≃ᵢ β) (y : β) : h (h.symm y) = y :=
h.toEquiv.apply_symm_apply y
#align isometry_equiv.apply_symm_apply IsometryEquiv.apply_symm_apply
@[simp]
theorem symm_apply_apply (h : α ≃ᵢ β) (x : α) : h.symm (h x) = x :=
h.toEquiv.symm_apply_apply x
#align isometry_equiv.symm_apply_apply IsometryEquiv.symm_apply_apply
theorem symm_apply_eq (h : α ≃ᵢ β) {x : α} {y : β} : h.symm y = x ↔ y = h x :=
h.toEquiv.symm_apply_eq
#align isometry_equiv.symm_apply_eq IsometryEquiv.symm_apply_eq
theorem eq_symm_apply (h : α ≃ᵢ β) {x : α} {y : β} : x = h.symm y ↔ h x = y :=
h.toEquiv.eq_symm_apply
#align isometry_equiv.eq_symm_apply IsometryEquiv.eq_symm_apply
theorem symm_comp_self (h : α ≃ᵢ β) : (h.symm : β → α) ∘ h = id := funext h.left_inv
#align isometry_equiv.symm_comp_self IsometryEquiv.symm_comp_self
theorem self_comp_symm (h : α ≃ᵢ β) : (h : α → β) ∘ h.symm = id := funext h.right_inv
#align isometry_equiv.self_comp_symm IsometryEquiv.self_comp_symm
@[simp]
theorem range_eq_univ (h : α ≃ᵢ β) : range h = univ :=
h.toEquiv.range_eq_univ
#align isometry_equiv.range_eq_univ IsometryEquiv.range_eq_univ
theorem image_symm (h : α ≃ᵢ β) : image h.symm = preimage h :=
image_eq_preimage_of_inverse h.symm.toEquiv.left_inv h.symm.toEquiv.right_inv
#align isometry_equiv.image_symm IsometryEquiv.image_symm
theorem preimage_symm (h : α ≃ᵢ β) : preimage h.symm = image h :=
(image_eq_preimage_of_inverse h.toEquiv.left_inv h.toEquiv.right_inv).symm
#align isometry_equiv.preimage_symm IsometryEquiv.preimage_symm
@[simp]
theorem symm_trans_apply (h₁ : α ≃ᵢ β) (h₂ : β ≃ᵢ γ) (x : γ) :
(h₁.trans h₂).symm x = h₁.symm (h₂.symm x) :=
rfl
#align isometry_equiv.symm_trans_apply IsometryEquiv.symm_trans_apply
theorem ediam_univ (h : α ≃ᵢ β) : EMetric.diam (univ : Set α) = EMetric.diam (univ : Set β) := by
rw [← h.range_eq_univ, h.isometry.ediam_range]
#align isometry_equiv.ediam_univ IsometryEquiv.ediam_univ
@[simp]
theorem ediam_preimage (h : α ≃ᵢ β) (s : Set β) : EMetric.diam (h ⁻¹' s) = EMetric.diam s := by
rw [← image_symm, ediam_image]
#align isometry_equiv.ediam_preimage IsometryEquiv.ediam_preimage
@[simp]
theorem preimage_emetric_ball (h : α ≃ᵢ β) (x : β) (r : ℝ≥0∞) :
h ⁻¹' EMetric.ball x r = EMetric.ball (h.symm x) r := by
rw [← h.isometry.preimage_emetric_ball (h.symm x) r, h.apply_symm_apply]
#align isometry_equiv.preimage_emetric_ball IsometryEquiv.preimage_emetric_ball
@[simp]
theorem preimage_emetric_closedBall (h : α ≃ᵢ β) (x : β) (r : ℝ≥0∞) :
h ⁻¹' EMetric.closedBall x r = EMetric.closedBall (h.symm x) r := by
rw [← h.isometry.preimage_emetric_closedBall (h.symm x) r, h.apply_symm_apply]
#align isometry_equiv.preimage_emetric_closed_ball IsometryEquiv.preimage_emetric_closedBall
@[simp]
theorem image_emetric_ball (h : α ≃ᵢ β) (x : α) (r : ℝ≥0∞) :
h '' EMetric.ball x r = EMetric.ball (h x) r := by
rw [← h.preimage_symm, h.symm.preimage_emetric_ball, symm_symm]
#align isometry_equiv.image_emetric_ball IsometryEquiv.image_emetric_ball
@[simp]
theorem image_emetric_closedBall (h : α ≃ᵢ β) (x : α) (r : ℝ≥0∞) :
h '' EMetric.closedBall x r = EMetric.closedBall (h x) r := by
rw [← h.preimage_symm, h.symm.preimage_emetric_closedBall, symm_symm]
#align isometry_equiv.image_emetric_closed_ball IsometryEquiv.image_emetric_closedBall
/-- The (bundled) homeomorphism associated to an isometric isomorphism. -/
@[simps toEquiv]
protected def toHomeomorph (h : α ≃ᵢ β) : α ≃ₜ β where
continuous_toFun := h.continuous
continuous_invFun := h.symm.continuous
toEquiv := h.toEquiv
#align isometry_equiv.to_homeomorph IsometryEquiv.toHomeomorph
#align isometry_equiv.to_homeomorph_to_equiv IsometryEquiv.toHomeomorph_toEquiv
@[simp]
theorem coe_toHomeomorph (h : α ≃ᵢ β) : ⇑h.toHomeomorph = h :=
rfl
#align isometry_equiv.coe_to_homeomorph IsometryEquiv.coe_toHomeomorph
@[simp]
theorem coe_toHomeomorph_symm (h : α ≃ᵢ β) : ⇑h.toHomeomorph.symm = h.symm :=
rfl
#align isometry_equiv.coe_to_homeomorph_symm IsometryEquiv.coe_toHomeomorph_symm
@[simp]
theorem comp_continuousOn_iff {γ} [TopologicalSpace γ] (h : α ≃ᵢ β) {f : γ → α} {s : Set γ} :
ContinuousOn (h ∘ f) s ↔ ContinuousOn f s :=
h.toHomeomorph.comp_continuousOn_iff _ _
#align isometry_equiv.comp_continuous_on_iff IsometryEquiv.comp_continuousOn_iff
@[simp]
theorem comp_continuous_iff {γ} [TopologicalSpace γ] (h : α ≃ᵢ β) {f : γ → α} :
Continuous (h ∘ f) ↔ Continuous f :=
h.toHomeomorph.comp_continuous_iff
#align isometry_equiv.comp_continuous_iff IsometryEquiv.comp_continuous_iff
@[simp]
theorem comp_continuous_iff' {γ} [TopologicalSpace γ] (h : α ≃ᵢ β) {f : β → γ} :
Continuous (f ∘ h) ↔ Continuous f :=
h.toHomeomorph.comp_continuous_iff'
#align isometry_equiv.comp_continuous_iff' IsometryEquiv.comp_continuous_iff'
/-- The group of isometries. -/
instance : Group (α ≃ᵢ α) where
one := IsometryEquiv.refl _
mul e₁ e₂ := e₂.trans e₁
inv := IsometryEquiv.symm
mul_assoc e₁ e₂ e₃ := rfl
one_mul e := ext fun _ => rfl
mul_one e := ext fun _ => rfl
mul_left_inv e := ext e.symm_apply_apply
@[simp] theorem coe_one : ⇑(1 : α ≃ᵢ α) = id := rfl
#align isometry_equiv.coe_one IsometryEquiv.coe_one
@[simp] theorem coe_mul (e₁ e₂ : α ≃ᵢ α) : ⇑(e₁ * e₂) = e₁ ∘ e₂ := rfl
#align isometry_equiv.coe_mul IsometryEquiv.coe_mul
theorem mul_apply (e₁ e₂ : α ≃ᵢ α) (x : α) : (e₁ * e₂) x = e₁ (e₂ x) := rfl
#align isometry_equiv.mul_apply IsometryEquiv.mul_apply
@[simp] theorem inv_apply_self (e : α ≃ᵢ α) (x : α) : e⁻¹ (e x) = x := e.symm_apply_apply x
#align isometry_equiv.inv_apply_self IsometryEquiv.inv_apply_self
@[simp] theorem apply_inv_self (e : α ≃ᵢ α) (x : α) : e (e⁻¹ x) = x := e.apply_symm_apply x
#align isometry_equiv.apply_inv_self IsometryEquiv.apply_inv_self
theorem completeSpace_iff (e : α ≃ᵢ β) : CompleteSpace α ↔ CompleteSpace β := by
simp only [completeSpace_iff_isComplete_univ, ← e.range_eq_univ, ← image_univ,
isComplete_image_iff e.isometry.uniformInducing]
#align isometry_equiv.complete_space_iff IsometryEquiv.completeSpace_iff
protected theorem completeSpace [CompleteSpace β] (e : α ≃ᵢ β) : CompleteSpace α :=
e.completeSpace_iff.2 ‹_›
#align isometry_equiv.complete_space IsometryEquiv.completeSpace
variable (ι α)
/-- `Equiv.funUnique` as an `IsometryEquiv`. -/
@[simps!]
def funUnique [Unique ι] [Fintype ι] : (ι → α) ≃ᵢ α where
toEquiv := Equiv.funUnique ι α
isometry_toFun x hx := by simp [edist_pi_def, Finset.univ_unique, Finset.sup_singleton]
#align isometry_equiv.fun_unique IsometryEquiv.funUnique
/-- `piFinTwoEquiv` as an `IsometryEquiv`. -/
@[simps!]
def piFinTwo (α : Fin 2 → Type*) [∀ i, PseudoEMetricSpace (α i)] : (∀ i, α i) ≃ᵢ α 0 × α 1 where
toEquiv := piFinTwoEquiv α
isometry_toFun x hx := by simp [edist_pi_def, Fin.univ_succ, Prod.edist_eq]
#align isometry_equiv.pi_fin_two IsometryEquiv.piFinTwo
end PseudoEMetricSpace
section PseudoMetricSpace
variable [PseudoMetricSpace α] [PseudoMetricSpace β] (h : α ≃ᵢ β)
@[simp]
theorem diam_image (s : Set α) : Metric.diam (h '' s) = Metric.diam s :=
h.isometry.diam_image s
#align isometry_equiv.diam_image IsometryEquiv.diam_image
@[simp]
theorem diam_preimage (s : Set β) : Metric.diam (h ⁻¹' s) = Metric.diam s := by
rw [← image_symm, diam_image]
#align isometry_equiv.diam_preimage IsometryEquiv.diam_preimage
theorem diam_univ : Metric.diam (univ : Set α) = Metric.diam (univ : Set β) :=
congr_arg ENNReal.toReal h.ediam_univ
#align isometry_equiv.diam_univ IsometryEquiv.diam_univ
@[simp]
theorem preimage_ball (h : α ≃ᵢ β) (x : β) (r : ℝ) :
h ⁻¹' Metric.ball x r = Metric.ball (h.symm x) r := by
rw [← h.isometry.preimage_ball (h.symm x) r, h.apply_symm_apply]
#align isometry_equiv.preimage_ball IsometryEquiv.preimage_ball
@[simp]
theorem preimage_sphere (h : α ≃ᵢ β) (x : β) (r : ℝ) :
h ⁻¹' Metric.sphere x r = Metric.sphere (h.symm x) r := by
rw [← h.isometry.preimage_sphere (h.symm x) r, h.apply_symm_apply]
#align isometry_equiv.preimage_sphere IsometryEquiv.preimage_sphere
@[simp]
theorem preimage_closedBall (h : α ≃ᵢ β) (x : β) (r : ℝ) :
h ⁻¹' Metric.closedBall x r = Metric.closedBall (h.symm x) r := by
rw [← h.isometry.preimage_closedBall (h.symm x) r, h.apply_symm_apply]
#align isometry_equiv.preimage_closed_ball IsometryEquiv.preimage_closedBall
@[simp]
theorem image_ball (h : α ≃ᵢ β) (x : α) (r : ℝ) : h '' Metric.ball x r = Metric.ball (h x) r := by
rw [← h.preimage_symm, h.symm.preimage_ball, symm_symm]
#align isometry_equiv.image_ball IsometryEquiv.image_ball
@[simp]
theorem image_sphere (h : α ≃ᵢ β) (x : α) (r : ℝ) :
h '' Metric.sphere x r = Metric.sphere (h x) r := by
rw [← h.preimage_symm, h.symm.preimage_sphere, symm_symm]
#align isometry_equiv.image_sphere IsometryEquiv.image_sphere
@[simp]
| Mathlib/Topology/MetricSpace/Isometry.lean | 637 | 639 | theorem image_closedBall (h : α ≃ᵢ β) (x : α) (r : ℝ) :
h '' Metric.closedBall x r = Metric.closedBall (h x) r := by |
rw [← h.preimage_symm, h.symm.preimage_closedBall, symm_symm]
|
/-
Copyright (c) 2022 Anne Baanen. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Anne Baanen
-/
import Mathlib.RingTheory.DedekindDomain.Ideal
#align_import number_theory.ramification_inertia from "leanprover-community/mathlib"@"039a089d2a4b93c761b234f3e5f5aeb752bac60f"
/-!
# Ramification index and inertia degree
Given `P : Ideal S` lying over `p : Ideal R` for the ring extension `f : R →+* S`
(assuming `P` and `p` are prime or maximal where needed),
the **ramification index** `Ideal.ramificationIdx f p P` is the multiplicity of `P` in `map f p`,
and the **inertia degree** `Ideal.inertiaDeg f p P` is the degree of the field extension
`(S / P) : (R / p)`.
## Main results
The main theorem `Ideal.sum_ramification_inertia` states that for all coprime `P` lying over `p`,
`Σ P, ramification_idx f p P * inertia_deg f p P` equals the degree of the field extension
`Frac(S) : Frac(R)`.
## Implementation notes
Often the above theory is set up in the case where:
* `R` is the ring of integers of a number field `K`,
* `L` is a finite separable extension of `K`,
* `S` is the integral closure of `R` in `L`,
* `p` and `P` are maximal ideals,
* `P` is an ideal lying over `p`
We will try to relax the above hypotheses as much as possible.
## Notation
In this file, `e` stands for the ramification index and `f` for the inertia degree of `P` over `p`,
leaving `p` and `P` implicit.
-/
namespace Ideal
universe u v
variable {R : Type u} [CommRing R]
variable {S : Type v} [CommRing S] (f : R →+* S)
variable (p : Ideal R) (P : Ideal S)
open FiniteDimensional
open UniqueFactorizationMonoid
section DecEq
open scoped Classical
/-- The ramification index of `P` over `p` is the largest exponent `n` such that
`p` is contained in `P^n`.
In particular, if `p` is not contained in `P^n`, then the ramification index is 0.
If there is no largest such `n` (e.g. because `p = ⊥`), then `ramificationIdx` is
defined to be 0.
-/
noncomputable def ramificationIdx : ℕ := sSup {n | map f p ≤ P ^ n}
#align ideal.ramification_idx Ideal.ramificationIdx
variable {f p P}
theorem ramificationIdx_eq_find (h : ∃ n, ∀ k, map f p ≤ P ^ k → k ≤ n) :
ramificationIdx f p P = Nat.find h :=
Nat.sSup_def h
#align ideal.ramification_idx_eq_find Ideal.ramificationIdx_eq_find
theorem ramificationIdx_eq_zero (h : ∀ n : ℕ, ∃ k, map f p ≤ P ^ k ∧ n < k) :
ramificationIdx f p P = 0 :=
dif_neg (by push_neg; exact h)
#align ideal.ramification_idx_eq_zero Ideal.ramificationIdx_eq_zero
theorem ramificationIdx_spec {n : ℕ} (hle : map f p ≤ P ^ n) (hgt : ¬map f p ≤ P ^ (n + 1)) :
ramificationIdx f p P = n := by
let Q : ℕ → Prop := fun m => ∀ k : ℕ, map f p ≤ P ^ k → k ≤ m
have : Q n := by
intro k hk
refine le_of_not_lt fun hnk => ?_
exact hgt (hk.trans (Ideal.pow_le_pow_right hnk))
rw [ramificationIdx_eq_find ⟨n, this⟩]
refine le_antisymm (Nat.find_min' _ this) (le_of_not_gt fun h : Nat.find _ < n => ?_)
obtain this' := Nat.find_spec ⟨n, this⟩
exact h.not_le (this' _ hle)
#align ideal.ramification_idx_spec Ideal.ramificationIdx_spec
theorem ramificationIdx_lt {n : ℕ} (hgt : ¬map f p ≤ P ^ n) : ramificationIdx f p P < n := by
cases' n with n n
· simp at hgt
· rw [Nat.lt_succ_iff]
have : ∀ k, map f p ≤ P ^ k → k ≤ n := by
refine fun k hk => le_of_not_lt fun hnk => ?_
exact hgt (hk.trans (Ideal.pow_le_pow_right hnk))
rw [ramificationIdx_eq_find ⟨n, this⟩]
exact Nat.find_min' ⟨n, this⟩ this
#align ideal.ramification_idx_lt Ideal.ramificationIdx_lt
@[simp]
theorem ramificationIdx_bot : ramificationIdx f ⊥ P = 0 :=
dif_neg <| not_exists.mpr fun n hn => n.lt_succ_self.not_le (hn _ (by simp))
#align ideal.ramification_idx_bot Ideal.ramificationIdx_bot
@[simp]
theorem ramificationIdx_of_not_le (h : ¬map f p ≤ P) : ramificationIdx f p P = 0 :=
ramificationIdx_spec (by simp) (by simpa using h)
#align ideal.ramification_idx_of_not_le Ideal.ramificationIdx_of_not_le
theorem ramificationIdx_ne_zero {e : ℕ} (he : e ≠ 0) (hle : map f p ≤ P ^ e)
(hnle : ¬map f p ≤ P ^ (e + 1)) : ramificationIdx f p P ≠ 0 := by
rwa [ramificationIdx_spec hle hnle]
#align ideal.ramification_idx_ne_zero Ideal.ramificationIdx_ne_zero
theorem le_pow_of_le_ramificationIdx {n : ℕ} (hn : n ≤ ramificationIdx f p P) :
map f p ≤ P ^ n := by
contrapose! hn
exact ramificationIdx_lt hn
#align ideal.le_pow_of_le_ramification_idx Ideal.le_pow_of_le_ramificationIdx
theorem le_pow_ramificationIdx : map f p ≤ P ^ ramificationIdx f p P :=
le_pow_of_le_ramificationIdx (le_refl _)
#align ideal.le_pow_ramification_idx Ideal.le_pow_ramificationIdx
theorem le_comap_pow_ramificationIdx : p ≤ comap f (P ^ ramificationIdx f p P) :=
map_le_iff_le_comap.mp le_pow_ramificationIdx
#align ideal.le_comap_pow_ramification_idx Ideal.le_comap_pow_ramificationIdx
theorem le_comap_of_ramificationIdx_ne_zero (h : ramificationIdx f p P ≠ 0) : p ≤ comap f P :=
Ideal.map_le_iff_le_comap.mp <| le_pow_ramificationIdx.trans <| Ideal.pow_le_self <| h
#align ideal.le_comap_of_ramification_idx_ne_zero Ideal.le_comap_of_ramificationIdx_ne_zero
namespace IsDedekindDomain
variable [IsDedekindDomain S]
theorem ramificationIdx_eq_normalizedFactors_count (hp0 : map f p ≠ ⊥) (hP : P.IsPrime)
(hP0 : P ≠ ⊥) : ramificationIdx f p P = (normalizedFactors (map f p)).count P := by
have hPirr := (Ideal.prime_of_isPrime hP0 hP).irreducible
refine ramificationIdx_spec (Ideal.le_of_dvd ?_) (mt Ideal.dvd_iff_le.mpr ?_) <;>
rw [dvd_iff_normalizedFactors_le_normalizedFactors (pow_ne_zero _ hP0) hp0,
normalizedFactors_pow, normalizedFactors_irreducible hPirr, normalize_eq,
Multiset.nsmul_singleton, ← Multiset.le_count_iff_replicate_le]
exact (Nat.lt_succ_self _).not_le
#align ideal.is_dedekind_domain.ramification_idx_eq_normalized_factors_count Ideal.IsDedekindDomain.ramificationIdx_eq_normalizedFactors_count
theorem ramificationIdx_eq_factors_count (hp0 : map f p ≠ ⊥) (hP : P.IsPrime) (hP0 : P ≠ ⊥) :
ramificationIdx f p P = (factors (map f p)).count P := by
rw [IsDedekindDomain.ramificationIdx_eq_normalizedFactors_count hp0 hP hP0,
factors_eq_normalizedFactors]
#align ideal.is_dedekind_domain.ramification_idx_eq_factors_count Ideal.IsDedekindDomain.ramificationIdx_eq_factors_count
theorem ramificationIdx_ne_zero (hp0 : map f p ≠ ⊥) (hP : P.IsPrime) (le : map f p ≤ P) :
ramificationIdx f p P ≠ 0 := by
have hP0 : P ≠ ⊥ := by
rintro rfl
have := le_bot_iff.mp le
contradiction
have hPirr := (Ideal.prime_of_isPrime hP0 hP).irreducible
rw [IsDedekindDomain.ramificationIdx_eq_normalizedFactors_count hp0 hP hP0]
obtain ⟨P', hP', P'_eq⟩ :=
exists_mem_normalizedFactors_of_dvd hp0 hPirr (Ideal.dvd_iff_le.mpr le)
rwa [Multiset.count_ne_zero, associated_iff_eq.mp P'_eq]
#align ideal.is_dedekind_domain.ramification_idx_ne_zero Ideal.IsDedekindDomain.ramificationIdx_ne_zero
end IsDedekindDomain
variable (f p P)
attribute [local instance] Ideal.Quotient.field
/-- The inertia degree of `P : Ideal S` lying over `p : Ideal R` is the degree of the
extension `(S / P) : (R / p)`.
We do not assume `P` lies over `p` in the definition; we return `0` instead.
See `inertiaDeg_algebraMap` for the common case where `f = algebraMap R S`
and there is an algebra structure `R / p → S / P`.
-/
noncomputable def inertiaDeg [p.IsMaximal] : ℕ :=
if hPp : comap f P = p then
@finrank (R ⧸ p) (S ⧸ P) _ _ <|
@Algebra.toModule _ _ _ _ <|
RingHom.toAlgebra <|
Ideal.Quotient.lift p ((Ideal.Quotient.mk P).comp f) fun _ ha =>
Quotient.eq_zero_iff_mem.mpr <| mem_comap.mp <| hPp.symm ▸ ha
else 0
#align ideal.inertia_deg Ideal.inertiaDeg
-- Useful for the `nontriviality` tactic using `comap_eq_of_scalar_tower_quotient`.
@[simp]
theorem inertiaDeg_of_subsingleton [hp : p.IsMaximal] [hQ : Subsingleton (S ⧸ P)] :
inertiaDeg f p P = 0 := by
have := Ideal.Quotient.subsingleton_iff.mp hQ
subst this
exact dif_neg fun h => hp.ne_top <| h.symm.trans comap_top
#align ideal.inertia_deg_of_subsingleton Ideal.inertiaDeg_of_subsingleton
@[simp]
theorem inertiaDeg_algebraMap [Algebra R S] [Algebra (R ⧸ p) (S ⧸ P)]
[IsScalarTower R (R ⧸ p) (S ⧸ P)] [hp : p.IsMaximal] :
inertiaDeg (algebraMap R S) p P = finrank (R ⧸ p) (S ⧸ P) := by
nontriviality S ⧸ P using inertiaDeg_of_subsingleton, finrank_zero_of_subsingleton
have := comap_eq_of_scalar_tower_quotient (algebraMap (R ⧸ p) (S ⧸ P)).injective
rw [inertiaDeg, dif_pos this]
congr
refine Algebra.algebra_ext _ _ fun x' => Quotient.inductionOn' x' fun x => ?_
change Ideal.Quotient.lift p _ _ (Ideal.Quotient.mk p x) = algebraMap _ _ (Ideal.Quotient.mk p x)
rw [Ideal.Quotient.lift_mk, ← Ideal.Quotient.algebraMap_eq P, ← IsScalarTower.algebraMap_eq,
← Ideal.Quotient.algebraMap_eq, ← IsScalarTower.algebraMap_apply]
#align ideal.inertia_deg_algebra_map Ideal.inertiaDeg_algebraMap
end DecEq
section FinrankQuotientMap
open scoped nonZeroDivisors
variable [Algebra R S]
variable {K : Type*} [Field K] [Algebra R K] [hRK : IsFractionRing R K]
variable {L : Type*} [Field L] [Algebra S L] [IsFractionRing S L]
variable {V V' V'' : Type*}
variable [AddCommGroup V] [Module R V] [Module K V] [IsScalarTower R K V]
variable [AddCommGroup V'] [Module R V'] [Module S V'] [IsScalarTower R S V']
variable [AddCommGroup V''] [Module R V'']
variable (K)
/-- Let `V` be a vector space over `K = Frac(R)`, `S / R` a ring extension
and `V'` a module over `S`. If `b`, in the intersection `V''` of `V` and `V'`,
is linear independent over `S` in `V'`, then it is linear independent over `R` in `V`.
The statement we prove is actually slightly more general:
* it suffices that the inclusion `algebraMap R S : R → S` is nontrivial
* the function `f' : V'' → V'` doesn't need to be injective
-/
theorem FinrankQuotientMap.linearIndependent_of_nontrivial [IsDedekindDomain R]
(hRS : RingHom.ker (algebraMap R S) ≠ ⊤) (f : V'' →ₗ[R] V) (hf : Function.Injective f)
(f' : V'' →ₗ[R] V') {ι : Type*} {b : ι → V''} (hb' : LinearIndependent S (f' ∘ b)) :
LinearIndependent K (f ∘ b) := by
contrapose! hb' with hb
-- Informally, if we have a nontrivial linear dependence with coefficients `g` in `K`,
-- then we can find a linear dependence with coefficients `I.Quotient.mk g'` in `R/I`,
-- where `I = ker (algebraMap R S)`.
-- We make use of the same principle but stay in `R` everywhere.
simp only [linearIndependent_iff', not_forall] at hb ⊢
obtain ⟨s, g, eq, j', hj's, hj'g⟩ := hb
use s
obtain ⟨a, hag, j, hjs, hgI⟩ := Ideal.exist_integer_multiples_not_mem hRS s g hj's hj'g
choose g'' hg'' using hag
letI := Classical.propDecidable
let g' i := if h : i ∈ s then g'' i h else 0
have hg' : ∀ i ∈ s, algebraMap _ _ (g' i) = a * g i := by
intro i hi; exact (congr_arg _ (dif_pos hi)).trans (hg'' i hi)
-- Because `R/I` is nontrivial, we can lift `g` to a nontrivial linear dependence in `S`.
have hgI : algebraMap R S (g' j) ≠ 0 := by
simp only [FractionalIdeal.mem_coeIdeal, not_exists, not_and'] at hgI
exact hgI _ (hg' j hjs)
refine ⟨fun i => algebraMap R S (g' i), ?_, j, hjs, hgI⟩
have eq : f (∑ i ∈ s, g' i • b i) = 0 := by
rw [map_sum, ← smul_zero a, ← eq, Finset.smul_sum]
refine Finset.sum_congr rfl ?_
intro i hi
rw [LinearMap.map_smul, ← IsScalarTower.algebraMap_smul K, hg' i hi, ← smul_assoc,
smul_eq_mul, Function.comp_apply]
simp only [IsScalarTower.algebraMap_smul, ← map_smul, ← map_sum,
(f.map_eq_zero_iff hf).mp eq, LinearMap.map_zero, (· ∘ ·)]
#align ideal.finrank_quotient_map.linear_independent_of_nontrivial Ideal.FinrankQuotientMap.linearIndependent_of_nontrivial
open scoped Matrix
variable {K}
/-- If `b` mod `p` spans `S/p` as `R/p`-space, then `b` itself spans `Frac(S)` as `K`-space.
Here,
* `p` is an ideal of `R` such that `R / p` is nontrivial
* `K` is a field that has an embedding of `R` (in particular we can take `K = Frac(R)`)
* `L` is a field extension of `K`
* `S` is the integral closure of `R` in `L`
More precisely, we avoid quotients in this statement and instead require that `b ∪ pS` spans `S`.
-/
theorem FinrankQuotientMap.span_eq_top [IsDomain R] [IsDomain S] [Algebra K L] [IsNoetherian R S]
[Algebra R L] [IsScalarTower R S L] [IsScalarTower R K L] [IsIntegralClosure S R L]
[NoZeroSMulDivisors R K] (hp : p ≠ ⊤) (b : Set S)
(hb' : Submodule.span R b ⊔ (p.map (algebraMap R S)).restrictScalars R = ⊤) :
Submodule.span K (algebraMap S L '' b) = ⊤ := by
have hRL : Function.Injective (algebraMap R L) := by
rw [IsScalarTower.algebraMap_eq R K L]
exact (algebraMap K L).injective.comp (NoZeroSMulDivisors.algebraMap_injective R K)
-- Let `M` be the `R`-module spanned by the proposed basis elements.
let M : Submodule R S := Submodule.span R b
-- Then `S / M` is generated by some finite set of `n` vectors `a`.
letI h : Module.Finite R (S ⧸ M) :=
Module.Finite.of_surjective (Submodule.mkQ _) (Submodule.Quotient.mk_surjective _)
obtain ⟨n, a, ha⟩ := @Module.Finite.exists_fin _ _ _ _ _ h
-- Because the image of `p` in `S / M` is `⊤`,
have smul_top_eq : p • (⊤ : Submodule R (S ⧸ M)) = ⊤ := by
calc
p • ⊤ = Submodule.map M.mkQ (p • ⊤) := by
rw [Submodule.map_smul'', Submodule.map_top, M.range_mkQ]
_ = ⊤ := by rw [Ideal.smul_top_eq_map, (Submodule.map_mkQ_eq_top M _).mpr hb']
-- we can write the elements of `a` as `p`-linear combinations of other elements of `a`.
have exists_sum : ∀ x : S ⧸ M, ∃ a' : Fin n → R, (∀ i, a' i ∈ p) ∧ ∑ i, a' i • a i = x := by
intro x
obtain ⟨a'', ha'', hx⟩ := (Submodule.mem_ideal_smul_span_iff_exists_sum p a x).1
(by { rw [ha, smul_top_eq]; exact Submodule.mem_top } :
x ∈ p • Submodule.span R (Set.range a))
· refine ⟨fun i => a'' i, fun i => ha'' _, ?_⟩
rw [← hx, Finsupp.sum_fintype]
exact fun _ => zero_smul _ _
choose A' hA'p hA' using fun i => exists_sum (a i)
-- This gives us a(n invertible) matrix `A` such that `det A ∈ (M = span R b)`,
let A : Matrix (Fin n) (Fin n) R := Matrix.of A' - 1
let B := A.adjugate
have A_smul : ∀ i, ∑ j, A i j • a j = 0 := by
intros
simp [A, Matrix.sub_apply, Matrix.of_apply, ne_eq, Matrix.one_apply, sub_smul,
Finset.sum_sub_distrib, hA', sub_self]
-- since `span S {det A} / M = 0`.
have d_smul : ∀ i, A.det • a i = 0 := by
intro i
calc
A.det • a i = ∑ j, (B * A) i j • a j := ?_
_ = ∑ k, B i k • ∑ j, A k j • a j := ?_
_ = 0 := Finset.sum_eq_zero fun k _ => ?_
· simp only [B, Matrix.adjugate_mul, Matrix.smul_apply, Matrix.one_apply, smul_eq_mul, ite_true,
mul_ite, mul_one, mul_zero, ite_smul, zero_smul, Finset.sum_ite_eq, Finset.mem_univ]
· simp only [Matrix.mul_apply, Finset.smul_sum, Finset.sum_smul, smul_smul]
rw [Finset.sum_comm]
· rw [A_smul, smul_zero]
-- In the rings of integers we have the desired inclusion.
have span_d : (Submodule.span S ({algebraMap R S A.det} : Set S)).restrictScalars R ≤ M := by
intro x hx
rw [Submodule.restrictScalars_mem] at hx
obtain ⟨x', rfl⟩ := Submodule.mem_span_singleton.mp hx
rw [smul_eq_mul, mul_comm, ← Algebra.smul_def] at hx ⊢
rw [← Submodule.Quotient.mk_eq_zero, Submodule.Quotient.mk_smul]
obtain ⟨a', _, quot_x_eq⟩ := exists_sum (Submodule.Quotient.mk x')
rw [← quot_x_eq, Finset.smul_sum]
conv =>
lhs; congr; next => skip
intro x; rw [smul_comm A.det, d_smul, smul_zero]
exact Finset.sum_const_zero
refine top_le_iff.mp
(calc
⊤ = (Ideal.span {algebraMap R L A.det}).restrictScalars K := ?_
_ ≤ Submodule.span K (algebraMap S L '' b) := ?_)
-- Because `det A ≠ 0`, we have `span L {det A} = ⊤`.
· rw [eq_comm, Submodule.restrictScalars_eq_top_iff, Ideal.span_singleton_eq_top]
refine IsUnit.mk0 _ ((map_ne_zero_iff (algebraMap R L) hRL).mpr ?_)
refine ne_zero_of_map (f := Ideal.Quotient.mk p) ?_
haveI := Ideal.Quotient.nontrivial hp
calc
Ideal.Quotient.mk p A.det = Matrix.det ((Ideal.Quotient.mk p).mapMatrix A) := by
rw [RingHom.map_det]
_ = Matrix.det ((Ideal.Quotient.mk p).mapMatrix (Matrix.of A' - 1)) := rfl
_ = Matrix.det fun i j =>
(Ideal.Quotient.mk p) (A' i j) - (1 : Matrix (Fin n) (Fin n) (R ⧸ p)) i j := ?_
_ = Matrix.det (-1 : Matrix (Fin n) (Fin n) (R ⧸ p)) := ?_
_ = (-1 : R ⧸ p) ^ n := by rw [Matrix.det_neg, Fintype.card_fin, Matrix.det_one, mul_one]
_ ≠ 0 := IsUnit.ne_zero (isUnit_one.neg.pow _)
· refine congr_arg Matrix.det (Matrix.ext fun i j => ?_)
rw [map_sub, RingHom.mapMatrix_apply, map_one]
rfl
· refine congr_arg Matrix.det (Matrix.ext fun i j => ?_)
rw [Ideal.Quotient.eq_zero_iff_mem.mpr (hA'p i j), zero_sub]
rfl
-- And we conclude `L = span L {det A} ≤ span K b`, so `span K b` spans everything.
· intro x hx
rw [Submodule.restrictScalars_mem, IsScalarTower.algebraMap_apply R S L] at hx
have : Algebra.IsAlgebraic R L := by
have : NoZeroSMulDivisors R L := NoZeroSMulDivisors.of_algebraMap_injective hRL
rw [← IsFractionRing.isAlgebraic_iff' R S]
infer_instance
refine IsFractionRing.ideal_span_singleton_map_subset R hRL span_d hx
#align ideal.finrank_quotient_map.span_eq_top Ideal.FinrankQuotientMap.span_eq_top
variable (K L)
/-- If `p` is a maximal ideal of `R`, and `S` is the integral closure of `R` in `L`,
then the dimension `[S/pS : R/p]` is equal to `[Frac(S) : Frac(R)]`. -/
theorem finrank_quotient_map [IsDomain S] [IsDedekindDomain R] [Algebra K L]
[Algebra R L] [IsScalarTower R K L] [IsScalarTower R S L] [IsIntegralClosure S R L]
[hp : p.IsMaximal] [IsNoetherian R S] :
finrank (R ⧸ p) (S ⧸ map (algebraMap R S) p) = finrank K L := by
-- Choose an arbitrary basis `b` for `[S/pS : R/p]`.
-- We'll use the previous results to turn it into a basis on `[Frac(S) : Frac(R)]`.
letI : Field (R ⧸ p) := Ideal.Quotient.field _
let ι := Module.Free.ChooseBasisIndex (R ⧸ p) (S ⧸ map (algebraMap R S) p)
let b : Basis ι (R ⧸ p) (S ⧸ map (algebraMap R S) p) := Module.Free.chooseBasis _ _
-- Namely, choose a representative `b' i : S` for each `b i : S / pS`.
let b' : ι → S := fun i => (Ideal.Quotient.mk_surjective (b i)).choose
have b_eq_b' : ⇑b = (Submodule.mkQ (map (algebraMap R S) p)).restrictScalars R ∘ b' :=
funext fun i => (Ideal.Quotient.mk_surjective (b i)).choose_spec.symm
-- We claim `b'` is a basis for `Frac(S)` over `Frac(R)` because it is linear independent
-- and spans the whole of `Frac(S)`.
let b'' : ι → L := algebraMap S L ∘ b'
have b''_li : LinearIndependent K b'' := ?_
· have b''_sp : Submodule.span K (Set.range b'') = ⊤ := ?_
-- Since the two bases have the same index set, the spaces have the same dimension.
· let c : Basis ι K L := Basis.mk b''_li b''_sp.ge
rw [finrank_eq_card_basis b, finrank_eq_card_basis c]
-- It remains to show that the basis is indeed linear independent and spans the whole space.
· rw [Set.range_comp]
refine FinrankQuotientMap.span_eq_top p hp.ne_top _ (top_le_iff.mp ?_)
-- The nicest way to show `S ≤ span b' ⊔ pS` is by reducing both sides modulo pS.
-- However, this would imply distinguishing between `pS` as `S`-ideal,
-- and `pS` as `R`-submodule, since they have different (non-defeq) quotients.
-- Instead we'll lift `x mod pS ∈ span b` to `y ∈ span b'` for some `y - x ∈ pS`.
intro x _
have mem_span_b : ((Submodule.mkQ (map (algebraMap R S) p)) x : S ⧸ map (algebraMap R S) p) ∈
Submodule.span (R ⧸ p) (Set.range b) := b.mem_span _
rw [← @Submodule.restrictScalars_mem R,
Submodule.restrictScalars_span R (R ⧸ p) Ideal.Quotient.mk_surjective, b_eq_b',
Set.range_comp, ← Submodule.map_span] at mem_span_b
obtain ⟨y, y_mem, y_eq⟩ := Submodule.mem_map.mp mem_span_b
suffices y + -(y - x) ∈ _ by simpa
rw [LinearMap.restrictScalars_apply, Submodule.mkQ_apply, Submodule.mkQ_apply,
Submodule.Quotient.eq] at y_eq
exact add_mem (Submodule.mem_sup_left y_mem) (neg_mem <| Submodule.mem_sup_right y_eq)
· have := b.linearIndependent; rw [b_eq_b'] at this
convert FinrankQuotientMap.linearIndependent_of_nontrivial K _
((Algebra.linearMap S L).restrictScalars R) _ ((Submodule.mkQ _).restrictScalars R) this
· rw [Quotient.algebraMap_eq, Ideal.mk_ker]
exact hp.ne_top
· exact IsFractionRing.injective S L
#align ideal.finrank_quotient_map Ideal.finrank_quotient_map
end FinrankQuotientMap
section FactLeComap
local notation "e" => ramificationIdx f p P
/-- `R / p` has a canonical map to `S / (P ^ e)`, where `e` is the ramification index
of `P` over `p`. -/
noncomputable instance Quotient.algebraQuotientPowRamificationIdx : Algebra (R ⧸ p) (S ⧸ P ^ e) :=
Quotient.algebraQuotientOfLEComap (Ideal.map_le_iff_le_comap.mp le_pow_ramificationIdx)
#align ideal.quotient.algebra_quotient_pow_ramification_idx Ideal.Quotient.algebraQuotientPowRamificationIdx
#adaptation_note /-- 2024-04-23
The right hand side here used to be `Ideal.Quotient.mk _ (f x)` which was somewhat slow,
but this is now even slower without `set_option backward.isDefEq.lazyProjDelta false in`
Instead we've replaced it with `Ideal.Quotient.mk (P ^ e) (f x)` (compare #12412) -/
@[simp]
theorem Quotient.algebraMap_quotient_pow_ramificationIdx (x : R) :
algebraMap (R ⧸ p) (S ⧸ P ^ e) (Ideal.Quotient.mk p x) = Ideal.Quotient.mk (P ^ e) (f x) := rfl
#align ideal.quotient.algebra_map_quotient_pow_ramification_idx Ideal.Quotient.algebraMap_quotient_pow_ramificationIdx
variable [hfp : NeZero (ramificationIdx f p P)]
/-- If `P` lies over `p`, then `R / p` has a canonical map to `S / P`.
This can't be an instance since the map `f : R → S` is generally not inferrable.
-/
def Quotient.algebraQuotientOfRamificationIdxNeZero : Algebra (R ⧸ p) (S ⧸ P) :=
Quotient.algebraQuotientOfLEComap (le_comap_of_ramificationIdx_ne_zero hfp.out)
#align ideal.quotient.algebra_quotient_of_ramification_idx_ne_zero Ideal.Quotient.algebraQuotientOfRamificationIdxNeZero
set_option synthInstance.checkSynthOrder false -- Porting note: this is okay by the remark below
-- In this file, the value for `f` can be inferred.
attribute [local instance] Ideal.Quotient.algebraQuotientOfRamificationIdxNeZero
#adaptation_note /-- 2024-04-28
The RHS used to be `Ideal.Quotient.mk _ (f x)`, which was slow,
but this is now even slower without `set_option backward.isDefEq.lazyWhnfCore false in`
(compare https://github.com/leanprover-community/mathlib4/pull/12412) -/
@[simp]
theorem Quotient.algebraMap_quotient_of_ramificationIdx_neZero (x : R) :
algebraMap (R ⧸ p) (S ⧸ P) (Ideal.Quotient.mk p x) = Ideal.Quotient.mk P (f x) := rfl
#align ideal.quotient.algebra_map_quotient_of_ramification_idx_ne_zero Ideal.Quotient.algebraMap_quotient_of_ramificationIdx_neZero
/-- The inclusion `(P^(i + 1) / P^e) ⊂ (P^i / P^e)`. -/
@[simps]
def powQuotSuccInclusion (i : ℕ) :
Ideal.map (Ideal.Quotient.mk (P ^ e)) (P ^ (i + 1)) →ₗ[R ⧸ p]
Ideal.map (Ideal.Quotient.mk (P ^ e)) (P ^ i) where
toFun x := ⟨x, Ideal.map_mono (Ideal.pow_le_pow_right i.le_succ) x.2⟩
map_add' _ _ := rfl
map_smul' _ _ := rfl
#align ideal.pow_quot_succ_inclusion Ideal.powQuotSuccInclusion
theorem powQuotSuccInclusion_injective (i : ℕ) :
Function.Injective (powQuotSuccInclusion f p P i) := by
rw [← LinearMap.ker_eq_bot, LinearMap.ker_eq_bot']
rintro ⟨x, hx⟩ hx0
rw [Subtype.ext_iff] at hx0 ⊢
rwa [powQuotSuccInclusion_apply_coe] at hx0
#align ideal.pow_quot_succ_inclusion_injective Ideal.powQuotSuccInclusion_injective
/-- `S ⧸ P` embeds into the quotient by `P^(i+1) ⧸ P^e` as a subspace of `P^i ⧸ P^e`.
See `quotientToQuotientRangePowQuotSucc` for this as a linear map,
and `quotientRangePowQuotSuccInclusionEquiv` for this as a linear equivalence.
-/
noncomputable def quotientToQuotientRangePowQuotSuccAux {i : ℕ} {a : S} (a_mem : a ∈ P ^ i) :
S ⧸ P →
(P ^ i).map (Ideal.Quotient.mk (P ^ e)) ⧸ LinearMap.range (powQuotSuccInclusion f p P i) :=
Quotient.map' (fun x : S => ⟨_, Ideal.mem_map_of_mem _ (Ideal.mul_mem_right x _ a_mem)⟩)
fun x y h => by
rw [Submodule.quotientRel_r_def] at h ⊢
simp only [_root_.map_mul, LinearMap.mem_range]
refine ⟨⟨_, Ideal.mem_map_of_mem _ (Ideal.mul_mem_mul a_mem h)⟩, ?_⟩
ext
rw [powQuotSuccInclusion_apply_coe, Subtype.coe_mk, Submodule.coe_sub, Subtype.coe_mk,
Subtype.coe_mk, _root_.map_mul, map_sub, mul_sub]
#align ideal.quotient_to_quotient_range_pow_quot_succ_aux Ideal.quotientToQuotientRangePowQuotSuccAux
| Mathlib/NumberTheory/RamificationInertia.lean | 515 | 518 | theorem quotientToQuotientRangePowQuotSuccAux_mk {i : ℕ} {a : S} (a_mem : a ∈ P ^ i) (x : S) :
quotientToQuotientRangePowQuotSuccAux f p P a_mem (Submodule.Quotient.mk x) =
Submodule.Quotient.mk ⟨_, Ideal.mem_map_of_mem _ (Ideal.mul_mem_right x _ a_mem)⟩ := by |
apply Quotient.map'_mk''
|
/-
Copyright (c) 2021 Yaël Dillies. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yaël Dillies
-/
import Mathlib.Data.Nat.Choose.Basic
import Mathlib.Data.Nat.Factorial.Cast
#align_import data.nat.choose.cast from "leanprover-community/mathlib"@"bb168510ef455e9280a152e7f31673cabd3d7496"
/-!
# Cast of binomial coefficients
This file allows calculating the binomial coefficient `a.choose b` as an element of a division ring
of characteristic `0`.
-/
open Nat
variable (K : Type*) [DivisionRing K] [CharZero K]
namespace Nat
theorem cast_choose {a b : ℕ} (h : a ≤ b) : (b.choose a : K) = b ! / (a ! * (b - a)!) := by
have : ∀ {n : ℕ}, (n ! : K) ≠ 0 := Nat.cast_ne_zero.2 (factorial_ne_zero _)
rw [eq_div_iff_mul_eq (mul_ne_zero this this)]
rw_mod_cast [← mul_assoc, choose_mul_factorial_mul_factorial h]
#align nat.cast_choose Nat.cast_choose
| Mathlib/Data/Nat/Choose/Cast.lean | 31 | 32 | theorem cast_add_choose {a b : ℕ} : ((a + b).choose a : K) = (a + b)! / (a ! * b !) := by |
rw [cast_choose K (_root_.le_add_right le_rfl), add_tsub_cancel_left]
|
/-
Copyright (c) 2020 Floris van Doorn. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Floris van Doorn
-/
import Mathlib.MeasureTheory.Constructions.Prod.Basic
import Mathlib.MeasureTheory.Group.Measure
import Mathlib.Topology.Constructions
#align_import measure_theory.constructions.pi from "leanprover-community/mathlib"@"fd5edc43dc4f10b85abfe544b88f82cf13c5f844"
/-!
# Product measures
In this file we define and prove properties about finite products of measures
(and at some point, countable products of measures).
## Main definition
* `MeasureTheory.Measure.pi`: The product of finitely many σ-finite measures.
Given `μ : (i : ι) → Measure (α i)` for `[Fintype ι]` it has type `Measure ((i : ι) → α i)`.
To apply Fubini's theorem or Tonelli's theorem along some subset, we recommend using the marginal
construction `MeasureTheory.lmarginal` and (todo) `MeasureTheory.marginal`. This allows you to
apply the theorems without any bookkeeping with measurable equivalences.
## Implementation Notes
We define `MeasureTheory.OuterMeasure.pi`, the product of finitely many outer measures, as the
maximal outer measure `n` with the property that `n (pi univ s) ≤ ∏ i, m i (s i)`,
where `pi univ s` is the product of the sets `{s i | i : ι}`.
We then show that this induces a product of measures, called `MeasureTheory.Measure.pi`.
For a collection of σ-finite measures `μ` and a collection of measurable sets `s` we show that
`Measure.pi μ (pi univ s) = ∏ i, m i (s i)`. To do this, we follow the following steps:
* We know that there is some ordering on `ι`, given by an element of `[Countable ι]`.
* Using this, we have an equivalence `MeasurableEquiv.piMeasurableEquivTProd` between
`∀ ι, α i` and an iterated product of `α i`, called `List.tprod α l` for some list `l`.
* On this iterated product we can easily define a product measure `MeasureTheory.Measure.tprod`
by iterating `MeasureTheory.Measure.prod`
* Using the previous two steps we construct `MeasureTheory.Measure.pi'` on `(i : ι) → α i` for
countable `ι`.
* We know that `MeasureTheory.Measure.pi'` sends products of sets to products of measures, and
since `MeasureTheory.Measure.pi` is the maximal such measure (or at least, it comes from an outer
measure which is the maximal such outer measure), we get the same rule for
`MeasureTheory.Measure.pi`.
## Tags
finitary product measure
-/
noncomputable section
open Function Set MeasureTheory.OuterMeasure Filter MeasurableSpace Encodable
open scoped Classical Topology ENNReal
universe u v
variable {ι ι' : Type*} {α : ι → Type*}
/-! We start with some measurability properties -/
/-- Boxes formed by π-systems form a π-system. -/
theorem IsPiSystem.pi {C : ∀ i, Set (Set (α i))} (hC : ∀ i, IsPiSystem (C i)) :
IsPiSystem (pi univ '' pi univ C) := by
rintro _ ⟨s₁, hs₁, rfl⟩ _ ⟨s₂, hs₂, rfl⟩ hst
rw [← pi_inter_distrib] at hst ⊢; rw [univ_pi_nonempty_iff] at hst
exact mem_image_of_mem _ fun i _ => hC i _ (hs₁ i (mem_univ i)) _ (hs₂ i (mem_univ i)) (hst i)
#align is_pi_system.pi IsPiSystem.pi
/-- Boxes form a π-system. -/
theorem isPiSystem_pi [∀ i, MeasurableSpace (α i)] :
IsPiSystem (pi univ '' pi univ fun i => { s : Set (α i) | MeasurableSet s }) :=
IsPiSystem.pi fun _ => isPiSystem_measurableSet
#align is_pi_system_pi isPiSystem_pi
section Finite
variable [Finite ι] [Finite ι']
/-- Boxes of countably spanning sets are countably spanning. -/
theorem IsCountablySpanning.pi {C : ∀ i, Set (Set (α i))} (hC : ∀ i, IsCountablySpanning (C i)) :
IsCountablySpanning (pi univ '' pi univ C) := by
choose s h1s h2s using hC
cases nonempty_encodable (ι → ℕ)
let e : ℕ → ι → ℕ := fun n => (@decode (ι → ℕ) _ n).iget
refine ⟨fun n => Set.pi univ fun i => s i (e n i), fun n =>
mem_image_of_mem _ fun i _ => h1s i _, ?_⟩
simp_rw [(surjective_decode_iget (ι → ℕ)).iUnion_comp fun x => Set.pi univ fun i => s i (x i),
iUnion_univ_pi s, h2s, pi_univ]
#align is_countably_spanning.pi IsCountablySpanning.pi
/-- The product of generated σ-algebras is the one generated by boxes, if both generating sets
are countably spanning. -/
theorem generateFrom_pi_eq {C : ∀ i, Set (Set (α i))} (hC : ∀ i, IsCountablySpanning (C i)) :
(@MeasurableSpace.pi _ _ fun i => generateFrom (C i)) =
generateFrom (pi univ '' pi univ C) := by
cases nonempty_encodable ι
apply le_antisymm
· refine iSup_le ?_; intro i; rw [comap_generateFrom]
apply generateFrom_le; rintro _ ⟨s, hs, rfl⟩; dsimp
choose t h1t h2t using hC
simp_rw [eval_preimage, ← h2t]
rw [← @iUnion_const _ ℕ _ s]
have : Set.pi univ (update (fun i' : ι => iUnion (t i')) i (⋃ _ : ℕ, s)) =
Set.pi univ fun k => ⋃ j : ℕ,
@update ι (fun i' => Set (α i')) _ (fun i' => t i' j) i s k := by
ext; simp_rw [mem_univ_pi]; apply forall_congr'; intro i'
by_cases h : i' = i
· subst h; simp
· rw [← Ne] at h; simp [h]
rw [this, ← iUnion_univ_pi]
apply MeasurableSet.iUnion
intro n; apply measurableSet_generateFrom
apply mem_image_of_mem; intro j _; dsimp only
by_cases h : j = i
· subst h; rwa [update_same]
· rw [update_noteq h]; apply h1t
· apply generateFrom_le; rintro _ ⟨s, hs, rfl⟩
rw [univ_pi_eq_iInter]; apply MeasurableSet.iInter; intro i
apply @measurable_pi_apply _ _ (fun i => generateFrom (C i))
exact measurableSet_generateFrom (hs i (mem_univ i))
#align generate_from_pi_eq generateFrom_pi_eq
/-- If `C` and `D` generate the σ-algebras on `α` resp. `β`, then rectangles formed by `C` and `D`
generate the σ-algebra on `α × β`. -/
theorem generateFrom_eq_pi [h : ∀ i, MeasurableSpace (α i)] {C : ∀ i, Set (Set (α i))}
(hC : ∀ i, generateFrom (C i) = h i) (h2C : ∀ i, IsCountablySpanning (C i)) :
generateFrom (pi univ '' pi univ C) = MeasurableSpace.pi := by
simp only [← funext hC, generateFrom_pi_eq h2C]
#align generate_from_eq_pi generateFrom_eq_pi
/-- The product σ-algebra is generated from boxes, i.e. `s ×ˢ t` for sets `s : set α` and
`t : set β`. -/
theorem generateFrom_pi [∀ i, MeasurableSpace (α i)] :
generateFrom (pi univ '' pi univ fun i => { s : Set (α i) | MeasurableSet s }) =
MeasurableSpace.pi :=
generateFrom_eq_pi (fun _ => generateFrom_measurableSet) fun _ =>
isCountablySpanning_measurableSet
#align generate_from_pi generateFrom_pi
end Finite
namespace MeasureTheory
variable [Fintype ι] {m : ∀ i, OuterMeasure (α i)}
/-- An upper bound for the measure in a finite product space.
It is defined to by taking the image of the set under all projections, and taking the product
of the measures of these images.
For measurable boxes it is equal to the correct measure. -/
@[simp]
def piPremeasure (m : ∀ i, OuterMeasure (α i)) (s : Set (∀ i, α i)) : ℝ≥0∞ :=
∏ i, m i (eval i '' s)
#align measure_theory.pi_premeasure MeasureTheory.piPremeasure
theorem piPremeasure_pi {s : ∀ i, Set (α i)} (hs : (pi univ s).Nonempty) :
piPremeasure m (pi univ s) = ∏ i, m i (s i) := by simp [hs, piPremeasure]
#align measure_theory.pi_premeasure_pi MeasureTheory.piPremeasure_pi
theorem piPremeasure_pi' {s : ∀ i, Set (α i)} : piPremeasure m (pi univ s) = ∏ i, m i (s i) := by
cases isEmpty_or_nonempty ι
· simp [piPremeasure]
rcases (pi univ s).eq_empty_or_nonempty with h | h
· rcases univ_pi_eq_empty_iff.mp h with ⟨i, hi⟩
have : ∃ i, m i (s i) = 0 := ⟨i, by simp [hi]⟩
simpa [h, Finset.card_univ, zero_pow Fintype.card_ne_zero, @eq_comm _ (0 : ℝ≥0∞),
Finset.prod_eq_zero_iff, piPremeasure]
· simp [h, piPremeasure]
#align measure_theory.pi_premeasure_pi' MeasureTheory.piPremeasure_pi'
theorem piPremeasure_pi_mono {s t : Set (∀ i, α i)} (h : s ⊆ t) :
piPremeasure m s ≤ piPremeasure m t :=
Finset.prod_le_prod' fun _ _ => measure_mono (image_subset _ h)
#align measure_theory.pi_premeasure_pi_mono MeasureTheory.piPremeasure_pi_mono
theorem piPremeasure_pi_eval {s : Set (∀ i, α i)} :
piPremeasure m (pi univ fun i => eval i '' s) = piPremeasure m s := by
simp only [eval, piPremeasure_pi']; rfl
#align measure_theory.pi_premeasure_pi_eval MeasureTheory.piPremeasure_pi_eval
namespace OuterMeasure
/-- `OuterMeasure.pi m` is the finite product of the outer measures `{m i | i : ι}`.
It is defined to be the maximal outer measure `n` with the property that
`n (pi univ s) ≤ ∏ i, m i (s i)`, where `pi univ s` is the product of the sets
`{s i | i : ι}`. -/
protected def pi (m : ∀ i, OuterMeasure (α i)) : OuterMeasure (∀ i, α i) :=
boundedBy (piPremeasure m)
#align measure_theory.outer_measure.pi MeasureTheory.OuterMeasure.pi
theorem pi_pi_le (m : ∀ i, OuterMeasure (α i)) (s : ∀ i, Set (α i)) :
OuterMeasure.pi m (pi univ s) ≤ ∏ i, m i (s i) := by
rcases (pi univ s).eq_empty_or_nonempty with h | h
· simp [h]
exact (boundedBy_le _).trans_eq (piPremeasure_pi h)
#align measure_theory.outer_measure.pi_pi_le MeasureTheory.OuterMeasure.pi_pi_le
theorem le_pi {m : ∀ i, OuterMeasure (α i)} {n : OuterMeasure (∀ i, α i)} :
n ≤ OuterMeasure.pi m ↔
∀ s : ∀ i, Set (α i), (pi univ s).Nonempty → n (pi univ s) ≤ ∏ i, m i (s i) := by
rw [OuterMeasure.pi, le_boundedBy']; constructor
· intro h s hs; refine (h _ hs).trans_eq (piPremeasure_pi hs)
· intro h s hs; refine le_trans (n.mono <| subset_pi_eval_image univ s) (h _ ?_)
simp [univ_pi_nonempty_iff, hs]
#align measure_theory.outer_measure.le_pi MeasureTheory.OuterMeasure.le_pi
end OuterMeasure
namespace Measure
variable [∀ i, MeasurableSpace (α i)] (μ : ∀ i, Measure (α i))
section Tprod
open List
variable {δ : Type*} {π : δ → Type*} [∀ x, MeasurableSpace (π x)]
-- for some reason the equation compiler doesn't like this definition
/-- A product of measures in `tprod α l`. -/
protected def tprod (l : List δ) (μ : ∀ i, Measure (π i)) : Measure (TProd π l) := by
induction' l with i l ih
· exact dirac PUnit.unit
· have := (μ i).prod (α := π i) ih
exact this
#align measure_theory.measure.tprod MeasureTheory.Measure.tprod
@[simp]
theorem tprod_nil (μ : ∀ i, Measure (π i)) : Measure.tprod [] μ = dirac PUnit.unit :=
rfl
#align measure_theory.measure.tprod_nil MeasureTheory.Measure.tprod_nil
@[simp]
theorem tprod_cons (i : δ) (l : List δ) (μ : ∀ i, Measure (π i)) :
Measure.tprod (i :: l) μ = (μ i).prod (Measure.tprod l μ) :=
rfl
#align measure_theory.measure.tprod_cons MeasureTheory.Measure.tprod_cons
instance sigmaFinite_tprod (l : List δ) (μ : ∀ i, Measure (π i)) [∀ i, SigmaFinite (μ i)] :
SigmaFinite (Measure.tprod l μ) := by
induction l with
| nil => rw [tprod_nil]; infer_instance
| cons i l ih => rw [tprod_cons]; exact @prod.instSigmaFinite _ _ _ _ _ _ _ ih
#align measure_theory.measure.sigma_finite_tprod MeasureTheory.Measure.sigmaFinite_tprod
theorem tprod_tprod (l : List δ) (μ : ∀ i, Measure (π i)) [∀ i, SigmaFinite (μ i)]
(s : ∀ i, Set (π i)) :
Measure.tprod l μ (Set.tprod l s) = (l.map fun i => (μ i) (s i)).prod := by
induction l with
| nil => simp
| cons a l ih =>
rw [tprod_cons, Set.tprod]
erw [prod_prod] -- TODO: why `rw` fails?
rw [map_cons, prod_cons, ih]
#align measure_theory.measure.tprod_tprod MeasureTheory.Measure.tprod_tprod
end Tprod
section Encodable
open List MeasurableEquiv
variable [Encodable ι]
/-- The product measure on an encodable finite type, defined by mapping `Measure.tprod` along the
equivalence `MeasurableEquiv.piMeasurableEquivTProd`.
The definition `MeasureTheory.Measure.pi` should be used instead of this one. -/
def pi' : Measure (∀ i, α i) :=
Measure.map (TProd.elim' mem_sortedUniv) (Measure.tprod (sortedUniv ι) μ)
#align measure_theory.measure.pi' MeasureTheory.Measure.pi'
theorem pi'_pi [∀ i, SigmaFinite (μ i)] (s : ∀ i, Set (α i)) :
pi' μ (pi univ s) = ∏ i, μ i (s i) := by
rw [pi']
rw [← MeasurableEquiv.piMeasurableEquivTProd_symm_apply, MeasurableEquiv.map_apply,
MeasurableEquiv.piMeasurableEquivTProd_symm_apply, elim_preimage_pi, tprod_tprod _ μ, ←
List.prod_toFinset, sortedUniv_toFinset] <;>
exact sortedUniv_nodup ι
#align measure_theory.measure.pi'_pi MeasureTheory.Measure.pi'_pi
end Encodable
theorem pi_caratheodory :
MeasurableSpace.pi ≤ (OuterMeasure.pi fun i => (μ i).toOuterMeasure).caratheodory := by
refine iSup_le ?_
intro i s hs
rw [MeasurableSpace.comap] at hs
rcases hs with ⟨s, hs, rfl⟩
apply boundedBy_caratheodory
intro t
simp_rw [piPremeasure]
refine Finset.prod_add_prod_le' (Finset.mem_univ i) ?_ ?_ ?_
· simp [image_inter_preimage, image_diff_preimage, measure_inter_add_diff _ hs, le_refl]
· rintro j - _; gcongr; apply inter_subset_left
· rintro j - _; gcongr; apply diff_subset
#align measure_theory.measure.pi_caratheodory MeasureTheory.Measure.pi_caratheodory
/-- `Measure.pi μ` is the finite product of the measures `{μ i | i : ι}`.
It is defined to be measure corresponding to `MeasureTheory.OuterMeasure.pi`. -/
protected irreducible_def pi : Measure (∀ i, α i) :=
toMeasure (OuterMeasure.pi fun i => (μ i).toOuterMeasure) (pi_caratheodory μ)
#align measure_theory.measure.pi MeasureTheory.Measure.pi
-- Porting note: moved from below so that instances about `Measure.pi` and `MeasureSpace.pi`
-- go together
instance _root_.MeasureTheory.MeasureSpace.pi {α : ι → Type*} [∀ i, MeasureSpace (α i)] :
MeasureSpace (∀ i, α i) :=
⟨Measure.pi fun _ => volume⟩
#align measure_theory.measure_space.pi MeasureTheory.MeasureSpace.pi
theorem pi_pi_aux [∀ i, SigmaFinite (μ i)] (s : ∀ i, Set (α i)) (hs : ∀ i, MeasurableSet (s i)) :
Measure.pi μ (pi univ s) = ∏ i, μ i (s i) := by
refine le_antisymm ?_ ?_
· rw [Measure.pi, toMeasure_apply _ _ (MeasurableSet.pi countable_univ fun i _ => hs i)]
apply OuterMeasure.pi_pi_le
· haveI : Encodable ι := Fintype.toEncodable ι
simp_rw [← pi'_pi μ s, Measure.pi,
toMeasure_apply _ _ (MeasurableSet.pi countable_univ fun i _ => hs i)]
suffices (pi' μ).toOuterMeasure ≤ OuterMeasure.pi fun i => (μ i).toOuterMeasure by exact this _
clear hs s
rw [OuterMeasure.le_pi]
intro s _
exact (pi'_pi μ s).le
#align measure_theory.measure.pi_pi_aux MeasureTheory.Measure.pi_pi_aux
variable {μ}
/-- `Measure.pi μ` has finite spanning sets in rectangles of finite spanning sets. -/
def FiniteSpanningSetsIn.pi {C : ∀ i, Set (Set (α i))}
(hμ : ∀ i, (μ i).FiniteSpanningSetsIn (C i)) :
(Measure.pi μ).FiniteSpanningSetsIn (pi univ '' pi univ C) := by
haveI := fun i => (hμ i).sigmaFinite
haveI := Fintype.toEncodable ι
refine ⟨fun n => Set.pi univ fun i => (hμ i).set ((@decode (ι → ℕ) _ n).iget i),
fun n => ?_, fun n => ?_, ?_⟩ <;>
-- TODO (kmill) If this let comes before the refine, while the noncomputability checker
-- correctly sees this definition is computable, the Lean VM fails to see the binding is
-- computationally irrelevant. The `noncomputable section` doesn't help because all it does
-- is insert `noncomputable` for you when necessary.
let e : ℕ → ι → ℕ := fun n => (@decode (ι → ℕ) _ n).iget
· refine mem_image_of_mem _ fun i _ => (hμ i).set_mem _
· calc
Measure.pi μ (Set.pi univ fun i => (hμ i).set (e n i)) ≤
Measure.pi μ (Set.pi univ fun i => toMeasurable (μ i) ((hμ i).set (e n i))) :=
measure_mono (pi_mono fun i _ => subset_toMeasurable _ _)
_ = ∏ i, μ i (toMeasurable (μ i) ((hμ i).set (e n i))) :=
(pi_pi_aux μ _ fun i => measurableSet_toMeasurable _ _)
_ = ∏ i, μ i ((hμ i).set (e n i)) := by simp only [measure_toMeasurable]
_ < ∞ := ENNReal.prod_lt_top fun i _ => ((hμ i).finite _).ne
· simp_rw [(surjective_decode_iget (ι → ℕ)).iUnion_comp fun x =>
Set.pi univ fun i => (hμ i).set (x i),
iUnion_univ_pi fun i => (hμ i).set, (hμ _).spanning, Set.pi_univ]
#align measure_theory.measure.finite_spanning_sets_in.pi MeasureTheory.Measure.FiniteSpanningSetsIn.pi
/-- A measure on a finite product space equals the product measure if they are equal on rectangles
with as sides sets that generate the corresponding σ-algebras. -/
theorem pi_eq_generateFrom {C : ∀ i, Set (Set (α i))}
(hC : ∀ i, generateFrom (C i) = by apply_assumption) (h2C : ∀ i, IsPiSystem (C i))
(h3C : ∀ i, (μ i).FiniteSpanningSetsIn (C i)) {μν : Measure (∀ i, α i)}
(h₁ : ∀ s : ∀ i, Set (α i), (∀ i, s i ∈ C i) → μν (pi univ s) = ∏ i, μ i (s i)) :
Measure.pi μ = μν := by
have h4C : ∀ (i) (s : Set (α i)), s ∈ C i → MeasurableSet s := by
intro i s hs; rw [← hC]; exact measurableSet_generateFrom hs
refine
(FiniteSpanningSetsIn.pi h3C).ext
(generateFrom_eq_pi hC fun i => (h3C i).isCountablySpanning).symm (IsPiSystem.pi h2C) ?_
rintro _ ⟨s, hs, rfl⟩
rw [mem_univ_pi] at hs
haveI := fun i => (h3C i).sigmaFinite
simp_rw [h₁ s hs, pi_pi_aux μ s fun i => h4C i _ (hs i)]
#align measure_theory.measure.pi_eq_generate_from MeasureTheory.Measure.pi_eq_generateFrom
variable [∀ i, SigmaFinite (μ i)]
/-- A measure on a finite product space equals the product measure if they are equal on
rectangles. -/
theorem pi_eq {μ' : Measure (∀ i, α i)}
(h : ∀ s : ∀ i, Set (α i), (∀ i, MeasurableSet (s i)) → μ' (pi univ s) = ∏ i, μ i (s i)) :
Measure.pi μ = μ' :=
pi_eq_generateFrom (fun _ => generateFrom_measurableSet) (fun _ => isPiSystem_measurableSet)
(fun i => (μ i).toFiniteSpanningSetsIn) h
#align measure_theory.measure.pi_eq MeasureTheory.Measure.pi_eq
variable (μ)
theorem pi'_eq_pi [Encodable ι] : pi' μ = Measure.pi μ :=
Eq.symm <| pi_eq fun s _ => pi'_pi μ s
#align measure_theory.measure.pi'_eq_pi MeasureTheory.Measure.pi'_eq_pi
@[simp]
theorem pi_pi (s : ∀ i, Set (α i)) : Measure.pi μ (pi univ s) = ∏ i, μ i (s i) := by
haveI : Encodable ι := Fintype.toEncodable ι
rw [← pi'_eq_pi, pi'_pi]
#align measure_theory.measure.pi_pi MeasureTheory.Measure.pi_pi
nonrec theorem pi_univ : Measure.pi μ univ = ∏ i, μ i univ := by rw [← pi_univ, pi_pi μ]
#align measure_theory.measure.pi_univ MeasureTheory.Measure.pi_univ
theorem pi_ball [∀ i, MetricSpace (α i)] (x : ∀ i, α i) {r : ℝ} (hr : 0 < r) :
Measure.pi μ (Metric.ball x r) = ∏ i, μ i (Metric.ball (x i) r) := by rw [ball_pi _ hr, pi_pi]
#align measure_theory.measure.pi_ball MeasureTheory.Measure.pi_ball
theorem pi_closedBall [∀ i, MetricSpace (α i)] (x : ∀ i, α i) {r : ℝ} (hr : 0 ≤ r) :
Measure.pi μ (Metric.closedBall x r) = ∏ i, μ i (Metric.closedBall (x i) r) := by
rw [closedBall_pi _ hr, pi_pi]
#align measure_theory.measure.pi_closed_ball MeasureTheory.Measure.pi_closedBall
instance pi.sigmaFinite : SigmaFinite (Measure.pi μ) :=
(FiniteSpanningSetsIn.pi fun i => (μ i).toFiniteSpanningSetsIn).sigmaFinite
#align measure_theory.measure.pi.sigma_finite MeasureTheory.Measure.pi.sigmaFinite
instance {α : ι → Type*} [∀ i, MeasureSpace (α i)] [∀ i, SigmaFinite (volume : Measure (α i))] :
SigmaFinite (volume : Measure (∀ i, α i)) :=
pi.sigmaFinite _
instance pi.instIsFiniteMeasure [∀ i, IsFiniteMeasure (μ i)] :
IsFiniteMeasure (Measure.pi μ) :=
⟨Measure.pi_univ μ ▸ ENNReal.prod_lt_top (fun i _ ↦ measure_ne_top (μ i) _)⟩
instance {α : ι → Type*} [∀ i, MeasureSpace (α i)] [∀ i, IsFiniteMeasure (volume : Measure (α i))] :
IsFiniteMeasure (volume : Measure (∀ i, α i)) :=
pi.instIsFiniteMeasure _
instance pi.instIsProbabilityMeasure [∀ i, IsProbabilityMeasure (μ i)] :
IsProbabilityMeasure (Measure.pi μ) :=
⟨by simp only [Measure.pi_univ, measure_univ, Finset.prod_const_one]⟩
instance {α : ι → Type*} [∀ i, MeasureSpace (α i)]
[∀ i, IsProbabilityMeasure (volume : Measure (α i))] :
IsProbabilityMeasure (volume : Measure (∀ i, α i)) :=
pi.instIsProbabilityMeasure _
theorem pi_of_empty {α : Type*} [Fintype α] [IsEmpty α] {β : α → Type*}
{m : ∀ a, MeasurableSpace (β a)} (μ : ∀ a : α, Measure (β a)) (x : ∀ a, β a := isEmptyElim) :
Measure.pi μ = dirac x := by
haveI : ∀ a, SigmaFinite (μ a) := isEmptyElim
refine pi_eq fun s _ => ?_
rw [Fintype.prod_empty, dirac_apply_of_mem]
exact isEmptyElim (α := α)
#align measure_theory.measure.pi_of_empty MeasureTheory.Measure.pi_of_empty
lemma volume_pi_eq_dirac {ι : Type*} [Fintype ι] [IsEmpty ι]
{α : ι → Type*} [∀ i, MeasureSpace (α i)] (x : ∀ a, α a := isEmptyElim) :
(volume : Measure (∀ i, α i)) = Measure.dirac x :=
Measure.pi_of_empty _ _
@[simp]
theorem pi_empty_univ {α : Type*} [Fintype α] [IsEmpty α] {β : α → Type*}
{m : ∀ α, MeasurableSpace (β α)} (μ : ∀ a : α, Measure (β a)) :
Measure.pi μ (Set.univ) = 1 := by
rw [pi_of_empty, measure_univ]
theorem pi_eval_preimage_null {i : ι} {s : Set (α i)} (hs : μ i s = 0) :
Measure.pi μ (eval i ⁻¹' s) = 0 := by
-- WLOG, `s` is measurable
rcases exists_measurable_superset_of_null hs with ⟨t, hst, _, hμt⟩
suffices Measure.pi μ (eval i ⁻¹' t) = 0 from measure_mono_null (preimage_mono hst) this
-- Now rewrite it as `Set.pi`, and apply `pi_pi`
rw [← univ_pi_update_univ, pi_pi]
apply Finset.prod_eq_zero (Finset.mem_univ i)
simp [hμt]
#align measure_theory.measure.pi_eval_preimage_null MeasureTheory.Measure.pi_eval_preimage_null
theorem pi_hyperplane (i : ι) [NoAtoms (μ i)] (x : α i) :
Measure.pi μ { f : ∀ i, α i | f i = x } = 0 :=
show Measure.pi μ (eval i ⁻¹' {x}) = 0 from pi_eval_preimage_null _ (measure_singleton x)
#align measure_theory.measure.pi_hyperplane MeasureTheory.Measure.pi_hyperplane
theorem ae_eval_ne (i : ι) [NoAtoms (μ i)] (x : α i) : ∀ᵐ y : ∀ i, α i ∂Measure.pi μ, y i ≠ x :=
compl_mem_ae_iff.2 (pi_hyperplane μ i x)
#align measure_theory.measure.ae_eval_ne MeasureTheory.Measure.ae_eval_ne
variable {μ}
theorem tendsto_eval_ae_ae {i : ι} : Tendsto (eval i) (ae (Measure.pi μ)) (ae (μ i)) := fun _ hs =>
pi_eval_preimage_null μ hs
#align measure_theory.measure.tendsto_eval_ae_ae MeasureTheory.Measure.tendsto_eval_ae_ae
theorem ae_pi_le_pi : ae (Measure.pi μ) ≤ Filter.pi fun i => ae (μ i) :=
le_iInf fun _ => tendsto_eval_ae_ae.le_comap
#align measure_theory.measure.ae_pi_le_pi MeasureTheory.Measure.ae_pi_le_pi
theorem ae_eq_pi {β : ι → Type*} {f f' : ∀ i, α i → β i} (h : ∀ i, f i =ᵐ[μ i] f' i) :
(fun (x : ∀ i, α i) i => f i (x i)) =ᵐ[Measure.pi μ] fun x i => f' i (x i) :=
(eventually_all.2 fun i => tendsto_eval_ae_ae.eventually (h i)).mono fun _ hx => funext hx
#align measure_theory.measure.ae_eq_pi MeasureTheory.Measure.ae_eq_pi
theorem ae_le_pi {β : ι → Type*} [∀ i, Preorder (β i)] {f f' : ∀ i, α i → β i}
(h : ∀ i, f i ≤ᵐ[μ i] f' i) :
(fun (x : ∀ i, α i) i => f i (x i)) ≤ᵐ[Measure.pi μ] fun x i => f' i (x i) :=
(eventually_all.2 fun i => tendsto_eval_ae_ae.eventually (h i)).mono fun _ hx => hx
#align measure_theory.measure.ae_le_pi MeasureTheory.Measure.ae_le_pi
theorem ae_le_set_pi {I : Set ι} {s t : ∀ i, Set (α i)} (h : ∀ i ∈ I, s i ≤ᵐ[μ i] t i) :
Set.pi I s ≤ᵐ[Measure.pi μ] Set.pi I t :=
((eventually_all_finite I.toFinite).2 fun i hi => tendsto_eval_ae_ae.eventually (h i hi)).mono
fun _ hst hx i hi => hst i hi <| hx i hi
#align measure_theory.measure.ae_le_set_pi MeasureTheory.Measure.ae_le_set_pi
theorem ae_eq_set_pi {I : Set ι} {s t : ∀ i, Set (α i)} (h : ∀ i ∈ I, s i =ᵐ[μ i] t i) :
Set.pi I s =ᵐ[Measure.pi μ] Set.pi I t :=
(ae_le_set_pi fun i hi => (h i hi).le).antisymm (ae_le_set_pi fun i hi => (h i hi).symm.le)
#align measure_theory.measure.ae_eq_set_pi MeasureTheory.Measure.ae_eq_set_pi
section Intervals
variable [∀ i, PartialOrder (α i)] [∀ i, NoAtoms (μ i)]
theorem pi_Iio_ae_eq_pi_Iic {s : Set ι} {f : ∀ i, α i} :
(pi s fun i => Iio (f i)) =ᵐ[Measure.pi μ] pi s fun i => Iic (f i) :=
ae_eq_set_pi fun _ _ => Iio_ae_eq_Iic
#align measure_theory.measure.pi_Iio_ae_eq_pi_Iic MeasureTheory.Measure.pi_Iio_ae_eq_pi_Iic
theorem pi_Ioi_ae_eq_pi_Ici {s : Set ι} {f : ∀ i, α i} :
(pi s fun i => Ioi (f i)) =ᵐ[Measure.pi μ] pi s fun i => Ici (f i) :=
ae_eq_set_pi fun _ _ => Ioi_ae_eq_Ici
#align measure_theory.measure.pi_Ioi_ae_eq_pi_Ici MeasureTheory.Measure.pi_Ioi_ae_eq_pi_Ici
theorem univ_pi_Iio_ae_eq_Iic {f : ∀ i, α i} :
(pi univ fun i => Iio (f i)) =ᵐ[Measure.pi μ] Iic f := by
rw [← pi_univ_Iic]; exact pi_Iio_ae_eq_pi_Iic
#align measure_theory.measure.univ_pi_Iio_ae_eq_Iic MeasureTheory.Measure.univ_pi_Iio_ae_eq_Iic
theorem univ_pi_Ioi_ae_eq_Ici {f : ∀ i, α i} :
(pi univ fun i => Ioi (f i)) =ᵐ[Measure.pi μ] Ici f := by
rw [← pi_univ_Ici]; exact pi_Ioi_ae_eq_pi_Ici
#align measure_theory.measure.univ_pi_Ioi_ae_eq_Ici MeasureTheory.Measure.univ_pi_Ioi_ae_eq_Ici
theorem pi_Ioo_ae_eq_pi_Icc {s : Set ι} {f g : ∀ i, α i} :
(pi s fun i => Ioo (f i) (g i)) =ᵐ[Measure.pi μ] pi s fun i => Icc (f i) (g i) :=
ae_eq_set_pi fun _ _ => Ioo_ae_eq_Icc
#align measure_theory.measure.pi_Ioo_ae_eq_pi_Icc MeasureTheory.Measure.pi_Ioo_ae_eq_pi_Icc
theorem pi_Ioo_ae_eq_pi_Ioc {s : Set ι} {f g : ∀ i, α i} :
(pi s fun i => Ioo (f i) (g i)) =ᵐ[Measure.pi μ] pi s fun i => Ioc (f i) (g i) :=
ae_eq_set_pi fun _ _ => Ioo_ae_eq_Ioc
#align measure_theory.measure.pi_Ioo_ae_eq_pi_Ioc MeasureTheory.Measure.pi_Ioo_ae_eq_pi_Ioc
theorem univ_pi_Ioo_ae_eq_Icc {f g : ∀ i, α i} :
(pi univ fun i => Ioo (f i) (g i)) =ᵐ[Measure.pi μ] Icc f g := by
rw [← pi_univ_Icc]; exact pi_Ioo_ae_eq_pi_Icc
#align measure_theory.measure.univ_pi_Ioo_ae_eq_Icc MeasureTheory.Measure.univ_pi_Ioo_ae_eq_Icc
theorem pi_Ioc_ae_eq_pi_Icc {s : Set ι} {f g : ∀ i, α i} :
(pi s fun i => Ioc (f i) (g i)) =ᵐ[Measure.pi μ] pi s fun i => Icc (f i) (g i) :=
ae_eq_set_pi fun _ _ => Ioc_ae_eq_Icc
#align measure_theory.measure.pi_Ioc_ae_eq_pi_Icc MeasureTheory.Measure.pi_Ioc_ae_eq_pi_Icc
theorem univ_pi_Ioc_ae_eq_Icc {f g : ∀ i, α i} :
(pi univ fun i => Ioc (f i) (g i)) =ᵐ[Measure.pi μ] Icc f g := by
rw [← pi_univ_Icc]; exact pi_Ioc_ae_eq_pi_Icc
#align measure_theory.measure.univ_pi_Ioc_ae_eq_Icc MeasureTheory.Measure.univ_pi_Ioc_ae_eq_Icc
theorem pi_Ico_ae_eq_pi_Icc {s : Set ι} {f g : ∀ i, α i} :
(pi s fun i => Ico (f i) (g i)) =ᵐ[Measure.pi μ] pi s fun i => Icc (f i) (g i) :=
ae_eq_set_pi fun _ _ => Ico_ae_eq_Icc
#align measure_theory.measure.pi_Ico_ae_eq_pi_Icc MeasureTheory.Measure.pi_Ico_ae_eq_pi_Icc
| Mathlib/MeasureTheory/Constructions/Pi.lean | 565 | 567 | theorem univ_pi_Ico_ae_eq_Icc {f g : ∀ i, α i} :
(pi univ fun i => Ico (f i) (g i)) =ᵐ[Measure.pi μ] Icc f g := by |
rw [← pi_univ_Icc]; exact pi_Ico_ae_eq_pi_Icc
|
/-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Sébastien Gouëzel,
Rémy Degenne, David Loeffler
-/
import Mathlib.Analysis.SpecialFunctions.Pow.Real
#align_import analysis.special_functions.pow.nnreal from "leanprover-community/mathlib"@"4fa54b337f7d52805480306db1b1439c741848c8"
/-!
# Power function on `ℝ≥0` and `ℝ≥0∞`
We construct the power functions `x ^ y` where
* `x` is a nonnegative real number and `y` is a real number;
* `x` is a number from `[0, +∞]` (a.k.a. `ℝ≥0∞`) and `y` is a real number.
We also prove basic properties of these functions.
-/
noncomputable section
open scoped Classical
open Real NNReal ENNReal ComplexConjugate
open Finset Function Set
namespace NNReal
variable {w x y z : ℝ}
/-- The nonnegative real power function `x^y`, defined for `x : ℝ≥0` and `y : ℝ` as the
restriction of the real power function. For `x > 0`, it is equal to `exp (y log x)`. For `x = 0`,
one sets `0 ^ 0 = 1` and `0 ^ y = 0` for `y ≠ 0`. -/
noncomputable def rpow (x : ℝ≥0) (y : ℝ) : ℝ≥0 :=
⟨(x : ℝ) ^ y, Real.rpow_nonneg x.2 y⟩
#align nnreal.rpow NNReal.rpow
noncomputable instance : Pow ℝ≥0 ℝ :=
⟨rpow⟩
@[simp]
theorem rpow_eq_pow (x : ℝ≥0) (y : ℝ) : rpow x y = x ^ y :=
rfl
#align nnreal.rpow_eq_pow NNReal.rpow_eq_pow
@[simp, norm_cast]
theorem coe_rpow (x : ℝ≥0) (y : ℝ) : ((x ^ y : ℝ≥0) : ℝ) = (x : ℝ) ^ y :=
rfl
#align nnreal.coe_rpow NNReal.coe_rpow
@[simp]
theorem rpow_zero (x : ℝ≥0) : x ^ (0 : ℝ) = 1 :=
NNReal.eq <| Real.rpow_zero _
#align nnreal.rpow_zero NNReal.rpow_zero
@[simp]
theorem rpow_eq_zero_iff {x : ℝ≥0} {y : ℝ} : x ^ y = 0 ↔ x = 0 ∧ y ≠ 0 := by
rw [← NNReal.coe_inj, coe_rpow, ← NNReal.coe_eq_zero]
exact Real.rpow_eq_zero_iff_of_nonneg x.2
#align nnreal.rpow_eq_zero_iff NNReal.rpow_eq_zero_iff
@[simp]
theorem zero_rpow {x : ℝ} (h : x ≠ 0) : (0 : ℝ≥0) ^ x = 0 :=
NNReal.eq <| Real.zero_rpow h
#align nnreal.zero_rpow NNReal.zero_rpow
@[simp]
theorem rpow_one (x : ℝ≥0) : x ^ (1 : ℝ) = x :=
NNReal.eq <| Real.rpow_one _
#align nnreal.rpow_one NNReal.rpow_one
@[simp]
theorem one_rpow (x : ℝ) : (1 : ℝ≥0) ^ x = 1 :=
NNReal.eq <| Real.one_rpow _
#align nnreal.one_rpow NNReal.one_rpow
theorem rpow_add {x : ℝ≥0} (hx : x ≠ 0) (y z : ℝ) : x ^ (y + z) = x ^ y * x ^ z :=
NNReal.eq <| Real.rpow_add (pos_iff_ne_zero.2 hx) _ _
#align nnreal.rpow_add NNReal.rpow_add
theorem rpow_add' (x : ℝ≥0) {y z : ℝ} (h : y + z ≠ 0) : x ^ (y + z) = x ^ y * x ^ z :=
NNReal.eq <| Real.rpow_add' x.2 h
#align nnreal.rpow_add' NNReal.rpow_add'
/-- Variant of `NNReal.rpow_add'` that avoids having to prove `y + z = w` twice. -/
lemma rpow_of_add_eq (x : ℝ≥0) (hw : w ≠ 0) (h : y + z = w) : x ^ w = x ^ y * x ^ z := by
rw [← h, rpow_add']; rwa [h]
theorem rpow_mul (x : ℝ≥0) (y z : ℝ) : x ^ (y * z) = (x ^ y) ^ z :=
NNReal.eq <| Real.rpow_mul x.2 y z
#align nnreal.rpow_mul NNReal.rpow_mul
theorem rpow_neg (x : ℝ≥0) (y : ℝ) : x ^ (-y) = (x ^ y)⁻¹ :=
NNReal.eq <| Real.rpow_neg x.2 _
#align nnreal.rpow_neg NNReal.rpow_neg
theorem rpow_neg_one (x : ℝ≥0) : x ^ (-1 : ℝ) = x⁻¹ := by simp [rpow_neg]
#align nnreal.rpow_neg_one NNReal.rpow_neg_one
theorem rpow_sub {x : ℝ≥0} (hx : x ≠ 0) (y z : ℝ) : x ^ (y - z) = x ^ y / x ^ z :=
NNReal.eq <| Real.rpow_sub (pos_iff_ne_zero.2 hx) y z
#align nnreal.rpow_sub NNReal.rpow_sub
theorem rpow_sub' (x : ℝ≥0) {y z : ℝ} (h : y - z ≠ 0) : x ^ (y - z) = x ^ y / x ^ z :=
NNReal.eq <| Real.rpow_sub' x.2 h
#align nnreal.rpow_sub' NNReal.rpow_sub'
theorem rpow_inv_rpow_self {y : ℝ} (hy : y ≠ 0) (x : ℝ≥0) : (x ^ y) ^ (1 / y) = x := by
field_simp [← rpow_mul]
#align nnreal.rpow_inv_rpow_self NNReal.rpow_inv_rpow_self
theorem rpow_self_rpow_inv {y : ℝ} (hy : y ≠ 0) (x : ℝ≥0) : (x ^ (1 / y)) ^ y = x := by
field_simp [← rpow_mul]
#align nnreal.rpow_self_rpow_inv NNReal.rpow_self_rpow_inv
theorem inv_rpow (x : ℝ≥0) (y : ℝ) : x⁻¹ ^ y = (x ^ y)⁻¹ :=
NNReal.eq <| Real.inv_rpow x.2 y
#align nnreal.inv_rpow NNReal.inv_rpow
theorem div_rpow (x y : ℝ≥0) (z : ℝ) : (x / y) ^ z = x ^ z / y ^ z :=
NNReal.eq <| Real.div_rpow x.2 y.2 z
#align nnreal.div_rpow NNReal.div_rpow
theorem sqrt_eq_rpow (x : ℝ≥0) : sqrt x = x ^ (1 / (2 : ℝ)) := by
refine NNReal.eq ?_
push_cast
exact Real.sqrt_eq_rpow x.1
#align nnreal.sqrt_eq_rpow NNReal.sqrt_eq_rpow
@[simp, norm_cast]
theorem rpow_natCast (x : ℝ≥0) (n : ℕ) : x ^ (n : ℝ) = x ^ n :=
NNReal.eq <| by simpa only [coe_rpow, coe_pow] using Real.rpow_natCast x n
#align nnreal.rpow_nat_cast NNReal.rpow_natCast
@[deprecated (since := "2024-04-17")]
alias rpow_nat_cast := rpow_natCast
@[simp]
lemma rpow_ofNat (x : ℝ≥0) (n : ℕ) [n.AtLeastTwo] :
x ^ (no_index (OfNat.ofNat n) : ℝ) = x ^ (OfNat.ofNat n : ℕ) :=
rpow_natCast x n
theorem rpow_two (x : ℝ≥0) : x ^ (2 : ℝ) = x ^ 2 := rpow_ofNat x 2
#align nnreal.rpow_two NNReal.rpow_two
theorem mul_rpow {x y : ℝ≥0} {z : ℝ} : (x * y) ^ z = x ^ z * y ^ z :=
NNReal.eq <| Real.mul_rpow x.2 y.2
#align nnreal.mul_rpow NNReal.mul_rpow
/-- `rpow` as a `MonoidHom`-/
@[simps]
def rpowMonoidHom (r : ℝ) : ℝ≥0 →* ℝ≥0 where
toFun := (· ^ r)
map_one' := one_rpow _
map_mul' _x _y := mul_rpow
/-- `rpow` variant of `List.prod_map_pow` for `ℝ≥0`-/
theorem list_prod_map_rpow (l : List ℝ≥0) (r : ℝ) :
(l.map (· ^ r)).prod = l.prod ^ r :=
l.prod_hom (rpowMonoidHom r)
theorem list_prod_map_rpow' {ι} (l : List ι) (f : ι → ℝ≥0) (r : ℝ) :
(l.map (f · ^ r)).prod = (l.map f).prod ^ r := by
rw [← list_prod_map_rpow, List.map_map]; rfl
/-- `rpow` version of `Multiset.prod_map_pow` for `ℝ≥0`. -/
lemma multiset_prod_map_rpow {ι} (s : Multiset ι) (f : ι → ℝ≥0) (r : ℝ) :
(s.map (f · ^ r)).prod = (s.map f).prod ^ r :=
s.prod_hom' (rpowMonoidHom r) _
/-- `rpow` version of `Finset.prod_pow` for `ℝ≥0`. -/
lemma finset_prod_rpow {ι} (s : Finset ι) (f : ι → ℝ≥0) (r : ℝ) :
(∏ i ∈ s, f i ^ r) = (∏ i ∈ s, f i) ^ r :=
multiset_prod_map_rpow _ _ _
-- note: these don't really belong here, but they're much easier to prove in terms of the above
section Real
/-- `rpow` version of `List.prod_map_pow` for `Real`. -/
theorem _root_.Real.list_prod_map_rpow (l : List ℝ) (hl : ∀ x ∈ l, (0 : ℝ) ≤ x) (r : ℝ) :
(l.map (· ^ r)).prod = l.prod ^ r := by
lift l to List ℝ≥0 using hl
have := congr_arg ((↑) : ℝ≥0 → ℝ) (NNReal.list_prod_map_rpow l r)
push_cast at this
rw [List.map_map] at this ⊢
exact mod_cast this
theorem _root_.Real.list_prod_map_rpow' {ι} (l : List ι) (f : ι → ℝ)
(hl : ∀ i ∈ l, (0 : ℝ) ≤ f i) (r : ℝ) :
(l.map (f · ^ r)).prod = (l.map f).prod ^ r := by
rw [← Real.list_prod_map_rpow (l.map f) _ r, List.map_map]
· rfl
simpa using hl
/-- `rpow` version of `Multiset.prod_map_pow`. -/
theorem _root_.Real.multiset_prod_map_rpow {ι} (s : Multiset ι) (f : ι → ℝ)
(hs : ∀ i ∈ s, (0 : ℝ) ≤ f i) (r : ℝ) :
(s.map (f · ^ r)).prod = (s.map f).prod ^ r := by
induction' s using Quotient.inductionOn with l
simpa using Real.list_prod_map_rpow' l f hs r
/-- `rpow` version of `Finset.prod_pow`. -/
theorem _root_.Real.finset_prod_rpow
{ι} (s : Finset ι) (f : ι → ℝ) (hs : ∀ i ∈ s, 0 ≤ f i) (r : ℝ) :
(∏ i ∈ s, f i ^ r) = (∏ i ∈ s, f i) ^ r :=
Real.multiset_prod_map_rpow s.val f hs r
end Real
@[gcongr] theorem rpow_le_rpow {x y : ℝ≥0} {z : ℝ} (h₁ : x ≤ y) (h₂ : 0 ≤ z) : x ^ z ≤ y ^ z :=
Real.rpow_le_rpow x.2 h₁ h₂
#align nnreal.rpow_le_rpow NNReal.rpow_le_rpow
@[gcongr] theorem rpow_lt_rpow {x y : ℝ≥0} {z : ℝ} (h₁ : x < y) (h₂ : 0 < z) : x ^ z < y ^ z :=
Real.rpow_lt_rpow x.2 h₁ h₂
#align nnreal.rpow_lt_rpow NNReal.rpow_lt_rpow
theorem rpow_lt_rpow_iff {x y : ℝ≥0} {z : ℝ} (hz : 0 < z) : x ^ z < y ^ z ↔ x < y :=
Real.rpow_lt_rpow_iff x.2 y.2 hz
#align nnreal.rpow_lt_rpow_iff NNReal.rpow_lt_rpow_iff
theorem rpow_le_rpow_iff {x y : ℝ≥0} {z : ℝ} (hz : 0 < z) : x ^ z ≤ y ^ z ↔ x ≤ y :=
Real.rpow_le_rpow_iff x.2 y.2 hz
#align nnreal.rpow_le_rpow_iff NNReal.rpow_le_rpow_iff
theorem le_rpow_one_div_iff {x y : ℝ≥0} {z : ℝ} (hz : 0 < z) : x ≤ y ^ (1 / z) ↔ x ^ z ≤ y := by
rw [← rpow_le_rpow_iff hz, rpow_self_rpow_inv hz.ne']
#align nnreal.le_rpow_one_div_iff NNReal.le_rpow_one_div_iff
theorem rpow_one_div_le_iff {x y : ℝ≥0} {z : ℝ} (hz : 0 < z) : x ^ (1 / z) ≤ y ↔ x ≤ y ^ z := by
rw [← rpow_le_rpow_iff hz, rpow_self_rpow_inv hz.ne']
#align nnreal.rpow_one_div_le_iff NNReal.rpow_one_div_le_iff
@[gcongr] theorem rpow_lt_rpow_of_exponent_lt {x : ℝ≥0} {y z : ℝ} (hx : 1 < x) (hyz : y < z) :
x ^ y < x ^ z :=
Real.rpow_lt_rpow_of_exponent_lt hx hyz
#align nnreal.rpow_lt_rpow_of_exponent_lt NNReal.rpow_lt_rpow_of_exponent_lt
@[gcongr] theorem rpow_le_rpow_of_exponent_le {x : ℝ≥0} {y z : ℝ} (hx : 1 ≤ x) (hyz : y ≤ z) :
x ^ y ≤ x ^ z :=
Real.rpow_le_rpow_of_exponent_le hx hyz
#align nnreal.rpow_le_rpow_of_exponent_le NNReal.rpow_le_rpow_of_exponent_le
theorem rpow_lt_rpow_of_exponent_gt {x : ℝ≥0} {y z : ℝ} (hx0 : 0 < x) (hx1 : x < 1) (hyz : z < y) :
x ^ y < x ^ z :=
Real.rpow_lt_rpow_of_exponent_gt hx0 hx1 hyz
#align nnreal.rpow_lt_rpow_of_exponent_gt NNReal.rpow_lt_rpow_of_exponent_gt
theorem rpow_le_rpow_of_exponent_ge {x : ℝ≥0} {y z : ℝ} (hx0 : 0 < x) (hx1 : x ≤ 1) (hyz : z ≤ y) :
x ^ y ≤ x ^ z :=
Real.rpow_le_rpow_of_exponent_ge hx0 hx1 hyz
#align nnreal.rpow_le_rpow_of_exponent_ge NNReal.rpow_le_rpow_of_exponent_ge
theorem rpow_pos {p : ℝ} {x : ℝ≥0} (hx_pos : 0 < x) : 0 < x ^ p := by
have rpow_pos_of_nonneg : ∀ {p : ℝ}, 0 < p → 0 < x ^ p := by
intro p hp_pos
rw [← zero_rpow hp_pos.ne']
exact rpow_lt_rpow hx_pos hp_pos
rcases lt_trichotomy (0 : ℝ) p with (hp_pos | rfl | hp_neg)
· exact rpow_pos_of_nonneg hp_pos
· simp only [zero_lt_one, rpow_zero]
· rw [← neg_neg p, rpow_neg, inv_pos]
exact rpow_pos_of_nonneg (neg_pos.mpr hp_neg)
#align nnreal.rpow_pos NNReal.rpow_pos
theorem rpow_lt_one {x : ℝ≥0} {z : ℝ} (hx1 : x < 1) (hz : 0 < z) : x ^ z < 1 :=
Real.rpow_lt_one (coe_nonneg x) hx1 hz
#align nnreal.rpow_lt_one NNReal.rpow_lt_one
theorem rpow_le_one {x : ℝ≥0} {z : ℝ} (hx2 : x ≤ 1) (hz : 0 ≤ z) : x ^ z ≤ 1 :=
Real.rpow_le_one x.2 hx2 hz
#align nnreal.rpow_le_one NNReal.rpow_le_one
theorem rpow_lt_one_of_one_lt_of_neg {x : ℝ≥0} {z : ℝ} (hx : 1 < x) (hz : z < 0) : x ^ z < 1 :=
Real.rpow_lt_one_of_one_lt_of_neg hx hz
#align nnreal.rpow_lt_one_of_one_lt_of_neg NNReal.rpow_lt_one_of_one_lt_of_neg
theorem rpow_le_one_of_one_le_of_nonpos {x : ℝ≥0} {z : ℝ} (hx : 1 ≤ x) (hz : z ≤ 0) : x ^ z ≤ 1 :=
Real.rpow_le_one_of_one_le_of_nonpos hx hz
#align nnreal.rpow_le_one_of_one_le_of_nonpos NNReal.rpow_le_one_of_one_le_of_nonpos
theorem one_lt_rpow {x : ℝ≥0} {z : ℝ} (hx : 1 < x) (hz : 0 < z) : 1 < x ^ z :=
Real.one_lt_rpow hx hz
#align nnreal.one_lt_rpow NNReal.one_lt_rpow
theorem one_le_rpow {x : ℝ≥0} {z : ℝ} (h : 1 ≤ x) (h₁ : 0 ≤ z) : 1 ≤ x ^ z :=
Real.one_le_rpow h h₁
#align nnreal.one_le_rpow NNReal.one_le_rpow
theorem one_lt_rpow_of_pos_of_lt_one_of_neg {x : ℝ≥0} {z : ℝ} (hx1 : 0 < x) (hx2 : x < 1)
(hz : z < 0) : 1 < x ^ z :=
Real.one_lt_rpow_of_pos_of_lt_one_of_neg hx1 hx2 hz
#align nnreal.one_lt_rpow_of_pos_of_lt_one_of_neg NNReal.one_lt_rpow_of_pos_of_lt_one_of_neg
theorem one_le_rpow_of_pos_of_le_one_of_nonpos {x : ℝ≥0} {z : ℝ} (hx1 : 0 < x) (hx2 : x ≤ 1)
(hz : z ≤ 0) : 1 ≤ x ^ z :=
Real.one_le_rpow_of_pos_of_le_one_of_nonpos hx1 hx2 hz
#align nnreal.one_le_rpow_of_pos_of_le_one_of_nonpos NNReal.one_le_rpow_of_pos_of_le_one_of_nonpos
theorem rpow_le_self_of_le_one {x : ℝ≥0} {z : ℝ} (hx : x ≤ 1) (h_one_le : 1 ≤ z) : x ^ z ≤ x := by
rcases eq_bot_or_bot_lt x with (rfl | (h : 0 < x))
· have : z ≠ 0 := by linarith
simp [this]
nth_rw 2 [← NNReal.rpow_one x]
exact NNReal.rpow_le_rpow_of_exponent_ge h hx h_one_le
#align nnreal.rpow_le_self_of_le_one NNReal.rpow_le_self_of_le_one
theorem rpow_left_injective {x : ℝ} (hx : x ≠ 0) : Function.Injective fun y : ℝ≥0 => y ^ x :=
fun y z hyz => by simpa only [rpow_inv_rpow_self hx] using congr_arg (fun y => y ^ (1 / x)) hyz
#align nnreal.rpow_left_injective NNReal.rpow_left_injective
theorem rpow_eq_rpow_iff {x y : ℝ≥0} {z : ℝ} (hz : z ≠ 0) : x ^ z = y ^ z ↔ x = y :=
(rpow_left_injective hz).eq_iff
#align nnreal.rpow_eq_rpow_iff NNReal.rpow_eq_rpow_iff
theorem rpow_left_surjective {x : ℝ} (hx : x ≠ 0) : Function.Surjective fun y : ℝ≥0 => y ^ x :=
fun y => ⟨y ^ x⁻¹, by simp_rw [← rpow_mul, _root_.inv_mul_cancel hx, rpow_one]⟩
#align nnreal.rpow_left_surjective NNReal.rpow_left_surjective
theorem rpow_left_bijective {x : ℝ} (hx : x ≠ 0) : Function.Bijective fun y : ℝ≥0 => y ^ x :=
⟨rpow_left_injective hx, rpow_left_surjective hx⟩
#align nnreal.rpow_left_bijective NNReal.rpow_left_bijective
theorem eq_rpow_one_div_iff {x y : ℝ≥0} {z : ℝ} (hz : z ≠ 0) : x = y ^ (1 / z) ↔ x ^ z = y := by
rw [← rpow_eq_rpow_iff hz, rpow_self_rpow_inv hz]
#align nnreal.eq_rpow_one_div_iff NNReal.eq_rpow_one_div_iff
theorem rpow_one_div_eq_iff {x y : ℝ≥0} {z : ℝ} (hz : z ≠ 0) : x ^ (1 / z) = y ↔ x = y ^ z := by
rw [← rpow_eq_rpow_iff hz, rpow_self_rpow_inv hz]
#align nnreal.rpow_one_div_eq_iff NNReal.rpow_one_div_eq_iff
@[simp] lemma rpow_rpow_inv {y : ℝ} (hy : y ≠ 0) (x : ℝ≥0) : (x ^ y) ^ y⁻¹ = x := by
rw [← rpow_mul, mul_inv_cancel hy, rpow_one]
@[simp] lemma rpow_inv_rpow {y : ℝ} (hy : y ≠ 0) (x : ℝ≥0) : (x ^ y⁻¹) ^ y = x := by
rw [← rpow_mul, inv_mul_cancel hy, rpow_one]
theorem pow_rpow_inv_natCast (x : ℝ≥0) {n : ℕ} (hn : n ≠ 0) : (x ^ n) ^ (n⁻¹ : ℝ) = x := by
rw [← NNReal.coe_inj, coe_rpow, NNReal.coe_pow]
exact Real.pow_rpow_inv_natCast x.2 hn
#align nnreal.pow_nat_rpow_nat_inv NNReal.pow_rpow_inv_natCast
theorem rpow_inv_natCast_pow (x : ℝ≥0) {n : ℕ} (hn : n ≠ 0) : (x ^ (n⁻¹ : ℝ)) ^ n = x := by
rw [← NNReal.coe_inj, NNReal.coe_pow, coe_rpow]
exact Real.rpow_inv_natCast_pow x.2 hn
#align nnreal.rpow_nat_inv_pow_nat NNReal.rpow_inv_natCast_pow
theorem _root_.Real.toNNReal_rpow_of_nonneg {x y : ℝ} (hx : 0 ≤ x) :
Real.toNNReal (x ^ y) = Real.toNNReal x ^ y := by
nth_rw 1 [← Real.coe_toNNReal x hx]
rw [← NNReal.coe_rpow, Real.toNNReal_coe]
#align real.to_nnreal_rpow_of_nonneg Real.toNNReal_rpow_of_nonneg
theorem strictMono_rpow_of_pos {z : ℝ} (h : 0 < z) : StrictMono fun x : ℝ≥0 => x ^ z :=
fun x y hxy => by simp only [NNReal.rpow_lt_rpow hxy h, coe_lt_coe]
theorem monotone_rpow_of_nonneg {z : ℝ} (h : 0 ≤ z) : Monotone fun x : ℝ≥0 => x ^ z :=
h.eq_or_lt.elim (fun h0 => h0 ▸ by simp only [rpow_zero, monotone_const]) fun h0 =>
(strictMono_rpow_of_pos h0).monotone
/-- Bundles `fun x : ℝ≥0 => x ^ y` into an order isomorphism when `y : ℝ` is positive,
where the inverse is `fun x : ℝ≥0 => x ^ (1 / y)`. -/
@[simps! apply]
def orderIsoRpow (y : ℝ) (hy : 0 < y) : ℝ≥0 ≃o ℝ≥0 :=
(strictMono_rpow_of_pos hy).orderIsoOfRightInverse (fun x => x ^ y) (fun x => x ^ (1 / y))
fun x => by
dsimp
rw [← rpow_mul, one_div_mul_cancel hy.ne.symm, rpow_one]
theorem orderIsoRpow_symm_eq (y : ℝ) (hy : 0 < y) :
(orderIsoRpow y hy).symm = orderIsoRpow (1 / y) (one_div_pos.2 hy) := by
simp only [orderIsoRpow, one_div_one_div]; rfl
end NNReal
namespace ENNReal
/-- The real power function `x^y` on extended nonnegative reals, defined for `x : ℝ≥0∞` and
`y : ℝ` as the restriction of the real power function if `0 < x < ⊤`, and with the natural values
for `0` and `⊤` (i.e., `0 ^ x = 0` for `x > 0`, `1` for `x = 0` and `⊤` for `x < 0`, and
`⊤ ^ x = 1 / 0 ^ x`). -/
noncomputable def rpow : ℝ≥0∞ → ℝ → ℝ≥0∞
| some x, y => if x = 0 ∧ y < 0 then ⊤ else (x ^ y : ℝ≥0)
| none, y => if 0 < y then ⊤ else if y = 0 then 1 else 0
#align ennreal.rpow ENNReal.rpow
noncomputable instance : Pow ℝ≥0∞ ℝ :=
⟨rpow⟩
@[simp]
theorem rpow_eq_pow (x : ℝ≥0∞) (y : ℝ) : rpow x y = x ^ y :=
rfl
#align ennreal.rpow_eq_pow ENNReal.rpow_eq_pow
@[simp]
theorem rpow_zero {x : ℝ≥0∞} : x ^ (0 : ℝ) = 1 := by
cases x <;>
· dsimp only [(· ^ ·), Pow.pow, rpow]
simp [lt_irrefl]
#align ennreal.rpow_zero ENNReal.rpow_zero
theorem top_rpow_def (y : ℝ) : (⊤ : ℝ≥0∞) ^ y = if 0 < y then ⊤ else if y = 0 then 1 else 0 :=
rfl
#align ennreal.top_rpow_def ENNReal.top_rpow_def
@[simp]
theorem top_rpow_of_pos {y : ℝ} (h : 0 < y) : (⊤ : ℝ≥0∞) ^ y = ⊤ := by simp [top_rpow_def, h]
#align ennreal.top_rpow_of_pos ENNReal.top_rpow_of_pos
@[simp]
theorem top_rpow_of_neg {y : ℝ} (h : y < 0) : (⊤ : ℝ≥0∞) ^ y = 0 := by
simp [top_rpow_def, asymm h, ne_of_lt h]
#align ennreal.top_rpow_of_neg ENNReal.top_rpow_of_neg
@[simp]
theorem zero_rpow_of_pos {y : ℝ} (h : 0 < y) : (0 : ℝ≥0∞) ^ y = 0 := by
rw [← ENNReal.coe_zero, ← ENNReal.some_eq_coe]
dsimp only [(· ^ ·), rpow, Pow.pow]
simp [h, asymm h, ne_of_gt h]
#align ennreal.zero_rpow_of_pos ENNReal.zero_rpow_of_pos
@[simp]
theorem zero_rpow_of_neg {y : ℝ} (h : y < 0) : (0 : ℝ≥0∞) ^ y = ⊤ := by
rw [← ENNReal.coe_zero, ← ENNReal.some_eq_coe]
dsimp only [(· ^ ·), rpow, Pow.pow]
simp [h, ne_of_gt h]
#align ennreal.zero_rpow_of_neg ENNReal.zero_rpow_of_neg
theorem zero_rpow_def (y : ℝ) : (0 : ℝ≥0∞) ^ y = if 0 < y then 0 else if y = 0 then 1 else ⊤ := by
rcases lt_trichotomy (0 : ℝ) y with (H | rfl | H)
· simp [H, ne_of_gt, zero_rpow_of_pos, lt_irrefl]
· simp [lt_irrefl]
· simp [H, asymm H, ne_of_lt, zero_rpow_of_neg]
#align ennreal.zero_rpow_def ENNReal.zero_rpow_def
@[simp]
theorem zero_rpow_mul_self (y : ℝ) : (0 : ℝ≥0∞) ^ y * (0 : ℝ≥0∞) ^ y = (0 : ℝ≥0∞) ^ y := by
rw [zero_rpow_def]
split_ifs
exacts [zero_mul _, one_mul _, top_mul_top]
#align ennreal.zero_rpow_mul_self ENNReal.zero_rpow_mul_self
@[norm_cast]
theorem coe_rpow_of_ne_zero {x : ℝ≥0} (h : x ≠ 0) (y : ℝ) : (x : ℝ≥0∞) ^ y = (x ^ y : ℝ≥0) := by
rw [← ENNReal.some_eq_coe]
dsimp only [(· ^ ·), Pow.pow, rpow]
simp [h]
#align ennreal.coe_rpow_of_ne_zero ENNReal.coe_rpow_of_ne_zero
@[norm_cast]
theorem coe_rpow_of_nonneg (x : ℝ≥0) {y : ℝ} (h : 0 ≤ y) : (x : ℝ≥0∞) ^ y = (x ^ y : ℝ≥0) := by
by_cases hx : x = 0
· rcases le_iff_eq_or_lt.1 h with (H | H)
· simp [hx, H.symm]
· simp [hx, zero_rpow_of_pos H, NNReal.zero_rpow (ne_of_gt H)]
· exact coe_rpow_of_ne_zero hx _
#align ennreal.coe_rpow_of_nonneg ENNReal.coe_rpow_of_nonneg
theorem coe_rpow_def (x : ℝ≥0) (y : ℝ) :
(x : ℝ≥0∞) ^ y = if x = 0 ∧ y < 0 then ⊤ else ↑(x ^ y) :=
rfl
#align ennreal.coe_rpow_def ENNReal.coe_rpow_def
@[simp]
theorem rpow_one (x : ℝ≥0∞) : x ^ (1 : ℝ) = x := by
cases x
· exact dif_pos zero_lt_one
· change ite _ _ _ = _
simp only [NNReal.rpow_one, some_eq_coe, ite_eq_right_iff, top_ne_coe, and_imp]
exact fun _ => zero_le_one.not_lt
#align ennreal.rpow_one ENNReal.rpow_one
@[simp]
theorem one_rpow (x : ℝ) : (1 : ℝ≥0∞) ^ x = 1 := by
rw [← coe_one, coe_rpow_of_ne_zero one_ne_zero]
simp
#align ennreal.one_rpow ENNReal.one_rpow
@[simp]
| Mathlib/Analysis/SpecialFunctions/Pow/NNReal.lean | 481 | 488 | theorem rpow_eq_zero_iff {x : ℝ≥0∞} {y : ℝ} : x ^ y = 0 ↔ x = 0 ∧ 0 < y ∨ x = ⊤ ∧ y < 0 := by |
cases' x with x
· rcases lt_trichotomy y 0 with (H | H | H) <;>
simp [H, top_rpow_of_neg, top_rpow_of_pos, le_of_lt]
· by_cases h : x = 0
· rcases lt_trichotomy y 0 with (H | H | H) <;>
simp [h, H, zero_rpow_of_neg, zero_rpow_of_pos, le_of_lt]
· simp [coe_rpow_of_ne_zero h, h]
|
/-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir
-/
import Mathlib.Algebra.Order.CauSeq.BigOperators
import Mathlib.Data.Complex.Abs
import Mathlib.Data.Complex.BigOperators
import Mathlib.Data.Nat.Choose.Sum
#align_import data.complex.exponential from "leanprover-community/mathlib"@"a8b2226cfb0a79f5986492053fc49b1a0c6aeffb"
/-!
# Exponential, trigonometric and hyperbolic trigonometric functions
This file contains the definitions of the real and complex exponential, sine, cosine, tangent,
hyperbolic sine, hyperbolic cosine, and hyperbolic tangent functions.
-/
open CauSeq Finset IsAbsoluteValue
open scoped Classical ComplexConjugate
namespace Complex
theorem isCauSeq_abs_exp (z : ℂ) :
IsCauSeq _root_.abs fun n => ∑ m ∈ range n, abs (z ^ m / m.factorial) :=
let ⟨n, hn⟩ := exists_nat_gt (abs z)
have hn0 : (0 : ℝ) < n := lt_of_le_of_lt (abs.nonneg _) hn
IsCauSeq.series_ratio_test n (abs z / n) (div_nonneg (abs.nonneg _) (le_of_lt hn0))
(by rwa [div_lt_iff hn0, one_mul]) fun m hm => by
rw [abs_abs, abs_abs, Nat.factorial_succ, pow_succ', mul_comm m.succ, Nat.cast_mul, ← div_div,
mul_div_assoc, mul_div_right_comm, map_mul, map_div₀, abs_natCast]
gcongr
exact le_trans hm (Nat.le_succ _)
#align complex.is_cau_abs_exp Complex.isCauSeq_abs_exp
noncomputable section
theorem isCauSeq_exp (z : ℂ) : IsCauSeq abs fun n => ∑ m ∈ range n, z ^ m / m.factorial :=
(isCauSeq_abs_exp z).of_abv
#align complex.is_cau_exp Complex.isCauSeq_exp
/-- The Cauchy sequence consisting of partial sums of the Taylor series of
the complex exponential function -/
-- Porting note (#11180): removed `@[pp_nodot]`
def exp' (z : ℂ) : CauSeq ℂ Complex.abs :=
⟨fun n => ∑ m ∈ range n, z ^ m / m.factorial, isCauSeq_exp z⟩
#align complex.exp' Complex.exp'
/-- The complex exponential function, defined via its Taylor series -/
-- Porting note (#11180): removed `@[pp_nodot]`
-- Porting note: removed `irreducible` attribute, so I can prove things
def exp (z : ℂ) : ℂ :=
CauSeq.lim (exp' z)
#align complex.exp Complex.exp
/-- The complex sine function, defined via `exp` -/
-- Porting note (#11180): removed `@[pp_nodot]`
def sin (z : ℂ) : ℂ :=
(exp (-z * I) - exp (z * I)) * I / 2
#align complex.sin Complex.sin
/-- The complex cosine function, defined via `exp` -/
-- Porting note (#11180): removed `@[pp_nodot]`
def cos (z : ℂ) : ℂ :=
(exp (z * I) + exp (-z * I)) / 2
#align complex.cos Complex.cos
/-- The complex tangent function, defined as `sin z / cos z` -/
-- Porting note (#11180): removed `@[pp_nodot]`
def tan (z : ℂ) : ℂ :=
sin z / cos z
#align complex.tan Complex.tan
/-- The complex cotangent function, defined as `cos z / sin z` -/
def cot (z : ℂ) : ℂ :=
cos z / sin z
/-- The complex hyperbolic sine function, defined via `exp` -/
-- Porting note (#11180): removed `@[pp_nodot]`
def sinh (z : ℂ) : ℂ :=
(exp z - exp (-z)) / 2
#align complex.sinh Complex.sinh
/-- The complex hyperbolic cosine function, defined via `exp` -/
-- Porting note (#11180): removed `@[pp_nodot]`
def cosh (z : ℂ) : ℂ :=
(exp z + exp (-z)) / 2
#align complex.cosh Complex.cosh
/-- The complex hyperbolic tangent function, defined as `sinh z / cosh z` -/
-- Porting note (#11180): removed `@[pp_nodot]`
def tanh (z : ℂ) : ℂ :=
sinh z / cosh z
#align complex.tanh Complex.tanh
/-- scoped notation for the complex exponential function -/
scoped notation "cexp" => Complex.exp
end
end Complex
namespace Real
open Complex
noncomputable section
/-- The real exponential function, defined as the real part of the complex exponential -/
-- Porting note (#11180): removed `@[pp_nodot]`
nonrec def exp (x : ℝ) : ℝ :=
(exp x).re
#align real.exp Real.exp
/-- The real sine function, defined as the real part of the complex sine -/
-- Porting note (#11180): removed `@[pp_nodot]`
nonrec def sin (x : ℝ) : ℝ :=
(sin x).re
#align real.sin Real.sin
/-- The real cosine function, defined as the real part of the complex cosine -/
-- Porting note (#11180): removed `@[pp_nodot]`
nonrec def cos (x : ℝ) : ℝ :=
(cos x).re
#align real.cos Real.cos
/-- The real tangent function, defined as the real part of the complex tangent -/
-- Porting note (#11180): removed `@[pp_nodot]`
nonrec def tan (x : ℝ) : ℝ :=
(tan x).re
#align real.tan Real.tan
/-- The real cotangent function, defined as the real part of the complex cotangent -/
nonrec def cot (x : ℝ) : ℝ :=
(cot x).re
/-- The real hypebolic sine function, defined as the real part of the complex hyperbolic sine -/
-- Porting note (#11180): removed `@[pp_nodot]`
nonrec def sinh (x : ℝ) : ℝ :=
(sinh x).re
#align real.sinh Real.sinh
/-- The real hypebolic cosine function, defined as the real part of the complex hyperbolic cosine -/
-- Porting note (#11180): removed `@[pp_nodot]`
nonrec def cosh (x : ℝ) : ℝ :=
(cosh x).re
#align real.cosh Real.cosh
/-- The real hypebolic tangent function, defined as the real part of
the complex hyperbolic tangent -/
-- Porting note (#11180): removed `@[pp_nodot]`
nonrec def tanh (x : ℝ) : ℝ :=
(tanh x).re
#align real.tanh Real.tanh
/-- scoped notation for the real exponential function -/
scoped notation "rexp" => Real.exp
end
end Real
namespace Complex
variable (x y : ℂ)
@[simp]
theorem exp_zero : exp 0 = 1 := by
rw [exp]
refine lim_eq_of_equiv_const fun ε ε0 => ⟨1, fun j hj => ?_⟩
convert (config := .unfoldSameFun) ε0 -- Porting note: ε0 : ε > 0 but goal is _ < ε
cases' j with j j
· exact absurd hj (not_le_of_gt zero_lt_one)
· dsimp [exp']
induction' j with j ih
· dsimp [exp']; simp [show Nat.succ 0 = 1 from rfl]
· rw [← ih (by simp [Nat.succ_le_succ])]
simp only [sum_range_succ, pow_succ]
simp
#align complex.exp_zero Complex.exp_zero
theorem exp_add : exp (x + y) = exp x * exp y := by
have hj : ∀ j : ℕ, (∑ m ∈ range j, (x + y) ^ m / m.factorial) =
∑ i ∈ range j, ∑ k ∈ range (i + 1), x ^ k / k.factorial *
(y ^ (i - k) / (i - k).factorial) := by
intro j
refine Finset.sum_congr rfl fun m _ => ?_
rw [add_pow, div_eq_mul_inv, sum_mul]
refine Finset.sum_congr rfl fun I hi => ?_
have h₁ : (m.choose I : ℂ) ≠ 0 :=
Nat.cast_ne_zero.2 (pos_iff_ne_zero.1 (Nat.choose_pos (Nat.le_of_lt_succ (mem_range.1 hi))))
have h₂ := Nat.choose_mul_factorial_mul_factorial (Nat.le_of_lt_succ <| Finset.mem_range.1 hi)
rw [← h₂, Nat.cast_mul, Nat.cast_mul, mul_inv, mul_inv]
simp only [mul_left_comm (m.choose I : ℂ), mul_assoc, mul_left_comm (m.choose I : ℂ)⁻¹,
mul_comm (m.choose I : ℂ)]
rw [inv_mul_cancel h₁]
simp [div_eq_mul_inv, mul_comm, mul_assoc, mul_left_comm]
simp_rw [exp, exp', lim_mul_lim]
apply (lim_eq_lim_of_equiv _).symm
simp only [hj]
exact cauchy_product (isCauSeq_abs_exp x) (isCauSeq_exp y)
#align complex.exp_add Complex.exp_add
-- Porting note (#11445): new definition
/-- the exponential function as a monoid hom from `Multiplicative ℂ` to `ℂ` -/
noncomputable def expMonoidHom : MonoidHom (Multiplicative ℂ) ℂ :=
{ toFun := fun z => exp (Multiplicative.toAdd z),
map_one' := by simp,
map_mul' := by simp [exp_add] }
theorem exp_list_sum (l : List ℂ) : exp l.sum = (l.map exp).prod :=
map_list_prod (M := Multiplicative ℂ) expMonoidHom l
#align complex.exp_list_sum Complex.exp_list_sum
theorem exp_multiset_sum (s : Multiset ℂ) : exp s.sum = (s.map exp).prod :=
@MonoidHom.map_multiset_prod (Multiplicative ℂ) ℂ _ _ expMonoidHom s
#align complex.exp_multiset_sum Complex.exp_multiset_sum
theorem exp_sum {α : Type*} (s : Finset α) (f : α → ℂ) :
exp (∑ x ∈ s, f x) = ∏ x ∈ s, exp (f x) :=
map_prod (β := Multiplicative ℂ) expMonoidHom f s
#align complex.exp_sum Complex.exp_sum
lemma exp_nsmul (x : ℂ) (n : ℕ) : exp (n • x) = exp x ^ n :=
@MonoidHom.map_pow (Multiplicative ℂ) ℂ _ _ expMonoidHom _ _
theorem exp_nat_mul (x : ℂ) : ∀ n : ℕ, exp (n * x) = exp x ^ n
| 0 => by rw [Nat.cast_zero, zero_mul, exp_zero, pow_zero]
| Nat.succ n => by rw [pow_succ, Nat.cast_add_one, add_mul, exp_add, ← exp_nat_mul _ n, one_mul]
#align complex.exp_nat_mul Complex.exp_nat_mul
theorem exp_ne_zero : exp x ≠ 0 := fun h =>
zero_ne_one <| by rw [← exp_zero, ← add_neg_self x, exp_add, h]; simp
#align complex.exp_ne_zero Complex.exp_ne_zero
theorem exp_neg : exp (-x) = (exp x)⁻¹ := by
rw [← mul_right_inj' (exp_ne_zero x), ← exp_add]; simp [mul_inv_cancel (exp_ne_zero x)]
#align complex.exp_neg Complex.exp_neg
theorem exp_sub : exp (x - y) = exp x / exp y := by
simp [sub_eq_add_neg, exp_add, exp_neg, div_eq_mul_inv]
#align complex.exp_sub Complex.exp_sub
theorem exp_int_mul (z : ℂ) (n : ℤ) : Complex.exp (n * z) = Complex.exp z ^ n := by
cases n
· simp [exp_nat_mul]
· simp [exp_add, add_mul, pow_add, exp_neg, exp_nat_mul]
#align complex.exp_int_mul Complex.exp_int_mul
@[simp]
theorem exp_conj : exp (conj x) = conj (exp x) := by
dsimp [exp]
rw [← lim_conj]
refine congr_arg CauSeq.lim (CauSeq.ext fun _ => ?_)
dsimp [exp', Function.comp_def, cauSeqConj]
rw [map_sum (starRingEnd _)]
refine sum_congr rfl fun n _ => ?_
rw [map_div₀, map_pow, ← ofReal_natCast, conj_ofReal]
#align complex.exp_conj Complex.exp_conj
@[simp]
theorem ofReal_exp_ofReal_re (x : ℝ) : ((exp x).re : ℂ) = exp x :=
conj_eq_iff_re.1 <| by rw [← exp_conj, conj_ofReal]
#align complex.of_real_exp_of_real_re Complex.ofReal_exp_ofReal_re
@[simp, norm_cast]
theorem ofReal_exp (x : ℝ) : (Real.exp x : ℂ) = exp x :=
ofReal_exp_ofReal_re _
#align complex.of_real_exp Complex.ofReal_exp
@[simp]
theorem exp_ofReal_im (x : ℝ) : (exp x).im = 0 := by rw [← ofReal_exp_ofReal_re, ofReal_im]
#align complex.exp_of_real_im Complex.exp_ofReal_im
theorem exp_ofReal_re (x : ℝ) : (exp x).re = Real.exp x :=
rfl
#align complex.exp_of_real_re Complex.exp_ofReal_re
theorem two_sinh : 2 * sinh x = exp x - exp (-x) :=
mul_div_cancel₀ _ two_ne_zero
#align complex.two_sinh Complex.two_sinh
theorem two_cosh : 2 * cosh x = exp x + exp (-x) :=
mul_div_cancel₀ _ two_ne_zero
#align complex.two_cosh Complex.two_cosh
@[simp]
theorem sinh_zero : sinh 0 = 0 := by simp [sinh]
#align complex.sinh_zero Complex.sinh_zero
@[simp]
theorem sinh_neg : sinh (-x) = -sinh x := by simp [sinh, exp_neg, (neg_div _ _).symm, add_mul]
#align complex.sinh_neg Complex.sinh_neg
private theorem sinh_add_aux {a b c d : ℂ} :
(a - b) * (c + d) + (a + b) * (c - d) = 2 * (a * c - b * d) := by ring
theorem sinh_add : sinh (x + y) = sinh x * cosh y + cosh x * sinh y := by
rw [← mul_right_inj' (two_ne_zero' ℂ), two_sinh, exp_add, neg_add, exp_add, eq_comm, mul_add, ←
mul_assoc, two_sinh, mul_left_comm, two_sinh, ← mul_right_inj' (two_ne_zero' ℂ), mul_add,
mul_left_comm, two_cosh, ← mul_assoc, two_cosh]
exact sinh_add_aux
#align complex.sinh_add Complex.sinh_add
@[simp]
theorem cosh_zero : cosh 0 = 1 := by simp [cosh]
#align complex.cosh_zero Complex.cosh_zero
@[simp]
theorem cosh_neg : cosh (-x) = cosh x := by simp [add_comm, cosh, exp_neg]
#align complex.cosh_neg Complex.cosh_neg
private theorem cosh_add_aux {a b c d : ℂ} :
(a + b) * (c + d) + (a - b) * (c - d) = 2 * (a * c + b * d) := by ring
theorem cosh_add : cosh (x + y) = cosh x * cosh y + sinh x * sinh y := by
rw [← mul_right_inj' (two_ne_zero' ℂ), two_cosh, exp_add, neg_add, exp_add, eq_comm, mul_add, ←
mul_assoc, two_cosh, ← mul_assoc, two_sinh, ← mul_right_inj' (two_ne_zero' ℂ), mul_add,
mul_left_comm, two_cosh, mul_left_comm, two_sinh]
exact cosh_add_aux
#align complex.cosh_add Complex.cosh_add
theorem sinh_sub : sinh (x - y) = sinh x * cosh y - cosh x * sinh y := by
simp [sub_eq_add_neg, sinh_add, sinh_neg, cosh_neg]
#align complex.sinh_sub Complex.sinh_sub
theorem cosh_sub : cosh (x - y) = cosh x * cosh y - sinh x * sinh y := by
simp [sub_eq_add_neg, cosh_add, sinh_neg, cosh_neg]
#align complex.cosh_sub Complex.cosh_sub
theorem sinh_conj : sinh (conj x) = conj (sinh x) := by
rw [sinh, ← RingHom.map_neg, exp_conj, exp_conj, ← RingHom.map_sub, sinh, map_div₀]
-- Porting note: not nice
simp [← one_add_one_eq_two]
#align complex.sinh_conj Complex.sinh_conj
@[simp]
theorem ofReal_sinh_ofReal_re (x : ℝ) : ((sinh x).re : ℂ) = sinh x :=
conj_eq_iff_re.1 <| by rw [← sinh_conj, conj_ofReal]
#align complex.of_real_sinh_of_real_re Complex.ofReal_sinh_ofReal_re
@[simp, norm_cast]
theorem ofReal_sinh (x : ℝ) : (Real.sinh x : ℂ) = sinh x :=
ofReal_sinh_ofReal_re _
#align complex.of_real_sinh Complex.ofReal_sinh
@[simp]
theorem sinh_ofReal_im (x : ℝ) : (sinh x).im = 0 := by rw [← ofReal_sinh_ofReal_re, ofReal_im]
#align complex.sinh_of_real_im Complex.sinh_ofReal_im
theorem sinh_ofReal_re (x : ℝ) : (sinh x).re = Real.sinh x :=
rfl
#align complex.sinh_of_real_re Complex.sinh_ofReal_re
theorem cosh_conj : cosh (conj x) = conj (cosh x) := by
rw [cosh, ← RingHom.map_neg, exp_conj, exp_conj, ← RingHom.map_add, cosh, map_div₀]
-- Porting note: not nice
simp [← one_add_one_eq_two]
#align complex.cosh_conj Complex.cosh_conj
theorem ofReal_cosh_ofReal_re (x : ℝ) : ((cosh x).re : ℂ) = cosh x :=
conj_eq_iff_re.1 <| by rw [← cosh_conj, conj_ofReal]
#align complex.of_real_cosh_of_real_re Complex.ofReal_cosh_ofReal_re
@[simp, norm_cast]
theorem ofReal_cosh (x : ℝ) : (Real.cosh x : ℂ) = cosh x :=
ofReal_cosh_ofReal_re _
#align complex.of_real_cosh Complex.ofReal_cosh
@[simp]
theorem cosh_ofReal_im (x : ℝ) : (cosh x).im = 0 := by rw [← ofReal_cosh_ofReal_re, ofReal_im]
#align complex.cosh_of_real_im Complex.cosh_ofReal_im
@[simp]
theorem cosh_ofReal_re (x : ℝ) : (cosh x).re = Real.cosh x :=
rfl
#align complex.cosh_of_real_re Complex.cosh_ofReal_re
theorem tanh_eq_sinh_div_cosh : tanh x = sinh x / cosh x :=
rfl
#align complex.tanh_eq_sinh_div_cosh Complex.tanh_eq_sinh_div_cosh
@[simp]
theorem tanh_zero : tanh 0 = 0 := by simp [tanh]
#align complex.tanh_zero Complex.tanh_zero
@[simp]
theorem tanh_neg : tanh (-x) = -tanh x := by simp [tanh, neg_div]
#align complex.tanh_neg Complex.tanh_neg
theorem tanh_conj : tanh (conj x) = conj (tanh x) := by
rw [tanh, sinh_conj, cosh_conj, ← map_div₀, tanh]
#align complex.tanh_conj Complex.tanh_conj
@[simp]
theorem ofReal_tanh_ofReal_re (x : ℝ) : ((tanh x).re : ℂ) = tanh x :=
conj_eq_iff_re.1 <| by rw [← tanh_conj, conj_ofReal]
#align complex.of_real_tanh_of_real_re Complex.ofReal_tanh_ofReal_re
@[simp, norm_cast]
theorem ofReal_tanh (x : ℝ) : (Real.tanh x : ℂ) = tanh x :=
ofReal_tanh_ofReal_re _
#align complex.of_real_tanh Complex.ofReal_tanh
@[simp]
theorem tanh_ofReal_im (x : ℝ) : (tanh x).im = 0 := by rw [← ofReal_tanh_ofReal_re, ofReal_im]
#align complex.tanh_of_real_im Complex.tanh_ofReal_im
theorem tanh_ofReal_re (x : ℝ) : (tanh x).re = Real.tanh x :=
rfl
#align complex.tanh_of_real_re Complex.tanh_ofReal_re
@[simp]
theorem cosh_add_sinh : cosh x + sinh x = exp x := by
rw [← mul_right_inj' (two_ne_zero' ℂ), mul_add, two_cosh, two_sinh, add_add_sub_cancel, two_mul]
#align complex.cosh_add_sinh Complex.cosh_add_sinh
@[simp]
theorem sinh_add_cosh : sinh x + cosh x = exp x := by rw [add_comm, cosh_add_sinh]
#align complex.sinh_add_cosh Complex.sinh_add_cosh
@[simp]
theorem exp_sub_cosh : exp x - cosh x = sinh x :=
sub_eq_iff_eq_add.2 (sinh_add_cosh x).symm
#align complex.exp_sub_cosh Complex.exp_sub_cosh
@[simp]
theorem exp_sub_sinh : exp x - sinh x = cosh x :=
sub_eq_iff_eq_add.2 (cosh_add_sinh x).symm
#align complex.exp_sub_sinh Complex.exp_sub_sinh
@[simp]
theorem cosh_sub_sinh : cosh x - sinh x = exp (-x) := by
rw [← mul_right_inj' (two_ne_zero' ℂ), mul_sub, two_cosh, two_sinh, add_sub_sub_cancel, two_mul]
#align complex.cosh_sub_sinh Complex.cosh_sub_sinh
@[simp]
theorem sinh_sub_cosh : sinh x - cosh x = -exp (-x) := by rw [← neg_sub, cosh_sub_sinh]
#align complex.sinh_sub_cosh Complex.sinh_sub_cosh
@[simp]
theorem cosh_sq_sub_sinh_sq : cosh x ^ 2 - sinh x ^ 2 = 1 := by
rw [sq_sub_sq, cosh_add_sinh, cosh_sub_sinh, ← exp_add, add_neg_self, exp_zero]
#align complex.cosh_sq_sub_sinh_sq Complex.cosh_sq_sub_sinh_sq
theorem cosh_sq : cosh x ^ 2 = sinh x ^ 2 + 1 := by
rw [← cosh_sq_sub_sinh_sq x]
ring
#align complex.cosh_sq Complex.cosh_sq
theorem sinh_sq : sinh x ^ 2 = cosh x ^ 2 - 1 := by
rw [← cosh_sq_sub_sinh_sq x]
ring
#align complex.sinh_sq Complex.sinh_sq
theorem cosh_two_mul : cosh (2 * x) = cosh x ^ 2 + sinh x ^ 2 := by rw [two_mul, cosh_add, sq, sq]
#align complex.cosh_two_mul Complex.cosh_two_mul
theorem sinh_two_mul : sinh (2 * x) = 2 * sinh x * cosh x := by
rw [two_mul, sinh_add]
ring
#align complex.sinh_two_mul Complex.sinh_two_mul
theorem cosh_three_mul : cosh (3 * x) = 4 * cosh x ^ 3 - 3 * cosh x := by
have h1 : x + 2 * x = 3 * x := by ring
rw [← h1, cosh_add x (2 * x)]
simp only [cosh_two_mul, sinh_two_mul]
have h2 : sinh x * (2 * sinh x * cosh x) = 2 * cosh x * sinh x ^ 2 := by ring
rw [h2, sinh_sq]
ring
#align complex.cosh_three_mul Complex.cosh_three_mul
theorem sinh_three_mul : sinh (3 * x) = 4 * sinh x ^ 3 + 3 * sinh x := by
have h1 : x + 2 * x = 3 * x := by ring
rw [← h1, sinh_add x (2 * x)]
simp only [cosh_two_mul, sinh_two_mul]
have h2 : cosh x * (2 * sinh x * cosh x) = 2 * sinh x * cosh x ^ 2 := by ring
rw [h2, cosh_sq]
ring
#align complex.sinh_three_mul Complex.sinh_three_mul
@[simp]
theorem sin_zero : sin 0 = 0 := by simp [sin]
#align complex.sin_zero Complex.sin_zero
@[simp]
theorem sin_neg : sin (-x) = -sin x := by
simp [sin, sub_eq_add_neg, exp_neg, (neg_div _ _).symm, add_mul]
#align complex.sin_neg Complex.sin_neg
theorem two_sin : 2 * sin x = (exp (-x * I) - exp (x * I)) * I :=
mul_div_cancel₀ _ two_ne_zero
#align complex.two_sin Complex.two_sin
theorem two_cos : 2 * cos x = exp (x * I) + exp (-x * I) :=
mul_div_cancel₀ _ two_ne_zero
#align complex.two_cos Complex.two_cos
theorem sinh_mul_I : sinh (x * I) = sin x * I := by
rw [← mul_right_inj' (two_ne_zero' ℂ), two_sinh, ← mul_assoc, two_sin, mul_assoc, I_mul_I,
mul_neg_one, neg_sub, neg_mul_eq_neg_mul]
set_option linter.uppercaseLean3 false in
#align complex.sinh_mul_I Complex.sinh_mul_I
theorem cosh_mul_I : cosh (x * I) = cos x := by
rw [← mul_right_inj' (two_ne_zero' ℂ), two_cosh, two_cos, neg_mul_eq_neg_mul]
set_option linter.uppercaseLean3 false in
#align complex.cosh_mul_I Complex.cosh_mul_I
theorem tanh_mul_I : tanh (x * I) = tan x * I := by
rw [tanh_eq_sinh_div_cosh, cosh_mul_I, sinh_mul_I, mul_div_right_comm, tan]
set_option linter.uppercaseLean3 false in
#align complex.tanh_mul_I Complex.tanh_mul_I
theorem cos_mul_I : cos (x * I) = cosh x := by rw [← cosh_mul_I]; ring_nf; simp
set_option linter.uppercaseLean3 false in
#align complex.cos_mul_I Complex.cos_mul_I
theorem sin_mul_I : sin (x * I) = sinh x * I := by
have h : I * sin (x * I) = -sinh x := by
rw [mul_comm, ← sinh_mul_I]
ring_nf
simp
rw [← neg_neg (sinh x), ← h]
apply Complex.ext <;> simp
set_option linter.uppercaseLean3 false in
#align complex.sin_mul_I Complex.sin_mul_I
theorem tan_mul_I : tan (x * I) = tanh x * I := by
rw [tan, sin_mul_I, cos_mul_I, mul_div_right_comm, tanh_eq_sinh_div_cosh]
set_option linter.uppercaseLean3 false in
#align complex.tan_mul_I Complex.tan_mul_I
theorem sin_add : sin (x + y) = sin x * cos y + cos x * sin y := by
rw [← mul_left_inj' I_ne_zero, ← sinh_mul_I, add_mul, add_mul, mul_right_comm, ← sinh_mul_I,
mul_assoc, ← sinh_mul_I, ← cosh_mul_I, ← cosh_mul_I, sinh_add]
#align complex.sin_add Complex.sin_add
@[simp]
theorem cos_zero : cos 0 = 1 := by simp [cos]
#align complex.cos_zero Complex.cos_zero
@[simp]
theorem cos_neg : cos (-x) = cos x := by simp [cos, sub_eq_add_neg, exp_neg, add_comm]
#align complex.cos_neg Complex.cos_neg
private theorem cos_add_aux {a b c d : ℂ} :
(a + b) * (c + d) - (b - a) * (d - c) * -1 = 2 * (a * c + b * d) := by ring
theorem cos_add : cos (x + y) = cos x * cos y - sin x * sin y := by
rw [← cosh_mul_I, add_mul, cosh_add, cosh_mul_I, cosh_mul_I, sinh_mul_I, sinh_mul_I,
mul_mul_mul_comm, I_mul_I, mul_neg_one, sub_eq_add_neg]
#align complex.cos_add Complex.cos_add
theorem sin_sub : sin (x - y) = sin x * cos y - cos x * sin y := by
simp [sub_eq_add_neg, sin_add, sin_neg, cos_neg]
#align complex.sin_sub Complex.sin_sub
theorem cos_sub : cos (x - y) = cos x * cos y + sin x * sin y := by
simp [sub_eq_add_neg, cos_add, sin_neg, cos_neg]
#align complex.cos_sub Complex.cos_sub
theorem sin_add_mul_I (x y : ℂ) : sin (x + y * I) = sin x * cosh y + cos x * sinh y * I := by
rw [sin_add, cos_mul_I, sin_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.sin_add_mul_I Complex.sin_add_mul_I
theorem sin_eq (z : ℂ) : sin z = sin z.re * cosh z.im + cos z.re * sinh z.im * I := by
convert sin_add_mul_I z.re z.im; exact (re_add_im z).symm
#align complex.sin_eq Complex.sin_eq
theorem cos_add_mul_I (x y : ℂ) : cos (x + y * I) = cos x * cosh y - sin x * sinh y * I := by
rw [cos_add, cos_mul_I, sin_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.cos_add_mul_I Complex.cos_add_mul_I
theorem cos_eq (z : ℂ) : cos z = cos z.re * cosh z.im - sin z.re * sinh z.im * I := by
convert cos_add_mul_I z.re z.im; exact (re_add_im z).symm
#align complex.cos_eq Complex.cos_eq
theorem sin_sub_sin : sin x - sin y = 2 * sin ((x - y) / 2) * cos ((x + y) / 2) := by
have s1 := sin_add ((x + y) / 2) ((x - y) / 2)
have s2 := sin_sub ((x + y) / 2) ((x - y) / 2)
rw [div_add_div_same, add_sub, add_right_comm, add_sub_cancel_right, half_add_self] at s1
rw [div_sub_div_same, ← sub_add, add_sub_cancel_left, half_add_self] at s2
rw [s1, s2]
ring
#align complex.sin_sub_sin Complex.sin_sub_sin
theorem cos_sub_cos : cos x - cos y = -2 * sin ((x + y) / 2) * sin ((x - y) / 2) := by
have s1 := cos_add ((x + y) / 2) ((x - y) / 2)
have s2 := cos_sub ((x + y) / 2) ((x - y) / 2)
rw [div_add_div_same, add_sub, add_right_comm, add_sub_cancel_right, half_add_self] at s1
rw [div_sub_div_same, ← sub_add, add_sub_cancel_left, half_add_self] at s2
rw [s1, s2]
ring
#align complex.cos_sub_cos Complex.cos_sub_cos
theorem sin_add_sin : sin x + sin y = 2 * sin ((x + y) / 2) * cos ((x - y) / 2) := by
simpa using sin_sub_sin x (-y)
theorem cos_add_cos : cos x + cos y = 2 * cos ((x + y) / 2) * cos ((x - y) / 2) := by
calc
cos x + cos y = cos ((x + y) / 2 + (x - y) / 2) + cos ((x + y) / 2 - (x - y) / 2) := ?_
_ =
cos ((x + y) / 2) * cos ((x - y) / 2) - sin ((x + y) / 2) * sin ((x - y) / 2) +
(cos ((x + y) / 2) * cos ((x - y) / 2) + sin ((x + y) / 2) * sin ((x - y) / 2)) :=
?_
_ = 2 * cos ((x + y) / 2) * cos ((x - y) / 2) := ?_
· congr <;> field_simp
· rw [cos_add, cos_sub]
ring
#align complex.cos_add_cos Complex.cos_add_cos
theorem sin_conj : sin (conj x) = conj (sin x) := by
rw [← mul_left_inj' I_ne_zero, ← sinh_mul_I, ← conj_neg_I, ← RingHom.map_mul, ← RingHom.map_mul,
sinh_conj, mul_neg, sinh_neg, sinh_mul_I, mul_neg]
#align complex.sin_conj Complex.sin_conj
@[simp]
theorem ofReal_sin_ofReal_re (x : ℝ) : ((sin x).re : ℂ) = sin x :=
conj_eq_iff_re.1 <| by rw [← sin_conj, conj_ofReal]
#align complex.of_real_sin_of_real_re Complex.ofReal_sin_ofReal_re
@[simp, norm_cast]
theorem ofReal_sin (x : ℝ) : (Real.sin x : ℂ) = sin x :=
ofReal_sin_ofReal_re _
#align complex.of_real_sin Complex.ofReal_sin
@[simp]
theorem sin_ofReal_im (x : ℝ) : (sin x).im = 0 := by rw [← ofReal_sin_ofReal_re, ofReal_im]
#align complex.sin_of_real_im Complex.sin_ofReal_im
theorem sin_ofReal_re (x : ℝ) : (sin x).re = Real.sin x :=
rfl
#align complex.sin_of_real_re Complex.sin_ofReal_re
theorem cos_conj : cos (conj x) = conj (cos x) := by
rw [← cosh_mul_I, ← conj_neg_I, ← RingHom.map_mul, ← cosh_mul_I, cosh_conj, mul_neg, cosh_neg]
#align complex.cos_conj Complex.cos_conj
@[simp]
theorem ofReal_cos_ofReal_re (x : ℝ) : ((cos x).re : ℂ) = cos x :=
conj_eq_iff_re.1 <| by rw [← cos_conj, conj_ofReal]
#align complex.of_real_cos_of_real_re Complex.ofReal_cos_ofReal_re
@[simp, norm_cast]
theorem ofReal_cos (x : ℝ) : (Real.cos x : ℂ) = cos x :=
ofReal_cos_ofReal_re _
#align complex.of_real_cos Complex.ofReal_cos
@[simp]
theorem cos_ofReal_im (x : ℝ) : (cos x).im = 0 := by rw [← ofReal_cos_ofReal_re, ofReal_im]
#align complex.cos_of_real_im Complex.cos_ofReal_im
theorem cos_ofReal_re (x : ℝ) : (cos x).re = Real.cos x :=
rfl
#align complex.cos_of_real_re Complex.cos_ofReal_re
@[simp]
theorem tan_zero : tan 0 = 0 := by simp [tan]
#align complex.tan_zero Complex.tan_zero
theorem tan_eq_sin_div_cos : tan x = sin x / cos x :=
rfl
#align complex.tan_eq_sin_div_cos Complex.tan_eq_sin_div_cos
theorem tan_mul_cos {x : ℂ} (hx : cos x ≠ 0) : tan x * cos x = sin x := by
rw [tan_eq_sin_div_cos, div_mul_cancel₀ _ hx]
#align complex.tan_mul_cos Complex.tan_mul_cos
@[simp]
theorem tan_neg : tan (-x) = -tan x := by simp [tan, neg_div]
#align complex.tan_neg Complex.tan_neg
theorem tan_conj : tan (conj x) = conj (tan x) := by rw [tan, sin_conj, cos_conj, ← map_div₀, tan]
#align complex.tan_conj Complex.tan_conj
@[simp]
theorem ofReal_tan_ofReal_re (x : ℝ) : ((tan x).re : ℂ) = tan x :=
conj_eq_iff_re.1 <| by rw [← tan_conj, conj_ofReal]
#align complex.of_real_tan_of_real_re Complex.ofReal_tan_ofReal_re
@[simp, norm_cast]
theorem ofReal_tan (x : ℝ) : (Real.tan x : ℂ) = tan x :=
ofReal_tan_ofReal_re _
#align complex.of_real_tan Complex.ofReal_tan
@[simp]
theorem tan_ofReal_im (x : ℝ) : (tan x).im = 0 := by rw [← ofReal_tan_ofReal_re, ofReal_im]
#align complex.tan_of_real_im Complex.tan_ofReal_im
theorem tan_ofReal_re (x : ℝ) : (tan x).re = Real.tan x :=
rfl
#align complex.tan_of_real_re Complex.tan_ofReal_re
theorem cos_add_sin_I : cos x + sin x * I = exp (x * I) := by
rw [← cosh_add_sinh, sinh_mul_I, cosh_mul_I]
set_option linter.uppercaseLean3 false in
#align complex.cos_add_sin_I Complex.cos_add_sin_I
theorem cos_sub_sin_I : cos x - sin x * I = exp (-x * I) := by
rw [neg_mul, ← cosh_sub_sinh, sinh_mul_I, cosh_mul_I]
set_option linter.uppercaseLean3 false in
#align complex.cos_sub_sin_I Complex.cos_sub_sin_I
@[simp]
theorem sin_sq_add_cos_sq : sin x ^ 2 + cos x ^ 2 = 1 :=
Eq.trans (by rw [cosh_mul_I, sinh_mul_I, mul_pow, I_sq, mul_neg_one, sub_neg_eq_add, add_comm])
(cosh_sq_sub_sinh_sq (x * I))
#align complex.sin_sq_add_cos_sq Complex.sin_sq_add_cos_sq
@[simp]
theorem cos_sq_add_sin_sq : cos x ^ 2 + sin x ^ 2 = 1 := by rw [add_comm, sin_sq_add_cos_sq]
#align complex.cos_sq_add_sin_sq Complex.cos_sq_add_sin_sq
theorem cos_two_mul' : cos (2 * x) = cos x ^ 2 - sin x ^ 2 := by rw [two_mul, cos_add, ← sq, ← sq]
#align complex.cos_two_mul' Complex.cos_two_mul'
theorem cos_two_mul : cos (2 * x) = 2 * cos x ^ 2 - 1 := by
rw [cos_two_mul', eq_sub_iff_add_eq.2 (sin_sq_add_cos_sq x), ← sub_add, sub_add_eq_add_sub,
two_mul]
#align complex.cos_two_mul Complex.cos_two_mul
theorem sin_two_mul : sin (2 * x) = 2 * sin x * cos x := by
rw [two_mul, sin_add, two_mul, add_mul, mul_comm]
#align complex.sin_two_mul Complex.sin_two_mul
theorem cos_sq : cos x ^ 2 = 1 / 2 + cos (2 * x) / 2 := by
simp [cos_two_mul, div_add_div_same, mul_div_cancel_left₀, two_ne_zero, -one_div]
#align complex.cos_sq Complex.cos_sq
theorem cos_sq' : cos x ^ 2 = 1 - sin x ^ 2 := by rw [← sin_sq_add_cos_sq x, add_sub_cancel_left]
#align complex.cos_sq' Complex.cos_sq'
theorem sin_sq : sin x ^ 2 = 1 - cos x ^ 2 := by rw [← sin_sq_add_cos_sq x, add_sub_cancel_right]
#align complex.sin_sq Complex.sin_sq
theorem inv_one_add_tan_sq {x : ℂ} (hx : cos x ≠ 0) : (1 + tan x ^ 2)⁻¹ = cos x ^ 2 := by
rw [tan_eq_sin_div_cos, div_pow]
field_simp
#align complex.inv_one_add_tan_sq Complex.inv_one_add_tan_sq
theorem tan_sq_div_one_add_tan_sq {x : ℂ} (hx : cos x ≠ 0) :
tan x ^ 2 / (1 + tan x ^ 2) = sin x ^ 2 := by
simp only [← tan_mul_cos hx, mul_pow, ← inv_one_add_tan_sq hx, div_eq_mul_inv, one_mul]
#align complex.tan_sq_div_one_add_tan_sq Complex.tan_sq_div_one_add_tan_sq
theorem cos_three_mul : cos (3 * x) = 4 * cos x ^ 3 - 3 * cos x := by
have h1 : x + 2 * x = 3 * x := by ring
rw [← h1, cos_add x (2 * x)]
simp only [cos_two_mul, sin_two_mul, mul_add, mul_sub, mul_one, sq]
have h2 : 4 * cos x ^ 3 = 2 * cos x * cos x * cos x + 2 * cos x * cos x ^ 2 := by ring
rw [h2, cos_sq']
ring
#align complex.cos_three_mul Complex.cos_three_mul
theorem sin_three_mul : sin (3 * x) = 3 * sin x - 4 * sin x ^ 3 := by
have h1 : x + 2 * x = 3 * x := by ring
rw [← h1, sin_add x (2 * x)]
simp only [cos_two_mul, sin_two_mul, cos_sq']
have h2 : cos x * (2 * sin x * cos x) = 2 * sin x * cos x ^ 2 := by ring
rw [h2, cos_sq']
ring
#align complex.sin_three_mul Complex.sin_three_mul
theorem exp_mul_I : exp (x * I) = cos x + sin x * I :=
(cos_add_sin_I _).symm
set_option linter.uppercaseLean3 false in
#align complex.exp_mul_I Complex.exp_mul_I
theorem exp_add_mul_I : exp (x + y * I) = exp x * (cos y + sin y * I) := by rw [exp_add, exp_mul_I]
set_option linter.uppercaseLean3 false in
#align complex.exp_add_mul_I Complex.exp_add_mul_I
theorem exp_eq_exp_re_mul_sin_add_cos : exp x = exp x.re * (cos x.im + sin x.im * I) := by
rw [← exp_add_mul_I, re_add_im]
#align complex.exp_eq_exp_re_mul_sin_add_cos Complex.exp_eq_exp_re_mul_sin_add_cos
theorem exp_re : (exp x).re = Real.exp x.re * Real.cos x.im := by
rw [exp_eq_exp_re_mul_sin_add_cos]
simp [exp_ofReal_re, cos_ofReal_re]
#align complex.exp_re Complex.exp_re
theorem exp_im : (exp x).im = Real.exp x.re * Real.sin x.im := by
rw [exp_eq_exp_re_mul_sin_add_cos]
simp [exp_ofReal_re, sin_ofReal_re]
#align complex.exp_im Complex.exp_im
@[simp]
theorem exp_ofReal_mul_I_re (x : ℝ) : (exp (x * I)).re = Real.cos x := by
simp [exp_mul_I, cos_ofReal_re]
set_option linter.uppercaseLean3 false in
#align complex.exp_of_real_mul_I_re Complex.exp_ofReal_mul_I_re
@[simp]
theorem exp_ofReal_mul_I_im (x : ℝ) : (exp (x * I)).im = Real.sin x := by
simp [exp_mul_I, sin_ofReal_re]
set_option linter.uppercaseLean3 false in
#align complex.exp_of_real_mul_I_im Complex.exp_ofReal_mul_I_im
/-- **De Moivre's formula** -/
theorem cos_add_sin_mul_I_pow (n : ℕ) (z : ℂ) :
(cos z + sin z * I) ^ n = cos (↑n * z) + sin (↑n * z) * I := by
rw [← exp_mul_I, ← exp_mul_I]
induction' n with n ih
· rw [pow_zero, Nat.cast_zero, zero_mul, zero_mul, exp_zero]
· rw [pow_succ, ih, Nat.cast_succ, add_mul, add_mul, one_mul, exp_add]
set_option linter.uppercaseLean3 false in
#align complex.cos_add_sin_mul_I_pow Complex.cos_add_sin_mul_I_pow
end Complex
namespace Real
open Complex
variable (x y : ℝ)
@[simp]
theorem exp_zero : exp 0 = 1 := by simp [Real.exp]
#align real.exp_zero Real.exp_zero
nonrec theorem exp_add : exp (x + y) = exp x * exp y := by simp [exp_add, exp]
#align real.exp_add Real.exp_add
-- Porting note (#11445): new definition
/-- the exponential function as a monoid hom from `Multiplicative ℝ` to `ℝ` -/
noncomputable def expMonoidHom : MonoidHom (Multiplicative ℝ) ℝ :=
{ toFun := fun x => exp (Multiplicative.toAdd x),
map_one' := by simp,
map_mul' := by simp [exp_add] }
theorem exp_list_sum (l : List ℝ) : exp l.sum = (l.map exp).prod :=
map_list_prod (M := Multiplicative ℝ) expMonoidHom l
#align real.exp_list_sum Real.exp_list_sum
theorem exp_multiset_sum (s : Multiset ℝ) : exp s.sum = (s.map exp).prod :=
@MonoidHom.map_multiset_prod (Multiplicative ℝ) ℝ _ _ expMonoidHom s
#align real.exp_multiset_sum Real.exp_multiset_sum
theorem exp_sum {α : Type*} (s : Finset α) (f : α → ℝ) :
exp (∑ x ∈ s, f x) = ∏ x ∈ s, exp (f x) :=
map_prod (β := Multiplicative ℝ) expMonoidHom f s
#align real.exp_sum Real.exp_sum
lemma exp_nsmul (x : ℝ) (n : ℕ) : exp (n • x) = exp x ^ n :=
@MonoidHom.map_pow (Multiplicative ℝ) ℝ _ _ expMonoidHom _ _
nonrec theorem exp_nat_mul (x : ℝ) (n : ℕ) : exp (n * x) = exp x ^ n :=
ofReal_injective (by simp [exp_nat_mul])
#align real.exp_nat_mul Real.exp_nat_mul
nonrec theorem exp_ne_zero : exp x ≠ 0 := fun h =>
exp_ne_zero x <| by rw [exp, ← ofReal_inj] at h; simp_all
#align real.exp_ne_zero Real.exp_ne_zero
nonrec theorem exp_neg : exp (-x) = (exp x)⁻¹ :=
ofReal_injective <| by simp [exp_neg]
#align real.exp_neg Real.exp_neg
theorem exp_sub : exp (x - y) = exp x / exp y := by
simp [sub_eq_add_neg, exp_add, exp_neg, div_eq_mul_inv]
#align real.exp_sub Real.exp_sub
@[simp]
theorem sin_zero : sin 0 = 0 := by simp [sin]
#align real.sin_zero Real.sin_zero
@[simp]
theorem sin_neg : sin (-x) = -sin x := by simp [sin, exp_neg, (neg_div _ _).symm, add_mul]
#align real.sin_neg Real.sin_neg
nonrec theorem sin_add : sin (x + y) = sin x * cos y + cos x * sin y :=
ofReal_injective <| by simp [sin_add]
#align real.sin_add Real.sin_add
@[simp]
theorem cos_zero : cos 0 = 1 := by simp [cos]
#align real.cos_zero Real.cos_zero
@[simp]
theorem cos_neg : cos (-x) = cos x := by simp [cos, exp_neg]
#align real.cos_neg Real.cos_neg
@[simp]
theorem cos_abs : cos |x| = cos x := by
cases le_total x 0 <;> simp only [*, _root_.abs_of_nonneg, abs_of_nonpos, cos_neg]
#align real.cos_abs Real.cos_abs
nonrec theorem cos_add : cos (x + y) = cos x * cos y - sin x * sin y :=
ofReal_injective <| by simp [cos_add]
#align real.cos_add Real.cos_add
theorem sin_sub : sin (x - y) = sin x * cos y - cos x * sin y := by
simp [sub_eq_add_neg, sin_add, sin_neg, cos_neg]
#align real.sin_sub Real.sin_sub
theorem cos_sub : cos (x - y) = cos x * cos y + sin x * sin y := by
simp [sub_eq_add_neg, cos_add, sin_neg, cos_neg]
#align real.cos_sub Real.cos_sub
nonrec theorem sin_sub_sin : sin x - sin y = 2 * sin ((x - y) / 2) * cos ((x + y) / 2) :=
ofReal_injective <| by simp [sin_sub_sin]
#align real.sin_sub_sin Real.sin_sub_sin
nonrec theorem cos_sub_cos : cos x - cos y = -2 * sin ((x + y) / 2) * sin ((x - y) / 2) :=
ofReal_injective <| by simp [cos_sub_cos]
#align real.cos_sub_cos Real.cos_sub_cos
nonrec theorem cos_add_cos : cos x + cos y = 2 * cos ((x + y) / 2) * cos ((x - y) / 2) :=
ofReal_injective <| by simp [cos_add_cos]
#align real.cos_add_cos Real.cos_add_cos
nonrec theorem tan_eq_sin_div_cos : tan x = sin x / cos x :=
ofReal_injective <| by simp [tan_eq_sin_div_cos]
#align real.tan_eq_sin_div_cos Real.tan_eq_sin_div_cos
theorem tan_mul_cos {x : ℝ} (hx : cos x ≠ 0) : tan x * cos x = sin x := by
rw [tan_eq_sin_div_cos, div_mul_cancel₀ _ hx]
#align real.tan_mul_cos Real.tan_mul_cos
@[simp]
theorem tan_zero : tan 0 = 0 := by simp [tan]
#align real.tan_zero Real.tan_zero
@[simp]
| Mathlib/Data/Complex/Exponential.lean | 931 | 931 | theorem tan_neg : tan (-x) = -tan x := by | simp [tan, neg_div]
|
/-
Copyright (c) 2020 Frédéric Dupuis. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Frédéric Dupuis
-/
import Mathlib.Data.Real.Sqrt
import Mathlib.Analysis.NormedSpace.Star.Basic
import Mathlib.Analysis.NormedSpace.ContinuousLinearMap
import Mathlib.Analysis.NormedSpace.Basic
#align_import data.is_R_or_C.basic from "leanprover-community/mathlib"@"baa88307f3e699fa7054ef04ec79fa4f056169cb"
/-!
# `RCLike`: a typeclass for ℝ or ℂ
This file defines the typeclass `RCLike` intended to have only two instances:
ℝ and ℂ. It is meant for definitions and theorems which hold for both the real and the complex case,
and in particular when the real case follows directly from the complex case by setting `re` to `id`,
`im` to zero and so on. Its API follows closely that of ℂ.
Applications include defining inner products and Hilbert spaces for both the real and
complex case. One typically produces the definitions and proof for an arbitrary field of this
typeclass, which basically amounts to doing the complex case, and the two cases then fall out
immediately from the two instances of the class.
The instance for `ℝ` is registered in this file.
The instance for `ℂ` is declared in `Mathlib/Analysis/Complex/Basic.lean`.
## Implementation notes
The coercion from reals into an `RCLike` field is done by registering `RCLike.ofReal` as
a `CoeTC`. For this to work, we must proceed carefully to avoid problems involving circular
coercions in the case `K=ℝ`; in particular, we cannot use the plain `Coe` and must set
priorities carefully. This problem was already solved for `ℕ`, and we copy the solution detailed
in `Mathlib/Data/Nat/Cast/Defs.lean`. See also Note [coercion into rings] for more details.
In addition, several lemmas need to be set at priority 900 to make sure that they do not override
their counterparts in `Mathlib/Analysis/Complex/Basic.lean` (which causes linter errors).
A few lemmas requiring heavier imports are in `Mathlib/Data/RCLike/Lemmas.lean`.
-/
section
local notation "𝓚" => algebraMap ℝ _
open ComplexConjugate
/--
This typeclass captures properties shared by ℝ and ℂ, with an API that closely matches that of ℂ.
-/
class RCLike (K : semiOutParam Type*) extends DenselyNormedField K, StarRing K,
NormedAlgebra ℝ K, CompleteSpace K where
re : K →+ ℝ
im : K →+ ℝ
/-- Imaginary unit in `K`. Meant to be set to `0` for `K = ℝ`. -/
I : K
I_re_ax : re I = 0
I_mul_I_ax : I = 0 ∨ I * I = -1
re_add_im_ax : ∀ z : K, 𝓚 (re z) + 𝓚 (im z) * I = z
ofReal_re_ax : ∀ r : ℝ, re (𝓚 r) = r
ofReal_im_ax : ∀ r : ℝ, im (𝓚 r) = 0
mul_re_ax : ∀ z w : K, re (z * w) = re z * re w - im z * im w
mul_im_ax : ∀ z w : K, im (z * w) = re z * im w + im z * re w
conj_re_ax : ∀ z : K, re (conj z) = re z
conj_im_ax : ∀ z : K, im (conj z) = -im z
conj_I_ax : conj I = -I
norm_sq_eq_def_ax : ∀ z : K, ‖z‖ ^ 2 = re z * re z + im z * im z
mul_im_I_ax : ∀ z : K, im z * im I = im z
/-- only an instance in the `ComplexOrder` locale -/
[toPartialOrder : PartialOrder K]
le_iff_re_im {z w : K} : z ≤ w ↔ re z ≤ re w ∧ im z = im w
-- note we cannot put this in the `extends` clause
[toDecidableEq : DecidableEq K]
#align is_R_or_C RCLike
scoped[ComplexOrder] attribute [instance 100] RCLike.toPartialOrder
attribute [instance 100] RCLike.toDecidableEq
end
variable {K E : Type*} [RCLike K]
namespace RCLike
open ComplexConjugate
/-- Coercion from `ℝ` to an `RCLike` field. -/
@[coe] abbrev ofReal : ℝ → K := Algebra.cast
/- The priority must be set at 900 to ensure that coercions are tried in the right order.
See Note [coercion into rings], or `Mathlib/Data/Nat/Cast/Basic.lean` for more details. -/
noncomputable instance (priority := 900) algebraMapCoe : CoeTC ℝ K :=
⟨ofReal⟩
#align is_R_or_C.algebra_map_coe RCLike.algebraMapCoe
theorem ofReal_alg (x : ℝ) : (x : K) = x • (1 : K) :=
Algebra.algebraMap_eq_smul_one x
#align is_R_or_C.of_real_alg RCLike.ofReal_alg
theorem real_smul_eq_coe_mul (r : ℝ) (z : K) : r • z = (r : K) * z :=
Algebra.smul_def r z
#align is_R_or_C.real_smul_eq_coe_mul RCLike.real_smul_eq_coe_mul
theorem real_smul_eq_coe_smul [AddCommGroup E] [Module K E] [Module ℝ E] [IsScalarTower ℝ K E]
(r : ℝ) (x : E) : r • x = (r : K) • x := by rw [RCLike.ofReal_alg, smul_one_smul]
#align is_R_or_C.real_smul_eq_coe_smul RCLike.real_smul_eq_coe_smul
theorem algebraMap_eq_ofReal : ⇑(algebraMap ℝ K) = ofReal :=
rfl
#align is_R_or_C.algebra_map_eq_of_real RCLike.algebraMap_eq_ofReal
@[simp, rclike_simps]
theorem re_add_im (z : K) : (re z : K) + im z * I = z :=
RCLike.re_add_im_ax z
#align is_R_or_C.re_add_im RCLike.re_add_im
@[simp, norm_cast, rclike_simps]
theorem ofReal_re : ∀ r : ℝ, re (r : K) = r :=
RCLike.ofReal_re_ax
#align is_R_or_C.of_real_re RCLike.ofReal_re
@[simp, norm_cast, rclike_simps]
theorem ofReal_im : ∀ r : ℝ, im (r : K) = 0 :=
RCLike.ofReal_im_ax
#align is_R_or_C.of_real_im RCLike.ofReal_im
@[simp, rclike_simps]
theorem mul_re : ∀ z w : K, re (z * w) = re z * re w - im z * im w :=
RCLike.mul_re_ax
#align is_R_or_C.mul_re RCLike.mul_re
@[simp, rclike_simps]
theorem mul_im : ∀ z w : K, im (z * w) = re z * im w + im z * re w :=
RCLike.mul_im_ax
#align is_R_or_C.mul_im RCLike.mul_im
theorem ext_iff {z w : K} : z = w ↔ re z = re w ∧ im z = im w :=
⟨fun h => h ▸ ⟨rfl, rfl⟩, fun ⟨h₁, h₂⟩ => re_add_im z ▸ re_add_im w ▸ h₁ ▸ h₂ ▸ rfl⟩
#align is_R_or_C.ext_iff RCLike.ext_iff
theorem ext {z w : K} (hre : re z = re w) (him : im z = im w) : z = w :=
ext_iff.2 ⟨hre, him⟩
#align is_R_or_C.ext RCLike.ext
@[norm_cast]
theorem ofReal_zero : ((0 : ℝ) : K) = 0 :=
algebraMap.coe_zero
#align is_R_or_C.of_real_zero RCLike.ofReal_zero
@[rclike_simps]
theorem zero_re' : re (0 : K) = (0 : ℝ) :=
map_zero re
#align is_R_or_C.zero_re' RCLike.zero_re'
@[norm_cast]
theorem ofReal_one : ((1 : ℝ) : K) = 1 :=
map_one (algebraMap ℝ K)
#align is_R_or_C.of_real_one RCLike.ofReal_one
@[simp, rclike_simps]
theorem one_re : re (1 : K) = 1 := by rw [← ofReal_one, ofReal_re]
#align is_R_or_C.one_re RCLike.one_re
@[simp, rclike_simps]
theorem one_im : im (1 : K) = 0 := by rw [← ofReal_one, ofReal_im]
#align is_R_or_C.one_im RCLike.one_im
theorem ofReal_injective : Function.Injective ((↑) : ℝ → K) :=
(algebraMap ℝ K).injective
#align is_R_or_C.of_real_injective RCLike.ofReal_injective
@[norm_cast]
theorem ofReal_inj {z w : ℝ} : (z : K) = (w : K) ↔ z = w :=
algebraMap.coe_inj
#align is_R_or_C.of_real_inj RCLike.ofReal_inj
-- replaced by `RCLike.ofNat_re`
#noalign is_R_or_C.bit0_re
#noalign is_R_or_C.bit1_re
-- replaced by `RCLike.ofNat_im`
#noalign is_R_or_C.bit0_im
#noalign is_R_or_C.bit1_im
theorem ofReal_eq_zero {x : ℝ} : (x : K) = 0 ↔ x = 0 :=
algebraMap.lift_map_eq_zero_iff x
#align is_R_or_C.of_real_eq_zero RCLike.ofReal_eq_zero
theorem ofReal_ne_zero {x : ℝ} : (x : K) ≠ 0 ↔ x ≠ 0 :=
ofReal_eq_zero.not
#align is_R_or_C.of_real_ne_zero RCLike.ofReal_ne_zero
@[simp, rclike_simps, norm_cast]
theorem ofReal_add (r s : ℝ) : ((r + s : ℝ) : K) = r + s :=
algebraMap.coe_add _ _
#align is_R_or_C.of_real_add RCLike.ofReal_add
-- replaced by `RCLike.ofReal_ofNat`
#noalign is_R_or_C.of_real_bit0
#noalign is_R_or_C.of_real_bit1
@[simp, norm_cast, rclike_simps]
theorem ofReal_neg (r : ℝ) : ((-r : ℝ) : K) = -r :=
algebraMap.coe_neg r
#align is_R_or_C.of_real_neg RCLike.ofReal_neg
@[simp, norm_cast, rclike_simps]
theorem ofReal_sub (r s : ℝ) : ((r - s : ℝ) : K) = r - s :=
map_sub (algebraMap ℝ K) r s
#align is_R_or_C.of_real_sub RCLike.ofReal_sub
@[simp, rclike_simps, norm_cast]
theorem ofReal_sum {α : Type*} (s : Finset α) (f : α → ℝ) :
((∑ i ∈ s, f i : ℝ) : K) = ∑ i ∈ s, (f i : K) :=
map_sum (algebraMap ℝ K) _ _
#align is_R_or_C.of_real_sum RCLike.ofReal_sum
@[simp, rclike_simps, norm_cast]
theorem ofReal_finsupp_sum {α M : Type*} [Zero M] (f : α →₀ M) (g : α → M → ℝ) :
((f.sum fun a b => g a b : ℝ) : K) = f.sum fun a b => (g a b : K) :=
map_finsupp_sum (algebraMap ℝ K) f g
#align is_R_or_C.of_real_finsupp_sum RCLike.ofReal_finsupp_sum
@[simp, norm_cast, rclike_simps]
theorem ofReal_mul (r s : ℝ) : ((r * s : ℝ) : K) = r * s :=
algebraMap.coe_mul _ _
#align is_R_or_C.of_real_mul RCLike.ofReal_mul
@[simp, norm_cast, rclike_simps]
theorem ofReal_pow (r : ℝ) (n : ℕ) : ((r ^ n : ℝ) : K) = (r : K) ^ n :=
map_pow (algebraMap ℝ K) r n
#align is_R_or_C.of_real_pow RCLike.ofReal_pow
@[simp, rclike_simps, norm_cast]
theorem ofReal_prod {α : Type*} (s : Finset α) (f : α → ℝ) :
((∏ i ∈ s, f i : ℝ) : K) = ∏ i ∈ s, (f i : K) :=
map_prod (algebraMap ℝ K) _ _
#align is_R_or_C.of_real_prod RCLike.ofReal_prod
@[simp, rclike_simps, norm_cast]
theorem ofReal_finsupp_prod {α M : Type*} [Zero M] (f : α →₀ M) (g : α → M → ℝ) :
((f.prod fun a b => g a b : ℝ) : K) = f.prod fun a b => (g a b : K) :=
map_finsupp_prod _ f g
#align is_R_or_C.of_real_finsupp_prod RCLike.ofReal_finsupp_prod
@[simp, norm_cast, rclike_simps]
theorem real_smul_ofReal (r x : ℝ) : r • (x : K) = (r : K) * (x : K) :=
real_smul_eq_coe_mul _ _
#align is_R_or_C.real_smul_of_real RCLike.real_smul_ofReal
@[rclike_simps]
theorem re_ofReal_mul (r : ℝ) (z : K) : re (↑r * z) = r * re z := by
simp only [mul_re, ofReal_im, zero_mul, ofReal_re, sub_zero]
#align is_R_or_C.of_real_mul_re RCLike.re_ofReal_mul
@[rclike_simps]
theorem im_ofReal_mul (r : ℝ) (z : K) : im (↑r * z) = r * im z := by
simp only [add_zero, ofReal_im, zero_mul, ofReal_re, mul_im]
#align is_R_or_C.of_real_mul_im RCLike.im_ofReal_mul
@[rclike_simps]
theorem smul_re (r : ℝ) (z : K) : re (r • z) = r * re z := by
rw [real_smul_eq_coe_mul, re_ofReal_mul]
#align is_R_or_C.smul_re RCLike.smul_re
@[rclike_simps]
theorem smul_im (r : ℝ) (z : K) : im (r • z) = r * im z := by
rw [real_smul_eq_coe_mul, im_ofReal_mul]
#align is_R_or_C.smul_im RCLike.smul_im
@[simp, norm_cast, rclike_simps]
theorem norm_ofReal (r : ℝ) : ‖(r : K)‖ = |r| :=
norm_algebraMap' K r
#align is_R_or_C.norm_of_real RCLike.norm_ofReal
/-! ### Characteristic zero -/
-- see Note [lower instance priority]
/-- ℝ and ℂ are both of characteristic zero. -/
instance (priority := 100) charZero_rclike : CharZero K :=
(RingHom.charZero_iff (algebraMap ℝ K).injective).1 inferInstance
set_option linter.uppercaseLean3 false in
#align is_R_or_C.char_zero_R_or_C RCLike.charZero_rclike
/-! ### The imaginary unit, `I` -/
/-- The imaginary unit. -/
@[simp, rclike_simps]
theorem I_re : re (I : K) = 0 :=
I_re_ax
set_option linter.uppercaseLean3 false in
#align is_R_or_C.I_re RCLike.I_re
@[simp, rclike_simps]
theorem I_im (z : K) : im z * im (I : K) = im z :=
mul_im_I_ax z
set_option linter.uppercaseLean3 false in
#align is_R_or_C.I_im RCLike.I_im
@[simp, rclike_simps]
theorem I_im' (z : K) : im (I : K) * im z = im z := by rw [mul_comm, I_im]
set_option linter.uppercaseLean3 false in
#align is_R_or_C.I_im' RCLike.I_im'
@[rclike_simps] -- porting note (#10618): was `simp`
theorem I_mul_re (z : K) : re (I * z) = -im z := by
simp only [I_re, zero_sub, I_im', zero_mul, mul_re]
set_option linter.uppercaseLean3 false in
#align is_R_or_C.I_mul_re RCLike.I_mul_re
theorem I_mul_I : (I : K) = 0 ∨ (I : K) * I = -1 :=
I_mul_I_ax
set_option linter.uppercaseLean3 false in
#align is_R_or_C.I_mul_I RCLike.I_mul_I
variable (𝕜) in
lemma I_eq_zero_or_im_I_eq_one : (I : K) = 0 ∨ im (I : K) = 1 :=
I_mul_I (K := K) |>.imp_right fun h ↦ by simpa [h] using (I_mul_re (I : K)).symm
@[simp, rclike_simps]
theorem conj_re (z : K) : re (conj z) = re z :=
RCLike.conj_re_ax z
#align is_R_or_C.conj_re RCLike.conj_re
@[simp, rclike_simps]
theorem conj_im (z : K) : im (conj z) = -im z :=
RCLike.conj_im_ax z
#align is_R_or_C.conj_im RCLike.conj_im
@[simp, rclike_simps]
theorem conj_I : conj (I : K) = -I :=
RCLike.conj_I_ax
set_option linter.uppercaseLean3 false in
#align is_R_or_C.conj_I RCLike.conj_I
@[simp, rclike_simps]
theorem conj_ofReal (r : ℝ) : conj (r : K) = (r : K) := by
rw [ext_iff]
simp only [ofReal_im, conj_im, eq_self_iff_true, conj_re, and_self_iff, neg_zero]
#align is_R_or_C.conj_of_real RCLike.conj_ofReal
-- replaced by `RCLike.conj_ofNat`
#noalign is_R_or_C.conj_bit0
#noalign is_R_or_C.conj_bit1
theorem conj_nat_cast (n : ℕ) : conj (n : K) = n := map_natCast _ _
-- See note [no_index around OfNat.ofNat]
theorem conj_ofNat (n : ℕ) [n.AtLeastTwo] : conj (no_index (OfNat.ofNat n : K)) = OfNat.ofNat n :=
map_ofNat _ _
@[rclike_simps] -- Porting note (#10618): was a `simp` but `simp` can prove it
theorem conj_neg_I : conj (-I) = (I : K) := by rw [map_neg, conj_I, neg_neg]
set_option linter.uppercaseLean3 false in
#align is_R_or_C.conj_neg_I RCLike.conj_neg_I
theorem conj_eq_re_sub_im (z : K) : conj z = re z - im z * I :=
(congr_arg conj (re_add_im z).symm).trans <| by
rw [map_add, map_mul, conj_I, conj_ofReal, conj_ofReal, mul_neg, sub_eq_add_neg]
#align is_R_or_C.conj_eq_re_sub_im RCLike.conj_eq_re_sub_im
theorem sub_conj (z : K) : z - conj z = 2 * im z * I :=
calc
z - conj z = re z + im z * I - (re z - im z * I) := by rw [re_add_im, ← conj_eq_re_sub_im]
_ = 2 * im z * I := by rw [add_sub_sub_cancel, ← two_mul, mul_assoc]
#align is_R_or_C.sub_conj RCLike.sub_conj
@[rclike_simps]
theorem conj_smul (r : ℝ) (z : K) : conj (r • z) = r • conj z := by
rw [conj_eq_re_sub_im, conj_eq_re_sub_im, smul_re, smul_im, ofReal_mul, ofReal_mul,
real_smul_eq_coe_mul r (_ - _), mul_sub, mul_assoc]
#align is_R_or_C.conj_smul RCLike.conj_smul
theorem add_conj (z : K) : z + conj z = 2 * re z :=
calc
z + conj z = re z + im z * I + (re z - im z * I) := by rw [re_add_im, conj_eq_re_sub_im]
_ = 2 * re z := by rw [add_add_sub_cancel, two_mul]
#align is_R_or_C.add_conj RCLike.add_conj
theorem re_eq_add_conj (z : K) : ↑(re z) = (z + conj z) / 2 := by
rw [add_conj, mul_div_cancel_left₀ (re z : K) two_ne_zero]
#align is_R_or_C.re_eq_add_conj RCLike.re_eq_add_conj
theorem im_eq_conj_sub (z : K) : ↑(im z) = I * (conj z - z) / 2 := by
rw [← neg_inj, ← ofReal_neg, ← I_mul_re, re_eq_add_conj, map_mul, conj_I, ← neg_div, ← mul_neg,
neg_sub, mul_sub, neg_mul, sub_eq_add_neg]
#align is_R_or_C.im_eq_conj_sub RCLike.im_eq_conj_sub
open List in
/-- There are several equivalent ways to say that a number `z` is in fact a real number. -/
theorem is_real_TFAE (z : K) : TFAE [conj z = z, ∃ r : ℝ, (r : K) = z, ↑(re z) = z, im z = 0] := by
tfae_have 1 → 4
· intro h
rw [← @ofReal_inj K, im_eq_conj_sub, h, sub_self, mul_zero, zero_div,
ofReal_zero]
tfae_have 4 → 3
· intro h
conv_rhs => rw [← re_add_im z, h, ofReal_zero, zero_mul, add_zero]
tfae_have 3 → 2
· exact fun h => ⟨_, h⟩
tfae_have 2 → 1
· exact fun ⟨r, hr⟩ => hr ▸ conj_ofReal _
tfae_finish
#align is_R_or_C.is_real_tfae RCLike.is_real_TFAE
theorem conj_eq_iff_real {z : K} : conj z = z ↔ ∃ r : ℝ, z = (r : K) :=
((is_real_TFAE z).out 0 1).trans <| by simp only [eq_comm]
#align is_R_or_C.conj_eq_iff_real RCLike.conj_eq_iff_real
theorem conj_eq_iff_re {z : K} : conj z = z ↔ (re z : K) = z :=
(is_real_TFAE z).out 0 2
#align is_R_or_C.conj_eq_iff_re RCLike.conj_eq_iff_re
theorem conj_eq_iff_im {z : K} : conj z = z ↔ im z = 0 :=
(is_real_TFAE z).out 0 3
#align is_R_or_C.conj_eq_iff_im RCLike.conj_eq_iff_im
@[simp]
theorem star_def : (Star.star : K → K) = conj :=
rfl
#align is_R_or_C.star_def RCLike.star_def
variable (K)
/-- Conjugation as a ring equivalence. This is used to convert the inner product into a
sesquilinear product. -/
abbrev conjToRingEquiv : K ≃+* Kᵐᵒᵖ :=
starRingEquiv
#align is_R_or_C.conj_to_ring_equiv RCLike.conjToRingEquiv
variable {K} {z : K}
/-- The norm squared function. -/
def normSq : K →*₀ ℝ where
toFun z := re z * re z + im z * im z
map_zero' := by simp only [add_zero, mul_zero, map_zero]
map_one' := by simp only [one_im, add_zero, mul_one, one_re, mul_zero]
map_mul' z w := by
simp only [mul_im, mul_re]
ring
#align is_R_or_C.norm_sq RCLike.normSq
theorem normSq_apply (z : K) : normSq z = re z * re z + im z * im z :=
rfl
#align is_R_or_C.norm_sq_apply RCLike.normSq_apply
theorem norm_sq_eq_def {z : K} : ‖z‖ ^ 2 = re z * re z + im z * im z :=
norm_sq_eq_def_ax z
#align is_R_or_C.norm_sq_eq_def RCLike.norm_sq_eq_def
theorem normSq_eq_def' (z : K) : normSq z = ‖z‖ ^ 2 :=
norm_sq_eq_def.symm
#align is_R_or_C.norm_sq_eq_def' RCLike.normSq_eq_def'
@[rclike_simps]
theorem normSq_zero : normSq (0 : K) = 0 :=
normSq.map_zero
#align is_R_or_C.norm_sq_zero RCLike.normSq_zero
@[rclike_simps]
theorem normSq_one : normSq (1 : K) = 1 :=
normSq.map_one
#align is_R_or_C.norm_sq_one RCLike.normSq_one
theorem normSq_nonneg (z : K) : 0 ≤ normSq z :=
add_nonneg (mul_self_nonneg _) (mul_self_nonneg _)
#align is_R_or_C.norm_sq_nonneg RCLike.normSq_nonneg
@[rclike_simps] -- porting note (#10618): was `simp`
theorem normSq_eq_zero {z : K} : normSq z = 0 ↔ z = 0 :=
map_eq_zero _
#align is_R_or_C.norm_sq_eq_zero RCLike.normSq_eq_zero
@[simp, rclike_simps]
theorem normSq_pos {z : K} : 0 < normSq z ↔ z ≠ 0 := by
rw [lt_iff_le_and_ne, Ne, eq_comm]; simp [normSq_nonneg]
#align is_R_or_C.norm_sq_pos RCLike.normSq_pos
@[simp, rclike_simps]
| Mathlib/Analysis/RCLike/Basic.lean | 480 | 480 | theorem normSq_neg (z : K) : normSq (-z) = normSq z := by | simp only [normSq_eq_def', norm_neg]
|
/-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Johannes Hölzl, Scott Morrison, Jens Wagemaker
-/
import Mathlib.Algebra.MonoidAlgebra.Support
import Mathlib.Algebra.Polynomial.Basic
import Mathlib.Algebra.Regular.Basic
import Mathlib.Data.Nat.Choose.Sum
#align_import data.polynomial.coeff from "leanprover-community/mathlib"@"2651125b48fc5c170ab1111afd0817c903b1fc6c"
/-!
# Theory of univariate polynomials
The theorems include formulas for computing coefficients, such as
`coeff_add`, `coeff_sum`, `coeff_mul`
-/
set_option linter.uppercaseLean3 false
noncomputable section
open Finsupp Finset AddMonoidAlgebra
open Polynomial
namespace Polynomial
universe u v
variable {R : Type u} {S : Type v} {a b : R} {n m : ℕ}
variable [Semiring R] {p q r : R[X]}
section Coeff
@[simp]
theorem coeff_add (p q : R[X]) (n : ℕ) : coeff (p + q) n = coeff p n + coeff q n := by
rcases p with ⟨⟩
rcases q with ⟨⟩
simp_rw [← ofFinsupp_add, coeff]
exact Finsupp.add_apply _ _ _
#align polynomial.coeff_add Polynomial.coeff_add
set_option linter.deprecated false in
@[simp]
theorem coeff_bit0 (p : R[X]) (n : ℕ) : coeff (bit0 p) n = bit0 (coeff p n) := by simp [bit0]
#align polynomial.coeff_bit0 Polynomial.coeff_bit0
@[simp]
theorem coeff_smul [SMulZeroClass S R] (r : S) (p : R[X]) (n : ℕ) :
coeff (r • p) n = r • coeff p n := by
rcases p with ⟨⟩
simp_rw [← ofFinsupp_smul, coeff]
exact Finsupp.smul_apply _ _ _
#align polynomial.coeff_smul Polynomial.coeff_smul
theorem support_smul [SMulZeroClass S R] (r : S) (p : R[X]) :
support (r • p) ⊆ support p := by
intro i hi
simp? [mem_support_iff] at hi ⊢ says simp only [mem_support_iff, coeff_smul, ne_eq] at hi ⊢
contrapose! hi
simp [hi]
#align polynomial.support_smul Polynomial.support_smul
open scoped Pointwise in
theorem card_support_mul_le : (p * q).support.card ≤ p.support.card * q.support.card := by
calc (p * q).support.card
_ = (p.toFinsupp * q.toFinsupp).support.card := by rw [← support_toFinsupp, toFinsupp_mul]
_ ≤ (p.toFinsupp.support + q.toFinsupp.support).card :=
Finset.card_le_card (AddMonoidAlgebra.support_mul p.toFinsupp q.toFinsupp)
_ ≤ p.support.card * q.support.card := Finset.card_image₂_le ..
/-- `Polynomial.sum` as a linear map. -/
@[simps]
def lsum {R A M : Type*} [Semiring R] [Semiring A] [AddCommMonoid M] [Module R A] [Module R M]
(f : ℕ → A →ₗ[R] M) : A[X] →ₗ[R] M where
toFun p := p.sum (f · ·)
map_add' p q := sum_add_index p q _ (fun n => (f n).map_zero) fun n _ _ => (f n).map_add _ _
map_smul' c p := by
-- Porting note: added `dsimp only`; `beta_reduce` alone is not sufficient
dsimp only
rw [sum_eq_of_subset (f · ·) (fun n => (f n).map_zero) (support_smul c p)]
simp only [sum_def, Finset.smul_sum, coeff_smul, LinearMap.map_smul, RingHom.id_apply]
#align polynomial.lsum Polynomial.lsum
#align polynomial.lsum_apply Polynomial.lsum_apply
variable (R)
/-- The nth coefficient, as a linear map. -/
def lcoeff (n : ℕ) : R[X] →ₗ[R] R where
toFun p := coeff p n
map_add' p q := coeff_add p q n
map_smul' r p := coeff_smul r p n
#align polynomial.lcoeff Polynomial.lcoeff
variable {R}
@[simp]
theorem lcoeff_apply (n : ℕ) (f : R[X]) : lcoeff R n f = coeff f n :=
rfl
#align polynomial.lcoeff_apply Polynomial.lcoeff_apply
@[simp]
theorem finset_sum_coeff {ι : Type*} (s : Finset ι) (f : ι → R[X]) (n : ℕ) :
coeff (∑ b ∈ s, f b) n = ∑ b ∈ s, coeff (f b) n :=
map_sum (lcoeff R n) _ _
#align polynomial.finset_sum_coeff Polynomial.finset_sum_coeff
lemma coeff_list_sum (l : List R[X]) (n : ℕ) :
l.sum.coeff n = (l.map (lcoeff R n)).sum :=
map_list_sum (lcoeff R n) _
lemma coeff_list_sum_map {ι : Type*} (l : List ι) (f : ι → R[X]) (n : ℕ) :
(l.map f).sum.coeff n = (l.map (fun a => (f a).coeff n)).sum := by
simp_rw [coeff_list_sum, List.map_map, Function.comp, lcoeff_apply]
theorem coeff_sum [Semiring S] (n : ℕ) (f : ℕ → R → S[X]) :
coeff (p.sum f) n = p.sum fun a b => coeff (f a b) n := by
rcases p with ⟨⟩
-- porting note (#10745): was `simp [Polynomial.sum, support, coeff]`.
simp [Polynomial.sum, support_ofFinsupp, coeff_ofFinsupp]
#align polynomial.coeff_sum Polynomial.coeff_sum
/-- Decomposes the coefficient of the product `p * q` as a sum
over `antidiagonal`. A version which sums over `range (n + 1)` can be obtained
by using `Finset.Nat.sum_antidiagonal_eq_sum_range_succ`. -/
theorem coeff_mul (p q : R[X]) (n : ℕ) :
coeff (p * q) n = ∑ x ∈ antidiagonal n, coeff p x.1 * coeff q x.2 := by
rcases p with ⟨p⟩; rcases q with ⟨q⟩
simp_rw [← ofFinsupp_mul, coeff]
exact AddMonoidAlgebra.mul_apply_antidiagonal p q n _ Finset.mem_antidiagonal
#align polynomial.coeff_mul Polynomial.coeff_mul
@[simp]
theorem mul_coeff_zero (p q : R[X]) : coeff (p * q) 0 = coeff p 0 * coeff q 0 := by simp [coeff_mul]
#align polynomial.mul_coeff_zero Polynomial.mul_coeff_zero
/-- `constantCoeff p` returns the constant term of the polynomial `p`,
defined as `coeff p 0`. This is a ring homomorphism. -/
@[simps]
def constantCoeff : R[X] →+* R where
toFun p := coeff p 0
map_one' := coeff_one_zero
map_mul' := mul_coeff_zero
map_zero' := coeff_zero 0
map_add' p q := coeff_add p q 0
#align polynomial.constant_coeff Polynomial.constantCoeff
#align polynomial.constant_coeff_apply Polynomial.constantCoeff_apply
theorem isUnit_C {x : R} : IsUnit (C x) ↔ IsUnit x :=
⟨fun h => (congr_arg IsUnit coeff_C_zero).mp (h.map <| @constantCoeff R _), fun h => h.map C⟩
#align polynomial.is_unit_C Polynomial.isUnit_C
theorem coeff_mul_X_zero (p : R[X]) : coeff (p * X) 0 = 0 := by simp
#align polynomial.coeff_mul_X_zero Polynomial.coeff_mul_X_zero
theorem coeff_X_mul_zero (p : R[X]) : coeff (X * p) 0 = 0 := by simp
#align polynomial.coeff_X_mul_zero Polynomial.coeff_X_mul_zero
| Mathlib/Algebra/Polynomial/Coeff.lean | 163 | 167 | theorem coeff_C_mul_X_pow (x : R) (k n : ℕ) :
coeff (C x * X ^ k : R[X]) n = if n = k then x else 0 := by |
rw [C_mul_X_pow_eq_monomial, coeff_monomial]
congr 1
simp [eq_comm]
|
/-
Copyright (c) 2020 Filippo A. E. Nuccio. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Filippo A. E. Nuccio, Andrew Yang
-/
import Mathlib.AlgebraicGeometry.PrimeSpectrum.Basic
import Mathlib.Topology.NoetherianSpace
#align_import algebraic_geometry.prime_spectrum.noetherian from "leanprover-community/mathlib"@"052f6013363326d50cb99c6939814a4b8eb7b301"
/-!
This file proves additional properties of the prime spectrum a ring is Noetherian.
-/
universe u v
namespace PrimeSpectrum
open Submodule
variable (R : Type u) [CommRing R] [IsNoetherianRing R]
variable {A : Type u} [CommRing A] [IsDomain A] [IsNoetherianRing A]
/-- In a noetherian ring, every ideal contains a product of prime ideals
([samuel, § 3.3, Lemma 3])-/
| Mathlib/AlgebraicGeometry/PrimeSpectrum/Noetherian.lean | 27 | 54 | theorem exists_primeSpectrum_prod_le (I : Ideal R) :
∃ Z : Multiset (PrimeSpectrum R), Multiset.prod (Z.map asIdeal) ≤ I := by |
-- Porting note: Need to specify `P` explicitly
refine IsNoetherian.induction
(P := fun I => ∃ Z : Multiset (PrimeSpectrum R), Multiset.prod (Z.map asIdeal) ≤ I)
(fun (M : Ideal R) hgt => ?_) I
by_cases h_prM : M.IsPrime
· use {⟨M, h_prM⟩}
rw [Multiset.map_singleton, Multiset.prod_singleton]
by_cases htop : M = ⊤
· rw [htop]
exact ⟨0, le_top⟩
have lt_add : ∀ z ∉ M, M < M + span R {z} := by
intro z hz
refine lt_of_le_of_ne le_sup_left fun m_eq => hz ?_
rw [m_eq]
exact Ideal.mem_sup_right (mem_span_singleton_self z)
obtain ⟨x, hx, y, hy, hxy⟩ := (Ideal.not_isPrime_iff.mp h_prM).resolve_left htop
obtain ⟨Wx, h_Wx⟩ := hgt (M + span R {x}) (lt_add _ hx)
obtain ⟨Wy, h_Wy⟩ := hgt (M + span R {y}) (lt_add _ hy)
use Wx + Wy
rw [Multiset.map_add, Multiset.prod_add]
apply le_trans (Submodule.mul_le_mul h_Wx h_Wy)
rw [add_mul]
apply sup_le (show M * (M + span R {y}) ≤ M from Ideal.mul_le_right)
rw [mul_add]
apply sup_le (show span R {x} * M ≤ M from Ideal.mul_le_left)
rwa [span_mul_span, Set.singleton_mul_singleton, span_singleton_le_iff_mem]
|
/-
Copyright (c) 2019 Gabriel Ebner. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Gabriel Ebner, Sébastien Gouëzel
-/
import Mathlib.Analysis.Calculus.FDeriv.Basic
import Mathlib.Analysis.NormedSpace.OperatorNorm.NormedSpace
#align_import analysis.calculus.deriv.basic from "leanprover-community/mathlib"@"3bce8d800a6f2b8f63fe1e588fd76a9ff4adcebe"
/-!
# One-dimensional derivatives
This file defines the derivative of a function `f : 𝕜 → F` where `𝕜` is a
normed field and `F` is a normed space over this field. The derivative of
such a function `f` at a point `x` is given by an element `f' : F`.
The theory is developed analogously to the [Fréchet
derivatives](./fderiv.html). We first introduce predicates defined in terms
of the corresponding predicates for Fréchet derivatives:
- `HasDerivAtFilter f f' x L` states that the function `f` has the
derivative `f'` at the point `x` as `x` goes along the filter `L`.
- `HasDerivWithinAt f f' s x` states that the function `f` has the
derivative `f'` at the point `x` within the subset `s`.
- `HasDerivAt f f' x` states that the function `f` has the derivative `f'`
at the point `x`.
- `HasStrictDerivAt f f' x` states that the function `f` has the derivative `f'`
at the point `x` in the sense of strict differentiability, i.e.,
`f y - f z = (y - z) • f' + o (y - z)` as `y, z → x`.
For the last two notions we also define a functional version:
- `derivWithin f s x` is a derivative of `f` at `x` within `s`. If the
derivative does not exist, then `derivWithin f s x` equals zero.
- `deriv f x` is a derivative of `f` at `x`. If the derivative does not
exist, then `deriv f x` equals zero.
The theorems `fderivWithin_derivWithin` and `fderiv_deriv` show that the
one-dimensional derivatives coincide with the general Fréchet derivatives.
We also show the existence and compute the derivatives of:
- constants
- the identity function
- linear maps (in `Linear.lean`)
- addition (in `Add.lean`)
- sum of finitely many functions (in `Add.lean`)
- negation (in `Add.lean`)
- subtraction (in `Add.lean`)
- star (in `Star.lean`)
- multiplication of two functions in `𝕜 → 𝕜` (in `Mul.lean`)
- multiplication of a function in `𝕜 → 𝕜` and of a function in `𝕜 → E` (in `Mul.lean`)
- powers of a function (in `Pow.lean` and `ZPow.lean`)
- inverse `x → x⁻¹` (in `Inv.lean`)
- division (in `Inv.lean`)
- composition of a function in `𝕜 → F` with a function in `𝕜 → 𝕜` (in `Comp.lean`)
- composition of a function in `F → E` with a function in `𝕜 → F` (in `Comp.lean`)
- inverse function (assuming that it exists; the inverse function theorem is in `Inverse.lean`)
- polynomials (in `Polynomial.lean`)
For most binary operations we also define `const_op` and `op_const` theorems for the cases when
the first or second argument is a constant. This makes writing chains of `HasDerivAt`'s easier,
and they more frequently lead to the desired result.
We set up the simplifier so that it can compute the derivative of simple functions. For instance,
```lean
example (x : ℝ) :
deriv (fun x ↦ cos (sin x) * exp x) x = (cos(sin(x))-sin(sin(x))*cos(x))*exp(x) := by
simp; ring
```
The relationship between the derivative of a function and its definition from a standard
undergraduate course as the limit of the slope `(f y - f x) / (y - x)` as `y` tends to `𝓝[≠] x`
is developed in the file `Slope.lean`.
## Implementation notes
Most of the theorems are direct restatements of the corresponding theorems
for Fréchet derivatives.
The strategy to construct simp lemmas that give the simplifier the possibility to compute
derivatives is the same as the one for differentiability statements, as explained in
`FDeriv/Basic.lean`. See the explanations there.
-/
universe u v w
noncomputable section
open scoped Classical Topology Filter ENNReal NNReal
open Filter Asymptotics Set
open ContinuousLinearMap (smulRight smulRight_one_eq_iff)
variable {𝕜 : Type u} [NontriviallyNormedField 𝕜]
variable {F : Type v} [NormedAddCommGroup F] [NormedSpace 𝕜 F]
variable {E : Type w} [NormedAddCommGroup E] [NormedSpace 𝕜 E]
/-- `f` has the derivative `f'` at the point `x` as `x` goes along the filter `L`.
That is, `f x' = f x + (x' - x) • f' + o(x' - x)` where `x'` converges along the filter `L`.
-/
def HasDerivAtFilter (f : 𝕜 → F) (f' : F) (x : 𝕜) (L : Filter 𝕜) :=
HasFDerivAtFilter f (smulRight (1 : 𝕜 →L[𝕜] 𝕜) f') x L
#align has_deriv_at_filter HasDerivAtFilter
/-- `f` has the derivative `f'` at the point `x` within the subset `s`.
That is, `f x' = f x + (x' - x) • f' + o(x' - x)` where `x'` converges to `x` inside `s`.
-/
def HasDerivWithinAt (f : 𝕜 → F) (f' : F) (s : Set 𝕜) (x : 𝕜) :=
HasDerivAtFilter f f' x (𝓝[s] x)
#align has_deriv_within_at HasDerivWithinAt
/-- `f` has the derivative `f'` at the point `x`.
That is, `f x' = f x + (x' - x) • f' + o(x' - x)` where `x'` converges to `x`.
-/
def HasDerivAt (f : 𝕜 → F) (f' : F) (x : 𝕜) :=
HasDerivAtFilter f f' x (𝓝 x)
#align has_deriv_at HasDerivAt
/-- `f` has the derivative `f'` at the point `x` in the sense of strict differentiability.
That is, `f y - f z = (y - z) • f' + o(y - z)` as `y, z → x`. -/
def HasStrictDerivAt (f : 𝕜 → F) (f' : F) (x : 𝕜) :=
HasStrictFDerivAt f (smulRight (1 : 𝕜 →L[𝕜] 𝕜) f') x
#align has_strict_deriv_at HasStrictDerivAt
/-- Derivative of `f` at the point `x` within the set `s`, if it exists. Zero otherwise.
If the derivative exists (i.e., `∃ f', HasDerivWithinAt f f' s x`), then
`f x' = f x + (x' - x) • derivWithin f s x + o(x' - x)` where `x'` converges to `x` inside `s`.
-/
def derivWithin (f : 𝕜 → F) (s : Set 𝕜) (x : 𝕜) :=
fderivWithin 𝕜 f s x 1
#align deriv_within derivWithin
/-- Derivative of `f` at the point `x`, if it exists. Zero otherwise.
If the derivative exists (i.e., `∃ f', HasDerivAt f f' x`), then
`f x' = f x + (x' - x) • deriv f x + o(x' - x)` where `x'` converges to `x`.
-/
def deriv (f : 𝕜 → F) (x : 𝕜) :=
fderiv 𝕜 f x 1
#align deriv deriv
variable {f f₀ f₁ g : 𝕜 → F}
variable {f' f₀' f₁' g' : F}
variable {x : 𝕜}
variable {s t : Set 𝕜}
variable {L L₁ L₂ : Filter 𝕜}
/-- Expressing `HasFDerivAtFilter f f' x L` in terms of `HasDerivAtFilter` -/
theorem hasFDerivAtFilter_iff_hasDerivAtFilter {f' : 𝕜 →L[𝕜] F} :
HasFDerivAtFilter f f' x L ↔ HasDerivAtFilter f (f' 1) x L := by simp [HasDerivAtFilter]
#align has_fderiv_at_filter_iff_has_deriv_at_filter hasFDerivAtFilter_iff_hasDerivAtFilter
theorem HasFDerivAtFilter.hasDerivAtFilter {f' : 𝕜 →L[𝕜] F} :
HasFDerivAtFilter f f' x L → HasDerivAtFilter f (f' 1) x L :=
hasFDerivAtFilter_iff_hasDerivAtFilter.mp
#align has_fderiv_at_filter.has_deriv_at_filter HasFDerivAtFilter.hasDerivAtFilter
/-- Expressing `HasFDerivWithinAt f f' s x` in terms of `HasDerivWithinAt` -/
theorem hasFDerivWithinAt_iff_hasDerivWithinAt {f' : 𝕜 →L[𝕜] F} :
HasFDerivWithinAt f f' s x ↔ HasDerivWithinAt f (f' 1) s x :=
hasFDerivAtFilter_iff_hasDerivAtFilter
#align has_fderiv_within_at_iff_has_deriv_within_at hasFDerivWithinAt_iff_hasDerivWithinAt
/-- Expressing `HasDerivWithinAt f f' s x` in terms of `HasFDerivWithinAt` -/
theorem hasDerivWithinAt_iff_hasFDerivWithinAt {f' : F} :
HasDerivWithinAt f f' s x ↔ HasFDerivWithinAt f (smulRight (1 : 𝕜 →L[𝕜] 𝕜) f') s x :=
Iff.rfl
#align has_deriv_within_at_iff_has_fderiv_within_at hasDerivWithinAt_iff_hasFDerivWithinAt
theorem HasFDerivWithinAt.hasDerivWithinAt {f' : 𝕜 →L[𝕜] F} :
HasFDerivWithinAt f f' s x → HasDerivWithinAt f (f' 1) s x :=
hasFDerivWithinAt_iff_hasDerivWithinAt.mp
#align has_fderiv_within_at.has_deriv_within_at HasFDerivWithinAt.hasDerivWithinAt
theorem HasDerivWithinAt.hasFDerivWithinAt {f' : F} :
HasDerivWithinAt f f' s x → HasFDerivWithinAt f (smulRight (1 : 𝕜 →L[𝕜] 𝕜) f') s x :=
hasDerivWithinAt_iff_hasFDerivWithinAt.mp
#align has_deriv_within_at.has_fderiv_within_at HasDerivWithinAt.hasFDerivWithinAt
/-- Expressing `HasFDerivAt f f' x` in terms of `HasDerivAt` -/
theorem hasFDerivAt_iff_hasDerivAt {f' : 𝕜 →L[𝕜] F} : HasFDerivAt f f' x ↔ HasDerivAt f (f' 1) x :=
hasFDerivAtFilter_iff_hasDerivAtFilter
#align has_fderiv_at_iff_has_deriv_at hasFDerivAt_iff_hasDerivAt
theorem HasFDerivAt.hasDerivAt {f' : 𝕜 →L[𝕜] F} : HasFDerivAt f f' x → HasDerivAt f (f' 1) x :=
hasFDerivAt_iff_hasDerivAt.mp
#align has_fderiv_at.has_deriv_at HasFDerivAt.hasDerivAt
theorem hasStrictFDerivAt_iff_hasStrictDerivAt {f' : 𝕜 →L[𝕜] F} :
HasStrictFDerivAt f f' x ↔ HasStrictDerivAt f (f' 1) x := by
simp [HasStrictDerivAt, HasStrictFDerivAt]
#align has_strict_fderiv_at_iff_has_strict_deriv_at hasStrictFDerivAt_iff_hasStrictDerivAt
protected theorem HasStrictFDerivAt.hasStrictDerivAt {f' : 𝕜 →L[𝕜] F} :
HasStrictFDerivAt f f' x → HasStrictDerivAt f (f' 1) x :=
hasStrictFDerivAt_iff_hasStrictDerivAt.mp
#align has_strict_fderiv_at.has_strict_deriv_at HasStrictFDerivAt.hasStrictDerivAt
theorem hasStrictDerivAt_iff_hasStrictFDerivAt :
HasStrictDerivAt f f' x ↔ HasStrictFDerivAt f (smulRight (1 : 𝕜 →L[𝕜] 𝕜) f') x :=
Iff.rfl
#align has_strict_deriv_at_iff_has_strict_fderiv_at hasStrictDerivAt_iff_hasStrictFDerivAt
alias ⟨HasStrictDerivAt.hasStrictFDerivAt, _⟩ := hasStrictDerivAt_iff_hasStrictFDerivAt
#align has_strict_deriv_at.has_strict_fderiv_at HasStrictDerivAt.hasStrictFDerivAt
/-- Expressing `HasDerivAt f f' x` in terms of `HasFDerivAt` -/
theorem hasDerivAt_iff_hasFDerivAt {f' : F} :
HasDerivAt f f' x ↔ HasFDerivAt f (smulRight (1 : 𝕜 →L[𝕜] 𝕜) f') x :=
Iff.rfl
#align has_deriv_at_iff_has_fderiv_at hasDerivAt_iff_hasFDerivAt
alias ⟨HasDerivAt.hasFDerivAt, _⟩ := hasDerivAt_iff_hasFDerivAt
#align has_deriv_at.has_fderiv_at HasDerivAt.hasFDerivAt
theorem derivWithin_zero_of_not_differentiableWithinAt (h : ¬DifferentiableWithinAt 𝕜 f s x) :
derivWithin f s x = 0 := by
unfold derivWithin
rw [fderivWithin_zero_of_not_differentiableWithinAt h]
simp
#align deriv_within_zero_of_not_differentiable_within_at derivWithin_zero_of_not_differentiableWithinAt
theorem derivWithin_zero_of_isolated (h : 𝓝[s \ {x}] x = ⊥) : derivWithin f s x = 0 := by
rw [derivWithin, fderivWithin_zero_of_isolated h, ContinuousLinearMap.zero_apply]
theorem derivWithin_zero_of_nmem_closure (h : x ∉ closure s) : derivWithin f s x = 0 := by
rw [derivWithin, fderivWithin_zero_of_nmem_closure h, ContinuousLinearMap.zero_apply]
theorem differentiableWithinAt_of_derivWithin_ne_zero (h : derivWithin f s x ≠ 0) :
DifferentiableWithinAt 𝕜 f s x :=
not_imp_comm.1 derivWithin_zero_of_not_differentiableWithinAt h
#align differentiable_within_at_of_deriv_within_ne_zero differentiableWithinAt_of_derivWithin_ne_zero
theorem deriv_zero_of_not_differentiableAt (h : ¬DifferentiableAt 𝕜 f x) : deriv f x = 0 := by
unfold deriv
rw [fderiv_zero_of_not_differentiableAt h]
simp
#align deriv_zero_of_not_differentiable_at deriv_zero_of_not_differentiableAt
theorem differentiableAt_of_deriv_ne_zero (h : deriv f x ≠ 0) : DifferentiableAt 𝕜 f x :=
not_imp_comm.1 deriv_zero_of_not_differentiableAt h
#align differentiable_at_of_deriv_ne_zero differentiableAt_of_deriv_ne_zero
theorem UniqueDiffWithinAt.eq_deriv (s : Set 𝕜) (H : UniqueDiffWithinAt 𝕜 s x)
(h : HasDerivWithinAt f f' s x) (h₁ : HasDerivWithinAt f f₁' s x) : f' = f₁' :=
smulRight_one_eq_iff.mp <| UniqueDiffWithinAt.eq H h h₁
#align unique_diff_within_at.eq_deriv UniqueDiffWithinAt.eq_deriv
theorem hasDerivAtFilter_iff_isLittleO :
HasDerivAtFilter f f' x L ↔ (fun x' : 𝕜 => f x' - f x - (x' - x) • f') =o[L] fun x' => x' - x :=
hasFDerivAtFilter_iff_isLittleO ..
#align has_deriv_at_filter_iff_is_o hasDerivAtFilter_iff_isLittleO
theorem hasDerivAtFilter_iff_tendsto :
HasDerivAtFilter f f' x L ↔
Tendsto (fun x' : 𝕜 => ‖x' - x‖⁻¹ * ‖f x' - f x - (x' - x) • f'‖) L (𝓝 0) :=
hasFDerivAtFilter_iff_tendsto
#align has_deriv_at_filter_iff_tendsto hasDerivAtFilter_iff_tendsto
theorem hasDerivWithinAt_iff_isLittleO :
HasDerivWithinAt f f' s x ↔
(fun x' : 𝕜 => f x' - f x - (x' - x) • f') =o[𝓝[s] x] fun x' => x' - x :=
hasFDerivAtFilter_iff_isLittleO ..
#align has_deriv_within_at_iff_is_o hasDerivWithinAt_iff_isLittleO
theorem hasDerivWithinAt_iff_tendsto :
HasDerivWithinAt f f' s x ↔
Tendsto (fun x' => ‖x' - x‖⁻¹ * ‖f x' - f x - (x' - x) • f'‖) (𝓝[s] x) (𝓝 0) :=
hasFDerivAtFilter_iff_tendsto
#align has_deriv_within_at_iff_tendsto hasDerivWithinAt_iff_tendsto
theorem hasDerivAt_iff_isLittleO :
HasDerivAt f f' x ↔ (fun x' : 𝕜 => f x' - f x - (x' - x) • f') =o[𝓝 x] fun x' => x' - x :=
hasFDerivAtFilter_iff_isLittleO ..
#align has_deriv_at_iff_is_o hasDerivAt_iff_isLittleO
theorem hasDerivAt_iff_tendsto :
HasDerivAt f f' x ↔ Tendsto (fun x' => ‖x' - x‖⁻¹ * ‖f x' - f x - (x' - x) • f'‖) (𝓝 x) (𝓝 0) :=
hasFDerivAtFilter_iff_tendsto
#align has_deriv_at_iff_tendsto hasDerivAt_iff_tendsto
theorem HasDerivAtFilter.isBigO_sub (h : HasDerivAtFilter f f' x L) :
(fun x' => f x' - f x) =O[L] fun x' => x' - x :=
HasFDerivAtFilter.isBigO_sub h
set_option linter.uppercaseLean3 false in
#align has_deriv_at_filter.is_O_sub HasDerivAtFilter.isBigO_sub
nonrec theorem HasDerivAtFilter.isBigO_sub_rev (hf : HasDerivAtFilter f f' x L) (hf' : f' ≠ 0) :
(fun x' => x' - x) =O[L] fun x' => f x' - f x :=
suffices AntilipschitzWith ‖f'‖₊⁻¹ (smulRight (1 : 𝕜 →L[𝕜] 𝕜) f') from hf.isBigO_sub_rev this
AddMonoidHomClass.antilipschitz_of_bound (smulRight (1 : 𝕜 →L[𝕜] 𝕜) f') fun x => by
simp [norm_smul, ← div_eq_inv_mul, mul_div_cancel_right₀ _ (mt norm_eq_zero.1 hf')]
set_option linter.uppercaseLean3 false in
#align has_deriv_at_filter.is_O_sub_rev HasDerivAtFilter.isBigO_sub_rev
theorem HasStrictDerivAt.hasDerivAt (h : HasStrictDerivAt f f' x) : HasDerivAt f f' x :=
h.hasFDerivAt
#align has_strict_deriv_at.has_deriv_at HasStrictDerivAt.hasDerivAt
theorem hasDerivWithinAt_congr_set' {s t : Set 𝕜} (y : 𝕜) (h : s =ᶠ[𝓝[{y}ᶜ] x] t) :
HasDerivWithinAt f f' s x ↔ HasDerivWithinAt f f' t x :=
hasFDerivWithinAt_congr_set' y h
#align has_deriv_within_at_congr_set' hasDerivWithinAt_congr_set'
theorem hasDerivWithinAt_congr_set {s t : Set 𝕜} (h : s =ᶠ[𝓝 x] t) :
HasDerivWithinAt f f' s x ↔ HasDerivWithinAt f f' t x :=
hasFDerivWithinAt_congr_set h
#align has_deriv_within_at_congr_set hasDerivWithinAt_congr_set
alias ⟨HasDerivWithinAt.congr_set, _⟩ := hasDerivWithinAt_congr_set
#align has_deriv_within_at.congr_set HasDerivWithinAt.congr_set
@[simp]
theorem hasDerivWithinAt_diff_singleton :
HasDerivWithinAt f f' (s \ {x}) x ↔ HasDerivWithinAt f f' s x :=
hasFDerivWithinAt_diff_singleton _
#align has_deriv_within_at_diff_singleton hasDerivWithinAt_diff_singleton
@[simp]
theorem hasDerivWithinAt_Ioi_iff_Ici [PartialOrder 𝕜] :
HasDerivWithinAt f f' (Ioi x) x ↔ HasDerivWithinAt f f' (Ici x) x := by
rw [← Ici_diff_left, hasDerivWithinAt_diff_singleton]
#align has_deriv_within_at_Ioi_iff_Ici hasDerivWithinAt_Ioi_iff_Ici
alias ⟨HasDerivWithinAt.Ici_of_Ioi, HasDerivWithinAt.Ioi_of_Ici⟩ := hasDerivWithinAt_Ioi_iff_Ici
#align has_deriv_within_at.Ici_of_Ioi HasDerivWithinAt.Ici_of_Ioi
#align has_deriv_within_at.Ioi_of_Ici HasDerivWithinAt.Ioi_of_Ici
@[simp]
theorem hasDerivWithinAt_Iio_iff_Iic [PartialOrder 𝕜] :
HasDerivWithinAt f f' (Iio x) x ↔ HasDerivWithinAt f f' (Iic x) x := by
rw [← Iic_diff_right, hasDerivWithinAt_diff_singleton]
#align has_deriv_within_at_Iio_iff_Iic hasDerivWithinAt_Iio_iff_Iic
alias ⟨HasDerivWithinAt.Iic_of_Iio, HasDerivWithinAt.Iio_of_Iic⟩ := hasDerivWithinAt_Iio_iff_Iic
#align has_deriv_within_at.Iic_of_Iio HasDerivWithinAt.Iic_of_Iio
#align has_deriv_within_at.Iio_of_Iic HasDerivWithinAt.Iio_of_Iic
theorem HasDerivWithinAt.Ioi_iff_Ioo [LinearOrder 𝕜] [OrderClosedTopology 𝕜] {x y : 𝕜} (h : x < y) :
HasDerivWithinAt f f' (Ioo x y) x ↔ HasDerivWithinAt f f' (Ioi x) x :=
hasFDerivWithinAt_inter <| Iio_mem_nhds h
#align has_deriv_within_at.Ioi_iff_Ioo HasDerivWithinAt.Ioi_iff_Ioo
alias ⟨HasDerivWithinAt.Ioi_of_Ioo, HasDerivWithinAt.Ioo_of_Ioi⟩ := HasDerivWithinAt.Ioi_iff_Ioo
#align has_deriv_within_at.Ioi_of_Ioo HasDerivWithinAt.Ioi_of_Ioo
#align has_deriv_within_at.Ioo_of_Ioi HasDerivWithinAt.Ioo_of_Ioi
theorem hasDerivAt_iff_isLittleO_nhds_zero :
HasDerivAt f f' x ↔ (fun h => f (x + h) - f x - h • f') =o[𝓝 0] fun h => h :=
hasFDerivAt_iff_isLittleO_nhds_zero
#align has_deriv_at_iff_is_o_nhds_zero hasDerivAt_iff_isLittleO_nhds_zero
theorem HasDerivAtFilter.mono (h : HasDerivAtFilter f f' x L₂) (hst : L₁ ≤ L₂) :
HasDerivAtFilter f f' x L₁ :=
HasFDerivAtFilter.mono h hst
#align has_deriv_at_filter.mono HasDerivAtFilter.mono
theorem HasDerivWithinAt.mono (h : HasDerivWithinAt f f' t x) (hst : s ⊆ t) :
HasDerivWithinAt f f' s x :=
HasFDerivWithinAt.mono h hst
#align has_deriv_within_at.mono HasDerivWithinAt.mono
theorem HasDerivWithinAt.mono_of_mem (h : HasDerivWithinAt f f' t x) (hst : t ∈ 𝓝[s] x) :
HasDerivWithinAt f f' s x :=
HasFDerivWithinAt.mono_of_mem h hst
#align has_deriv_within_at.mono_of_mem HasDerivWithinAt.mono_of_mem
#align has_deriv_within_at.nhds_within HasDerivWithinAt.mono_of_mem
theorem HasDerivAt.hasDerivAtFilter (h : HasDerivAt f f' x) (hL : L ≤ 𝓝 x) :
HasDerivAtFilter f f' x L :=
HasFDerivAt.hasFDerivAtFilter h hL
#align has_deriv_at.has_deriv_at_filter HasDerivAt.hasDerivAtFilter
theorem HasDerivAt.hasDerivWithinAt (h : HasDerivAt f f' x) : HasDerivWithinAt f f' s x :=
HasFDerivAt.hasFDerivWithinAt h
#align has_deriv_at.has_deriv_within_at HasDerivAt.hasDerivWithinAt
theorem HasDerivWithinAt.differentiableWithinAt (h : HasDerivWithinAt f f' s x) :
DifferentiableWithinAt 𝕜 f s x :=
HasFDerivWithinAt.differentiableWithinAt h
#align has_deriv_within_at.differentiable_within_at HasDerivWithinAt.differentiableWithinAt
theorem HasDerivAt.differentiableAt (h : HasDerivAt f f' x) : DifferentiableAt 𝕜 f x :=
HasFDerivAt.differentiableAt h
#align has_deriv_at.differentiable_at HasDerivAt.differentiableAt
@[simp]
theorem hasDerivWithinAt_univ : HasDerivWithinAt f f' univ x ↔ HasDerivAt f f' x :=
hasFDerivWithinAt_univ
#align has_deriv_within_at_univ hasDerivWithinAt_univ
theorem HasDerivAt.unique (h₀ : HasDerivAt f f₀' x) (h₁ : HasDerivAt f f₁' x) : f₀' = f₁' :=
smulRight_one_eq_iff.mp <| h₀.hasFDerivAt.unique h₁
#align has_deriv_at.unique HasDerivAt.unique
theorem hasDerivWithinAt_inter' (h : t ∈ 𝓝[s] x) :
HasDerivWithinAt f f' (s ∩ t) x ↔ HasDerivWithinAt f f' s x :=
hasFDerivWithinAt_inter' h
#align has_deriv_within_at_inter' hasDerivWithinAt_inter'
theorem hasDerivWithinAt_inter (h : t ∈ 𝓝 x) :
HasDerivWithinAt f f' (s ∩ t) x ↔ HasDerivWithinAt f f' s x :=
hasFDerivWithinAt_inter h
#align has_deriv_within_at_inter hasDerivWithinAt_inter
theorem HasDerivWithinAt.union (hs : HasDerivWithinAt f f' s x) (ht : HasDerivWithinAt f f' t x) :
HasDerivWithinAt f f' (s ∪ t) x :=
hs.hasFDerivWithinAt.union ht.hasFDerivWithinAt
#align has_deriv_within_at.union HasDerivWithinAt.union
theorem HasDerivWithinAt.hasDerivAt (h : HasDerivWithinAt f f' s x) (hs : s ∈ 𝓝 x) :
HasDerivAt f f' x :=
HasFDerivWithinAt.hasFDerivAt h hs
#align has_deriv_within_at.has_deriv_at HasDerivWithinAt.hasDerivAt
theorem DifferentiableWithinAt.hasDerivWithinAt (h : DifferentiableWithinAt 𝕜 f s x) :
HasDerivWithinAt f (derivWithin f s x) s x :=
h.hasFDerivWithinAt.hasDerivWithinAt
#align differentiable_within_at.has_deriv_within_at DifferentiableWithinAt.hasDerivWithinAt
theorem DifferentiableAt.hasDerivAt (h : DifferentiableAt 𝕜 f x) : HasDerivAt f (deriv f x) x :=
h.hasFDerivAt.hasDerivAt
#align differentiable_at.has_deriv_at DifferentiableAt.hasDerivAt
@[simp]
theorem hasDerivAt_deriv_iff : HasDerivAt f (deriv f x) x ↔ DifferentiableAt 𝕜 f x :=
⟨fun h => h.differentiableAt, fun h => h.hasDerivAt⟩
#align has_deriv_at_deriv_iff hasDerivAt_deriv_iff
@[simp]
theorem hasDerivWithinAt_derivWithin_iff :
HasDerivWithinAt f (derivWithin f s x) s x ↔ DifferentiableWithinAt 𝕜 f s x :=
⟨fun h => h.differentiableWithinAt, fun h => h.hasDerivWithinAt⟩
#align has_deriv_within_at_deriv_within_iff hasDerivWithinAt_derivWithin_iff
theorem DifferentiableOn.hasDerivAt (h : DifferentiableOn 𝕜 f s) (hs : s ∈ 𝓝 x) :
HasDerivAt f (deriv f x) x :=
(h.hasFDerivAt hs).hasDerivAt
#align differentiable_on.has_deriv_at DifferentiableOn.hasDerivAt
theorem HasDerivAt.deriv (h : HasDerivAt f f' x) : deriv f x = f' :=
h.differentiableAt.hasDerivAt.unique h
#align has_deriv_at.deriv HasDerivAt.deriv
theorem deriv_eq {f' : 𝕜 → F} (h : ∀ x, HasDerivAt f (f' x) x) : deriv f = f' :=
funext fun x => (h x).deriv
#align deriv_eq deriv_eq
theorem HasDerivWithinAt.derivWithin (h : HasDerivWithinAt f f' s x)
(hxs : UniqueDiffWithinAt 𝕜 s x) : derivWithin f s x = f' :=
hxs.eq_deriv _ h.differentiableWithinAt.hasDerivWithinAt h
#align has_deriv_within_at.deriv_within HasDerivWithinAt.derivWithin
theorem fderivWithin_derivWithin : (fderivWithin 𝕜 f s x : 𝕜 → F) 1 = derivWithin f s x :=
rfl
#align fderiv_within_deriv_within fderivWithin_derivWithin
theorem derivWithin_fderivWithin :
smulRight (1 : 𝕜 →L[𝕜] 𝕜) (derivWithin f s x) = fderivWithin 𝕜 f s x := by simp [derivWithin]
#align deriv_within_fderiv_within derivWithin_fderivWithin
theorem norm_derivWithin_eq_norm_fderivWithin : ‖derivWithin f s x‖ = ‖fderivWithin 𝕜 f s x‖ := by
simp [← derivWithin_fderivWithin]
theorem fderiv_deriv : (fderiv 𝕜 f x : 𝕜 → F) 1 = deriv f x :=
rfl
#align fderiv_deriv fderiv_deriv
theorem deriv_fderiv : smulRight (1 : 𝕜 →L[𝕜] 𝕜) (deriv f x) = fderiv 𝕜 f x := by simp [deriv]
#align deriv_fderiv deriv_fderiv
theorem norm_deriv_eq_norm_fderiv : ‖deriv f x‖ = ‖fderiv 𝕜 f x‖ := by
simp [← deriv_fderiv]
theorem DifferentiableAt.derivWithin (h : DifferentiableAt 𝕜 f x) (hxs : UniqueDiffWithinAt 𝕜 s x) :
derivWithin f s x = deriv f x := by
unfold derivWithin deriv
rw [h.fderivWithin hxs]
#align differentiable_at.deriv_within DifferentiableAt.derivWithin
theorem HasDerivWithinAt.deriv_eq_zero (hd : HasDerivWithinAt f 0 s x)
(H : UniqueDiffWithinAt 𝕜 s x) : deriv f x = 0 :=
(em' (DifferentiableAt 𝕜 f x)).elim deriv_zero_of_not_differentiableAt fun h =>
H.eq_deriv _ h.hasDerivAt.hasDerivWithinAt hd
#align has_deriv_within_at.deriv_eq_zero HasDerivWithinAt.deriv_eq_zero
theorem derivWithin_of_mem (st : t ∈ 𝓝[s] x) (ht : UniqueDiffWithinAt 𝕜 s x)
(h : DifferentiableWithinAt 𝕜 f t x) : derivWithin f s x = derivWithin f t x :=
((DifferentiableWithinAt.hasDerivWithinAt h).mono_of_mem st).derivWithin ht
#align deriv_within_of_mem derivWithin_of_mem
theorem derivWithin_subset (st : s ⊆ t) (ht : UniqueDiffWithinAt 𝕜 s x)
(h : DifferentiableWithinAt 𝕜 f t x) : derivWithin f s x = derivWithin f t x :=
((DifferentiableWithinAt.hasDerivWithinAt h).mono st).derivWithin ht
#align deriv_within_subset derivWithin_subset
theorem derivWithin_congr_set' (y : 𝕜) (h : s =ᶠ[𝓝[{y}ᶜ] x] t) :
derivWithin f s x = derivWithin f t x := by simp only [derivWithin, fderivWithin_congr_set' y h]
#align deriv_within_congr_set' derivWithin_congr_set'
theorem derivWithin_congr_set (h : s =ᶠ[𝓝 x] t) : derivWithin f s x = derivWithin f t x := by
simp only [derivWithin, fderivWithin_congr_set h]
#align deriv_within_congr_set derivWithin_congr_set
@[simp]
theorem derivWithin_univ : derivWithin f univ = deriv f := by
ext
unfold derivWithin deriv
rw [fderivWithin_univ]
#align deriv_within_univ derivWithin_univ
| Mathlib/Analysis/Calculus/Deriv/Basic.lean | 524 | 526 | theorem derivWithin_inter (ht : t ∈ 𝓝 x) : derivWithin f (s ∩ t) x = derivWithin f s x := by |
unfold derivWithin
rw [fderivWithin_inter ht]
|
/-
Copyright (c) 2018 Kevin Buzzard, Patrick Massot. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kevin Buzzard, Patrick Massot
This file is to a certain extent based on `quotient_module.lean` by Johannes Hölzl.
-/
import Mathlib.Algebra.Group.Subgroup.Finite
import Mathlib.Algebra.Group.Subgroup.Pointwise
import Mathlib.GroupTheory.Congruence.Basic
import Mathlib.GroupTheory.Coset
#align_import group_theory.quotient_group from "leanprover-community/mathlib"@"59694bd07f0a39c5beccba34bd9f413a160782bf"
/-!
# Quotients of groups by normal subgroups
This files develops the basic theory of quotients of groups by normal subgroups. In particular it
proves Noether's first and second isomorphism theorems.
## Main definitions
* `mk'`: the canonical group homomorphism `G →* G/N` given a normal subgroup `N` of `G`.
* `lift φ`: the group homomorphism `G/N →* H` given a group homomorphism `φ : G →* H` such that
`N ⊆ ker φ`.
* `map f`: the group homomorphism `G/N →* H/M` given a group homomorphism `f : G →* H` such that
`N ⊆ f⁻¹(M)`.
## Main statements
* `QuotientGroup.quotientKerEquivRange`: Noether's first isomorphism theorem, an explicit
isomorphism `G/ker φ → range φ` for every group homomorphism `φ : G →* H`.
* `QuotientGroup.quotientInfEquivProdNormalQuotient`: Noether's second isomorphism theorem, an
explicit isomorphism between `H/(H ∩ N)` and `(HN)/N` given a subgroup `H` and a normal subgroup
`N` of a group `G`.
* `QuotientGroup.quotientQuotientEquivQuotient`: Noether's third isomorphism theorem,
the canonical isomorphism between `(G / N) / (M / N)` and `G / M`, where `N ≤ M`.
## Tags
isomorphism theorems, quotient groups
-/
open Function
open scoped Pointwise
universe u v w x
namespace QuotientGroup
variable {G : Type u} [Group G] (N : Subgroup G) [nN : N.Normal] {H : Type v} [Group H]
{M : Type x} [Monoid M]
/-- The congruence relation generated by a normal subgroup. -/
@[to_additive "The additive congruence relation generated by a normal additive subgroup."]
protected def con : Con G where
toSetoid := leftRel N
mul' := @fun a b c d hab hcd => by
rw [leftRel_eq] at hab hcd ⊢
dsimp only
calc
(a * c)⁻¹ * (b * d) = c⁻¹ * (a⁻¹ * b) * c⁻¹⁻¹ * (c⁻¹ * d) := by
simp only [mul_inv_rev, mul_assoc, inv_mul_cancel_left]
_ ∈ N := N.mul_mem (nN.conj_mem _ hab _) hcd
#align quotient_group.con QuotientGroup.con
#align quotient_add_group.con QuotientAddGroup.con
@[to_additive]
instance Quotient.group : Group (G ⧸ N) :=
(QuotientGroup.con N).group
#align quotient_group.quotient.group QuotientGroup.Quotient.group
#align quotient_add_group.quotient.add_group QuotientAddGroup.Quotient.addGroup
/-- The group homomorphism from `G` to `G/N`. -/
@[to_additive "The additive group homomorphism from `G` to `G/N`."]
def mk' : G →* G ⧸ N :=
MonoidHom.mk' QuotientGroup.mk fun _ _ => rfl
#align quotient_group.mk' QuotientGroup.mk'
#align quotient_add_group.mk' QuotientAddGroup.mk'
@[to_additive (attr := simp)]
theorem coe_mk' : (mk' N : G → G ⧸ N) = mk :=
rfl
#align quotient_group.coe_mk' QuotientGroup.coe_mk'
#align quotient_add_group.coe_mk' QuotientAddGroup.coe_mk'
@[to_additive (attr := simp)]
theorem mk'_apply (x : G) : mk' N x = x :=
rfl
#align quotient_group.mk'_apply QuotientGroup.mk'_apply
#align quotient_add_group.mk'_apply QuotientAddGroup.mk'_apply
@[to_additive]
theorem mk'_surjective : Surjective <| mk' N :=
@mk_surjective _ _ N
#align quotient_group.mk'_surjective QuotientGroup.mk'_surjective
#align quotient_add_group.mk'_surjective QuotientAddGroup.mk'_surjective
@[to_additive]
theorem mk'_eq_mk' {x y : G} : mk' N x = mk' N y ↔ ∃ z ∈ N, x * z = y :=
QuotientGroup.eq'.trans <| by
simp only [← _root_.eq_inv_mul_iff_mul_eq, exists_prop, exists_eq_right]
#align quotient_group.mk'_eq_mk' QuotientGroup.mk'_eq_mk'
#align quotient_add_group.mk'_eq_mk' QuotientAddGroup.mk'_eq_mk'
open scoped Pointwise in
@[to_additive]
theorem sound (U : Set (G ⧸ N)) (g : N.op) :
g • (mk' N) ⁻¹' U = (mk' N) ⁻¹' U := by
ext x
simp only [Set.mem_preimage, Set.mem_smul_set_iff_inv_smul_mem]
congr! 1
exact Quotient.sound ⟨g⁻¹, rfl⟩
/-- Two `MonoidHom`s from a quotient group are equal if their compositions with
`QuotientGroup.mk'` are equal.
See note [partially-applied ext lemmas]. -/
@[to_additive (attr := ext 1100) "Two `AddMonoidHom`s from an additive quotient group are equal if
their compositions with `AddQuotientGroup.mk'` are equal.
See note [partially-applied ext lemmas]. "]
theorem monoidHom_ext ⦃f g : G ⧸ N →* M⦄ (h : f.comp (mk' N) = g.comp (mk' N)) : f = g :=
MonoidHom.ext fun x => QuotientGroup.induction_on x <| (DFunLike.congr_fun h : _)
#align quotient_group.monoid_hom_ext QuotientGroup.monoidHom_ext
#align quotient_add_group.add_monoid_hom_ext QuotientAddGroup.addMonoidHom_ext
@[to_additive (attr := simp)]
| Mathlib/GroupTheory/QuotientGroup.lean | 129 | 131 | theorem eq_one_iff {N : Subgroup G} [nN : N.Normal] (x : G) : (x : G ⧸ N) = 1 ↔ x ∈ N := by |
refine QuotientGroup.eq.trans ?_
rw [mul_one, Subgroup.inv_mem_iff]
|
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl
-/
import Aesop
import Mathlib.Order.BoundedOrder
#align_import order.disjoint from "leanprover-community/mathlib"@"22c4d2ff43714b6ff724b2745ccfdc0f236a4a76"
/-!
# Disjointness and complements
This file defines `Disjoint`, `Codisjoint`, and the `IsCompl` predicate.
## Main declarations
* `Disjoint x y`: two elements of a lattice are disjoint if their `inf` is the bottom element.
* `Codisjoint x y`: two elements of a lattice are codisjoint if their `join` is the top element.
* `IsCompl x y`: In a bounded lattice, predicate for "`x` is a complement of `y`". Note that in a
non distributive lattice, an element can have several complements.
* `ComplementedLattice α`: Typeclass stating that any element of a lattice has a complement.
-/
open Function
variable {α : Type*}
section Disjoint
section PartialOrderBot
variable [PartialOrder α] [OrderBot α] {a b c d : α}
/-- Two elements of a lattice are disjoint if their inf is the bottom element.
(This generalizes disjoint sets, viewed as members of the subset lattice.)
Note that we define this without reference to `⊓`, as this allows us to talk about orders where
the infimum is not unique, or where implementing `Inf` would require additional `Decidable`
arguments. -/
def Disjoint (a b : α) : Prop :=
∀ ⦃x⦄, x ≤ a → x ≤ b → x ≤ ⊥
#align disjoint Disjoint
@[simp]
theorem disjoint_of_subsingleton [Subsingleton α] : Disjoint a b :=
fun x _ _ ↦ le_of_eq (Subsingleton.elim x ⊥)
theorem disjoint_comm : Disjoint a b ↔ Disjoint b a :=
forall_congr' fun _ ↦ forall_swap
#align disjoint.comm disjoint_comm
@[symm]
theorem Disjoint.symm ⦃a b : α⦄ : Disjoint a b → Disjoint b a :=
disjoint_comm.1
#align disjoint.symm Disjoint.symm
theorem symmetric_disjoint : Symmetric (Disjoint : α → α → Prop) :=
Disjoint.symm
#align symmetric_disjoint symmetric_disjoint
@[simp]
theorem disjoint_bot_left : Disjoint ⊥ a := fun _ hbot _ ↦ hbot
#align disjoint_bot_left disjoint_bot_left
@[simp]
theorem disjoint_bot_right : Disjoint a ⊥ := fun _ _ hbot ↦ hbot
#align disjoint_bot_right disjoint_bot_right
theorem Disjoint.mono (h₁ : a ≤ b) (h₂ : c ≤ d) : Disjoint b d → Disjoint a c :=
fun h _ ha hc ↦ h (ha.trans h₁) (hc.trans h₂)
#align disjoint.mono Disjoint.mono
theorem Disjoint.mono_left (h : a ≤ b) : Disjoint b c → Disjoint a c :=
Disjoint.mono h le_rfl
#align disjoint.mono_left Disjoint.mono_left
theorem Disjoint.mono_right : b ≤ c → Disjoint a c → Disjoint a b :=
Disjoint.mono le_rfl
#align disjoint.mono_right Disjoint.mono_right
@[simp]
theorem disjoint_self : Disjoint a a ↔ a = ⊥ :=
⟨fun hd ↦ bot_unique <| hd le_rfl le_rfl, fun h _ ha _ ↦ ha.trans_eq h⟩
#align disjoint_self disjoint_self
/- TODO: Rename `Disjoint.eq_bot` to `Disjoint.inf_eq` and `Disjoint.eq_bot_of_self` to
`Disjoint.eq_bot` -/
alias ⟨Disjoint.eq_bot_of_self, _⟩ := disjoint_self
#align disjoint.eq_bot_of_self Disjoint.eq_bot_of_self
theorem Disjoint.ne (ha : a ≠ ⊥) (hab : Disjoint a b) : a ≠ b :=
fun h ↦ ha <| disjoint_self.1 <| by rwa [← h] at hab
#align disjoint.ne Disjoint.ne
theorem Disjoint.eq_bot_of_le (hab : Disjoint a b) (h : a ≤ b) : a = ⊥ :=
eq_bot_iff.2 <| hab le_rfl h
#align disjoint.eq_bot_of_le Disjoint.eq_bot_of_le
theorem Disjoint.eq_bot_of_ge (hab : Disjoint a b) : b ≤ a → b = ⊥ :=
hab.symm.eq_bot_of_le
#align disjoint.eq_bot_of_ge Disjoint.eq_bot_of_ge
lemma Disjoint.eq_iff (hab : Disjoint a b) : a = b ↔ a = ⊥ ∧ b = ⊥ := by aesop
lemma Disjoint.ne_iff (hab : Disjoint a b) : a ≠ b ↔ a ≠ ⊥ ∨ b ≠ ⊥ :=
hab.eq_iff.not.trans not_and_or
end PartialOrderBot
section PartialBoundedOrder
variable [PartialOrder α] [BoundedOrder α] {a : α}
@[simp]
theorem disjoint_top : Disjoint a ⊤ ↔ a = ⊥ :=
⟨fun h ↦ bot_unique <| h le_rfl le_top, fun h _ ha _ ↦ ha.trans_eq h⟩
#align disjoint_top disjoint_top
@[simp]
theorem top_disjoint : Disjoint ⊤ a ↔ a = ⊥ :=
⟨fun h ↦ bot_unique <| h le_top le_rfl, fun h _ _ ha ↦ ha.trans_eq h⟩
#align top_disjoint top_disjoint
end PartialBoundedOrder
section SemilatticeInfBot
variable [SemilatticeInf α] [OrderBot α] {a b c d : α}
theorem disjoint_iff_inf_le : Disjoint a b ↔ a ⊓ b ≤ ⊥ :=
⟨fun hd ↦ hd inf_le_left inf_le_right, fun h _ ha hb ↦ (le_inf ha hb).trans h⟩
#align disjoint_iff_inf_le disjoint_iff_inf_le
theorem disjoint_iff : Disjoint a b ↔ a ⊓ b = ⊥ :=
disjoint_iff_inf_le.trans le_bot_iff
#align disjoint_iff disjoint_iff
theorem Disjoint.le_bot : Disjoint a b → a ⊓ b ≤ ⊥ :=
disjoint_iff_inf_le.mp
#align disjoint.le_bot Disjoint.le_bot
theorem Disjoint.eq_bot : Disjoint a b → a ⊓ b = ⊥ :=
bot_unique ∘ Disjoint.le_bot
#align disjoint.eq_bot Disjoint.eq_bot
theorem disjoint_assoc : Disjoint (a ⊓ b) c ↔ Disjoint a (b ⊓ c) := by
rw [disjoint_iff_inf_le, disjoint_iff_inf_le, inf_assoc]
#align disjoint_assoc disjoint_assoc
theorem disjoint_left_comm : Disjoint a (b ⊓ c) ↔ Disjoint b (a ⊓ c) := by
simp_rw [disjoint_iff_inf_le, inf_left_comm]
#align disjoint_left_comm disjoint_left_comm
theorem disjoint_right_comm : Disjoint (a ⊓ b) c ↔ Disjoint (a ⊓ c) b := by
simp_rw [disjoint_iff_inf_le, inf_right_comm]
#align disjoint_right_comm disjoint_right_comm
variable (c)
theorem Disjoint.inf_left (h : Disjoint a b) : Disjoint (a ⊓ c) b :=
h.mono_left inf_le_left
#align disjoint.inf_left Disjoint.inf_left
theorem Disjoint.inf_left' (h : Disjoint a b) : Disjoint (c ⊓ a) b :=
h.mono_left inf_le_right
#align disjoint.inf_left' Disjoint.inf_left'
theorem Disjoint.inf_right (h : Disjoint a b) : Disjoint a (b ⊓ c) :=
h.mono_right inf_le_left
#align disjoint.inf_right Disjoint.inf_right
theorem Disjoint.inf_right' (h : Disjoint a b) : Disjoint a (c ⊓ b) :=
h.mono_right inf_le_right
#align disjoint.inf_right' Disjoint.inf_right'
variable {c}
theorem Disjoint.of_disjoint_inf_of_le (h : Disjoint (a ⊓ b) c) (hle : a ≤ c) : Disjoint a b :=
disjoint_iff.2 <| h.eq_bot_of_le <| inf_le_of_left_le hle
#align disjoint.of_disjoint_inf_of_le Disjoint.of_disjoint_inf_of_le
theorem Disjoint.of_disjoint_inf_of_le' (h : Disjoint (a ⊓ b) c) (hle : b ≤ c) : Disjoint a b :=
disjoint_iff.2 <| h.eq_bot_of_le <| inf_le_of_right_le hle
#align disjoint.of_disjoint_inf_of_le' Disjoint.of_disjoint_inf_of_le'
end SemilatticeInfBot
section DistribLatticeBot
variable [DistribLattice α] [OrderBot α] {a b c : α}
@[simp]
theorem disjoint_sup_left : Disjoint (a ⊔ b) c ↔ Disjoint a c ∧ Disjoint b c := by
simp only [disjoint_iff, inf_sup_right, sup_eq_bot_iff]
#align disjoint_sup_left disjoint_sup_left
@[simp]
theorem disjoint_sup_right : Disjoint a (b ⊔ c) ↔ Disjoint a b ∧ Disjoint a c := by
simp only [disjoint_iff, inf_sup_left, sup_eq_bot_iff]
#align disjoint_sup_right disjoint_sup_right
theorem Disjoint.sup_left (ha : Disjoint a c) (hb : Disjoint b c) : Disjoint (a ⊔ b) c :=
disjoint_sup_left.2 ⟨ha, hb⟩
#align disjoint.sup_left Disjoint.sup_left
theorem Disjoint.sup_right (hb : Disjoint a b) (hc : Disjoint a c) : Disjoint a (b ⊔ c) :=
disjoint_sup_right.2 ⟨hb, hc⟩
#align disjoint.sup_right Disjoint.sup_right
theorem Disjoint.left_le_of_le_sup_right (h : a ≤ b ⊔ c) (hd : Disjoint a c) : a ≤ b :=
le_of_inf_le_sup_le (le_trans hd.le_bot bot_le) <| sup_le h le_sup_right
#align disjoint.left_le_of_le_sup_right Disjoint.left_le_of_le_sup_right
theorem Disjoint.left_le_of_le_sup_left (h : a ≤ c ⊔ b) (hd : Disjoint a c) : a ≤ b :=
hd.left_le_of_le_sup_right <| by rwa [sup_comm]
#align disjoint.left_le_of_le_sup_left Disjoint.left_le_of_le_sup_left
end DistribLatticeBot
end Disjoint
section Codisjoint
section PartialOrderTop
variable [PartialOrder α] [OrderTop α] {a b c d : α}
/-- Two elements of a lattice are codisjoint if their sup is the top element.
Note that we define this without reference to `⊔`, as this allows us to talk about orders where
the supremum is not unique, or where implement `Sup` would require additional `Decidable`
arguments. -/
def Codisjoint (a b : α) : Prop :=
∀ ⦃x⦄, a ≤ x → b ≤ x → ⊤ ≤ x
#align codisjoint Codisjoint
theorem Codisjoint_comm : Codisjoint a b ↔ Codisjoint b a :=
forall_congr' fun _ ↦ forall_swap
#align codisjoint.comm Codisjoint_comm
@[symm]
theorem Codisjoint.symm ⦃a b : α⦄ : Codisjoint a b → Codisjoint b a :=
Codisjoint_comm.1
#align codisjoint.symm Codisjoint.symm
theorem symmetric_codisjoint : Symmetric (Codisjoint : α → α → Prop) :=
Codisjoint.symm
#align symmetric_codisjoint symmetric_codisjoint
@[simp]
theorem codisjoint_top_left : Codisjoint ⊤ a := fun _ htop _ ↦ htop
#align codisjoint_top_left codisjoint_top_left
@[simp]
theorem codisjoint_top_right : Codisjoint a ⊤ := fun _ _ htop ↦ htop
#align codisjoint_top_right codisjoint_top_right
theorem Codisjoint.mono (h₁ : a ≤ b) (h₂ : c ≤ d) : Codisjoint a c → Codisjoint b d :=
fun h _ ha hc ↦ h (h₁.trans ha) (h₂.trans hc)
#align codisjoint.mono Codisjoint.mono
theorem Codisjoint.mono_left (h : a ≤ b) : Codisjoint a c → Codisjoint b c :=
Codisjoint.mono h le_rfl
#align codisjoint.mono_left Codisjoint.mono_left
theorem Codisjoint.mono_right : b ≤ c → Codisjoint a b → Codisjoint a c :=
Codisjoint.mono le_rfl
#align codisjoint.mono_right Codisjoint.mono_right
@[simp]
theorem codisjoint_self : Codisjoint a a ↔ a = ⊤ :=
⟨fun hd ↦ top_unique <| hd le_rfl le_rfl, fun h _ ha _ ↦ h.symm.trans_le ha⟩
#align codisjoint_self codisjoint_self
/- TODO: Rename `Codisjoint.eq_top` to `Codisjoint.sup_eq` and `Codisjoint.eq_top_of_self` to
`Codisjoint.eq_top` -/
alias ⟨Codisjoint.eq_top_of_self, _⟩ := codisjoint_self
#align codisjoint.eq_top_of_self Codisjoint.eq_top_of_self
theorem Codisjoint.ne (ha : a ≠ ⊤) (hab : Codisjoint a b) : a ≠ b :=
fun h ↦ ha <| codisjoint_self.1 <| by rwa [← h] at hab
#align codisjoint.ne Codisjoint.ne
theorem Codisjoint.eq_top_of_le (hab : Codisjoint a b) (h : b ≤ a) : a = ⊤ :=
eq_top_iff.2 <| hab le_rfl h
#align codisjoint.eq_top_of_le Codisjoint.eq_top_of_le
theorem Codisjoint.eq_top_of_ge (hab : Codisjoint a b) : a ≤ b → b = ⊤ :=
hab.symm.eq_top_of_le
#align codisjoint.eq_top_of_ge Codisjoint.eq_top_of_ge
lemma Codisjoint.eq_iff (hab : Codisjoint a b) : a = b ↔ a = ⊤ ∧ b = ⊤ := by aesop
lemma Codisjoint.ne_iff (hab : Codisjoint a b) : a ≠ b ↔ a ≠ ⊤ ∨ b ≠ ⊤ :=
hab.eq_iff.not.trans not_and_or
end PartialOrderTop
section PartialBoundedOrder
variable [PartialOrder α] [BoundedOrder α] {a b : α}
@[simp]
theorem codisjoint_bot : Codisjoint a ⊥ ↔ a = ⊤ :=
⟨fun h ↦ top_unique <| h le_rfl bot_le, fun h _ ha _ ↦ h.symm.trans_le ha⟩
#align codisjoint_bot codisjoint_bot
@[simp]
theorem bot_codisjoint : Codisjoint ⊥ a ↔ a = ⊤ :=
⟨fun h ↦ top_unique <| h bot_le le_rfl, fun h _ _ ha ↦ h.symm.trans_le ha⟩
#align bot_codisjoint bot_codisjoint
lemma Codisjoint.ne_bot_of_ne_top (h : Codisjoint a b) (ha : a ≠ ⊤) : b ≠ ⊥ := by
rintro rfl; exact ha <| by simpa using h
lemma Codisjoint.ne_bot_of_ne_top' (h : Codisjoint a b) (hb : b ≠ ⊤) : a ≠ ⊥ := by
rintro rfl; exact hb <| by simpa using h
end PartialBoundedOrder
section SemilatticeSupTop
variable [SemilatticeSup α] [OrderTop α] {a b c d : α}
theorem codisjoint_iff_le_sup : Codisjoint a b ↔ ⊤ ≤ a ⊔ b :=
@disjoint_iff_inf_le αᵒᵈ _ _ _ _
#align codisjoint_iff_le_sup codisjoint_iff_le_sup
theorem codisjoint_iff : Codisjoint a b ↔ a ⊔ b = ⊤ :=
@disjoint_iff αᵒᵈ _ _ _ _
#align codisjoint_iff codisjoint_iff
theorem Codisjoint.top_le : Codisjoint a b → ⊤ ≤ a ⊔ b :=
@Disjoint.le_bot αᵒᵈ _ _ _ _
#align codisjoint.top_le Codisjoint.top_le
theorem Codisjoint.eq_top : Codisjoint a b → a ⊔ b = ⊤ :=
@Disjoint.eq_bot αᵒᵈ _ _ _ _
#align codisjoint.eq_top Codisjoint.eq_top
theorem codisjoint_assoc : Codisjoint (a ⊔ b) c ↔ Codisjoint a (b ⊔ c) :=
@disjoint_assoc αᵒᵈ _ _ _ _ _
#align codisjoint_assoc codisjoint_assoc
theorem codisjoint_left_comm : Codisjoint a (b ⊔ c) ↔ Codisjoint b (a ⊔ c) :=
@disjoint_left_comm αᵒᵈ _ _ _ _ _
#align codisjoint_left_comm codisjoint_left_comm
theorem codisjoint_right_comm : Codisjoint (a ⊔ b) c ↔ Codisjoint (a ⊔ c) b :=
@disjoint_right_comm αᵒᵈ _ _ _ _ _
#align codisjoint_right_comm codisjoint_right_comm
variable (c)
theorem Codisjoint.sup_left (h : Codisjoint a b) : Codisjoint (a ⊔ c) b :=
h.mono_left le_sup_left
#align codisjoint.sup_left Codisjoint.sup_left
theorem Codisjoint.sup_left' (h : Codisjoint a b) : Codisjoint (c ⊔ a) b :=
h.mono_left le_sup_right
#align codisjoint.sup_left' Codisjoint.sup_left'
theorem Codisjoint.sup_right (h : Codisjoint a b) : Codisjoint a (b ⊔ c) :=
h.mono_right le_sup_left
#align codisjoint.sup_right Codisjoint.sup_right
theorem Codisjoint.sup_right' (h : Codisjoint a b) : Codisjoint a (c ⊔ b) :=
h.mono_right le_sup_right
#align codisjoint.sup_right' Codisjoint.sup_right'
variable {c}
theorem Codisjoint.of_codisjoint_sup_of_le (h : Codisjoint (a ⊔ b) c) (hle : c ≤ a) :
Codisjoint a b :=
@Disjoint.of_disjoint_inf_of_le αᵒᵈ _ _ _ _ _ h hle
#align codisjoint.of_codisjoint_sup_of_le Codisjoint.of_codisjoint_sup_of_le
theorem Codisjoint.of_codisjoint_sup_of_le' (h : Codisjoint (a ⊔ b) c) (hle : c ≤ b) :
Codisjoint a b :=
@Disjoint.of_disjoint_inf_of_le' αᵒᵈ _ _ _ _ _ h hle
#align codisjoint.of_codisjoint_sup_of_le' Codisjoint.of_codisjoint_sup_of_le'
end SemilatticeSupTop
section DistribLatticeTop
variable [DistribLattice α] [OrderTop α] {a b c : α}
@[simp]
theorem codisjoint_inf_left : Codisjoint (a ⊓ b) c ↔ Codisjoint a c ∧ Codisjoint b c := by
simp only [codisjoint_iff, sup_inf_right, inf_eq_top_iff]
#align codisjoint_inf_left codisjoint_inf_left
@[simp]
theorem codisjoint_inf_right : Codisjoint a (b ⊓ c) ↔ Codisjoint a b ∧ Codisjoint a c := by
simp only [codisjoint_iff, sup_inf_left, inf_eq_top_iff]
#align codisjoint_inf_right codisjoint_inf_right
theorem Codisjoint.inf_left (ha : Codisjoint a c) (hb : Codisjoint b c) : Codisjoint (a ⊓ b) c :=
codisjoint_inf_left.2 ⟨ha, hb⟩
#align codisjoint.inf_left Codisjoint.inf_left
theorem Codisjoint.inf_right (hb : Codisjoint a b) (hc : Codisjoint a c) : Codisjoint a (b ⊓ c) :=
codisjoint_inf_right.2 ⟨hb, hc⟩
#align codisjoint.inf_right Codisjoint.inf_right
theorem Codisjoint.left_le_of_le_inf_right (h : a ⊓ b ≤ c) (hd : Codisjoint b c) : a ≤ c :=
@Disjoint.left_le_of_le_sup_right αᵒᵈ _ _ _ _ _ h hd.symm
#align codisjoint.left_le_of_le_inf_right Codisjoint.left_le_of_le_inf_right
theorem Codisjoint.left_le_of_le_inf_left (h : b ⊓ a ≤ c) (hd : Codisjoint b c) : a ≤ c :=
hd.left_le_of_le_inf_right <| by rwa [inf_comm]
#align codisjoint.left_le_of_le_inf_left Codisjoint.left_le_of_le_inf_left
end DistribLatticeTop
end Codisjoint
open OrderDual
theorem Disjoint.dual [SemilatticeInf α] [OrderBot α] {a b : α} :
Disjoint a b → Codisjoint (toDual a) (toDual b) :=
id
#align disjoint.dual Disjoint.dual
theorem Codisjoint.dual [SemilatticeSup α] [OrderTop α] {a b : α} :
Codisjoint a b → Disjoint (toDual a) (toDual b) :=
id
#align codisjoint.dual Codisjoint.dual
@[simp]
theorem disjoint_toDual_iff [SemilatticeSup α] [OrderTop α] {a b : α} :
Disjoint (toDual a) (toDual b) ↔ Codisjoint a b :=
Iff.rfl
#align disjoint_to_dual_iff disjoint_toDual_iff
@[simp]
theorem disjoint_ofDual_iff [SemilatticeInf α] [OrderBot α] {a b : αᵒᵈ} :
Disjoint (ofDual a) (ofDual b) ↔ Codisjoint a b :=
Iff.rfl
#align disjoint_of_dual_iff disjoint_ofDual_iff
@[simp]
theorem codisjoint_toDual_iff [SemilatticeInf α] [OrderBot α] {a b : α} :
Codisjoint (toDual a) (toDual b) ↔ Disjoint a b :=
Iff.rfl
#align codisjoint_to_dual_iff codisjoint_toDual_iff
@[simp]
theorem codisjoint_ofDual_iff [SemilatticeSup α] [OrderTop α] {a b : αᵒᵈ} :
Codisjoint (ofDual a) (ofDual b) ↔ Disjoint a b :=
Iff.rfl
#align codisjoint_of_dual_iff codisjoint_ofDual_iff
section DistribLattice
variable [DistribLattice α] [BoundedOrder α] {a b c : α}
theorem Disjoint.le_of_codisjoint (hab : Disjoint a b) (hbc : Codisjoint b c) : a ≤ c := by
rw [← @inf_top_eq _ _ _ a, ← @bot_sup_eq _ _ _ c, ← hab.eq_bot, ← hbc.eq_top, sup_inf_right]
exact inf_le_inf_right _ le_sup_left
#align disjoint.le_of_codisjoint Disjoint.le_of_codisjoint
end DistribLattice
section IsCompl
/-- Two elements `x` and `y` are complements of each other if `x ⊔ y = ⊤` and `x ⊓ y = ⊥`. -/
structure IsCompl [PartialOrder α] [BoundedOrder α] (x y : α) : Prop where
/-- If `x` and `y` are to be complementary in an order, they should be disjoint. -/
protected disjoint : Disjoint x y
/-- If `x` and `y` are to be complementary in an order, they should be codisjoint. -/
protected codisjoint : Codisjoint x y
#align is_compl IsCompl
theorem isCompl_iff [PartialOrder α] [BoundedOrder α] {a b : α} :
IsCompl a b ↔ Disjoint a b ∧ Codisjoint a b :=
⟨fun h ↦ ⟨h.1, h.2⟩, fun h ↦ ⟨h.1, h.2⟩⟩
#align is_compl_iff isCompl_iff
namespace IsCompl
section BoundedPartialOrder
variable [PartialOrder α] [BoundedOrder α] {x y z : α}
@[symm]
protected theorem symm (h : IsCompl x y) : IsCompl y x :=
⟨h.1.symm, h.2.symm⟩
#align is_compl.symm IsCompl.symm
lemma _root_.isCompl_comm : IsCompl x y ↔ IsCompl y x := ⟨IsCompl.symm, IsCompl.symm⟩
theorem dual (h : IsCompl x y) : IsCompl (toDual x) (toDual y) :=
⟨h.2, h.1⟩
#align is_compl.dual IsCompl.dual
theorem ofDual {a b : αᵒᵈ} (h : IsCompl a b) : IsCompl (ofDual a) (ofDual b) :=
⟨h.2, h.1⟩
#align is_compl.of_dual IsCompl.ofDual
end BoundedPartialOrder
section BoundedLattice
variable [Lattice α] [BoundedOrder α] {x y z : α}
theorem of_le (h₁ : x ⊓ y ≤ ⊥) (h₂ : ⊤ ≤ x ⊔ y) : IsCompl x y :=
⟨disjoint_iff_inf_le.mpr h₁, codisjoint_iff_le_sup.mpr h₂⟩
#align is_compl.of_le IsCompl.of_le
theorem of_eq (h₁ : x ⊓ y = ⊥) (h₂ : x ⊔ y = ⊤) : IsCompl x y :=
⟨disjoint_iff.mpr h₁, codisjoint_iff.mpr h₂⟩
#align is_compl.of_eq IsCompl.of_eq
theorem inf_eq_bot (h : IsCompl x y) : x ⊓ y = ⊥ :=
h.disjoint.eq_bot
#align is_compl.inf_eq_bot IsCompl.inf_eq_bot
theorem sup_eq_top (h : IsCompl x y) : x ⊔ y = ⊤ :=
h.codisjoint.eq_top
#align is_compl.sup_eq_top IsCompl.sup_eq_top
end BoundedLattice
variable [DistribLattice α] [BoundedOrder α] {a b x y z : α}
theorem inf_left_le_of_le_sup_right (h : IsCompl x y) (hle : a ≤ b ⊔ y) : a ⊓ x ≤ b :=
calc
a ⊓ x ≤ (b ⊔ y) ⊓ x := inf_le_inf hle le_rfl
_ = b ⊓ x ⊔ y ⊓ x := inf_sup_right _ _ _
_ = b ⊓ x := by rw [h.symm.inf_eq_bot, sup_bot_eq]
_ ≤ b := inf_le_left
#align is_compl.inf_left_le_of_le_sup_right IsCompl.inf_left_le_of_le_sup_right
theorem le_sup_right_iff_inf_left_le {a b} (h : IsCompl x y) : a ≤ b ⊔ y ↔ a ⊓ x ≤ b :=
⟨h.inf_left_le_of_le_sup_right, h.symm.dual.inf_left_le_of_le_sup_right⟩
#align is_compl.le_sup_right_iff_inf_left_le IsCompl.le_sup_right_iff_inf_left_le
| Mathlib/Order/Disjoint.lean | 540 | 541 | theorem inf_left_eq_bot_iff (h : IsCompl y z) : x ⊓ y = ⊥ ↔ x ≤ z := by |
rw [← le_bot_iff, ← h.le_sup_right_iff_inf_left_le, bot_sup_eq]
|
/-
Copyright (c) 2018 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Jens Wagemaker, Aaron Anderson
-/
import Mathlib.Algebra.BigOperators.Associated
import Mathlib.Algebra.GCDMonoid.Basic
import Mathlib.Data.Finsupp.Multiset
import Mathlib.Data.Nat.Factors
import Mathlib.RingTheory.Noetherian
import Mathlib.RingTheory.Multiplicity
#align_import ring_theory.unique_factorization_domain from "leanprover-community/mathlib"@"570e9f4877079b3a923135b3027ac3be8695ab8c"
/-!
# Unique factorization
## Main Definitions
* `WfDvdMonoid` holds for `Monoid`s for which a strict divisibility relation is
well-founded.
* `UniqueFactorizationMonoid` holds for `WfDvdMonoid`s where
`Irreducible` is equivalent to `Prime`
## To do
* set up the complete lattice structure on `FactorSet`.
-/
variable {α : Type*}
local infixl:50 " ~ᵤ " => Associated
/-- Well-foundedness of the strict version of |, which is equivalent to the descending chain
condition on divisibility and to the ascending chain condition on
principal ideals in an integral domain.
-/
class WfDvdMonoid (α : Type*) [CommMonoidWithZero α] : Prop where
wellFounded_dvdNotUnit : WellFounded (@DvdNotUnit α _)
#align wf_dvd_monoid WfDvdMonoid
export WfDvdMonoid (wellFounded_dvdNotUnit)
-- see Note [lower instance priority]
instance (priority := 100) IsNoetherianRing.wfDvdMonoid [CommRing α] [IsDomain α]
[IsNoetherianRing α] : WfDvdMonoid α :=
⟨by
convert InvImage.wf (fun a => Ideal.span ({a} : Set α)) (wellFounded_submodule_gt _ _)
ext
exact Ideal.span_singleton_lt_span_singleton.symm⟩
#align is_noetherian_ring.wf_dvd_monoid IsNoetherianRing.wfDvdMonoid
namespace WfDvdMonoid
variable [CommMonoidWithZero α]
open Associates Nat
theorem of_wfDvdMonoid_associates (_ : WfDvdMonoid (Associates α)) : WfDvdMonoid α :=
⟨(mk_surjective.wellFounded_iff mk_dvdNotUnit_mk_iff.symm).2 wellFounded_dvdNotUnit⟩
#align wf_dvd_monoid.of_wf_dvd_monoid_associates WfDvdMonoid.of_wfDvdMonoid_associates
variable [WfDvdMonoid α]
instance wfDvdMonoid_associates : WfDvdMonoid (Associates α) :=
⟨(mk_surjective.wellFounded_iff mk_dvdNotUnit_mk_iff.symm).1 wellFounded_dvdNotUnit⟩
#align wf_dvd_monoid.wf_dvd_monoid_associates WfDvdMonoid.wfDvdMonoid_associates
theorem wellFounded_associates : WellFounded ((· < ·) : Associates α → Associates α → Prop) :=
Subrelation.wf dvdNotUnit_of_lt wellFounded_dvdNotUnit
#align wf_dvd_monoid.well_founded_associates WfDvdMonoid.wellFounded_associates
-- Porting note: elab_as_elim can only be global and cannot be changed on an imported decl
-- attribute [local elab_as_elim] WellFounded.fix
theorem exists_irreducible_factor {a : α} (ha : ¬IsUnit a) (ha0 : a ≠ 0) :
∃ i, Irreducible i ∧ i ∣ a :=
let ⟨b, hs, hr⟩ := wellFounded_dvdNotUnit.has_min { b | b ∣ a ∧ ¬IsUnit b } ⟨a, dvd_rfl, ha⟩
⟨b,
⟨hs.2, fun c d he =>
let h := dvd_trans ⟨d, he⟩ hs.1
or_iff_not_imp_left.2 fun hc =>
of_not_not fun hd => hr c ⟨h, hc⟩ ⟨ne_zero_of_dvd_ne_zero ha0 h, d, hd, he⟩⟩,
hs.1⟩
#align wf_dvd_monoid.exists_irreducible_factor WfDvdMonoid.exists_irreducible_factor
@[elab_as_elim]
theorem induction_on_irreducible {P : α → Prop} (a : α) (h0 : P 0) (hu : ∀ u : α, IsUnit u → P u)
(hi : ∀ a i : α, a ≠ 0 → Irreducible i → P a → P (i * a)) : P a :=
haveI := Classical.dec
wellFounded_dvdNotUnit.fix
(fun a ih =>
if ha0 : a = 0 then ha0.substr h0
else
if hau : IsUnit a then hu a hau
else
let ⟨i, hii, b, hb⟩ := exists_irreducible_factor hau ha0
let hb0 : b ≠ 0 := ne_zero_of_dvd_ne_zero ha0 ⟨i, mul_comm i b ▸ hb⟩
hb.symm ▸ hi b i hb0 hii <| ih b ⟨hb0, i, hii.1, mul_comm i b ▸ hb⟩)
a
#align wf_dvd_monoid.induction_on_irreducible WfDvdMonoid.induction_on_irreducible
theorem exists_factors (a : α) :
a ≠ 0 → ∃ f : Multiset α, (∀ b ∈ f, Irreducible b) ∧ Associated f.prod a :=
induction_on_irreducible a (fun h => (h rfl).elim)
(fun u hu _ => ⟨0, fun _ h => False.elim (Multiset.not_mem_zero _ h), hu.unit, one_mul _⟩)
fun a i ha0 hi ih _ =>
let ⟨s, hs⟩ := ih ha0
⟨i ::ₘ s, fun b H => (Multiset.mem_cons.1 H).elim (fun h => h.symm ▸ hi) (hs.1 b), by
rw [s.prod_cons i]
exact hs.2.mul_left i⟩
#align wf_dvd_monoid.exists_factors WfDvdMonoid.exists_factors
theorem not_unit_iff_exists_factors_eq (a : α) (hn0 : a ≠ 0) :
¬IsUnit a ↔ ∃ f : Multiset α, (∀ b ∈ f, Irreducible b) ∧ f.prod = a ∧ f ≠ ∅ :=
⟨fun hnu => by
obtain ⟨f, hi, u, rfl⟩ := exists_factors a hn0
obtain ⟨b, h⟩ := Multiset.exists_mem_of_ne_zero fun h : f = 0 => hnu <| by simp [h]
classical
refine ⟨(f.erase b).cons (b * u), fun a ha => ?_, ?_, Multiset.cons_ne_zero⟩
· obtain rfl | ha := Multiset.mem_cons.1 ha
exacts [Associated.irreducible ⟨u, rfl⟩ (hi b h), hi a (Multiset.mem_of_mem_erase ha)]
· rw [Multiset.prod_cons, mul_comm b, mul_assoc, Multiset.prod_erase h, mul_comm],
fun ⟨f, hi, he, hne⟩ =>
let ⟨b, h⟩ := Multiset.exists_mem_of_ne_zero hne
not_isUnit_of_not_isUnit_dvd (hi b h).not_unit <| he ▸ Multiset.dvd_prod h⟩
#align wf_dvd_monoid.not_unit_iff_exists_factors_eq WfDvdMonoid.not_unit_iff_exists_factors_eq
theorem isRelPrime_of_no_irreducible_factors {x y : α} (nonzero : ¬(x = 0 ∧ y = 0))
(H : ∀ z : α, Irreducible z → z ∣ x → ¬z ∣ y) : IsRelPrime x y :=
isRelPrime_of_no_nonunits_factors nonzero fun _z znu znz zx zy ↦
have ⟨i, h1, h2⟩ := exists_irreducible_factor znu znz
H i h1 (h2.trans zx) (h2.trans zy)
end WfDvdMonoid
theorem WfDvdMonoid.of_wellFounded_associates [CancelCommMonoidWithZero α]
(h : WellFounded ((· < ·) : Associates α → Associates α → Prop)) : WfDvdMonoid α :=
WfDvdMonoid.of_wfDvdMonoid_associates
⟨by
convert h
ext
exact Associates.dvdNotUnit_iff_lt⟩
#align wf_dvd_monoid.of_well_founded_associates WfDvdMonoid.of_wellFounded_associates
theorem WfDvdMonoid.iff_wellFounded_associates [CancelCommMonoidWithZero α] :
WfDvdMonoid α ↔ WellFounded ((· < ·) : Associates α → Associates α → Prop) :=
⟨by apply WfDvdMonoid.wellFounded_associates, WfDvdMonoid.of_wellFounded_associates⟩
#align wf_dvd_monoid.iff_well_founded_associates WfDvdMonoid.iff_wellFounded_associates
theorem WfDvdMonoid.max_power_factor' [CommMonoidWithZero α] [WfDvdMonoid α] {a₀ x : α}
(h : a₀ ≠ 0) (hx : ¬IsUnit x) : ∃ (n : ℕ) (a : α), ¬x ∣ a ∧ a₀ = x ^ n * a := by
obtain ⟨a, ⟨n, rfl⟩, hm⟩ := wellFounded_dvdNotUnit.has_min
{a | ∃ n, x ^ n * a = a₀} ⟨a₀, 0, by rw [pow_zero, one_mul]⟩
refine ⟨n, a, ?_, rfl⟩; rintro ⟨d, rfl⟩
exact hm d ⟨n + 1, by rw [pow_succ, mul_assoc]⟩
⟨(right_ne_zero_of_mul <| right_ne_zero_of_mul h), x, hx, mul_comm _ _⟩
theorem WfDvdMonoid.max_power_factor [CommMonoidWithZero α] [WfDvdMonoid α] {a₀ x : α}
(h : a₀ ≠ 0) (hx : Irreducible x) : ∃ (n : ℕ) (a : α), ¬x ∣ a ∧ a₀ = x ^ n * a :=
max_power_factor' h hx.not_unit
theorem multiplicity.finite_of_not_isUnit [CancelCommMonoidWithZero α] [WfDvdMonoid α]
{a b : α} (ha : ¬IsUnit a) (hb : b ≠ 0) : multiplicity.Finite a b := by
obtain ⟨n, c, ndvd, rfl⟩ := WfDvdMonoid.max_power_factor' hb ha
exact ⟨n, by rwa [pow_succ, mul_dvd_mul_iff_left (left_ne_zero_of_mul hb)]⟩
section Prio
-- set_option default_priority 100
-- see Note [default priority]
/-- unique factorization monoids.
These are defined as `CancelCommMonoidWithZero`s with well-founded strict divisibility
relations, but this is equivalent to more familiar definitions:
Each element (except zero) is uniquely represented as a multiset of irreducible factors.
Uniqueness is only up to associated elements.
Each element (except zero) is non-uniquely represented as a multiset
of prime factors.
To define a UFD using the definition in terms of multisets
of irreducible factors, use the definition `of_exists_unique_irreducible_factors`
To define a UFD using the definition in terms of multisets
of prime factors, use the definition `of_exists_prime_factors`
-/
class UniqueFactorizationMonoid (α : Type*) [CancelCommMonoidWithZero α] extends WfDvdMonoid α :
Prop where
protected irreducible_iff_prime : ∀ {a : α}, Irreducible a ↔ Prime a
#align unique_factorization_monoid UniqueFactorizationMonoid
/-- Can't be an instance because it would cause a loop `ufm → WfDvdMonoid → ufm → ...`. -/
theorem ufm_of_decomposition_of_wfDvdMonoid [CancelCommMonoidWithZero α] [WfDvdMonoid α]
[DecompositionMonoid α] : UniqueFactorizationMonoid α :=
{ ‹WfDvdMonoid α› with irreducible_iff_prime := irreducible_iff_prime }
#align ufm_of_gcd_of_wf_dvd_monoid ufm_of_decomposition_of_wfDvdMonoid
@[deprecated] alias ufm_of_gcd_of_wfDvdMonoid := ufm_of_decomposition_of_wfDvdMonoid
instance Associates.ufm [CancelCommMonoidWithZero α] [UniqueFactorizationMonoid α] :
UniqueFactorizationMonoid (Associates α) :=
{ (WfDvdMonoid.wfDvdMonoid_associates : WfDvdMonoid (Associates α)) with
irreducible_iff_prime := by
rw [← Associates.irreducible_iff_prime_iff]
apply UniqueFactorizationMonoid.irreducible_iff_prime }
#align associates.ufm Associates.ufm
end Prio
namespace UniqueFactorizationMonoid
variable [CancelCommMonoidWithZero α] [UniqueFactorizationMonoid α]
theorem exists_prime_factors (a : α) :
a ≠ 0 → ∃ f : Multiset α, (∀ b ∈ f, Prime b) ∧ f.prod ~ᵤ a := by
simp_rw [← UniqueFactorizationMonoid.irreducible_iff_prime]
apply WfDvdMonoid.exists_factors a
#align unique_factorization_monoid.exists_prime_factors UniqueFactorizationMonoid.exists_prime_factors
instance : DecompositionMonoid α where
primal a := by
obtain rfl | ha := eq_or_ne a 0; · exact isPrimal_zero
obtain ⟨f, hf, u, rfl⟩ := exists_prime_factors a ha
exact ((Submonoid.isPrimal α).multiset_prod_mem f (hf · ·|>.isPrimal)).mul u.isUnit.isPrimal
lemma exists_prime_iff :
(∃ (p : α), Prime p) ↔ ∃ (x : α), x ≠ 0 ∧ ¬ IsUnit x := by
refine ⟨fun ⟨p, hp⟩ ↦ ⟨p, hp.ne_zero, hp.not_unit⟩, fun ⟨x, hx₀, hxu⟩ ↦ ?_⟩
obtain ⟨f, hf, -⟩ := WfDvdMonoid.exists_irreducible_factor hxu hx₀
exact ⟨f, UniqueFactorizationMonoid.irreducible_iff_prime.mp hf⟩
@[elab_as_elim]
theorem induction_on_prime {P : α → Prop} (a : α) (h₁ : P 0) (h₂ : ∀ x : α, IsUnit x → P x)
(h₃ : ∀ a p : α, a ≠ 0 → Prime p → P a → P (p * a)) : P a := by
simp_rw [← UniqueFactorizationMonoid.irreducible_iff_prime] at h₃
exact WfDvdMonoid.induction_on_irreducible a h₁ h₂ h₃
#align unique_factorization_monoid.induction_on_prime UniqueFactorizationMonoid.induction_on_prime
end UniqueFactorizationMonoid
theorem prime_factors_unique [CancelCommMonoidWithZero α] :
∀ {f g : Multiset α},
(∀ x ∈ f, Prime x) → (∀ x ∈ g, Prime x) → f.prod ~ᵤ g.prod → Multiset.Rel Associated f g := by
classical
intro f
induction' f using Multiset.induction_on with p f ih
· intros g _ hg h
exact Multiset.rel_zero_left.2 <|
Multiset.eq_zero_of_forall_not_mem fun x hx =>
have : IsUnit g.prod := by simpa [associated_one_iff_isUnit] using h.symm
(hg x hx).not_unit <|
isUnit_iff_dvd_one.2 <| (Multiset.dvd_prod hx).trans (isUnit_iff_dvd_one.1 this)
· intros g hf hg hfg
let ⟨b, hbg, hb⟩ :=
(exists_associated_mem_of_dvd_prod (hf p (by simp)) fun q hq => hg _ hq) <|
hfg.dvd_iff_dvd_right.1 (show p ∣ (p ::ₘ f).prod by simp)
haveI := Classical.decEq α
rw [← Multiset.cons_erase hbg]
exact
Multiset.Rel.cons hb
(ih (fun q hq => hf _ (by simp [hq]))
(fun {q} (hq : q ∈ g.erase b) => hg q (Multiset.mem_of_mem_erase hq))
(Associated.of_mul_left
(by rwa [← Multiset.prod_cons, ← Multiset.prod_cons, Multiset.cons_erase hbg]) hb
(hf p (by simp)).ne_zero))
#align prime_factors_unique prime_factors_unique
namespace UniqueFactorizationMonoid
variable [CancelCommMonoidWithZero α] [UniqueFactorizationMonoid α]
theorem factors_unique {f g : Multiset α} (hf : ∀ x ∈ f, Irreducible x)
(hg : ∀ x ∈ g, Irreducible x) (h : f.prod ~ᵤ g.prod) : Multiset.Rel Associated f g :=
prime_factors_unique (fun x hx => UniqueFactorizationMonoid.irreducible_iff_prime.mp (hf x hx))
(fun x hx => UniqueFactorizationMonoid.irreducible_iff_prime.mp (hg x hx)) h
#align unique_factorization_monoid.factors_unique UniqueFactorizationMonoid.factors_unique
end UniqueFactorizationMonoid
/-- If an irreducible has a prime factorization,
then it is an associate of one of its prime factors. -/
theorem prime_factors_irreducible [CancelCommMonoidWithZero α] {a : α} {f : Multiset α}
(ha : Irreducible a) (pfa : (∀ b ∈ f, Prime b) ∧ f.prod ~ᵤ a) : ∃ p, a ~ᵤ p ∧ f = {p} := by
haveI := Classical.decEq α
refine @Multiset.induction_on _
(fun g => (g.prod ~ᵤ a) → (∀ b ∈ g, Prime b) → ∃ p, a ~ᵤ p ∧ g = {p}) f ?_ ?_ pfa.2 pfa.1
· intro h; exact (ha.not_unit (associated_one_iff_isUnit.1 (Associated.symm h))).elim
· rintro p s _ ⟨u, hu⟩ hs
use p
have hs0 : s = 0 := by
by_contra hs0
obtain ⟨q, hq⟩ := Multiset.exists_mem_of_ne_zero hs0
apply (hs q (by simp [hq])).2.1
refine (ha.isUnit_or_isUnit (?_ : _ = p * ↑u * (s.erase q).prod * _)).resolve_left ?_
· rw [mul_right_comm _ _ q, mul_assoc, ← Multiset.prod_cons, Multiset.cons_erase hq, ← hu,
mul_comm, mul_comm p _, mul_assoc]
simp
apply mt isUnit_of_mul_isUnit_left (mt isUnit_of_mul_isUnit_left _)
apply (hs p (Multiset.mem_cons_self _ _)).2.1
simp only [mul_one, Multiset.prod_cons, Multiset.prod_zero, hs0] at *
exact ⟨Associated.symm ⟨u, hu⟩, rfl⟩
#align prime_factors_irreducible prime_factors_irreducible
section ExistsPrimeFactors
variable [CancelCommMonoidWithZero α]
variable (pf : ∀ a : α, a ≠ 0 → ∃ f : Multiset α, (∀ b ∈ f, Prime b) ∧ f.prod ~ᵤ a)
theorem WfDvdMonoid.of_exists_prime_factors : WfDvdMonoid α :=
⟨by
classical
refine RelHomClass.wellFounded
(RelHom.mk ?_ ?_ : (DvdNotUnit : α → α → Prop) →r ((· < ·) : ℕ∞ → ℕ∞ → Prop)) wellFounded_lt
· intro a
by_cases h : a = 0
· exact ⊤
exact ↑(Multiset.card (Classical.choose (pf a h)))
rintro a b ⟨ane0, ⟨c, hc, b_eq⟩⟩
rw [dif_neg ane0]
by_cases h : b = 0
· simp [h, lt_top_iff_ne_top]
· rw [dif_neg h]
erw [WithTop.coe_lt_coe]
have cne0 : c ≠ 0 := by
refine mt (fun con => ?_) h
rw [b_eq, con, mul_zero]
calc
Multiset.card (Classical.choose (pf a ane0)) <
_ + Multiset.card (Classical.choose (pf c cne0)) :=
lt_add_of_pos_right _
(Multiset.card_pos.mpr fun con => hc (associated_one_iff_isUnit.mp ?_))
_ = Multiset.card (Classical.choose (pf a ane0) + Classical.choose (pf c cne0)) :=
(Multiset.card_add _ _).symm
_ = Multiset.card (Classical.choose (pf b h)) :=
Multiset.card_eq_card_of_rel
(prime_factors_unique ?_ (Classical.choose_spec (pf _ h)).1 ?_)
· convert (Classical.choose_spec (pf c cne0)).2.symm
rw [con, Multiset.prod_zero]
· intro x hadd
rw [Multiset.mem_add] at hadd
cases' hadd with h h <;> apply (Classical.choose_spec (pf _ _)).1 _ h <;> assumption
· rw [Multiset.prod_add]
trans a * c
· apply Associated.mul_mul <;> apply (Classical.choose_spec (pf _ _)).2 <;> assumption
· rw [← b_eq]
apply (Classical.choose_spec (pf _ _)).2.symm; assumption⟩
#align wf_dvd_monoid.of_exists_prime_factors WfDvdMonoid.of_exists_prime_factors
theorem irreducible_iff_prime_of_exists_prime_factors {p : α} : Irreducible p ↔ Prime p := by
by_cases hp0 : p = 0
· simp [hp0]
refine ⟨fun h => ?_, Prime.irreducible⟩
obtain ⟨f, hf⟩ := pf p hp0
obtain ⟨q, hq, rfl⟩ := prime_factors_irreducible h hf
rw [hq.prime_iff]
exact hf.1 q (Multiset.mem_singleton_self _)
#align irreducible_iff_prime_of_exists_prime_factors irreducible_iff_prime_of_exists_prime_factors
theorem UniqueFactorizationMonoid.of_exists_prime_factors : UniqueFactorizationMonoid α :=
{ WfDvdMonoid.of_exists_prime_factors pf with
irreducible_iff_prime := irreducible_iff_prime_of_exists_prime_factors pf }
#align unique_factorization_monoid.of_exists_prime_factors UniqueFactorizationMonoid.of_exists_prime_factors
end ExistsPrimeFactors
theorem UniqueFactorizationMonoid.iff_exists_prime_factors [CancelCommMonoidWithZero α] :
UniqueFactorizationMonoid α ↔
∀ a : α, a ≠ 0 → ∃ f : Multiset α, (∀ b ∈ f, Prime b) ∧ f.prod ~ᵤ a :=
⟨fun h => @UniqueFactorizationMonoid.exists_prime_factors _ _ h,
UniqueFactorizationMonoid.of_exists_prime_factors⟩
#align unique_factorization_monoid.iff_exists_prime_factors UniqueFactorizationMonoid.iff_exists_prime_factors
section
variable {β : Type*} [CancelCommMonoidWithZero α] [CancelCommMonoidWithZero β]
theorem MulEquiv.uniqueFactorizationMonoid (e : α ≃* β) (hα : UniqueFactorizationMonoid α) :
UniqueFactorizationMonoid β := by
rw [UniqueFactorizationMonoid.iff_exists_prime_factors] at hα ⊢
intro a ha
obtain ⟨w, hp, u, h⟩ :=
hα (e.symm a) fun h =>
ha <| by
convert← map_zero e
simp [← h]
exact
⟨w.map e, fun b hb =>
let ⟨c, hc, he⟩ := Multiset.mem_map.1 hb
he ▸ e.prime_iff.1 (hp c hc),
Units.map e.toMonoidHom u,
by
erw [Multiset.prod_hom, ← e.map_mul, h]
simp⟩
#align mul_equiv.unique_factorization_monoid MulEquiv.uniqueFactorizationMonoid
theorem MulEquiv.uniqueFactorizationMonoid_iff (e : α ≃* β) :
UniqueFactorizationMonoid α ↔ UniqueFactorizationMonoid β :=
⟨e.uniqueFactorizationMonoid, e.symm.uniqueFactorizationMonoid⟩
#align mul_equiv.unique_factorization_monoid_iff MulEquiv.uniqueFactorizationMonoid_iff
end
theorem irreducible_iff_prime_of_exists_unique_irreducible_factors [CancelCommMonoidWithZero α]
(eif : ∀ a : α, a ≠ 0 → ∃ f : Multiset α, (∀ b ∈ f, Irreducible b) ∧ f.prod ~ᵤ a)
(uif :
∀ f g : Multiset α,
(∀ x ∈ f, Irreducible x) →
(∀ x ∈ g, Irreducible x) → f.prod ~ᵤ g.prod → Multiset.Rel Associated f g)
(p : α) : Irreducible p ↔ Prime p :=
letI := Classical.decEq α
⟨ fun hpi =>
⟨hpi.ne_zero, hpi.1, fun a b ⟨x, hx⟩ =>
if hab0 : a * b = 0 then
(eq_zero_or_eq_zero_of_mul_eq_zero hab0).elim (fun ha0 => by simp [ha0]) fun hb0 => by
simp [hb0]
else by
have hx0 : x ≠ 0 := fun hx0 => by simp_all
have ha0 : a ≠ 0 := left_ne_zero_of_mul hab0
have hb0 : b ≠ 0 := right_ne_zero_of_mul hab0
cases' eif x hx0 with fx hfx
cases' eif a ha0 with fa hfa
cases' eif b hb0 with fb hfb
have h : Multiset.Rel Associated (p ::ₘ fx) (fa + fb) := by
apply uif
· exact fun i hi => (Multiset.mem_cons.1 hi).elim (fun hip => hip.symm ▸ hpi) (hfx.1 _)
· exact fun i hi => (Multiset.mem_add.1 hi).elim (hfa.1 _) (hfb.1 _)
calc
Multiset.prod (p ::ₘ fx) ~ᵤ a * b := by
rw [hx, Multiset.prod_cons]; exact hfx.2.mul_left _
_ ~ᵤ fa.prod * fb.prod := hfa.2.symm.mul_mul hfb.2.symm
_ = _ := by rw [Multiset.prod_add]
exact
let ⟨q, hqf, hq⟩ := Multiset.exists_mem_of_rel_of_mem h (Multiset.mem_cons_self p _)
(Multiset.mem_add.1 hqf).elim
(fun hqa =>
Or.inl <| hq.dvd_iff_dvd_left.2 <| hfa.2.dvd_iff_dvd_right.1 (Multiset.dvd_prod hqa))
fun hqb =>
Or.inr <| hq.dvd_iff_dvd_left.2 <| hfb.2.dvd_iff_dvd_right.1 (Multiset.dvd_prod hqb)⟩,
Prime.irreducible⟩
#align irreducible_iff_prime_of_exists_unique_irreducible_factors irreducible_iff_prime_of_exists_unique_irreducible_factors
theorem UniqueFactorizationMonoid.of_exists_unique_irreducible_factors [CancelCommMonoidWithZero α]
(eif : ∀ a : α, a ≠ 0 → ∃ f : Multiset α, (∀ b ∈ f, Irreducible b) ∧ f.prod ~ᵤ a)
(uif :
∀ f g : Multiset α,
(∀ x ∈ f, Irreducible x) →
(∀ x ∈ g, Irreducible x) → f.prod ~ᵤ g.prod → Multiset.Rel Associated f g) :
UniqueFactorizationMonoid α :=
UniqueFactorizationMonoid.of_exists_prime_factors
(by
convert eif using 7
simp_rw [irreducible_iff_prime_of_exists_unique_irreducible_factors eif uif])
#align unique_factorization_monoid.of_exists_unique_irreducible_factors UniqueFactorizationMonoid.of_exists_unique_irreducible_factors
namespace UniqueFactorizationMonoid
variable [CancelCommMonoidWithZero α]
variable [UniqueFactorizationMonoid α]
open Classical in
/-- Noncomputably determines the multiset of prime factors. -/
noncomputable def factors (a : α) : Multiset α :=
if h : a = 0 then 0 else Classical.choose (UniqueFactorizationMonoid.exists_prime_factors a h)
#align unique_factorization_monoid.factors UniqueFactorizationMonoid.factors
theorem factors_prod {a : α} (ane0 : a ≠ 0) : Associated (factors a).prod a := by
rw [factors, dif_neg ane0]
exact (Classical.choose_spec (exists_prime_factors a ane0)).2
#align unique_factorization_monoid.factors_prod UniqueFactorizationMonoid.factors_prod
@[simp]
theorem factors_zero : factors (0 : α) = 0 := by simp [factors]
#align unique_factorization_monoid.factors_zero UniqueFactorizationMonoid.factors_zero
theorem ne_zero_of_mem_factors {p a : α} (h : p ∈ factors a) : a ≠ 0 := by
rintro rfl
simp at h
#align unique_factorization_monoid.ne_zero_of_mem_factors UniqueFactorizationMonoid.ne_zero_of_mem_factors
theorem dvd_of_mem_factors {p a : α} (h : p ∈ factors a) : p ∣ a :=
dvd_trans (Multiset.dvd_prod h) (Associated.dvd (factors_prod (ne_zero_of_mem_factors h)))
#align unique_factorization_monoid.dvd_of_mem_factors UniqueFactorizationMonoid.dvd_of_mem_factors
theorem prime_of_factor {a : α} (x : α) (hx : x ∈ factors a) : Prime x := by
have ane0 := ne_zero_of_mem_factors hx
rw [factors, dif_neg ane0] at hx
exact (Classical.choose_spec (UniqueFactorizationMonoid.exists_prime_factors a ane0)).1 x hx
#align unique_factorization_monoid.prime_of_factor UniqueFactorizationMonoid.prime_of_factor
theorem irreducible_of_factor {a : α} : ∀ x : α, x ∈ factors a → Irreducible x := fun x h =>
(prime_of_factor x h).irreducible
#align unique_factorization_monoid.irreducible_of_factor UniqueFactorizationMonoid.irreducible_of_factor
@[simp]
theorem factors_one : factors (1 : α) = 0 := by
nontriviality α using factors
rw [← Multiset.rel_zero_right]
refine factors_unique irreducible_of_factor (fun x hx => (Multiset.not_mem_zero x hx).elim) ?_
rw [Multiset.prod_zero]
exact factors_prod one_ne_zero
#align unique_factorization_monoid.factors_one UniqueFactorizationMonoid.factors_one
theorem exists_mem_factors_of_dvd {a p : α} (ha0 : a ≠ 0) (hp : Irreducible p) :
p ∣ a → ∃ q ∈ factors a, p ~ᵤ q := fun ⟨b, hb⟩ =>
have hb0 : b ≠ 0 := fun hb0 => by simp_all
have : Multiset.Rel Associated (p ::ₘ factors b) (factors a) :=
factors_unique
(fun x hx => (Multiset.mem_cons.1 hx).elim (fun h => h.symm ▸ hp) (irreducible_of_factor _))
irreducible_of_factor
(Associated.symm <|
calc
Multiset.prod (factors a) ~ᵤ a := factors_prod ha0
_ = p * b := hb
_ ~ᵤ Multiset.prod (p ::ₘ factors b) := by
rw [Multiset.prod_cons]; exact (factors_prod hb0).symm.mul_left _
)
Multiset.exists_mem_of_rel_of_mem this (by simp)
#align unique_factorization_monoid.exists_mem_factors_of_dvd UniqueFactorizationMonoid.exists_mem_factors_of_dvd
theorem exists_mem_factors {x : α} (hx : x ≠ 0) (h : ¬IsUnit x) : ∃ p, p ∈ factors x := by
obtain ⟨p', hp', hp'x⟩ := WfDvdMonoid.exists_irreducible_factor h hx
obtain ⟨p, hp, _⟩ := exists_mem_factors_of_dvd hx hp' hp'x
exact ⟨p, hp⟩
#align unique_factorization_monoid.exists_mem_factors UniqueFactorizationMonoid.exists_mem_factors
open Classical in
theorem factors_mul {x y : α} (hx : x ≠ 0) (hy : y ≠ 0) :
Multiset.Rel Associated (factors (x * y)) (factors x + factors y) := by
refine
factors_unique irreducible_of_factor
(fun a ha =>
(Multiset.mem_add.mp ha).by_cases (irreducible_of_factor _) (irreducible_of_factor _))
((factors_prod (mul_ne_zero hx hy)).trans ?_)
rw [Multiset.prod_add]
exact (Associated.mul_mul (factors_prod hx) (factors_prod hy)).symm
#align unique_factorization_monoid.factors_mul UniqueFactorizationMonoid.factors_mul
theorem factors_pow {x : α} (n : ℕ) :
Multiset.Rel Associated (factors (x ^ n)) (n • factors x) := by
match n with
| 0 => rw [zero_smul, pow_zero, factors_one, Multiset.rel_zero_right]
| n+1 =>
by_cases h0 : x = 0
· simp [h0, zero_pow n.succ_ne_zero, smul_zero]
· rw [pow_succ', succ_nsmul']
refine Multiset.Rel.trans _ (factors_mul h0 (pow_ne_zero n h0)) ?_
refine Multiset.Rel.add ?_ <| factors_pow n
exact Multiset.rel_refl_of_refl_on fun y _ => Associated.refl _
#align unique_factorization_monoid.factors_pow UniqueFactorizationMonoid.factors_pow
@[simp]
theorem factors_pos (x : α) (hx : x ≠ 0) : 0 < factors x ↔ ¬IsUnit x := by
constructor
· intro h hx
obtain ⟨p, hp⟩ := Multiset.exists_mem_of_ne_zero h.ne'
exact (prime_of_factor _ hp).not_unit (isUnit_of_dvd_unit (dvd_of_mem_factors hp) hx)
· intro h
obtain ⟨p, hp⟩ := exists_mem_factors hx h
exact
bot_lt_iff_ne_bot.mpr
(mt Multiset.eq_zero_iff_forall_not_mem.mp (not_forall.mpr ⟨p, not_not.mpr hp⟩))
#align unique_factorization_monoid.factors_pos UniqueFactorizationMonoid.factors_pos
open Multiset in
theorem factors_pow_count_prod [DecidableEq α] {x : α} (hx : x ≠ 0) :
(∏ p ∈ (factors x).toFinset, p ^ (factors x).count p) ~ᵤ x :=
calc
_ = prod (∑ a ∈ toFinset (factors x), count a (factors x) • {a}) := by
simp only [prod_sum, prod_nsmul, prod_singleton]
_ = prod (factors x) := by rw [toFinset_sum_count_nsmul_eq (factors x)]
_ ~ᵤ x := factors_prod hx
end UniqueFactorizationMonoid
namespace UniqueFactorizationMonoid
variable [CancelCommMonoidWithZero α] [NormalizationMonoid α]
variable [UniqueFactorizationMonoid α]
/-- Noncomputably determines the multiset of prime factors. -/
noncomputable def normalizedFactors (a : α) : Multiset α :=
Multiset.map normalize <| factors a
#align unique_factorization_monoid.normalized_factors UniqueFactorizationMonoid.normalizedFactors
/-- An arbitrary choice of factors of `x : M` is exactly the (unique) normalized set of factors,
if `M` has a trivial group of units. -/
@[simp]
theorem factors_eq_normalizedFactors {M : Type*} [CancelCommMonoidWithZero M]
[UniqueFactorizationMonoid M] [Unique Mˣ] (x : M) : factors x = normalizedFactors x := by
unfold normalizedFactors
convert (Multiset.map_id (factors x)).symm
ext p
exact normalize_eq p
#align unique_factorization_monoid.factors_eq_normalized_factors UniqueFactorizationMonoid.factors_eq_normalizedFactors
theorem normalizedFactors_prod {a : α} (ane0 : a ≠ 0) :
Associated (normalizedFactors a).prod a := by
rw [normalizedFactors, factors, dif_neg ane0]
refine Associated.trans ?_ (Classical.choose_spec (exists_prime_factors a ane0)).2
rw [← Associates.mk_eq_mk_iff_associated, ← Associates.prod_mk, ← Associates.prod_mk,
Multiset.map_map]
congr 2
ext
rw [Function.comp_apply, Associates.mk_normalize]
#align unique_factorization_monoid.normalized_factors_prod UniqueFactorizationMonoid.normalizedFactors_prod
theorem prime_of_normalized_factor {a : α} : ∀ x : α, x ∈ normalizedFactors a → Prime x := by
rw [normalizedFactors, factors]
split_ifs with ane0; · simp
intro x hx; rcases Multiset.mem_map.1 hx with ⟨y, ⟨hy, rfl⟩⟩
rw [(normalize_associated _).prime_iff]
exact (Classical.choose_spec (UniqueFactorizationMonoid.exists_prime_factors a ane0)).1 y hy
#align unique_factorization_monoid.prime_of_normalized_factor UniqueFactorizationMonoid.prime_of_normalized_factor
theorem irreducible_of_normalized_factor {a : α} :
∀ x : α, x ∈ normalizedFactors a → Irreducible x := fun x h =>
(prime_of_normalized_factor x h).irreducible
#align unique_factorization_monoid.irreducible_of_normalized_factor UniqueFactorizationMonoid.irreducible_of_normalized_factor
| Mathlib/RingTheory/UniqueFactorizationDomain.lean | 626 | 632 | theorem normalize_normalized_factor {a : α} :
∀ x : α, x ∈ normalizedFactors a → normalize x = x := by |
rw [normalizedFactors, factors]
split_ifs with h; · simp
intro x hx
obtain ⟨y, _, rfl⟩ := Multiset.mem_map.1 hx
apply normalize_idem
|
/-
Copyright (c) 2021 Scott Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johan Commelin, Scott Morrison
-/
import Mathlib.Algebra.Homology.ComplexShape
import Mathlib.CategoryTheory.Subobject.Limits
import Mathlib.CategoryTheory.GradedObject
import Mathlib.Algebra.Homology.ShortComplex.Basic
#align_import algebra.homology.homological_complex from "leanprover-community/mathlib"@"88bca0ce5d22ebfd9e73e682e51d60ea13b48347"
/-!
# Homological complexes.
A `HomologicalComplex V c` with a "shape" controlled by `c : ComplexShape ι`
has chain groups `X i` (objects in `V`) indexed by `i : ι`,
and a differential `d i j` whenever `c.Rel i j`.
We in fact ask for differentials `d i j` for all `i j : ι`,
but have a field `shape` requiring that these are zero when not allowed by `c`.
This avoids a lot of dependent type theory hell!
The composite of any two differentials `d i j ≫ d j k` must be zero.
We provide `ChainComplex V α` for
`α`-indexed chain complexes in which `d i j ≠ 0` only if `j + 1 = i`,
and similarly `CochainComplex V α`, with `i = j + 1`.
There is a category structure, where morphisms are chain maps.
For `C : HomologicalComplex V c`, we define `C.xNext i`, which is either `C.X j` for some
arbitrarily chosen `j` such that `c.r i j`, or `C.X i` if there is no such `j`.
Similarly we have `C.xPrev j`.
Defined in terms of these we have `C.dFrom i : C.X i ⟶ C.xNext i` and
`C.dTo j : C.xPrev j ⟶ C.X j`, which are either defined as `C.d i j`, or zero, as needed.
-/
universe v u
open CategoryTheory CategoryTheory.Category CategoryTheory.Limits
variable {ι : Type*}
variable (V : Type u) [Category.{v} V] [HasZeroMorphisms V]
/-- A `HomologicalComplex V c` with a "shape" controlled by `c : ComplexShape ι`
has chain groups `X i` (objects in `V`) indexed by `i : ι`,
and a differential `d i j` whenever `c.Rel i j`.
We in fact ask for differentials `d i j` for all `i j : ι`,
but have a field `shape` requiring that these are zero when not allowed by `c`.
This avoids a lot of dependent type theory hell!
The composite of any two differentials `d i j ≫ d j k` must be zero.
-/
structure HomologicalComplex (c : ComplexShape ι) where
X : ι → V
d : ∀ i j, X i ⟶ X j
shape : ∀ i j, ¬c.Rel i j → d i j = 0 := by aesop_cat
d_comp_d' : ∀ i j k, c.Rel i j → c.Rel j k → d i j ≫ d j k = 0 := by aesop_cat
#align homological_complex HomologicalComplex
namespace HomologicalComplex
attribute [simp] shape
variable {V} {c : ComplexShape ι}
@[reassoc (attr := simp)]
theorem d_comp_d (C : HomologicalComplex V c) (i j k : ι) : C.d i j ≫ C.d j k = 0 := by
by_cases hij : c.Rel i j
· by_cases hjk : c.Rel j k
· exact C.d_comp_d' i j k hij hjk
· rw [C.shape j k hjk, comp_zero]
· rw [C.shape i j hij, zero_comp]
#align homological_complex.d_comp_d HomologicalComplex.d_comp_d
theorem ext {C₁ C₂ : HomologicalComplex V c} (h_X : C₁.X = C₂.X)
(h_d :
∀ i j : ι,
c.Rel i j → C₁.d i j ≫ eqToHom (congr_fun h_X j) = eqToHom (congr_fun h_X i) ≫ C₂.d i j) :
C₁ = C₂ := by
obtain ⟨X₁, d₁, s₁, h₁⟩ := C₁
obtain ⟨X₂, d₂, s₂, h₂⟩ := C₂
dsimp at h_X
subst h_X
simp only [mk.injEq, heq_eq_eq, true_and]
ext i j
by_cases hij: c.Rel i j
· simpa only [comp_id, id_comp, eqToHom_refl] using h_d i j hij
· rw [s₁ i j hij, s₂ i j hij]
#align homological_complex.ext HomologicalComplex.ext
/-- The obvious isomorphism `K.X p ≅ K.X q` when `p = q`. -/
def XIsoOfEq (K : HomologicalComplex V c) {p q : ι} (h : p = q) : K.X p ≅ K.X q :=
eqToIso (by rw [h])
@[simp]
lemma XIsoOfEq_rfl (K : HomologicalComplex V c) (p : ι) :
K.XIsoOfEq (rfl : p = p) = Iso.refl _ := rfl
@[reassoc (attr := simp)]
lemma XIsoOfEq_hom_comp_XIsoOfEq_hom (K : HomologicalComplex V c) {p₁ p₂ p₃ : ι}
(h₁₂ : p₁ = p₂) (h₂₃ : p₂ = p₃) :
(K.XIsoOfEq h₁₂).hom ≫ (K.XIsoOfEq h₂₃).hom = (K.XIsoOfEq (h₁₂.trans h₂₃)).hom := by
dsimp [XIsoOfEq]
simp only [eqToHom_trans]
@[reassoc (attr := simp)]
lemma XIsoOfEq_hom_comp_XIsoOfEq_inv (K : HomologicalComplex V c) {p₁ p₂ p₃ : ι}
(h₁₂ : p₁ = p₂) (h₃₂ : p₃ = p₂) :
(K.XIsoOfEq h₁₂).hom ≫ (K.XIsoOfEq h₃₂).inv = (K.XIsoOfEq (h₁₂.trans h₃₂.symm)).hom := by
dsimp [XIsoOfEq]
simp only [eqToHom_trans]
@[reassoc (attr := simp)]
lemma XIsoOfEq_inv_comp_XIsoOfEq_hom (K : HomologicalComplex V c) {p₁ p₂ p₃ : ι}
(h₂₁ : p₂ = p₁) (h₂₃ : p₂ = p₃) :
(K.XIsoOfEq h₂₁).inv ≫ (K.XIsoOfEq h₂₃).hom = (K.XIsoOfEq (h₂₁.symm.trans h₂₃)).hom := by
dsimp [XIsoOfEq]
simp only [eqToHom_trans]
@[reassoc (attr := simp)]
lemma XIsoOfEq_inv_comp_XIsoOfEq_inv (K : HomologicalComplex V c) {p₁ p₂ p₃ : ι}
(h₂₁ : p₂ = p₁) (h₃₂ : p₃ = p₂) :
(K.XIsoOfEq h₂₁).inv ≫ (K.XIsoOfEq h₃₂).inv = (K.XIsoOfEq (h₃₂.trans h₂₁).symm).hom := by
dsimp [XIsoOfEq]
simp only [eqToHom_trans]
@[reassoc (attr := simp)]
lemma XIsoOfEq_hom_comp_d (K : HomologicalComplex V c) {p₁ p₂ : ι} (h : p₁ = p₂) (p₃ : ι) :
(K.XIsoOfEq h).hom ≫ K.d p₂ p₃ = K.d p₁ p₃ := by subst h; simp
@[reassoc (attr := simp)]
lemma XIsoOfEq_inv_comp_d (K : HomologicalComplex V c) {p₂ p₁ : ι} (h : p₂ = p₁) (p₃ : ι) :
(K.XIsoOfEq h).inv ≫ K.d p₂ p₃ = K.d p₁ p₃ := by subst h; simp
@[reassoc (attr := simp)]
lemma d_comp_XIsoOfEq_hom (K : HomologicalComplex V c) {p₂ p₃ : ι} (h : p₂ = p₃) (p₁ : ι) :
K.d p₁ p₂ ≫ (K.XIsoOfEq h).hom = K.d p₁ p₃ := by subst h; simp
@[reassoc (attr := simp)]
lemma d_comp_XIsoOfEq_inv (K : HomologicalComplex V c) {p₂ p₃ : ι} (h : p₃ = p₂) (p₁ : ι) :
K.d p₁ p₂ ≫ (K.XIsoOfEq h).inv = K.d p₁ p₃ := by subst h; simp
end HomologicalComplex
/-- An `α`-indexed chain complex is a `HomologicalComplex`
in which `d i j ≠ 0` only if `j + 1 = i`.
-/
abbrev ChainComplex (α : Type*) [AddRightCancelSemigroup α] [One α] : Type _ :=
HomologicalComplex V (ComplexShape.down α)
#align chain_complex ChainComplex
/-- An `α`-indexed cochain complex is a `HomologicalComplex`
in which `d i j ≠ 0` only if `i + 1 = j`.
-/
abbrev CochainComplex (α : Type*) [AddRightCancelSemigroup α] [One α] : Type _ :=
HomologicalComplex V (ComplexShape.up α)
#align cochain_complex CochainComplex
namespace ChainComplex
@[simp]
theorem prev (α : Type*) [AddRightCancelSemigroup α] [One α] (i : α) :
(ComplexShape.down α).prev i = i + 1 :=
(ComplexShape.down α).prev_eq' rfl
#align chain_complex.prev ChainComplex.prev
@[simp]
theorem next (α : Type*) [AddGroup α] [One α] (i : α) : (ComplexShape.down α).next i = i - 1 :=
(ComplexShape.down α).next_eq' <| sub_add_cancel _ _
#align chain_complex.next ChainComplex.next
@[simp]
theorem next_nat_zero : (ComplexShape.down ℕ).next 0 = 0 := by
classical
refine dif_neg ?_
push_neg
intro
apply Nat.noConfusion
#align chain_complex.next_nat_zero ChainComplex.next_nat_zero
@[simp]
theorem next_nat_succ (i : ℕ) : (ComplexShape.down ℕ).next (i + 1) = i :=
(ComplexShape.down ℕ).next_eq' rfl
#align chain_complex.next_nat_succ ChainComplex.next_nat_succ
end ChainComplex
namespace CochainComplex
@[simp]
theorem prev (α : Type*) [AddGroup α] [One α] (i : α) : (ComplexShape.up α).prev i = i - 1 :=
(ComplexShape.up α).prev_eq' <| sub_add_cancel _ _
#align cochain_complex.prev CochainComplex.prev
@[simp]
theorem next (α : Type*) [AddRightCancelSemigroup α] [One α] (i : α) :
(ComplexShape.up α).next i = i + 1 :=
(ComplexShape.up α).next_eq' rfl
#align cochain_complex.next CochainComplex.next
@[simp]
theorem prev_nat_zero : (ComplexShape.up ℕ).prev 0 = 0 := by
classical
refine dif_neg ?_
push_neg
intro
apply Nat.noConfusion
#align cochain_complex.prev_nat_zero CochainComplex.prev_nat_zero
@[simp]
theorem prev_nat_succ (i : ℕ) : (ComplexShape.up ℕ).prev (i + 1) = i :=
(ComplexShape.up ℕ).prev_eq' rfl
#align cochain_complex.prev_nat_succ CochainComplex.prev_nat_succ
end CochainComplex
namespace HomologicalComplex
variable {V}
variable {c : ComplexShape ι} (C : HomologicalComplex V c)
/-- A morphism of homological complexes consists of maps between the chain groups,
commuting with the differentials.
-/
@[ext]
structure Hom (A B : HomologicalComplex V c) where
f : ∀ i, A.X i ⟶ B.X i
comm' : ∀ i j, c.Rel i j → f i ≫ B.d i j = A.d i j ≫ f j := by aesop_cat
#align homological_complex.hom HomologicalComplex.Hom
@[reassoc (attr := simp)]
theorem Hom.comm {A B : HomologicalComplex V c} (f : A.Hom B) (i j : ι) :
f.f i ≫ B.d i j = A.d i j ≫ f.f j := by
by_cases hij : c.Rel i j
· exact f.comm' i j hij
· rw [A.shape i j hij, B.shape i j hij, comp_zero, zero_comp]
#align homological_complex.hom.comm HomologicalComplex.Hom.comm
instance (A B : HomologicalComplex V c) : Inhabited (Hom A B) :=
⟨{ f := fun i => 0 }⟩
/-- Identity chain map. -/
def id (A : HomologicalComplex V c) : Hom A A where f _ := 𝟙 _
#align homological_complex.id HomologicalComplex.id
/-- Composition of chain maps. -/
def comp (A B C : HomologicalComplex V c) (φ : Hom A B) (ψ : Hom B C) : Hom A C where
f i := φ.f i ≫ ψ.f i
#align homological_complex.comp HomologicalComplex.comp
section
attribute [local simp] id comp
instance : Category (HomologicalComplex V c) where
Hom := Hom
id := id
comp := comp _ _ _
end
-- Porting note: added because `Hom.ext` is not triggered automatically
@[ext]
lemma hom_ext {C D : HomologicalComplex V c} (f g : C ⟶ D)
(h : ∀ i, f.f i = g.f i) : f = g := by
apply Hom.ext
funext
apply h
@[simp]
theorem id_f (C : HomologicalComplex V c) (i : ι) : Hom.f (𝟙 C) i = 𝟙 (C.X i) :=
rfl
#align homological_complex.id_f HomologicalComplex.id_f
@[simp, reassoc]
theorem comp_f {C₁ C₂ C₃ : HomologicalComplex V c} (f : C₁ ⟶ C₂) (g : C₂ ⟶ C₃) (i : ι) :
(f ≫ g).f i = f.f i ≫ g.f i :=
rfl
#align homological_complex.comp_f HomologicalComplex.comp_f
@[simp]
theorem eqToHom_f {C₁ C₂ : HomologicalComplex V c} (h : C₁ = C₂) (n : ι) :
HomologicalComplex.Hom.f (eqToHom h) n =
eqToHom (congr_fun (congr_arg HomologicalComplex.X h) n) := by
subst h
rfl
#align homological_complex.eq_to_hom_f HomologicalComplex.eqToHom_f
-- We'll use this later to show that `HomologicalComplex V c` is preadditive when `V` is.
theorem hom_f_injective {C₁ C₂ : HomologicalComplex V c} :
Function.Injective fun f : Hom C₁ C₂ => f.f := by aesop_cat
#align homological_complex.hom_f_injective HomologicalComplex.hom_f_injective
instance (X Y : HomologicalComplex V c) : Zero (X ⟶ Y) :=
⟨{ f := fun i => 0}⟩
@[simp]
theorem zero_f (C D : HomologicalComplex V c) (i : ι) : (0 : C ⟶ D).f i = 0 :=
rfl
#align homological_complex.zero_apply HomologicalComplex.zero_f
instance : HasZeroMorphisms (HomologicalComplex V c) where
open ZeroObject
/-- The zero complex -/
noncomputable def zero [HasZeroObject V] : HomologicalComplex V c where
X _ := 0
d _ _ := 0
#align homological_complex.zero HomologicalComplex.zero
theorem isZero_zero [HasZeroObject V] : IsZero (zero : HomologicalComplex V c) := by
refine ⟨fun X => ⟨⟨⟨0⟩, fun f => ?_⟩⟩, fun X => ⟨⟨⟨0⟩, fun f => ?_⟩⟩⟩
all_goals
ext
dsimp [zero]
apply Subsingleton.elim
#align homological_complex.is_zero_zero HomologicalComplex.isZero_zero
instance [HasZeroObject V] : HasZeroObject (HomologicalComplex V c) :=
⟨⟨zero, isZero_zero⟩⟩
noncomputable instance [HasZeroObject V] : Inhabited (HomologicalComplex V c) :=
⟨zero⟩
theorem congr_hom {C D : HomologicalComplex V c} {f g : C ⟶ D} (w : f = g) (i : ι) :
f.f i = g.f i :=
congr_fun (congr_arg Hom.f w) i
#align homological_complex.congr_hom HomologicalComplex.congr_hom
lemma mono_of_mono_f {K L : HomologicalComplex V c} (φ : K ⟶ L)
(hφ : ∀ i, Mono (φ.f i)) : Mono φ where
right_cancellation g h eq := by
ext i
rw [← cancel_mono (φ.f i)]
exact congr_hom eq i
lemma epi_of_epi_f {K L : HomologicalComplex V c} (φ : K ⟶ L)
(hφ : ∀ i, Epi (φ.f i)) : Epi φ where
left_cancellation g h eq := by
ext i
rw [← cancel_epi (φ.f i)]
exact congr_hom eq i
section
variable (V c)
/-- The functor picking out the `i`-th object of a complex. -/
@[simps]
def eval (i : ι) : HomologicalComplex V c ⥤ V where
obj C := C.X i
map f := f.f i
#align homological_complex.eval HomologicalComplex.eval
/-- The functor forgetting the differential in a complex, obtaining a graded object. -/
@[simps]
def forget : HomologicalComplex V c ⥤ GradedObject ι V where
obj C := C.X
map f := f.f
#align homological_complex.forget HomologicalComplex.forget
instance : (forget V c).Faithful where
map_injective h := by
ext i
exact congr_fun h i
/-- Forgetting the differentials than picking out the `i`-th object is the same as
just picking out the `i`-th object. -/
@[simps!]
def forgetEval (i : ι) : forget V c ⋙ GradedObject.eval i ≅ eval V c i :=
NatIso.ofComponents fun X => Iso.refl _
#align homological_complex.forget_eval HomologicalComplex.forgetEval
end
noncomputable section
@[reassoc]
lemma XIsoOfEq_hom_naturality {K L : HomologicalComplex V c} (φ : K ⟶ L) {n n' : ι} (h : n = n') :
φ.f n ≫ (L.XIsoOfEq h).hom = (K.XIsoOfEq h).hom ≫ φ.f n' := by subst h; simp
@[reassoc]
lemma XIsoOfEq_inv_naturality {K L : HomologicalComplex V c} (φ : K ⟶ L) {n n' : ι} (h : n = n') :
φ.f n' ≫ (L.XIsoOfEq h).inv = (K.XIsoOfEq h).inv ≫ φ.f n := by subst h; simp
-- Porting note: removed @[simp] as the linter complained
/-- If `C.d i j` and `C.d i j'` are both allowed, then we must have `j = j'`,
and so the differentials only differ by an `eqToHom`.
-/
theorem d_comp_eqToHom {i j j' : ι} (rij : c.Rel i j) (rij' : c.Rel i j') :
C.d i j' ≫ eqToHom (congr_arg C.X (c.next_eq rij' rij)) = C.d i j := by
obtain rfl := c.next_eq rij rij'
simp only [eqToHom_refl, comp_id]
#align homological_complex.d_comp_eq_to_hom HomologicalComplex.d_comp_eqToHom
-- Porting note: removed @[simp] as the linter complained
/-- If `C.d i j` and `C.d i' j` are both allowed, then we must have `i = i'`,
and so the differentials only differ by an `eqToHom`.
-/
theorem eqToHom_comp_d {i i' j : ι} (rij : c.Rel i j) (rij' : c.Rel i' j) :
eqToHom (congr_arg C.X (c.prev_eq rij rij')) ≫ C.d i' j = C.d i j := by
obtain rfl := c.prev_eq rij rij'
simp only [eqToHom_refl, id_comp]
#align homological_complex.eq_to_hom_comp_d HomologicalComplex.eqToHom_comp_d
theorem kernel_eq_kernel [HasKernels V] {i j j' : ι} (r : c.Rel i j) (r' : c.Rel i j') :
kernelSubobject (C.d i j) = kernelSubobject (C.d i j') := by
rw [← d_comp_eqToHom C r r']
apply kernelSubobject_comp_mono
#align homological_complex.kernel_eq_kernel HomologicalComplex.kernel_eq_kernel
theorem image_eq_image [HasImages V] [HasEqualizers V] {i i' j : ι} (r : c.Rel i j)
(r' : c.Rel i' j) : imageSubobject (C.d i j) = imageSubobject (C.d i' j) := by
rw [← eqToHom_comp_d C r r']
apply imageSubobject_iso_comp
#align homological_complex.image_eq_image HomologicalComplex.image_eq_image
section
/-- Either `C.X i`, if there is some `i` with `c.Rel i j`, or `C.X j`. -/
abbrev xPrev (j : ι) : V :=
C.X (c.prev j)
set_option linter.uppercaseLean3 false in
#align homological_complex.X_prev HomologicalComplex.xPrev
/-- If `c.Rel i j`, then `C.xPrev j` is isomorphic to `C.X i`. -/
def xPrevIso {i j : ι} (r : c.Rel i j) : C.xPrev j ≅ C.X i :=
eqToIso <| by rw [← c.prev_eq' r]
set_option linter.uppercaseLean3 false in
#align homological_complex.X_prev_iso HomologicalComplex.xPrevIso
/-- If there is no `i` so `c.Rel i j`, then `C.xPrev j` is isomorphic to `C.X j`. -/
def xPrevIsoSelf {j : ι} (h : ¬c.Rel (c.prev j) j) : C.xPrev j ≅ C.X j :=
eqToIso <|
congr_arg C.X
(by
dsimp [ComplexShape.prev]
rw [dif_neg]
push_neg; intro i hi
have : c.prev j = i := c.prev_eq' hi
rw [this] at h; contradiction)
set_option linter.uppercaseLean3 false in
#align homological_complex.X_prev_iso_self HomologicalComplex.xPrevIsoSelf
/-- Either `C.X j`, if there is some `j` with `c.rel i j`, or `C.X i`. -/
abbrev xNext (i : ι) : V :=
C.X (c.next i)
set_option linter.uppercaseLean3 false in
#align homological_complex.X_next HomologicalComplex.xNext
/-- If `c.Rel i j`, then `C.xNext i` is isomorphic to `C.X j`. -/
def xNextIso {i j : ι} (r : c.Rel i j) : C.xNext i ≅ C.X j :=
eqToIso <| by rw [← c.next_eq' r]
set_option linter.uppercaseLean3 false in
#align homological_complex.X_next_iso HomologicalComplex.xNextIso
/-- If there is no `j` so `c.Rel i j`, then `C.xNext i` is isomorphic to `C.X i`. -/
def xNextIsoSelf {i : ι} (h : ¬c.Rel i (c.next i)) : C.xNext i ≅ C.X i :=
eqToIso <|
congr_arg C.X
(by
dsimp [ComplexShape.next]
rw [dif_neg]; rintro ⟨j, hj⟩
have : c.next i = j := c.next_eq' hj
rw [this] at h; contradiction)
set_option linter.uppercaseLean3 false in
#align homological_complex.X_next_iso_self HomologicalComplex.xNextIsoSelf
/-- The differential mapping into `C.X j`, or zero if there isn't one.
-/
abbrev dTo (j : ι) : C.xPrev j ⟶ C.X j :=
C.d (c.prev j) j
#align homological_complex.d_to HomologicalComplex.dTo
/-- The differential mapping out of `C.X i`, or zero if there isn't one.
-/
abbrev dFrom (i : ι) : C.X i ⟶ C.xNext i :=
C.d i (c.next i)
#align homological_complex.d_from HomologicalComplex.dFrom
theorem dTo_eq {i j : ι} (r : c.Rel i j) : C.dTo j = (C.xPrevIso r).hom ≫ C.d i j := by
obtain rfl := c.prev_eq' r
exact (Category.id_comp _).symm
#align homological_complex.d_to_eq HomologicalComplex.dTo_eq
@[simp]
theorem dTo_eq_zero {j : ι} (h : ¬c.Rel (c.prev j) j) : C.dTo j = 0 :=
C.shape _ _ h
#align homological_complex.d_to_eq_zero HomologicalComplex.dTo_eq_zero
theorem dFrom_eq {i j : ι} (r : c.Rel i j) : C.dFrom i = C.d i j ≫ (C.xNextIso r).inv := by
obtain rfl := c.next_eq' r
exact (Category.comp_id _).symm
#align homological_complex.d_from_eq HomologicalComplex.dFrom_eq
@[simp]
theorem dFrom_eq_zero {i : ι} (h : ¬c.Rel i (c.next i)) : C.dFrom i = 0 :=
C.shape _ _ h
#align homological_complex.d_from_eq_zero HomologicalComplex.dFrom_eq_zero
@[reassoc (attr := simp)]
theorem xPrevIso_comp_dTo {i j : ι} (r : c.Rel i j) : (C.xPrevIso r).inv ≫ C.dTo j = C.d i j := by
simp [C.dTo_eq r]
set_option linter.uppercaseLean3 false in
#align homological_complex.X_prev_iso_comp_d_to HomologicalComplex.xPrevIso_comp_dTo
@[reassoc (attr := simp)]
theorem xPrevIsoSelf_comp_dTo {j : ι} (h : ¬c.Rel (c.prev j) j) :
(C.xPrevIsoSelf h).inv ≫ C.dTo j = 0 := by simp [h]
set_option linter.uppercaseLean3 false in
#align homological_complex.X_prev_iso_self_comp_d_to HomologicalComplex.xPrevIsoSelf_comp_dTo
@[reassoc (attr := simp)]
theorem dFrom_comp_xNextIso {i j : ι} (r : c.Rel i j) :
C.dFrom i ≫ (C.xNextIso r).hom = C.d i j := by
simp [C.dFrom_eq r]
set_option linter.uppercaseLean3 false in
#align homological_complex.d_from_comp_X_next_iso HomologicalComplex.dFrom_comp_xNextIso
@[reassoc (attr := simp)]
theorem dFrom_comp_xNextIsoSelf {i : ι} (h : ¬c.Rel i (c.next i)) :
C.dFrom i ≫ (C.xNextIsoSelf h).hom = 0 := by simp [h]
set_option linter.uppercaseLean3 false in
#align homological_complex.d_from_comp_X_next_iso_self HomologicalComplex.dFrom_comp_xNextIsoSelf
@[simp 1100]
theorem dTo_comp_dFrom (j : ι) : C.dTo j ≫ C.dFrom j = 0 :=
C.d_comp_d _ _ _
#align homological_complex.d_to_comp_d_from HomologicalComplex.dTo_comp_dFrom
theorem kernel_from_eq_kernel [HasKernels V] {i j : ι} (r : c.Rel i j) :
kernelSubobject (C.dFrom i) = kernelSubobject (C.d i j) := by
rw [C.dFrom_eq r]
apply kernelSubobject_comp_mono
#align homological_complex.kernel_from_eq_kernel HomologicalComplex.kernel_from_eq_kernel
theorem image_to_eq_image [HasImages V] [HasEqualizers V] {i j : ι} (r : c.Rel i j) :
imageSubobject (C.dTo j) = imageSubobject (C.d i j) := by
rw [C.dTo_eq r]
apply imageSubobject_iso_comp
#align homological_complex.image_to_eq_image HomologicalComplex.image_to_eq_image
end
namespace Hom
variable {C₁ C₂ C₃ : HomologicalComplex V c}
/-- The `i`-th component of an isomorphism of chain complexes. -/
@[simps!]
def isoApp (f : C₁ ≅ C₂) (i : ι) : C₁.X i ≅ C₂.X i :=
(eval V c i).mapIso f
#align homological_complex.hom.iso_app HomologicalComplex.Hom.isoApp
/-- Construct an isomorphism of chain complexes from isomorphism of the objects
which commute with the differentials. -/
@[simps]
def isoOfComponents (f : ∀ i, C₁.X i ≅ C₂.X i)
(hf : ∀ i j, c.Rel i j → (f i).hom ≫ C₂.d i j = C₁.d i j ≫ (f j).hom := by aesop_cat) :
C₁ ≅ C₂ where
hom :=
{ f := fun i => (f i).hom
comm' := hf }
inv :=
{ f := fun i => (f i).inv
comm' := fun i j hij =>
calc
(f i).inv ≫ C₁.d i j = (f i).inv ≫ (C₁.d i j ≫ (f j).hom) ≫ (f j).inv := by simp
_ = (f i).inv ≫ ((f i).hom ≫ C₂.d i j) ≫ (f j).inv := by rw [hf i j hij]
_ = C₂.d i j ≫ (f j).inv := by simp }
hom_inv_id := by
ext i
exact (f i).hom_inv_id
inv_hom_id := by
ext i
exact (f i).inv_hom_id
#align homological_complex.hom.iso_of_components HomologicalComplex.Hom.isoOfComponents
@[simp]
| Mathlib/Algebra/Homology/HomologicalComplex.lean | 585 | 589 | theorem isoOfComponents_app (f : ∀ i, C₁.X i ≅ C₂.X i)
(hf : ∀ i j, c.Rel i j → (f i).hom ≫ C₂.d i j = C₁.d i j ≫ (f j).hom) (i : ι) :
isoApp (isoOfComponents f hf) i = f i := by |
ext
simp
|
/-
Copyright (c) 2021 Yaël Dillies, Bhavik Mehta. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yaël Dillies, Bhavik Mehta, Huỳnh Trần Khanh, Stuart Presnell
-/
import Mathlib.Algebra.BigOperators.Group.Finset
import Mathlib.Data.Finset.Sym
import Mathlib.Data.Fintype.Sum
import Mathlib.Data.Fintype.Prod
#align_import data.sym.card from "leanprover-community/mathlib"@"0bd2ea37bcba5769e14866170f251c9bc64e35d7"
/-!
# Stars and bars
In this file, we prove (in `Sym.card_sym_eq_multichoose`) that the function `multichoose n k`
defined in `Data/Nat/Choose/Basic` counts the number of multisets of cardinality `k` over an
alphabet of cardinality `n`. In conjunction with `Nat.multichoose_eq` proved in
`Data/Nat/Choose/Basic`, which shows that `multichoose n k = choose (n + k - 1) k`,
this is central to the "stars and bars" technique in combinatorics, where we switch between
counting multisets of size `k` over an alphabet of size `n` to counting strings of `k` elements
("stars") separated by `n-1` dividers ("bars").
## Informal statement
Many problems in mathematics are of the form of (or can be reduced to) putting `k` indistinguishable
objects into `n` distinguishable boxes; for example, the problem of finding natural numbers
`x1, ..., xn` whose sum is `k`. This is equivalent to forming a multiset of cardinality `k` from
an alphabet of cardinality `n` -- for each box `i ∈ [1, n]` the multiset contains as many copies
of `i` as there are items in the `i`th box.
The "stars and bars" technique arises from another way of presenting the same problem. Instead of
putting `k` items into `n` boxes, we take a row of `k` items (the "stars") and separate them by
inserting `n-1` dividers (the "bars"). For example, the pattern `*|||**|*|` exhibits 4 items
distributed into 6 boxes -- note that any box, including the first and last, may be empty.
Such arrangements of `k` stars and `n-1` bars are in 1-1 correspondence with multisets of size `k`
over an alphabet of size `n`, and are counted by `choose (n + k - 1) k`.
Note that this problem is one component of Gian-Carlo Rota's "Twelvefold Way"
https://en.wikipedia.org/wiki/Twelvefold_way
## Formal statement
Here we generalise the alphabet to an arbitrary fintype `α`, and we use `Sym α k` as the type of
multisets of size `k` over `α`. Thus the statement that these are counted by `multichoose` is:
`Sym.card_sym_eq_multichoose : card (Sym α k) = multichoose (card α) k`
while the "stars and bars" technique gives
`Sym.card_sym_eq_choose : card (Sym α k) = choose (card α + k - 1) k`
## Tags
stars and bars, multichoose
-/
open Finset Fintype Function Sum Nat
variable {α β : Type*}
namespace Sym
section Sym
variable (α) (n : ℕ)
/-- Over `Fin (n + 1)`, the multisets of size `k + 1` containing `0` are equivalent to those of size
`k`, as demonstrated by respectively erasing or appending `0`. -/
protected def e1 {n k : ℕ} : { s : Sym (Fin (n + 1)) (k + 1) // ↑0 ∈ s } ≃ Sym (Fin n.succ) k where
toFun s := s.1.erase 0 s.2
invFun s := ⟨cons 0 s, mem_cons_self 0 s⟩
left_inv s := by simp
right_inv s := by simp
set_option linter.uppercaseLean3 false in
#align sym.E1 Sym.e1
/-- The multisets of size `k` over `Fin n+2` not containing `0`
are equivalent to those of size `k` over `Fin n+1`,
as demonstrated by respectively decrementing or incrementing every element of the multiset.
-/
protected def e2 {n k : ℕ} : { s : Sym (Fin n.succ.succ) k // ↑0 ∉ s } ≃ Sym (Fin n.succ) k where
toFun s := map (Fin.predAbove 0) s.1
invFun s :=
⟨map (Fin.succAbove 0) s,
(mt mem_map.1) (not_exists.2 fun t => not_and.2 fun _ => Fin.succAbove_ne _ t)⟩
left_inv s := by
ext1
simp only [map_map]
refine (Sym.map_congr fun v hv ↦ ?_).trans (map_id' _)
exact Fin.succAbove_predAbove (ne_of_mem_of_not_mem hv s.2)
right_inv s := by
simp only [map_map, comp_apply, ← Fin.castSucc_zero, Fin.predAbove_succAbove, map_id']
set_option linter.uppercaseLean3 false in
#align sym.E2 Sym.e2
-- Porting note: use eqn compiler instead of `pincerRecursion` to make cases more readable
theorem card_sym_fin_eq_multichoose : ∀ n k : ℕ, card (Sym (Fin n) k) = multichoose n k
| n, 0 => by simp
| 0, k + 1 => by rw [multichoose_zero_succ]; exact card_eq_zero
| 1, k + 1 => by simp
| n + 2, k + 1 => by
rw [multichoose_succ_succ, ← card_sym_fin_eq_multichoose (n + 1) (k + 1),
← card_sym_fin_eq_multichoose (n + 2) k, add_comm (Fintype.card _), ← card_sum]
refine Fintype.card_congr (Equiv.symm ?_)
apply (Sym.e1.symm.sumCongr Sym.e2.symm).trans
apply Equiv.sumCompl
#align sym.card_sym_fin_eq_multichoose Sym.card_sym_fin_eq_multichoose
/-- For any fintype `α` of cardinality `n`, `card (Sym α k) = multichoose (card α) k`. -/
theorem card_sym_eq_multichoose (α : Type*) (k : ℕ) [Fintype α] [Fintype (Sym α k)] :
card (Sym α k) = multichoose (card α) k := by
rw [← card_sym_fin_eq_multichoose]
-- FIXME: Without the `Fintype` namespace, why does it complain about `Finset.card_congr` being
-- deprecated?
exact Fintype.card_congr (equivCongr (equivFin α))
#align sym.card_sym_eq_multichoose Sym.card_sym_eq_multichoose
/-- The *stars and bars* lemma: the cardinality of `Sym α k` is equal to
`Nat.choose (card α + k - 1) k`. -/
theorem card_sym_eq_choose {α : Type*} [Fintype α] (k : ℕ) [Fintype (Sym α k)] :
card (Sym α k) = (card α + k - 1).choose k := by
rw [card_sym_eq_multichoose, Nat.multichoose_eq]
#align sym.card_sym_eq_choose Sym.card_sym_eq_choose
end Sym
end Sym
namespace Sym2
variable [DecidableEq α]
/-- The `diag` of `s : Finset α` is sent on a finset of `Sym2 α` of card `s.card`. -/
theorem card_image_diag (s : Finset α) : (s.diag.image Sym2.mk).card = s.card := by
rw [card_image_of_injOn, diag_card]
rintro ⟨x₀, x₁⟩ hx _ _ h
cases Sym2.eq.1 h
· rfl
· simp only [mem_coe, mem_diag] at hx
rw [hx.2]
#align sym2.card_image_diag Sym2.card_image_diag
| Mathlib/Data/Sym/Card.lean | 143 | 161 | theorem two_mul_card_image_offDiag (s : Finset α) :
2 * (s.offDiag.image Sym2.mk).card = s.offDiag.card := by |
rw [card_eq_sum_card_image (Sym2.mk : α × α → _), sum_const_nat (Sym2.ind _), mul_comm]
rintro x y hxy
simp_rw [mem_image, mem_offDiag] at hxy
obtain ⟨a, ⟨ha₁, ha₂, ha⟩, h⟩ := hxy
replace h := Sym2.eq.1 h
obtain ⟨hx, hy, hxy⟩ : x ∈ s ∧ y ∈ s ∧ x ≠ y := by
cases h <;> refine ⟨‹_›, ‹_›, ?_⟩ <;> [exact ha; exact ha.symm]
have hxy' : y ≠ x := hxy.symm
have : (s.offDiag.filter fun z => Sym2.mk z = s(x, y)) = ({(x, y), (y, x)} : Finset _) := by
ext ⟨x₁, y₁⟩
rw [mem_filter, mem_insert, mem_singleton, Sym2.eq_iff, Prod.mk.inj_iff, Prod.mk.inj_iff,
and_iff_right_iff_imp]
-- `hxy'` is used in `exact`
rintro (⟨rfl, rfl⟩ | ⟨rfl, rfl⟩) <;> rw [mem_offDiag] <;> exact ⟨‹_›, ‹_›, ‹_›⟩
rw [this, card_insert_of_not_mem, card_singleton]
simp only [not_and, Prod.mk.inj_iff, mem_singleton]
exact fun _ => hxy'
|
/-
Copyright (c) 2018 Mario Carneiro. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro, Chris Hughes, Floris van Doorn, Yaël Dillies
-/
import Mathlib.Data.Nat.Defs
import Mathlib.Tactic.GCongr.Core
import Mathlib.Tactic.Common
import Mathlib.Tactic.Monotonicity.Attr
#align_import data.nat.factorial.basic from "leanprover-community/mathlib"@"d012cd09a9b256d870751284dd6a29882b0be105"
/-!
# Factorial and variants
This file defines the factorial, along with the ascending and descending variants.
## Main declarations
* `Nat.factorial`: The factorial.
* `Nat.ascFactorial`: The ascending factorial. It is the product of natural numbers from `n` to
`n + k - 1`.
* `Nat.descFactorial`: The descending factorial. It is the product of natural numbers from
`n - k + 1` to `n`.
-/
namespace Nat
/-- `Nat.factorial n` is the factorial of `n`. -/
def factorial : ℕ → ℕ
| 0 => 1
| succ n => succ n * factorial n
#align nat.factorial Nat.factorial
/-- factorial notation `n!` -/
scoped notation:10000 n "!" => Nat.factorial n
section Factorial
variable {m n : ℕ}
@[simp] theorem factorial_zero : 0! = 1 :=
rfl
#align nat.factorial_zero Nat.factorial_zero
theorem factorial_succ (n : ℕ) : (n + 1)! = (n + 1) * n ! :=
rfl
#align nat.factorial_succ Nat.factorial_succ
@[simp] theorem factorial_one : 1! = 1 :=
rfl
#align nat.factorial_one Nat.factorial_one
@[simp] theorem factorial_two : 2! = 2 :=
rfl
#align nat.factorial_two Nat.factorial_two
theorem mul_factorial_pred (hn : 0 < n) : n * (n - 1)! = n ! :=
Nat.sub_add_cancel (Nat.succ_le_of_lt hn) ▸ rfl
#align nat.mul_factorial_pred Nat.mul_factorial_pred
theorem factorial_pos : ∀ n, 0 < n !
| 0 => Nat.zero_lt_one
| succ n => Nat.mul_pos (succ_pos _) (factorial_pos n)
#align nat.factorial_pos Nat.factorial_pos
theorem factorial_ne_zero (n : ℕ) : n ! ≠ 0 :=
ne_of_gt (factorial_pos _)
#align nat.factorial_ne_zero Nat.factorial_ne_zero
theorem factorial_dvd_factorial {m n} (h : m ≤ n) : m ! ∣ n ! := by
induction' h with n _ ih
· exact Nat.dvd_refl _
· exact Nat.dvd_trans ih (Nat.dvd_mul_left _ _)
#align nat.factorial_dvd_factorial Nat.factorial_dvd_factorial
theorem dvd_factorial : ∀ {m n}, 0 < m → m ≤ n → m ∣ n !
| succ _, _, _, h => Nat.dvd_trans (Nat.dvd_mul_right _ _) (factorial_dvd_factorial h)
#align nat.dvd_factorial Nat.dvd_factorial
@[mono, gcongr]
theorem factorial_le {m n} (h : m ≤ n) : m ! ≤ n ! :=
le_of_dvd (factorial_pos _) (factorial_dvd_factorial h)
#align nat.factorial_le Nat.factorial_le
theorem factorial_mul_pow_le_factorial : ∀ {m n : ℕ}, m ! * (m + 1) ^ n ≤ (m + n)!
| m, 0 => by simp
| m, n + 1 => by
rw [← Nat.add_assoc, factorial_succ, Nat.mul_comm (_ + 1), Nat.pow_succ, ← Nat.mul_assoc]
exact Nat.mul_le_mul factorial_mul_pow_le_factorial (succ_le_succ (le_add_right _ _))
#align nat.factorial_mul_pow_le_factorial Nat.factorial_mul_pow_le_factorial
theorem factorial_lt (hn : 0 < n) : n ! < m ! ↔ n < m := by
refine ⟨fun h => not_le.mp fun hmn => Nat.not_le_of_lt h (factorial_le hmn), fun h => ?_⟩
have : ∀ {n}, 0 < n → n ! < (n + 1)! := by
intro k hk
rw [factorial_succ, succ_mul, Nat.lt_add_left_iff_pos]
exact Nat.mul_pos hk k.factorial_pos
induction' h with k hnk ih generalizing hn
· exact this hn
· exact lt_trans (ih hn) $ this <| lt_trans hn <| lt_of_succ_le hnk
#align nat.factorial_lt Nat.factorial_lt
@[gcongr]
lemma factorial_lt_of_lt {m n : ℕ} (hn : 0 < n) (h : n < m) : n ! < m ! := (factorial_lt hn).mpr h
@[simp] lemma one_lt_factorial : 1 < n ! ↔ 1 < n := factorial_lt Nat.one_pos
#align nat.one_lt_factorial Nat.one_lt_factorial
@[simp]
theorem factorial_eq_one : n ! = 1 ↔ n ≤ 1 := by
constructor
· intro h
rw [← not_lt, ← one_lt_factorial, h]
apply lt_irrefl
· rintro (_|_|_) <;> rfl
#align nat.factorial_eq_one Nat.factorial_eq_one
theorem factorial_inj (hn : 1 < n) : n ! = m ! ↔ n = m := by
refine ⟨fun h => ?_, congr_arg _⟩
obtain hnm | rfl | hnm := lt_trichotomy n m
· rw [← factorial_lt <| lt_of_succ_lt hn, h] at hnm
cases lt_irrefl _ hnm
· rfl
rw [← one_lt_factorial, h, one_lt_factorial] at hn
rw [← factorial_lt <| lt_of_succ_lt hn, h] at hnm
cases lt_irrefl _ hnm
#align nat.factorial_inj Nat.factorial_inj
theorem factorial_inj' (h : 1 < n ∨ 1 < m) : n ! = m ! ↔ n = m := by
obtain hn|hm := h
· exact factorial_inj hn
· rw [eq_comm, factorial_inj hm, eq_comm]
theorem self_le_factorial : ∀ n : ℕ, n ≤ n !
| 0 => Nat.zero_le _
| k + 1 => Nat.le_mul_of_pos_right _ (Nat.one_le_of_lt k.factorial_pos)
#align nat.self_le_factorial Nat.self_le_factorial
theorem lt_factorial_self {n : ℕ} (hi : 3 ≤ n) : n < n ! := by
have : 0 < n := by omega
have hn : 1 < pred n := le_pred_of_lt (succ_le_iff.mp hi)
rw [← succ_pred_eq_of_pos ‹0 < n›, factorial_succ]
exact (Nat.lt_mul_iff_one_lt_right (pred n).succ_pos).2
((Nat.lt_of_lt_of_le hn (self_le_factorial _)))
#align nat.lt_factorial_self Nat.lt_factorial_self
theorem add_factorial_succ_lt_factorial_add_succ {i : ℕ} (n : ℕ) (hi : 2 ≤ i) :
i + (n + 1)! < (i + n + 1)! := by
rw [factorial_succ (i + _), Nat.add_mul, Nat.one_mul]
have := (i + n).self_le_factorial
refine Nat.add_lt_add_of_lt_of_le (Nat.lt_of_le_of_lt ?_ ((Nat.lt_mul_iff_one_lt_right ?_).2 ?_))
(factorial_le ?_) <;> omega
#align nat.add_factorial_succ_lt_factorial_add_succ Nat.add_factorial_succ_lt_factorial_add_succ
theorem add_factorial_lt_factorial_add {i n : ℕ} (hi : 2 ≤ i) (hn : 1 ≤ n) :
i + n ! < (i + n)! := by
cases hn
· rw [factorial_one]
exact lt_factorial_self (succ_le_succ hi)
exact add_factorial_succ_lt_factorial_add_succ _ hi
#align nat.add_factorial_lt_factorial_add Nat.add_factorial_lt_factorial_add
theorem add_factorial_succ_le_factorial_add_succ (i : ℕ) (n : ℕ) :
i + (n + 1)! ≤ (i + (n + 1))! := by
cases (le_or_lt (2 : ℕ) i)
· rw [← Nat.add_assoc]
apply Nat.le_of_lt
apply add_factorial_succ_lt_factorial_add_succ
assumption
· match i with
| 0 => simp
| 1 =>
rw [← Nat.add_assoc, factorial_succ (1 + n), Nat.add_mul, Nat.one_mul, Nat.add_comm 1 n,
Nat.add_le_add_iff_right]
exact Nat.mul_pos n.succ_pos n.succ.factorial_pos
| succ (succ n) => contradiction
#align nat.add_factorial_succ_le_factorial_add_succ Nat.add_factorial_succ_le_factorial_add_succ
theorem add_factorial_le_factorial_add (i : ℕ) {n : ℕ} (n1 : 1 ≤ n) : i + n ! ≤ (i + n)! := by
cases' n1 with h
· exact self_le_factorial _
exact add_factorial_succ_le_factorial_add_succ i h
#align nat.add_factorial_le_factorial_add Nat.add_factorial_le_factorial_add
theorem factorial_mul_pow_sub_le_factorial {n m : ℕ} (hnm : n ≤ m) : n ! * n ^ (m - n) ≤ m ! := by
calc
_ ≤ n ! * (n + 1) ^ (m - n) := Nat.mul_le_mul_left _ (Nat.pow_le_pow_left n.le_succ _)
_ ≤ _ := by simpa [hnm] using @Nat.factorial_mul_pow_le_factorial n (m - n)
#align nat.factorial_mul_pow_sub_le_factorial Nat.factorial_mul_pow_sub_le_factorial
lemma factorial_le_pow : ∀ n, n ! ≤ n ^ n
| 0 => le_refl _
| n + 1 =>
calc
_ ≤ (n + 1) * n ^ n := Nat.mul_le_mul_left _ n.factorial_le_pow
_ ≤ (n + 1) * (n + 1) ^ n := Nat.mul_le_mul_left _ (Nat.pow_le_pow_left n.le_succ _)
_ = _ := by rw [pow_succ']
end Factorial
/-! ### Ascending and descending factorials -/
section AscFactorial
/-- `n.ascFactorial k = n (n + 1) ⋯ (n + k - 1)`. This is closely related to `ascPochhammer`, but
much less general. -/
def ascFactorial (n : ℕ) : ℕ → ℕ
| 0 => 1
| k + 1 => (n + k) * ascFactorial n k
#align nat.asc_factorial Nat.ascFactorial
@[simp]
theorem ascFactorial_zero (n : ℕ) : n.ascFactorial 0 = 1 :=
rfl
#align nat.asc_factorial_zero Nat.ascFactorial_zero
theorem ascFactorial_succ {n k : ℕ} : n.ascFactorial k.succ = (n + k) * n.ascFactorial k :=
rfl
#align nat.asc_factorial_succ Nat.ascFactorial_succ
theorem zero_ascFactorial : ∀ (k : ℕ), (0 : ℕ).ascFactorial k.succ = 0
| 0 => by
rw [ascFactorial_succ, ascFactorial_zero, Nat.zero_add, Nat.zero_mul]
| (k+1) => by
rw [ascFactorial_succ, zero_ascFactorial k, Nat.mul_zero]
@[simp]
theorem one_ascFactorial : ∀ (k : ℕ), (1 : ℕ).ascFactorial k = k.factorial
| 0 => ascFactorial_zero 1
| (k+1) => by
rw [ascFactorial_succ, one_ascFactorial k, Nat.add_comm, factorial_succ]
theorem succ_ascFactorial (n : ℕ) :
∀ k, n * n.succ.ascFactorial k = (n + k) * n.ascFactorial k
| 0 => by rw [Nat.add_zero, ascFactorial_zero, ascFactorial_zero]
| k + 1 => by rw [ascFactorial, Nat.mul_left_comm, succ_ascFactorial n k, ascFactorial, succ_add,
← Nat.add_assoc]
#align nat.succ_asc_factorial Nat.succ_ascFactorial
/-- `(n + 1).ascFactorial k = (n + k) ! / n !` but without ℕ-division. See
`Nat.ascFactorial_eq_div` for the version with ℕ-division. -/
theorem factorial_mul_ascFactorial (n : ℕ) : ∀ k, n ! * (n + 1).ascFactorial k = (n + k)!
| 0 => by rw [ascFactorial_zero, Nat.add_zero, Nat.mul_one]
| k + 1 => by
rw [ascFactorial_succ, ← Nat.add_assoc, factorial_succ, Nat.mul_comm (n + 1 + k),
← Nat.mul_assoc, factorial_mul_ascFactorial n k, Nat.mul_comm, Nat.add_right_comm]
#align nat.factorial_mul_asc_factorial Nat.factorial_mul_ascFactorial
/-- `n.ascFactorial k = (n + k - 1)! / (n - 1)!` for `n > 0` but without ℕ-division. See
`Nat.ascFactorial_eq_div` for the version with ℕ-division. Consider using
`factorial_mul_ascFactorial` to avoid complications of ℕ-subtraction. -/
theorem factorial_mul_ascFactorial' (n k : ℕ) (h : 0 < n) :
(n - 1) ! * n.ascFactorial k = (n + k - 1)! := by
rw [Nat.sub_add_comm h, Nat.sub_one]
nth_rw 2 [Nat.eq_add_of_sub_eq h rfl]
rw [Nat.sub_one, factorial_mul_ascFactorial]
/-- Avoid in favor of `Nat.factorial_mul_ascFactorial` if you can. ℕ-division isn't worth it. -/
theorem ascFactorial_eq_div (n k : ℕ) : (n + 1).ascFactorial k = (n + k)! / n ! :=
Nat.eq_div_of_mul_eq_right n.factorial_ne_zero (factorial_mul_ascFactorial _ _)
/-- Avoid in favor of `Nat.factorial_mul_ascFactorial'` if you can. ℕ-division isn't worth it. -/
theorem ascFactorial_eq_div' (n k : ℕ) (h : 0 < n) :
n.ascFactorial k = (n + k - 1)! / (n - 1) ! :=
Nat.eq_div_of_mul_eq_right (n - 1).factorial_ne_zero (factorial_mul_ascFactorial' _ _ h)
#align nat.asc_factorial_eq_div Nat.ascFactorial_eq_div
theorem ascFactorial_of_sub {n k : ℕ}:
(n - k) * (n - k + 1).ascFactorial k = (n - k).ascFactorial (k + 1) := by
rw [succ_ascFactorial, ascFactorial_succ]
#align nat.asc_factorial_of_sub Nat.ascFactorial_of_sub
theorem pow_succ_le_ascFactorial (n : ℕ) : ∀ k : ℕ, n ^ k ≤ n.ascFactorial k
| 0 => by rw [ascFactorial_zero, Nat.pow_zero]
| k + 1 => by
rw [Nat.pow_succ, Nat.mul_comm, ascFactorial_succ, ← succ_ascFactorial]
exact Nat.mul_le_mul (Nat.le_refl n)
(Nat.le_trans (Nat.pow_le_pow_left (le_succ n) k) (pow_succ_le_ascFactorial n.succ k))
#align nat.pow_succ_le_asc_factorial Nat.pow_succ_le_ascFactorial
theorem pow_lt_ascFactorial' (n k : ℕ) : (n + 1) ^ (k + 2) < (n + 1).ascFactorial (k + 2) := by
rw [Nat.pow_succ, ascFactorial, Nat.mul_comm]
exact Nat.mul_lt_mul_of_lt_of_le' (Nat.lt_add_of_pos_right k.succ_pos)
(pow_succ_le_ascFactorial n.succ _) (Nat.pow_pos n.succ_pos)
#align nat.pow_lt_asc_factorial' Nat.pow_lt_ascFactorial'
theorem pow_lt_ascFactorial (n : ℕ) : ∀ {k : ℕ}, 2 ≤ k → (n + 1) ^ k < (n + 1).ascFactorial k
| 0 => by rintro ⟨⟩
| 1 => by intro; contradiction
| k + 2 => fun _ => pow_lt_ascFactorial' n k
#align nat.pow_lt_asc_factorial Nat.pow_lt_ascFactorial
theorem ascFactorial_le_pow_add (n : ℕ) : ∀ k : ℕ, (n+1).ascFactorial k ≤ (n + k) ^ k
| 0 => by rw [ascFactorial_zero, Nat.pow_zero]
| k + 1 => by
rw [ascFactorial_succ, Nat.pow_succ, Nat.mul_comm, ← Nat.add_assoc, Nat.add_right_comm n 1 k]
exact Nat.mul_le_mul_right _
(Nat.le_trans (ascFactorial_le_pow_add _ k) (Nat.pow_le_pow_left (le_succ _) _))
#align nat.asc_factorial_le_pow_add Nat.ascFactorial_le_pow_add
theorem ascFactorial_lt_pow_add (n : ℕ) : ∀ {k : ℕ}, 2 ≤ k → (n + 1).ascFactorial k < (n + k) ^ k
| 0 => by rintro ⟨⟩
| 1 => by intro; contradiction
| k + 2 => fun _ => by
rw [Nat.pow_succ, Nat.mul_comm, ascFactorial_succ, succ_add_eq_add_succ n (k + 1)]
exact Nat.mul_lt_mul_of_le_of_lt (le_refl _) (Nat.lt_of_le_of_lt (ascFactorial_le_pow_add n _)
(Nat.pow_lt_pow_left (Nat.lt_succ_self _) k.succ_ne_zero)) (succ_pos _)
#align nat.asc_factorial_lt_pow_add Nat.ascFactorial_lt_pow_add
theorem ascFactorial_pos (n k : ℕ) : 0 < (n + 1).ascFactorial k :=
Nat.lt_of_lt_of_le (Nat.pow_pos n.succ_pos) (pow_succ_le_ascFactorial (n + 1) k)
#align nat.asc_factorial_pos Nat.ascFactorial_pos
end AscFactorial
section DescFactorial
/-- `n.descFactorial k = n! / (n - k)!` (as seen in `Nat.descFactorial_eq_div`), but
implemented recursively to allow for "quick" computation when using `norm_num`. This is closely
related to `descPochhammer`, but much less general. -/
def descFactorial (n : ℕ) : ℕ → ℕ
| 0 => 1
| k + 1 => (n - k) * descFactorial n k
#align nat.desc_factorial Nat.descFactorial
@[simp]
theorem descFactorial_zero (n : ℕ) : n.descFactorial 0 = 1 :=
rfl
#align nat.desc_factorial_zero Nat.descFactorial_zero
@[simp]
theorem descFactorial_succ (n k : ℕ) : n.descFactorial (k + 1) = (n - k) * n.descFactorial k :=
rfl
#align nat.desc_factorial_succ Nat.descFactorial_succ
| Mathlib/Data/Nat/Factorial/Basic.lean | 340 | 341 | theorem zero_descFactorial_succ (k : ℕ) : (0 : ℕ).descFactorial (k + 1) = 0 := by |
rw [descFactorial_succ, Nat.zero_sub, Nat.zero_mul]
|
/-
Copyright (c) 2015, 2017 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad, Robert Y. Lewis, Johannes Hölzl, Mario Carneiro, Sébastien Gouëzel
-/
import Mathlib.Topology.EMetricSpace.Basic
import Mathlib.Topology.Bornology.Constructions
import Mathlib.Data.Set.Pointwise.Interval
import Mathlib.Topology.Order.DenselyOrdered
/-!
## Pseudo-metric spaces
This file defines pseudo-metric spaces: these differ from metric spaces by not imposing the
condition `dist x y = 0 → x = y`.
Many definitions and theorems expected on (pseudo-)metric spaces are already introduced on uniform
spaces and topological spaces. For example: open and closed sets, compactness, completeness,
continuity and uniform continuity.
## Main definitions
* `Dist α`: Endows a space `α` with a function `dist a b`.
* `PseudoMetricSpace α`: A space endowed with a distance function, which can
be zero even if the two elements are non-equal.
* `Metric.ball x ε`: The set of all points `y` with `dist y x < ε`.
* `Metric.Bounded s`: Whether a subset of a `PseudoMetricSpace` is bounded.
* `MetricSpace α`: A `PseudoMetricSpace` with the guarantee `dist x y = 0 → x = y`.
Additional useful definitions:
* `nndist a b`: `dist` as a function to the non-negative reals.
* `Metric.closedBall x ε`: The set of all points `y` with `dist y x ≤ ε`.
* `Metric.sphere x ε`: The set of all points `y` with `dist y x = ε`.
TODO (anyone): Add "Main results" section.
## Tags
pseudo_metric, dist
-/
open Set Filter TopologicalSpace Bornology
open scoped ENNReal NNReal Uniformity Topology
universe u v w
variable {α : Type u} {β : Type v} {X ι : Type*}
theorem UniformSpace.ofDist_aux (ε : ℝ) (hε : 0 < ε) : ∃ δ > (0 : ℝ), ∀ x < δ, ∀ y < δ, x + y < ε :=
⟨ε / 2, half_pos hε, fun _x hx _y hy => add_halves ε ▸ add_lt_add hx hy⟩
/-- Construct a uniform structure from a distance function and metric space axioms -/
def UniformSpace.ofDist (dist : α → α → ℝ) (dist_self : ∀ x : α, dist x x = 0)
(dist_comm : ∀ x y : α, dist x y = dist y x)
(dist_triangle : ∀ x y z : α, dist x z ≤ dist x y + dist y z) : UniformSpace α :=
.ofFun dist dist_self dist_comm dist_triangle ofDist_aux
#align uniform_space_of_dist UniformSpace.ofDist
-- Porting note: dropped the `dist_self` argument
/-- Construct a bornology from a distance function and metric space axioms. -/
abbrev Bornology.ofDist {α : Type*} (dist : α → α → ℝ) (dist_comm : ∀ x y, dist x y = dist y x)
(dist_triangle : ∀ x y z, dist x z ≤ dist x y + dist y z) : Bornology α :=
Bornology.ofBounded { s : Set α | ∃ C, ∀ ⦃x⦄, x ∈ s → ∀ ⦃y⦄, y ∈ s → dist x y ≤ C }
⟨0, fun x hx y => hx.elim⟩ (fun s ⟨c, hc⟩ t h => ⟨c, fun x hx y hy => hc (h hx) (h hy)⟩)
(fun s hs t ht => by
rcases s.eq_empty_or_nonempty with rfl | ⟨x, hx⟩
· rwa [empty_union]
rcases t.eq_empty_or_nonempty with rfl | ⟨y, hy⟩
· rwa [union_empty]
rsuffices ⟨C, hC⟩ : ∃ C, ∀ z ∈ s ∪ t, dist x z ≤ C
· refine ⟨C + C, fun a ha b hb => (dist_triangle a x b).trans ?_⟩
simpa only [dist_comm] using add_le_add (hC _ ha) (hC _ hb)
rcases hs with ⟨Cs, hs⟩; rcases ht with ⟨Ct, ht⟩
refine ⟨max Cs (dist x y + Ct), fun z hz => hz.elim
(fun hz => (hs hx hz).trans (le_max_left _ _))
(fun hz => (dist_triangle x y z).trans <|
(add_le_add le_rfl (ht hy hz)).trans (le_max_right _ _))⟩)
fun z => ⟨dist z z, forall_eq.2 <| forall_eq.2 le_rfl⟩
#align bornology.of_dist Bornology.ofDistₓ
/-- The distance function (given an ambient metric space on `α`), which returns
a nonnegative real number `dist x y` given `x y : α`. -/
@[ext]
class Dist (α : Type*) where
dist : α → α → ℝ
#align has_dist Dist
export Dist (dist)
-- the uniform structure and the emetric space structure are embedded in the metric space structure
-- to avoid instance diamond issues. See Note [forgetful inheritance].
/-- This is an internal lemma used inside the default of `PseudoMetricSpace.edist`. -/
private theorem dist_nonneg' {α} {x y : α} (dist : α → α → ℝ)
(dist_self : ∀ x : α, dist x x = 0) (dist_comm : ∀ x y : α, dist x y = dist y x)
(dist_triangle : ∀ x y z : α, dist x z ≤ dist x y + dist y z) : 0 ≤ dist x y :=
have : 0 ≤ 2 * dist x y :=
calc 0 = dist x x := (dist_self _).symm
_ ≤ dist x y + dist y x := dist_triangle _ _ _
_ = 2 * dist x y := by rw [two_mul, dist_comm]
nonneg_of_mul_nonneg_right this two_pos
#noalign pseudo_metric_space.edist_dist_tac -- Porting note (#11215): TODO: restore
/-- Pseudo metric and Metric spaces
A pseudo metric space is endowed with a distance for which the requirement `d(x,y)=0 → x = y` might
not hold. A metric space is a pseudo metric space such that `d(x,y)=0 → x = y`.
Each pseudo metric space induces a canonical `UniformSpace` and hence a canonical
`TopologicalSpace` This is enforced in the type class definition, by extending the `UniformSpace`
structure. When instantiating a `PseudoMetricSpace` structure, the uniformity fields are not
necessary, they will be filled in by default. In the same way, each (pseudo) metric space induces a
(pseudo) emetric space structure. It is included in the structure, but filled in by default.
-/
class PseudoMetricSpace (α : Type u) extends Dist α : Type u where
dist_self : ∀ x : α, dist x x = 0
dist_comm : ∀ x y : α, dist x y = dist y x
dist_triangle : ∀ x y z : α, dist x z ≤ dist x y + dist y z
edist : α → α → ℝ≥0∞ := fun x y => ENNReal.ofNNReal ⟨dist x y, dist_nonneg' _ ‹_› ‹_› ‹_›⟩
edist_dist : ∀ x y : α, edist x y = ENNReal.ofReal (dist x y)
-- Porting note (#11215): TODO: add := by _
toUniformSpace : UniformSpace α := .ofDist dist dist_self dist_comm dist_triangle
uniformity_dist : 𝓤 α = ⨅ ε > 0, 𝓟 { p : α × α | dist p.1 p.2 < ε } := by intros; rfl
toBornology : Bornology α := Bornology.ofDist dist dist_comm dist_triangle
cobounded_sets : (Bornology.cobounded α).sets =
{ s | ∃ C : ℝ, ∀ x ∈ sᶜ, ∀ y ∈ sᶜ, dist x y ≤ C } := by intros; rfl
#align pseudo_metric_space PseudoMetricSpace
/-- Two pseudo metric space structures with the same distance function coincide. -/
@[ext]
theorem PseudoMetricSpace.ext {α : Type*} {m m' : PseudoMetricSpace α}
(h : m.toDist = m'.toDist) : m = m' := by
cases' m with d _ _ _ ed hed U hU B hB
cases' m' with d' _ _ _ ed' hed' U' hU' B' hB'
obtain rfl : d = d' := h
congr
· ext x y : 2
rw [hed, hed']
· exact UniformSpace.ext (hU.trans hU'.symm)
· ext : 2
rw [← Filter.mem_sets, ← Filter.mem_sets, hB, hB']
#align pseudo_metric_space.ext PseudoMetricSpace.ext
variable [PseudoMetricSpace α]
attribute [instance] PseudoMetricSpace.toUniformSpace PseudoMetricSpace.toBornology
-- see Note [lower instance priority]
instance (priority := 200) PseudoMetricSpace.toEDist : EDist α :=
⟨PseudoMetricSpace.edist⟩
#align pseudo_metric_space.to_has_edist PseudoMetricSpace.toEDist
/-- Construct a pseudo-metric space structure whose underlying topological space structure
(definitionally) agrees which a pre-existing topology which is compatible with a given distance
function. -/
def PseudoMetricSpace.ofDistTopology {α : Type u} [TopologicalSpace α] (dist : α → α → ℝ)
(dist_self : ∀ x : α, dist x x = 0) (dist_comm : ∀ x y : α, dist x y = dist y x)
(dist_triangle : ∀ x y z : α, dist x z ≤ dist x y + dist y z)
(H : ∀ s : Set α, IsOpen s ↔ ∀ x ∈ s, ∃ ε > 0, ∀ y, dist x y < ε → y ∈ s) :
PseudoMetricSpace α :=
{ dist := dist
dist_self := dist_self
dist_comm := dist_comm
dist_triangle := dist_triangle
edist_dist := fun x y => by exact ENNReal.coe_nnreal_eq _
toUniformSpace :=
(UniformSpace.ofDist dist dist_self dist_comm dist_triangle).replaceTopology <|
TopologicalSpace.ext_iff.2 fun s ↦ (H s).trans <| forall₂_congr fun x _ ↦
((UniformSpace.hasBasis_ofFun (exists_gt (0 : ℝ)) dist dist_self dist_comm dist_triangle
UniformSpace.ofDist_aux).comap (Prod.mk x)).mem_iff.symm
uniformity_dist := rfl
toBornology := Bornology.ofDist dist dist_comm dist_triangle
cobounded_sets := rfl }
#align pseudo_metric_space.of_dist_topology PseudoMetricSpace.ofDistTopology
@[simp]
theorem dist_self (x : α) : dist x x = 0 :=
PseudoMetricSpace.dist_self x
#align dist_self dist_self
theorem dist_comm (x y : α) : dist x y = dist y x :=
PseudoMetricSpace.dist_comm x y
#align dist_comm dist_comm
theorem edist_dist (x y : α) : edist x y = ENNReal.ofReal (dist x y) :=
PseudoMetricSpace.edist_dist x y
#align edist_dist edist_dist
theorem dist_triangle (x y z : α) : dist x z ≤ dist x y + dist y z :=
PseudoMetricSpace.dist_triangle x y z
#align dist_triangle dist_triangle
theorem dist_triangle_left (x y z : α) : dist x y ≤ dist z x + dist z y := by
rw [dist_comm z]; apply dist_triangle
#align dist_triangle_left dist_triangle_left
theorem dist_triangle_right (x y z : α) : dist x y ≤ dist x z + dist y z := by
rw [dist_comm y]; apply dist_triangle
#align dist_triangle_right dist_triangle_right
theorem dist_triangle4 (x y z w : α) : dist x w ≤ dist x y + dist y z + dist z w :=
calc
dist x w ≤ dist x z + dist z w := dist_triangle x z w
_ ≤ dist x y + dist y z + dist z w := add_le_add_right (dist_triangle x y z) _
#align dist_triangle4 dist_triangle4
theorem dist_triangle4_left (x₁ y₁ x₂ y₂ : α) :
dist x₂ y₂ ≤ dist x₁ y₁ + (dist x₁ x₂ + dist y₁ y₂) := by
rw [add_left_comm, dist_comm x₁, ← add_assoc]
apply dist_triangle4
#align dist_triangle4_left dist_triangle4_left
theorem dist_triangle4_right (x₁ y₁ x₂ y₂ : α) :
dist x₁ y₁ ≤ dist x₁ x₂ + dist y₁ y₂ + dist x₂ y₂ := by
rw [add_right_comm, dist_comm y₁]
apply dist_triangle4
#align dist_triangle4_right dist_triangle4_right
/-- The triangle (polygon) inequality for sequences of points; `Finset.Ico` version. -/
theorem dist_le_Ico_sum_dist (f : ℕ → α) {m n} (h : m ≤ n) :
dist (f m) (f n) ≤ ∑ i ∈ Finset.Ico m n, dist (f i) (f (i + 1)) := by
induction n, h using Nat.le_induction with
| base => rw [Finset.Ico_self, Finset.sum_empty, dist_self]
| succ n hle ihn =>
calc
dist (f m) (f (n + 1)) ≤ dist (f m) (f n) + dist (f n) (f (n + 1)) := dist_triangle _ _ _
_ ≤ (∑ i ∈ Finset.Ico m n, _) + _ := add_le_add ihn le_rfl
_ = ∑ i ∈ Finset.Ico m (n + 1), _ := by
{ rw [Nat.Ico_succ_right_eq_insert_Ico hle, Finset.sum_insert, add_comm]; simp }
#align dist_le_Ico_sum_dist dist_le_Ico_sum_dist
/-- The triangle (polygon) inequality for sequences of points; `Finset.range` version. -/
theorem dist_le_range_sum_dist (f : ℕ → α) (n : ℕ) :
dist (f 0) (f n) ≤ ∑ i ∈ Finset.range n, dist (f i) (f (i + 1)) :=
Nat.Ico_zero_eq_range ▸ dist_le_Ico_sum_dist f (Nat.zero_le n)
#align dist_le_range_sum_dist dist_le_range_sum_dist
/-- A version of `dist_le_Ico_sum_dist` with each intermediate distance replaced
with an upper estimate. -/
theorem dist_le_Ico_sum_of_dist_le {f : ℕ → α} {m n} (hmn : m ≤ n) {d : ℕ → ℝ}
(hd : ∀ {k}, m ≤ k → k < n → dist (f k) (f (k + 1)) ≤ d k) :
dist (f m) (f n) ≤ ∑ i ∈ Finset.Ico m n, d i :=
le_trans (dist_le_Ico_sum_dist f hmn) <|
Finset.sum_le_sum fun _k hk => hd (Finset.mem_Ico.1 hk).1 (Finset.mem_Ico.1 hk).2
#align dist_le_Ico_sum_of_dist_le dist_le_Ico_sum_of_dist_le
/-- A version of `dist_le_range_sum_dist` with each intermediate distance replaced
with an upper estimate. -/
theorem dist_le_range_sum_of_dist_le {f : ℕ → α} (n : ℕ) {d : ℕ → ℝ}
(hd : ∀ {k}, k < n → dist (f k) (f (k + 1)) ≤ d k) :
dist (f 0) (f n) ≤ ∑ i ∈ Finset.range n, d i :=
Nat.Ico_zero_eq_range ▸ dist_le_Ico_sum_of_dist_le (zero_le n) fun _ => hd
#align dist_le_range_sum_of_dist_le dist_le_range_sum_of_dist_le
theorem swap_dist : Function.swap (@dist α _) = dist := by funext x y; exact dist_comm _ _
#align swap_dist swap_dist
theorem abs_dist_sub_le (x y z : α) : |dist x z - dist y z| ≤ dist x y :=
abs_sub_le_iff.2
⟨sub_le_iff_le_add.2 (dist_triangle _ _ _), sub_le_iff_le_add.2 (dist_triangle_left _ _ _)⟩
#align abs_dist_sub_le abs_dist_sub_le
theorem dist_nonneg {x y : α} : 0 ≤ dist x y :=
dist_nonneg' dist dist_self dist_comm dist_triangle
#align dist_nonneg dist_nonneg
namespace Mathlib.Meta.Positivity
open Lean Meta Qq Function
/-- Extension for the `positivity` tactic: distances are nonnegative. -/
@[positivity Dist.dist _ _]
def evalDist : PositivityExt where eval {u α} _zα _pα e := do
match u, α, e with
| 0, ~q(ℝ), ~q(@Dist.dist $β $inst $a $b) =>
let _inst ← synthInstanceQ q(PseudoMetricSpace $β)
assertInstancesCommute
pure (.nonnegative q(dist_nonneg))
| _, _, _ => throwError "not dist"
end Mathlib.Meta.Positivity
example {x y : α} : 0 ≤ dist x y := by positivity
@[simp] theorem abs_dist {a b : α} : |dist a b| = dist a b := abs_of_nonneg dist_nonneg
#align abs_dist abs_dist
/-- A version of `Dist` that takes value in `ℝ≥0`. -/
class NNDist (α : Type*) where
nndist : α → α → ℝ≥0
#align has_nndist NNDist
export NNDist (nndist)
-- see Note [lower instance priority]
/-- Distance as a nonnegative real number. -/
instance (priority := 100) PseudoMetricSpace.toNNDist : NNDist α :=
⟨fun a b => ⟨dist a b, dist_nonneg⟩⟩
#align pseudo_metric_space.to_has_nndist PseudoMetricSpace.toNNDist
/-- Express `dist` in terms of `nndist`-/
theorem dist_nndist (x y : α) : dist x y = nndist x y := rfl
#align dist_nndist dist_nndist
@[simp, norm_cast]
theorem coe_nndist (x y : α) : ↑(nndist x y) = dist x y := rfl
#align coe_nndist coe_nndist
/-- Express `edist` in terms of `nndist`-/
theorem edist_nndist (x y : α) : edist x y = nndist x y := by
rw [edist_dist, dist_nndist, ENNReal.ofReal_coe_nnreal]
#align edist_nndist edist_nndist
/-- Express `nndist` in terms of `edist`-/
theorem nndist_edist (x y : α) : nndist x y = (edist x y).toNNReal := by
simp [edist_nndist]
#align nndist_edist nndist_edist
@[simp, norm_cast]
theorem coe_nnreal_ennreal_nndist (x y : α) : ↑(nndist x y) = edist x y :=
(edist_nndist x y).symm
#align coe_nnreal_ennreal_nndist coe_nnreal_ennreal_nndist
@[simp, norm_cast]
theorem edist_lt_coe {x y : α} {c : ℝ≥0} : edist x y < c ↔ nndist x y < c := by
rw [edist_nndist, ENNReal.coe_lt_coe]
#align edist_lt_coe edist_lt_coe
@[simp, norm_cast]
theorem edist_le_coe {x y : α} {c : ℝ≥0} : edist x y ≤ c ↔ nndist x y ≤ c := by
rw [edist_nndist, ENNReal.coe_le_coe]
#align edist_le_coe edist_le_coe
/-- In a pseudometric space, the extended distance is always finite-/
theorem edist_lt_top {α : Type*} [PseudoMetricSpace α] (x y : α) : edist x y < ⊤ :=
(edist_dist x y).symm ▸ ENNReal.ofReal_lt_top
#align edist_lt_top edist_lt_top
/-- In a pseudometric space, the extended distance is always finite-/
theorem edist_ne_top (x y : α) : edist x y ≠ ⊤ :=
(edist_lt_top x y).ne
#align edist_ne_top edist_ne_top
/-- `nndist x x` vanishes-/
@[simp] theorem nndist_self (a : α) : nndist a a = 0 := NNReal.coe_eq_zero.1 (dist_self a)
#align nndist_self nndist_self
-- Porting note: `dist_nndist` and `coe_nndist` moved up
@[simp, norm_cast]
theorem dist_lt_coe {x y : α} {c : ℝ≥0} : dist x y < c ↔ nndist x y < c :=
Iff.rfl
#align dist_lt_coe dist_lt_coe
@[simp, norm_cast]
theorem dist_le_coe {x y : α} {c : ℝ≥0} : dist x y ≤ c ↔ nndist x y ≤ c :=
Iff.rfl
#align dist_le_coe dist_le_coe
@[simp]
theorem edist_lt_ofReal {x y : α} {r : ℝ} : edist x y < ENNReal.ofReal r ↔ dist x y < r := by
rw [edist_dist, ENNReal.ofReal_lt_ofReal_iff_of_nonneg dist_nonneg]
#align edist_lt_of_real edist_lt_ofReal
@[simp]
theorem edist_le_ofReal {x y : α} {r : ℝ} (hr : 0 ≤ r) :
edist x y ≤ ENNReal.ofReal r ↔ dist x y ≤ r := by
rw [edist_dist, ENNReal.ofReal_le_ofReal_iff hr]
#align edist_le_of_real edist_le_ofReal
/-- Express `nndist` in terms of `dist`-/
theorem nndist_dist (x y : α) : nndist x y = Real.toNNReal (dist x y) := by
rw [dist_nndist, Real.toNNReal_coe]
#align nndist_dist nndist_dist
theorem nndist_comm (x y : α) : nndist x y = nndist y x := NNReal.eq <| dist_comm x y
#align nndist_comm nndist_comm
/-- Triangle inequality for the nonnegative distance-/
theorem nndist_triangle (x y z : α) : nndist x z ≤ nndist x y + nndist y z :=
dist_triangle _ _ _
#align nndist_triangle nndist_triangle
theorem nndist_triangle_left (x y z : α) : nndist x y ≤ nndist z x + nndist z y :=
dist_triangle_left _ _ _
#align nndist_triangle_left nndist_triangle_left
theorem nndist_triangle_right (x y z : α) : nndist x y ≤ nndist x z + nndist y z :=
dist_triangle_right _ _ _
#align nndist_triangle_right nndist_triangle_right
/-- Express `dist` in terms of `edist`-/
theorem dist_edist (x y : α) : dist x y = (edist x y).toReal := by
rw [edist_dist, ENNReal.toReal_ofReal dist_nonneg]
#align dist_edist dist_edist
namespace Metric
-- instantiate pseudometric space as a topology
variable {x y z : α} {δ ε ε₁ ε₂ : ℝ} {s : Set α}
/-- `ball x ε` is the set of all points `y` with `dist y x < ε` -/
def ball (x : α) (ε : ℝ) : Set α :=
{ y | dist y x < ε }
#align metric.ball Metric.ball
@[simp]
theorem mem_ball : y ∈ ball x ε ↔ dist y x < ε :=
Iff.rfl
#align metric.mem_ball Metric.mem_ball
theorem mem_ball' : y ∈ ball x ε ↔ dist x y < ε := by rw [dist_comm, mem_ball]
#align metric.mem_ball' Metric.mem_ball'
theorem pos_of_mem_ball (hy : y ∈ ball x ε) : 0 < ε :=
dist_nonneg.trans_lt hy
#align metric.pos_of_mem_ball Metric.pos_of_mem_ball
theorem mem_ball_self (h : 0 < ε) : x ∈ ball x ε := by
rwa [mem_ball, dist_self]
#align metric.mem_ball_self Metric.mem_ball_self
@[simp]
theorem nonempty_ball : (ball x ε).Nonempty ↔ 0 < ε :=
⟨fun ⟨_x, hx⟩ => pos_of_mem_ball hx, fun h => ⟨x, mem_ball_self h⟩⟩
#align metric.nonempty_ball Metric.nonempty_ball
@[simp]
theorem ball_eq_empty : ball x ε = ∅ ↔ ε ≤ 0 := by
rw [← not_nonempty_iff_eq_empty, nonempty_ball, not_lt]
#align metric.ball_eq_empty Metric.ball_eq_empty
@[simp]
theorem ball_zero : ball x 0 = ∅ := by rw [ball_eq_empty]
#align metric.ball_zero Metric.ball_zero
/-- If a point belongs to an open ball, then there is a strictly smaller radius whose ball also
contains it.
See also `exists_lt_subset_ball`. -/
theorem exists_lt_mem_ball_of_mem_ball (h : x ∈ ball y ε) : ∃ ε' < ε, x ∈ ball y ε' := by
simp only [mem_ball] at h ⊢
exact ⟨(dist x y + ε) / 2, by linarith, by linarith⟩
#align metric.exists_lt_mem_ball_of_mem_ball Metric.exists_lt_mem_ball_of_mem_ball
theorem ball_eq_ball (ε : ℝ) (x : α) :
UniformSpace.ball x { p | dist p.2 p.1 < ε } = Metric.ball x ε :=
rfl
#align metric.ball_eq_ball Metric.ball_eq_ball
theorem ball_eq_ball' (ε : ℝ) (x : α) :
UniformSpace.ball x { p | dist p.1 p.2 < ε } = Metric.ball x ε := by
ext
simp [dist_comm, UniformSpace.ball]
#align metric.ball_eq_ball' Metric.ball_eq_ball'
@[simp]
theorem iUnion_ball_nat (x : α) : ⋃ n : ℕ, ball x n = univ :=
iUnion_eq_univ_iff.2 fun y => exists_nat_gt (dist y x)
#align metric.Union_ball_nat Metric.iUnion_ball_nat
@[simp]
theorem iUnion_ball_nat_succ (x : α) : ⋃ n : ℕ, ball x (n + 1) = univ :=
iUnion_eq_univ_iff.2 fun y => (exists_nat_gt (dist y x)).imp fun _ h => h.trans (lt_add_one _)
#align metric.Union_ball_nat_succ Metric.iUnion_ball_nat_succ
/-- `closedBall x ε` is the set of all points `y` with `dist y x ≤ ε` -/
def closedBall (x : α) (ε : ℝ) :=
{ y | dist y x ≤ ε }
#align metric.closed_ball Metric.closedBall
@[simp] theorem mem_closedBall : y ∈ closedBall x ε ↔ dist y x ≤ ε := Iff.rfl
#align metric.mem_closed_ball Metric.mem_closedBall
theorem mem_closedBall' : y ∈ closedBall x ε ↔ dist x y ≤ ε := by rw [dist_comm, mem_closedBall]
#align metric.mem_closed_ball' Metric.mem_closedBall'
/-- `sphere x ε` is the set of all points `y` with `dist y x = ε` -/
def sphere (x : α) (ε : ℝ) := { y | dist y x = ε }
#align metric.sphere Metric.sphere
@[simp] theorem mem_sphere : y ∈ sphere x ε ↔ dist y x = ε := Iff.rfl
#align metric.mem_sphere Metric.mem_sphere
theorem mem_sphere' : y ∈ sphere x ε ↔ dist x y = ε := by rw [dist_comm, mem_sphere]
#align metric.mem_sphere' Metric.mem_sphere'
theorem ne_of_mem_sphere (h : y ∈ sphere x ε) (hε : ε ≠ 0) : y ≠ x :=
ne_of_mem_of_not_mem h <| by simpa using hε.symm
#align metric.ne_of_mem_sphere Metric.ne_of_mem_sphere
theorem nonneg_of_mem_sphere (hy : y ∈ sphere x ε) : 0 ≤ ε :=
dist_nonneg.trans_eq hy
#align metric.nonneg_of_mem_sphere Metric.nonneg_of_mem_sphere
@[simp]
theorem sphere_eq_empty_of_neg (hε : ε < 0) : sphere x ε = ∅ :=
Set.eq_empty_iff_forall_not_mem.mpr fun _y hy => (nonneg_of_mem_sphere hy).not_lt hε
#align metric.sphere_eq_empty_of_neg Metric.sphere_eq_empty_of_neg
theorem sphere_eq_empty_of_subsingleton [Subsingleton α] (hε : ε ≠ 0) : sphere x ε = ∅ :=
Set.eq_empty_iff_forall_not_mem.mpr fun _ h => ne_of_mem_sphere h hε (Subsingleton.elim _ _)
#align metric.sphere_eq_empty_of_subsingleton Metric.sphere_eq_empty_of_subsingleton
instance sphere_isEmpty_of_subsingleton [Subsingleton α] [NeZero ε] : IsEmpty (sphere x ε) := by
rw [sphere_eq_empty_of_subsingleton (NeZero.ne ε)]; infer_instance
#align metric.sphere_is_empty_of_subsingleton Metric.sphere_isEmpty_of_subsingleton
theorem mem_closedBall_self (h : 0 ≤ ε) : x ∈ closedBall x ε := by
rwa [mem_closedBall, dist_self]
#align metric.mem_closed_ball_self Metric.mem_closedBall_self
@[simp]
theorem nonempty_closedBall : (closedBall x ε).Nonempty ↔ 0 ≤ ε :=
⟨fun ⟨_x, hx⟩ => dist_nonneg.trans hx, fun h => ⟨x, mem_closedBall_self h⟩⟩
#align metric.nonempty_closed_ball Metric.nonempty_closedBall
@[simp]
theorem closedBall_eq_empty : closedBall x ε = ∅ ↔ ε < 0 := by
rw [← not_nonempty_iff_eq_empty, nonempty_closedBall, not_le]
#align metric.closed_ball_eq_empty Metric.closedBall_eq_empty
/-- Closed balls and spheres coincide when the radius is non-positive -/
theorem closedBall_eq_sphere_of_nonpos (hε : ε ≤ 0) : closedBall x ε = sphere x ε :=
Set.ext fun _ => (hε.trans dist_nonneg).le_iff_eq
#align metric.closed_ball_eq_sphere_of_nonpos Metric.closedBall_eq_sphere_of_nonpos
theorem ball_subset_closedBall : ball x ε ⊆ closedBall x ε := fun _y hy =>
mem_closedBall.2 (le_of_lt hy)
#align metric.ball_subset_closed_ball Metric.ball_subset_closedBall
theorem sphere_subset_closedBall : sphere x ε ⊆ closedBall x ε := fun _ => le_of_eq
#align metric.sphere_subset_closed_ball Metric.sphere_subset_closedBall
lemma sphere_subset_ball {r R : ℝ} (h : r < R) : sphere x r ⊆ ball x R := fun _x hx ↦
(mem_sphere.1 hx).trans_lt h
theorem closedBall_disjoint_ball (h : δ + ε ≤ dist x y) : Disjoint (closedBall x δ) (ball y ε) :=
Set.disjoint_left.mpr fun _a ha1 ha2 =>
(h.trans <| dist_triangle_left _ _ _).not_lt <| add_lt_add_of_le_of_lt ha1 ha2
#align metric.closed_ball_disjoint_ball Metric.closedBall_disjoint_ball
theorem ball_disjoint_closedBall (h : δ + ε ≤ dist x y) : Disjoint (ball x δ) (closedBall y ε) :=
(closedBall_disjoint_ball <| by rwa [add_comm, dist_comm]).symm
#align metric.ball_disjoint_closed_ball Metric.ball_disjoint_closedBall
theorem ball_disjoint_ball (h : δ + ε ≤ dist x y) : Disjoint (ball x δ) (ball y ε) :=
(closedBall_disjoint_ball h).mono_left ball_subset_closedBall
#align metric.ball_disjoint_ball Metric.ball_disjoint_ball
theorem closedBall_disjoint_closedBall (h : δ + ε < dist x y) :
Disjoint (closedBall x δ) (closedBall y ε) :=
Set.disjoint_left.mpr fun _a ha1 ha2 =>
h.not_le <| (dist_triangle_left _ _ _).trans <| add_le_add ha1 ha2
#align metric.closed_ball_disjoint_closed_ball Metric.closedBall_disjoint_closedBall
theorem sphere_disjoint_ball : Disjoint (sphere x ε) (ball x ε) :=
Set.disjoint_left.mpr fun _y hy₁ hy₂ => absurd hy₁ <| ne_of_lt hy₂
#align metric.sphere_disjoint_ball Metric.sphere_disjoint_ball
@[simp]
theorem ball_union_sphere : ball x ε ∪ sphere x ε = closedBall x ε :=
Set.ext fun _y => (@le_iff_lt_or_eq ℝ _ _ _).symm
#align metric.ball_union_sphere Metric.ball_union_sphere
@[simp]
theorem sphere_union_ball : sphere x ε ∪ ball x ε = closedBall x ε := by
rw [union_comm, ball_union_sphere]
#align metric.sphere_union_ball Metric.sphere_union_ball
@[simp]
theorem closedBall_diff_sphere : closedBall x ε \ sphere x ε = ball x ε := by
rw [← ball_union_sphere, Set.union_diff_cancel_right sphere_disjoint_ball.symm.le_bot]
#align metric.closed_ball_diff_sphere Metric.closedBall_diff_sphere
@[simp]
theorem closedBall_diff_ball : closedBall x ε \ ball x ε = sphere x ε := by
rw [← ball_union_sphere, Set.union_diff_cancel_left sphere_disjoint_ball.symm.le_bot]
#align metric.closed_ball_diff_ball Metric.closedBall_diff_ball
theorem mem_ball_comm : x ∈ ball y ε ↔ y ∈ ball x ε := by rw [mem_ball', mem_ball]
#align metric.mem_ball_comm Metric.mem_ball_comm
theorem mem_closedBall_comm : x ∈ closedBall y ε ↔ y ∈ closedBall x ε := by
rw [mem_closedBall', mem_closedBall]
#align metric.mem_closed_ball_comm Metric.mem_closedBall_comm
theorem mem_sphere_comm : x ∈ sphere y ε ↔ y ∈ sphere x ε := by rw [mem_sphere', mem_sphere]
#align metric.mem_sphere_comm Metric.mem_sphere_comm
@[gcongr]
theorem ball_subset_ball (h : ε₁ ≤ ε₂) : ball x ε₁ ⊆ ball x ε₂ := fun _y yx =>
lt_of_lt_of_le (mem_ball.1 yx) h
#align metric.ball_subset_ball Metric.ball_subset_ball
theorem closedBall_eq_bInter_ball : closedBall x ε = ⋂ δ > ε, ball x δ := by
ext y; rw [mem_closedBall, ← forall_lt_iff_le', mem_iInter₂]; rfl
#align metric.closed_ball_eq_bInter_ball Metric.closedBall_eq_bInter_ball
theorem ball_subset_ball' (h : ε₁ + dist x y ≤ ε₂) : ball x ε₁ ⊆ ball y ε₂ := fun z hz =>
calc
dist z y ≤ dist z x + dist x y := dist_triangle _ _ _
_ < ε₁ + dist x y := add_lt_add_right (mem_ball.1 hz) _
_ ≤ ε₂ := h
#align metric.ball_subset_ball' Metric.ball_subset_ball'
@[gcongr]
theorem closedBall_subset_closedBall (h : ε₁ ≤ ε₂) : closedBall x ε₁ ⊆ closedBall x ε₂ :=
fun _y (yx : _ ≤ ε₁) => le_trans yx h
#align metric.closed_ball_subset_closed_ball Metric.closedBall_subset_closedBall
theorem closedBall_subset_closedBall' (h : ε₁ + dist x y ≤ ε₂) :
closedBall x ε₁ ⊆ closedBall y ε₂ := fun z hz =>
calc
dist z y ≤ dist z x + dist x y := dist_triangle _ _ _
_ ≤ ε₁ + dist x y := add_le_add_right (mem_closedBall.1 hz) _
_ ≤ ε₂ := h
#align metric.closed_ball_subset_closed_ball' Metric.closedBall_subset_closedBall'
theorem closedBall_subset_ball (h : ε₁ < ε₂) : closedBall x ε₁ ⊆ ball x ε₂ :=
fun y (yh : dist y x ≤ ε₁) => lt_of_le_of_lt yh h
#align metric.closed_ball_subset_ball Metric.closedBall_subset_ball
theorem closedBall_subset_ball' (h : ε₁ + dist x y < ε₂) :
closedBall x ε₁ ⊆ ball y ε₂ := fun z hz =>
calc
dist z y ≤ dist z x + dist x y := dist_triangle _ _ _
_ ≤ ε₁ + dist x y := add_le_add_right (mem_closedBall.1 hz) _
_ < ε₂ := h
#align metric.closed_ball_subset_ball' Metric.closedBall_subset_ball'
theorem dist_le_add_of_nonempty_closedBall_inter_closedBall
(h : (closedBall x ε₁ ∩ closedBall y ε₂).Nonempty) : dist x y ≤ ε₁ + ε₂ :=
let ⟨z, hz⟩ := h
calc
dist x y ≤ dist z x + dist z y := dist_triangle_left _ _ _
_ ≤ ε₁ + ε₂ := add_le_add hz.1 hz.2
#align metric.dist_le_add_of_nonempty_closed_ball_inter_closed_ball Metric.dist_le_add_of_nonempty_closedBall_inter_closedBall
theorem dist_lt_add_of_nonempty_closedBall_inter_ball (h : (closedBall x ε₁ ∩ ball y ε₂).Nonempty) :
dist x y < ε₁ + ε₂ :=
let ⟨z, hz⟩ := h
calc
dist x y ≤ dist z x + dist z y := dist_triangle_left _ _ _
_ < ε₁ + ε₂ := add_lt_add_of_le_of_lt hz.1 hz.2
#align metric.dist_lt_add_of_nonempty_closed_ball_inter_ball Metric.dist_lt_add_of_nonempty_closedBall_inter_ball
theorem dist_lt_add_of_nonempty_ball_inter_closedBall (h : (ball x ε₁ ∩ closedBall y ε₂).Nonempty) :
dist x y < ε₁ + ε₂ := by
rw [inter_comm] at h
rw [add_comm, dist_comm]
exact dist_lt_add_of_nonempty_closedBall_inter_ball h
#align metric.dist_lt_add_of_nonempty_ball_inter_closed_ball Metric.dist_lt_add_of_nonempty_ball_inter_closedBall
theorem dist_lt_add_of_nonempty_ball_inter_ball (h : (ball x ε₁ ∩ ball y ε₂).Nonempty) :
dist x y < ε₁ + ε₂ :=
dist_lt_add_of_nonempty_closedBall_inter_ball <|
h.mono (inter_subset_inter ball_subset_closedBall Subset.rfl)
#align metric.dist_lt_add_of_nonempty_ball_inter_ball Metric.dist_lt_add_of_nonempty_ball_inter_ball
@[simp]
theorem iUnion_closedBall_nat (x : α) : ⋃ n : ℕ, closedBall x n = univ :=
iUnion_eq_univ_iff.2 fun y => exists_nat_ge (dist y x)
#align metric.Union_closed_ball_nat Metric.iUnion_closedBall_nat
theorem iUnion_inter_closedBall_nat (s : Set α) (x : α) : ⋃ n : ℕ, s ∩ closedBall x n = s := by
rw [← inter_iUnion, iUnion_closedBall_nat, inter_univ]
#align metric.Union_inter_closed_ball_nat Metric.iUnion_inter_closedBall_nat
theorem ball_subset (h : dist x y ≤ ε₂ - ε₁) : ball x ε₁ ⊆ ball y ε₂ := fun z zx => by
rw [← add_sub_cancel ε₁ ε₂]
exact lt_of_le_of_lt (dist_triangle z x y) (add_lt_add_of_lt_of_le zx h)
#align metric.ball_subset Metric.ball_subset
theorem ball_half_subset (y) (h : y ∈ ball x (ε / 2)) : ball y (ε / 2) ⊆ ball x ε :=
ball_subset <| by rw [sub_self_div_two]; exact le_of_lt h
#align metric.ball_half_subset Metric.ball_half_subset
theorem exists_ball_subset_ball (h : y ∈ ball x ε) : ∃ ε' > 0, ball y ε' ⊆ ball x ε :=
⟨_, sub_pos.2 h, ball_subset <| by rw [sub_sub_self]⟩
#align metric.exists_ball_subset_ball Metric.exists_ball_subset_ball
/-- If a property holds for all points in closed balls of arbitrarily large radii, then it holds for
all points. -/
theorem forall_of_forall_mem_closedBall (p : α → Prop) (x : α)
(H : ∃ᶠ R : ℝ in atTop, ∀ y ∈ closedBall x R, p y) (y : α) : p y := by
obtain ⟨R, hR, h⟩ : ∃ R ≥ dist y x, ∀ z : α, z ∈ closedBall x R → p z :=
frequently_iff.1 H (Ici_mem_atTop (dist y x))
exact h _ hR
#align metric.forall_of_forall_mem_closed_ball Metric.forall_of_forall_mem_closedBall
/-- If a property holds for all points in balls of arbitrarily large radii, then it holds for all
points. -/
theorem forall_of_forall_mem_ball (p : α → Prop) (x : α)
(H : ∃ᶠ R : ℝ in atTop, ∀ y ∈ ball x R, p y) (y : α) : p y := by
obtain ⟨R, hR, h⟩ : ∃ R > dist y x, ∀ z : α, z ∈ ball x R → p z :=
frequently_iff.1 H (Ioi_mem_atTop (dist y x))
exact h _ hR
#align metric.forall_of_forall_mem_ball Metric.forall_of_forall_mem_ball
theorem isBounded_iff {s : Set α} :
IsBounded s ↔ ∃ C : ℝ, ∀ ⦃x⦄, x ∈ s → ∀ ⦃y⦄, y ∈ s → dist x y ≤ C := by
rw [isBounded_def, ← Filter.mem_sets, @PseudoMetricSpace.cobounded_sets α, mem_setOf_eq,
compl_compl]
#align metric.is_bounded_iff Metric.isBounded_iff
theorem isBounded_iff_eventually {s : Set α} :
IsBounded s ↔ ∀ᶠ C in atTop, ∀ ⦃x⦄, x ∈ s → ∀ ⦃y⦄, y ∈ s → dist x y ≤ C :=
isBounded_iff.trans
⟨fun ⟨C, h⟩ => eventually_atTop.2 ⟨C, fun _C' hC' _x hx _y hy => (h hx hy).trans hC'⟩,
Eventually.exists⟩
#align metric.is_bounded_iff_eventually Metric.isBounded_iff_eventually
theorem isBounded_iff_exists_ge {s : Set α} (c : ℝ) :
IsBounded s ↔ ∃ C, c ≤ C ∧ ∀ ⦃x⦄, x ∈ s → ∀ ⦃y⦄, y ∈ s → dist x y ≤ C :=
⟨fun h => ((eventually_ge_atTop c).and (isBounded_iff_eventually.1 h)).exists, fun h =>
isBounded_iff.2 <| h.imp fun _ => And.right⟩
#align metric.is_bounded_iff_exists_ge Metric.isBounded_iff_exists_ge
theorem isBounded_iff_nndist {s : Set α} :
IsBounded s ↔ ∃ C : ℝ≥0, ∀ ⦃x⦄, x ∈ s → ∀ ⦃y⦄, y ∈ s → nndist x y ≤ C := by
simp only [isBounded_iff_exists_ge 0, NNReal.exists, ← NNReal.coe_le_coe, ← dist_nndist,
NNReal.coe_mk, exists_prop]
#align metric.is_bounded_iff_nndist Metric.isBounded_iff_nndist
theorem toUniformSpace_eq :
‹PseudoMetricSpace α›.toUniformSpace = .ofDist dist dist_self dist_comm dist_triangle :=
UniformSpace.ext PseudoMetricSpace.uniformity_dist
#align metric.to_uniform_space_eq Metric.toUniformSpace_eq
theorem uniformity_basis_dist :
(𝓤 α).HasBasis (fun ε : ℝ => 0 < ε) fun ε => { p : α × α | dist p.1 p.2 < ε } := by
rw [toUniformSpace_eq]
exact UniformSpace.hasBasis_ofFun (exists_gt _) _ _ _ _ _
#align metric.uniformity_basis_dist Metric.uniformity_basis_dist
/-- Given `f : β → ℝ`, if `f` sends `{i | p i}` to a set of positive numbers
accumulating to zero, then `f i`-neighborhoods of the diagonal form a basis of `𝓤 α`.
For specific bases see `uniformity_basis_dist`, `uniformity_basis_dist_inv_nat_succ`,
and `uniformity_basis_dist_inv_nat_pos`. -/
protected theorem mk_uniformity_basis {β : Type*} {p : β → Prop} {f : β → ℝ}
(hf₀ : ∀ i, p i → 0 < f i) (hf : ∀ ⦃ε⦄, 0 < ε → ∃ i, p i ∧ f i ≤ ε) :
(𝓤 α).HasBasis p fun i => { p : α × α | dist p.1 p.2 < f i } := by
refine ⟨fun s => uniformity_basis_dist.mem_iff.trans ?_⟩
constructor
· rintro ⟨ε, ε₀, hε⟩
rcases hf ε₀ with ⟨i, hi, H⟩
exact ⟨i, hi, fun x (hx : _ < _) => hε <| lt_of_lt_of_le hx H⟩
· exact fun ⟨i, hi, H⟩ => ⟨f i, hf₀ i hi, H⟩
#align metric.mk_uniformity_basis Metric.mk_uniformity_basis
theorem uniformity_basis_dist_rat :
(𝓤 α).HasBasis (fun r : ℚ => 0 < r) fun r => { p : α × α | dist p.1 p.2 < r } :=
Metric.mk_uniformity_basis (fun _ => Rat.cast_pos.2) fun _ε hε =>
let ⟨r, hr0, hrε⟩ := exists_rat_btwn hε
⟨r, Rat.cast_pos.1 hr0, hrε.le⟩
#align metric.uniformity_basis_dist_rat Metric.uniformity_basis_dist_rat
theorem uniformity_basis_dist_inv_nat_succ :
(𝓤 α).HasBasis (fun _ => True) fun n : ℕ => { p : α × α | dist p.1 p.2 < 1 / (↑n + 1) } :=
Metric.mk_uniformity_basis (fun n _ => div_pos zero_lt_one <| Nat.cast_add_one_pos n) fun _ε ε0 =>
(exists_nat_one_div_lt ε0).imp fun _n hn => ⟨trivial, le_of_lt hn⟩
#align metric.uniformity_basis_dist_inv_nat_succ Metric.uniformity_basis_dist_inv_nat_succ
theorem uniformity_basis_dist_inv_nat_pos :
(𝓤 α).HasBasis (fun n : ℕ => 0 < n) fun n : ℕ => { p : α × α | dist p.1 p.2 < 1 / ↑n } :=
Metric.mk_uniformity_basis (fun _ hn => div_pos zero_lt_one <| Nat.cast_pos.2 hn) fun _ ε0 =>
let ⟨n, hn⟩ := exists_nat_one_div_lt ε0
⟨n + 1, Nat.succ_pos n, mod_cast hn.le⟩
#align metric.uniformity_basis_dist_inv_nat_pos Metric.uniformity_basis_dist_inv_nat_pos
theorem uniformity_basis_dist_pow {r : ℝ} (h0 : 0 < r) (h1 : r < 1) :
(𝓤 α).HasBasis (fun _ : ℕ => True) fun n : ℕ => { p : α × α | dist p.1 p.2 < r ^ n } :=
Metric.mk_uniformity_basis (fun _ _ => pow_pos h0 _) fun _ε ε0 =>
let ⟨n, hn⟩ := exists_pow_lt_of_lt_one ε0 h1
⟨n, trivial, hn.le⟩
#align metric.uniformity_basis_dist_pow Metric.uniformity_basis_dist_pow
theorem uniformity_basis_dist_lt {R : ℝ} (hR : 0 < R) :
(𝓤 α).HasBasis (fun r : ℝ => 0 < r ∧ r < R) fun r => { p : α × α | dist p.1 p.2 < r } :=
Metric.mk_uniformity_basis (fun _ => And.left) fun r hr =>
⟨min r (R / 2), ⟨lt_min hr (half_pos hR), min_lt_iff.2 <| Or.inr (half_lt_self hR)⟩,
min_le_left _ _⟩
#align metric.uniformity_basis_dist_lt Metric.uniformity_basis_dist_lt
/-- Given `f : β → ℝ`, if `f` sends `{i | p i}` to a set of positive numbers
accumulating to zero, then closed neighborhoods of the diagonal of sizes `{f i | p i}`
form a basis of `𝓤 α`.
Currently we have only one specific basis `uniformity_basis_dist_le` based on this constructor.
More can be easily added if needed in the future. -/
protected theorem mk_uniformity_basis_le {β : Type*} {p : β → Prop} {f : β → ℝ}
(hf₀ : ∀ x, p x → 0 < f x) (hf : ∀ ε, 0 < ε → ∃ x, p x ∧ f x ≤ ε) :
(𝓤 α).HasBasis p fun x => { p : α × α | dist p.1 p.2 ≤ f x } := by
refine ⟨fun s => uniformity_basis_dist.mem_iff.trans ?_⟩
constructor
· rintro ⟨ε, ε₀, hε⟩
rcases exists_between ε₀ with ⟨ε', hε'⟩
rcases hf ε' hε'.1 with ⟨i, hi, H⟩
exact ⟨i, hi, fun x (hx : _ ≤ _) => hε <| lt_of_le_of_lt (le_trans hx H) hε'.2⟩
· exact fun ⟨i, hi, H⟩ => ⟨f i, hf₀ i hi, fun x (hx : _ < _) => H (mem_setOf.2 hx.le)⟩
#align metric.mk_uniformity_basis_le Metric.mk_uniformity_basis_le
/-- Constant size closed neighborhoods of the diagonal form a basis
of the uniformity filter. -/
theorem uniformity_basis_dist_le :
(𝓤 α).HasBasis ((0 : ℝ) < ·) fun ε => { p : α × α | dist p.1 p.2 ≤ ε } :=
Metric.mk_uniformity_basis_le (fun _ => id) fun ε ε₀ => ⟨ε, ε₀, le_refl ε⟩
#align metric.uniformity_basis_dist_le Metric.uniformity_basis_dist_le
theorem uniformity_basis_dist_le_pow {r : ℝ} (h0 : 0 < r) (h1 : r < 1) :
(𝓤 α).HasBasis (fun _ : ℕ => True) fun n : ℕ => { p : α × α | dist p.1 p.2 ≤ r ^ n } :=
Metric.mk_uniformity_basis_le (fun _ _ => pow_pos h0 _) fun _ε ε0 =>
let ⟨n, hn⟩ := exists_pow_lt_of_lt_one ε0 h1
⟨n, trivial, hn.le⟩
#align metric.uniformity_basis_dist_le_pow Metric.uniformity_basis_dist_le_pow
theorem mem_uniformity_dist {s : Set (α × α)} :
s ∈ 𝓤 α ↔ ∃ ε > 0, ∀ {a b : α}, dist a b < ε → (a, b) ∈ s :=
uniformity_basis_dist.mem_uniformity_iff
#align metric.mem_uniformity_dist Metric.mem_uniformity_dist
/-- A constant size neighborhood of the diagonal is an entourage. -/
theorem dist_mem_uniformity {ε : ℝ} (ε0 : 0 < ε) : { p : α × α | dist p.1 p.2 < ε } ∈ 𝓤 α :=
mem_uniformity_dist.2 ⟨ε, ε0, id⟩
#align metric.dist_mem_uniformity Metric.dist_mem_uniformity
theorem uniformContinuous_iff [PseudoMetricSpace β] {f : α → β} :
UniformContinuous f ↔ ∀ ε > 0, ∃ δ > 0, ∀ {a b : α}, dist a b < δ → dist (f a) (f b) < ε :=
uniformity_basis_dist.uniformContinuous_iff uniformity_basis_dist
#align metric.uniform_continuous_iff Metric.uniformContinuous_iff
theorem uniformContinuousOn_iff [PseudoMetricSpace β] {f : α → β} {s : Set α} :
UniformContinuousOn f s ↔
∀ ε > 0, ∃ δ > 0, ∀ x ∈ s, ∀ y ∈ s, dist x y < δ → dist (f x) (f y) < ε :=
Metric.uniformity_basis_dist.uniformContinuousOn_iff Metric.uniformity_basis_dist
#align metric.uniform_continuous_on_iff Metric.uniformContinuousOn_iff
theorem uniformContinuousOn_iff_le [PseudoMetricSpace β] {f : α → β} {s : Set α} :
UniformContinuousOn f s ↔
∀ ε > 0, ∃ δ > 0, ∀ x ∈ s, ∀ y ∈ s, dist x y ≤ δ → dist (f x) (f y) ≤ ε :=
Metric.uniformity_basis_dist_le.uniformContinuousOn_iff Metric.uniformity_basis_dist_le
#align metric.uniform_continuous_on_iff_le Metric.uniformContinuousOn_iff_le
nonrec theorem uniformInducing_iff [PseudoMetricSpace β] {f : α → β} :
UniformInducing f ↔ UniformContinuous f ∧
∀ δ > 0, ∃ ε > 0, ∀ {a b : α}, dist (f a) (f b) < ε → dist a b < δ :=
uniformInducing_iff'.trans <| Iff.rfl.and <|
((uniformity_basis_dist.comap _).le_basis_iff uniformity_basis_dist).trans <| by
simp only [subset_def, Prod.forall, gt_iff_lt, preimage_setOf_eq, Prod.map_apply, mem_setOf]
nonrec theorem uniformEmbedding_iff [PseudoMetricSpace β] {f : α → β} :
UniformEmbedding f ↔ Function.Injective f ∧ UniformContinuous f ∧
∀ δ > 0, ∃ ε > 0, ∀ {a b : α}, dist (f a) (f b) < ε → dist a b < δ := by
rw [uniformEmbedding_iff, and_comm, uniformInducing_iff]
#align metric.uniform_embedding_iff Metric.uniformEmbedding_iff
/-- If a map between pseudometric spaces is a uniform embedding then the distance between `f x`
and `f y` is controlled in terms of the distance between `x` and `y`. -/
theorem controlled_of_uniformEmbedding [PseudoMetricSpace β] {f : α → β} (h : UniformEmbedding f) :
(∀ ε > 0, ∃ δ > 0, ∀ {a b : α}, dist a b < δ → dist (f a) (f b) < ε) ∧
∀ δ > 0, ∃ ε > 0, ∀ {a b : α}, dist (f a) (f b) < ε → dist a b < δ :=
⟨uniformContinuous_iff.1 h.uniformContinuous, (uniformEmbedding_iff.1 h).2.2⟩
#align metric.controlled_of_uniform_embedding Metric.controlled_of_uniformEmbedding
theorem totallyBounded_iff {s : Set α} :
TotallyBounded s ↔ ∀ ε > 0, ∃ t : Set α, t.Finite ∧ s ⊆ ⋃ y ∈ t, ball y ε :=
uniformity_basis_dist.totallyBounded_iff
#align metric.totally_bounded_iff Metric.totallyBounded_iff
/-- A pseudometric space is totally bounded if one can reconstruct up to any ε>0 any element of the
space from finitely many data. -/
theorem totallyBounded_of_finite_discretization {s : Set α}
(H : ∀ ε > (0 : ℝ),
∃ (β : Type u) (_ : Fintype β) (F : s → β), ∀ x y, F x = F y → dist (x : α) y < ε) :
TotallyBounded s := by
rcases s.eq_empty_or_nonempty with hs | hs
· rw [hs]
exact totallyBounded_empty
rcases hs with ⟨x0, hx0⟩
haveI : Inhabited s := ⟨⟨x0, hx0⟩⟩
refine totallyBounded_iff.2 fun ε ε0 => ?_
rcases H ε ε0 with ⟨β, fβ, F, hF⟩
let Finv := Function.invFun F
refine ⟨range (Subtype.val ∘ Finv), finite_range _, fun x xs => ?_⟩
let x' := Finv (F ⟨x, xs⟩)
have : F x' = F ⟨x, xs⟩ := Function.invFun_eq ⟨⟨x, xs⟩, rfl⟩
simp only [Set.mem_iUnion, Set.mem_range]
exact ⟨_, ⟨F ⟨x, xs⟩, rfl⟩, hF _ _ this.symm⟩
#align metric.totally_bounded_of_finite_discretization Metric.totallyBounded_of_finite_discretization
theorem finite_approx_of_totallyBounded {s : Set α} (hs : TotallyBounded s) :
∀ ε > 0, ∃ t, t ⊆ s ∧ Set.Finite t ∧ s ⊆ ⋃ y ∈ t, ball y ε := by
intro ε ε_pos
rw [totallyBounded_iff_subset] at hs
exact hs _ (dist_mem_uniformity ε_pos)
#align metric.finite_approx_of_totally_bounded Metric.finite_approx_of_totallyBounded
/-- Expressing uniform convergence using `dist` -/
theorem tendstoUniformlyOnFilter_iff {F : ι → β → α} {f : β → α} {p : Filter ι} {p' : Filter β} :
TendstoUniformlyOnFilter F f p p' ↔
∀ ε > 0, ∀ᶠ n : ι × β in p ×ˢ p', dist (f n.snd) (F n.fst n.snd) < ε := by
refine ⟨fun H ε hε => H _ (dist_mem_uniformity hε), fun H u hu => ?_⟩
rcases mem_uniformity_dist.1 hu with ⟨ε, εpos, hε⟩
exact (H ε εpos).mono fun n hn => hε hn
#align metric.tendsto_uniformly_on_filter_iff Metric.tendstoUniformlyOnFilter_iff
/-- Expressing locally uniform convergence on a set using `dist`. -/
| Mathlib/Topology/MetricSpace/PseudoMetric.lean | 909 | 916 | theorem tendstoLocallyUniformlyOn_iff [TopologicalSpace β] {F : ι → β → α} {f : β → α}
{p : Filter ι} {s : Set β} :
TendstoLocallyUniformlyOn F f p s ↔
∀ ε > 0, ∀ x ∈ s, ∃ t ∈ 𝓝[s] x, ∀ᶠ n in p, ∀ y ∈ t, dist (f y) (F n y) < ε := by |
refine ⟨fun H ε hε => H _ (dist_mem_uniformity hε), fun H u hu x hx => ?_⟩
rcases mem_uniformity_dist.1 hu with ⟨ε, εpos, hε⟩
rcases H ε εpos x hx with ⟨t, ht, Ht⟩
exact ⟨t, ht, Ht.mono fun n hs x hx => hε (hs x hx)⟩
|
/-
Copyright (c) 2021 Rémy Degenne. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Zhouhang Zhou, Yury Kudryashov, Sébastien Gouëzel, Rémy Degenne
-/
import Mathlib.MeasureTheory.Function.SimpleFuncDenseLp
#align_import measure_theory.integral.set_to_l1 from "leanprover-community/mathlib"@"f2ce6086713c78a7f880485f7917ea547a215982"
/-!
# Extension of a linear function from indicators to L1
Let `T : Set α → E →L[ℝ] F` be additive for measurable sets with finite measure, in the sense that
for `s, t` two such sets, `s ∩ t = ∅ → T (s ∪ t) = T s + T t`. `T` is akin to a bilinear map on
`Set α × E`, or a linear map on indicator functions.
This file constructs an extension of `T` to integrable simple functions, which are finite sums of
indicators of measurable sets with finite measure, then to integrable functions, which are limits of
integrable simple functions.
The main result is a continuous linear map `(α →₁[μ] E) →L[ℝ] F`. This extension process is used to
define the Bochner integral in the `MeasureTheory.Integral.Bochner` file and the conditional
expectation of an integrable function in `MeasureTheory.Function.ConditionalExpectation`.
## Main Definitions
- `FinMeasAdditive μ T`: the property that `T` is additive on measurable sets with finite measure.
For two such sets, `s ∩ t = ∅ → T (s ∪ t) = T s + T t`.
- `DominatedFinMeasAdditive μ T C`: `FinMeasAdditive μ T ∧ ∀ s, ‖T s‖ ≤ C * (μ s).toReal`.
This is the property needed to perform the extension from indicators to L1.
- `setToL1 (hT : DominatedFinMeasAdditive μ T C) : (α →₁[μ] E) →L[ℝ] F`: the extension of `T`
from indicators to L1.
- `setToFun μ T (hT : DominatedFinMeasAdditive μ T C) (f : α → E) : F`: a version of the
extension which applies to functions (with value 0 if the function is not integrable).
## Properties
For most properties of `setToFun`, we provide two lemmas. One version uses hypotheses valid on
all sets, like `T = T'`, and a second version which uses a primed name uses hypotheses on
measurable sets with finite measure, like `∀ s, MeasurableSet s → μ s < ∞ → T s = T' s`.
The lemmas listed here don't show all hypotheses. Refer to the actual lemmas for details.
Linearity:
- `setToFun_zero_left : setToFun μ 0 hT f = 0`
- `setToFun_add_left : setToFun μ (T + T') _ f = setToFun μ T hT f + setToFun μ T' hT' f`
- `setToFun_smul_left : setToFun μ (fun s ↦ c • (T s)) (hT.smul c) f = c • setToFun μ T hT f`
- `setToFun_zero : setToFun μ T hT (0 : α → E) = 0`
- `setToFun_neg : setToFun μ T hT (-f) = - setToFun μ T hT f`
If `f` and `g` are integrable:
- `setToFun_add : setToFun μ T hT (f + g) = setToFun μ T hT f + setToFun μ T hT g`
- `setToFun_sub : setToFun μ T hT (f - g) = setToFun μ T hT f - setToFun μ T hT g`
If `T` is verifies `∀ c : 𝕜, ∀ s x, T s (c • x) = c • T s x`:
- `setToFun_smul : setToFun μ T hT (c • f) = c • setToFun μ T hT f`
Other:
- `setToFun_congr_ae (h : f =ᵐ[μ] g) : setToFun μ T hT f = setToFun μ T hT g`
- `setToFun_measure_zero (h : μ = 0) : setToFun μ T hT f = 0`
If the space is a `NormedLatticeAddCommGroup` and `T` is such that `0 ≤ T s x` for `0 ≤ x`, we
also prove order-related properties:
- `setToFun_mono_left (h : ∀ s x, T s x ≤ T' s x) : setToFun μ T hT f ≤ setToFun μ T' hT' f`
- `setToFun_nonneg (hf : 0 ≤ᵐ[μ] f) : 0 ≤ setToFun μ T hT f`
- `setToFun_mono (hfg : f ≤ᵐ[μ] g) : setToFun μ T hT f ≤ setToFun μ T hT g`
## Implementation notes
The starting object `T : Set α → E →L[ℝ] F` matters only through its restriction on measurable sets
with finite measure. Its value on other sets is ignored.
-/
noncomputable section
open scoped Classical Topology NNReal ENNReal MeasureTheory Pointwise
open Set Filter TopologicalSpace ENNReal EMetric
namespace MeasureTheory
variable {α E F F' G 𝕜 : Type*} {p : ℝ≥0∞} [NormedAddCommGroup E] [NormedSpace ℝ E]
[NormedAddCommGroup F] [NormedSpace ℝ F] [NormedAddCommGroup F'] [NormedSpace ℝ F']
[NormedAddCommGroup G] {m : MeasurableSpace α} {μ : Measure α}
local infixr:25 " →ₛ " => SimpleFunc
open Finset
section FinMeasAdditive
/-- A set function is `FinMeasAdditive` if its value on the union of two disjoint measurable
sets with finite measure is the sum of its values on each set. -/
def FinMeasAdditive {β} [AddMonoid β] {_ : MeasurableSpace α} (μ : Measure α) (T : Set α → β) :
Prop :=
∀ s t, MeasurableSet s → MeasurableSet t → μ s ≠ ∞ → μ t ≠ ∞ → s ∩ t = ∅ → T (s ∪ t) = T s + T t
#align measure_theory.fin_meas_additive MeasureTheory.FinMeasAdditive
namespace FinMeasAdditive
variable {β : Type*} [AddCommMonoid β] {T T' : Set α → β}
theorem zero : FinMeasAdditive μ (0 : Set α → β) := fun s t _ _ _ _ _ => by simp
#align measure_theory.fin_meas_additive.zero MeasureTheory.FinMeasAdditive.zero
theorem add (hT : FinMeasAdditive μ T) (hT' : FinMeasAdditive μ T') :
FinMeasAdditive μ (T + T') := by
intro s t hs ht hμs hμt hst
simp only [hT s t hs ht hμs hμt hst, hT' s t hs ht hμs hμt hst, Pi.add_apply]
abel
#align measure_theory.fin_meas_additive.add MeasureTheory.FinMeasAdditive.add
theorem smul [Monoid 𝕜] [DistribMulAction 𝕜 β] (hT : FinMeasAdditive μ T) (c : 𝕜) :
FinMeasAdditive μ fun s => c • T s := fun s t hs ht hμs hμt hst => by
simp [hT s t hs ht hμs hμt hst]
#align measure_theory.fin_meas_additive.smul MeasureTheory.FinMeasAdditive.smul
theorem of_eq_top_imp_eq_top {μ' : Measure α} (h : ∀ s, MeasurableSet s → μ s = ∞ → μ' s = ∞)
(hT : FinMeasAdditive μ T) : FinMeasAdditive μ' T := fun s t hs ht hμ's hμ't hst =>
hT s t hs ht (mt (h s hs) hμ's) (mt (h t ht) hμ't) hst
#align measure_theory.fin_meas_additive.of_eq_top_imp_eq_top MeasureTheory.FinMeasAdditive.of_eq_top_imp_eq_top
theorem of_smul_measure (c : ℝ≥0∞) (hc_ne_top : c ≠ ∞) (hT : FinMeasAdditive (c • μ) T) :
FinMeasAdditive μ T := by
refine of_eq_top_imp_eq_top (fun s _ hμs => ?_) hT
rw [Measure.smul_apply, smul_eq_mul, ENNReal.mul_eq_top] at hμs
simp only [hc_ne_top, or_false_iff, Ne, false_and_iff] at hμs
exact hμs.2
#align measure_theory.fin_meas_additive.of_smul_measure MeasureTheory.FinMeasAdditive.of_smul_measure
theorem smul_measure (c : ℝ≥0∞) (hc_ne_zero : c ≠ 0) (hT : FinMeasAdditive μ T) :
FinMeasAdditive (c • μ) T := by
refine of_eq_top_imp_eq_top (fun s _ hμs => ?_) hT
rw [Measure.smul_apply, smul_eq_mul, ENNReal.mul_eq_top]
simp only [hc_ne_zero, true_and_iff, Ne, not_false_iff]
exact Or.inl hμs
#align measure_theory.fin_meas_additive.smul_measure MeasureTheory.FinMeasAdditive.smul_measure
theorem smul_measure_iff (c : ℝ≥0∞) (hc_ne_zero : c ≠ 0) (hc_ne_top : c ≠ ∞) :
FinMeasAdditive (c • μ) T ↔ FinMeasAdditive μ T :=
⟨fun hT => of_smul_measure c hc_ne_top hT, fun hT => smul_measure c hc_ne_zero hT⟩
#align measure_theory.fin_meas_additive.smul_measure_iff MeasureTheory.FinMeasAdditive.smul_measure_iff
theorem map_empty_eq_zero {β} [AddCancelMonoid β] {T : Set α → β} (hT : FinMeasAdditive μ T) :
T ∅ = 0 := by
have h_empty : μ ∅ ≠ ∞ := (measure_empty.le.trans_lt ENNReal.coe_lt_top).ne
specialize hT ∅ ∅ MeasurableSet.empty MeasurableSet.empty h_empty h_empty (Set.inter_empty ∅)
rw [Set.union_empty] at hT
nth_rw 1 [← add_zero (T ∅)] at hT
exact (add_left_cancel hT).symm
#align measure_theory.fin_meas_additive.map_empty_eq_zero MeasureTheory.FinMeasAdditive.map_empty_eq_zero
theorem map_iUnion_fin_meas_set_eq_sum (T : Set α → β) (T_empty : T ∅ = 0)
(h_add : FinMeasAdditive μ T) {ι} (S : ι → Set α) (sι : Finset ι)
(hS_meas : ∀ i, MeasurableSet (S i)) (hSp : ∀ i ∈ sι, μ (S i) ≠ ∞)
(h_disj : ∀ᵉ (i ∈ sι) (j ∈ sι), i ≠ j → Disjoint (S i) (S j)) :
T (⋃ i ∈ sι, S i) = ∑ i ∈ sι, T (S i) := by
revert hSp h_disj
refine Finset.induction_on sι ?_ ?_
· simp only [Finset.not_mem_empty, IsEmpty.forall_iff, iUnion_false, iUnion_empty, sum_empty,
forall₂_true_iff, imp_true_iff, forall_true_left, not_false_iff, T_empty]
intro a s has h hps h_disj
rw [Finset.sum_insert has, ← h]
swap; · exact fun i hi => hps i (Finset.mem_insert_of_mem hi)
swap;
· exact fun i hi j hj hij =>
h_disj i (Finset.mem_insert_of_mem hi) j (Finset.mem_insert_of_mem hj) hij
rw [←
h_add (S a) (⋃ i ∈ s, S i) (hS_meas a) (measurableSet_biUnion _ fun i _ => hS_meas i)
(hps a (Finset.mem_insert_self a s))]
· congr; convert Finset.iSup_insert a s S
· exact
((measure_biUnion_finset_le _ _).trans_lt <|
ENNReal.sum_lt_top fun i hi => hps i <| Finset.mem_insert_of_mem hi).ne
· simp_rw [Set.inter_iUnion]
refine iUnion_eq_empty.mpr fun i => iUnion_eq_empty.mpr fun hi => ?_
rw [← Set.disjoint_iff_inter_eq_empty]
refine h_disj a (Finset.mem_insert_self a s) i (Finset.mem_insert_of_mem hi) fun hai => ?_
rw [← hai] at hi
exact has hi
#align measure_theory.fin_meas_additive.map_Union_fin_meas_set_eq_sum MeasureTheory.FinMeasAdditive.map_iUnion_fin_meas_set_eq_sum
end FinMeasAdditive
/-- A `FinMeasAdditive` set function whose norm on every set is less than the measure of the
set (up to a multiplicative constant). -/
def DominatedFinMeasAdditive {β} [SeminormedAddCommGroup β] {_ : MeasurableSpace α} (μ : Measure α)
(T : Set α → β) (C : ℝ) : Prop :=
FinMeasAdditive μ T ∧ ∀ s, MeasurableSet s → μ s < ∞ → ‖T s‖ ≤ C * (μ s).toReal
#align measure_theory.dominated_fin_meas_additive MeasureTheory.DominatedFinMeasAdditive
namespace DominatedFinMeasAdditive
variable {β : Type*} [SeminormedAddCommGroup β] {T T' : Set α → β} {C C' : ℝ}
theorem zero {m : MeasurableSpace α} (μ : Measure α) (hC : 0 ≤ C) :
DominatedFinMeasAdditive μ (0 : Set α → β) C := by
refine ⟨FinMeasAdditive.zero, fun s _ _ => ?_⟩
rw [Pi.zero_apply, norm_zero]
exact mul_nonneg hC toReal_nonneg
#align measure_theory.dominated_fin_meas_additive.zero MeasureTheory.DominatedFinMeasAdditive.zero
theorem eq_zero_of_measure_zero {β : Type*} [NormedAddCommGroup β] {T : Set α → β} {C : ℝ}
(hT : DominatedFinMeasAdditive μ T C) {s : Set α} (hs : MeasurableSet s) (hs_zero : μ s = 0) :
T s = 0 := by
refine norm_eq_zero.mp ?_
refine ((hT.2 s hs (by simp [hs_zero])).trans (le_of_eq ?_)).antisymm (norm_nonneg _)
rw [hs_zero, ENNReal.zero_toReal, mul_zero]
#align measure_theory.dominated_fin_meas_additive.eq_zero_of_measure_zero MeasureTheory.DominatedFinMeasAdditive.eq_zero_of_measure_zero
theorem eq_zero {β : Type*} [NormedAddCommGroup β] {T : Set α → β} {C : ℝ} {m : MeasurableSpace α}
(hT : DominatedFinMeasAdditive (0 : Measure α) T C) {s : Set α} (hs : MeasurableSet s) :
T s = 0 :=
eq_zero_of_measure_zero hT hs (by simp only [Measure.coe_zero, Pi.zero_apply])
#align measure_theory.dominated_fin_meas_additive.eq_zero MeasureTheory.DominatedFinMeasAdditive.eq_zero
theorem add (hT : DominatedFinMeasAdditive μ T C) (hT' : DominatedFinMeasAdditive μ T' C') :
DominatedFinMeasAdditive μ (T + T') (C + C') := by
refine ⟨hT.1.add hT'.1, fun s hs hμs => ?_⟩
rw [Pi.add_apply, add_mul]
exact (norm_add_le _ _).trans (add_le_add (hT.2 s hs hμs) (hT'.2 s hs hμs))
#align measure_theory.dominated_fin_meas_additive.add MeasureTheory.DominatedFinMeasAdditive.add
theorem smul [NormedField 𝕜] [NormedSpace 𝕜 β] (hT : DominatedFinMeasAdditive μ T C) (c : 𝕜) :
DominatedFinMeasAdditive μ (fun s => c • T s) (‖c‖ * C) := by
refine ⟨hT.1.smul c, fun s hs hμs => ?_⟩
dsimp only
rw [norm_smul, mul_assoc]
exact mul_le_mul le_rfl (hT.2 s hs hμs) (norm_nonneg _) (norm_nonneg _)
#align measure_theory.dominated_fin_meas_additive.smul MeasureTheory.DominatedFinMeasAdditive.smul
theorem of_measure_le {μ' : Measure α} (h : μ ≤ μ') (hT : DominatedFinMeasAdditive μ T C)
(hC : 0 ≤ C) : DominatedFinMeasAdditive μ' T C := by
have h' : ∀ s, μ s = ∞ → μ' s = ∞ := fun s hs ↦ top_unique <| hs.symm.trans_le (h _)
refine ⟨hT.1.of_eq_top_imp_eq_top fun s _ ↦ h' s, fun s hs hμ's ↦ ?_⟩
have hμs : μ s < ∞ := (h s).trans_lt hμ's
calc
‖T s‖ ≤ C * (μ s).toReal := hT.2 s hs hμs
_ ≤ C * (μ' s).toReal := by gcongr; exacts [hμ's.ne, h _]
#align measure_theory.dominated_fin_meas_additive.of_measure_le MeasureTheory.DominatedFinMeasAdditive.of_measure_le
theorem add_measure_right {_ : MeasurableSpace α} (μ ν : Measure α)
(hT : DominatedFinMeasAdditive μ T C) (hC : 0 ≤ C) : DominatedFinMeasAdditive (μ + ν) T C :=
of_measure_le (Measure.le_add_right le_rfl) hT hC
#align measure_theory.dominated_fin_meas_additive.add_measure_right MeasureTheory.DominatedFinMeasAdditive.add_measure_right
theorem add_measure_left {_ : MeasurableSpace α} (μ ν : Measure α)
(hT : DominatedFinMeasAdditive ν T C) (hC : 0 ≤ C) : DominatedFinMeasAdditive (μ + ν) T C :=
of_measure_le (Measure.le_add_left le_rfl) hT hC
#align measure_theory.dominated_fin_meas_additive.add_measure_left MeasureTheory.DominatedFinMeasAdditive.add_measure_left
theorem of_smul_measure (c : ℝ≥0∞) (hc_ne_top : c ≠ ∞) (hT : DominatedFinMeasAdditive (c • μ) T C) :
DominatedFinMeasAdditive μ T (c.toReal * C) := by
have h : ∀ s, MeasurableSet s → c • μ s = ∞ → μ s = ∞ := by
intro s _ hcμs
simp only [hc_ne_top, Algebra.id.smul_eq_mul, ENNReal.mul_eq_top, or_false_iff, Ne,
false_and_iff] at hcμs
exact hcμs.2
refine ⟨hT.1.of_eq_top_imp_eq_top (μ := c • μ) h, fun s hs hμs => ?_⟩
have hcμs : c • μ s ≠ ∞ := mt (h s hs) hμs.ne
rw [smul_eq_mul] at hcμs
simp_rw [DominatedFinMeasAdditive, Measure.smul_apply, smul_eq_mul, toReal_mul] at hT
refine (hT.2 s hs hcμs.lt_top).trans (le_of_eq ?_)
ring
#align measure_theory.dominated_fin_meas_additive.of_smul_measure MeasureTheory.DominatedFinMeasAdditive.of_smul_measure
theorem of_measure_le_smul {μ' : Measure α} (c : ℝ≥0∞) (hc : c ≠ ∞) (h : μ ≤ c • μ')
(hT : DominatedFinMeasAdditive μ T C) (hC : 0 ≤ C) :
DominatedFinMeasAdditive μ' T (c.toReal * C) :=
(hT.of_measure_le h hC).of_smul_measure c hc
#align measure_theory.dominated_fin_meas_additive.of_measure_le_smul MeasureTheory.DominatedFinMeasAdditive.of_measure_le_smul
end DominatedFinMeasAdditive
end FinMeasAdditive
namespace SimpleFunc
/-- Extend `Set α → (F →L[ℝ] F')` to `(α →ₛ F) → F'`. -/
def setToSimpleFunc {_ : MeasurableSpace α} (T : Set α → F →L[ℝ] F') (f : α →ₛ F) : F' :=
∑ x ∈ f.range, T (f ⁻¹' {x}) x
#align measure_theory.simple_func.set_to_simple_func MeasureTheory.SimpleFunc.setToSimpleFunc
@[simp]
theorem setToSimpleFunc_zero {m : MeasurableSpace α} (f : α →ₛ F) :
setToSimpleFunc (0 : Set α → F →L[ℝ] F') f = 0 := by simp [setToSimpleFunc]
#align measure_theory.simple_func.set_to_simple_func_zero MeasureTheory.SimpleFunc.setToSimpleFunc_zero
theorem setToSimpleFunc_zero' {T : Set α → E →L[ℝ] F'}
(h_zero : ∀ s, MeasurableSet s → μ s < ∞ → T s = 0) (f : α →ₛ E) (hf : Integrable f μ) :
setToSimpleFunc T f = 0 := by
simp_rw [setToSimpleFunc]
refine sum_eq_zero fun x _ => ?_
by_cases hx0 : x = 0
· simp [hx0]
rw [h_zero (f ⁻¹' ({x} : Set E)) (measurableSet_fiber _ _)
(measure_preimage_lt_top_of_integrable f hf hx0),
ContinuousLinearMap.zero_apply]
#align measure_theory.simple_func.set_to_simple_func_zero' MeasureTheory.SimpleFunc.setToSimpleFunc_zero'
@[simp]
theorem setToSimpleFunc_zero_apply {m : MeasurableSpace α} (T : Set α → F →L[ℝ] F') :
setToSimpleFunc T (0 : α →ₛ F) = 0 := by
cases isEmpty_or_nonempty α <;> simp [setToSimpleFunc]
#align measure_theory.simple_func.set_to_simple_func_zero_apply MeasureTheory.SimpleFunc.setToSimpleFunc_zero_apply
theorem setToSimpleFunc_eq_sum_filter {m : MeasurableSpace α} (T : Set α → F →L[ℝ] F')
(f : α →ₛ F) :
setToSimpleFunc T f = ∑ x ∈ f.range.filter fun x => x ≠ 0, (T (f ⁻¹' {x})) x := by
symm
refine sum_filter_of_ne fun x _ => mt fun hx0 => ?_
rw [hx0]
exact ContinuousLinearMap.map_zero _
#align measure_theory.simple_func.set_to_simple_func_eq_sum_filter MeasureTheory.SimpleFunc.setToSimpleFunc_eq_sum_filter
theorem map_setToSimpleFunc (T : Set α → F →L[ℝ] F') (h_add : FinMeasAdditive μ T) {f : α →ₛ G}
(hf : Integrable f μ) {g : G → F} (hg : g 0 = 0) :
(f.map g).setToSimpleFunc T = ∑ x ∈ f.range, T (f ⁻¹' {x}) (g x) := by
have T_empty : T ∅ = 0 := h_add.map_empty_eq_zero
have hfp : ∀ x ∈ f.range, x ≠ 0 → μ (f ⁻¹' {x}) ≠ ∞ := fun x _ hx0 =>
(measure_preimage_lt_top_of_integrable f hf hx0).ne
simp only [setToSimpleFunc, range_map]
refine Finset.sum_image' _ fun b hb => ?_
rcases mem_range.1 hb with ⟨a, rfl⟩
by_cases h0 : g (f a) = 0
· simp_rw [h0]
rw [ContinuousLinearMap.map_zero, Finset.sum_eq_zero fun x hx => ?_]
rw [mem_filter] at hx
rw [hx.2, ContinuousLinearMap.map_zero]
have h_left_eq :
T (map g f ⁻¹' {g (f a)}) (g (f a)) =
T (f ⁻¹' (f.range.filter fun b => g b = g (f a))) (g (f a)) := by
congr; rw [map_preimage_singleton]
rw [h_left_eq]
have h_left_eq' :
T (f ⁻¹' (filter (fun b : G => g b = g (f a)) f.range)) (g (f a)) =
T (⋃ y ∈ filter (fun b : G => g b = g (f a)) f.range, f ⁻¹' {y}) (g (f a)) := by
congr; rw [← Finset.set_biUnion_preimage_singleton]
rw [h_left_eq']
rw [h_add.map_iUnion_fin_meas_set_eq_sum T T_empty]
· simp only [sum_apply, ContinuousLinearMap.coe_sum']
refine Finset.sum_congr rfl fun x hx => ?_
rw [mem_filter] at hx
rw [hx.2]
· exact fun i => measurableSet_fiber _ _
· intro i hi
rw [mem_filter] at hi
refine hfp i hi.1 fun hi0 => ?_
rw [hi0, hg] at hi
exact h0 hi.2.symm
· intro i _j hi _ hij
rw [Set.disjoint_iff]
intro x hx
rw [Set.mem_inter_iff, Set.mem_preimage, Set.mem_preimage, Set.mem_singleton_iff,
Set.mem_singleton_iff] at hx
rw [← hx.1, ← hx.2] at hij
exact absurd rfl hij
#align measure_theory.simple_func.map_set_to_simple_func MeasureTheory.SimpleFunc.map_setToSimpleFunc
theorem setToSimpleFunc_congr' (T : Set α → E →L[ℝ] F) (h_add : FinMeasAdditive μ T) {f g : α →ₛ E}
(hf : Integrable f μ) (hg : Integrable g μ)
(h : Pairwise fun x y => T (f ⁻¹' {x} ∩ g ⁻¹' {y}) = 0) :
f.setToSimpleFunc T = g.setToSimpleFunc T :=
show ((pair f g).map Prod.fst).setToSimpleFunc T = ((pair f g).map Prod.snd).setToSimpleFunc T by
have h_pair : Integrable (f.pair g) μ := integrable_pair hf hg
rw [map_setToSimpleFunc T h_add h_pair Prod.fst_zero]
rw [map_setToSimpleFunc T h_add h_pair Prod.snd_zero]
refine Finset.sum_congr rfl fun p hp => ?_
rcases mem_range.1 hp with ⟨a, rfl⟩
by_cases eq : f a = g a
· dsimp only [pair_apply]; rw [eq]
· have : T (pair f g ⁻¹' {(f a, g a)}) = 0 := by
have h_eq : T ((⇑(f.pair g)) ⁻¹' {(f a, g a)}) = T (f ⁻¹' {f a} ∩ g ⁻¹' {g a}) := by
congr; rw [pair_preimage_singleton f g]
rw [h_eq]
exact h eq
simp only [this, ContinuousLinearMap.zero_apply, pair_apply]
#align measure_theory.simple_func.set_to_simple_func_congr' MeasureTheory.SimpleFunc.setToSimpleFunc_congr'
theorem setToSimpleFunc_congr (T : Set α → E →L[ℝ] F)
(h_zero : ∀ s, MeasurableSet s → μ s = 0 → T s = 0) (h_add : FinMeasAdditive μ T) {f g : α →ₛ E}
(hf : Integrable f μ) (h : f =ᵐ[μ] g) : f.setToSimpleFunc T = g.setToSimpleFunc T := by
refine setToSimpleFunc_congr' T h_add hf ((integrable_congr h).mp hf) ?_
refine fun x y hxy => h_zero _ ((measurableSet_fiber f x).inter (measurableSet_fiber g y)) ?_
rw [EventuallyEq, ae_iff] at h
refine measure_mono_null (fun z => ?_) h
simp_rw [Set.mem_inter_iff, Set.mem_setOf_eq, Set.mem_preimage, Set.mem_singleton_iff]
intro h
rwa [h.1, h.2]
#align measure_theory.simple_func.set_to_simple_func_congr MeasureTheory.SimpleFunc.setToSimpleFunc_congr
theorem setToSimpleFunc_congr_left (T T' : Set α → E →L[ℝ] F)
(h : ∀ s, MeasurableSet s → μ s < ∞ → T s = T' s) (f : α →ₛ E) (hf : Integrable f μ) :
setToSimpleFunc T f = setToSimpleFunc T' f := by
simp_rw [setToSimpleFunc]
refine sum_congr rfl fun x _ => ?_
by_cases hx0 : x = 0
· simp [hx0]
· rw [h (f ⁻¹' {x}) (SimpleFunc.measurableSet_fiber _ _)
(SimpleFunc.measure_preimage_lt_top_of_integrable _ hf hx0)]
#align measure_theory.simple_func.set_to_simple_func_congr_left MeasureTheory.SimpleFunc.setToSimpleFunc_congr_left
| Mathlib/MeasureTheory/Integral/SetToL1.lean | 402 | 406 | theorem setToSimpleFunc_add_left {m : MeasurableSpace α} (T T' : Set α → F →L[ℝ] F') {f : α →ₛ F} :
setToSimpleFunc (T + T') f = setToSimpleFunc T f + setToSimpleFunc T' f := by |
simp_rw [setToSimpleFunc, Pi.add_apply]
push_cast
simp_rw [Pi.add_apply, sum_add_distrib]
|
/-
Copyright (c) 2021 Damiano Testa. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Damiano Testa
-/
import Mathlib.Algebra.Group.Basic
import Mathlib.Order.Basic
import Mathlib.Order.Monotone.Basic
#align_import algebra.covariant_and_contravariant from "leanprover-community/mathlib"@"2258b40dacd2942571c8ce136215350c702dc78f"
/-!
# Covariants and contravariants
This file contains general lemmas and instances to work with the interactions between a relation and
an action on a Type.
The intended application is the splitting of the ordering from the algebraic assumptions on the
operations in the `Ordered[...]` hierarchy.
The strategy is to introduce two more flexible typeclasses, `CovariantClass` and
`ContravariantClass`:
* `CovariantClass` models the implication `a ≤ b → c * a ≤ c * b` (multiplication is monotone),
* `ContravariantClass` models the implication `a * b < a * c → b < c`.
Since `Co(ntra)variantClass` takes as input the operation (typically `(+)` or `(*)`) and the order
relation (typically `(≤)` or `(<)`), these are the only two typeclasses that I have used.
The general approach is to formulate the lemma that you are interested in and prove it, with the
`Ordered[...]` typeclass of your liking. After that, you convert the single typeclass,
say `[OrderedCancelMonoid M]`, into three typeclasses, e.g.
`[CancelMonoid M] [PartialOrder M] [CovariantClass M M (Function.swap (*)) (≤)]`
and have a go at seeing if the proof still works!
Note that it is possible to combine several `Co(ntra)variantClass` assumptions together.
Indeed, the usual ordered typeclasses arise from assuming the pair
`[CovariantClass M M (*) (≤)] [ContravariantClass M M (*) (<)]`
on top of order/algebraic assumptions.
A formal remark is that normally `CovariantClass` uses the `(≤)`-relation, while
`ContravariantClass` uses the `(<)`-relation. This need not be the case in general, but seems to be
the most common usage. In the opposite direction, the implication
```lean
[Semigroup α] [PartialOrder α] [ContravariantClass α α (*) (≤)] → LeftCancelSemigroup α
```
holds -- note the `Co*ntra*` assumption on the `(≤)`-relation.
# Formalization notes
We stick to the convention of using `Function.swap (*)` (or `Function.swap (+)`), for the
typeclass assumptions, since `Function.swap` is slightly better behaved than `flip`.
However, sometimes as a **non-typeclass** assumption, we prefer `flip (*)` (or `flip (+)`),
as it is easier to use.
-/
-- TODO: convert `ExistsMulOfLE`, `ExistsAddOfLE`?
-- TODO: relationship with `Con/AddCon`
-- TODO: include equivalence of `LeftCancelSemigroup` with
-- `Semigroup PartialOrder ContravariantClass α α (*) (≤)`?
-- TODO : use ⇒, as per Eric's suggestion? See
-- https://leanprover.zulipchat.com/#narrow/stream/116395-maths/topic/ordered.20stuff/near/236148738
-- for a discussion.
open Function
section Variants
variable {M N : Type*} (μ : M → N → N) (r : N → N → Prop)
variable (M N)
/-- `Covariant` is useful to formulate succinctly statements about the interactions between an
action of a Type on another one and a relation on the acted-upon Type.
See the `CovariantClass` doc-string for its meaning. -/
def Covariant : Prop :=
∀ (m) {n₁ n₂}, r n₁ n₂ → r (μ m n₁) (μ m n₂)
#align covariant Covariant
/-- `Contravariant` is useful to formulate succinctly statements about the interactions between an
action of a Type on another one and a relation on the acted-upon Type.
See the `ContravariantClass` doc-string for its meaning. -/
def Contravariant : Prop :=
∀ (m) {n₁ n₂}, r (μ m n₁) (μ m n₂) → r n₁ n₂
#align contravariant Contravariant
/-- Given an action `μ` of a Type `M` on a Type `N` and a relation `r` on `N`, informally, the
`CovariantClass` says that "the action `μ` preserves the relation `r`."
More precisely, the `CovariantClass` is a class taking two Types `M N`, together with an "action"
`μ : M → N → N` and a relation `r : N → N → Prop`. Its unique field `elim` is the assertion that
for all `m ∈ M` and all elements `n₁, n₂ ∈ N`, if the relation `r` holds for the pair
`(n₁, n₂)`, then, the relation `r` also holds for the pair `(μ m n₁, μ m n₂)`,
obtained from `(n₁, n₂)` by acting upon it by `m`.
If `m : M` and `h : r n₁ n₂`, then `CovariantClass.elim m h : r (μ m n₁) (μ m n₂)`.
-/
class CovariantClass : Prop where
/-- For all `m ∈ M` and all elements `n₁, n₂ ∈ N`, if the relation `r` holds for the pair
`(n₁, n₂)`, then, the relation `r` also holds for the pair `(μ m n₁, μ m n₂)` -/
protected elim : Covariant M N μ r
#align covariant_class CovariantClass
/-- Given an action `μ` of a Type `M` on a Type `N` and a relation `r` on `N`, informally, the
`ContravariantClass` says that "if the result of the action `μ` on a pair satisfies the
relation `r`, then the initial pair satisfied the relation `r`."
More precisely, the `ContravariantClass` is a class taking two Types `M N`, together with an
"action" `μ : M → N → N` and a relation `r : N → N → Prop`. Its unique field `elim` is the
assertion that for all `m ∈ M` and all elements `n₁, n₂ ∈ N`, if the relation `r` holds for the
pair `(μ m n₁, μ m n₂)` obtained from `(n₁, n₂)` by acting upon it by `m`, then, the relation
`r` also holds for the pair `(n₁, n₂)`.
If `m : M` and `h : r (μ m n₁) (μ m n₂)`, then `ContravariantClass.elim m h : r n₁ n₂`.
-/
class ContravariantClass : Prop where
/-- For all `m ∈ M` and all elements `n₁, n₂ ∈ N`, if the relation `r` holds for the
pair `(μ m n₁, μ m n₂)` obtained from `(n₁, n₂)` by acting upon it by `m`, then, the relation
`r` also holds for the pair `(n₁, n₂)`. -/
protected elim : Contravariant M N μ r
#align contravariant_class ContravariantClass
theorem rel_iff_cov [CovariantClass M N μ r] [ContravariantClass M N μ r] (m : M) {a b : N} :
r (μ m a) (μ m b) ↔ r a b :=
⟨ContravariantClass.elim _, CovariantClass.elim _⟩
#align rel_iff_cov rel_iff_cov
section flip
variable {M N μ r}
theorem Covariant.flip (h : Covariant M N μ r) : Covariant M N μ (flip r) :=
fun a _ _ ↦ h a
#align covariant.flip Covariant.flip
theorem Contravariant.flip (h : Contravariant M N μ r) : Contravariant M N μ (flip r) :=
fun a _ _ ↦ h a
#align contravariant.flip Contravariant.flip
end flip
section Covariant
variable {M N μ r} [CovariantClass M N μ r]
theorem act_rel_act_of_rel (m : M) {a b : N} (ab : r a b) : r (μ m a) (μ m b) :=
CovariantClass.elim _ ab
#align act_rel_act_of_rel act_rel_act_of_rel
@[to_additive]
theorem Group.covariant_iff_contravariant [Group N] :
Covariant N N (· * ·) r ↔ Contravariant N N (· * ·) r := by
refine ⟨fun h a b c bc ↦ ?_, fun h a b c bc ↦ ?_⟩
· rw [← inv_mul_cancel_left a b, ← inv_mul_cancel_left a c]
exact h a⁻¹ bc
· rw [← inv_mul_cancel_left a b, ← inv_mul_cancel_left a c] at bc
exact h a⁻¹ bc
#align group.covariant_iff_contravariant Group.covariant_iff_contravariant
#align add_group.covariant_iff_contravariant AddGroup.covariant_iff_contravariant
@[to_additive]
instance (priority := 100) Group.covconv [Group N] [CovariantClass N N (· * ·) r] :
ContravariantClass N N (· * ·) r :=
⟨Group.covariant_iff_contravariant.mp CovariantClass.elim⟩
@[to_additive]
theorem Group.covariant_swap_iff_contravariant_swap [Group N] :
Covariant N N (swap (· * ·)) r ↔ Contravariant N N (swap (· * ·)) r := by
refine ⟨fun h a b c bc ↦ ?_, fun h a b c bc ↦ ?_⟩
· rw [← mul_inv_cancel_right b a, ← mul_inv_cancel_right c a]
exact h a⁻¹ bc
· rw [← mul_inv_cancel_right b a, ← mul_inv_cancel_right c a] at bc
exact h a⁻¹ bc
#align group.covariant_swap_iff_contravariant_swap Group.covariant_swap_iff_contravariant_swap
#align add_group.covariant_swap_iff_contravariant_swap AddGroup.covariant_swap_iff_contravariant_swap
@[to_additive]
instance (priority := 100) Group.covconv_swap [Group N] [CovariantClass N N (swap (· * ·)) r] :
ContravariantClass N N (swap (· * ·)) r :=
⟨Group.covariant_swap_iff_contravariant_swap.mp CovariantClass.elim⟩
section Trans
variable [IsTrans N r] (m n : M) {a b c d : N}
-- Lemmas with 3 elements.
theorem act_rel_of_rel_of_act_rel (ab : r a b) (rl : r (μ m b) c) : r (μ m a) c :=
_root_.trans (act_rel_act_of_rel m ab) rl
#align act_rel_of_rel_of_act_rel act_rel_of_rel_of_act_rel
theorem rel_act_of_rel_of_rel_act (ab : r a b) (rr : r c (μ m a)) : r c (μ m b) :=
_root_.trans rr (act_rel_act_of_rel _ ab)
#align rel_act_of_rel_of_rel_act rel_act_of_rel_of_rel_act
end Trans
end Covariant
-- Lemma with 4 elements.
section MEqN
variable {M N μ r} {mu : N → N → N} [IsTrans N r] [i : CovariantClass N N mu r]
[i' : CovariantClass N N (swap mu) r] {a b c d : N}
theorem act_rel_act_of_rel_of_rel (ab : r a b) (cd : r c d) : r (mu a c) (mu b d) :=
_root_.trans (@act_rel_act_of_rel _ _ (swap mu) r _ c _ _ ab) (act_rel_act_of_rel b cd)
#align act_rel_act_of_rel_of_rel act_rel_act_of_rel_of_rel
end MEqN
section Contravariant
variable {M N μ r} [ContravariantClass M N μ r]
theorem rel_of_act_rel_act (m : M) {a b : N} (ab : r (μ m a) (μ m b)) : r a b :=
ContravariantClass.elim _ ab
#align rel_of_act_rel_act rel_of_act_rel_act
section Trans
variable [IsTrans N r] (m n : M) {a b c d : N}
-- Lemmas with 3 elements.
theorem act_rel_of_act_rel_of_rel_act_rel (ab : r (μ m a) b) (rl : r (μ m b) (μ m c)) :
r (μ m a) c :=
_root_.trans ab (rel_of_act_rel_act m rl)
#align act_rel_of_act_rel_of_rel_act_rel act_rel_of_act_rel_of_rel_act_rel
theorem rel_act_of_act_rel_act_of_rel_act (ab : r (μ m a) (μ m b)) (rr : r b (μ m c)) :
r a (μ m c) :=
_root_.trans (rel_of_act_rel_act m ab) rr
#align rel_act_of_act_rel_act_of_rel_act rel_act_of_act_rel_act_of_rel_act
end Trans
end Contravariant
section Monotone
variable {α : Type*} {M N μ} [Preorder α] [Preorder N]
variable {f : N → α}
/-- The partial application of a constant to a covariant operator is monotone. -/
theorem Covariant.monotone_of_const [CovariantClass M N μ (· ≤ ·)] (m : M) : Monotone (μ m) :=
fun _ _ ↦ CovariantClass.elim m
#align covariant.monotone_of_const Covariant.monotone_of_const
/-- A monotone function remains monotone when composed with the partial application
of a covariant operator. E.g., `∀ (m : ℕ), Monotone f → Monotone (fun n ↦ f (m + n))`. -/
theorem Monotone.covariant_of_const [CovariantClass M N μ (· ≤ ·)] (hf : Monotone f) (m : M) :
Monotone (f <| μ m ·) :=
hf.comp (Covariant.monotone_of_const m)
#align monotone.covariant_of_const Monotone.covariant_of_const
/-- Same as `Monotone.covariant_of_const`, but with the constant on the other side of
the operator. E.g., `∀ (m : ℕ), Monotone f → Monotone (fun n ↦ f (n + m))`. -/
theorem Monotone.covariant_of_const' {μ : N → N → N} [CovariantClass N N (swap μ) (· ≤ ·)]
(hf : Monotone f) (m : N) : Monotone (f <| μ · m) :=
Monotone.covariant_of_const (μ := swap μ) hf m
#align monotone.covariant_of_const' Monotone.covariant_of_const'
/-- Dual of `Monotone.covariant_of_const` -/
theorem Antitone.covariant_of_const [CovariantClass M N μ (· ≤ ·)] (hf : Antitone f) (m : M) :
Antitone (f <| μ m ·) :=
hf.comp_monotone <| Covariant.monotone_of_const m
#align antitone.covariant_of_const Antitone.covariant_of_const
/-- Dual of `Monotone.covariant_of_const'` -/
theorem Antitone.covariant_of_const' {μ : N → N → N} [CovariantClass N N (swap μ) (· ≤ ·)]
(hf : Antitone f) (m : N) : Antitone (f <| μ · m) :=
Antitone.covariant_of_const (μ := swap μ) hf m
#align antitone.covariant_of_const' Antitone.covariant_of_const'
end Monotone
theorem covariant_le_of_covariant_lt [PartialOrder N] :
Covariant M N μ (· < ·) → Covariant M N μ (· ≤ ·) := by
intro h a b c bc
rcases bc.eq_or_lt with (rfl | bc)
· exact le_rfl
· exact (h _ bc).le
#align covariant_le_of_covariant_lt covariant_le_of_covariant_lt
theorem covariantClass_le_of_lt [PartialOrder N] [CovariantClass M N μ (· < ·)] :
CovariantClass M N μ (· ≤ ·) := ⟨covariant_le_of_covariant_lt _ _ _ CovariantClass.elim⟩
| Mathlib/Algebra/Order/Monoid/Unbundled/Defs.lean | 292 | 297 | theorem contravariant_le_iff_contravariant_lt_and_eq [PartialOrder N] :
Contravariant M N μ (· ≤ ·) ↔ Contravariant M N μ (· < ·) ∧ Contravariant M N μ (· = ·) := by |
refine ⟨fun h ↦ ⟨fun a b c bc ↦ ?_, fun a b c bc ↦ ?_⟩, fun h ↦ fun a b c bc ↦ ?_⟩
· exact (h a bc.le).lt_of_ne (by rintro rfl; exact lt_irrefl _ bc)
· exact (h a bc.le).antisymm (h a bc.ge)
· exact bc.lt_or_eq.elim (fun bc ↦ (h.1 a bc).le) (fun bc ↦ (h.2 a bc).le)
|
/-
Copyright (c) 2020 Anatole Dedecker. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Anatole Dedecker, Alexey Soloyev, Junyan Xu, Kamila Szewczyk
-/
import Mathlib.Data.Real.Irrational
import Mathlib.Data.Nat.Fib.Basic
import Mathlib.Data.Fin.VecNotation
import Mathlib.Algebra.LinearRecurrence
import Mathlib.Tactic.NormNum.NatFib
import Mathlib.Tactic.NormNum.Prime
#align_import data.real.golden_ratio from "leanprover-community/mathlib"@"2196ab363eb097c008d4497125e0dde23fb36db2"
/-!
# The golden ratio and its conjugate
This file defines the golden ratio `φ := (1 + √5)/2` and its conjugate
`ψ := (1 - √5)/2`, which are the two real roots of `X² - X - 1`.
Along with various computational facts about them, we prove their
irrationality, and we link them to the Fibonacci sequence by proving
Binet's formula.
-/
noncomputable section
open Polynomial
/-- The golden ratio `φ := (1 + √5)/2`. -/
abbrev goldenRatio : ℝ := (1 + √5) / 2
#align golden_ratio goldenRatio
/-- The conjugate of the golden ratio `ψ := (1 - √5)/2`. -/
abbrev goldenConj : ℝ := (1 - √5) / 2
#align golden_conj goldenConj
@[inherit_doc goldenRatio] scoped[goldenRatio] notation "φ" => goldenRatio
@[inherit_doc goldenConj] scoped[goldenRatio] notation "ψ" => goldenConj
open Real goldenRatio
/-- The inverse of the golden ratio is the opposite of its conjugate. -/
theorem inv_gold : φ⁻¹ = -ψ := by
have : 1 + √5 ≠ 0 := ne_of_gt (add_pos (by norm_num) <| Real.sqrt_pos.mpr (by norm_num))
field_simp [sub_mul, mul_add]
norm_num
#align inv_gold inv_gold
/-- The opposite of the golden ratio is the inverse of its conjugate. -/
| Mathlib/Data/Real/GoldenRatio.lean | 51 | 53 | theorem inv_goldConj : ψ⁻¹ = -φ := by |
rw [inv_eq_iff_eq_inv, ← neg_inv, ← neg_eq_iff_eq_neg]
exact inv_gold.symm
|
/-
Copyright (c) 2021 Aaron Anderson, Jesse Michael Han, Floris van Doorn. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Aaron Anderson, Jesse Michael Han, Floris van Doorn
-/
import Mathlib.Data.Finset.Basic
import Mathlib.ModelTheory.Syntax
import Mathlib.Data.List.ProdSigma
#align_import model_theory.semantics from "leanprover-community/mathlib"@"d565b3df44619c1498326936be16f1a935df0728"
/-!
# Basics on First-Order Semantics
This file defines the interpretations of first-order terms, formulas, sentences, and theories
in a style inspired by the [Flypitch project](https://flypitch.github.io/).
## Main Definitions
* `FirstOrder.Language.Term.realize` is defined so that `t.realize v` is the term `t` evaluated at
variables `v`.
* `FirstOrder.Language.BoundedFormula.Realize` is defined so that `φ.Realize v xs` is the bounded
formula `φ` evaluated at tuples of variables `v` and `xs`.
* `FirstOrder.Language.Formula.Realize` is defined so that `φ.Realize v` is the formula `φ`
evaluated at variables `v`.
* `FirstOrder.Language.Sentence.Realize` is defined so that `φ.Realize M` is the sentence `φ`
evaluated in the structure `M`. Also denoted `M ⊨ φ`.
* `FirstOrder.Language.Theory.Model` is defined so that `T.Model M` is true if and only if every
sentence of `T` is realized in `M`. Also denoted `T ⊨ φ`.
## Main Results
* `FirstOrder.Language.BoundedFormula.realize_toPrenex` shows that the prenex normal form of a
formula has the same realization as the original formula.
* Several results in this file show that syntactic constructions such as `relabel`, `castLE`,
`liftAt`, `subst`, and the actions of language maps commute with realization of terms, formulas,
sentences, and theories.
## Implementation Notes
* Formulas use a modified version of de Bruijn variables. Specifically, a `L.BoundedFormula α n`
is a formula with some variables indexed by a type `α`, which cannot be quantified over, and some
indexed by `Fin n`, which can. For any `φ : L.BoundedFormula α (n + 1)`, we define the formula
`∀' φ : L.BoundedFormula α n` by universally quantifying over the variable indexed by
`n : Fin (n + 1)`.
## References
For the Flypitch project:
- [J. Han, F. van Doorn, *A formal proof of the independence of the continuum hypothesis*]
[flypitch_cpp]
- [J. Han, F. van Doorn, *A formalization of forcing and the unprovability of
the continuum hypothesis*][flypitch_itp]
-/
universe u v w u' v'
namespace FirstOrder
namespace Language
variable {L : Language.{u, v}} {L' : Language}
variable {M : Type w} {N P : Type*} [L.Structure M] [L.Structure N] [L.Structure P]
variable {α : Type u'} {β : Type v'} {γ : Type*}
open FirstOrder Cardinal
open Structure Cardinal Fin
namespace Term
-- Porting note: universes in different order
/-- A term `t` with variables indexed by `α` can be evaluated by giving a value to each variable. -/
def realize (v : α → M) : ∀ _t : L.Term α, M
| var k => v k
| func f ts => funMap f fun i => (ts i).realize v
#align first_order.language.term.realize FirstOrder.Language.Term.realize
/- Porting note: The equation lemma of `realize` is too strong; it simplifies terms like the LHS of
`realize_functions_apply₁`. Even `eqns` can't fix this. We removed `simp` attr from `realize` and
prepare new simp lemmas for `realize`. -/
@[simp]
theorem realize_var (v : α → M) (k) : realize v (var k : L.Term α) = v k := rfl
@[simp]
theorem realize_func (v : α → M) {n} (f : L.Functions n) (ts) :
realize v (func f ts : L.Term α) = funMap f fun i => (ts i).realize v := rfl
@[simp]
theorem realize_relabel {t : L.Term α} {g : α → β} {v : β → M} :
(t.relabel g).realize v = t.realize (v ∘ g) := by
induction' t with _ n f ts ih
· rfl
· simp [ih]
#align first_order.language.term.realize_relabel FirstOrder.Language.Term.realize_relabel
@[simp]
theorem realize_liftAt {n n' m : ℕ} {t : L.Term (Sum α (Fin n))} {v : Sum α (Fin (n + n')) → M} :
(t.liftAt n' m).realize v =
t.realize (v ∘ Sum.map id fun i : Fin _ =>
if ↑i < m then Fin.castAdd n' i else Fin.addNat i n') :=
realize_relabel
#align first_order.language.term.realize_lift_at FirstOrder.Language.Term.realize_liftAt
@[simp]
theorem realize_constants {c : L.Constants} {v : α → M} : c.term.realize v = c :=
funMap_eq_coe_constants
#align first_order.language.term.realize_constants FirstOrder.Language.Term.realize_constants
@[simp]
theorem realize_functions_apply₁ {f : L.Functions 1} {t : L.Term α} {v : α → M} :
(f.apply₁ t).realize v = funMap f ![t.realize v] := by
rw [Functions.apply₁, Term.realize]
refine congr rfl (funext fun i => ?_)
simp only [Matrix.cons_val_fin_one]
#align first_order.language.term.realize_functions_apply₁ FirstOrder.Language.Term.realize_functions_apply₁
@[simp]
theorem realize_functions_apply₂ {f : L.Functions 2} {t₁ t₂ : L.Term α} {v : α → M} :
(f.apply₂ t₁ t₂).realize v = funMap f ![t₁.realize v, t₂.realize v] := by
rw [Functions.apply₂, Term.realize]
refine congr rfl (funext (Fin.cases ?_ ?_))
· simp only [Matrix.cons_val_zero]
· simp only [Matrix.cons_val_succ, Matrix.cons_val_fin_one, forall_const]
#align first_order.language.term.realize_functions_apply₂ FirstOrder.Language.Term.realize_functions_apply₂
theorem realize_con {A : Set M} {a : A} {v : α → M} : (L.con a).term.realize v = a :=
rfl
#align first_order.language.term.realize_con FirstOrder.Language.Term.realize_con
@[simp]
theorem realize_subst {t : L.Term α} {tf : α → L.Term β} {v : β → M} :
(t.subst tf).realize v = t.realize fun a => (tf a).realize v := by
induction' t with _ _ _ _ ih
· rfl
· simp [ih]
#align first_order.language.term.realize_subst FirstOrder.Language.Term.realize_subst
@[simp]
theorem realize_restrictVar [DecidableEq α] {t : L.Term α} {s : Set α} (h : ↑t.varFinset ⊆ s)
{v : α → M} : (t.restrictVar (Set.inclusion h)).realize (v ∘ (↑)) = t.realize v := by
induction' t with _ _ _ _ ih
· rfl
· simp_rw [varFinset, Finset.coe_biUnion, Set.iUnion_subset_iff] at h
exact congr rfl (funext fun i => ih i (h i (Finset.mem_univ i)))
#align first_order.language.term.realize_restrict_var FirstOrder.Language.Term.realize_restrictVar
@[simp]
theorem realize_restrictVarLeft [DecidableEq α] {γ : Type*} {t : L.Term (Sum α γ)} {s : Set α}
(h : ↑t.varFinsetLeft ⊆ s) {v : α → M} {xs : γ → M} :
(t.restrictVarLeft (Set.inclusion h)).realize (Sum.elim (v ∘ (↑)) xs) =
t.realize (Sum.elim v xs) := by
induction' t with a _ _ _ ih
· cases a <;> rfl
· simp_rw [varFinsetLeft, Finset.coe_biUnion, Set.iUnion_subset_iff] at h
exact congr rfl (funext fun i => ih i (h i (Finset.mem_univ i)))
#align first_order.language.term.realize_restrict_var_left FirstOrder.Language.Term.realize_restrictVarLeft
@[simp]
theorem realize_constantsToVars [L[[α]].Structure M] [(lhomWithConstants L α).IsExpansionOn M]
{t : L[[α]].Term β} {v : β → M} :
t.constantsToVars.realize (Sum.elim (fun a => ↑(L.con a)) v) = t.realize v := by
induction' t with _ n f ts ih
· simp
· cases n
· cases f
· simp only [realize, ih, Nat.zero_eq, constantsOn, mk₂_Functions]
-- Porting note: below lemma does not work with simp for some reason
rw [withConstants_funMap_sum_inl]
· simp only [realize, constantsToVars, Sum.elim_inl, funMap_eq_coe_constants]
rfl
· cases' f with _ f
· simp only [realize, ih, constantsOn, mk₂_Functions]
-- Porting note: below lemma does not work with simp for some reason
rw [withConstants_funMap_sum_inl]
· exact isEmptyElim f
#align first_order.language.term.realize_constants_to_vars FirstOrder.Language.Term.realize_constantsToVars
@[simp]
theorem realize_varsToConstants [L[[α]].Structure M] [(lhomWithConstants L α).IsExpansionOn M]
{t : L.Term (Sum α β)} {v : β → M} :
t.varsToConstants.realize v = t.realize (Sum.elim (fun a => ↑(L.con a)) v) := by
induction' t with ab n f ts ih
· cases' ab with a b
-- Porting note: both cases were `simp [Language.con]`
· simp [Language.con, realize, funMap_eq_coe_constants]
· simp [realize, constantMap]
· simp only [realize, constantsOn, mk₂_Functions, ih]
-- Porting note: below lemma does not work with simp for some reason
rw [withConstants_funMap_sum_inl]
#align first_order.language.term.realize_vars_to_constants FirstOrder.Language.Term.realize_varsToConstants
theorem realize_constantsVarsEquivLeft [L[[α]].Structure M]
[(lhomWithConstants L α).IsExpansionOn M] {n} {t : L[[α]].Term (Sum β (Fin n))} {v : β → M}
{xs : Fin n → M} :
(constantsVarsEquivLeft t).realize (Sum.elim (Sum.elim (fun a => ↑(L.con a)) v) xs) =
t.realize (Sum.elim v xs) := by
simp only [constantsVarsEquivLeft, realize_relabel, Equiv.coe_trans, Function.comp_apply,
constantsVarsEquiv_apply, relabelEquiv_symm_apply]
refine _root_.trans ?_ realize_constantsToVars
rcongr x
rcases x with (a | (b | i)) <;> simp
#align first_order.language.term.realize_constants_vars_equiv_left FirstOrder.Language.Term.realize_constantsVarsEquivLeft
end Term
namespace LHom
@[simp]
theorem realize_onTerm [L'.Structure M] (φ : L →ᴸ L') [φ.IsExpansionOn M] (t : L.Term α)
(v : α → M) : (φ.onTerm t).realize v = t.realize v := by
induction' t with _ n f ts ih
· rfl
· simp only [Term.realize, LHom.onTerm, LHom.map_onFunction, ih]
set_option linter.uppercaseLean3 false in
#align first_order.language.Lhom.realize_on_term FirstOrder.Language.LHom.realize_onTerm
end LHom
@[simp]
theorem Hom.realize_term (g : M →[L] N) {t : L.Term α} {v : α → M} :
t.realize (g ∘ v) = g (t.realize v) := by
induction t
· rfl
· rw [Term.realize, Term.realize, g.map_fun]
refine congr rfl ?_
ext x
simp [*]
#align first_order.language.hom.realize_term FirstOrder.Language.Hom.realize_term
@[simp]
theorem Embedding.realize_term {v : α → M} (t : L.Term α) (g : M ↪[L] N) :
t.realize (g ∘ v) = g (t.realize v) :=
g.toHom.realize_term
#align first_order.language.embedding.realize_term FirstOrder.Language.Embedding.realize_term
@[simp]
theorem Equiv.realize_term {v : α → M} (t : L.Term α) (g : M ≃[L] N) :
t.realize (g ∘ v) = g (t.realize v) :=
g.toHom.realize_term
#align first_order.language.equiv.realize_term FirstOrder.Language.Equiv.realize_term
variable {n : ℕ}
namespace BoundedFormula
open Term
-- Porting note: universes in different order
/-- A bounded formula can be evaluated as true or false by giving values to each free variable. -/
def Realize : ∀ {l} (_f : L.BoundedFormula α l) (_v : α → M) (_xs : Fin l → M), Prop
| _, falsum, _v, _xs => False
| _, equal t₁ t₂, v, xs => t₁.realize (Sum.elim v xs) = t₂.realize (Sum.elim v xs)
| _, rel R ts, v, xs => RelMap R fun i => (ts i).realize (Sum.elim v xs)
| _, imp f₁ f₂, v, xs => Realize f₁ v xs → Realize f₂ v xs
| _, all f, v, xs => ∀ x : M, Realize f v (snoc xs x)
#align first_order.language.bounded_formula.realize FirstOrder.Language.BoundedFormula.Realize
variable {l : ℕ} {φ ψ : L.BoundedFormula α l} {θ : L.BoundedFormula α l.succ}
variable {v : α → M} {xs : Fin l → M}
@[simp]
theorem realize_bot : (⊥ : L.BoundedFormula α l).Realize v xs ↔ False :=
Iff.rfl
#align first_order.language.bounded_formula.realize_bot FirstOrder.Language.BoundedFormula.realize_bot
@[simp]
theorem realize_not : φ.not.Realize v xs ↔ ¬φ.Realize v xs :=
Iff.rfl
#align first_order.language.bounded_formula.realize_not FirstOrder.Language.BoundedFormula.realize_not
@[simp]
theorem realize_bdEqual (t₁ t₂ : L.Term (Sum α (Fin l))) :
(t₁.bdEqual t₂).Realize v xs ↔ t₁.realize (Sum.elim v xs) = t₂.realize (Sum.elim v xs) :=
Iff.rfl
#align first_order.language.bounded_formula.realize_bd_equal FirstOrder.Language.BoundedFormula.realize_bdEqual
@[simp]
theorem realize_top : (⊤ : L.BoundedFormula α l).Realize v xs ↔ True := by simp [Top.top]
#align first_order.language.bounded_formula.realize_top FirstOrder.Language.BoundedFormula.realize_top
@[simp]
theorem realize_inf : (φ ⊓ ψ).Realize v xs ↔ φ.Realize v xs ∧ ψ.Realize v xs := by
simp [Inf.inf, Realize]
#align first_order.language.bounded_formula.realize_inf FirstOrder.Language.BoundedFormula.realize_inf
@[simp]
theorem realize_foldr_inf (l : List (L.BoundedFormula α n)) (v : α → M) (xs : Fin n → M) :
(l.foldr (· ⊓ ·) ⊤).Realize v xs ↔ ∀ φ ∈ l, BoundedFormula.Realize φ v xs := by
induction' l with φ l ih
· simp
· simp [ih]
#align first_order.language.bounded_formula.realize_foldr_inf FirstOrder.Language.BoundedFormula.realize_foldr_inf
@[simp]
theorem realize_imp : (φ.imp ψ).Realize v xs ↔ φ.Realize v xs → ψ.Realize v xs := by
simp only [Realize]
#align first_order.language.bounded_formula.realize_imp FirstOrder.Language.BoundedFormula.realize_imp
@[simp]
theorem realize_rel {k : ℕ} {R : L.Relations k} {ts : Fin k → L.Term _} :
(R.boundedFormula ts).Realize v xs ↔ RelMap R fun i => (ts i).realize (Sum.elim v xs) :=
Iff.rfl
#align first_order.language.bounded_formula.realize_rel FirstOrder.Language.BoundedFormula.realize_rel
@[simp]
| Mathlib/ModelTheory/Semantics.lean | 305 | 309 | theorem realize_rel₁ {R : L.Relations 1} {t : L.Term _} :
(R.boundedFormula₁ t).Realize v xs ↔ RelMap R ![t.realize (Sum.elim v xs)] := by |
rw [Relations.boundedFormula₁, realize_rel, iff_eq_eq]
refine congr rfl (funext fun _ => ?_)
simp only [Matrix.cons_val_fin_one]
|
/-
Copyright (c) 2021 Heather Macbeth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Heather Macbeth, Yury Kudryashov
-/
import Mathlib.Topology.Order.Basic
#align_import topology.algebra.order.monotone_convergence from "leanprover-community/mathlib"@"4c19a16e4b705bf135cf9a80ac18fcc99c438514"
/-!
# Bounded monotone sequences converge
In this file we prove a few theorems of the form “if the range of a monotone function `f : ι → α`
admits a least upper bound `a`, then `f x` tends to `a` as `x → ∞`”, as well as version of this
statement for (conditionally) complete lattices that use `⨆ x, f x` instead of `IsLUB`.
These theorems work for linear orders with order topologies as well as their products (both in terms
of `Prod` and in terms of function types). In order to reduce code duplication, we introduce two
typeclasses (one for the property formulated above and one for the dual property), prove theorems
assuming one of these typeclasses, and provide instances for linear orders and their products.
We also prove some "inverse" results: if `f n` is a monotone sequence and `a` is its limit,
then `f n ≤ a` for all `n`.
## Tags
monotone convergence
-/
open Filter Set Function
open scoped Classical
open Filter Topology
variable {α β : Type*}
/-- We say that `α` is a `SupConvergenceClass` if the following holds. Let `f : ι → α` be a
monotone function, let `a : α` be a least upper bound of `Set.range f`. Then `f x` tends to `𝓝 a`
as `x → ∞` (formally, at the filter `Filter.atTop`). We require this for `ι = (s : Set α)`,
`f = CoeTC.coe` in the definition, then prove it for any `f` in `tendsto_atTop_isLUB`.
This property holds for linear orders with order topology as well as their products. -/
class SupConvergenceClass (α : Type*) [Preorder α] [TopologicalSpace α] : Prop where
/-- proof that a monotone function tends to `𝓝 a` as `x → ∞` -/
tendsto_coe_atTop_isLUB :
∀ (a : α) (s : Set α), IsLUB s a → Tendsto (CoeTC.coe : s → α) atTop (𝓝 a)
#align Sup_convergence_class SupConvergenceClass
/-- We say that `α` is an `InfConvergenceClass` if the following holds. Let `f : ι → α` be a
monotone function, let `a : α` be a greatest lower bound of `Set.range f`. Then `f x` tends to `𝓝 a`
as `x → -∞` (formally, at the filter `Filter.atBot`). We require this for `ι = (s : Set α)`,
`f = CoeTC.coe` in the definition, then prove it for any `f` in `tendsto_atBot_isGLB`.
This property holds for linear orders with order topology as well as their products. -/
class InfConvergenceClass (α : Type*) [Preorder α] [TopologicalSpace α] : Prop where
/-- proof that a monotone function tends to `𝓝 a` as `x → -∞`-/
tendsto_coe_atBot_isGLB :
∀ (a : α) (s : Set α), IsGLB s a → Tendsto (CoeTC.coe : s → α) atBot (𝓝 a)
#align Inf_convergence_class InfConvergenceClass
instance OrderDual.supConvergenceClass [Preorder α] [TopologicalSpace α] [InfConvergenceClass α] :
SupConvergenceClass αᵒᵈ :=
⟨‹InfConvergenceClass α›.1⟩
#align order_dual.Sup_convergence_class OrderDual.supConvergenceClass
instance OrderDual.infConvergenceClass [Preorder α] [TopologicalSpace α] [SupConvergenceClass α] :
InfConvergenceClass αᵒᵈ :=
⟨‹SupConvergenceClass α›.1⟩
#align order_dual.Inf_convergence_class OrderDual.infConvergenceClass
-- see Note [lower instance priority]
instance (priority := 100) LinearOrder.supConvergenceClass [TopologicalSpace α] [LinearOrder α]
[OrderTopology α] : SupConvergenceClass α := by
refine ⟨fun a s ha => tendsto_order.2 ⟨fun b hb => ?_, fun b hb => ?_⟩⟩
· rcases ha.exists_between hb with ⟨c, hcs, bc, bca⟩
lift c to s using hcs
exact (eventually_ge_atTop c).mono fun x hx => bc.trans_le hx
· exact eventually_of_forall fun x => (ha.1 x.2).trans_lt hb
#align linear_order.Sup_convergence_class LinearOrder.supConvergenceClass
-- see Note [lower instance priority]
instance (priority := 100) LinearOrder.infConvergenceClass [TopologicalSpace α] [LinearOrder α]
[OrderTopology α] : InfConvergenceClass α :=
show InfConvergenceClass αᵒᵈᵒᵈ from OrderDual.infConvergenceClass
#align linear_order.Inf_convergence_class LinearOrder.infConvergenceClass
section
variable {ι : Type*} [Preorder ι] [TopologicalSpace α]
section IsLUB
variable [Preorder α] [SupConvergenceClass α] {f : ι → α} {a : α}
theorem tendsto_atTop_isLUB (h_mono : Monotone f) (ha : IsLUB (Set.range f) a) :
Tendsto f atTop (𝓝 a) := by
suffices Tendsto (rangeFactorization f) atTop atTop from
(SupConvergenceClass.tendsto_coe_atTop_isLUB _ _ ha).comp this
exact h_mono.rangeFactorization.tendsto_atTop_atTop fun b => b.2.imp fun a ha => ha.ge
#align tendsto_at_top_is_lub tendsto_atTop_isLUB
theorem tendsto_atBot_isLUB (h_anti : Antitone f) (ha : IsLUB (Set.range f) a) :
Tendsto f atBot (𝓝 a) := by convert tendsto_atTop_isLUB h_anti.dual_left ha using 1
#align tendsto_at_bot_is_lub tendsto_atBot_isLUB
end IsLUB
section IsGLB
variable [Preorder α] [InfConvergenceClass α] {f : ι → α} {a : α}
theorem tendsto_atBot_isGLB (h_mono : Monotone f) (ha : IsGLB (Set.range f) a) :
Tendsto f atBot (𝓝 a) := by convert tendsto_atTop_isLUB h_mono.dual ha.dual using 1
#align tendsto_at_bot_is_glb tendsto_atBot_isGLB
theorem tendsto_atTop_isGLB (h_anti : Antitone f) (ha : IsGLB (Set.range f) a) :
Tendsto f atTop (𝓝 a) := by convert tendsto_atBot_isLUB h_anti.dual ha.dual using 1
#align tendsto_at_top_is_glb tendsto_atTop_isGLB
end IsGLB
section CiSup
variable [ConditionallyCompleteLattice α] [SupConvergenceClass α] {f : ι → α} {a : α}
theorem tendsto_atTop_ciSup (h_mono : Monotone f) (hbdd : BddAbove <| range f) :
Tendsto f atTop (𝓝 (⨆ i, f i)) := by
cases isEmpty_or_nonempty ι
exacts [tendsto_of_isEmpty, tendsto_atTop_isLUB h_mono (isLUB_ciSup hbdd)]
#align tendsto_at_top_csupr tendsto_atTop_ciSup
theorem tendsto_atBot_ciSup (h_anti : Antitone f) (hbdd : BddAbove <| range f) :
Tendsto f atBot (𝓝 (⨆ i, f i)) := by convert tendsto_atTop_ciSup h_anti.dual hbdd.dual using 1
#align tendsto_at_bot_csupr tendsto_atBot_ciSup
end CiSup
section CiInf
variable [ConditionallyCompleteLattice α] [InfConvergenceClass α] {f : ι → α} {a : α}
theorem tendsto_atBot_ciInf (h_mono : Monotone f) (hbdd : BddBelow <| range f) :
Tendsto f atBot (𝓝 (⨅ i, f i)) := by convert tendsto_atTop_ciSup h_mono.dual hbdd.dual using 1
#align tendsto_at_bot_cinfi tendsto_atBot_ciInf
theorem tendsto_atTop_ciInf (h_anti : Antitone f) (hbdd : BddBelow <| range f) :
Tendsto f atTop (𝓝 (⨅ i, f i)) := by convert tendsto_atBot_ciSup h_anti.dual hbdd.dual using 1
#align tendsto_at_top_cinfi tendsto_atTop_ciInf
end CiInf
section iSup
variable [CompleteLattice α] [SupConvergenceClass α] {f : ι → α} {a : α}
theorem tendsto_atTop_iSup (h_mono : Monotone f) : Tendsto f atTop (𝓝 (⨆ i, f i)) :=
tendsto_atTop_ciSup h_mono (OrderTop.bddAbove _)
#align tendsto_at_top_supr tendsto_atTop_iSup
theorem tendsto_atBot_iSup (h_anti : Antitone f) : Tendsto f atBot (𝓝 (⨆ i, f i)) :=
tendsto_atBot_ciSup h_anti (OrderTop.bddAbove _)
#align tendsto_at_bot_supr tendsto_atBot_iSup
end iSup
section iInf
variable [CompleteLattice α] [InfConvergenceClass α] {f : ι → α} {a : α}
theorem tendsto_atBot_iInf (h_mono : Monotone f) : Tendsto f atBot (𝓝 (⨅ i, f i)) :=
tendsto_atBot_ciInf h_mono (OrderBot.bddBelow _)
#align tendsto_at_bot_infi tendsto_atBot_iInf
theorem tendsto_atTop_iInf (h_anti : Antitone f) : Tendsto f atTop (𝓝 (⨅ i, f i)) :=
tendsto_atTop_ciInf h_anti (OrderBot.bddBelow _)
#align tendsto_at_top_infi tendsto_atTop_iInf
end iInf
end
instance Prod.supConvergenceClass
[Preorder α] [Preorder β] [TopologicalSpace α] [TopologicalSpace β]
[SupConvergenceClass α] [SupConvergenceClass β] : SupConvergenceClass (α × β) := by
constructor
rintro ⟨a, b⟩ s h
rw [isLUB_prod, ← range_restrict, ← range_restrict] at h
have A : Tendsto (fun x : s => (x : α × β).1) atTop (𝓝 a) :=
tendsto_atTop_isLUB (monotone_fst.restrict s) h.1
have B : Tendsto (fun x : s => (x : α × β).2) atTop (𝓝 b) :=
tendsto_atTop_isLUB (monotone_snd.restrict s) h.2
convert A.prod_mk_nhds B
-- Porting note: previously required below to close
-- ext1 ⟨⟨x, y⟩, h⟩
-- rfl
instance [Preorder α] [Preorder β] [TopologicalSpace α] [TopologicalSpace β] [InfConvergenceClass α]
[InfConvergenceClass β] : InfConvergenceClass (α × β) :=
show InfConvergenceClass (αᵒᵈ × βᵒᵈ)ᵒᵈ from OrderDual.infConvergenceClass
instance Pi.supConvergenceClass
{ι : Type*} {α : ι → Type*} [∀ i, Preorder (α i)] [∀ i, TopologicalSpace (α i)]
[∀ i, SupConvergenceClass (α i)] : SupConvergenceClass (∀ i, α i) := by
refine ⟨fun f s h => ?_⟩
simp only [isLUB_pi, ← range_restrict] at h
exact tendsto_pi_nhds.2 fun i => tendsto_atTop_isLUB ((monotone_eval _).restrict _) (h i)
instance Pi.infConvergenceClass
{ι : Type*} {α : ι → Type*} [∀ i, Preorder (α i)] [∀ i, TopologicalSpace (α i)]
[∀ i, InfConvergenceClass (α i)] : InfConvergenceClass (∀ i, α i) :=
show InfConvergenceClass (∀ i, (α i)ᵒᵈ)ᵒᵈ from OrderDual.infConvergenceClass
instance Pi.supConvergenceClass' {ι : Type*} [Preorder α] [TopologicalSpace α]
[SupConvergenceClass α] : SupConvergenceClass (ι → α) :=
supConvergenceClass
#align pi.Sup_convergence_class' Pi.supConvergenceClass'
instance Pi.infConvergenceClass' {ι : Type*} [Preorder α] [TopologicalSpace α]
[InfConvergenceClass α] : InfConvergenceClass (ι → α) :=
Pi.infConvergenceClass
#align pi.Inf_convergence_class' Pi.infConvergenceClass'
theorem tendsto_of_monotone {ι α : Type*} [Preorder ι] [TopologicalSpace α]
[ConditionallyCompleteLinearOrder α] [OrderTopology α] {f : ι → α} (h_mono : Monotone f) :
Tendsto f atTop atTop ∨ ∃ l, Tendsto f atTop (𝓝 l) :=
if H : BddAbove (range f) then Or.inr ⟨_, tendsto_atTop_ciSup h_mono H⟩
else Or.inl <| tendsto_atTop_atTop_of_monotone' h_mono H
#align tendsto_of_monotone tendsto_of_monotone
theorem tendsto_of_antitone {ι α : Type*} [Preorder ι] [TopologicalSpace α]
[ConditionallyCompleteLinearOrder α] [OrderTopology α] {f : ι → α} (h_mono : Antitone f) :
Tendsto f atTop atBot ∨ ∃ l, Tendsto f atTop (𝓝 l) :=
@tendsto_of_monotone ι αᵒᵈ _ _ _ _ _ h_mono
#align tendsto_of_antitone tendsto_of_antitone
| Mathlib/Topology/Order/MonotoneConvergence.lean | 237 | 245 | theorem tendsto_iff_tendsto_subseq_of_monotone {ι₁ ι₂ α : Type*} [SemilatticeSup ι₁] [Preorder ι₂]
[Nonempty ι₁] [TopologicalSpace α] [ConditionallyCompleteLinearOrder α] [OrderTopology α]
[NoMaxOrder α] {f : ι₂ → α} {φ : ι₁ → ι₂} {l : α} (hf : Monotone f)
(hg : Tendsto φ atTop atTop) : Tendsto f atTop (𝓝 l) ↔ Tendsto (f ∘ φ) atTop (𝓝 l) := by |
constructor <;> intro h
· exact h.comp hg
· rcases tendsto_of_monotone hf with (h' | ⟨l', hl'⟩)
· exact (not_tendsto_atTop_of_tendsto_nhds h (h'.comp hg)).elim
· rwa [tendsto_nhds_unique h (hl'.comp hg)]
|
/-
Copyright (c) 2021 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov
-/
import Mathlib.Analysis.BoxIntegral.Partition.SubboxInduction
import Mathlib.Analysis.BoxIntegral.Partition.Split
#align_import analysis.box_integral.partition.filter from "leanprover-community/mathlib"@"92ca63f0fb391a9ca5f22d2409a6080e786d99f7"
/-!
# Filters used in box-based integrals
First we define a structure `BoxIntegral.IntegrationParams`. This structure will be used as an
argument in the definition of `BoxIntegral.integral` in order to use the same definition for a few
well-known definitions of integrals based on partitions of a rectangular box into subboxes (Riemann
integral, Henstock-Kurzweil integral, and McShane integral).
This structure holds three boolean values (see below), and encodes eight different sets of
parameters; only four of these values are used somewhere in `mathlib4`. Three of them correspond to
the integration theories listed above, and one is a generalization of the one-dimensional
Henstock-Kurzweil integral such that the divergence theorem works without additional integrability
assumptions.
Finally, for each set of parameters `l : BoxIntegral.IntegrationParams` and a rectangular box
`I : BoxIntegral.Box ι`, we define several `Filter`s that will be used either in the definition of
the corresponding integral, or in the proofs of its properties. We equip
`BoxIntegral.IntegrationParams` with a `BoundedOrder` structure such that larger
`IntegrationParams` produce larger filters.
## Main definitions
### Integration parameters
The structure `BoxIntegral.IntegrationParams` has 3 boolean fields with the following meaning:
* `bRiemann`: the value `true` means that the filter corresponds to a Riemann-style integral, i.e.
in the definition of integrability we require a constant upper estimate `r` on the size of boxes
of a tagged partition; the value `false` means that the estimate may depend on the position of the
tag.
* `bHenstock`: the value `true` means that we require that each tag belongs to its own closed box;
the value `false` means that we only require that tags belong to the ambient box.
* `bDistortion`: the value `true` means that `r` can depend on the maximal ratio of sides of the
same box of a partition. Presence of this case make quite a few proofs harder but we can prove the
divergence theorem only for the filter `BoxIntegral.IntegrationParams.GP = ⊥ =
{bRiemann := false, bHenstock := true, bDistortion := true}`.
### Well-known sets of parameters
Out of eight possible values of `BoxIntegral.IntegrationParams`, the following four are used in
the library.
* `BoxIntegral.IntegrationParams.Riemann` (`bRiemann = true`, `bHenstock = true`,
`bDistortion = false`): this value corresponds to the Riemann integral; in the corresponding
filter, we require that the diameters of all boxes `J` of a tagged partition are bounded from
above by a constant upper estimate that may not depend on the geometry of `J`, and each tag
belongs to the corresponding closed box.
* `BoxIntegral.IntegrationParams.Henstock` (`bRiemann = false`, `bHenstock = true`,
`bDistortion = false`): this value corresponds to the most natural generalization of
Henstock-Kurzweil integral to higher dimension; the only (but important!) difference between this
theory and Riemann integral is that instead of a constant upper estimate on the size of all boxes
of a partition, we require that the partition is *subordinate* to a possibly discontinuous
function `r : (ι → ℝ) → {x : ℝ | 0 < x}`, i.e. each box `J` is included in a closed ball with
center `π.tag J` and radius `r J`.
* `BoxIntegral.IntegrationParams.McShane` (`bRiemann = false`, `bHenstock = false`,
`bDistortion = false`): this value corresponds to the McShane integral; the only difference with
the Henstock integral is that we allow tags to be outside of their boxes; the tags still have to
be in the ambient closed box, and the partition still has to be subordinate to a function.
* `BoxIntegral.IntegrationParams.GP = ⊥` (`bRiemann = false`, `bHenstock = true`,
`bDistortion = true`): this is the least integration theory in our list, i.e., all functions
integrable in any other theory is integrable in this one as well. This is a non-standard
generalization of the Henstock-Kurzweil integral to higher dimension. In dimension one, it
generates the same filter as `Henstock`. In higher dimension, this generalization defines an
integration theory such that the divergence of any Fréchet differentiable function `f` is
integrable, and its integral is equal to the sum of integrals of `f` over the faces of the box,
taken with appropriate signs.
A function `f` is `GP`-integrable if for any `ε > 0` and `c : ℝ≥0` there exists
`r : (ι → ℝ) → {x : ℝ | 0 < x}` such that for any tagged partition `π` subordinate to `r`, if each
tag belongs to the corresponding closed box and for each box `J ∈ π`, the maximal ratio of its
sides is less than or equal to `c`, then the integral sum of `f` over `π` is `ε`-close to the
integral.
### Filters and predicates on `TaggedPrepartition I`
For each value of `IntegrationParams` and a rectangular box `I`, we define a few filters on
`TaggedPrepartition I`. First, we define a predicate
```
structure BoxIntegral.IntegrationParams.MemBaseSet (l : BoxIntegral.IntegrationParams)
(I : BoxIntegral.Box ι) (c : ℝ≥0) (r : (ι → ℝ) → Ioi (0 : ℝ))
(π : BoxIntegral.TaggedPrepartition I) : Prop where
```
This predicate says that
* if `l.bHenstock`, then `π` is a Henstock prepartition, i.e. each tag belongs to the corresponding
closed box;
* `π` is subordinate to `r`;
* if `l.bDistortion`, then the distortion of each box in `π` is less than or equal to `c`;
* if `l.bDistortion`, then there exists a prepartition `π'` with distortion `≤ c` that covers
exactly `I \ π.iUnion`.
The last condition is always true for `c > 1`, see TODO section for more details.
Then we define a predicate `BoxIntegral.IntegrationParams.RCond` on functions
`r : (ι → ℝ) → {x : ℝ | 0 < x}`. If `l.bRiemann`, then this predicate requires `r` to be a constant
function, otherwise it imposes no restrictions on `r`. We introduce this definition to prove a few
dot-notation lemmas: e.g., `BoxIntegral.IntegrationParams.RCond.min` says that the pointwise
minimum of two functions that satisfy this condition satisfies this condition as well.
Then we define four filters on `BoxIntegral.TaggedPrepartition I`.
* `BoxIntegral.IntegrationParams.toFilterDistortion`: an auxiliary filter that takes parameters
`(l : BoxIntegral.IntegrationParams) (I : BoxIntegral.Box ι) (c : ℝ≥0)` and returns the
filter generated by all sets `{π | MemBaseSet l I c r π}`, where `r` is a function satisfying
the predicate `BoxIntegral.IntegrationParams.RCond l`;
* `BoxIntegral.IntegrationParams.toFilter l I`: the supremum of `l.toFilterDistortion I c`
over all `c : ℝ≥0`;
* `BoxIntegral.IntegrationParams.toFilterDistortioniUnion l I c π₀`, where `π₀` is a
prepartition of `I`: the infimum of `l.toFilterDistortion I c` and the principal filter
generated by `{π | π.iUnion = π₀.iUnion}`;
* `BoxIntegral.IntegrationParams.toFilteriUnion l I π₀`: the supremum of
`l.toFilterDistortioniUnion l I c π₀` over all `c : ℝ≥0`. This is the filter (in the case
`π₀ = ⊤` is the one-box partition of `I`) used in the definition of the integral of a function
over a box.
## Implementation details
* Later we define the integral of a function over a rectangular box as the limit (if it exists) of
the integral sums along `BoxIntegral.IntegrationParams.toFilteriUnion l I ⊤`. While it is
possible to define the integral with a general filter on `BoxIntegral.TaggedPrepartition I` as a
parameter, many lemmas (e.g., Sacks-Henstock lemma and most results about integrability of
functions) require the filter to have a predictable structure. So, instead of adding assumptions
about the filter here and there, we define this auxiliary type that can encode all integration
theories we need in practice.
* While the definition of the integral only uses the filter
`BoxIntegral.IntegrationParams.toFilteriUnion l I ⊤` and partitions of a box, some lemmas
(e.g., the Henstock-Sacks lemmas) are best formulated in terms of the predicate `MemBaseSet` and
other filters defined above.
* We use `Bool` instead of `Prop` for the fields of `IntegrationParams` in order to have decidable
equality and inequalities.
## TODO
Currently, `BoxIntegral.IntegrationParams.MemBaseSet` explicitly requires that there exists a
partition of the complement `I \ π.iUnion` with distortion `≤ c`. For `c > 1`, this condition is
always true but the proof of this fact requires more API about
`BoxIntegral.Prepartition.splitMany`. We should formalize this fact, then either require `c > 1`
everywhere, or replace `≤ c` with `< c` so that we automatically get `c > 1` for a non-trivial
prepartition (and consider the special case `π = ⊥` separately if needed).
## Tags
integral, rectangular box, partition, filter
-/
open Set Function Filter Metric Finset Bool
open scoped Classical
open Topology Filter NNReal
noncomputable section
namespace BoxIntegral
variable {ι : Type*} [Fintype ι] {I J : Box ι} {c c₁ c₂ : ℝ≥0} {r r₁ r₂ : (ι → ℝ) → Ioi (0 : ℝ)}
{π π₁ π₂ : TaggedPrepartition I}
open TaggedPrepartition
/-- An `IntegrationParams` is a structure holding 3 boolean values used to define a filter to be
used in the definition of a box-integrable function.
* `bRiemann`: the value `true` means that the filter corresponds to a Riemann-style integral, i.e.
in the definition of integrability we require a constant upper estimate `r` on the size of boxes
of a tagged partition; the value `false` means that the estimate may depend on the position of the
tag.
* `bHenstock`: the value `true` means that we require that each tag belongs to its own closed box;
the value `false` means that we only require that tags belong to the ambient box.
* `bDistortion`: the value `true` means that `r` can depend on the maximal ratio of sides of the
same box of a partition. Presence of this case makes quite a few proofs harder but we can prove
the divergence theorem only for the filter `BoxIntegral.IntegrationParams.GP = ⊥ =
{bRiemann := false, bHenstock := true, bDistortion := true}`.
-/
@[ext]
structure IntegrationParams : Type where
(bRiemann bHenstock bDistortion : Bool)
#align box_integral.integration_params BoxIntegral.IntegrationParams
variable {l l₁ l₂ : IntegrationParams}
namespace IntegrationParams
/-- Auxiliary equivalence with a product type used to lift an order. -/
def equivProd : IntegrationParams ≃ Bool × Boolᵒᵈ × Boolᵒᵈ where
toFun l := ⟨l.1, OrderDual.toDual l.2, OrderDual.toDual l.3⟩
invFun l := ⟨l.1, OrderDual.ofDual l.2.1, OrderDual.ofDual l.2.2⟩
left_inv _ := rfl
right_inv _ := rfl
#align box_integral.integration_params.equiv_prod BoxIntegral.IntegrationParams.equivProd
instance : PartialOrder IntegrationParams :=
PartialOrder.lift equivProd equivProd.injective
/-- Auxiliary `OrderIso` with a product type used to lift a `BoundedOrder` structure. -/
def isoProd : IntegrationParams ≃o Bool × Boolᵒᵈ × Boolᵒᵈ :=
⟨equivProd, Iff.rfl⟩
#align box_integral.integration_params.iso_prod BoxIntegral.IntegrationParams.isoProd
instance : BoundedOrder IntegrationParams :=
isoProd.symm.toGaloisInsertion.liftBoundedOrder
/-- The value `BoxIntegral.IntegrationParams.GP = ⊥`
(`bRiemann = false`, `bHenstock = true`, `bDistortion = true`)
corresponds to a generalization of the Henstock integral such that the Divergence theorem holds true
without additional integrability assumptions, see the module docstring for details. -/
instance : Inhabited IntegrationParams :=
⟨⊥⟩
instance : DecidableRel ((· ≤ ·) : IntegrationParams → IntegrationParams → Prop) :=
fun _ _ => And.decidable
instance : DecidableEq IntegrationParams :=
fun x y => decidable_of_iff _ (IntegrationParams.ext_iff x y).symm
/-- The `BoxIntegral.IntegrationParams` corresponding to the Riemann integral. In the
corresponding filter, we require that the diameters of all boxes `J` of a tagged partition are
bounded from above by a constant upper estimate that may not depend on the geometry of `J`, and each
tag belongs to the corresponding closed box. -/
def Riemann : IntegrationParams where
bRiemann := true
bHenstock := true
bDistortion := false
set_option linter.uppercaseLean3 false in
#align box_integral.integration_params.Riemann BoxIntegral.IntegrationParams.Riemann
/-- The `BoxIntegral.IntegrationParams` corresponding to the Henstock-Kurzweil integral. In the
corresponding filter, we require that the tagged partition is subordinate to a (possibly,
discontinuous) positive function `r` and each tag belongs to the corresponding closed box. -/
def Henstock : IntegrationParams :=
⟨false, true, false⟩
set_option linter.uppercaseLean3 false in
#align box_integral.integration_params.Henstock BoxIntegral.IntegrationParams.Henstock
/-- The `BoxIntegral.IntegrationParams` corresponding to the McShane integral. In the
corresponding filter, we require that the tagged partition is subordinate to a (possibly,
discontinuous) positive function `r`; the tags may be outside of the corresponding closed box
(but still inside the ambient closed box `I.Icc`). -/
def McShane : IntegrationParams :=
⟨false, false, false⟩
set_option linter.uppercaseLean3 false in
#align box_integral.integration_params.McShane BoxIntegral.IntegrationParams.McShane
/-- The `BoxIntegral.IntegrationParams` corresponding to the generalized Perron integral. In the
corresponding filter, we require that the tagged partition is subordinate to a (possibly,
discontinuous) positive function `r` and each tag belongs to the corresponding closed box. We also
require an upper estimate on the distortion of all boxes of the partition. -/
def GP : IntegrationParams := ⊥
set_option linter.uppercaseLean3 false in
#align box_integral.integration_params.GP BoxIntegral.IntegrationParams.GP
theorem henstock_le_riemann : Henstock ≤ Riemann := by trivial
set_option linter.uppercaseLean3 false in
#align box_integral.integration_params.Henstock_le_Riemann BoxIntegral.IntegrationParams.henstock_le_riemann
theorem henstock_le_mcShane : Henstock ≤ McShane := by trivial
set_option linter.uppercaseLean3 false in
#align box_integral.integration_params.Henstock_le_McShane BoxIntegral.IntegrationParams.henstock_le_mcShane
theorem gp_le : GP ≤ l :=
bot_le
set_option linter.uppercaseLean3 false in
#align box_integral.integration_params.GP_le BoxIntegral.IntegrationParams.gp_le
/-- The predicate corresponding to a base set of the filter defined by an
`IntegrationParams`. It says that
* if `l.bHenstock`, then `π` is a Henstock prepartition, i.e. each tag belongs to the corresponding
closed box;
* `π` is subordinate to `r`;
* if `l.bDistortion`, then the distortion of each box in `π` is less than or equal to `c`;
* if `l.bDistortion`, then there exists a prepartition `π'` with distortion `≤ c` that covers
exactly `I \ π.iUnion`.
The last condition is automatically verified for partitions, and is used in the proof of the
Sacks-Henstock inequality to compare two prepartitions covering the same part of the box.
It is also automatically satisfied for any `c > 1`, see TODO section of the module docstring for
details. -/
structure MemBaseSet (l : IntegrationParams) (I : Box ι) (c : ℝ≥0) (r : (ι → ℝ) → Ioi (0 : ℝ))
(π : TaggedPrepartition I) : Prop where
protected isSubordinate : π.IsSubordinate r
protected isHenstock : l.bHenstock → π.IsHenstock
protected distortion_le : l.bDistortion → π.distortion ≤ c
protected exists_compl : l.bDistortion → ∃ π' : Prepartition I,
π'.iUnion = ↑I \ π.iUnion ∧ π'.distortion ≤ c
#align box_integral.integration_params.mem_base_set BoxIntegral.IntegrationParams.MemBaseSet
/-- A predicate saying that in case `l.bRiemann = true`, the function `r` is a constant. -/
def RCond {ι : Type*} (l : IntegrationParams) (r : (ι → ℝ) → Ioi (0 : ℝ)) : Prop :=
l.bRiemann → ∀ x, r x = r 0
#align box_integral.integration_params.r_cond BoxIntegral.IntegrationParams.RCond
/-- A set `s : Set (TaggedPrepartition I)` belongs to `l.toFilterDistortion I c` if there exists
a function `r : ℝⁿ → (0, ∞)` (or a constant `r` if `l.bRiemann = true`) such that `s` contains each
prepartition `π` such that `l.MemBaseSet I c r π`. -/
def toFilterDistortion (l : IntegrationParams) (I : Box ι) (c : ℝ≥0) :
Filter (TaggedPrepartition I) :=
⨅ (r : (ι → ℝ) → Ioi (0 : ℝ)) (_ : l.RCond r), 𝓟 { π | l.MemBaseSet I c r π }
#align box_integral.integration_params.to_filter_distortion BoxIntegral.IntegrationParams.toFilterDistortion
/-- A set `s : Set (TaggedPrepartition I)` belongs to `l.toFilter I` if for any `c : ℝ≥0` there
exists a function `r : ℝⁿ → (0, ∞)` (or a constant `r` if `l.bRiemann = true`) such that
`s` contains each prepartition `π` such that `l.MemBaseSet I c r π`. -/
def toFilter (l : IntegrationParams) (I : Box ι) : Filter (TaggedPrepartition I) :=
⨆ c : ℝ≥0, l.toFilterDistortion I c
#align box_integral.integration_params.to_filter BoxIntegral.IntegrationParams.toFilter
/-- A set `s : Set (TaggedPrepartition I)` belongs to `l.toFilterDistortioniUnion I c π₀` if
there exists a function `r : ℝⁿ → (0, ∞)` (or a constant `r` if `l.bRiemann = true`) such that `s`
contains each prepartition `π` such that `l.MemBaseSet I c r π` and `π.iUnion = π₀.iUnion`. -/
def toFilterDistortioniUnion (l : IntegrationParams) (I : Box ι) (c : ℝ≥0) (π₀ : Prepartition I) :=
l.toFilterDistortion I c ⊓ 𝓟 { π | π.iUnion = π₀.iUnion }
#align box_integral.integration_params.to_filter_distortion_Union BoxIntegral.IntegrationParams.toFilterDistortioniUnion
/-- A set `s : Set (TaggedPrepartition I)` belongs to `l.toFilteriUnion I π₀` if for any `c : ℝ≥0`
there exists a function `r : ℝⁿ → (0, ∞)` (or a constant `r` if `l.bRiemann = true`) such that `s`
contains each prepartition `π` such that `l.MemBaseSet I c r π` and `π.iUnion = π₀.iUnion`. -/
def toFilteriUnion (l : IntegrationParams) (I : Box ι) (π₀ : Prepartition I) :=
⨆ c : ℝ≥0, l.toFilterDistortioniUnion I c π₀
#align box_integral.integration_params.to_filter_Union BoxIntegral.IntegrationParams.toFilteriUnion
theorem rCond_of_bRiemann_eq_false {ι} (l : IntegrationParams) (hl : l.bRiemann = false)
{r : (ι → ℝ) → Ioi (0 : ℝ)} : l.RCond r := by
simp [RCond, hl]
set_option linter.uppercaseLean3 false in
#align box_integral.integration_params.r_cond_of_bRiemann_eq_ff BoxIntegral.IntegrationParams.rCond_of_bRiemann_eq_false
theorem toFilter_inf_iUnion_eq (l : IntegrationParams) (I : Box ι) (π₀ : Prepartition I) :
l.toFilter I ⊓ 𝓟 { π | π.iUnion = π₀.iUnion } = l.toFilteriUnion I π₀ :=
(iSup_inf_principal _ _).symm
#align box_integral.integration_params.to_filter_inf_Union_eq BoxIntegral.IntegrationParams.toFilter_inf_iUnion_eq
theorem MemBaseSet.mono' (I : Box ι) (h : l₁ ≤ l₂) (hc : c₁ ≤ c₂) {π : TaggedPrepartition I}
(hr : ∀ J ∈ π, r₁ (π.tag J) ≤ r₂ (π.tag J)) (hπ : l₁.MemBaseSet I c₁ r₁ π) :
l₂.MemBaseSet I c₂ r₂ π :=
⟨hπ.1.mono' hr, fun h₂ => hπ.2 (le_iff_imp.1 h.2.1 h₂),
fun hD => (hπ.3 (le_iff_imp.1 h.2.2 hD)).trans hc,
fun hD => (hπ.4 (le_iff_imp.1 h.2.2 hD)).imp fun _ hπ => ⟨hπ.1, hπ.2.trans hc⟩⟩
#align box_integral.integration_params.mem_base_set.mono' BoxIntegral.IntegrationParams.MemBaseSet.mono'
@[mono]
theorem MemBaseSet.mono (I : Box ι) (h : l₁ ≤ l₂) (hc : c₁ ≤ c₂) {π : TaggedPrepartition I}
(hr : ∀ x ∈ Box.Icc I, r₁ x ≤ r₂ x) (hπ : l₁.MemBaseSet I c₁ r₁ π) : l₂.MemBaseSet I c₂ r₂ π :=
hπ.mono' I h hc fun J _ => hr _ <| π.tag_mem_Icc J
#align box_integral.integration_params.mem_base_set.mono BoxIntegral.IntegrationParams.MemBaseSet.mono
theorem MemBaseSet.exists_common_compl (h₁ : l.MemBaseSet I c₁ r₁ π₁) (h₂ : l.MemBaseSet I c₂ r₂ π₂)
(hU : π₁.iUnion = π₂.iUnion) :
∃ π : Prepartition I, π.iUnion = ↑I \ π₁.iUnion ∧
(l.bDistortion → π.distortion ≤ c₁) ∧ (l.bDistortion → π.distortion ≤ c₂) := by
wlog hc : c₁ ≤ c₂ with H
· simpa [hU, _root_.and_comm] using
@H _ _ I J c c₂ c₁ r r₂ r₁ π π₂ π₁ _ l₂ l₁ h₂ h₁ hU.symm (le_of_not_le hc)
by_cases hD : (l.bDistortion : Prop)
· rcases h₁.4 hD with ⟨π, hπU, hπc⟩
exact ⟨π, hπU, fun _ => hπc, fun _ => hπc.trans hc⟩
· exact ⟨π₁.toPrepartition.compl, π₁.toPrepartition.iUnion_compl,
fun h => (hD h).elim, fun h => (hD h).elim⟩
#align box_integral.integration_params.mem_base_set.exists_common_compl BoxIntegral.IntegrationParams.MemBaseSet.exists_common_compl
protected theorem MemBaseSet.unionComplToSubordinate (hπ₁ : l.MemBaseSet I c r₁ π₁)
(hle : ∀ x ∈ Box.Icc I, r₂ x ≤ r₁ x) {π₂ : Prepartition I} (hU : π₂.iUnion = ↑I \ π₁.iUnion)
(hc : l.bDistortion → π₂.distortion ≤ c) :
l.MemBaseSet I c r₁ (π₁.unionComplToSubordinate π₂ hU r₂) :=
⟨hπ₁.1.disjUnion ((π₂.isSubordinate_toSubordinate r₂).mono hle) _,
fun h => (hπ₁.2 h).disjUnion (π₂.isHenstock_toSubordinate _) _,
fun h => (distortion_unionComplToSubordinate _ _ _ _).trans_le (max_le (hπ₁.3 h) (hc h)),
fun _ => ⟨⊥, by simp⟩⟩
#align box_integral.integration_params.mem_base_set.union_compl_to_subordinate BoxIntegral.IntegrationParams.MemBaseSet.unionComplToSubordinate
protected theorem MemBaseSet.filter (hπ : l.MemBaseSet I c r π) (p : Box ι → Prop) :
l.MemBaseSet I c r (π.filter p) := by
refine ⟨fun J hJ => hπ.1 J (π.mem_filter.1 hJ).1, fun hH J hJ => hπ.2 hH J (π.mem_filter.1 hJ).1,
fun hD => (distortion_filter_le _ _).trans (hπ.3 hD), fun hD => ?_⟩
rcases hπ.4 hD with ⟨π₁, hπ₁U, hc⟩
set π₂ := π.filter fun J => ¬p J
have : Disjoint π₁.iUnion π₂.iUnion := by
simpa [π₂, hπ₁U] using disjoint_sdiff_self_left.mono_right sdiff_le
refine ⟨π₁.disjUnion π₂.toPrepartition this, ?_, ?_⟩
· suffices ↑I \ π.iUnion ∪ π.iUnion \ (π.filter p).iUnion = ↑I \ (π.filter p).iUnion by
simp [π₂, *]
have h : (π.filter p).iUnion ⊆ π.iUnion :=
biUnion_subset_biUnion_left (Finset.filter_subset _ _)
ext x
fconstructor
· rintro (⟨hxI, hxπ⟩ | ⟨hxπ, hxp⟩)
exacts [⟨hxI, mt (@h x) hxπ⟩, ⟨π.iUnion_subset hxπ, hxp⟩]
· rintro ⟨hxI, hxp⟩
by_cases hxπ : x ∈ π.iUnion
exacts [Or.inr ⟨hxπ, hxp⟩, Or.inl ⟨hxI, hxπ⟩]
· have : (π.filter fun J => ¬p J).distortion ≤ c := (distortion_filter_le _ _).trans (hπ.3 hD)
simpa [hc]
#align box_integral.integration_params.mem_base_set.filter BoxIntegral.IntegrationParams.MemBaseSet.filter
theorem biUnionTagged_memBaseSet {π : Prepartition I} {πi : ∀ J, TaggedPrepartition J}
(h : ∀ J ∈ π, l.MemBaseSet J c r (πi J)) (hp : ∀ J ∈ π, (πi J).IsPartition)
(hc : l.bDistortion → π.compl.distortion ≤ c) : l.MemBaseSet I c r (π.biUnionTagged πi) := by
refine ⟨TaggedPrepartition.isSubordinate_biUnionTagged.2 fun J hJ => (h J hJ).1,
fun hH => TaggedPrepartition.isHenstock_biUnionTagged.2 fun J hJ => (h J hJ).2 hH,
fun hD => ?_, fun hD => ?_⟩
· rw [Prepartition.distortion_biUnionTagged, Finset.sup_le_iff]
exact fun J hJ => (h J hJ).3 hD
· refine ⟨_, ?_, hc hD⟩
rw [π.iUnion_compl, ← π.iUnion_biUnion_partition hp]
rfl
#align box_integral.integration_params.bUnion_tagged_mem_base_set BoxIntegral.IntegrationParams.biUnionTagged_memBaseSet
@[mono]
theorem RCond.mono {ι : Type*} {r : (ι → ℝ) → Ioi (0 : ℝ)} (h : l₁ ≤ l₂) (hr : l₂.RCond r) :
l₁.RCond r :=
fun hR => hr (le_iff_imp.1 h.1 hR)
#align box_integral.integration_params.r_cond.mono BoxIntegral.IntegrationParams.RCond.mono
nonrec theorem RCond.min {ι : Type*} {r₁ r₂ : (ι → ℝ) → Ioi (0 : ℝ)} (h₁ : l.RCond r₁)
(h₂ : l.RCond r₂) : l.RCond fun x => min (r₁ x) (r₂ x) :=
fun hR x => congr_arg₂ min (h₁ hR x) (h₂ hR x)
#align box_integral.integration_params.r_cond.min BoxIntegral.IntegrationParams.RCond.min
@[mono]
theorem toFilterDistortion_mono (I : Box ι) (h : l₁ ≤ l₂) (hc : c₁ ≤ c₂) :
l₁.toFilterDistortion I c₁ ≤ l₂.toFilterDistortion I c₂ :=
iInf_mono fun _ =>
iInf_mono' fun hr =>
⟨hr.mono h, principal_mono.2 fun _ => MemBaseSet.mono I h hc fun _ _ => le_rfl⟩
#align box_integral.integration_params.to_filter_distortion_mono BoxIntegral.IntegrationParams.toFilterDistortion_mono
@[mono]
theorem toFilter_mono (I : Box ι) {l₁ l₂ : IntegrationParams} (h : l₁ ≤ l₂) :
l₁.toFilter I ≤ l₂.toFilter I :=
iSup_mono fun _ => toFilterDistortion_mono I h le_rfl
#align box_integral.integration_params.to_filter_mono BoxIntegral.IntegrationParams.toFilter_mono
@[mono]
theorem toFilteriUnion_mono (I : Box ι) {l₁ l₂ : IntegrationParams} (h : l₁ ≤ l₂)
(π₀ : Prepartition I) : l₁.toFilteriUnion I π₀ ≤ l₂.toFilteriUnion I π₀ :=
iSup_mono fun _ => inf_le_inf_right _ <| toFilterDistortion_mono _ h le_rfl
#align box_integral.integration_params.to_filter_Union_mono BoxIntegral.IntegrationParams.toFilteriUnion_mono
theorem toFilteriUnion_congr (I : Box ι) (l : IntegrationParams) {π₁ π₂ : Prepartition I}
(h : π₁.iUnion = π₂.iUnion) : l.toFilteriUnion I π₁ = l.toFilteriUnion I π₂ := by
simp only [toFilteriUnion, toFilterDistortioniUnion, h]
#align box_integral.integration_params.to_filter_Union_congr BoxIntegral.IntegrationParams.toFilteriUnion_congr
theorem hasBasis_toFilterDistortion (l : IntegrationParams) (I : Box ι) (c : ℝ≥0) :
(l.toFilterDistortion I c).HasBasis l.RCond fun r => { π | l.MemBaseSet I c r π } :=
hasBasis_biInf_principal'
(fun _ hr₁ _ hr₂ =>
⟨_, hr₁.min hr₂, fun _ => MemBaseSet.mono _ le_rfl le_rfl fun _ _ => min_le_left _ _,
fun _ => MemBaseSet.mono _ le_rfl le_rfl fun _ _ => min_le_right _ _⟩)
⟨fun _ => ⟨1, Set.mem_Ioi.2 zero_lt_one⟩, fun _ _ => rfl⟩
#align box_integral.integration_params.has_basis_to_filter_distortion BoxIntegral.IntegrationParams.hasBasis_toFilterDistortion
theorem hasBasis_toFilterDistortioniUnion (l : IntegrationParams) (I : Box ι) (c : ℝ≥0)
(π₀ : Prepartition I) :
(l.toFilterDistortioniUnion I c π₀).HasBasis l.RCond fun r =>
{ π | l.MemBaseSet I c r π ∧ π.iUnion = π₀.iUnion } :=
(l.hasBasis_toFilterDistortion I c).inf_principal _
#align box_integral.integration_params.has_basis_to_filter_distortion_Union BoxIntegral.IntegrationParams.hasBasis_toFilterDistortioniUnion
theorem hasBasis_toFilteriUnion (l : IntegrationParams) (I : Box ι) (π₀ : Prepartition I) :
(l.toFilteriUnion I π₀).HasBasis (fun r : ℝ≥0 → (ι → ℝ) → Ioi (0 : ℝ) => ∀ c, l.RCond (r c))
fun r => { π | ∃ c, l.MemBaseSet I c (r c) π ∧ π.iUnion = π₀.iUnion } := by
have := fun c => l.hasBasis_toFilterDistortioniUnion I c π₀
simpa only [setOf_and, setOf_exists] using hasBasis_iSup this
#align box_integral.integration_params.has_basis_to_filter_Union BoxIntegral.IntegrationParams.hasBasis_toFilteriUnion
theorem hasBasis_toFilteriUnion_top (l : IntegrationParams) (I : Box ι) :
(l.toFilteriUnion I ⊤).HasBasis (fun r : ℝ≥0 → (ι → ℝ) → Ioi (0 : ℝ) => ∀ c, l.RCond (r c))
fun r => { π | ∃ c, l.MemBaseSet I c (r c) π ∧ π.IsPartition } := by
simpa only [TaggedPrepartition.isPartition_iff_iUnion_eq, Prepartition.iUnion_top] using
l.hasBasis_toFilteriUnion I ⊤
#align box_integral.integration_params.has_basis_to_filter_Union_top BoxIntegral.IntegrationParams.hasBasis_toFilteriUnion_top
theorem hasBasis_toFilter (l : IntegrationParams) (I : Box ι) :
(l.toFilter I).HasBasis (fun r : ℝ≥0 → (ι → ℝ) → Ioi (0 : ℝ) => ∀ c, l.RCond (r c))
fun r => { π | ∃ c, l.MemBaseSet I c (r c) π } := by
simpa only [setOf_exists] using hasBasis_iSup (l.hasBasis_toFilterDistortion I)
#align box_integral.integration_params.has_basis_to_filter BoxIntegral.IntegrationParams.hasBasis_toFilter
theorem tendsto_embedBox_toFilteriUnion_top (l : IntegrationParams) (h : I ≤ J) :
Tendsto (TaggedPrepartition.embedBox I J h) (l.toFilteriUnion I ⊤)
(l.toFilteriUnion J (Prepartition.single J I h)) := by
simp only [toFilteriUnion, tendsto_iSup]; intro c
set π₀ := Prepartition.single J I h
refine le_iSup_of_le (max c π₀.compl.distortion) ?_
refine ((l.hasBasis_toFilterDistortioniUnion I c ⊤).tendsto_iff
(l.hasBasis_toFilterDistortioniUnion J _ _)).2 fun r hr => ?_
refine ⟨r, hr, fun π hπ => ?_⟩
rw [mem_setOf_eq, Prepartition.iUnion_top] at hπ
refine ⟨⟨hπ.1.1, hπ.1.2, fun hD => le_trans (hπ.1.3 hD) (le_max_left _ _), fun _ => ?_⟩, ?_⟩
· refine ⟨_, π₀.iUnion_compl.trans ?_, le_max_right _ _⟩
congr 1
exact (Prepartition.iUnion_single h).trans hπ.2.symm
· exact hπ.2.trans (Prepartition.iUnion_single _).symm
#align box_integral.integration_params.tendsto_embed_box_to_filter_Union_top BoxIntegral.IntegrationParams.tendsto_embedBox_toFilteriUnion_top
theorem exists_memBaseSet_le_iUnion_eq (l : IntegrationParams) (π₀ : Prepartition I)
(hc₁ : π₀.distortion ≤ c) (hc₂ : π₀.compl.distortion ≤ c) (r : (ι → ℝ) → Ioi (0 : ℝ)) :
∃ π, l.MemBaseSet I c r π ∧ π.toPrepartition ≤ π₀ ∧ π.iUnion = π₀.iUnion := by
rcases π₀.exists_tagged_le_isHenstock_isSubordinate_iUnion_eq r with ⟨π, hle, hH, hr, hd, hU⟩
refine ⟨π, ⟨hr, fun _ => hH, fun _ => hd.trans_le hc₁, fun _ => ⟨π₀.compl, ?_, hc₂⟩⟩, ⟨hle, hU⟩⟩
exact Prepartition.compl_congr hU ▸ π.toPrepartition.iUnion_compl
#align box_integral.integration_params.exists_mem_base_set_le_Union_eq BoxIntegral.IntegrationParams.exists_memBaseSet_le_iUnion_eq
| Mathlib/Analysis/BoxIntegral/Partition/Filter.lean | 530 | 534 | theorem exists_memBaseSet_isPartition (l : IntegrationParams) (I : Box ι) (hc : I.distortion ≤ c)
(r : (ι → ℝ) → Ioi (0 : ℝ)) : ∃ π, l.MemBaseSet I c r π ∧ π.IsPartition := by |
rw [← Prepartition.distortion_top] at hc
have hc' : (⊤ : Prepartition I).compl.distortion ≤ c := by simp
simpa [isPartition_iff_iUnion_eq] using l.exists_memBaseSet_le_iUnion_eq ⊤ hc hc' r
|
/-
Copyright (c) 2016 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad, Leonardo de Moura, Mario Carneiro, Johannes Hölzl
-/
import Mathlib.Algebra.Order.Monoid.Defs
import Mathlib.Algebra.Order.Sub.Defs
import Mathlib.Util.AssertExists
#align_import algebra.order.group.defs from "leanprover-community/mathlib"@"b599f4e4e5cf1fbcb4194503671d3d9e569c1fce"
/-!
# Ordered groups
This file develops the basics of ordered groups.
## Implementation details
Unfortunately, the number of `'` appended to lemmas in this file
may differ between the multiplicative and the additive version of a lemma.
The reason is that we did not want to change existing names in the library.
-/
open Function
universe u
variable {α : Type u}
/-- An ordered additive commutative group is an additive commutative group
with a partial order in which addition is strictly monotone. -/
class OrderedAddCommGroup (α : Type u) extends AddCommGroup α, PartialOrder α where
/-- Addition is monotone in an ordered additive commutative group. -/
protected add_le_add_left : ∀ a b : α, a ≤ b → ∀ c : α, c + a ≤ c + b
#align ordered_add_comm_group OrderedAddCommGroup
/-- An ordered commutative group is a commutative group
with a partial order in which multiplication is strictly monotone. -/
class OrderedCommGroup (α : Type u) extends CommGroup α, PartialOrder α where
/-- Multiplication is monotone in an ordered commutative group. -/
protected mul_le_mul_left : ∀ a b : α, a ≤ b → ∀ c : α, c * a ≤ c * b
#align ordered_comm_group OrderedCommGroup
attribute [to_additive] OrderedCommGroup
@[to_additive]
instance OrderedCommGroup.to_covariantClass_left_le (α : Type u) [OrderedCommGroup α] :
CovariantClass α α (· * ·) (· ≤ ·) where
elim a b c bc := OrderedCommGroup.mul_le_mul_left b c bc a
#align ordered_comm_group.to_covariant_class_left_le OrderedCommGroup.to_covariantClass_left_le
#align ordered_add_comm_group.to_covariant_class_left_le OrderedAddCommGroup.to_covariantClass_left_le
-- See note [lower instance priority]
@[to_additive OrderedAddCommGroup.toOrderedCancelAddCommMonoid]
instance (priority := 100) OrderedCommGroup.toOrderedCancelCommMonoid [OrderedCommGroup α] :
OrderedCancelCommMonoid α :=
{ ‹OrderedCommGroup α› with le_of_mul_le_mul_left := fun a b c ↦ le_of_mul_le_mul_left' }
#align ordered_comm_group.to_ordered_cancel_comm_monoid OrderedCommGroup.toOrderedCancelCommMonoid
#align ordered_add_comm_group.to_ordered_cancel_add_comm_monoid OrderedAddCommGroup.toOrderedCancelAddCommMonoid
example (α : Type u) [OrderedAddCommGroup α] : CovariantClass α α (swap (· + ·)) (· < ·) :=
IsRightCancelAdd.covariant_swap_add_lt_of_covariant_swap_add_le α
-- Porting note: this instance is not used,
-- and causes timeouts after lean4#2210.
-- It was introduced in https://github.com/leanprover-community/mathlib/pull/17564
-- but without the motivation clearly explained.
/-- A choice-free shortcut instance. -/
@[to_additive "A choice-free shortcut instance."]
theorem OrderedCommGroup.to_contravariantClass_left_le (α : Type u) [OrderedCommGroup α] :
ContravariantClass α α (· * ·) (· ≤ ·) where
elim a b c bc := by simpa using mul_le_mul_left' bc a⁻¹
#align ordered_comm_group.to_contravariant_class_left_le OrderedCommGroup.to_contravariantClass_left_le
#align ordered_add_comm_group.to_contravariant_class_left_le OrderedAddCommGroup.to_contravariantClass_left_le
-- Porting note: this instance is not used,
-- and causes timeouts after lean4#2210.
-- See further explanation on `OrderedCommGroup.to_contravariantClass_left_le`.
/-- A choice-free shortcut instance. -/
@[to_additive "A choice-free shortcut instance."]
theorem OrderedCommGroup.to_contravariantClass_right_le (α : Type u) [OrderedCommGroup α] :
ContravariantClass α α (swap (· * ·)) (· ≤ ·) where
elim a b c bc := by simpa using mul_le_mul_right' bc a⁻¹
#align ordered_comm_group.to_contravariant_class_right_le OrderedCommGroup.to_contravariantClass_right_le
#align ordered_add_comm_group.to_contravariant_class_right_le OrderedAddCommGroup.to_contravariantClass_right_le
section Group
variable [Group α]
section TypeclassesLeftLE
variable [LE α] [CovariantClass α α (· * ·) (· ≤ ·)] {a b c d : α}
/-- Uses `left` co(ntra)variant. -/
@[to_additive (attr := simp) "Uses `left` co(ntra)variant."]
theorem Left.inv_le_one_iff : a⁻¹ ≤ 1 ↔ 1 ≤ a := by
rw [← mul_le_mul_iff_left a]
simp
#align left.inv_le_one_iff Left.inv_le_one_iff
#align left.neg_nonpos_iff Left.neg_nonpos_iff
/-- Uses `left` co(ntra)variant. -/
@[to_additive (attr := simp) "Uses `left` co(ntra)variant."]
theorem Left.one_le_inv_iff : 1 ≤ a⁻¹ ↔ a ≤ 1 := by
rw [← mul_le_mul_iff_left a]
simp
#align left.one_le_inv_iff Left.one_le_inv_iff
#align left.nonneg_neg_iff Left.nonneg_neg_iff
@[to_additive (attr := simp)]
theorem le_inv_mul_iff_mul_le : b ≤ a⁻¹ * c ↔ a * b ≤ c := by
rw [← mul_le_mul_iff_left a]
simp
#align le_inv_mul_iff_mul_le le_inv_mul_iff_mul_le
#align le_neg_add_iff_add_le le_neg_add_iff_add_le
@[to_additive (attr := simp)]
| Mathlib/Algebra/Order/Group/Defs.lean | 120 | 121 | theorem inv_mul_le_iff_le_mul : b⁻¹ * a ≤ c ↔ a ≤ b * c := by |
rw [← mul_le_mul_iff_left b, mul_inv_cancel_left]
|
/-
Copyright (c) 2017 Mario Carneiro. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro, Yury G. Kudryashov
-/
import Batteries.Data.Sum.Basic
import Batteries.Logic
/-!
# Disjoint union of types
Theorems about the definitions introduced in `Batteries.Data.Sum.Basic`.
-/
open Function
namespace Sum
@[simp] protected theorem «forall» {p : α ⊕ β → Prop} :
(∀ x, p x) ↔ (∀ a, p (inl a)) ∧ ∀ b, p (inr b) :=
⟨fun h => ⟨fun _ => h _, fun _ => h _⟩, fun ⟨h₁, h₂⟩ => Sum.rec h₁ h₂⟩
@[simp] protected theorem «exists» {p : α ⊕ β → Prop} :
(∃ x, p x) ↔ (∃ a, p (inl a)) ∨ ∃ b, p (inr b) :=
⟨ fun
| ⟨inl a, h⟩ => Or.inl ⟨a, h⟩
| ⟨inr b, h⟩ => Or.inr ⟨b, h⟩,
fun
| Or.inl ⟨a, h⟩ => ⟨inl a, h⟩
| Or.inr ⟨b, h⟩ => ⟨inr b, h⟩⟩
theorem forall_sum {γ : α ⊕ β → Sort _} (p : (∀ ab, γ ab) → Prop) :
(∀ fab, p fab) ↔ (∀ fa fb, p (Sum.rec fa fb)) := by
refine ⟨fun h fa fb => h _, fun h fab => ?_⟩
have h1 : fab = Sum.rec (fun a => fab (Sum.inl a)) (fun b => fab (Sum.inr b)) := by
ext ab; cases ab <;> rfl
rw [h1]; exact h _ _
section get
@[simp] theorem inl_getLeft : ∀ (x : α ⊕ β) (h : x.isLeft), inl (x.getLeft h) = x
| inl _, _ => rfl
@[simp] theorem inr_getRight : ∀ (x : α ⊕ β) (h : x.isRight), inr (x.getRight h) = x
| inr _, _ => rfl
@[simp] theorem getLeft?_eq_none_iff {x : α ⊕ β} : x.getLeft? = none ↔ x.isRight := by
cases x <;> simp only [getLeft?, isRight, eq_self_iff_true]
@[simp] theorem getRight?_eq_none_iff {x : α ⊕ β} : x.getRight? = none ↔ x.isLeft := by
cases x <;> simp only [getRight?, isLeft, eq_self_iff_true]
theorem eq_left_getLeft_of_isLeft : ∀ {x : α ⊕ β} (h : x.isLeft), x = inl (x.getLeft h)
| inl _, _ => rfl
@[simp] theorem getLeft_eq_iff (h : x.isLeft) : x.getLeft h = a ↔ x = inl a := by
cases x <;> simp at h ⊢
theorem eq_right_getRight_of_isRight : ∀ {x : α ⊕ β} (h : x.isRight), x = inr (x.getRight h)
| inr _, _ => rfl
@[simp] theorem getRight_eq_iff (h : x.isRight) : x.getRight h = b ↔ x = inr b := by
cases x <;> simp at h ⊢
@[simp] theorem getLeft?_eq_some_iff : x.getLeft? = some a ↔ x = inl a := by
cases x <;> simp only [getLeft?, Option.some.injEq, inl.injEq]
@[simp] theorem getRight?_eq_some_iff : x.getRight? = some b ↔ x = inr b := by
cases x <;> simp only [getRight?, Option.some.injEq, inr.injEq]
@[simp] theorem bnot_isLeft (x : α ⊕ β) : !x.isLeft = x.isRight := by cases x <;> rfl
@[simp] theorem isLeft_eq_false {x : α ⊕ β} : x.isLeft = false ↔ x.isRight := by cases x <;> simp
theorem not_isLeft {x : α ⊕ β} : ¬x.isLeft ↔ x.isRight := by simp
@[simp] theorem bnot_isRight (x : α ⊕ β) : !x.isRight = x.isLeft := by cases x <;> rfl
@[simp] theorem isRight_eq_false {x : α ⊕ β} : x.isRight = false ↔ x.isLeft := by cases x <;> simp
| .lake/packages/batteries/Batteries/Data/Sum/Lemmas.lean | 81 | 81 | theorem not_isRight {x : α ⊕ β} : ¬x.isRight ↔ x.isLeft := by | simp
|
/-
Copyright (c) 2020 Oliver Nash. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Oliver Nash
-/
import Mathlib.Algebra.Lie.Matrix
import Mathlib.LinearAlgebra.Matrix.SesquilinearForm
import Mathlib.Tactic.NoncommRing
#align_import algebra.lie.skew_adjoint from "leanprover-community/mathlib"@"075b3f7d19b9da85a0b54b3e33055a74fc388dec"
/-!
# Lie algebras of skew-adjoint endomorphisms of a bilinear form
When a module carries a bilinear form, the Lie algebra of endomorphisms of the module contains a
distinguished Lie subalgebra: the skew-adjoint endomorphisms. Such subalgebras are important
because they provide a simple, explicit construction of the so-called classical Lie algebras.
This file defines the Lie subalgebra of skew-adjoint endomorphisms cut out by a bilinear form on
a module and proves some basic related results. It also provides the corresponding definitions and
results for the Lie algebra of square matrices.
## Main definitions
* `skewAdjointLieSubalgebra`
* `skewAdjointLieSubalgebraEquiv`
* `skewAdjointMatricesLieSubalgebra`
* `skewAdjointMatricesLieSubalgebraEquiv`
## Tags
lie algebra, skew-adjoint, bilinear form
-/
universe u v w w₁
section SkewAdjointEndomorphisms
open LinearMap (BilinForm)
variable {R : Type u} {M : Type v} [CommRing R] [AddCommGroup M] [Module R M]
variable (B : BilinForm R M)
-- Porting note: Changed `(f g)` to `{f g}` for convenience in `skewAdjointLieSubalgebra`
theorem LinearMap.BilinForm.isSkewAdjoint_bracket {f g : Module.End R M}
(hf : f ∈ B.skewAdjointSubmodule) (hg : g ∈ B.skewAdjointSubmodule) :
⁅f, g⁆ ∈ B.skewAdjointSubmodule := by
rw [mem_skewAdjointSubmodule] at *
have hfg : IsAdjointPair B B (f * g) (g * f) := by rw [← neg_mul_neg g f]; exact hf.mul hg
have hgf : IsAdjointPair B B (g * f) (f * g) := by rw [← neg_mul_neg f g]; exact hg.mul hf
change IsAdjointPair B B (f * g - g * f) (-(f * g - g * f)); rw [neg_sub]
exact hfg.sub hgf
#align bilin_form.is_skew_adjoint_bracket LinearMap.BilinForm.isSkewAdjoint_bracket
/-- Given an `R`-module `M`, equipped with a bilinear form, the skew-adjoint endomorphisms form a
Lie subalgebra of the Lie algebra of endomorphisms. -/
def skewAdjointLieSubalgebra : LieSubalgebra R (Module.End R M) :=
{ B.skewAdjointSubmodule with
lie_mem' := B.isSkewAdjoint_bracket }
#align skew_adjoint_lie_subalgebra skewAdjointLieSubalgebra
variable {N : Type w} [AddCommGroup N] [Module R N] (e : N ≃ₗ[R] M)
/-- An equivalence of modules with bilinear forms gives equivalence of Lie algebras of skew-adjoint
endomorphisms. -/
def skewAdjointLieSubalgebraEquiv :
skewAdjointLieSubalgebra (B.compl₁₂ (↑e : N →ₗ[R] M) ↑e) ≃ₗ⁅R⁆ skewAdjointLieSubalgebra B := by
apply LieEquiv.ofSubalgebras _ _ e.lieConj
ext f
simp only [LieSubalgebra.mem_coe, Submodule.mem_map_equiv, LieSubalgebra.mem_map_submodule,
LinearEquiv.coe_coe]
exact (LinearMap.isPairSelfAdjoint_equiv (B := -B) (F := B) e f).symm
#align skew_adjoint_lie_subalgebra_equiv skewAdjointLieSubalgebraEquiv
@[simp]
theorem skewAdjointLieSubalgebraEquiv_apply
(f : skewAdjointLieSubalgebra (B.compl₁₂ (Qₗ := N) (Qₗ' := N) ↑e ↑e)) :
↑(skewAdjointLieSubalgebraEquiv B e f) = e.lieConj f := by
simp [skewAdjointLieSubalgebraEquiv]
#align skew_adjoint_lie_subalgebra_equiv_apply skewAdjointLieSubalgebraEquiv_apply
@[simp]
theorem skewAdjointLieSubalgebraEquiv_symm_apply (f : skewAdjointLieSubalgebra B) :
↑((skewAdjointLieSubalgebraEquiv B e).symm f) = e.symm.lieConj f := by
simp [skewAdjointLieSubalgebraEquiv]
#align skew_adjoint_lie_subalgebra_equiv_symm_apply skewAdjointLieSubalgebraEquiv_symm_apply
end SkewAdjointEndomorphisms
section SkewAdjointMatrices
open scoped Matrix
variable {R : Type u} {n : Type w} [CommRing R] [DecidableEq n] [Fintype n]
variable (J : Matrix n n R)
theorem Matrix.lie_transpose (A B : Matrix n n R) : ⁅A, B⁆ᵀ = ⁅Bᵀ, Aᵀ⁆ :=
show (A * B - B * A)ᵀ = Bᵀ * Aᵀ - Aᵀ * Bᵀ by simp
#align matrix.lie_transpose Matrix.lie_transpose
-- Porting note: Changed `(A B)` to `{A B}` for convenience in `skewAdjointMatricesLieSubalgebra`
theorem Matrix.isSkewAdjoint_bracket {A B : Matrix n n R} (hA : A ∈ skewAdjointMatricesSubmodule J)
(hB : B ∈ skewAdjointMatricesSubmodule J) : ⁅A, B⁆ ∈ skewAdjointMatricesSubmodule J := by
simp only [mem_skewAdjointMatricesSubmodule] at *
change ⁅A, B⁆ᵀ * J = J * (-⁅A, B⁆)
change Aᵀ * J = J * (-A) at hA
change Bᵀ * J = J * (-B) at hB
rw [Matrix.lie_transpose, LieRing.of_associative_ring_bracket,
LieRing.of_associative_ring_bracket, sub_mul, mul_assoc, mul_assoc, hA, hB, ← mul_assoc,
← mul_assoc, hA, hB]
noncomm_ring
#align matrix.is_skew_adjoint_bracket Matrix.isSkewAdjoint_bracket
/-- The Lie subalgebra of skew-adjoint square matrices corresponding to a square matrix `J`. -/
def skewAdjointMatricesLieSubalgebra : LieSubalgebra R (Matrix n n R) :=
{ skewAdjointMatricesSubmodule J with
lie_mem' := J.isSkewAdjoint_bracket }
#align skew_adjoint_matrices_lie_subalgebra skewAdjointMatricesLieSubalgebra
@[simp]
theorem mem_skewAdjointMatricesLieSubalgebra (A : Matrix n n R) :
A ∈ skewAdjointMatricesLieSubalgebra J ↔ A ∈ skewAdjointMatricesSubmodule J :=
Iff.rfl
#align mem_skew_adjoint_matrices_lie_subalgebra mem_skewAdjointMatricesLieSubalgebra
/-- An invertible matrix `P` gives a Lie algebra equivalence between those endomorphisms that are
skew-adjoint with respect to a square matrix `J` and those with respect to `PᵀJP`. -/
def skewAdjointMatricesLieSubalgebraEquiv (P : Matrix n n R) (h : Invertible P) :
skewAdjointMatricesLieSubalgebra J ≃ₗ⁅R⁆ skewAdjointMatricesLieSubalgebra (Pᵀ * J * P) :=
LieEquiv.ofSubalgebras _ _ (P.lieConj h).symm <| by
ext A
suffices P.lieConj h A ∈ skewAdjointMatricesSubmodule J ↔
A ∈ skewAdjointMatricesSubmodule (Pᵀ * J * P) by
simp only [LieSubalgebra.mem_coe, Submodule.mem_map_equiv, LieSubalgebra.mem_map_submodule,
LinearEquiv.coe_coe]
exact this
simp [Matrix.IsSkewAdjoint, J.isAdjointPair_equiv _ _ P (isUnit_of_invertible P)]
#align skew_adjoint_matrices_lie_subalgebra_equiv skewAdjointMatricesLieSubalgebraEquiv
-- TODO(mathlib4#6607): fix elaboration so annotation on `A` isn't needed
theorem skewAdjointMatricesLieSubalgebraEquiv_apply (P : Matrix n n R) (h : Invertible P)
(A : skewAdjointMatricesLieSubalgebra J) :
↑(skewAdjointMatricesLieSubalgebraEquiv J P h A) = P⁻¹ * (A : Matrix n n R) * P := by
simp [skewAdjointMatricesLieSubalgebraEquiv]
#align skew_adjoint_matrices_lie_subalgebra_equiv_apply skewAdjointMatricesLieSubalgebraEquiv_apply
/-- An equivalence of matrix algebras commuting with the transpose endomorphisms restricts to an
equivalence of Lie algebras of skew-adjoint matrices. -/
def skewAdjointMatricesLieSubalgebraEquivTranspose {m : Type w} [DecidableEq m] [Fintype m]
(e : Matrix n n R ≃ₐ[R] Matrix m m R) (h : ∀ A, (e A)ᵀ = e Aᵀ) :
skewAdjointMatricesLieSubalgebra J ≃ₗ⁅R⁆ skewAdjointMatricesLieSubalgebra (e J) :=
LieEquiv.ofSubalgebras _ _ e.toLieEquiv <| by
ext A
suffices J.IsSkewAdjoint (e.symm A) ↔ (e J).IsSkewAdjoint A by
-- Porting note: Originally `simpa [this]`
simpa [- LieSubalgebra.mem_map, LieSubalgebra.mem_map_submodule]
simp only [Matrix.IsSkewAdjoint, Matrix.IsAdjointPair, ← h,
← Function.Injective.eq_iff e.injective, map_mul, AlgEquiv.apply_symm_apply, map_neg]
#align skew_adjoint_matrices_lie_subalgebra_equiv_transpose skewAdjointMatricesLieSubalgebraEquivTranspose
@[simp]
theorem skewAdjointMatricesLieSubalgebraEquivTranspose_apply {m : Type w} [DecidableEq m]
[Fintype m] (e : Matrix n n R ≃ₐ[R] Matrix m m R) (h : ∀ A, (e A)ᵀ = e Aᵀ)
(A : skewAdjointMatricesLieSubalgebra J) :
(skewAdjointMatricesLieSubalgebraEquivTranspose J e h A : Matrix m m R) = e A :=
rfl
#align skew_adjoint_matrices_lie_subalgebra_equiv_transpose_apply skewAdjointMatricesLieSubalgebraEquivTranspose_apply
| Mathlib/Algebra/Lie/SkewAdjoint.lean | 170 | 176 | theorem mem_skewAdjointMatricesLieSubalgebra_unit_smul (u : Rˣ) (J A : Matrix n n R) :
A ∈ skewAdjointMatricesLieSubalgebra (u • J) ↔ A ∈ skewAdjointMatricesLieSubalgebra J := by |
change A ∈ skewAdjointMatricesSubmodule (u • J) ↔ A ∈ skewAdjointMatricesSubmodule J
simp only [mem_skewAdjointMatricesSubmodule, Matrix.IsSkewAdjoint, Matrix.IsAdjointPair]
constructor <;> intro h
· simpa using congr_arg (fun B => u⁻¹ • B) h
· simp [h]
|
/-
Copyright (c) 2022 Violeta Hernández Palacios. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Violeta Hernández Palacios
-/
import Mathlib.Algebra.Order.Ring.Basic
import Mathlib.Computability.Primrec
import Mathlib.Tactic.Ring
import Mathlib.Tactic.Linarith
#align_import computability.ackermann from "leanprover-community/mathlib"@"9b2660e1b25419042c8da10bf411aa3c67f14383"
/-!
# Ackermann function
In this file, we define the two-argument Ackermann function `ack`. Despite having a recursive
definition, we show that this isn't a primitive recursive function.
## Main results
- `exists_lt_ack_of_nat_primrec`: any primitive recursive function is pointwise bounded above by
`ack m` for some `m`.
- `not_primrec₂_ack`: the two-argument Ackermann function is not primitive recursive.
## Proof approach
We very broadly adapt the proof idea from
https://www.planetmath.org/ackermannfunctionisnotprimitiverecursive. Namely, we prove that for any
primitive recursive `f : ℕ → ℕ`, there exists `m` such that `f n < ack m n` for all `n`. This then
implies that `fun n => ack n n` can't be primitive recursive, and so neither can `ack`. We aren't
able to use the same bounds as in that proof though, since our approach of using pairing functions
differs from their approach of using multivariate functions.
The important bounds we show during the main inductive proof (`exists_lt_ack_of_nat_primrec`)
are the following. Assuming `∀ n, f n < ack a n` and `∀ n, g n < ack b n`, we have:
- `∀ n, pair (f n) (g n) < ack (max a b + 3) n`.
- `∀ n, g (f n) < ack (max a b + 2) n`.
- `∀ n, Nat.rec (f n.unpair.1) (fun (y IH : ℕ) => g (pair n.unpair.1 (pair y IH)))
n.unpair.2 < ack (max a b + 9) n`.
The last one is evidently the hardest. Using `unpair_add_le`, we reduce it to the more manageable
- `∀ m n, rec (f m) (fun (y IH : ℕ) => g (pair m (pair y IH))) n <
ack (max a b + 9) (m + n)`.
We then prove this by induction on `n`. Our proof crucially depends on `ack_pair_lt`, which is
applied twice, giving us a constant of `4 + 4`. The rest of the proof consists of simpler bounds
which bump up our constant to `9`.
-/
open Nat
/-- The two-argument Ackermann function, defined so that
- `ack 0 n = n + 1`
- `ack (m + 1) 0 = ack m 1`
- `ack (m + 1) (n + 1) = ack m (ack (m + 1) n)`.
This is of interest as both a fast-growing function, and as an example of a recursive function that
isn't primitive recursive. -/
def ack : ℕ → ℕ → ℕ
| 0, n => n + 1
| m + 1, 0 => ack m 1
| m + 1, n + 1 => ack m (ack (m + 1) n)
#align ack ack
@[simp]
theorem ack_zero (n : ℕ) : ack 0 n = n + 1 := by rw [ack]
#align ack_zero ack_zero
@[simp]
| Mathlib/Computability/Ackermann.lean | 74 | 74 | theorem ack_succ_zero (m : ℕ) : ack (m + 1) 0 = ack m 1 := by | rw [ack]
|
/-
Copyright (c) 2017 Mario Carneiro. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro, Floris van Doorn, Violeta Hernández Palacios
-/
import Mathlib.SetTheory.Cardinal.Ordinal
import Mathlib.SetTheory.Ordinal.FixedPoint
#align_import set_theory.cardinal.cofinality from "leanprover-community/mathlib"@"7c2ce0c2da15516b4e65d0c9e254bb6dc93abd1f"
/-!
# Cofinality
This file contains the definition of cofinality of an ordinal number and regular cardinals
## Main Definitions
* `Ordinal.cof o` is the cofinality of the ordinal `o`.
If `o` is the order type of the relation `<` on `α`, then `o.cof` is the smallest cardinality of a
subset `s` of α that is *cofinal* in `α`, i.e. `∀ x : α, ∃ y ∈ s, ¬ y < x`.
* `Cardinal.IsStrongLimit c` means that `c` is a strong limit cardinal:
`c ≠ 0 ∧ ∀ x < c, 2 ^ x < c`.
* `Cardinal.IsRegular c` means that `c` is a regular cardinal: `ℵ₀ ≤ c ∧ c.ord.cof = c`.
* `Cardinal.IsInaccessible c` means that `c` is strongly inaccessible:
`ℵ₀ < c ∧ IsRegular c ∧ IsStrongLimit c`.
## Main Statements
* `Ordinal.infinite_pigeonhole_card`: the infinite pigeonhole principle
* `Cardinal.lt_power_cof`: A consequence of König's theorem stating that `c < c ^ c.ord.cof` for
`c ≥ ℵ₀`
* `Cardinal.univ_inaccessible`: The type of ordinals in `Type u` form an inaccessible cardinal
(in `Type v` with `v > u`). This shows (externally) that in `Type u` there are at least `u`
inaccessible cardinals.
## Implementation Notes
* The cofinality is defined for ordinals.
If `c` is a cardinal number, its cofinality is `c.ord.cof`.
## Tags
cofinality, regular cardinals, limits cardinals, inaccessible cardinals,
infinite pigeonhole principle
-/
noncomputable section
open Function Cardinal Set Order
open scoped Classical
open Cardinal Ordinal
universe u v w
variable {α : Type*} {r : α → α → Prop}
/-! ### Cofinality of orders -/
namespace Order
/-- Cofinality of a reflexive order `≼`. This is the smallest cardinality
of a subset `S : Set α` such that `∀ a, ∃ b ∈ S, a ≼ b`. -/
def cof (r : α → α → Prop) : Cardinal :=
sInf { c | ∃ S : Set α, (∀ a, ∃ b ∈ S, r a b) ∧ #S = c }
#align order.cof Order.cof
/-- The set in the definition of `Order.cof` is nonempty. -/
theorem cof_nonempty (r : α → α → Prop) [IsRefl α r] :
{ c | ∃ S : Set α, (∀ a, ∃ b ∈ S, r a b) ∧ #S = c }.Nonempty :=
⟨_, Set.univ, fun a => ⟨a, ⟨⟩, refl _⟩, rfl⟩
#align order.cof_nonempty Order.cof_nonempty
theorem cof_le (r : α → α → Prop) {S : Set α} (h : ∀ a, ∃ b ∈ S, r a b) : cof r ≤ #S :=
csInf_le' ⟨S, h, rfl⟩
#align order.cof_le Order.cof_le
theorem le_cof {r : α → α → Prop} [IsRefl α r] (c : Cardinal) :
c ≤ cof r ↔ ∀ {S : Set α}, (∀ a, ∃ b ∈ S, r a b) → c ≤ #S := by
rw [cof, le_csInf_iff'' (cof_nonempty r)]
use fun H S h => H _ ⟨S, h, rfl⟩
rintro H d ⟨S, h, rfl⟩
exact H h
#align order.le_cof Order.le_cof
end Order
theorem RelIso.cof_le_lift {α : Type u} {β : Type v} {r : α → α → Prop} {s} [IsRefl β s]
(f : r ≃r s) : Cardinal.lift.{max u v} (Order.cof r) ≤
Cardinal.lift.{max u v} (Order.cof s) := by
rw [Order.cof, Order.cof, lift_sInf, lift_sInf,
le_csInf_iff'' ((Order.cof_nonempty s).image _)]
rintro - ⟨-, ⟨u, H, rfl⟩, rfl⟩
apply csInf_le'
refine
⟨_, ⟨f.symm '' u, fun a => ?_, rfl⟩,
lift_mk_eq.{u, v, max u v}.2 ⟨(f.symm.toEquiv.image u).symm⟩⟩
rcases H (f a) with ⟨b, hb, hb'⟩
refine ⟨f.symm b, mem_image_of_mem _ hb, f.map_rel_iff.1 ?_⟩
rwa [RelIso.apply_symm_apply]
#align rel_iso.cof_le_lift RelIso.cof_le_lift
theorem RelIso.cof_eq_lift {α : Type u} {β : Type v} {r s} [IsRefl α r] [IsRefl β s] (f : r ≃r s) :
Cardinal.lift.{max u v} (Order.cof r) = Cardinal.lift.{max u v} (Order.cof s) :=
(RelIso.cof_le_lift f).antisymm (RelIso.cof_le_lift f.symm)
#align rel_iso.cof_eq_lift RelIso.cof_eq_lift
theorem RelIso.cof_le {α β : Type u} {r : α → α → Prop} {s} [IsRefl β s] (f : r ≃r s) :
Order.cof r ≤ Order.cof s :=
lift_le.1 (RelIso.cof_le_lift f)
#align rel_iso.cof_le RelIso.cof_le
theorem RelIso.cof_eq {α β : Type u} {r s} [IsRefl α r] [IsRefl β s] (f : r ≃r s) :
Order.cof r = Order.cof s :=
lift_inj.1 (RelIso.cof_eq_lift f)
#align rel_iso.cof_eq RelIso.cof_eq
/-- Cofinality of a strict order `≺`. This is the smallest cardinality of a set `S : Set α` such
that `∀ a, ∃ b ∈ S, ¬ b ≺ a`. -/
def StrictOrder.cof (r : α → α → Prop) : Cardinal :=
Order.cof (swap rᶜ)
#align strict_order.cof StrictOrder.cof
/-- The set in the definition of `Order.StrictOrder.cof` is nonempty. -/
theorem StrictOrder.cof_nonempty (r : α → α → Prop) [IsIrrefl α r] :
{ c | ∃ S : Set α, Unbounded r S ∧ #S = c }.Nonempty :=
@Order.cof_nonempty α _ (IsRefl.swap rᶜ)
#align strict_order.cof_nonempty StrictOrder.cof_nonempty
/-! ### Cofinality of ordinals -/
namespace Ordinal
/-- Cofinality of an ordinal. This is the smallest cardinal of a
subset `S` of the ordinal which is unbounded, in the sense
`∀ a, ∃ b ∈ S, a ≤ b`. It is defined for all ordinals, but
`cof 0 = 0` and `cof (succ o) = 1`, so it is only really
interesting on limit ordinals (when it is an infinite cardinal). -/
def cof (o : Ordinal.{u}) : Cardinal.{u} :=
o.liftOn (fun a => StrictOrder.cof a.r)
(by
rintro ⟨α, r, wo₁⟩ ⟨β, s, wo₂⟩ ⟨⟨f, hf⟩⟩
haveI := wo₁; haveI := wo₂
dsimp only
apply @RelIso.cof_eq _ _ _ _ ?_ ?_
· constructor
exact @fun a b => not_iff_not.2 hf
· dsimp only [swap]
exact ⟨fun _ => irrefl _⟩
· dsimp only [swap]
exact ⟨fun _ => irrefl _⟩)
#align ordinal.cof Ordinal.cof
theorem cof_type (r : α → α → Prop) [IsWellOrder α r] : (type r).cof = StrictOrder.cof r :=
rfl
#align ordinal.cof_type Ordinal.cof_type
theorem le_cof_type [IsWellOrder α r] {c} : c ≤ cof (type r) ↔ ∀ S, Unbounded r S → c ≤ #S :=
(le_csInf_iff'' (StrictOrder.cof_nonempty r)).trans
⟨fun H S h => H _ ⟨S, h, rfl⟩, by
rintro H d ⟨S, h, rfl⟩
exact H _ h⟩
#align ordinal.le_cof_type Ordinal.le_cof_type
theorem cof_type_le [IsWellOrder α r] {S : Set α} (h : Unbounded r S) : cof (type r) ≤ #S :=
le_cof_type.1 le_rfl S h
#align ordinal.cof_type_le Ordinal.cof_type_le
theorem lt_cof_type [IsWellOrder α r] {S : Set α} : #S < cof (type r) → Bounded r S := by
simpa using not_imp_not.2 cof_type_le
#align ordinal.lt_cof_type Ordinal.lt_cof_type
theorem cof_eq (r : α → α → Prop) [IsWellOrder α r] : ∃ S, Unbounded r S ∧ #S = cof (type r) :=
csInf_mem (StrictOrder.cof_nonempty r)
#align ordinal.cof_eq Ordinal.cof_eq
theorem ord_cof_eq (r : α → α → Prop) [IsWellOrder α r] :
∃ S, Unbounded r S ∧ type (Subrel r S) = (cof (type r)).ord := by
let ⟨S, hS, e⟩ := cof_eq r
let ⟨s, _, e'⟩ := Cardinal.ord_eq S
let T : Set α := { a | ∃ aS : a ∈ S, ∀ b : S, s b ⟨_, aS⟩ → r b a }
suffices Unbounded r T by
refine ⟨T, this, le_antisymm ?_ (Cardinal.ord_le.2 <| cof_type_le this)⟩
rw [← e, e']
refine
(RelEmbedding.ofMonotone
(fun a : T =>
(⟨a,
let ⟨aS, _⟩ := a.2
aS⟩ :
S))
fun a b h => ?_).ordinal_type_le
rcases a with ⟨a, aS, ha⟩
rcases b with ⟨b, bS, hb⟩
change s ⟨a, _⟩ ⟨b, _⟩
refine ((trichotomous_of s _ _).resolve_left fun hn => ?_).resolve_left ?_
· exact asymm h (ha _ hn)
· intro e
injection e with e
subst b
exact irrefl _ h
intro a
have : { b : S | ¬r b a }.Nonempty :=
let ⟨b, bS, ba⟩ := hS a
⟨⟨b, bS⟩, ba⟩
let b := (IsWellFounded.wf : WellFounded s).min _ this
have ba : ¬r b a := IsWellFounded.wf.min_mem _ this
refine ⟨b, ⟨b.2, fun c => not_imp_not.1 fun h => ?_⟩, ba⟩
rw [show ∀ b : S, (⟨b, b.2⟩ : S) = b by intro b; cases b; rfl]
exact IsWellFounded.wf.not_lt_min _ this (IsOrderConnected.neg_trans h ba)
#align ordinal.ord_cof_eq Ordinal.ord_cof_eq
/-! ### Cofinality of suprema and least strict upper bounds -/
private theorem card_mem_cof {o} : ∃ (ι : _) (f : ι → Ordinal), lsub.{u, u} f = o ∧ #ι = o.card :=
⟨_, _, lsub_typein o, mk_ordinal_out o⟩
/-- The set in the `lsub` characterization of `cof` is nonempty. -/
theorem cof_lsub_def_nonempty (o) :
{ a : Cardinal | ∃ (ι : _) (f : ι → Ordinal), lsub.{u, u} f = o ∧ #ι = a }.Nonempty :=
⟨_, card_mem_cof⟩
#align ordinal.cof_lsub_def_nonempty Ordinal.cof_lsub_def_nonempty
theorem cof_eq_sInf_lsub (o : Ordinal.{u}) : cof o =
sInf { a : Cardinal | ∃ (ι : Type u) (f : ι → Ordinal), lsub.{u, u} f = o ∧ #ι = a } := by
refine le_antisymm (le_csInf (cof_lsub_def_nonempty o) ?_) (csInf_le' ?_)
· rintro a ⟨ι, f, hf, rfl⟩
rw [← type_lt o]
refine
(cof_type_le fun a => ?_).trans
(@mk_le_of_injective _ _
(fun s : typein ((· < ·) : o.out.α → o.out.α → Prop) ⁻¹' Set.range f =>
Classical.choose s.prop)
fun s t hst => by
let H := congr_arg f hst
rwa [Classical.choose_spec s.prop, Classical.choose_spec t.prop, typein_inj,
Subtype.coe_inj] at H)
have := typein_lt_self a
simp_rw [← hf, lt_lsub_iff] at this
cases' this with i hi
refine ⟨enum (· < ·) (f i) ?_, ?_, ?_⟩
· rw [type_lt, ← hf]
apply lt_lsub
· rw [mem_preimage, typein_enum]
exact mem_range_self i
· rwa [← typein_le_typein, typein_enum]
· rcases cof_eq (· < · : (Quotient.out o).α → (Quotient.out o).α → Prop) with ⟨S, hS, hS'⟩
let f : S → Ordinal := fun s => typein LT.lt s.val
refine ⟨S, f, le_antisymm (lsub_le fun i => typein_lt_self (o := o) i)
(le_of_forall_lt fun a ha => ?_), by rwa [type_lt o] at hS'⟩
rw [← type_lt o] at ha
rcases hS (enum (· < ·) a ha) with ⟨b, hb, hb'⟩
rw [← typein_le_typein, typein_enum] at hb'
exact hb'.trans_lt (lt_lsub.{u, u} f ⟨b, hb⟩)
#align ordinal.cof_eq_Inf_lsub Ordinal.cof_eq_sInf_lsub
@[simp]
theorem lift_cof (o) : Cardinal.lift.{u, v} (cof o) = cof (Ordinal.lift.{u, v} o) := by
refine inductionOn o ?_
intro α r _
apply le_antisymm
· refine le_cof_type.2 fun S H => ?_
have : Cardinal.lift.{u, v} #(ULift.up ⁻¹' S) ≤ #(S : Type (max u v)) := by
rw [← Cardinal.lift_umax.{v, u}, ← Cardinal.lift_id'.{v, u} #S]
exact mk_preimage_of_injective_lift.{v, max u v} ULift.up S (ULift.up_injective.{u, v})
refine (Cardinal.lift_le.2 <| cof_type_le ?_).trans this
exact fun a =>
let ⟨⟨b⟩, bs, br⟩ := H ⟨a⟩
⟨b, bs, br⟩
· rcases cof_eq r with ⟨S, H, e'⟩
have : #(ULift.down.{u, v} ⁻¹' S) ≤ Cardinal.lift.{u, v} #S :=
⟨⟨fun ⟨⟨x⟩, h⟩ => ⟨⟨x, h⟩⟩, fun ⟨⟨x⟩, h₁⟩ ⟨⟨y⟩, h₂⟩ e => by
simp at e; congr⟩⟩
rw [e'] at this
refine (cof_type_le ?_).trans this
exact fun ⟨a⟩ =>
let ⟨b, bs, br⟩ := H a
⟨⟨b⟩, bs, br⟩
#align ordinal.lift_cof Ordinal.lift_cof
theorem cof_le_card (o) : cof o ≤ card o := by
rw [cof_eq_sInf_lsub]
exact csInf_le' card_mem_cof
#align ordinal.cof_le_card Ordinal.cof_le_card
theorem cof_ord_le (c : Cardinal) : c.ord.cof ≤ c := by simpa using cof_le_card c.ord
#align ordinal.cof_ord_le Ordinal.cof_ord_le
theorem ord_cof_le (o : Ordinal.{u}) : o.cof.ord ≤ o :=
(ord_le_ord.2 (cof_le_card o)).trans (ord_card_le o)
#align ordinal.ord_cof_le Ordinal.ord_cof_le
theorem exists_lsub_cof (o : Ordinal) :
∃ (ι : _) (f : ι → Ordinal), lsub.{u, u} f = o ∧ #ι = cof o := by
rw [cof_eq_sInf_lsub]
exact csInf_mem (cof_lsub_def_nonempty o)
#align ordinal.exists_lsub_cof Ordinal.exists_lsub_cof
theorem cof_lsub_le {ι} (f : ι → Ordinal) : cof (lsub.{u, u} f) ≤ #ι := by
rw [cof_eq_sInf_lsub]
exact csInf_le' ⟨ι, f, rfl, rfl⟩
#align ordinal.cof_lsub_le Ordinal.cof_lsub_le
theorem cof_lsub_le_lift {ι} (f : ι → Ordinal) :
cof (lsub.{u, v} f) ≤ Cardinal.lift.{v, u} #ι := by
rw [← mk_uLift.{u, v}]
convert cof_lsub_le.{max u v} fun i : ULift.{v, u} ι => f i.down
exact
lsub_eq_of_range_eq.{u, max u v, max u v}
(Set.ext fun x => ⟨fun ⟨i, hi⟩ => ⟨ULift.up.{v, u} i, hi⟩, fun ⟨i, hi⟩ => ⟨_, hi⟩⟩)
#align ordinal.cof_lsub_le_lift Ordinal.cof_lsub_le_lift
theorem le_cof_iff_lsub {o : Ordinal} {a : Cardinal} :
a ≤ cof o ↔ ∀ {ι} (f : ι → Ordinal), lsub.{u, u} f = o → a ≤ #ι := by
rw [cof_eq_sInf_lsub]
exact
(le_csInf_iff'' (cof_lsub_def_nonempty o)).trans
⟨fun H ι f hf => H _ ⟨ι, f, hf, rfl⟩, fun H b ⟨ι, f, hf, hb⟩ => by
rw [← hb]
exact H _ hf⟩
#align ordinal.le_cof_iff_lsub Ordinal.le_cof_iff_lsub
theorem lsub_lt_ord_lift {ι} {f : ι → Ordinal} {c : Ordinal}
(hι : Cardinal.lift.{v, u} #ι < c.cof)
(hf : ∀ i, f i < c) : lsub.{u, v} f < c :=
lt_of_le_of_ne (lsub_le.{v, u} hf) fun h => by
subst h
exact (cof_lsub_le_lift.{u, v} f).not_lt hι
#align ordinal.lsub_lt_ord_lift Ordinal.lsub_lt_ord_lift
theorem lsub_lt_ord {ι} {f : ι → Ordinal} {c : Ordinal} (hι : #ι < c.cof) :
(∀ i, f i < c) → lsub.{u, u} f < c :=
lsub_lt_ord_lift (by rwa [(#ι).lift_id])
#align ordinal.lsub_lt_ord Ordinal.lsub_lt_ord
theorem cof_sup_le_lift {ι} {f : ι → Ordinal} (H : ∀ i, f i < sup.{u, v} f) :
cof (sup.{u, v} f) ≤ Cardinal.lift.{v, u} #ι := by
rw [← sup_eq_lsub_iff_lt_sup.{u, v}] at H
rw [H]
exact cof_lsub_le_lift f
#align ordinal.cof_sup_le_lift Ordinal.cof_sup_le_lift
theorem cof_sup_le {ι} {f : ι → Ordinal} (H : ∀ i, f i < sup.{u, u} f) :
cof (sup.{u, u} f) ≤ #ι := by
rw [← (#ι).lift_id]
exact cof_sup_le_lift H
#align ordinal.cof_sup_le Ordinal.cof_sup_le
theorem sup_lt_ord_lift {ι} {f : ι → Ordinal} {c : Ordinal} (hι : Cardinal.lift.{v, u} #ι < c.cof)
(hf : ∀ i, f i < c) : sup.{u, v} f < c :=
(sup_le_lsub.{u, v} f).trans_lt (lsub_lt_ord_lift hι hf)
#align ordinal.sup_lt_ord_lift Ordinal.sup_lt_ord_lift
theorem sup_lt_ord {ι} {f : ι → Ordinal} {c : Ordinal} (hι : #ι < c.cof) :
(∀ i, f i < c) → sup.{u, u} f < c :=
sup_lt_ord_lift (by rwa [(#ι).lift_id])
#align ordinal.sup_lt_ord Ordinal.sup_lt_ord
theorem iSup_lt_lift {ι} {f : ι → Cardinal} {c : Cardinal}
(hι : Cardinal.lift.{v, u} #ι < c.ord.cof)
(hf : ∀ i, f i < c) : iSup.{max u v + 1, u + 1} f < c := by
rw [← ord_lt_ord, iSup_ord (Cardinal.bddAbove_range.{u, v} _)]
refine sup_lt_ord_lift hι fun i => ?_
rw [ord_lt_ord]
apply hf
#align ordinal.supr_lt_lift Ordinal.iSup_lt_lift
theorem iSup_lt {ι} {f : ι → Cardinal} {c : Cardinal} (hι : #ι < c.ord.cof) :
(∀ i, f i < c) → iSup f < c :=
iSup_lt_lift (by rwa [(#ι).lift_id])
#align ordinal.supr_lt Ordinal.iSup_lt
theorem nfpFamily_lt_ord_lift {ι} {f : ι → Ordinal → Ordinal} {c} (hc : ℵ₀ < cof c)
(hc' : Cardinal.lift.{v, u} #ι < cof c) (hf : ∀ (i), ∀ b < c, f i b < c) {a} (ha : a < c) :
nfpFamily.{u, v} f a < c := by
refine sup_lt_ord_lift ((Cardinal.lift_le.2 (mk_list_le_max ι)).trans_lt ?_) fun l => ?_
· rw [lift_max]
apply max_lt _ hc'
rwa [Cardinal.lift_aleph0]
· induction' l with i l H
· exact ha
· exact hf _ _ H
#align ordinal.nfp_family_lt_ord_lift Ordinal.nfpFamily_lt_ord_lift
theorem nfpFamily_lt_ord {ι} {f : ι → Ordinal → Ordinal} {c} (hc : ℵ₀ < cof c) (hc' : #ι < cof c)
(hf : ∀ (i), ∀ b < c, f i b < c) {a} : a < c → nfpFamily.{u, u} f a < c :=
nfpFamily_lt_ord_lift hc (by rwa [(#ι).lift_id]) hf
#align ordinal.nfp_family_lt_ord Ordinal.nfpFamily_lt_ord
theorem nfpBFamily_lt_ord_lift {o : Ordinal} {f : ∀ a < o, Ordinal → Ordinal} {c} (hc : ℵ₀ < cof c)
(hc' : Cardinal.lift.{v, u} o.card < cof c) (hf : ∀ (i hi), ∀ b < c, f i hi b < c) {a} :
a < c → nfpBFamily.{u, v} o f a < c :=
nfpFamily_lt_ord_lift hc (by rwa [mk_ordinal_out]) fun i => hf _ _
#align ordinal.nfp_bfamily_lt_ord_lift Ordinal.nfpBFamily_lt_ord_lift
theorem nfpBFamily_lt_ord {o : Ordinal} {f : ∀ a < o, Ordinal → Ordinal} {c} (hc : ℵ₀ < cof c)
(hc' : o.card < cof c) (hf : ∀ (i hi), ∀ b < c, f i hi b < c) {a} :
a < c → nfpBFamily.{u, u} o f a < c :=
nfpBFamily_lt_ord_lift hc (by rwa [o.card.lift_id]) hf
#align ordinal.nfp_bfamily_lt_ord Ordinal.nfpBFamily_lt_ord
theorem nfp_lt_ord {f : Ordinal → Ordinal} {c} (hc : ℵ₀ < cof c) (hf : ∀ i < c, f i < c) {a} :
a < c → nfp f a < c :=
nfpFamily_lt_ord_lift hc (by simpa using Cardinal.one_lt_aleph0.trans hc) fun _ => hf
#align ordinal.nfp_lt_ord Ordinal.nfp_lt_ord
theorem exists_blsub_cof (o : Ordinal) :
∃ f : ∀ a < (cof o).ord, Ordinal, blsub.{u, u} _ f = o := by
rcases exists_lsub_cof o with ⟨ι, f, hf, hι⟩
rcases Cardinal.ord_eq ι with ⟨r, hr, hι'⟩
rw [← @blsub_eq_lsub' ι r hr] at hf
rw [← hι, hι']
exact ⟨_, hf⟩
#align ordinal.exists_blsub_cof Ordinal.exists_blsub_cof
theorem le_cof_iff_blsub {b : Ordinal} {a : Cardinal} :
a ≤ cof b ↔ ∀ {o} (f : ∀ a < o, Ordinal), blsub.{u, u} o f = b → a ≤ o.card :=
le_cof_iff_lsub.trans
⟨fun H o f hf => by simpa using H _ hf, fun H ι f hf => by
rcases Cardinal.ord_eq ι with ⟨r, hr, hι'⟩
rw [← @blsub_eq_lsub' ι r hr] at hf
simpa using H _ hf⟩
#align ordinal.le_cof_iff_blsub Ordinal.le_cof_iff_blsub
theorem cof_blsub_le_lift {o} (f : ∀ a < o, Ordinal) :
cof (blsub.{u, v} o f) ≤ Cardinal.lift.{v, u} o.card := by
rw [← mk_ordinal_out o]
exact cof_lsub_le_lift _
#align ordinal.cof_blsub_le_lift Ordinal.cof_blsub_le_lift
theorem cof_blsub_le {o} (f : ∀ a < o, Ordinal) : cof (blsub.{u, u} o f) ≤ o.card := by
rw [← o.card.lift_id]
exact cof_blsub_le_lift f
#align ordinal.cof_blsub_le Ordinal.cof_blsub_le
theorem blsub_lt_ord_lift {o : Ordinal.{u}} {f : ∀ a < o, Ordinal} {c : Ordinal}
(ho : Cardinal.lift.{v, u} o.card < c.cof) (hf : ∀ i hi, f i hi < c) : blsub.{u, v} o f < c :=
lt_of_le_of_ne (blsub_le hf) fun h =>
ho.not_le (by simpa [← iSup_ord, hf, h] using cof_blsub_le_lift.{u, v} f)
#align ordinal.blsub_lt_ord_lift Ordinal.blsub_lt_ord_lift
theorem blsub_lt_ord {o : Ordinal} {f : ∀ a < o, Ordinal} {c : Ordinal} (ho : o.card < c.cof)
(hf : ∀ i hi, f i hi < c) : blsub.{u, u} o f < c :=
blsub_lt_ord_lift (by rwa [o.card.lift_id]) hf
#align ordinal.blsub_lt_ord Ordinal.blsub_lt_ord
theorem cof_bsup_le_lift {o : Ordinal} {f : ∀ a < o, Ordinal} (H : ∀ i h, f i h < bsup.{u, v} o f) :
cof (bsup.{u, v} o f) ≤ Cardinal.lift.{v, u} o.card := by
rw [← bsup_eq_blsub_iff_lt_bsup.{u, v}] at H
rw [H]
exact cof_blsub_le_lift.{u, v} f
#align ordinal.cof_bsup_le_lift Ordinal.cof_bsup_le_lift
theorem cof_bsup_le {o : Ordinal} {f : ∀ a < o, Ordinal} :
(∀ i h, f i h < bsup.{u, u} o f) → cof (bsup.{u, u} o f) ≤ o.card := by
rw [← o.card.lift_id]
exact cof_bsup_le_lift
#align ordinal.cof_bsup_le Ordinal.cof_bsup_le
theorem bsup_lt_ord_lift {o : Ordinal} {f : ∀ a < o, Ordinal} {c : Ordinal}
(ho : Cardinal.lift.{v, u} o.card < c.cof) (hf : ∀ i hi, f i hi < c) : bsup.{u, v} o f < c :=
(bsup_le_blsub f).trans_lt (blsub_lt_ord_lift ho hf)
#align ordinal.bsup_lt_ord_lift Ordinal.bsup_lt_ord_lift
theorem bsup_lt_ord {o : Ordinal} {f : ∀ a < o, Ordinal} {c : Ordinal} (ho : o.card < c.cof) :
(∀ i hi, f i hi < c) → bsup.{u, u} o f < c :=
bsup_lt_ord_lift (by rwa [o.card.lift_id])
#align ordinal.bsup_lt_ord Ordinal.bsup_lt_ord
/-! ### Basic results -/
@[simp]
theorem cof_zero : cof 0 = 0 := by
refine LE.le.antisymm ?_ (Cardinal.zero_le _)
rw [← card_zero]
exact cof_le_card 0
#align ordinal.cof_zero Ordinal.cof_zero
@[simp]
theorem cof_eq_zero {o} : cof o = 0 ↔ o = 0 :=
⟨inductionOn o fun α r _ z =>
let ⟨S, hl, e⟩ := cof_eq r
type_eq_zero_iff_isEmpty.2 <|
⟨fun a =>
let ⟨b, h, _⟩ := hl a
(mk_eq_zero_iff.1 (e.trans z)).elim' ⟨_, h⟩⟩,
fun e => by simp [e]⟩
#align ordinal.cof_eq_zero Ordinal.cof_eq_zero
theorem cof_ne_zero {o} : cof o ≠ 0 ↔ o ≠ 0 :=
cof_eq_zero.not
#align ordinal.cof_ne_zero Ordinal.cof_ne_zero
@[simp]
theorem cof_succ (o) : cof (succ o) = 1 := by
apply le_antisymm
· refine inductionOn o fun α r _ => ?_
change cof (type _) ≤ _
rw [← (_ : #_ = 1)]
· apply cof_type_le
refine fun a => ⟨Sum.inr PUnit.unit, Set.mem_singleton _, ?_⟩
rcases a with (a | ⟨⟨⟨⟩⟩⟩) <;> simp [EmptyRelation]
· rw [Cardinal.mk_fintype, Set.card_singleton]
simp
· rw [← Cardinal.succ_zero, succ_le_iff]
simpa [lt_iff_le_and_ne, Cardinal.zero_le] using fun h =>
succ_ne_zero o (cof_eq_zero.1 (Eq.symm h))
#align ordinal.cof_succ Ordinal.cof_succ
@[simp]
theorem cof_eq_one_iff_is_succ {o} : cof.{u} o = 1 ↔ ∃ a, o = succ a :=
⟨inductionOn o fun α r _ z => by
rcases cof_eq r with ⟨S, hl, e⟩; rw [z] at e
cases' mk_ne_zero_iff.1 (by rw [e]; exact one_ne_zero) with a
refine
⟨typein r a,
Eq.symm <|
Quotient.sound
⟨RelIso.ofSurjective (RelEmbedding.ofMonotone ?_ fun x y => ?_) fun x => ?_⟩⟩
· apply Sum.rec <;> [exact Subtype.val; exact fun _ => a]
· rcases x with (x | ⟨⟨⟨⟩⟩⟩) <;> rcases y with (y | ⟨⟨⟨⟩⟩⟩) <;>
simp [Subrel, Order.Preimage, EmptyRelation]
exact x.2
· suffices r x a ∨ ∃ _ : PUnit.{u}, ↑a = x by
convert this
dsimp [RelEmbedding.ofMonotone]; simp
rcases trichotomous_of r x a with (h | h | h)
· exact Or.inl h
· exact Or.inr ⟨PUnit.unit, h.symm⟩
· rcases hl x with ⟨a', aS, hn⟩
rw [(_ : ↑a = a')] at h
· exact absurd h hn
refine congr_arg Subtype.val (?_ : a = ⟨a', aS⟩)
haveI := le_one_iff_subsingleton.1 (le_of_eq e)
apply Subsingleton.elim,
fun ⟨a, e⟩ => by simp [e]⟩
#align ordinal.cof_eq_one_iff_is_succ Ordinal.cof_eq_one_iff_is_succ
/-- A fundamental sequence for `a` is an increasing sequence of length `o = cof a` that converges at
`a`. We provide `o` explicitly in order to avoid type rewrites. -/
def IsFundamentalSequence (a o : Ordinal.{u}) (f : ∀ b < o, Ordinal.{u}) : Prop :=
o ≤ a.cof.ord ∧ (∀ {i j} (hi hj), i < j → f i hi < f j hj) ∧ blsub.{u, u} o f = a
#align ordinal.is_fundamental_sequence Ordinal.IsFundamentalSequence
namespace IsFundamentalSequence
variable {a o : Ordinal.{u}} {f : ∀ b < o, Ordinal.{u}}
protected theorem cof_eq (hf : IsFundamentalSequence a o f) : a.cof.ord = o :=
hf.1.antisymm' <| by
rw [← hf.2.2]
exact (ord_le_ord.2 (cof_blsub_le f)).trans (ord_card_le o)
#align ordinal.is_fundamental_sequence.cof_eq Ordinal.IsFundamentalSequence.cof_eq
protected theorem strict_mono (hf : IsFundamentalSequence a o f) {i j} :
∀ hi hj, i < j → f i hi < f j hj :=
hf.2.1
#align ordinal.is_fundamental_sequence.strict_mono Ordinal.IsFundamentalSequence.strict_mono
theorem blsub_eq (hf : IsFundamentalSequence a o f) : blsub.{u, u} o f = a :=
hf.2.2
#align ordinal.is_fundamental_sequence.blsub_eq Ordinal.IsFundamentalSequence.blsub_eq
theorem ord_cof (hf : IsFundamentalSequence a o f) :
IsFundamentalSequence a a.cof.ord fun i hi => f i (hi.trans_le (by rw [hf.cof_eq])) := by
have H := hf.cof_eq
subst H
exact hf
#align ordinal.is_fundamental_sequence.ord_cof Ordinal.IsFundamentalSequence.ord_cof
theorem id_of_le_cof (h : o ≤ o.cof.ord) : IsFundamentalSequence o o fun a _ => a :=
⟨h, @fun _ _ _ _ => id, blsub_id o⟩
#align ordinal.is_fundamental_sequence.id_of_le_cof Ordinal.IsFundamentalSequence.id_of_le_cof
protected theorem zero {f : ∀ b < (0 : Ordinal), Ordinal} : IsFundamentalSequence 0 0 f :=
⟨by rw [cof_zero, ord_zero], @fun i j hi => (Ordinal.not_lt_zero i hi).elim, blsub_zero f⟩
#align ordinal.is_fundamental_sequence.zero Ordinal.IsFundamentalSequence.zero
protected theorem succ : IsFundamentalSequence (succ o) 1 fun _ _ => o := by
refine ⟨?_, @fun i j hi hj h => ?_, blsub_const Ordinal.one_ne_zero o⟩
· rw [cof_succ, ord_one]
· rw [lt_one_iff_zero] at hi hj
rw [hi, hj] at h
exact h.false.elim
#align ordinal.is_fundamental_sequence.succ Ordinal.IsFundamentalSequence.succ
protected theorem monotone (hf : IsFundamentalSequence a o f) {i j : Ordinal} (hi : i < o)
(hj : j < o) (hij : i ≤ j) : f i hi ≤ f j hj := by
rcases lt_or_eq_of_le hij with (hij | rfl)
· exact (hf.2.1 hi hj hij).le
· rfl
#align ordinal.is_fundamental_sequence.monotone Ordinal.IsFundamentalSequence.monotone
theorem trans {a o o' : Ordinal.{u}} {f : ∀ b < o, Ordinal.{u}} (hf : IsFundamentalSequence a o f)
{g : ∀ b < o', Ordinal.{u}} (hg : IsFundamentalSequence o o' g) :
IsFundamentalSequence a o' fun i hi =>
f (g i hi) (by rw [← hg.2.2]; apply lt_blsub) := by
refine ⟨?_, @fun i j _ _ h => hf.2.1 _ _ (hg.2.1 _ _ h), ?_⟩
· rw [hf.cof_eq]
exact hg.1.trans (ord_cof_le o)
· rw [@blsub_comp.{u, u, u} o _ f (@IsFundamentalSequence.monotone _ _ f hf)]
· exact hf.2.2
· exact hg.2.2
#align ordinal.is_fundamental_sequence.trans Ordinal.IsFundamentalSequence.trans
end IsFundamentalSequence
/-- Every ordinal has a fundamental sequence. -/
theorem exists_fundamental_sequence (a : Ordinal.{u}) :
∃ f, IsFundamentalSequence a a.cof.ord f := by
suffices h : ∃ o f, IsFundamentalSequence a o f by
rcases h with ⟨o, f, hf⟩
exact ⟨_, hf.ord_cof⟩
rcases exists_lsub_cof a with ⟨ι, f, hf, hι⟩
rcases ord_eq ι with ⟨r, wo, hr⟩
haveI := wo
let r' := Subrel r { i | ∀ j, r j i → f j < f i }
let hrr' : r' ↪r r := Subrel.relEmbedding _ _
haveI := hrr'.isWellOrder
refine
⟨_, _, hrr'.ordinal_type_le.trans ?_, @fun i j _ h _ => (enum r' j h).prop _ ?_,
le_antisymm (blsub_le fun i hi => lsub_le_iff.1 hf.le _) ?_⟩
· rw [← hι, hr]
· change r (hrr'.1 _) (hrr'.1 _)
rwa [hrr'.2, @enum_lt_enum _ r']
· rw [← hf, lsub_le_iff]
intro i
suffices h : ∃ i' hi', f i ≤ bfamilyOfFamily' r' (fun i => f i) i' hi' by
rcases h with ⟨i', hi', hfg⟩
exact hfg.trans_lt (lt_blsub _ _ _)
by_cases h : ∀ j, r j i → f j < f i
· refine ⟨typein r' ⟨i, h⟩, typein_lt_type _ _, ?_⟩
rw [bfamilyOfFamily'_typein]
· push_neg at h
cases' wo.wf.min_mem _ h with hji hij
refine ⟨typein r' ⟨_, fun k hkj => lt_of_lt_of_le ?_ hij⟩, typein_lt_type _ _, ?_⟩
· by_contra! H
exact (wo.wf.not_lt_min _ h ⟨IsTrans.trans _ _ _ hkj hji, H⟩) hkj
· rwa [bfamilyOfFamily'_typein]
#align ordinal.exists_fundamental_sequence Ordinal.exists_fundamental_sequence
@[simp]
theorem cof_cof (a : Ordinal.{u}) : cof (cof a).ord = cof a := by
cases' exists_fundamental_sequence a with f hf
cases' exists_fundamental_sequence a.cof.ord with g hg
exact ord_injective (hf.trans hg).cof_eq.symm
#align ordinal.cof_cof Ordinal.cof_cof
protected theorem IsNormal.isFundamentalSequence {f : Ordinal.{u} → Ordinal.{u}} (hf : IsNormal f)
{a o} (ha : IsLimit a) {g} (hg : IsFundamentalSequence a o g) :
IsFundamentalSequence (f a) o fun b hb => f (g b hb) := by
refine ⟨?_, @fun i j _ _ h => hf.strictMono (hg.2.1 _ _ h), ?_⟩
· rcases exists_lsub_cof (f a) with ⟨ι, f', hf', hι⟩
rw [← hg.cof_eq, ord_le_ord, ← hι]
suffices (lsub.{u, u} fun i => sInf { b : Ordinal | f' i ≤ f b }) = a by
rw [← this]
apply cof_lsub_le
have H : ∀ i, ∃ b < a, f' i ≤ f b := fun i => by
have := lt_lsub.{u, u} f' i
rw [hf', ← IsNormal.blsub_eq.{u, u} hf ha, lt_blsub_iff] at this
simpa using this
refine (lsub_le fun i => ?_).antisymm (le_of_forall_lt fun b hb => ?_)
· rcases H i with ⟨b, hb, hb'⟩
exact lt_of_le_of_lt (csInf_le' hb') hb
· have := hf.strictMono hb
rw [← hf', lt_lsub_iff] at this
cases' this with i hi
rcases H i with ⟨b, _, hb⟩
exact
((le_csInf_iff'' ⟨b, by exact hb⟩).2 fun c hc =>
hf.strictMono.le_iff_le.1 (hi.trans hc)).trans_lt (lt_lsub _ i)
· rw [@blsub_comp.{u, u, u} a _ (fun b _ => f b) (@fun i j _ _ h => hf.strictMono.monotone h) g
hg.2.2]
exact IsNormal.blsub_eq.{u, u} hf ha
#align ordinal.is_normal.is_fundamental_sequence Ordinal.IsNormal.isFundamentalSequence
theorem IsNormal.cof_eq {f} (hf : IsNormal f) {a} (ha : IsLimit a) : cof (f a) = cof a :=
let ⟨_, hg⟩ := exists_fundamental_sequence a
ord_injective (hf.isFundamentalSequence ha hg).cof_eq
#align ordinal.is_normal.cof_eq Ordinal.IsNormal.cof_eq
theorem IsNormal.cof_le {f} (hf : IsNormal f) (a) : cof a ≤ cof (f a) := by
rcases zero_or_succ_or_limit a with (rfl | ⟨b, rfl⟩ | ha)
· rw [cof_zero]
exact zero_le _
· rw [cof_succ, Cardinal.one_le_iff_ne_zero, cof_ne_zero, ← Ordinal.pos_iff_ne_zero]
exact (Ordinal.zero_le (f b)).trans_lt (hf.1 b)
· rw [hf.cof_eq ha]
#align ordinal.is_normal.cof_le Ordinal.IsNormal.cof_le
@[simp]
theorem cof_add (a b : Ordinal) : b ≠ 0 → cof (a + b) = cof b := fun h => by
rcases zero_or_succ_or_limit b with (rfl | ⟨c, rfl⟩ | hb)
· contradiction
· rw [add_succ, cof_succ, cof_succ]
· exact (add_isNormal a).cof_eq hb
#align ordinal.cof_add Ordinal.cof_add
theorem aleph0_le_cof {o} : ℵ₀ ≤ cof o ↔ IsLimit o := by
rcases zero_or_succ_or_limit o with (rfl | ⟨o, rfl⟩ | l)
· simp [not_zero_isLimit, Cardinal.aleph0_ne_zero]
· simp [not_succ_isLimit, Cardinal.one_lt_aleph0]
· simp [l]
refine le_of_not_lt fun h => ?_
cases' Cardinal.lt_aleph0.1 h with n e
have := cof_cof o
rw [e, ord_nat] at this
cases n
· simp at e
simp [e, not_zero_isLimit] at l
· rw [natCast_succ, cof_succ] at this
rw [← this, cof_eq_one_iff_is_succ] at e
rcases e with ⟨a, rfl⟩
exact not_succ_isLimit _ l
#align ordinal.aleph_0_le_cof Ordinal.aleph0_le_cof
@[simp]
theorem aleph'_cof {o : Ordinal} (ho : o.IsLimit) : (aleph' o).ord.cof = o.cof :=
aleph'_isNormal.cof_eq ho
#align ordinal.aleph'_cof Ordinal.aleph'_cof
@[simp]
theorem aleph_cof {o : Ordinal} (ho : o.IsLimit) : (aleph o).ord.cof = o.cof :=
aleph_isNormal.cof_eq ho
#align ordinal.aleph_cof Ordinal.aleph_cof
@[simp]
theorem cof_omega : cof ω = ℵ₀ :=
(aleph0_le_cof.2 omega_isLimit).antisymm' <| by
rw [← card_omega]
apply cof_le_card
#align ordinal.cof_omega Ordinal.cof_omega
theorem cof_eq' (r : α → α → Prop) [IsWellOrder α r] (h : IsLimit (type r)) :
∃ S : Set α, (∀ a, ∃ b ∈ S, r a b) ∧ #S = cof (type r) :=
let ⟨S, H, e⟩ := cof_eq r
⟨S, fun a =>
let a' := enum r _ (h.2 _ (typein_lt_type r a))
let ⟨b, h, ab⟩ := H a'
⟨b, h,
(IsOrderConnected.conn a b a' <|
(typein_lt_typein r).1
(by
rw [typein_enum]
exact lt_succ (typein _ _))).resolve_right
ab⟩,
e⟩
#align ordinal.cof_eq' Ordinal.cof_eq'
@[simp]
theorem cof_univ : cof univ.{u, v} = Cardinal.univ.{u, v} :=
le_antisymm (cof_le_card _)
(by
refine le_of_forall_lt fun c h => ?_
rcases lt_univ'.1 h with ⟨c, rfl⟩
rcases @cof_eq Ordinal.{u} (· < ·) _ with ⟨S, H, Se⟩
rw [univ, ← lift_cof, ← Cardinal.lift_lift.{u+1, v, u}, Cardinal.lift_lt, ← Se]
refine lt_of_not_ge fun h => ?_
cases' Cardinal.lift_down h with a e
refine Quotient.inductionOn a (fun α e => ?_) e
cases' Quotient.exact e with f
have f := Equiv.ulift.symm.trans f
let g a := (f a).1
let o := succ (sup.{u, u} g)
rcases H o with ⟨b, h, l⟩
refine l (lt_succ_iff.2 ?_)
rw [← show g (f.symm ⟨b, h⟩) = b by simp [g]]
apply le_sup)
#align ordinal.cof_univ Ordinal.cof_univ
/-! ### Infinite pigeonhole principle -/
/-- If the union of s is unbounded and s is smaller than the cofinality,
then s has an unbounded member -/
theorem unbounded_of_unbounded_sUnion (r : α → α → Prop) [wo : IsWellOrder α r] {s : Set (Set α)}
(h₁ : Unbounded r <| ⋃₀ s) (h₂ : #s < StrictOrder.cof r) : ∃ x ∈ s, Unbounded r x := by
by_contra! h
simp_rw [not_unbounded_iff] at h
let f : s → α := fun x : s => wo.wf.sup x (h x.1 x.2)
refine h₂.not_le (le_trans (csInf_le' ⟨range f, fun x => ?_, rfl⟩) mk_range_le)
rcases h₁ x with ⟨y, ⟨c, hc, hy⟩, hxy⟩
exact ⟨f ⟨c, hc⟩, mem_range_self _, fun hxz => hxy (Trans.trans (wo.wf.lt_sup _ hy) hxz)⟩
#align ordinal.unbounded_of_unbounded_sUnion Ordinal.unbounded_of_unbounded_sUnion
/-- If the union of s is unbounded and s is smaller than the cofinality,
then s has an unbounded member -/
theorem unbounded_of_unbounded_iUnion {α β : Type u} (r : α → α → Prop) [wo : IsWellOrder α r]
(s : β → Set α) (h₁ : Unbounded r <| ⋃ x, s x) (h₂ : #β < StrictOrder.cof r) :
∃ x : β, Unbounded r (s x) := by
rw [← sUnion_range] at h₁
rcases unbounded_of_unbounded_sUnion r h₁ (mk_range_le.trans_lt h₂) with ⟨_, ⟨x, rfl⟩, u⟩
exact ⟨x, u⟩
#align ordinal.unbounded_of_unbounded_Union Ordinal.unbounded_of_unbounded_iUnion
/-- The infinite pigeonhole principle -/
theorem infinite_pigeonhole {β α : Type u} (f : β → α) (h₁ : ℵ₀ ≤ #β) (h₂ : #α < (#β).ord.cof) :
∃ a : α, #(f ⁻¹' {a}) = #β := by
have : ∃ a, #β ≤ #(f ⁻¹' {a}) := by
by_contra! h
apply mk_univ.not_lt
rw [← preimage_univ, ← iUnion_of_singleton, preimage_iUnion]
exact
mk_iUnion_le_sum_mk.trans_lt
((sum_le_iSup _).trans_lt <| mul_lt_of_lt h₁ (h₂.trans_le <| cof_ord_le _) (iSup_lt h₂ h))
cases' this with x h
refine ⟨x, h.antisymm' ?_⟩
rw [le_mk_iff_exists_set]
exact ⟨_, rfl⟩
#align ordinal.infinite_pigeonhole Ordinal.infinite_pigeonhole
/-- Pigeonhole principle for a cardinality below the cardinality of the domain -/
theorem infinite_pigeonhole_card {β α : Type u} (f : β → α) (θ : Cardinal) (hθ : θ ≤ #β)
(h₁ : ℵ₀ ≤ θ) (h₂ : #α < θ.ord.cof) : ∃ a : α, θ ≤ #(f ⁻¹' {a}) := by
rcases le_mk_iff_exists_set.1 hθ with ⟨s, rfl⟩
cases' infinite_pigeonhole (f ∘ Subtype.val : s → α) h₁ h₂ with a ha
use a; rw [← ha, @preimage_comp _ _ _ Subtype.val f]
exact mk_preimage_of_injective _ _ Subtype.val_injective
#align ordinal.infinite_pigeonhole_card Ordinal.infinite_pigeonhole_card
theorem infinite_pigeonhole_set {β α : Type u} {s : Set β} (f : s → α) (θ : Cardinal)
(hθ : θ ≤ #s) (h₁ : ℵ₀ ≤ θ) (h₂ : #α < θ.ord.cof) :
∃ (a : α) (t : Set β) (h : t ⊆ s), θ ≤ #t ∧ ∀ ⦃x⦄ (hx : x ∈ t), f ⟨x, h hx⟩ = a := by
cases' infinite_pigeonhole_card f θ hθ h₁ h₂ with a ha
refine ⟨a, { x | ∃ h, f ⟨x, h⟩ = a }, ?_, ?_, ?_⟩
· rintro x ⟨hx, _⟩
exact hx
· refine
ha.trans
(ge_of_eq <|
Quotient.sound ⟨Equiv.trans ?_ (Equiv.subtypeSubtypeEquivSubtypeExists _ _).symm⟩)
simp only [coe_eq_subtype, mem_singleton_iff, mem_preimage, mem_setOf_eq]
rfl
rintro x ⟨_, hx'⟩; exact hx'
#align ordinal.infinite_pigeonhole_set Ordinal.infinite_pigeonhole_set
end Ordinal
/-! ### Regular and inaccessible cardinals -/
namespace Cardinal
open Ordinal
/-- A cardinal is a strong limit if it is not zero and it is
closed under powersets. Note that `ℵ₀` is a strong limit by this definition. -/
def IsStrongLimit (c : Cardinal) : Prop :=
c ≠ 0 ∧ ∀ x < c, (2^x) < c
#align cardinal.is_strong_limit Cardinal.IsStrongLimit
theorem IsStrongLimit.ne_zero {c} (h : IsStrongLimit c) : c ≠ 0 :=
h.1
#align cardinal.is_strong_limit.ne_zero Cardinal.IsStrongLimit.ne_zero
theorem IsStrongLimit.two_power_lt {x c} (h : IsStrongLimit c) : x < c → (2^x) < c :=
h.2 x
#align cardinal.is_strong_limit.two_power_lt Cardinal.IsStrongLimit.two_power_lt
theorem isStrongLimit_aleph0 : IsStrongLimit ℵ₀ :=
⟨aleph0_ne_zero, fun x hx => by
rcases lt_aleph0.1 hx with ⟨n, rfl⟩
exact mod_cast nat_lt_aleph0 (2 ^ n)⟩
#align cardinal.is_strong_limit_aleph_0 Cardinal.isStrongLimit_aleph0
protected theorem IsStrongLimit.isSuccLimit {c} (H : IsStrongLimit c) : IsSuccLimit c :=
isSuccLimit_of_succ_lt fun x h => (succ_le_of_lt <| cantor x).trans_lt (H.two_power_lt h)
#align cardinal.is_strong_limit.is_succ_limit Cardinal.IsStrongLimit.isSuccLimit
theorem IsStrongLimit.isLimit {c} (H : IsStrongLimit c) : IsLimit c :=
⟨H.ne_zero, H.isSuccLimit⟩
#align cardinal.is_strong_limit.is_limit Cardinal.IsStrongLimit.isLimit
theorem isStrongLimit_beth {o : Ordinal} (H : IsSuccLimit o) : IsStrongLimit (beth o) := by
rcases eq_or_ne o 0 with (rfl | h)
· rw [beth_zero]
exact isStrongLimit_aleph0
· refine ⟨beth_ne_zero o, fun a ha => ?_⟩
rw [beth_limit ⟨h, isSuccLimit_iff_succ_lt.1 H⟩] at ha
rcases exists_lt_of_lt_ciSup' ha with ⟨⟨i, hi⟩, ha⟩
have := power_le_power_left two_ne_zero ha.le
rw [← beth_succ] at this
exact this.trans_lt (beth_lt.2 (H.succ_lt hi))
#align cardinal.is_strong_limit_beth Cardinal.isStrongLimit_beth
theorem mk_bounded_subset {α : Type*} (h : ∀ x < #α, (2^x) < #α) {r : α → α → Prop}
[IsWellOrder α r] (hr : (#α).ord = type r) : #{ s : Set α // Bounded r s } = #α := by
rcases eq_or_ne #α 0 with (ha | ha)
· rw [ha]
haveI := mk_eq_zero_iff.1 ha
rw [mk_eq_zero_iff]
constructor
rintro ⟨s, hs⟩
exact (not_unbounded_iff s).2 hs (unbounded_of_isEmpty s)
have h' : IsStrongLimit #α := ⟨ha, h⟩
have ha := h'.isLimit.aleph0_le
apply le_antisymm
· have : { s : Set α | Bounded r s } = ⋃ i, 𝒫{ j | r j i } := setOf_exists _
rw [← coe_setOf, this]
refine mk_iUnion_le_sum_mk.trans ((sum_le_iSup (fun i => #(𝒫{ j | r j i }))).trans
((mul_le_max_of_aleph0_le_left ha).trans ?_))
rw [max_eq_left]
apply ciSup_le' _
intro i
rw [mk_powerset]
apply (h'.two_power_lt _).le
rw [coe_setOf, card_typein, ← lt_ord, hr]
apply typein_lt_type
· refine @mk_le_of_injective α _ (fun x => Subtype.mk {x} ?_) ?_
· apply bounded_singleton
rw [← hr]
apply ord_isLimit ha
· intro a b hab
simpa [singleton_eq_singleton_iff] using hab
#align cardinal.mk_bounded_subset Cardinal.mk_bounded_subset
theorem mk_subset_mk_lt_cof {α : Type*} (h : ∀ x < #α, (2^x) < #α) :
#{ s : Set α // #s < cof (#α).ord } = #α := by
rcases eq_or_ne #α 0 with (ha | ha)
· simp [ha]
have h' : IsStrongLimit #α := ⟨ha, h⟩
rcases ord_eq α with ⟨r, wo, hr⟩
haveI := wo
apply le_antisymm
· conv_rhs => rw [← mk_bounded_subset h hr]
apply mk_le_mk_of_subset
intro s hs
rw [hr] at hs
exact lt_cof_type hs
· refine @mk_le_of_injective α _ (fun x => Subtype.mk {x} ?_) ?_
· rw [mk_singleton]
exact one_lt_aleph0.trans_le (aleph0_le_cof.2 (ord_isLimit h'.isLimit.aleph0_le))
· intro a b hab
simpa [singleton_eq_singleton_iff] using hab
#align cardinal.mk_subset_mk_lt_cof Cardinal.mk_subset_mk_lt_cof
/-- A cardinal is regular if it is infinite and it equals its own cofinality. -/
def IsRegular (c : Cardinal) : Prop :=
ℵ₀ ≤ c ∧ c ≤ c.ord.cof
#align cardinal.is_regular Cardinal.IsRegular
theorem IsRegular.aleph0_le {c : Cardinal} (H : c.IsRegular) : ℵ₀ ≤ c :=
H.1
#align cardinal.is_regular.aleph_0_le Cardinal.IsRegular.aleph0_le
theorem IsRegular.cof_eq {c : Cardinal} (H : c.IsRegular) : c.ord.cof = c :=
(cof_ord_le c).antisymm H.2
#align cardinal.is_regular.cof_eq Cardinal.IsRegular.cof_eq
theorem IsRegular.pos {c : Cardinal} (H : c.IsRegular) : 0 < c :=
aleph0_pos.trans_le H.1
#align cardinal.is_regular.pos Cardinal.IsRegular.pos
theorem IsRegular.nat_lt {c : Cardinal} (H : c.IsRegular) (n : ℕ) : n < c :=
lt_of_lt_of_le (nat_lt_aleph0 n) H.aleph0_le
theorem IsRegular.ord_pos {c : Cardinal} (H : c.IsRegular) : 0 < c.ord := by
rw [Cardinal.lt_ord, card_zero]
exact H.pos
#align cardinal.is_regular.ord_pos Cardinal.IsRegular.ord_pos
theorem isRegular_cof {o : Ordinal} (h : o.IsLimit) : IsRegular o.cof :=
⟨aleph0_le_cof.2 h, (cof_cof o).ge⟩
#align cardinal.is_regular_cof Cardinal.isRegular_cof
theorem isRegular_aleph0 : IsRegular ℵ₀ :=
⟨le_rfl, by simp⟩
#align cardinal.is_regular_aleph_0 Cardinal.isRegular_aleph0
theorem isRegular_succ {c : Cardinal.{u}} (h : ℵ₀ ≤ c) : IsRegular (succ c) :=
⟨h.trans (le_succ c),
succ_le_of_lt
(by
cases' Quotient.exists_rep (@succ Cardinal _ _ c) with α αe; simp at αe
rcases ord_eq α with ⟨r, wo, re⟩
have := ord_isLimit (h.trans (le_succ _))
rw [← αe, re] at this ⊢
rcases cof_eq' r this with ⟨S, H, Se⟩
rw [← Se]
apply lt_imp_lt_of_le_imp_le fun h => mul_le_mul_right' h c
rw [mul_eq_self h, ← succ_le_iff, ← αe, ← sum_const']
refine le_trans ?_ (sum_le_sum (fun (x : S) => card (typein r (x : α))) _ fun i => ?_)
· simp only [← card_typein, ← mk_sigma]
exact
⟨Embedding.ofSurjective (fun x => x.2.1) fun a =>
let ⟨b, h, ab⟩ := H a
⟨⟨⟨_, h⟩, _, ab⟩, rfl⟩⟩
· rw [← lt_succ_iff, ← lt_ord, ← αe, re]
apply typein_lt_type)⟩
#align cardinal.is_regular_succ Cardinal.isRegular_succ
| Mathlib/SetTheory/Cardinal/Cofinality.lean | 997 | 999 | theorem isRegular_aleph_one : IsRegular (aleph 1) := by |
rw [← succ_aleph0]
exact isRegular_succ le_rfl
|
/-
Copyright (c) 2020 Johan Commelin, Robert Y. Lewis. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johan Commelin, Robert Y. Lewis
-/
import Mathlib.RingTheory.WittVector.Basic
import Mathlib.RingTheory.WittVector.IsPoly
#align_import ring_theory.witt_vector.init_tail from "leanprover-community/mathlib"@"0798037604b2d91748f9b43925fb7570a5f3256c"
/-!
# `init` and `tail`
Given a Witt vector `x`, we are sometimes interested
in its components before and after an index `n`.
This file defines those operations, proves that `init` is polynomial,
and shows how that polynomial interacts with `MvPolynomial.bind₁`.
## Main declarations
* `WittVector.init n x`: the first `n` coefficients of `x`, as a Witt vector. All coefficients at
indices ≥ `n` are 0.
* `WittVector.tail n x`: the complementary part to `init`. All coefficients at indices < `n` are 0,
otherwise they are the same as in `x`.
* `WittVector.coeff_add_of_disjoint`: if `x` and `y` are Witt vectors such that for every `n`
the `n`-th coefficient of `x` or of `y` is `0`, then the coefficients of `x + y`
are just `x.coeff n + y.coeff n`.
## References
* [Hazewinkel, *Witt Vectors*][Haze09]
* [Commelin and Lewis, *Formalizing the Ring of Witt Vectors*][CL21]
-/
variable {p : ℕ} [hp : Fact p.Prime] (n : ℕ) {R : Type*} [CommRing R]
-- type as `\bbW`
local notation "𝕎" => WittVector p
namespace WittVector
open MvPolynomial
open scoped Classical
noncomputable section
section
/-- `WittVector.select P x`, for a predicate `P : ℕ → Prop` is the Witt vector
whose `n`-th coefficient is `x.coeff n` if `P n` is true, and `0` otherwise.
-/
def select (P : ℕ → Prop) (x : 𝕎 R) : 𝕎 R :=
mk p fun n => if P n then x.coeff n else 0
#align witt_vector.select WittVector.select
section Select
variable (P : ℕ → Prop)
/-- The polynomial that witnesses that `WittVector.select` is a polynomial function.
`selectPoly n` is `X n` if `P n` holds, and `0` otherwise. -/
def selectPoly (n : ℕ) : MvPolynomial ℕ ℤ :=
if P n then X n else 0
#align witt_vector.select_poly WittVector.selectPoly
theorem coeff_select (x : 𝕎 R) (n : ℕ) :
(select P x).coeff n = aeval x.coeff (selectPoly P n) := by
dsimp [select, selectPoly]
split_ifs with hi
· rw [aeval_X, mk]; simp only [hi]; rfl
· rw [AlgHom.map_zero, mk]; simp only [hi]; rfl
#align witt_vector.coeff_select WittVector.coeff_select
-- Porting note: replaced `@[is_poly]` with `instance`. Made the argument `P` implicit in doing so.
instance select_isPoly {P : ℕ → Prop} : IsPoly p fun _ _ x => select P x := by
use selectPoly P
rintro R _Rcr x
funext i
apply coeff_select
#align witt_vector.select_is_poly WittVector.select_isPoly
theorem select_add_select_not : ∀ x : 𝕎 R, select P x + select (fun i => ¬P i) x = x := by
-- Porting note: TC search was insufficient to find this instance, even though all required
-- instances exist. See zulip: [https://leanprover.zulipchat.com/#narrow/stream/287929-mathlib4/topic/WittVector.20saga/near/370073526]
have : IsPoly p fun {R} [CommRing R] x ↦ select P x + select (fun i ↦ ¬P i) x :=
IsPoly₂.diag (hf := IsPoly₂.comp)
ghost_calc x
intro n
simp only [RingHom.map_add]
suffices
(bind₁ (selectPoly P)) (wittPolynomial p ℤ n) +
(bind₁ (selectPoly fun i => ¬P i)) (wittPolynomial p ℤ n) =
wittPolynomial p ℤ n by
apply_fun aeval x.coeff at this
simpa only [AlgHom.map_add, aeval_bind₁, ← coeff_select]
simp only [wittPolynomial_eq_sum_C_mul_X_pow, selectPoly, AlgHom.map_sum, AlgHom.map_pow,
AlgHom.map_mul, bind₁_X_right, bind₁_C_right, ← Finset.sum_add_distrib, ← mul_add]
apply Finset.sum_congr rfl
refine fun m _ => mul_eq_mul_left_iff.mpr (Or.inl ?_)
rw [ite_pow, zero_pow (pow_ne_zero _ hp.out.ne_zero)]
by_cases Pm : P m
· rw [if_pos Pm, if_neg $ not_not_intro Pm, zero_pow Fin.size_pos'.ne', add_zero]
· rwa [if_neg Pm, if_pos, zero_add]
#align witt_vector.select_add_select_not WittVector.select_add_select_not
theorem coeff_add_of_disjoint (x y : 𝕎 R) (h : ∀ n, x.coeff n = 0 ∨ y.coeff n = 0) :
(x + y).coeff n = x.coeff n + y.coeff n := by
let P : ℕ → Prop := fun n => y.coeff n = 0
haveI : DecidablePred P := Classical.decPred P
set z := mk p fun n => if P n then x.coeff n else y.coeff n
have hx : select P z = x := by
ext1 n; rw [select, coeff_mk, coeff_mk]
split_ifs with hn
· rfl
· rw [(h n).resolve_right hn]
have hy : select (fun i => ¬P i) z = y := by
ext1 n; rw [select, coeff_mk, coeff_mk]
split_ifs with hn
· exact hn.symm
· rfl
calc
(x + y).coeff n = z.coeff n := by rw [← hx, ← hy, select_add_select_not P z]
_ = x.coeff n + y.coeff n := by
simp only [z, mk.eq_1]
split_ifs with y0
· rw [y0, add_zero]
· rw [h n |>.resolve_right y0, zero_add]
#align witt_vector.coeff_add_of_disjoint WittVector.coeff_add_of_disjoint
end Select
/-- `WittVector.init n x` is the Witt vector of which the first `n` coefficients are those from `x`
and all other coefficients are `0`.
See `WittVector.tail` for the complementary part.
-/
def init (n : ℕ) : 𝕎 R → 𝕎 R :=
select fun i => i < n
#align witt_vector.init WittVector.init
/-- `WittVector.tail n x` is the Witt vector of which the first `n` coefficients are `0`
and all other coefficients are those from `x`.
See `WittVector.init` for the complementary part. -/
def tail (n : ℕ) : 𝕎 R → 𝕎 R :=
select fun i => n ≤ i
#align witt_vector.tail WittVector.tail
@[simp]
theorem init_add_tail (x : 𝕎 R) (n : ℕ) : init n x + tail n x = x := by
simp only [init, tail, ← not_lt, select_add_select_not]
#align witt_vector.init_add_tail WittVector.init_add_tail
end
/--
`init_ring` is an auxiliary tactic that discharges goals factoring `init` over ring operations.
-/
syntax (name := initRing) "init_ring" (" using " term)? : tactic
-- Porting note: this tactic requires that we turn hygiene off (note the free `n`).
-- TODO: make this tactic hygienic.
open Lean Elab Tactic in
elab_rules : tactic
| `(tactic| init_ring $[ using $a:term]?) => withMainContext <| set_option hygiene false in do
evalTactic <|← `(tactic|(
rw [WittVector.ext_iff]
intro i
simp only [WittVector.init, WittVector.select, WittVector.coeff_mk]
split_ifs with hi <;> try {rfl}
))
if let some e := a then
evalTactic <|← `(tactic|(
simp only [WittVector.add_coeff, WittVector.mul_coeff, WittVector.neg_coeff,
WittVector.sub_coeff, WittVector.nsmul_coeff, WittVector.zsmul_coeff, WittVector.pow_coeff]
apply MvPolynomial.eval₂Hom_congr' (RingHom.ext_int _ _) _ rfl
rintro ⟨b, k⟩ h -
replace h := $e:term p _ h
simp only [Finset.mem_range, Finset.mem_product, true_and, Finset.mem_univ] at h
have hk : k < n := by linarith
fin_cases b <;> simp only [Function.uncurry, Matrix.cons_val_zero, Matrix.head_cons,
WittVector.coeff_mk, Matrix.cons_val_one, WittVector.mk, Fin.mk_zero, Matrix.cons_val',
Matrix.empty_val', Matrix.cons_val_fin_one, Matrix.cons_val_zero,
hk, if_true]
))
-- Porting note: `by init_ring` should suffice; this patches over an issue with `split_ifs`.
-- See zulip: [https://leanprover.zulipchat.com/#narrow/stream/287929-mathlib4/topic/.60split_ifs.60.20boxes.20itself.20into.20a.20corner]
@[simp]
theorem init_init (x : 𝕎 R) (n : ℕ) : init n (init n x) = init n x := by
rw [ext_iff]
intro i
simp only [WittVector.init, WittVector.select, WittVector.coeff_mk]
by_cases hi : i < n <;> simp [hi]
#align witt_vector.init_init WittVector.init_init
| Mathlib/RingTheory/WittVector/InitTail.lean | 201 | 202 | theorem init_add (x y : 𝕎 R) (n : ℕ) : init n (x + y) = init n (init n x + init n y) := by |
init_ring using wittAdd_vars
|
/-
Copyright (c) 2020 Yury G. Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury G. Kudryashov
-/
import Mathlib.Order.Filter.Basic
import Mathlib.Data.Set.Countable
#align_import order.filter.countable_Inter from "leanprover-community/mathlib"@"b9e46fe101fc897fb2e7edaf0bf1f09ea49eb81a"
/-!
# Filters with countable intersection property
In this file we define `CountableInterFilter` to be the class of filters with the following
property: for any countable collection of sets `s ∈ l` their intersection belongs to `l` as well.
Two main examples are the `residual` filter defined in `Mathlib.Topology.GDelta` and
the `MeasureTheory.ae` filter defined in `Mathlib/MeasureTheory.OuterMeasure/AE`.
We reformulate the definition in terms of indexed intersection and in terms of `Filter.Eventually`
and provide instances for some basic constructions (`⊥`, `⊤`, `Filter.principal`, `Filter.map`,
`Filter.comap`, `Inf.inf`). We also provide a custom constructor `Filter.ofCountableInter`
that deduces two axioms of a `Filter` from the countable intersection property.
Note that there also exists a typeclass `CardinalInterFilter`, and thus an alternative spelling of
`CountableInterFilter` as `CardinalInterFilter l (aleph 1)`. The former (defined here) is the
preferred spelling; it has the advantage of not requiring the user to import the theory ordinals.
## Tags
filter, countable
-/
open Set Filter
open Filter
variable {ι : Sort*} {α β : Type*}
/-- A filter `l` has the countable intersection property if for any countable collection
of sets `s ∈ l` their intersection belongs to `l` as well. -/
class CountableInterFilter (l : Filter α) : Prop where
/-- For a countable collection of sets `s ∈ l`, their intersection belongs to `l` as well. -/
countable_sInter_mem : ∀ S : Set (Set α), S.Countable → (∀ s ∈ S, s ∈ l) → ⋂₀ S ∈ l
#align countable_Inter_filter CountableInterFilter
variable {l : Filter α} [CountableInterFilter l]
theorem countable_sInter_mem {S : Set (Set α)} (hSc : S.Countable) : ⋂₀ S ∈ l ↔ ∀ s ∈ S, s ∈ l :=
⟨fun hS _s hs => mem_of_superset hS (sInter_subset_of_mem hs),
CountableInterFilter.countable_sInter_mem _ hSc⟩
#align countable_sInter_mem countable_sInter_mem
theorem countable_iInter_mem [Countable ι] {s : ι → Set α} : (⋂ i, s i) ∈ l ↔ ∀ i, s i ∈ l :=
sInter_range s ▸ (countable_sInter_mem (countable_range _)).trans forall_mem_range
#align countable_Inter_mem countable_iInter_mem
theorem countable_bInter_mem {ι : Type*} {S : Set ι} (hS : S.Countable) {s : ∀ i ∈ S, Set α} :
(⋂ i, ⋂ hi : i ∈ S, s i ‹_›) ∈ l ↔ ∀ i, ∀ hi : i ∈ S, s i ‹_› ∈ l := by
rw [biInter_eq_iInter]
haveI := hS.toEncodable
exact countable_iInter_mem.trans Subtype.forall
#align countable_bInter_mem countable_bInter_mem
theorem eventually_countable_forall [Countable ι] {p : α → ι → Prop} :
(∀ᶠ x in l, ∀ i, p x i) ↔ ∀ i, ∀ᶠ x in l, p x i := by
simpa only [Filter.Eventually, setOf_forall] using
@countable_iInter_mem _ _ l _ _ fun i => { x | p x i }
#align eventually_countable_forall eventually_countable_forall
theorem eventually_countable_ball {ι : Type*} {S : Set ι} (hS : S.Countable)
{p : α → ∀ i ∈ S, Prop} :
(∀ᶠ x in l, ∀ i hi, p x i hi) ↔ ∀ i hi, ∀ᶠ x in l, p x i hi := by
simpa only [Filter.Eventually, setOf_forall] using
@countable_bInter_mem _ l _ _ _ hS fun i hi => { x | p x i hi }
#align eventually_countable_ball eventually_countable_ball
theorem EventuallyLE.countable_iUnion [Countable ι] {s t : ι → Set α} (h : ∀ i, s i ≤ᶠ[l] t i) :
⋃ i, s i ≤ᶠ[l] ⋃ i, t i :=
(eventually_countable_forall.2 h).mono fun _ hst hs => mem_iUnion.2 <| (mem_iUnion.1 hs).imp hst
#align eventually_le.countable_Union EventuallyLE.countable_iUnion
theorem EventuallyEq.countable_iUnion [Countable ι] {s t : ι → Set α} (h : ∀ i, s i =ᶠ[l] t i) :
⋃ i, s i =ᶠ[l] ⋃ i, t i :=
(EventuallyLE.countable_iUnion fun i => (h i).le).antisymm
(EventuallyLE.countable_iUnion fun i => (h i).symm.le)
#align eventually_eq.countable_Union EventuallyEq.countable_iUnion
theorem EventuallyLE.countable_bUnion {ι : Type*} {S : Set ι} (hS : S.Countable)
{s t : ∀ i ∈ S, Set α} (h : ∀ i hi, s i hi ≤ᶠ[l] t i hi) :
⋃ i ∈ S, s i ‹_› ≤ᶠ[l] ⋃ i ∈ S, t i ‹_› := by
simp only [biUnion_eq_iUnion]
haveI := hS.toEncodable
exact EventuallyLE.countable_iUnion fun i => h i i.2
#align eventually_le.countable_bUnion EventuallyLE.countable_bUnion
theorem EventuallyEq.countable_bUnion {ι : Type*} {S : Set ι} (hS : S.Countable)
{s t : ∀ i ∈ S, Set α} (h : ∀ i hi, s i hi =ᶠ[l] t i hi) :
⋃ i ∈ S, s i ‹_› =ᶠ[l] ⋃ i ∈ S, t i ‹_› :=
(EventuallyLE.countable_bUnion hS fun i hi => (h i hi).le).antisymm
(EventuallyLE.countable_bUnion hS fun i hi => (h i hi).symm.le)
#align eventually_eq.countable_bUnion EventuallyEq.countable_bUnion
theorem EventuallyLE.countable_iInter [Countable ι] {s t : ι → Set α} (h : ∀ i, s i ≤ᶠ[l] t i) :
⋂ i, s i ≤ᶠ[l] ⋂ i, t i :=
(eventually_countable_forall.2 h).mono fun _ hst hs =>
mem_iInter.2 fun i => hst _ (mem_iInter.1 hs i)
#align eventually_le.countable_Inter EventuallyLE.countable_iInter
theorem EventuallyEq.countable_iInter [Countable ι] {s t : ι → Set α} (h : ∀ i, s i =ᶠ[l] t i) :
⋂ i, s i =ᶠ[l] ⋂ i, t i :=
(EventuallyLE.countable_iInter fun i => (h i).le).antisymm
(EventuallyLE.countable_iInter fun i => (h i).symm.le)
#align eventually_eq.countable_Inter EventuallyEq.countable_iInter
theorem EventuallyLE.countable_bInter {ι : Type*} {S : Set ι} (hS : S.Countable)
{s t : ∀ i ∈ S, Set α} (h : ∀ i hi, s i hi ≤ᶠ[l] t i hi) :
⋂ i ∈ S, s i ‹_› ≤ᶠ[l] ⋂ i ∈ S, t i ‹_› := by
simp only [biInter_eq_iInter]
haveI := hS.toEncodable
exact EventuallyLE.countable_iInter fun i => h i i.2
#align eventually_le.countable_bInter EventuallyLE.countable_bInter
theorem EventuallyEq.countable_bInter {ι : Type*} {S : Set ι} (hS : S.Countable)
{s t : ∀ i ∈ S, Set α} (h : ∀ i hi, s i hi =ᶠ[l] t i hi) :
⋂ i ∈ S, s i ‹_› =ᶠ[l] ⋂ i ∈ S, t i ‹_› :=
(EventuallyLE.countable_bInter hS fun i hi => (h i hi).le).antisymm
(EventuallyLE.countable_bInter hS fun i hi => (h i hi).symm.le)
#align eventually_eq.countable_bInter EventuallyEq.countable_bInter
/-- Construct a filter with countable intersection property. This constructor deduces
`Filter.univ_sets` and `Filter.inter_sets` from the countable intersection property. -/
def Filter.ofCountableInter (l : Set (Set α))
(hl : ∀ S : Set (Set α), S.Countable → S ⊆ l → ⋂₀ S ∈ l)
(h_mono : ∀ s t, s ∈ l → s ⊆ t → t ∈ l) : Filter α where
sets := l
univ_sets := @sInter_empty α ▸ hl _ countable_empty (empty_subset _)
sets_of_superset := h_mono _ _
inter_sets {s t} hs ht := sInter_pair s t ▸
hl _ ((countable_singleton _).insert _) (insert_subset_iff.2 ⟨hs, singleton_subset_iff.2 ht⟩)
#align filter.of_countable_Inter Filter.ofCountableInter
instance Filter.countableInter_ofCountableInter (l : Set (Set α))
(hl : ∀ S : Set (Set α), S.Countable → S ⊆ l → ⋂₀ S ∈ l)
(h_mono : ∀ s t, s ∈ l → s ⊆ t → t ∈ l) :
CountableInterFilter (Filter.ofCountableInter l hl h_mono) :=
⟨hl⟩
#align filter.countable_Inter_of_countable_Inter Filter.countableInter_ofCountableInter
@[simp]
theorem Filter.mem_ofCountableInter {l : Set (Set α)}
(hl : ∀ S : Set (Set α), S.Countable → S ⊆ l → ⋂₀ S ∈ l) (h_mono : ∀ s t, s ∈ l → s ⊆ t → t ∈ l)
{s : Set α} : s ∈ Filter.ofCountableInter l hl h_mono ↔ s ∈ l :=
Iff.rfl
#align filter.mem_of_countable_Inter Filter.mem_ofCountableInter
/-- Construct a filter with countable intersection property.
Similarly to `Filter.comk`, a set belongs to this filter if its complement satisfies the property.
Similarly to `Filter.ofCountableInter`,
this constructor deduces some properties from the countable intersection property
which becomes the countable union property because we take complements of all sets. -/
def Filter.ofCountableUnion (l : Set (Set α))
(hUnion : ∀ S : Set (Set α), S.Countable → (∀ s ∈ S, s ∈ l) → ⋃₀ S ∈ l)
(hmono : ∀ t ∈ l, ∀ s ⊆ t, s ∈ l) : Filter α := by
refine .ofCountableInter {s | sᶜ ∈ l} (fun S hSc hSp ↦ ?_) fun s t ht hsub ↦ ?_
· rw [mem_setOf_eq, compl_sInter]
apply hUnion (compl '' S) (hSc.image _)
intro s hs
rw [mem_image] at hs
rcases hs with ⟨t, ht, rfl⟩
apply hSp ht
· rw [mem_setOf_eq]
rw [← compl_subset_compl] at hsub
exact hmono sᶜ ht tᶜ hsub
instance Filter.countableInter_ofCountableUnion (l : Set (Set α)) (h₁ h₂) :
CountableInterFilter (Filter.ofCountableUnion l h₁ h₂) :=
countableInter_ofCountableInter ..
@[simp]
theorem Filter.mem_ofCountableUnion {l : Set (Set α)} {hunion hmono s} :
s ∈ ofCountableUnion l hunion hmono ↔ l sᶜ :=
Iff.rfl
instance countableInterFilter_principal (s : Set α) : CountableInterFilter (𝓟 s) :=
⟨fun _ _ hS => subset_sInter hS⟩
#align countable_Inter_filter_principal countableInterFilter_principal
instance countableInterFilter_bot : CountableInterFilter (⊥ : Filter α) := by
rw [← principal_empty]
apply countableInterFilter_principal
#align countable_Inter_filter_bot countableInterFilter_bot
instance countableInterFilter_top : CountableInterFilter (⊤ : Filter α) := by
rw [← principal_univ]
apply countableInterFilter_principal
#align countable_Inter_filter_top countableInterFilter_top
instance (l : Filter β) [CountableInterFilter l] (f : α → β) :
CountableInterFilter (comap f l) := by
refine ⟨fun S hSc hS => ?_⟩
choose! t htl ht using hS
have : (⋂ s ∈ S, t s) ∈ l := (countable_bInter_mem hSc).2 htl
refine ⟨_, this, ?_⟩
simpa [preimage_iInter] using iInter₂_mono ht
instance (l : Filter α) [CountableInterFilter l] (f : α → β) : CountableInterFilter (map f l) := by
refine ⟨fun S hSc hS => ?_⟩
simp only [mem_map, sInter_eq_biInter, preimage_iInter₂] at hS ⊢
exact (countable_bInter_mem hSc).2 hS
/-- Infimum of two `CountableInterFilter`s is a `CountableInterFilter`. This is useful, e.g.,
to automatically get an instance for `residual α ⊓ 𝓟 s`. -/
instance countableInterFilter_inf (l₁ l₂ : Filter α) [CountableInterFilter l₁]
[CountableInterFilter l₂] : CountableInterFilter (l₁ ⊓ l₂) := by
refine ⟨fun S hSc hS => ?_⟩
choose s hs t ht hst using hS
replace hs : (⋂ i ∈ S, s i ‹_›) ∈ l₁ := (countable_bInter_mem hSc).2 hs
replace ht : (⋂ i ∈ S, t i ‹_›) ∈ l₂ := (countable_bInter_mem hSc).2 ht
refine mem_of_superset (inter_mem_inf hs ht) (subset_sInter fun i hi => ?_)
rw [hst i hi]
apply inter_subset_inter <;> exact iInter_subset_of_subset i (iInter_subset _ _)
#align countable_Inter_filter_inf countableInterFilter_inf
/-- Supremum of two `CountableInterFilter`s is a `CountableInterFilter`. -/
instance countableInterFilter_sup (l₁ l₂ : Filter α) [CountableInterFilter l₁]
[CountableInterFilter l₂] : CountableInterFilter (l₁ ⊔ l₂) := by
refine ⟨fun S hSc hS => ⟨?_, ?_⟩⟩ <;> refine (countable_sInter_mem hSc).2 fun s hs => ?_
exacts [(hS s hs).1, (hS s hs).2]
#align countable_Inter_filter_sup countableInterFilter_sup
namespace Filter
variable (g : Set (Set α))
/-- `Filter.CountableGenerateSets g` is the (sets of the)
greatest `countableInterFilter` containing `g`. -/
inductive CountableGenerateSets : Set α → Prop
| basic {s : Set α} : s ∈ g → CountableGenerateSets s
| univ : CountableGenerateSets univ
| superset {s t : Set α} : CountableGenerateSets s → s ⊆ t → CountableGenerateSets t
| sInter {S : Set (Set α)} :
S.Countable → (∀ s ∈ S, CountableGenerateSets s) → CountableGenerateSets (⋂₀ S)
#align filter.countable_generate_sets Filter.CountableGenerateSets
/-- `Filter.countableGenerate g` is the greatest `countableInterFilter` containing `g`. -/
def countableGenerate : Filter α :=
ofCountableInter (CountableGenerateSets g) (fun _ => CountableGenerateSets.sInter) fun _ _ =>
CountableGenerateSets.superset
--deriving CountableInterFilter
#align filter.countable_generate Filter.countableGenerate
-- Porting note: could not de derived
instance : CountableInterFilter (countableGenerate g) := by
delta countableGenerate; infer_instance
variable {g}
/-- A set is in the `countableInterFilter` generated by `g` if and only if
it contains a countable intersection of elements of `g`. -/
theorem mem_countableGenerate_iff {s : Set α} :
s ∈ countableGenerate g ↔ ∃ S : Set (Set α), S ⊆ g ∧ S.Countable ∧ ⋂₀ S ⊆ s := by
constructor <;> intro h
· induction' h with s hs s t _ st ih S Sct _ ih
· exact ⟨{s}, by simp [hs, subset_refl]⟩
· exact ⟨∅, by simp⟩
· refine Exists.imp (fun S => ?_) ih
tauto
choose T Tg Tct hT using ih
refine ⟨⋃ (s) (H : s ∈ S), T s H, by simpa, Sct.biUnion Tct, ?_⟩
apply subset_sInter
intro s H
exact subset_trans (sInter_subset_sInter (subset_iUnion₂ s H)) (hT s H)
rcases h with ⟨S, Sg, Sct, hS⟩
refine mem_of_superset ((countable_sInter_mem Sct).mpr ?_) hS
intro s H
exact CountableGenerateSets.basic (Sg H)
#align filter.mem_countable_generate_iff Filter.mem_countableGenerate_iff
theorem le_countableGenerate_iff_of_countableInterFilter {f : Filter α} [CountableInterFilter f] :
f ≤ countableGenerate g ↔ g ⊆ f.sets := by
constructor <;> intro h
· exact subset_trans (fun s => CountableGenerateSets.basic) h
intro s hs
induction' hs with s hs s t _ st ih S Sct _ ih
· exact h hs
· exact univ_mem
· exact mem_of_superset ih st
exact (countable_sInter_mem Sct).mpr ih
#align filter.le_countable_generate_iff_of_countable_Inter_filter Filter.le_countableGenerate_iff_of_countableInterFilter
variable (g)
/-- `countableGenerate g` is the greatest `countableInterFilter` containing `g`. -/
| Mathlib/Order/Filter/CountableInter.lean | 295 | 299 | theorem countableGenerate_isGreatest :
IsGreatest { f : Filter α | CountableInterFilter f ∧ g ⊆ f.sets } (countableGenerate g) := by |
refine ⟨⟨inferInstance, fun s => CountableGenerateSets.basic⟩, ?_⟩
rintro f ⟨fct, hf⟩
rwa [@le_countableGenerate_iff_of_countableInterFilter _ _ _ fct]
|
/-
Copyright (c) 2020 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov
-/
import Mathlib.Algebra.Group.Prod
import Mathlib.Order.Cover
#align_import algebra.support from "leanprover-community/mathlib"@"29cb56a7b35f72758b05a30490e1f10bd62c35c1"
/-!
# Support of a function
In this file we define `Function.support f = {x | f x ≠ 0}` and prove its basic properties.
We also define `Function.mulSupport f = {x | f x ≠ 1}`.
-/
assert_not_exists MonoidWithZero
open Set
namespace Function
variable {α β A B M N P G : Type*}
section One
variable [One M] [One N] [One P]
/-- `mulSupport` of a function is the set of points `x` such that `f x ≠ 1`. -/
@[to_additive "`support` of a function is the set of points `x` such that `f x ≠ 0`."]
def mulSupport (f : α → M) : Set α := {x | f x ≠ 1}
#align function.mul_support Function.mulSupport
#align function.support Function.support
@[to_additive]
theorem mulSupport_eq_preimage (f : α → M) : mulSupport f = f ⁻¹' {1}ᶜ :=
rfl
#align function.mul_support_eq_preimage Function.mulSupport_eq_preimage
#align function.support_eq_preimage Function.support_eq_preimage
@[to_additive]
theorem nmem_mulSupport {f : α → M} {x : α} : x ∉ mulSupport f ↔ f x = 1 :=
not_not
#align function.nmem_mul_support Function.nmem_mulSupport
#align function.nmem_support Function.nmem_support
@[to_additive]
theorem compl_mulSupport {f : α → M} : (mulSupport f)ᶜ = { x | f x = 1 } :=
ext fun _ => nmem_mulSupport
#align function.compl_mul_support Function.compl_mulSupport
#align function.compl_support Function.compl_support
@[to_additive (attr := simp)]
theorem mem_mulSupport {f : α → M} {x : α} : x ∈ mulSupport f ↔ f x ≠ 1 :=
Iff.rfl
#align function.mem_mul_support Function.mem_mulSupport
#align function.mem_support Function.mem_support
@[to_additive (attr := simp)]
theorem mulSupport_subset_iff {f : α → M} {s : Set α} : mulSupport f ⊆ s ↔ ∀ x, f x ≠ 1 → x ∈ s :=
Iff.rfl
#align function.mul_support_subset_iff Function.mulSupport_subset_iff
#align function.support_subset_iff Function.support_subset_iff
@[to_additive]
theorem mulSupport_subset_iff' {f : α → M} {s : Set α} :
mulSupport f ⊆ s ↔ ∀ x ∉ s, f x = 1 :=
forall_congr' fun _ => not_imp_comm
#align function.mul_support_subset_iff' Function.mulSupport_subset_iff'
#align function.support_subset_iff' Function.support_subset_iff'
@[to_additive]
theorem mulSupport_eq_iff {f : α → M} {s : Set α} :
mulSupport f = s ↔ (∀ x, x ∈ s → f x ≠ 1) ∧ ∀ x, x ∉ s → f x = 1 := by
simp (config := { contextual := true }) only [ext_iff, mem_mulSupport, ne_eq, iff_def,
not_imp_comm, and_comm, forall_and]
#align function.mul_support_eq_iff Function.mulSupport_eq_iff
#align function.support_eq_iff Function.support_eq_iff
@[to_additive]
theorem ext_iff_mulSupport {f g : α → M} :
f = g ↔ f.mulSupport = g.mulSupport ∧ ∀ x ∈ f.mulSupport, f x = g x :=
⟨fun h ↦ h ▸ ⟨rfl, fun _ _ ↦ rfl⟩, fun ⟨h₁, h₂⟩ ↦ funext fun x ↦ by
if hx : x ∈ f.mulSupport then exact h₂ x hx
else rw [nmem_mulSupport.1 hx, nmem_mulSupport.1 (mt (Set.ext_iff.1 h₁ x).2 hx)]⟩
@[to_additive]
theorem mulSupport_update_of_ne_one [DecidableEq α] (f : α → M) (x : α) {y : M} (hy : y ≠ 1) :
mulSupport (update f x y) = insert x (mulSupport f) := by
ext a; rcases eq_or_ne a x with rfl | hne <;> simp [*]
@[to_additive]
theorem mulSupport_update_one [DecidableEq α] (f : α → M) (x : α) :
mulSupport (update f x 1) = mulSupport f \ {x} := by
ext a; rcases eq_or_ne a x with rfl | hne <;> simp [*]
@[to_additive]
| Mathlib/Algebra/Group/Support.lean | 98 | 100 | theorem mulSupport_update_eq_ite [DecidableEq α] [DecidableEq M] (f : α → M) (x : α) (y : M) :
mulSupport (update f x y) = if y = 1 then mulSupport f \ {x} else insert x (mulSupport f) := by |
rcases eq_or_ne y 1 with rfl | hy <;> simp [mulSupport_update_one, mulSupport_update_of_ne_one, *]
|
/-
Copyright (c) 2020 Scott Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Scott Morrison
-/
import Mathlib.Algebra.MvPolynomial.PDeriv
import Mathlib.Algebra.Polynomial.AlgebraMap
import Mathlib.Algebra.Polynomial.Derivative
import Mathlib.Data.Nat.Choose.Sum
import Mathlib.LinearAlgebra.LinearIndependent
import Mathlib.RingTheory.Polynomial.Pochhammer
#align_import ring_theory.polynomial.bernstein from "leanprover-community/mathlib"@"bbeb185db4ccee8ed07dc48449414ebfa39cb821"
/-!
# Bernstein polynomials
The definition of the Bernstein polynomials
```
bernsteinPolynomial (R : Type*) [CommRing R] (n ν : ℕ) : R[X] :=
(choose n ν) * X^ν * (1 - X)^(n - ν)
```
and the fact that for `ν : fin (n+1)` these are linearly independent over `ℚ`.
We prove the basic identities
* `(Finset.range (n + 1)).sum (fun ν ↦ bernsteinPolynomial R n ν) = 1`
* `(Finset.range (n + 1)).sum (fun ν ↦ ν • bernsteinPolynomial R n ν) = n • X`
* `(Finset.range (n + 1)).sum (fun ν ↦ (ν * (ν-1)) • bernsteinPolynomial R n ν) = (n * (n-1)) • X^2`
## Notes
See also `Mathlib.Analysis.SpecialFunctions.Bernstein`, which defines the Bernstein approximations
of a continuous function `f : C([0,1], ℝ)`, and shows that these converge uniformly to `f`.
-/
noncomputable section
open Nat (choose)
open Polynomial (X)
open scoped Polynomial
variable (R : Type*) [CommRing R]
/-- `bernsteinPolynomial R n ν` is `(choose n ν) * X^ν * (1 - X)^(n - ν)`.
Although the coefficients are integers, it is convenient to work over an arbitrary commutative ring.
-/
def bernsteinPolynomial (n ν : ℕ) : R[X] :=
(choose n ν : R[X]) * X ^ ν * (1 - X) ^ (n - ν)
#align bernstein_polynomial bernsteinPolynomial
example : bernsteinPolynomial ℤ 3 2 = 3 * X ^ 2 - 3 * X ^ 3 := by
norm_num [bernsteinPolynomial, choose]
ring
namespace bernsteinPolynomial
theorem eq_zero_of_lt {n ν : ℕ} (h : n < ν) : bernsteinPolynomial R n ν = 0 := by
simp [bernsteinPolynomial, Nat.choose_eq_zero_of_lt h]
#align bernstein_polynomial.eq_zero_of_lt bernsteinPolynomial.eq_zero_of_lt
section
variable {R} {S : Type*} [CommRing S]
@[simp]
theorem map (f : R →+* S) (n ν : ℕ) :
(bernsteinPolynomial R n ν).map f = bernsteinPolynomial S n ν := by simp [bernsteinPolynomial]
#align bernstein_polynomial.map bernsteinPolynomial.map
end
theorem flip (n ν : ℕ) (h : ν ≤ n) :
(bernsteinPolynomial R n ν).comp (1 - X) = bernsteinPolynomial R n (n - ν) := by
simp [bernsteinPolynomial, h, tsub_tsub_assoc, mul_right_comm]
#align bernstein_polynomial.flip bernsteinPolynomial.flip
theorem flip' (n ν : ℕ) (h : ν ≤ n) :
bernsteinPolynomial R n ν = (bernsteinPolynomial R n (n - ν)).comp (1 - X) := by
simp [← flip _ _ _ h, Polynomial.comp_assoc]
#align bernstein_polynomial.flip' bernsteinPolynomial.flip'
theorem eval_at_0 (n ν : ℕ) : (bernsteinPolynomial R n ν).eval 0 = if ν = 0 then 1 else 0 := by
rw [bernsteinPolynomial]
split_ifs with h
· subst h; simp
· simp [zero_pow h]
#align bernstein_polynomial.eval_at_0 bernsteinPolynomial.eval_at_0
theorem eval_at_1 (n ν : ℕ) : (bernsteinPolynomial R n ν).eval 1 = if ν = n then 1 else 0 := by
rw [bernsteinPolynomial]
split_ifs with h
· subst h; simp
· obtain hνn | hnν := Ne.lt_or_lt h
· simp [zero_pow $ Nat.sub_ne_zero_of_lt hνn]
· simp [Nat.choose_eq_zero_of_lt hnν]
#align bernstein_polynomial.eval_at_1 bernsteinPolynomial.eval_at_1
theorem derivative_succ_aux (n ν : ℕ) :
Polynomial.derivative (bernsteinPolynomial R (n + 1) (ν + 1)) =
(n + 1) * (bernsteinPolynomial R n ν - bernsteinPolynomial R n (ν + 1)) := by
rw [bernsteinPolynomial]
suffices ((n + 1).choose (ν + 1) : R[X]) * ((↑(ν + 1 : ℕ) : R[X]) * X ^ ν) * (1 - X) ^ (n - ν) -
((n + 1).choose (ν + 1) : R[X]) * X ^ (ν + 1) * ((↑(n - ν) : R[X]) * (1 - X) ^ (n - ν - 1)) =
(↑(n + 1) : R[X]) * ((n.choose ν : R[X]) * X ^ ν * (1 - X) ^ (n - ν) -
(n.choose (ν + 1) : R[X]) * X ^ (ν + 1) * (1 - X) ^ (n - (ν + 1))) by
simpa [Polynomial.derivative_pow, ← sub_eq_add_neg, Nat.succ_sub_succ_eq_sub,
Polynomial.derivative_mul, Polynomial.derivative_natCast, zero_mul,
Nat.cast_add, algebraMap.coe_one, Polynomial.derivative_X, mul_one, zero_add,
Polynomial.derivative_sub, Polynomial.derivative_one, zero_sub, mul_neg, Nat.sub_zero,
bernsteinPolynomial, map_add, map_natCast, Nat.cast_one]
conv_rhs => rw [mul_sub]
-- We'll prove the two terms match up separately.
refine congr (congr_arg Sub.sub ?_) ?_
· simp only [← mul_assoc]
apply congr (congr_arg (· * ·) (congr (congr_arg (· * ·) _) rfl)) rfl
-- Now it's just about binomial coefficients
exact mod_cast congr_arg (fun m : ℕ => (m : R[X])) (Nat.succ_mul_choose_eq n ν).symm
· rw [← tsub_add_eq_tsub_tsub, ← mul_assoc, ← mul_assoc]; congr 1
rw [mul_comm, ← mul_assoc, ← mul_assoc]; congr 1
norm_cast
congr 1
convert (Nat.choose_mul_succ_eq n (ν + 1)).symm using 1
· -- Porting note: was
-- convert mul_comm _ _ using 2
-- simp
rw [mul_comm, Nat.succ_sub_succ_eq_sub]
· apply mul_comm
#align bernstein_polynomial.derivative_succ_aux bernsteinPolynomial.derivative_succ_aux
theorem derivative_succ (n ν : ℕ) : Polynomial.derivative (bernsteinPolynomial R n (ν + 1)) =
n * (bernsteinPolynomial R (n - 1) ν - bernsteinPolynomial R (n - 1) (ν + 1)) := by
cases n
· simp [bernsteinPolynomial]
· rw [Nat.cast_succ]; apply derivative_succ_aux
#align bernstein_polynomial.derivative_succ bernsteinPolynomial.derivative_succ
theorem derivative_zero (n : ℕ) :
Polynomial.derivative (bernsteinPolynomial R n 0) = -n * bernsteinPolynomial R (n - 1) 0 := by
simp [bernsteinPolynomial, Polynomial.derivative_pow]
#align bernstein_polynomial.derivative_zero bernsteinPolynomial.derivative_zero
theorem iterate_derivative_at_0_eq_zero_of_lt (n : ℕ) {ν k : ℕ} :
k < ν → (Polynomial.derivative^[k] (bernsteinPolynomial R n ν)).eval 0 = 0 := by
cases' ν with ν
· rintro ⟨⟩
· rw [Nat.lt_succ_iff]
induction' k with k ih generalizing n ν
· simp [eval_at_0]
· simp only [derivative_succ, Int.natCast_eq_zero, mul_eq_zero, Function.comp_apply,
Function.iterate_succ, Polynomial.iterate_derivative_sub,
Polynomial.iterate_derivative_natCast_mul, Polynomial.eval_mul, Polynomial.eval_natCast,
Polynomial.eval_sub]
intro h
apply mul_eq_zero_of_right
rw [ih _ _ (Nat.le_of_succ_le h), sub_zero]
convert ih _ _ (Nat.pred_le_pred h)
exact (Nat.succ_pred_eq_of_pos (k.succ_pos.trans_le h)).symm
#align bernstein_polynomial.iterate_derivative_at_0_eq_zero_of_lt bernsteinPolynomial.iterate_derivative_at_0_eq_zero_of_lt
@[simp]
theorem iterate_derivative_succ_at_0_eq_zero (n ν : ℕ) :
(Polynomial.derivative^[ν] (bernsteinPolynomial R n (ν + 1))).eval 0 = 0 :=
iterate_derivative_at_0_eq_zero_of_lt R n (lt_add_one ν)
#align bernstein_polynomial.iterate_derivative_succ_at_0_eq_zero bernsteinPolynomial.iterate_derivative_succ_at_0_eq_zero
open Polynomial
@[simp]
theorem iterate_derivative_at_0 (n ν : ℕ) :
(Polynomial.derivative^[ν] (bernsteinPolynomial R n ν)).eval 0 =
(ascPochhammer R ν).eval ((n - (ν - 1) : ℕ) : R) := by
by_cases h : ν ≤ n
· induction' ν with ν ih generalizing n
· simp [eval_at_0]
· have h' : ν ≤ n - 1 := le_tsub_of_add_le_right h
simp only [derivative_succ, ih (n - 1) h', iterate_derivative_succ_at_0_eq_zero,
Nat.succ_sub_succ_eq_sub, tsub_zero, sub_zero, iterate_derivative_sub,
iterate_derivative_natCast_mul, eval_one, eval_mul, eval_add, eval_sub, eval_X, eval_comp,
eval_natCast, Function.comp_apply, Function.iterate_succ, ascPochhammer_succ_left]
obtain rfl | h'' := ν.eq_zero_or_pos
· simp
· have : n - 1 - (ν - 1) = n - ν := by
rw [gt_iff_lt, ← Nat.succ_le_iff] at h''
rw [← tsub_add_eq_tsub_tsub, add_comm, tsub_add_cancel_of_le h'']
rw [this, ascPochhammer_eval_succ]
rw_mod_cast [tsub_add_cancel_of_le (h'.trans n.pred_le)]
· simp only [not_le] at h
rw [tsub_eq_zero_iff_le.mpr (Nat.le_sub_one_of_lt h), eq_zero_of_lt R h]
simp [pos_iff_ne_zero.mp (pos_of_gt h)]
#align bernstein_polynomial.iterate_derivative_at_0 bernsteinPolynomial.iterate_derivative_at_0
theorem iterate_derivative_at_0_ne_zero [CharZero R] (n ν : ℕ) (h : ν ≤ n) :
(Polynomial.derivative^[ν] (bernsteinPolynomial R n ν)).eval 0 ≠ 0 := by
simp only [Int.natCast_eq_zero, bernsteinPolynomial.iterate_derivative_at_0, Ne, Nat.cast_eq_zero]
simp only [← ascPochhammer_eval_cast]
norm_cast
apply ne_of_gt
obtain rfl | h' := Nat.eq_zero_or_pos ν
· simp
· rw [← Nat.succ_pred_eq_of_pos h'] at h
exact ascPochhammer_pos _ _ (tsub_pos_of_lt (Nat.lt_of_succ_le h))
#align bernstein_polynomial.iterate_derivative_at_0_ne_zero bernsteinPolynomial.iterate_derivative_at_0_ne_zero
/-!
Rather than redoing the work of evaluating the derivatives at 1,
we use the symmetry of the Bernstein polynomials.
-/
theorem iterate_derivative_at_1_eq_zero_of_lt (n : ℕ) {ν k : ℕ} :
k < n - ν → (Polynomial.derivative^[k] (bernsteinPolynomial R n ν)).eval 1 = 0 := by
intro w
rw [flip' _ _ _ (tsub_pos_iff_lt.mp (pos_of_gt w)).le]
simp [Polynomial.eval_comp, iterate_derivative_at_0_eq_zero_of_lt R n w]
#align bernstein_polynomial.iterate_derivative_at_1_eq_zero_of_lt bernsteinPolynomial.iterate_derivative_at_1_eq_zero_of_lt
@[simp]
theorem iterate_derivative_at_1 (n ν : ℕ) (h : ν ≤ n) :
(Polynomial.derivative^[n - ν] (bernsteinPolynomial R n ν)).eval 1 =
(-1) ^ (n - ν) * (ascPochhammer R (n - ν)).eval (ν + 1 : R) := by
rw [flip' _ _ _ h]
simp [Polynomial.eval_comp, h]
obtain rfl | h' := h.eq_or_lt
· simp
· norm_cast
congr
omega
#align bernstein_polynomial.iterate_derivative_at_1 bernsteinPolynomial.iterate_derivative_at_1
theorem iterate_derivative_at_1_ne_zero [CharZero R] (n ν : ℕ) (h : ν ≤ n) :
(Polynomial.derivative^[n - ν] (bernsteinPolynomial R n ν)).eval 1 ≠ 0 := by
rw [bernsteinPolynomial.iterate_derivative_at_1 _ _ _ h, Ne, neg_one_pow_mul_eq_zero_iff, ←
Nat.cast_succ, ← ascPochhammer_eval_cast, ← Nat.cast_zero, Nat.cast_inj]
exact (ascPochhammer_pos _ _ (Nat.succ_pos ν)).ne'
#align bernstein_polynomial.iterate_derivative_at_1_ne_zero bernsteinPolynomial.iterate_derivative_at_1_ne_zero
open Submodule
theorem linearIndependent_aux (n k : ℕ) (h : k ≤ n + 1) :
LinearIndependent ℚ fun ν : Fin k => bernsteinPolynomial ℚ n ν := by
induction' k with k ih
· apply linearIndependent_empty_type
· apply linearIndependent_fin_succ'.mpr
fconstructor
· exact ih (le_of_lt h)
· -- The actual work!
-- We show that the (n-k)-th derivative at 1 doesn't vanish,
-- but vanishes for everything in the span.
clear ih
simp only [Nat.succ_eq_add_one, add_le_add_iff_right] at h
simp only [Fin.val_last, Fin.init_def]
dsimp
apply not_mem_span_of_apply_not_mem_span_image (@Polynomial.derivative ℚ _ ^ (n - k))
-- Note: #8386 had to change `span_image` into `span_image _`
simp only [not_exists, not_and, Submodule.mem_map, Submodule.span_image _]
intro p m
apply_fun Polynomial.eval (1 : ℚ)
simp only [LinearMap.pow_apply]
-- The right hand side is nonzero,
-- so it will suffice to show the left hand side is always zero.
suffices (Polynomial.derivative^[n - k] p).eval 1 = 0 by
rw [this]
exact (iterate_derivative_at_1_ne_zero ℚ n k h).symm
refine span_induction m ?_ ?_ ?_ ?_
· simp
rintro ⟨a, w⟩; simp only [Fin.val_mk]
rw [iterate_derivative_at_1_eq_zero_of_lt ℚ n ((tsub_lt_tsub_iff_left_of_le h).mpr w)]
· simp
· intro x y hx hy; simp [hx, hy]
· intro a x h; simp [h]
#align bernstein_polynomial.linear_independent_aux bernsteinPolynomial.linearIndependent_aux
/-- The Bernstein polynomials are linearly independent.
We prove by induction that the collection of `bernsteinPolynomial n ν` for `ν = 0, ..., k`
are linearly independent.
The inductive step relies on the observation that the `(n-k)`-th derivative, evaluated at 1,
annihilates `bernsteinPolynomial n ν` for `ν < k`, but has a nonzero value at `ν = k`.
-/
theorem linearIndependent (n : ℕ) :
LinearIndependent ℚ fun ν : Fin (n + 1) => bernsteinPolynomial ℚ n ν :=
linearIndependent_aux n (n + 1) le_rfl
#align bernstein_polynomial.linear_independent bernsteinPolynomial.linearIndependent
theorem sum (n : ℕ) : (∑ ν ∈ Finset.range (n + 1), bernsteinPolynomial R n ν) = 1 :=
calc
(∑ ν ∈ Finset.range (n + 1), bernsteinPolynomial R n ν) = (X + (1 - X)) ^ n := by
rw [add_pow]
simp only [bernsteinPolynomial, mul_comm, mul_assoc, mul_left_comm]
_ = 1 := by simp
#align bernstein_polynomial.sum bernsteinPolynomial.sum
open Polynomial
open MvPolynomial hiding X
theorem sum_smul (n : ℕ) :
(∑ ν ∈ Finset.range (n + 1), ν • bernsteinPolynomial R n ν) = n • X := by
-- We calculate the `x`-derivative of `(x+y)^n`, evaluated at `y=(1-x)`,
-- either directly or by using the binomial theorem.
-- We'll work in `MvPolynomial Bool R`.
let x : MvPolynomial Bool R := MvPolynomial.X true
let y : MvPolynomial Bool R := MvPolynomial.X false
have pderiv_true_x : pderiv true x = 1 := by rw [pderiv_X]; rfl
have pderiv_true_y : pderiv true y = 0 := by rw [pderiv_X]; rfl
let e : Bool → R[X] := fun i => cond i X (1 - X)
-- Start with `(x+y)^n = (x+y)^n`,
-- take the `x`-derivative, evaluate at `x=X, y=1-X`, and multiply by `X`:
trans MvPolynomial.aeval e (pderiv true ((x + y) ^ n)) * X
-- On the left hand side we'll use the binomial theorem, then simplify.
· -- We first prepare a tedious rewrite:
have w : ∀ k : ℕ, k • bernsteinPolynomial R n k =
(k : R[X]) * Polynomial.X ^ (k - 1) * (1 - Polynomial.X) ^ (n - k) * (n.choose k : R[X]) *
Polynomial.X := by
rintro (_ | k)
· simp
· rw [bernsteinPolynomial]
simp only [← natCast_mul, Nat.succ_eq_add_one, Nat.add_succ_sub_one, add_zero, pow_succ]
push_cast
ring
rw [add_pow, map_sum (pderiv true), map_sum (MvPolynomial.aeval e), Finset.sum_mul]
-- Step inside the sum:
refine Finset.sum_congr rfl fun k _ => (w k).trans ?_
simp only [x, y, e, pderiv_true_x, pderiv_true_y, Algebra.id.smul_eq_mul, nsmul_eq_mul,
Bool.cond_true, Bool.cond_false, add_zero, mul_one, mul_zero, smul_zero, MvPolynomial.aeval_X,
MvPolynomial.pderiv_mul, Derivation.leibniz_pow, Derivation.map_natCast, map_natCast, map_pow,
map_mul]
· rw [(pderiv true).leibniz_pow, (pderiv true).map_add, pderiv_true_x, pderiv_true_y]
simp only [x, y, e, Algebra.id.smul_eq_mul, nsmul_eq_mul, map_natCast, map_pow, map_add,
map_mul, Bool.cond_true, Bool.cond_false, MvPolynomial.aeval_X, add_sub_cancel,
one_pow, add_zero, mul_one]
#align bernstein_polynomial.sum_smul bernsteinPolynomial.sum_smul
theorem sum_mul_smul (n : ℕ) :
(∑ ν ∈ Finset.range (n + 1), (ν * (ν - 1)) • bernsteinPolynomial R n ν) =
(n * (n - 1)) • X ^ 2 := by
-- We calculate the second `x`-derivative of `(x+y)^n`, evaluated at `y=(1-x)`,
-- either directly or by using the binomial theorem.
-- We'll work in `MvPolynomial Bool R`.
let x : MvPolynomial Bool R := MvPolynomial.X true
let y : MvPolynomial Bool R := MvPolynomial.X false
have pderiv_true_x : pderiv true x = 1 := by rw [pderiv_X]; rfl
have pderiv_true_y : pderiv true y = 0 := by rw [pderiv_X]; rfl
let e : Bool → R[X] := fun i => cond i X (1 - X)
-- Start with `(x+y)^n = (x+y)^n`,
-- take the second `x`-derivative, evaluate at `x=X, y=1-X`, and multiply by `X`:
trans MvPolynomial.aeval e (pderiv true (pderiv true ((x + y) ^ n))) * X ^ 2
-- On the left hand side we'll use the binomial theorem, then simplify.
· -- We first prepare a tedious rewrite:
have w : ∀ k : ℕ, (k * (k - 1)) • bernsteinPolynomial R n k =
(n.choose k : R[X]) * ((1 - Polynomial.X) ^ (n - k) *
((k : R[X]) * ((↑(k - 1) : R[X]) * Polynomial.X ^ (k - 1 - 1)))) * Polynomial.X ^ 2 := by
rintro (_ | _ | k)
· simp
· simp
· rw [bernsteinPolynomial]
simp only [← natCast_mul, Nat.succ_eq_add_one, Nat.add_succ_sub_one, add_zero, pow_succ]
push_cast
ring
rw [add_pow, map_sum (pderiv true), map_sum (pderiv true), map_sum (MvPolynomial.aeval e),
Finset.sum_mul]
-- Step inside the sum:
refine Finset.sum_congr rfl fun k _ => (w k).trans ?_
simp only [x, y, e, pderiv_true_x, pderiv_true_y, Algebra.id.smul_eq_mul, nsmul_eq_mul,
Bool.cond_true, Bool.cond_false, add_zero, zero_add, mul_zero, smul_zero, mul_one,
MvPolynomial.aeval_X, MvPolynomial.pderiv_X_self, MvPolynomial.pderiv_X_of_ne,
Derivation.leibniz_pow, Derivation.leibniz, Derivation.map_natCast, map_natCast, map_pow,
map_mul, map_add]
-- On the right hand side, we'll just simplify.
· simp only [x, y, e, pderiv_one, pderiv_mul, (pderiv _).leibniz_pow, (pderiv _).map_natCast,
(pderiv true).map_add, pderiv_true_x, pderiv_true_y, Algebra.id.smul_eq_mul, add_zero,
mul_one, Derivation.map_smul_of_tower, map_nsmul, map_pow, map_add, Bool.cond_true,
Bool.cond_false, MvPolynomial.aeval_X, add_sub_cancel, one_pow, smul_smul,
smul_one_mul]
#align bernstein_polynomial.sum_mul_smul bernsteinPolynomial.sum_mul_smul
/-- A certain linear combination of the previous three identities,
which we'll want later.
-/
| Mathlib/RingTheory/Polynomial/Bernstein.lean | 384 | 410 | theorem variance (n : ℕ) :
(∑ ν ∈ Finset.range (n + 1), (n • Polynomial.X - (ν : R[X])) ^ 2 * bernsteinPolynomial R n ν) =
n • Polynomial.X * ((1 : R[X]) - Polynomial.X) := by |
have p : ((((Finset.range (n + 1)).sum fun ν => (ν * (ν - 1)) • bernsteinPolynomial R n ν) +
(1 - (2 * n) • Polynomial.X) * (Finset.range (n + 1)).sum fun ν =>
ν • bernsteinPolynomial R n ν) + n ^ 2 • X ^ 2 *
(Finset.range (n + 1)).sum fun ν => bernsteinPolynomial R n ν) = _ :=
rfl
conv at p =>
lhs
rw [Finset.mul_sum, Finset.mul_sum, ← Finset.sum_add_distrib, ← Finset.sum_add_distrib]
simp only [← natCast_mul]
simp only [← mul_assoc]
simp only [← add_mul]
conv at p =>
rhs
rw [sum, sum_smul, sum_mul_smul, ← natCast_mul]
calc
_ = _ := Finset.sum_congr rfl fun k m => ?_
_ = _ := p
_ = _ := ?_
· congr 1; simp only [← natCast_mul, push_cast]
cases k <;> · simp; ring
· simp only [← natCast_mul, push_cast]
cases n
· simp
· simp; ring
|
/-
Copyright (c) 2018 Johan Commelin. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johan Commelin
-/
import Mathlib.Algebra.Algebra.Defs
import Mathlib.Algebra.Order.BigOperators.Ring.Finset
import Mathlib.Algebra.Order.Field.Canonical.Basic
import Mathlib.Algebra.Order.Nonneg.Field
import Mathlib.Algebra.Order.Nonneg.Floor
import Mathlib.Data.Real.Pointwise
import Mathlib.Order.ConditionallyCompleteLattice.Group
import Mathlib.Tactic.GCongr.Core
#align_import data.real.nnreal from "leanprover-community/mathlib"@"b1abe23ae96fef89ad30d9f4362c307f72a55010"
/-!
# Nonnegative real numbers
In this file we define `NNReal` (notation: `ℝ≥0`) to be the type of non-negative real numbers,
a.k.a. the interval `[0, ∞)`. We also define the following operations and structures on `ℝ≥0`:
* the order on `ℝ≥0` is the restriction of the order on `ℝ`; these relations define a conditionally
complete linear order with a bottom element, `ConditionallyCompleteLinearOrderBot`;
* `a + b` and `a * b` are the restrictions of addition and multiplication of real numbers to `ℝ≥0`;
these operations together with `0 = ⟨0, _⟩` and `1 = ⟨1, _⟩` turn `ℝ≥0` into a conditionally
complete linear ordered archimedean commutative semifield; we have no typeclass for this in
`mathlib` yet, so we define the following instances instead:
- `LinearOrderedSemiring ℝ≥0`;
- `OrderedCommSemiring ℝ≥0`;
- `CanonicallyOrderedCommSemiring ℝ≥0`;
- `LinearOrderedCommGroupWithZero ℝ≥0`;
- `CanonicallyLinearOrderedAddCommMonoid ℝ≥0`;
- `Archimedean ℝ≥0`;
- `ConditionallyCompleteLinearOrderBot ℝ≥0`.
These instances are derived from corresponding instances about the type `{x : α // 0 ≤ x}` in an
appropriate ordered field/ring/group/monoid `α`, see `Mathlib.Algebra.Order.Nonneg.Ring`.
* `Real.toNNReal x` is defined as `⟨max x 0, _⟩`, i.e. `↑(Real.toNNReal x) = x` when `0 ≤ x` and
`↑(Real.toNNReal x) = 0` otherwise.
We also define an instance `CanLift ℝ ℝ≥0`. This instance can be used by the `lift` tactic to
replace `x : ℝ` and `hx : 0 ≤ x` in the proof context with `x : ℝ≥0` while replacing all occurrences
of `x` with `↑x`. This tactic also works for a function `f : α → ℝ` with a hypothesis
`hf : ∀ x, 0 ≤ f x`.
## Notations
This file defines `ℝ≥0` as a localized notation for `NNReal`.
-/
open Function
-- to ensure these instances are computable
/-- Nonnegative real numbers. -/
def NNReal := { r : ℝ // 0 ≤ r } deriving
Zero, One, Semiring, StrictOrderedSemiring, CommMonoidWithZero, CommSemiring,
SemilatticeInf, SemilatticeSup, DistribLattice, OrderedCommSemiring,
CanonicallyOrderedCommSemiring, Inhabited
#align nnreal NNReal
namespace NNReal
scoped notation "ℝ≥0" => NNReal
noncomputable instance : FloorSemiring ℝ≥0 := Nonneg.floorSemiring
instance instDenselyOrdered : DenselyOrdered ℝ≥0 := Nonneg.instDenselyOrdered
instance : OrderBot ℝ≥0 := inferInstance
instance : Archimedean ℝ≥0 := Nonneg.archimedean
noncomputable instance : Sub ℝ≥0 := Nonneg.sub
noncomputable instance : OrderedSub ℝ≥0 := Nonneg.orderedSub
noncomputable instance : CanonicallyLinearOrderedSemifield ℝ≥0 :=
Nonneg.canonicallyLinearOrderedSemifield
/-- Coercion `ℝ≥0 → ℝ`. -/
@[coe] def toReal : ℝ≥0 → ℝ := Subtype.val
instance : Coe ℝ≥0 ℝ := ⟨toReal⟩
-- Simp lemma to put back `n.val` into the normal form given by the coercion.
@[simp]
theorem val_eq_coe (n : ℝ≥0) : n.val = n :=
rfl
#align nnreal.val_eq_coe NNReal.val_eq_coe
instance canLift : CanLift ℝ ℝ≥0 toReal fun r => 0 ≤ r :=
Subtype.canLift _
#align nnreal.can_lift NNReal.canLift
@[ext] protected theorem eq {n m : ℝ≥0} : (n : ℝ) = (m : ℝ) → n = m :=
Subtype.eq
#align nnreal.eq NNReal.eq
protected theorem eq_iff {n m : ℝ≥0} : (n : ℝ) = (m : ℝ) ↔ n = m :=
Subtype.ext_iff.symm
#align nnreal.eq_iff NNReal.eq_iff
theorem ne_iff {x y : ℝ≥0} : (x : ℝ) ≠ (y : ℝ) ↔ x ≠ y :=
not_congr <| NNReal.eq_iff
#align nnreal.ne_iff NNReal.ne_iff
protected theorem «forall» {p : ℝ≥0 → Prop} :
(∀ x : ℝ≥0, p x) ↔ ∀ (x : ℝ) (hx : 0 ≤ x), p ⟨x, hx⟩ :=
Subtype.forall
#align nnreal.forall NNReal.forall
protected theorem «exists» {p : ℝ≥0 → Prop} :
(∃ x : ℝ≥0, p x) ↔ ∃ (x : ℝ) (hx : 0 ≤ x), p ⟨x, hx⟩ :=
Subtype.exists
#align nnreal.exists NNReal.exists
/-- Reinterpret a real number `r` as a non-negative real number. Returns `0` if `r < 0`. -/
noncomputable def _root_.Real.toNNReal (r : ℝ) : ℝ≥0 :=
⟨max r 0, le_max_right _ _⟩
#align real.to_nnreal Real.toNNReal
theorem _root_.Real.coe_toNNReal (r : ℝ) (hr : 0 ≤ r) : (Real.toNNReal r : ℝ) = r :=
max_eq_left hr
#align real.coe_to_nnreal Real.coe_toNNReal
theorem _root_.Real.toNNReal_of_nonneg {r : ℝ} (hr : 0 ≤ r) : r.toNNReal = ⟨r, hr⟩ := by
simp_rw [Real.toNNReal, max_eq_left hr]
#align real.to_nnreal_of_nonneg Real.toNNReal_of_nonneg
theorem _root_.Real.le_coe_toNNReal (r : ℝ) : r ≤ Real.toNNReal r :=
le_max_left r 0
#align real.le_coe_to_nnreal Real.le_coe_toNNReal
theorem coe_nonneg (r : ℝ≥0) : (0 : ℝ) ≤ r := r.2
#align nnreal.coe_nonneg NNReal.coe_nonneg
@[simp, norm_cast] theorem coe_mk (a : ℝ) (ha) : toReal ⟨a, ha⟩ = a := rfl
#align nnreal.coe_mk NNReal.coe_mk
example : Zero ℝ≥0 := by infer_instance
example : One ℝ≥0 := by infer_instance
example : Add ℝ≥0 := by infer_instance
noncomputable example : Sub ℝ≥0 := by infer_instance
example : Mul ℝ≥0 := by infer_instance
noncomputable example : Inv ℝ≥0 := by infer_instance
noncomputable example : Div ℝ≥0 := by infer_instance
example : LE ℝ≥0 := by infer_instance
example : Bot ℝ≥0 := by infer_instance
example : Inhabited ℝ≥0 := by infer_instance
example : Nontrivial ℝ≥0 := by infer_instance
protected theorem coe_injective : Injective ((↑) : ℝ≥0 → ℝ) := Subtype.coe_injective
#align nnreal.coe_injective NNReal.coe_injective
@[simp, norm_cast] lemma coe_inj {r₁ r₂ : ℝ≥0} : (r₁ : ℝ) = r₂ ↔ r₁ = r₂ :=
NNReal.coe_injective.eq_iff
#align nnreal.coe_eq NNReal.coe_inj
@[deprecated (since := "2024-02-03")] protected alias coe_eq := coe_inj
@[simp, norm_cast] lemma coe_zero : ((0 : ℝ≥0) : ℝ) = 0 := rfl
#align nnreal.coe_zero NNReal.coe_zero
@[simp, norm_cast] lemma coe_one : ((1 : ℝ≥0) : ℝ) = 1 := rfl
#align nnreal.coe_one NNReal.coe_one
@[simp, norm_cast]
protected theorem coe_add (r₁ r₂ : ℝ≥0) : ((r₁ + r₂ : ℝ≥0) : ℝ) = r₁ + r₂ :=
rfl
#align nnreal.coe_add NNReal.coe_add
@[simp, norm_cast]
protected theorem coe_mul (r₁ r₂ : ℝ≥0) : ((r₁ * r₂ : ℝ≥0) : ℝ) = r₁ * r₂ :=
rfl
#align nnreal.coe_mul NNReal.coe_mul
@[simp, norm_cast]
protected theorem coe_inv (r : ℝ≥0) : ((r⁻¹ : ℝ≥0) : ℝ) = (r : ℝ)⁻¹ :=
rfl
#align nnreal.coe_inv NNReal.coe_inv
@[simp, norm_cast]
protected theorem coe_div (r₁ r₂ : ℝ≥0) : ((r₁ / r₂ : ℝ≥0) : ℝ) = (r₁ : ℝ) / r₂ :=
rfl
#align nnreal.coe_div NNReal.coe_div
#noalign nnreal.coe_bit0
#noalign nnreal.coe_bit1
protected theorem coe_two : ((2 : ℝ≥0) : ℝ) = 2 := rfl
#align nnreal.coe_two NNReal.coe_two
@[simp, norm_cast]
protected theorem coe_sub {r₁ r₂ : ℝ≥0} (h : r₂ ≤ r₁) : ((r₁ - r₂ : ℝ≥0) : ℝ) = ↑r₁ - ↑r₂ :=
max_eq_left <| le_sub_comm.2 <| by simp [show (r₂ : ℝ) ≤ r₁ from h]
#align nnreal.coe_sub NNReal.coe_sub
variable {r r₁ r₂ : ℝ≥0} {x y : ℝ}
@[simp, norm_cast] lemma coe_eq_zero : (r : ℝ) = 0 ↔ r = 0 := by rw [← coe_zero, coe_inj]
#align coe_eq_zero NNReal.coe_eq_zero
@[simp, norm_cast] lemma coe_eq_one : (r : ℝ) = 1 ↔ r = 1 := by rw [← coe_one, coe_inj]
#align coe_inj_one NNReal.coe_eq_one
@[norm_cast] lemma coe_ne_zero : (r : ℝ) ≠ 0 ↔ r ≠ 0 := coe_eq_zero.not
#align nnreal.coe_ne_zero NNReal.coe_ne_zero
@[norm_cast] lemma coe_ne_one : (r : ℝ) ≠ 1 ↔ r ≠ 1 := coe_eq_one.not
example : CommSemiring ℝ≥0 := by infer_instance
/-- Coercion `ℝ≥0 → ℝ` as a `RingHom`.
Porting note (#11215): TODO: what if we define `Coe ℝ≥0 ℝ` using this function? -/
def toRealHom : ℝ≥0 →+* ℝ where
toFun := (↑)
map_one' := NNReal.coe_one
map_mul' := NNReal.coe_mul
map_zero' := NNReal.coe_zero
map_add' := NNReal.coe_add
#align nnreal.to_real_hom NNReal.toRealHom
@[simp] theorem coe_toRealHom : ⇑toRealHom = toReal := rfl
#align nnreal.coe_to_real_hom NNReal.coe_toRealHom
section Actions
/-- A `MulAction` over `ℝ` restricts to a `MulAction` over `ℝ≥0`. -/
instance {M : Type*} [MulAction ℝ M] : MulAction ℝ≥0 M :=
MulAction.compHom M toRealHom.toMonoidHom
theorem smul_def {M : Type*} [MulAction ℝ M] (c : ℝ≥0) (x : M) : c • x = (c : ℝ) • x :=
rfl
#align nnreal.smul_def NNReal.smul_def
instance {M N : Type*} [MulAction ℝ M] [MulAction ℝ N] [SMul M N] [IsScalarTower ℝ M N] :
IsScalarTower ℝ≥0 M N where smul_assoc r := (smul_assoc (r : ℝ) : _)
instance smulCommClass_left {M N : Type*} [MulAction ℝ N] [SMul M N] [SMulCommClass ℝ M N] :
SMulCommClass ℝ≥0 M N where smul_comm r := (smul_comm (r : ℝ) : _)
#align nnreal.smul_comm_class_left NNReal.smulCommClass_left
instance smulCommClass_right {M N : Type*} [MulAction ℝ N] [SMul M N] [SMulCommClass M ℝ N] :
SMulCommClass M ℝ≥0 N where smul_comm m r := (smul_comm m (r : ℝ) : _)
#align nnreal.smul_comm_class_right NNReal.smulCommClass_right
/-- A `DistribMulAction` over `ℝ` restricts to a `DistribMulAction` over `ℝ≥0`. -/
instance {M : Type*} [AddMonoid M] [DistribMulAction ℝ M] : DistribMulAction ℝ≥0 M :=
DistribMulAction.compHom M toRealHom.toMonoidHom
/-- A `Module` over `ℝ` restricts to a `Module` over `ℝ≥0`. -/
instance {M : Type*} [AddCommMonoid M] [Module ℝ M] : Module ℝ≥0 M :=
Module.compHom M toRealHom
-- Porting note (#11215): TODO: after this line, `↑` uses `Algebra.cast` instead of `toReal`
/-- An `Algebra` over `ℝ` restricts to an `Algebra` over `ℝ≥0`. -/
instance {A : Type*} [Semiring A] [Algebra ℝ A] : Algebra ℝ≥0 A where
smul := (· • ·)
commutes' r x := by simp [Algebra.commutes]
smul_def' r x := by simp [← Algebra.smul_def (r : ℝ) x, smul_def]
toRingHom := (algebraMap ℝ A).comp (toRealHom : ℝ≥0 →+* ℝ)
instance : StarRing ℝ≥0 := starRingOfComm
instance : TrivialStar ℝ≥0 where
star_trivial _ := rfl
instance : StarModule ℝ≥0 ℝ where
star_smul := by simp only [star_trivial, eq_self_iff_true, forall_const]
-- verify that the above produces instances we might care about
example : Algebra ℝ≥0 ℝ := by infer_instance
example : DistribMulAction ℝ≥0ˣ ℝ := by infer_instance
end Actions
example : MonoidWithZero ℝ≥0 := by infer_instance
example : CommMonoidWithZero ℝ≥0 := by infer_instance
noncomputable example : CommGroupWithZero ℝ≥0 := by infer_instance
@[simp, norm_cast]
theorem coe_indicator {α} (s : Set α) (f : α → ℝ≥0) (a : α) :
((s.indicator f a : ℝ≥0) : ℝ) = s.indicator (fun x => ↑(f x)) a :=
(toRealHom : ℝ≥0 →+ ℝ).map_indicator _ _ _
#align nnreal.coe_indicator NNReal.coe_indicator
@[simp, norm_cast]
theorem coe_pow (r : ℝ≥0) (n : ℕ) : ((r ^ n : ℝ≥0) : ℝ) = (r : ℝ) ^ n := rfl
#align nnreal.coe_pow NNReal.coe_pow
@[simp, norm_cast]
theorem coe_zpow (r : ℝ≥0) (n : ℤ) : ((r ^ n : ℝ≥0) : ℝ) = (r : ℝ) ^ n := rfl
#align nnreal.coe_zpow NNReal.coe_zpow
@[norm_cast]
theorem coe_list_sum (l : List ℝ≥0) : ((l.sum : ℝ≥0) : ℝ) = (l.map (↑)).sum :=
map_list_sum toRealHom l
#align nnreal.coe_list_sum NNReal.coe_list_sum
@[norm_cast]
theorem coe_list_prod (l : List ℝ≥0) : ((l.prod : ℝ≥0) : ℝ) = (l.map (↑)).prod :=
map_list_prod toRealHom l
#align nnreal.coe_list_prod NNReal.coe_list_prod
@[norm_cast]
theorem coe_multiset_sum (s : Multiset ℝ≥0) : ((s.sum : ℝ≥0) : ℝ) = (s.map (↑)).sum :=
map_multiset_sum toRealHom s
#align nnreal.coe_multiset_sum NNReal.coe_multiset_sum
@[norm_cast]
theorem coe_multiset_prod (s : Multiset ℝ≥0) : ((s.prod : ℝ≥0) : ℝ) = (s.map (↑)).prod :=
map_multiset_prod toRealHom s
#align nnreal.coe_multiset_prod NNReal.coe_multiset_prod
@[norm_cast]
theorem coe_sum {α} {s : Finset α} {f : α → ℝ≥0} : ↑(∑ a ∈ s, f a) = ∑ a ∈ s, (f a : ℝ) :=
map_sum toRealHom _ _
#align nnreal.coe_sum NNReal.coe_sum
theorem _root_.Real.toNNReal_sum_of_nonneg {α} {s : Finset α} {f : α → ℝ}
(hf : ∀ a, a ∈ s → 0 ≤ f a) :
Real.toNNReal (∑ a ∈ s, f a) = ∑ a ∈ s, Real.toNNReal (f a) := by
rw [← coe_inj, NNReal.coe_sum, Real.coe_toNNReal _ (Finset.sum_nonneg hf)]
exact Finset.sum_congr rfl fun x hxs => by rw [Real.coe_toNNReal _ (hf x hxs)]
#align real.to_nnreal_sum_of_nonneg Real.toNNReal_sum_of_nonneg
@[norm_cast]
theorem coe_prod {α} {s : Finset α} {f : α → ℝ≥0} : ↑(∏ a ∈ s, f a) = ∏ a ∈ s, (f a : ℝ) :=
map_prod toRealHom _ _
#align nnreal.coe_prod NNReal.coe_prod
theorem _root_.Real.toNNReal_prod_of_nonneg {α} {s : Finset α} {f : α → ℝ}
(hf : ∀ a, a ∈ s → 0 ≤ f a) :
Real.toNNReal (∏ a ∈ s, f a) = ∏ a ∈ s, Real.toNNReal (f a) := by
rw [← coe_inj, NNReal.coe_prod, Real.coe_toNNReal _ (Finset.prod_nonneg hf)]
exact Finset.prod_congr rfl fun x hxs => by rw [Real.coe_toNNReal _ (hf x hxs)]
#align real.to_nnreal_prod_of_nonneg Real.toNNReal_prod_of_nonneg
-- Porting note (#11215): TODO: `simp`? `norm_cast`?
theorem coe_nsmul (r : ℝ≥0) (n : ℕ) : ↑(n • r) = n • (r : ℝ) := rfl
#align nnreal.nsmul_coe NNReal.coe_nsmul
@[simp, norm_cast]
protected theorem coe_natCast (n : ℕ) : (↑(↑n : ℝ≥0) : ℝ) = n :=
map_natCast toRealHom n
#align nnreal.coe_nat_cast NNReal.coe_natCast
@[deprecated (since := "2024-04-17")]
alias coe_nat_cast := NNReal.coe_natCast
-- See note [no_index around OfNat.ofNat]
@[simp, norm_cast]
protected theorem coe_ofNat (n : ℕ) [n.AtLeastTwo] :
(no_index (OfNat.ofNat n : ℝ≥0) : ℝ) = OfNat.ofNat n :=
rfl
@[simp, norm_cast]
protected theorem coe_ofScientific (m : ℕ) (s : Bool) (e : ℕ) :
↑(OfScientific.ofScientific m s e : ℝ≥0) = (OfScientific.ofScientific m s e : ℝ) :=
rfl
noncomputable example : LinearOrder ℝ≥0 := by infer_instance
@[simp, norm_cast] lemma coe_le_coe : (r₁ : ℝ) ≤ r₂ ↔ r₁ ≤ r₂ := Iff.rfl
#align nnreal.coe_le_coe NNReal.coe_le_coe
@[simp, norm_cast] lemma coe_lt_coe : (r₁ : ℝ) < r₂ ↔ r₁ < r₂ := Iff.rfl
#align nnreal.coe_lt_coe NNReal.coe_lt_coe
@[simp, norm_cast] lemma coe_pos : (0 : ℝ) < r ↔ 0 < r := Iff.rfl
#align nnreal.coe_pos NNReal.coe_pos
@[simp, norm_cast] lemma one_le_coe : 1 ≤ (r : ℝ) ↔ 1 ≤ r := by rw [← coe_le_coe, coe_one]
@[simp, norm_cast] lemma one_lt_coe : 1 < (r : ℝ) ↔ 1 < r := by rw [← coe_lt_coe, coe_one]
@[simp, norm_cast] lemma coe_le_one : (r : ℝ) ≤ 1 ↔ r ≤ 1 := by rw [← coe_le_coe, coe_one]
@[simp, norm_cast] lemma coe_lt_one : (r : ℝ) < 1 ↔ r < 1 := by rw [← coe_lt_coe, coe_one]
@[mono] lemma coe_mono : Monotone ((↑) : ℝ≥0 → ℝ) := fun _ _ => NNReal.coe_le_coe.2
#align nnreal.coe_mono NNReal.coe_mono
/-- Alias for the use of `gcongr` -/
@[gcongr] alias ⟨_, GCongr.toReal_le_toReal⟩ := coe_le_coe
protected theorem _root_.Real.toNNReal_mono : Monotone Real.toNNReal := fun _ _ h =>
max_le_max h (le_refl 0)
#align real.to_nnreal_mono Real.toNNReal_mono
@[simp]
theorem _root_.Real.toNNReal_coe {r : ℝ≥0} : Real.toNNReal r = r :=
NNReal.eq <| max_eq_left r.2
#align real.to_nnreal_coe Real.toNNReal_coe
@[simp]
theorem mk_natCast (n : ℕ) : @Eq ℝ≥0 (⟨(n : ℝ), n.cast_nonneg⟩ : ℝ≥0) n :=
NNReal.eq (NNReal.coe_natCast n).symm
#align nnreal.mk_coe_nat NNReal.mk_natCast
@[deprecated (since := "2024-04-05")] alias mk_coe_nat := mk_natCast
-- Porting note: place this in the `Real` namespace
@[simp]
theorem toNNReal_coe_nat (n : ℕ) : Real.toNNReal n = n :=
NNReal.eq <| by simp [Real.coe_toNNReal]
#align nnreal.to_nnreal_coe_nat NNReal.toNNReal_coe_nat
-- See note [no_index around OfNat.ofNat]
@[simp]
theorem _root_.Real.toNNReal_ofNat (n : ℕ) [n.AtLeastTwo] :
Real.toNNReal (no_index (OfNat.ofNat n)) = OfNat.ofNat n :=
toNNReal_coe_nat n
/-- `Real.toNNReal` and `NNReal.toReal : ℝ≥0 → ℝ` form a Galois insertion. -/
noncomputable def gi : GaloisInsertion Real.toNNReal (↑) :=
GaloisInsertion.monotoneIntro NNReal.coe_mono Real.toNNReal_mono Real.le_coe_toNNReal fun _ =>
Real.toNNReal_coe
#align nnreal.gi NNReal.gi
-- note that anything involving the (decidability of the) linear order,
-- will be noncomputable, everything else should not be.
example : OrderBot ℝ≥0 := by infer_instance
example : PartialOrder ℝ≥0 := by infer_instance
noncomputable example : CanonicallyLinearOrderedAddCommMonoid ℝ≥0 := by infer_instance
noncomputable example : LinearOrderedAddCommMonoid ℝ≥0 := by infer_instance
example : DistribLattice ℝ≥0 := by infer_instance
example : SemilatticeInf ℝ≥0 := by infer_instance
example : SemilatticeSup ℝ≥0 := by infer_instance
noncomputable example : LinearOrderedSemiring ℝ≥0 := by infer_instance
example : OrderedCommSemiring ℝ≥0 := by infer_instance
noncomputable example : LinearOrderedCommMonoid ℝ≥0 := by infer_instance
noncomputable example : LinearOrderedCommMonoidWithZero ℝ≥0 := by infer_instance
noncomputable example : LinearOrderedCommGroupWithZero ℝ≥0 := by infer_instance
example : CanonicallyOrderedCommSemiring ℝ≥0 := by infer_instance
example : DenselyOrdered ℝ≥0 := by infer_instance
example : NoMaxOrder ℝ≥0 := by infer_instance
instance instPosSMulStrictMono {α} [Preorder α] [MulAction ℝ α] [PosSMulStrictMono ℝ α] :
PosSMulStrictMono ℝ≥0 α where
elim _r hr _a₁ _a₂ ha := (smul_lt_smul_of_pos_left ha (coe_pos.2 hr):)
instance instSMulPosStrictMono {α} [Zero α] [Preorder α] [MulAction ℝ α] [SMulPosStrictMono ℝ α] :
SMulPosStrictMono ℝ≥0 α where
elim _a ha _r₁ _r₂ hr := (smul_lt_smul_of_pos_right (coe_lt_coe.2 hr) ha:)
/-- If `a` is a nonnegative real number, then the closed interval `[0, a]` in `ℝ` is order
isomorphic to the interval `Set.Iic a`. -/
-- Porting note (#11215): TODO: restore once `simps` supports `ℝ≥0` @[simps!? apply_coe_coe]
def orderIsoIccZeroCoe (a : ℝ≥0) : Set.Icc (0 : ℝ) a ≃o Set.Iic a where
toEquiv := Equiv.Set.sep (Set.Ici 0) fun x : ℝ => x ≤ a
map_rel_iff' := Iff.rfl
#align nnreal.order_iso_Icc_zero_coe NNReal.orderIsoIccZeroCoe
@[simp]
theorem orderIsoIccZeroCoe_apply_coe_coe (a : ℝ≥0) (b : Set.Icc (0 : ℝ) a) :
(orderIsoIccZeroCoe a b : ℝ) = b :=
rfl
@[simp]
theorem orderIsoIccZeroCoe_symm_apply_coe (a : ℝ≥0) (b : Set.Iic a) :
((orderIsoIccZeroCoe a).symm b : ℝ) = b :=
rfl
#align nnreal.order_iso_Icc_zero_coe_symm_apply_coe NNReal.orderIsoIccZeroCoe_symm_apply_coe
-- note we need the `@` to make the `Membership.mem` have a sensible type
theorem coe_image {s : Set ℝ≥0} :
(↑) '' s = { x : ℝ | ∃ h : 0 ≤ x, @Membership.mem ℝ≥0 _ _ ⟨x, h⟩ s } :=
Subtype.coe_image
#align nnreal.coe_image NNReal.coe_image
theorem bddAbove_coe {s : Set ℝ≥0} : BddAbove (((↑) : ℝ≥0 → ℝ) '' s) ↔ BddAbove s :=
Iff.intro
(fun ⟨b, hb⟩ =>
⟨Real.toNNReal b, fun ⟨y, _⟩ hys =>
show y ≤ max b 0 from le_max_of_le_left <| hb <| Set.mem_image_of_mem _ hys⟩)
fun ⟨b, hb⟩ => ⟨b, fun _ ⟨_, hx, eq⟩ => eq ▸ hb hx⟩
#align nnreal.bdd_above_coe NNReal.bddAbove_coe
theorem bddBelow_coe (s : Set ℝ≥0) : BddBelow (((↑) : ℝ≥0 → ℝ) '' s) :=
⟨0, fun _ ⟨q, _, eq⟩ => eq ▸ q.2⟩
#align nnreal.bdd_below_coe NNReal.bddBelow_coe
noncomputable instance : ConditionallyCompleteLinearOrderBot ℝ≥0 :=
Nonneg.conditionallyCompleteLinearOrderBot 0
@[norm_cast]
theorem coe_sSup (s : Set ℝ≥0) : (↑(sSup s) : ℝ) = sSup (((↑) : ℝ≥0 → ℝ) '' s) := by
rcases Set.eq_empty_or_nonempty s with rfl|hs
· simp
by_cases H : BddAbove s
· have A : sSup (Subtype.val '' s) ∈ Set.Ici 0 := by
apply Real.sSup_nonneg
rintro - ⟨y, -, rfl⟩
exact y.2
exact (@subset_sSup_of_within ℝ (Set.Ici (0 : ℝ)) _ _ (_) s hs H A).symm
· simp only [csSup_of_not_bddAbove H, csSup_empty, bot_eq_zero', NNReal.coe_zero]
apply (Real.sSup_of_not_bddAbove ?_).symm
contrapose! H
exact bddAbove_coe.1 H
#align nnreal.coe_Sup NNReal.coe_sSup
@[simp, norm_cast] -- Porting note: add `simp`
theorem coe_iSup {ι : Sort*} (s : ι → ℝ≥0) : (↑(⨆ i, s i) : ℝ) = ⨆ i, ↑(s i) := by
rw [iSup, iSup, coe_sSup, ← Set.range_comp]; rfl
#align nnreal.coe_supr NNReal.coe_iSup
@[norm_cast]
theorem coe_sInf (s : Set ℝ≥0) : (↑(sInf s) : ℝ) = sInf (((↑) : ℝ≥0 → ℝ) '' s) := by
rcases Set.eq_empty_or_nonempty s with rfl|hs
· simp only [Set.image_empty, Real.sInf_empty, coe_eq_zero]
exact @subset_sInf_emptyset ℝ (Set.Ici (0 : ℝ)) _ _ (_)
have A : sInf (Subtype.val '' s) ∈ Set.Ici 0 := by
apply Real.sInf_nonneg
rintro - ⟨y, -, rfl⟩
exact y.2
exact (@subset_sInf_of_within ℝ (Set.Ici (0 : ℝ)) _ _ (_) s hs (OrderBot.bddBelow s) A).symm
#align nnreal.coe_Inf NNReal.coe_sInf
@[simp]
theorem sInf_empty : sInf (∅ : Set ℝ≥0) = 0 := by
rw [← coe_eq_zero, coe_sInf, Set.image_empty, Real.sInf_empty]
#align nnreal.Inf_empty NNReal.sInf_empty
@[norm_cast]
theorem coe_iInf {ι : Sort*} (s : ι → ℝ≥0) : (↑(⨅ i, s i) : ℝ) = ⨅ i, ↑(s i) := by
rw [iInf, iInf, coe_sInf, ← Set.range_comp]; rfl
#align nnreal.coe_infi NNReal.coe_iInf
theorem le_iInf_add_iInf {ι ι' : Sort*} [Nonempty ι] [Nonempty ι'] {f : ι → ℝ≥0} {g : ι' → ℝ≥0}
{a : ℝ≥0} (h : ∀ i j, a ≤ f i + g j) : a ≤ (⨅ i, f i) + ⨅ j, g j := by
rw [← NNReal.coe_le_coe, NNReal.coe_add, coe_iInf, coe_iInf]
exact le_ciInf_add_ciInf h
#align nnreal.le_infi_add_infi NNReal.le_iInf_add_iInf
example : Archimedean ℝ≥0 := by infer_instance
-- Porting note (#11215): TODO: remove?
instance covariant_add : CovariantClass ℝ≥0 ℝ≥0 (· + ·) (· ≤ ·) := inferInstance
#align nnreal.covariant_add NNReal.covariant_add
instance contravariant_add : ContravariantClass ℝ≥0 ℝ≥0 (· + ·) (· < ·) := inferInstance
#align nnreal.contravariant_add NNReal.contravariant_add
instance covariant_mul : CovariantClass ℝ≥0 ℝ≥0 (· * ·) (· ≤ ·) := inferInstance
#align nnreal.covariant_mul NNReal.covariant_mul
-- Porting note (#11215): TODO: delete?
nonrec theorem le_of_forall_pos_le_add {a b : ℝ≥0} (h : ∀ ε, 0 < ε → a ≤ b + ε) : a ≤ b :=
le_of_forall_pos_le_add h
#align nnreal.le_of_forall_pos_le_add NNReal.le_of_forall_pos_le_add
theorem lt_iff_exists_rat_btwn (a b : ℝ≥0) :
a < b ↔ ∃ q : ℚ, 0 ≤ q ∧ a < Real.toNNReal q ∧ Real.toNNReal q < b :=
Iff.intro
(fun h : (↑a : ℝ) < (↑b : ℝ) =>
let ⟨q, haq, hqb⟩ := exists_rat_btwn h
have : 0 ≤ (q : ℝ) := le_trans a.2 <| le_of_lt haq
⟨q, Rat.cast_nonneg.1 this, by
simp [Real.coe_toNNReal _ this, NNReal.coe_lt_coe.symm, haq, hqb]⟩)
fun ⟨q, _, haq, hqb⟩ => lt_trans haq hqb
#align nnreal.lt_iff_exists_rat_btwn NNReal.lt_iff_exists_rat_btwn
theorem bot_eq_zero : (⊥ : ℝ≥0) = 0 := rfl
#align nnreal.bot_eq_zero NNReal.bot_eq_zero
theorem mul_sup (a b c : ℝ≥0) : a * (b ⊔ c) = a * b ⊔ a * c :=
mul_max_of_nonneg _ _ <| zero_le a
#align nnreal.mul_sup NNReal.mul_sup
theorem sup_mul (a b c : ℝ≥0) : (a ⊔ b) * c = a * c ⊔ b * c :=
max_mul_of_nonneg _ _ <| zero_le c
#align nnreal.sup_mul NNReal.sup_mul
theorem mul_finset_sup {α} (r : ℝ≥0) (s : Finset α) (f : α → ℝ≥0) :
r * s.sup f = s.sup fun a => r * f a :=
Finset.comp_sup_eq_sup_comp _ (NNReal.mul_sup r) (mul_zero r)
#align nnreal.mul_finset_sup NNReal.mul_finset_sup
theorem finset_sup_mul {α} (s : Finset α) (f : α → ℝ≥0) (r : ℝ≥0) :
s.sup f * r = s.sup fun a => f a * r :=
Finset.comp_sup_eq_sup_comp (· * r) (fun x y => NNReal.sup_mul x y r) (zero_mul r)
#align nnreal.finset_sup_mul NNReal.finset_sup_mul
theorem finset_sup_div {α} {f : α → ℝ≥0} {s : Finset α} (r : ℝ≥0) :
s.sup f / r = s.sup fun a => f a / r := by simp only [div_eq_inv_mul, mul_finset_sup]
#align nnreal.finset_sup_div NNReal.finset_sup_div
@[simp, norm_cast]
theorem coe_max (x y : ℝ≥0) : ((max x y : ℝ≥0) : ℝ) = max (x : ℝ) (y : ℝ) :=
NNReal.coe_mono.map_max
#align nnreal.coe_max NNReal.coe_max
@[simp, norm_cast]
theorem coe_min (x y : ℝ≥0) : ((min x y : ℝ≥0) : ℝ) = min (x : ℝ) (y : ℝ) :=
NNReal.coe_mono.map_min
#align nnreal.coe_min NNReal.coe_min
@[simp]
theorem zero_le_coe {q : ℝ≥0} : 0 ≤ (q : ℝ) :=
q.2
#align nnreal.zero_le_coe NNReal.zero_le_coe
instance instOrderedSMul {M : Type*} [OrderedAddCommMonoid M] [Module ℝ M] [OrderedSMul ℝ M] :
OrderedSMul ℝ≥0 M where
smul_lt_smul_of_pos hab hc := (smul_lt_smul_of_pos_left hab (NNReal.coe_pos.2 hc) : _)
lt_of_smul_lt_smul_of_pos {a b c} hab _ :=
lt_of_smul_lt_smul_of_nonneg_left (by exact hab) (NNReal.coe_nonneg c)
end NNReal
open NNReal
namespace Real
section ToNNReal
@[simp]
theorem coe_toNNReal' (r : ℝ) : (Real.toNNReal r : ℝ) = max r 0 :=
rfl
#align real.coe_to_nnreal' Real.coe_toNNReal'
@[simp]
theorem toNNReal_zero : Real.toNNReal 0 = 0 := NNReal.eq <| coe_toNNReal _ le_rfl
#align real.to_nnreal_zero Real.toNNReal_zero
@[simp]
theorem toNNReal_one : Real.toNNReal 1 = 1 := NNReal.eq <| coe_toNNReal _ zero_le_one
#align real.to_nnreal_one Real.toNNReal_one
@[simp]
theorem toNNReal_pos {r : ℝ} : 0 < Real.toNNReal r ↔ 0 < r := by
simp [← NNReal.coe_lt_coe, lt_irrefl]
#align real.to_nnreal_pos Real.toNNReal_pos
@[simp]
theorem toNNReal_eq_zero {r : ℝ} : Real.toNNReal r = 0 ↔ r ≤ 0 := by
simpa [-toNNReal_pos] using not_iff_not.2 (@toNNReal_pos r)
#align real.to_nnreal_eq_zero Real.toNNReal_eq_zero
theorem toNNReal_of_nonpos {r : ℝ} : r ≤ 0 → Real.toNNReal r = 0 :=
toNNReal_eq_zero.2
#align real.to_nnreal_of_nonpos Real.toNNReal_of_nonpos
lemma toNNReal_eq_iff_eq_coe {r : ℝ} {p : ℝ≥0} (hp : p ≠ 0) : r.toNNReal = p ↔ r = p :=
⟨fun h ↦ h ▸ (coe_toNNReal _ <| not_lt.1 fun hlt ↦ hp <| h ▸ toNNReal_of_nonpos hlt.le).symm,
fun h ↦ h.symm ▸ toNNReal_coe⟩
@[simp]
lemma toNNReal_eq_one {r : ℝ} : r.toNNReal = 1 ↔ r = 1 := toNNReal_eq_iff_eq_coe one_ne_zero
@[simp]
lemma toNNReal_eq_natCast {r : ℝ} {n : ℕ} (hn : n ≠ 0) : r.toNNReal = n ↔ r = n :=
mod_cast toNNReal_eq_iff_eq_coe <| Nat.cast_ne_zero.2 hn
@[deprecated (since := "2024-04-17")]
alias toNNReal_eq_nat_cast := toNNReal_eq_natCast
@[simp]
lemma toNNReal_eq_ofNat {r : ℝ} {n : ℕ} [n.AtLeastTwo] :
r.toNNReal = no_index (OfNat.ofNat n) ↔ r = OfNat.ofNat n :=
toNNReal_eq_natCast (NeZero.ne n)
@[simp]
theorem toNNReal_le_toNNReal_iff {r p : ℝ} (hp : 0 ≤ p) :
toNNReal r ≤ toNNReal p ↔ r ≤ p := by simp [← NNReal.coe_le_coe, hp]
#align real.to_nnreal_le_to_nnreal_iff Real.toNNReal_le_toNNReal_iff
@[simp]
lemma toNNReal_le_one {r : ℝ} : r.toNNReal ≤ 1 ↔ r ≤ 1 := by
simpa using toNNReal_le_toNNReal_iff zero_le_one
@[simp]
lemma one_lt_toNNReal {r : ℝ} : 1 < r.toNNReal ↔ 1 < r := by
simpa only [not_le] using toNNReal_le_one.not
@[simp]
lemma toNNReal_le_natCast {r : ℝ} {n : ℕ} : r.toNNReal ≤ n ↔ r ≤ n := by
simpa using toNNReal_le_toNNReal_iff n.cast_nonneg
@[deprecated (since := "2024-04-17")]
alias toNNReal_le_nat_cast := toNNReal_le_natCast
@[simp]
lemma natCast_lt_toNNReal {r : ℝ} {n : ℕ} : n < r.toNNReal ↔ n < r := by
simpa only [not_le] using toNNReal_le_natCast.not
@[deprecated (since := "2024-04-17")]
alias nat_cast_lt_toNNReal := natCast_lt_toNNReal
@[simp]
lemma toNNReal_le_ofNat {r : ℝ} {n : ℕ} [n.AtLeastTwo] :
r.toNNReal ≤ no_index (OfNat.ofNat n) ↔ r ≤ n :=
toNNReal_le_natCast
@[simp]
lemma ofNat_lt_toNNReal {r : ℝ} {n : ℕ} [n.AtLeastTwo] :
no_index (OfNat.ofNat n) < r.toNNReal ↔ n < r :=
natCast_lt_toNNReal
@[simp]
theorem toNNReal_eq_toNNReal_iff {r p : ℝ} (hr : 0 ≤ r) (hp : 0 ≤ p) :
toNNReal r = toNNReal p ↔ r = p := by simp [← coe_inj, coe_toNNReal, hr, hp]
#align real.to_nnreal_eq_to_nnreal_iff Real.toNNReal_eq_toNNReal_iff
@[simp]
theorem toNNReal_lt_toNNReal_iff' {r p : ℝ} : Real.toNNReal r < Real.toNNReal p ↔ r < p ∧ 0 < p :=
NNReal.coe_lt_coe.symm.trans max_lt_max_left_iff
#align real.to_nnreal_lt_to_nnreal_iff' Real.toNNReal_lt_toNNReal_iff'
theorem toNNReal_lt_toNNReal_iff {r p : ℝ} (h : 0 < p) :
Real.toNNReal r < Real.toNNReal p ↔ r < p :=
toNNReal_lt_toNNReal_iff'.trans (and_iff_left h)
#align real.to_nnreal_lt_to_nnreal_iff Real.toNNReal_lt_toNNReal_iff
theorem lt_of_toNNReal_lt {r p : ℝ} (h : r.toNNReal < p.toNNReal) : r < p :=
(Real.toNNReal_lt_toNNReal_iff <| Real.toNNReal_pos.1 (ne_bot_of_gt h).bot_lt).1 h
theorem toNNReal_lt_toNNReal_iff_of_nonneg {r p : ℝ} (hr : 0 ≤ r) :
Real.toNNReal r < Real.toNNReal p ↔ r < p :=
toNNReal_lt_toNNReal_iff'.trans ⟨And.left, fun h => ⟨h, lt_of_le_of_lt hr h⟩⟩
#align real.to_nnreal_lt_to_nnreal_iff_of_nonneg Real.toNNReal_lt_toNNReal_iff_of_nonneg
lemma toNNReal_le_toNNReal_iff' {r p : ℝ} : r.toNNReal ≤ p.toNNReal ↔ r ≤ p ∨ r ≤ 0 := by
simp_rw [← not_lt, toNNReal_lt_toNNReal_iff', not_and_or]
lemma toNNReal_le_toNNReal_iff_of_pos {r p : ℝ} (hr : 0 < r) : r.toNNReal ≤ p.toNNReal ↔ r ≤ p := by
simp [toNNReal_le_toNNReal_iff', hr.not_le]
@[simp]
lemma one_le_toNNReal {r : ℝ} : 1 ≤ r.toNNReal ↔ 1 ≤ r := by
simpa using toNNReal_le_toNNReal_iff_of_pos one_pos
@[simp]
lemma toNNReal_lt_one {r : ℝ} : r.toNNReal < 1 ↔ r < 1 := by simp only [← not_le, one_le_toNNReal]
@[simp]
lemma natCastle_toNNReal' {n : ℕ} {r : ℝ} : ↑n ≤ r.toNNReal ↔ n ≤ r ∨ n = 0 := by
simpa [n.cast_nonneg.le_iff_eq] using toNNReal_le_toNNReal_iff' (r := n)
@[deprecated (since := "2024-04-17")]
alias nat_cast_le_toNNReal' := natCastle_toNNReal'
@[simp]
lemma toNNReal_lt_natCast' {n : ℕ} {r : ℝ} : r.toNNReal < n ↔ r < n ∧ n ≠ 0 := by
simpa [pos_iff_ne_zero] using toNNReal_lt_toNNReal_iff' (r := r) (p := n)
@[deprecated (since := "2024-04-17")]
alias toNNReal_lt_nat_cast' := toNNReal_lt_natCast'
lemma natCast_le_toNNReal {n : ℕ} {r : ℝ} (hn : n ≠ 0) : ↑n ≤ r.toNNReal ↔ n ≤ r := by simp [hn]
@[deprecated (since := "2024-04-17")]
alias nat_cast_le_toNNReal := natCast_le_toNNReal
lemma toNNReal_lt_natCast {r : ℝ} {n : ℕ} (hn : n ≠ 0) : r.toNNReal < n ↔ r < n := by simp [hn]
@[deprecated (since := "2024-04-17")]
alias toNNReal_lt_nat_cast := toNNReal_lt_natCast
@[simp]
lemma toNNReal_lt_ofNat {r : ℝ} {n : ℕ} [n.AtLeastTwo] :
r.toNNReal < no_index (OfNat.ofNat n) ↔ r < OfNat.ofNat n :=
toNNReal_lt_natCast (NeZero.ne n)
@[simp]
lemma ofNat_le_toNNReal {n : ℕ} {r : ℝ} [n.AtLeastTwo] :
no_index (OfNat.ofNat n) ≤ r.toNNReal ↔ OfNat.ofNat n ≤ r :=
natCast_le_toNNReal (NeZero.ne n)
@[simp]
theorem toNNReal_add {r p : ℝ} (hr : 0 ≤ r) (hp : 0 ≤ p) :
Real.toNNReal (r + p) = Real.toNNReal r + Real.toNNReal p :=
NNReal.eq <| by simp [hr, hp, add_nonneg]
#align real.to_nnreal_add Real.toNNReal_add
theorem toNNReal_add_toNNReal {r p : ℝ} (hr : 0 ≤ r) (hp : 0 ≤ p) :
Real.toNNReal r + Real.toNNReal p = Real.toNNReal (r + p) :=
(Real.toNNReal_add hr hp).symm
#align real.to_nnreal_add_to_nnreal Real.toNNReal_add_toNNReal
theorem toNNReal_le_toNNReal {r p : ℝ} (h : r ≤ p) : Real.toNNReal r ≤ Real.toNNReal p :=
Real.toNNReal_mono h
#align real.to_nnreal_le_to_nnreal Real.toNNReal_le_toNNReal
theorem toNNReal_add_le {r p : ℝ} : Real.toNNReal (r + p) ≤ Real.toNNReal r + Real.toNNReal p :=
NNReal.coe_le_coe.1 <| max_le (add_le_add (le_max_left _ _) (le_max_left _ _)) NNReal.zero_le_coe
#align real.to_nnreal_add_le Real.toNNReal_add_le
theorem toNNReal_le_iff_le_coe {r : ℝ} {p : ℝ≥0} : toNNReal r ≤ p ↔ r ≤ ↑p :=
NNReal.gi.gc r p
#align real.to_nnreal_le_iff_le_coe Real.toNNReal_le_iff_le_coe
theorem le_toNNReal_iff_coe_le {r : ℝ≥0} {p : ℝ} (hp : 0 ≤ p) : r ≤ Real.toNNReal p ↔ ↑r ≤ p := by
rw [← NNReal.coe_le_coe, Real.coe_toNNReal p hp]
#align real.le_to_nnreal_iff_coe_le Real.le_toNNReal_iff_coe_le
theorem le_toNNReal_iff_coe_le' {r : ℝ≥0} {p : ℝ} (hr : 0 < r) : r ≤ Real.toNNReal p ↔ ↑r ≤ p :=
(le_or_lt 0 p).elim le_toNNReal_iff_coe_le fun hp => by
simp only [(hp.trans_le r.coe_nonneg).not_le, toNNReal_eq_zero.2 hp.le, hr.not_le]
#align real.le_to_nnreal_iff_coe_le' Real.le_toNNReal_iff_coe_le'
theorem toNNReal_lt_iff_lt_coe {r : ℝ} {p : ℝ≥0} (ha : 0 ≤ r) : Real.toNNReal r < p ↔ r < ↑p := by
rw [← NNReal.coe_lt_coe, Real.coe_toNNReal r ha]
#align real.to_nnreal_lt_iff_lt_coe Real.toNNReal_lt_iff_lt_coe
theorem lt_toNNReal_iff_coe_lt {r : ℝ≥0} {p : ℝ} : r < Real.toNNReal p ↔ ↑r < p :=
lt_iff_lt_of_le_iff_le toNNReal_le_iff_le_coe
#align real.lt_to_nnreal_iff_coe_lt Real.lt_toNNReal_iff_coe_lt
#noalign real.to_nnreal_bit0
#noalign real.to_nnreal_bit1
theorem toNNReal_pow {x : ℝ} (hx : 0 ≤ x) (n : ℕ) : (x ^ n).toNNReal = x.toNNReal ^ n := by
rw [← coe_inj, NNReal.coe_pow, Real.coe_toNNReal _ (pow_nonneg hx _),
Real.coe_toNNReal x hx]
#align real.to_nnreal_pow Real.toNNReal_pow
theorem toNNReal_mul {p q : ℝ} (hp : 0 ≤ p) :
Real.toNNReal (p * q) = Real.toNNReal p * Real.toNNReal q :=
NNReal.eq <| by simp [mul_max_of_nonneg, hp]
#align real.to_nnreal_mul Real.toNNReal_mul
end ToNNReal
end Real
open Real
namespace NNReal
section Mul
theorem mul_eq_mul_left {a b c : ℝ≥0} (h : a ≠ 0) : a * b = a * c ↔ b = c := by
rw [mul_eq_mul_left_iff, or_iff_left h]
#align nnreal.mul_eq_mul_left NNReal.mul_eq_mul_left
end Mul
section Pow
theorem pow_antitone_exp {a : ℝ≥0} (m n : ℕ) (mn : m ≤ n) (a1 : a ≤ 1) : a ^ n ≤ a ^ m :=
pow_le_pow_of_le_one (zero_le a) a1 mn
#align nnreal.pow_antitone_exp NNReal.pow_antitone_exp
nonrec theorem exists_pow_lt_of_lt_one {a b : ℝ≥0} (ha : 0 < a) (hb : b < 1) :
∃ n : ℕ, b ^ n < a := by
simpa only [← coe_pow, NNReal.coe_lt_coe] using
exists_pow_lt_of_lt_one (NNReal.coe_pos.2 ha) (NNReal.coe_lt_coe.2 hb)
#align nnreal.exists_pow_lt_of_lt_one NNReal.exists_pow_lt_of_lt_one
nonrec theorem exists_mem_Ico_zpow {x : ℝ≥0} {y : ℝ≥0} (hx : x ≠ 0) (hy : 1 < y) :
∃ n : ℤ, x ∈ Set.Ico (y ^ n) (y ^ (n + 1)) :=
exists_mem_Ico_zpow (α := ℝ) hx.bot_lt hy
#align nnreal.exists_mem_Ico_zpow NNReal.exists_mem_Ico_zpow
nonrec theorem exists_mem_Ioc_zpow {x : ℝ≥0} {y : ℝ≥0} (hx : x ≠ 0) (hy : 1 < y) :
∃ n : ℤ, x ∈ Set.Ioc (y ^ n) (y ^ (n + 1)) :=
exists_mem_Ioc_zpow (α := ℝ) hx.bot_lt hy
#align nnreal.exists_mem_Ioc_zpow NNReal.exists_mem_Ioc_zpow
end Pow
section Sub
/-!
### Lemmas about subtraction
In this section we provide a few lemmas about subtraction that do not fit well into any other
typeclass. For lemmas about subtraction and addition see lemmas about `OrderedSub` in the file
`Mathlib.Algebra.Order.Sub.Basic`. See also `mul_tsub` and `tsub_mul`.
-/
theorem sub_def {r p : ℝ≥0} : r - p = Real.toNNReal (r - p) :=
rfl
#align nnreal.sub_def NNReal.sub_def
theorem coe_sub_def {r p : ℝ≥0} : ↑(r - p) = max (r - p : ℝ) 0 :=
rfl
#align nnreal.coe_sub_def NNReal.coe_sub_def
example : OrderedSub ℝ≥0 := by infer_instance
theorem sub_div (a b c : ℝ≥0) : (a - b) / c = a / c - b / c :=
tsub_div _ _ _
#align nnreal.sub_div NNReal.sub_div
end Sub
section Inv
#align nnreal.sum_div Finset.sum_div
@[simp]
theorem inv_le {r p : ℝ≥0} (h : r ≠ 0) : r⁻¹ ≤ p ↔ 1 ≤ r * p := by
rw [← mul_le_mul_left (pos_iff_ne_zero.2 h), mul_inv_cancel h]
#align nnreal.inv_le NNReal.inv_le
theorem inv_le_of_le_mul {r p : ℝ≥0} (h : 1 ≤ r * p) : r⁻¹ ≤ p := by
by_cases r = 0 <;> simp [*, inv_le]
#align nnreal.inv_le_of_le_mul NNReal.inv_le_of_le_mul
@[simp]
theorem le_inv_iff_mul_le {r p : ℝ≥0} (h : p ≠ 0) : r ≤ p⁻¹ ↔ r * p ≤ 1 := by
rw [← mul_le_mul_left (pos_iff_ne_zero.2 h), mul_inv_cancel h, mul_comm]
#align nnreal.le_inv_iff_mul_le NNReal.le_inv_iff_mul_le
@[simp]
theorem lt_inv_iff_mul_lt {r p : ℝ≥0} (h : p ≠ 0) : r < p⁻¹ ↔ r * p < 1 := by
rw [← mul_lt_mul_left (pos_iff_ne_zero.2 h), mul_inv_cancel h, mul_comm]
#align nnreal.lt_inv_iff_mul_lt NNReal.lt_inv_iff_mul_lt
theorem mul_le_iff_le_inv {a b r : ℝ≥0} (hr : r ≠ 0) : r * a ≤ b ↔ a ≤ r⁻¹ * b := by
have : 0 < r := lt_of_le_of_ne (zero_le r) hr.symm
rw [← mul_le_mul_left (inv_pos.mpr this), ← mul_assoc, inv_mul_cancel hr, one_mul]
#align nnreal.mul_le_iff_le_inv NNReal.mul_le_iff_le_inv
theorem le_div_iff_mul_le {a b r : ℝ≥0} (hr : r ≠ 0) : a ≤ b / r ↔ a * r ≤ b :=
le_div_iff₀ hr
#align nnreal.le_div_iff_mul_le NNReal.le_div_iff_mul_le
theorem div_le_iff {a b r : ℝ≥0} (hr : r ≠ 0) : a / r ≤ b ↔ a ≤ b * r :=
div_le_iff₀ hr
#align nnreal.div_le_iff NNReal.div_le_iff
nonrec theorem div_le_iff' {a b r : ℝ≥0} (hr : r ≠ 0) : a / r ≤ b ↔ a ≤ r * b :=
@div_le_iff' ℝ _ a r b <| pos_iff_ne_zero.2 hr
#align nnreal.div_le_iff' NNReal.div_le_iff'
theorem div_le_of_le_mul {a b c : ℝ≥0} (h : a ≤ b * c) : a / c ≤ b :=
if h0 : c = 0 then by simp [h0] else (div_le_iff h0).2 h
#align nnreal.div_le_of_le_mul NNReal.div_le_of_le_mul
theorem div_le_of_le_mul' {a b c : ℝ≥0} (h : a ≤ b * c) : a / b ≤ c :=
div_le_of_le_mul <| mul_comm b c ▸ h
#align nnreal.div_le_of_le_mul' NNReal.div_le_of_le_mul'
nonrec theorem le_div_iff {a b r : ℝ≥0} (hr : r ≠ 0) : a ≤ b / r ↔ a * r ≤ b :=
@le_div_iff ℝ _ a b r <| pos_iff_ne_zero.2 hr
#align nnreal.le_div_iff NNReal.le_div_iff
nonrec theorem le_div_iff' {a b r : ℝ≥0} (hr : r ≠ 0) : a ≤ b / r ↔ r * a ≤ b :=
@le_div_iff' ℝ _ a b r <| pos_iff_ne_zero.2 hr
#align nnreal.le_div_iff' NNReal.le_div_iff'
theorem div_lt_iff {a b r : ℝ≥0} (hr : r ≠ 0) : a / r < b ↔ a < b * r :=
lt_iff_lt_of_le_iff_le (le_div_iff hr)
#align nnreal.div_lt_iff NNReal.div_lt_iff
theorem div_lt_iff' {a b r : ℝ≥0} (hr : r ≠ 0) : a / r < b ↔ a < r * b :=
lt_iff_lt_of_le_iff_le (le_div_iff' hr)
#align nnreal.div_lt_iff' NNReal.div_lt_iff'
theorem lt_div_iff {a b r : ℝ≥0} (hr : r ≠ 0) : a < b / r ↔ a * r < b :=
lt_iff_lt_of_le_iff_le (div_le_iff hr)
#align nnreal.lt_div_iff NNReal.lt_div_iff
theorem lt_div_iff' {a b r : ℝ≥0} (hr : r ≠ 0) : a < b / r ↔ r * a < b :=
lt_iff_lt_of_le_iff_le (div_le_iff' hr)
#align nnreal.lt_div_iff' NNReal.lt_div_iff'
theorem mul_lt_of_lt_div {a b r : ℝ≥0} (h : a < b / r) : a * r < b :=
(lt_div_iff fun hr => False.elim <| by simp [hr] at h).1 h
#align nnreal.mul_lt_of_lt_div NNReal.mul_lt_of_lt_div
theorem div_le_div_left_of_le {a b c : ℝ≥0} (c0 : c ≠ 0) (cb : c ≤ b) :
a / b ≤ a / c :=
div_le_div_of_nonneg_left (zero_le _) c0.bot_lt cb
#align nnreal.div_le_div_left_of_le NNReal.div_le_div_left_of_leₓ
nonrec theorem div_le_div_left {a b c : ℝ≥0} (a0 : 0 < a) (b0 : 0 < b) (c0 : 0 < c) :
a / b ≤ a / c ↔ c ≤ b :=
div_le_div_left a0 b0 c0
#align nnreal.div_le_div_left NNReal.div_le_div_left
theorem le_of_forall_lt_one_mul_le {x y : ℝ≥0} (h : ∀ a < 1, a * x ≤ y) : x ≤ y :=
le_of_forall_ge_of_dense fun a ha => by
have hx : x ≠ 0 := pos_iff_ne_zero.1 (lt_of_le_of_lt (zero_le _) ha)
have hx' : x⁻¹ ≠ 0 := by rwa [Ne, inv_eq_zero]
have : a * x⁻¹ < 1 := by rwa [← lt_inv_iff_mul_lt hx', inv_inv]
have : a * x⁻¹ * x ≤ y := h _ this
rwa [mul_assoc, inv_mul_cancel hx, mul_one] at this
#align nnreal.le_of_forall_lt_one_mul_le NNReal.le_of_forall_lt_one_mul_le
nonrec theorem half_le_self (a : ℝ≥0) : a / 2 ≤ a :=
half_le_self bot_le
#align nnreal.half_le_self NNReal.half_le_self
nonrec theorem half_lt_self {a : ℝ≥0} (h : a ≠ 0) : a / 2 < a :=
half_lt_self h.bot_lt
#align nnreal.half_lt_self NNReal.half_lt_self
theorem div_lt_one_of_lt {a b : ℝ≥0} (h : a < b) : a / b < 1 := by
rwa [div_lt_iff, one_mul]
exact ne_of_gt (lt_of_le_of_lt (zero_le _) h)
#align nnreal.div_lt_one_of_lt NNReal.div_lt_one_of_lt
theorem _root_.Real.toNNReal_inv {x : ℝ} : Real.toNNReal x⁻¹ = (Real.toNNReal x)⁻¹ := by
rcases le_total 0 x with hx | hx
· nth_rw 1 [← Real.coe_toNNReal x hx]
rw [← NNReal.coe_inv, Real.toNNReal_coe]
· rw [toNNReal_eq_zero.mpr hx, inv_zero, toNNReal_eq_zero.mpr (inv_nonpos.mpr hx)]
#align real.to_nnreal_inv Real.toNNReal_inv
theorem _root_.Real.toNNReal_div {x y : ℝ} (hx : 0 ≤ x) :
Real.toNNReal (x / y) = Real.toNNReal x / Real.toNNReal y := by
rw [div_eq_mul_inv, div_eq_mul_inv, ← Real.toNNReal_inv, ← Real.toNNReal_mul hx]
#align real.to_nnreal_div Real.toNNReal_div
theorem _root_.Real.toNNReal_div' {x y : ℝ} (hy : 0 ≤ y) :
Real.toNNReal (x / y) = Real.toNNReal x / Real.toNNReal y := by
rw [div_eq_inv_mul, div_eq_inv_mul, Real.toNNReal_mul (inv_nonneg.2 hy), Real.toNNReal_inv]
#align real.to_nnreal_div' Real.toNNReal_div'
theorem inv_lt_one_iff {x : ℝ≥0} (hx : x ≠ 0) : x⁻¹ < 1 ↔ 1 < x := by
rw [← one_div, div_lt_iff hx, one_mul]
#align nnreal.inv_lt_one_iff NNReal.inv_lt_one_iff
theorem zpow_pos {x : ℝ≥0} (hx : x ≠ 0) (n : ℤ) : 0 < x ^ n :=
zpow_pos_of_pos hx.bot_lt _
#align nnreal.zpow_pos NNReal.zpow_pos
theorem inv_lt_inv {x y : ℝ≥0} (hx : x ≠ 0) (h : x < y) : y⁻¹ < x⁻¹ :=
inv_lt_inv_of_lt hx.bot_lt h
#align nnreal.inv_lt_inv NNReal.inv_lt_inv
end Inv
@[simp]
theorem abs_eq (x : ℝ≥0) : |(x : ℝ)| = x :=
abs_of_nonneg x.property
#align nnreal.abs_eq NNReal.abs_eq
section Csupr
open Set
variable {ι : Sort*} {f : ι → ℝ≥0}
theorem le_toNNReal_of_coe_le {x : ℝ≥0} {y : ℝ} (h : ↑x ≤ y) : x ≤ y.toNNReal :=
(le_toNNReal_iff_coe_le <| x.2.trans h).2 h
#align nnreal.le_to_nnreal_of_coe_le NNReal.le_toNNReal_of_coe_le
nonrec theorem sSup_of_not_bddAbove {s : Set ℝ≥0} (hs : ¬BddAbove s) : SupSet.sSup s = 0 := by
rw [← bddAbove_coe] at hs
rw [← coe_inj, coe_sSup, NNReal.coe_zero]
exact sSup_of_not_bddAbove hs
#align nnreal.Sup_of_not_bdd_above NNReal.sSup_of_not_bddAbove
theorem iSup_of_not_bddAbove (hf : ¬BddAbove (range f)) : ⨆ i, f i = 0 :=
sSup_of_not_bddAbove hf
#align nnreal.supr_of_not_bdd_above NNReal.iSup_of_not_bddAbove
theorem iSup_empty [IsEmpty ι] (f : ι → ℝ≥0) : ⨆ i, f i = 0 := ciSup_of_empty f
theorem iInf_empty [IsEmpty ι] (f : ι → ℝ≥0) : ⨅ i, f i = 0 := by
rw [_root_.iInf_of_isEmpty, sInf_empty]
#align nnreal.infi_empty NNReal.iInf_empty
@[simp]
theorem iInf_const_zero {α : Sort*} : ⨅ _ : α, (0 : ℝ≥0) = 0 := by
rw [← coe_inj, coe_iInf]
exact Real.ciInf_const_zero
#align nnreal.infi_const_zero NNReal.iInf_const_zero
theorem iInf_mul (f : ι → ℝ≥0) (a : ℝ≥0) : iInf f * a = ⨅ i, f i * a := by
rw [← coe_inj, NNReal.coe_mul, coe_iInf, coe_iInf]
exact Real.iInf_mul_of_nonneg (NNReal.coe_nonneg _) _
#align nnreal.infi_mul NNReal.iInf_mul
theorem mul_iInf (f : ι → ℝ≥0) (a : ℝ≥0) : a * iInf f = ⨅ i, a * f i := by
simpa only [mul_comm] using iInf_mul f a
#align nnreal.mul_infi NNReal.mul_iInf
theorem mul_iSup (f : ι → ℝ≥0) (a : ℝ≥0) : (a * ⨆ i, f i) = ⨆ i, a * f i := by
rw [← coe_inj, NNReal.coe_mul, NNReal.coe_iSup, NNReal.coe_iSup]
exact Real.mul_iSup_of_nonneg (NNReal.coe_nonneg _) _
#align nnreal.mul_supr NNReal.mul_iSup
| Mathlib/Data/Real/NNReal.lean | 1,104 | 1,106 | theorem iSup_mul (f : ι → ℝ≥0) (a : ℝ≥0) : (⨆ i, f i) * a = ⨆ i, f i * a := by |
rw [mul_comm, mul_iSup]
simp_rw [mul_comm]
|
/-
Copyright (c) 2016 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad, Leonardo de Moura, Mario Carneiro, Yaël Dillies
-/
import Mathlib.Algebra.CharZero.Defs
import Mathlib.Algebra.Group.Pi.Basic
import Mathlib.Algebra.Group.Units
import Mathlib.Algebra.GroupWithZero.NeZero
import Mathlib.Algebra.Order.Group.Defs
import Mathlib.Algebra.Order.GroupWithZero.Unbundled
import Mathlib.Algebra.Order.Monoid.Canonical.Defs
import Mathlib.Algebra.Order.Monoid.NatCast
import Mathlib.Algebra.Order.Monoid.Unbundled.MinMax
import Mathlib.Algebra.Ring.Defs
import Mathlib.Tactic.Tauto
#align_import algebra.order.ring.char_zero from "leanprover-community/mathlib"@"655994e298904d7e5bbd1e18c95defd7b543eb94"
#align_import algebra.order.ring.defs from "leanprover-community/mathlib"@"44e29dbcff83ba7114a464d592b8c3743987c1e5"
/-!
# Ordered rings and semirings
This file develops the basics of ordered (semi)rings.
Each typeclass here comprises
* an algebraic class (`Semiring`, `CommSemiring`, `Ring`, `CommRing`)
* an order class (`PartialOrder`, `LinearOrder`)
* assumptions on how both interact ((strict) monotonicity, canonicity)
For short,
* "`+` respects `≤`" means "monotonicity of addition"
* "`+` respects `<`" means "strict monotonicity of addition"
* "`*` respects `≤`" means "monotonicity of multiplication by a nonnegative number".
* "`*` respects `<`" means "strict monotonicity of multiplication by a positive number".
## Typeclasses
* `OrderedSemiring`: Semiring with a partial order such that `+` and `*` respect `≤`.
* `StrictOrderedSemiring`: Nontrivial semiring with a partial order such that `+` and `*` respects
`<`.
* `OrderedCommSemiring`: Commutative semiring with a partial order such that `+` and `*` respect
`≤`.
* `StrictOrderedCommSemiring`: Nontrivial commutative semiring with a partial order such that `+`
and `*` respect `<`.
* `OrderedRing`: Ring with a partial order such that `+` respects `≤` and `*` respects `<`.
* `OrderedCommRing`: Commutative ring with a partial order such that `+` respects `≤` and
`*` respects `<`.
* `LinearOrderedSemiring`: Nontrivial semiring with a linear order such that `+` respects `≤` and
`*` respects `<`.
* `LinearOrderedCommSemiring`: Nontrivial commutative semiring with a linear order such that `+`
respects `≤` and `*` respects `<`.
* `LinearOrderedRing`: Nontrivial ring with a linear order such that `+` respects `≤` and `*`
respects `<`.
* `LinearOrderedCommRing`: Nontrivial commutative ring with a linear order such that `+` respects
`≤` and `*` respects `<`.
* `CanonicallyOrderedCommSemiring`: Commutative semiring with a partial order such that `+`
respects `≤`, `*` respects `<`, and `a ≤ b ↔ ∃ c, b = a + c`.
## Hierarchy
The hardest part of proving order lemmas might be to figure out the correct generality and its
corresponding typeclass. Here's an attempt at demystifying it. For each typeclass, we list its
immediate predecessors and what conditions are added to each of them.
* `OrderedSemiring`
- `OrderedAddCommMonoid` & multiplication & `*` respects `≤`
- `Semiring` & partial order structure & `+` respects `≤` & `*` respects `≤`
* `StrictOrderedSemiring`
- `OrderedCancelAddCommMonoid` & multiplication & `*` respects `<` & nontriviality
- `OrderedSemiring` & `+` respects `<` & `*` respects `<` & nontriviality
* `OrderedCommSemiring`
- `OrderedSemiring` & commutativity of multiplication
- `CommSemiring` & partial order structure & `+` respects `≤` & `*` respects `<`
* `StrictOrderedCommSemiring`
- `StrictOrderedSemiring` & commutativity of multiplication
- `OrderedCommSemiring` & `+` respects `<` & `*` respects `<` & nontriviality
* `OrderedRing`
- `OrderedSemiring` & additive inverses
- `OrderedAddCommGroup` & multiplication & `*` respects `<`
- `Ring` & partial order structure & `+` respects `≤` & `*` respects `<`
* `StrictOrderedRing`
- `StrictOrderedSemiring` & additive inverses
- `OrderedSemiring` & `+` respects `<` & `*` respects `<` & nontriviality
* `OrderedCommRing`
- `OrderedRing` & commutativity of multiplication
- `OrderedCommSemiring` & additive inverses
- `CommRing` & partial order structure & `+` respects `≤` & `*` respects `<`
* `StrictOrderedCommRing`
- `StrictOrderedCommSemiring` & additive inverses
- `StrictOrderedRing` & commutativity of multiplication
- `OrderedCommRing` & `+` respects `<` & `*` respects `<` & nontriviality
* `LinearOrderedSemiring`
- `StrictOrderedSemiring` & totality of the order
- `LinearOrderedAddCommMonoid` & multiplication & nontriviality & `*` respects `<`
* `LinearOrderedCommSemiring`
- `StrictOrderedCommSemiring` & totality of the order
- `LinearOrderedSemiring` & commutativity of multiplication
* `LinearOrderedRing`
- `StrictOrderedRing` & totality of the order
- `LinearOrderedSemiring` & additive inverses
- `LinearOrderedAddCommGroup` & multiplication & `*` respects `<`
- `Ring` & `IsDomain` & linear order structure
* `LinearOrderedCommRing`
- `StrictOrderedCommRing` & totality of the order
- `LinearOrderedRing` & commutativity of multiplication
- `LinearOrderedCommSemiring` & additive inverses
- `CommRing` & `IsDomain` & linear order structure
-/
open Function
universe u
variable {α : Type u} {β : Type*}
/-! Note that `OrderDual` does not satisfy any of the ordered ring typeclasses due to the
`zero_le_one` field. -/
theorem add_one_le_two_mul [LE α] [Semiring α] [CovariantClass α α (· + ·) (· ≤ ·)] {a : α}
(a1 : 1 ≤ a) : a + 1 ≤ 2 * a :=
calc
a + 1 ≤ a + a := add_le_add_left a1 a
_ = 2 * a := (two_mul _).symm
#align add_one_le_two_mul add_one_le_two_mul
/-- An `OrderedSemiring` is a semiring with a partial order such that addition is monotone and
multiplication by a nonnegative number is monotone. -/
class OrderedSemiring (α : Type u) extends Semiring α, OrderedAddCommMonoid α where
/-- `0 ≤ 1` in any ordered semiring. -/
protected zero_le_one : (0 : α) ≤ 1
/-- In an ordered semiring, we can multiply an inequality `a ≤ b` on the left
by a non-negative element `0 ≤ c` to obtain `c * a ≤ c * b`. -/
protected mul_le_mul_of_nonneg_left : ∀ a b c : α, a ≤ b → 0 ≤ c → c * a ≤ c * b
/-- In an ordered semiring, we can multiply an inequality `a ≤ b` on the right
by a non-negative element `0 ≤ c` to obtain `a * c ≤ b * c`. -/
protected mul_le_mul_of_nonneg_right : ∀ a b c : α, a ≤ b → 0 ≤ c → a * c ≤ b * c
#align ordered_semiring OrderedSemiring
/-- An `OrderedCommSemiring` is a commutative semiring with a partial order such that addition is
monotone and multiplication by a nonnegative number is monotone. -/
class OrderedCommSemiring (α : Type u) extends OrderedSemiring α, CommSemiring α where
mul_le_mul_of_nonneg_right a b c ha hc :=
-- parentheses ensure this generates an `optParam` rather than an `autoParam`
(by simpa only [mul_comm] using mul_le_mul_of_nonneg_left a b c ha hc)
#align ordered_comm_semiring OrderedCommSemiring
/-- An `OrderedRing` is a ring with a partial order such that addition is monotone and
multiplication by a nonnegative number is monotone. -/
class OrderedRing (α : Type u) extends Ring α, OrderedAddCommGroup α where
/-- `0 ≤ 1` in any ordered ring. -/
protected zero_le_one : 0 ≤ (1 : α)
/-- The product of non-negative elements is non-negative. -/
protected mul_nonneg : ∀ a b : α, 0 ≤ a → 0 ≤ b → 0 ≤ a * b
#align ordered_ring OrderedRing
/-- An `OrderedCommRing` is a commutative ring with a partial order such that addition is monotone
and multiplication by a nonnegative number is monotone. -/
class OrderedCommRing (α : Type u) extends OrderedRing α, CommRing α
#align ordered_comm_ring OrderedCommRing
/-- A `StrictOrderedSemiring` is a nontrivial semiring with a partial order such that addition is
strictly monotone and multiplication by a positive number is strictly monotone. -/
class StrictOrderedSemiring (α : Type u) extends Semiring α, OrderedCancelAddCommMonoid α,
Nontrivial α where
/-- In a strict ordered semiring, `0 ≤ 1`. -/
protected zero_le_one : (0 : α) ≤ 1
/-- Left multiplication by a positive element is strictly monotone. -/
protected mul_lt_mul_of_pos_left : ∀ a b c : α, a < b → 0 < c → c * a < c * b
/-- Right multiplication by a positive element is strictly monotone. -/
protected mul_lt_mul_of_pos_right : ∀ a b c : α, a < b → 0 < c → a * c < b * c
#align strict_ordered_semiring StrictOrderedSemiring
/-- A `StrictOrderedCommSemiring` is a commutative semiring with a partial order such that
addition is strictly monotone and multiplication by a positive number is strictly monotone. -/
class StrictOrderedCommSemiring (α : Type u) extends StrictOrderedSemiring α, CommSemiring α
#align strict_ordered_comm_semiring StrictOrderedCommSemiring
/-- A `StrictOrderedRing` is a ring with a partial order such that addition is strictly monotone
and multiplication by a positive number is strictly monotone. -/
class StrictOrderedRing (α : Type u) extends Ring α, OrderedAddCommGroup α, Nontrivial α where
/-- In a strict ordered ring, `0 ≤ 1`. -/
protected zero_le_one : 0 ≤ (1 : α)
/-- The product of two positive elements is positive. -/
protected mul_pos : ∀ a b : α, 0 < a → 0 < b → 0 < a * b
#align strict_ordered_ring StrictOrderedRing
/-- A `StrictOrderedCommRing` is a commutative ring with a partial order such that addition is
strictly monotone and multiplication by a positive number is strictly monotone. -/
class StrictOrderedCommRing (α : Type*) extends StrictOrderedRing α, CommRing α
#align strict_ordered_comm_ring StrictOrderedCommRing
/- It's not entirely clear we should assume `Nontrivial` at this point; it would be reasonable to
explore changing this, but be warned that the instances involving `Domain` may cause typeclass
search loops. -/
/-- A `LinearOrderedSemiring` is a nontrivial semiring with a linear order such that
addition is monotone and multiplication by a positive number is strictly monotone. -/
class LinearOrderedSemiring (α : Type u) extends StrictOrderedSemiring α,
LinearOrderedAddCommMonoid α
#align linear_ordered_semiring LinearOrderedSemiring
/-- A `LinearOrderedCommSemiring` is a nontrivial commutative semiring with a linear order such
that addition is monotone and multiplication by a positive number is strictly monotone. -/
class LinearOrderedCommSemiring (α : Type*) extends StrictOrderedCommSemiring α,
LinearOrderedSemiring α
#align linear_ordered_comm_semiring LinearOrderedCommSemiring
/-- A `LinearOrderedRing` is a ring with a linear order such that addition is monotone and
multiplication by a positive number is strictly monotone. -/
class LinearOrderedRing (α : Type u) extends StrictOrderedRing α, LinearOrder α
#align linear_ordered_ring LinearOrderedRing
/-- A `LinearOrderedCommRing` is a commutative ring with a linear order such that addition is
monotone and multiplication by a positive number is strictly monotone. -/
class LinearOrderedCommRing (α : Type u) extends LinearOrderedRing α, CommMonoid α
#align linear_ordered_comm_ring LinearOrderedCommRing
section OrderedSemiring
variable [OrderedSemiring α] {a b c d : α}
-- see Note [lower instance priority]
instance (priority := 100) OrderedSemiring.zeroLEOneClass : ZeroLEOneClass α :=
{ ‹OrderedSemiring α› with }
#align ordered_semiring.zero_le_one_class OrderedSemiring.zeroLEOneClass
-- see Note [lower instance priority]
instance (priority := 200) OrderedSemiring.toPosMulMono : PosMulMono α :=
⟨fun x _ _ h => OrderedSemiring.mul_le_mul_of_nonneg_left _ _ _ h x.2⟩
#align ordered_semiring.to_pos_mul_mono OrderedSemiring.toPosMulMono
-- see Note [lower instance priority]
instance (priority := 200) OrderedSemiring.toMulPosMono : MulPosMono α :=
⟨fun x _ _ h => OrderedSemiring.mul_le_mul_of_nonneg_right _ _ _ h x.2⟩
#align ordered_semiring.to_mul_pos_mono OrderedSemiring.toMulPosMono
set_option linter.deprecated false in
theorem bit1_mono : Monotone (bit1 : α → α) := fun _ _ h => add_le_add_right (bit0_mono h) _
#align bit1_mono bit1_mono
@[simp]
theorem pow_nonneg (H : 0 ≤ a) : ∀ n : ℕ, 0 ≤ a ^ n
| 0 => by
rw [pow_zero]
exact zero_le_one
| n + 1 => by
rw [pow_succ]
exact mul_nonneg (pow_nonneg H _) H
#align pow_nonneg pow_nonneg
lemma pow_le_pow_of_le_one (ha₀ : 0 ≤ a) (ha₁ : a ≤ 1) : ∀ {m n : ℕ}, m ≤ n → a ^ n ≤ a ^ m
| _, _, Nat.le.refl => le_rfl
| _, _, Nat.le.step h => by
rw [pow_succ']
exact (mul_le_of_le_one_left (pow_nonneg ha₀ _) ha₁).trans $ pow_le_pow_of_le_one ha₀ ha₁ h
#align pow_le_pow_of_le_one pow_le_pow_of_le_one
lemma pow_le_of_le_one (h₀ : 0 ≤ a) (h₁ : a ≤ 1) {n : ℕ} (hn : n ≠ 0) : a ^ n ≤ a :=
(pow_one a).subst (pow_le_pow_of_le_one h₀ h₁ (Nat.pos_of_ne_zero hn))
#align pow_le_of_le_one pow_le_of_le_one
lemma sq_le (h₀ : 0 ≤ a) (h₁ : a ≤ 1) : a ^ 2 ≤ a := pow_le_of_le_one h₀ h₁ two_ne_zero
#align sq_le sq_le
-- Porting note: it's unfortunate we need to write `(@one_le_two α)` here.
theorem add_le_mul_two_add (a2 : 2 ≤ a) (b0 : 0 ≤ b) : a + (2 + b) ≤ a * (2 + b) :=
calc
a + (2 + b) ≤ a + (a + a * b) :=
add_le_add_left (add_le_add a2 <| le_mul_of_one_le_left b0 <| (@one_le_two α).trans a2) a
_ ≤ a * (2 + b) := by rw [mul_add, mul_two, add_assoc]
#align add_le_mul_two_add add_le_mul_two_add
theorem one_le_mul_of_one_le_of_one_le (ha : 1 ≤ a) (hb : 1 ≤ b) : (1 : α) ≤ a * b :=
Left.one_le_mul_of_le_of_le ha hb <| zero_le_one.trans ha
#align one_le_mul_of_one_le_of_one_le one_le_mul_of_one_le_of_one_le
section Monotone
variable [Preorder β] {f g : β → α}
theorem monotone_mul_left_of_nonneg (ha : 0 ≤ a) : Monotone fun x => a * x := fun _ _ h =>
mul_le_mul_of_nonneg_left h ha
#align monotone_mul_left_of_nonneg monotone_mul_left_of_nonneg
theorem monotone_mul_right_of_nonneg (ha : 0 ≤ a) : Monotone fun x => x * a := fun _ _ h =>
mul_le_mul_of_nonneg_right h ha
#align monotone_mul_right_of_nonneg monotone_mul_right_of_nonneg
theorem Monotone.mul_const (hf : Monotone f) (ha : 0 ≤ a) : Monotone fun x => f x * a :=
(monotone_mul_right_of_nonneg ha).comp hf
#align monotone.mul_const Monotone.mul_const
theorem Monotone.const_mul (hf : Monotone f) (ha : 0 ≤ a) : Monotone fun x => a * f x :=
(monotone_mul_left_of_nonneg ha).comp hf
#align monotone.const_mul Monotone.const_mul
theorem Antitone.mul_const (hf : Antitone f) (ha : 0 ≤ a) : Antitone fun x => f x * a :=
(monotone_mul_right_of_nonneg ha).comp_antitone hf
#align antitone.mul_const Antitone.mul_const
theorem Antitone.const_mul (hf : Antitone f) (ha : 0 ≤ a) : Antitone fun x => a * f x :=
(monotone_mul_left_of_nonneg ha).comp_antitone hf
#align antitone.const_mul Antitone.const_mul
theorem Monotone.mul (hf : Monotone f) (hg : Monotone g) (hf₀ : ∀ x, 0 ≤ f x) (hg₀ : ∀ x, 0 ≤ g x) :
Monotone (f * g) := fun _ _ h => mul_le_mul (hf h) (hg h) (hg₀ _) (hf₀ _)
#align monotone.mul Monotone.mul
end Monotone
section
set_option linter.deprecated false
theorem bit1_pos [Nontrivial α] (h : 0 ≤ a) : 0 < bit1 a :=
zero_lt_one.trans_le <| bit1_zero.symm.trans_le <| bit1_mono h
#align bit1_pos bit1_pos
theorem bit1_pos' (h : 0 < a) : 0 < bit1 a := by
nontriviality
exact bit1_pos h.le
#align bit1_pos' bit1_pos'
end
theorem mul_le_one (ha : a ≤ 1) (hb' : 0 ≤ b) (hb : b ≤ 1) : a * b ≤ 1 :=
one_mul (1 : α) ▸ mul_le_mul ha hb hb' zero_le_one
#align mul_le_one mul_le_one
theorem one_lt_mul_of_le_of_lt (ha : 1 ≤ a) (hb : 1 < b) : 1 < a * b :=
hb.trans_le <| le_mul_of_one_le_left (zero_le_one.trans hb.le) ha
#align one_lt_mul_of_le_of_lt one_lt_mul_of_le_of_lt
theorem one_lt_mul_of_lt_of_le (ha : 1 < a) (hb : 1 ≤ b) : 1 < a * b :=
ha.trans_le <| le_mul_of_one_le_right (zero_le_one.trans ha.le) hb
#align one_lt_mul_of_lt_of_le one_lt_mul_of_lt_of_le
alias one_lt_mul := one_lt_mul_of_le_of_lt
#align one_lt_mul one_lt_mul
theorem mul_lt_one_of_nonneg_of_lt_one_left (ha₀ : 0 ≤ a) (ha : a < 1) (hb : b ≤ 1) : a * b < 1 :=
(mul_le_of_le_one_right ha₀ hb).trans_lt ha
#align mul_lt_one_of_nonneg_of_lt_one_left mul_lt_one_of_nonneg_of_lt_one_left
theorem mul_lt_one_of_nonneg_of_lt_one_right (ha : a ≤ 1) (hb₀ : 0 ≤ b) (hb : b < 1) : a * b < 1 :=
(mul_le_of_le_one_left hb₀ ha).trans_lt hb
#align mul_lt_one_of_nonneg_of_lt_one_right mul_lt_one_of_nonneg_of_lt_one_right
variable [ExistsAddOfLE α] [ContravariantClass α α (swap (· + ·)) (· ≤ ·)]
theorem mul_le_mul_of_nonpos_left (h : b ≤ a) (hc : c ≤ 0) : c * a ≤ c * b := by
obtain ⟨d, hcd⟩ := exists_add_of_le hc
refine le_of_add_le_add_right (a := d * b + d * a) ?_
calc
_ = d * b := by rw [add_left_comm, ← add_mul, ← hcd, zero_mul, add_zero]
_ ≤ d * a := mul_le_mul_of_nonneg_left h <| hcd.trans_le <| add_le_of_nonpos_left hc
_ = _ := by rw [← add_assoc, ← add_mul, ← hcd, zero_mul, zero_add]
#align mul_le_mul_of_nonpos_left mul_le_mul_of_nonpos_left
theorem mul_le_mul_of_nonpos_right (h : b ≤ a) (hc : c ≤ 0) : a * c ≤ b * c := by
obtain ⟨d, hcd⟩ := exists_add_of_le hc
refine le_of_add_le_add_right (a := b * d + a * d) ?_
calc
_ = b * d := by rw [add_left_comm, ← mul_add, ← hcd, mul_zero, add_zero]
_ ≤ a * d := mul_le_mul_of_nonneg_right h <| hcd.trans_le <| add_le_of_nonpos_left hc
_ = _ := by rw [← add_assoc, ← mul_add, ← hcd, mul_zero, zero_add]
#align mul_le_mul_of_nonpos_right mul_le_mul_of_nonpos_right
theorem mul_nonneg_of_nonpos_of_nonpos (ha : a ≤ 0) (hb : b ≤ 0) : 0 ≤ a * b := by
simpa only [zero_mul] using mul_le_mul_of_nonpos_right ha hb
#align mul_nonneg_of_nonpos_of_nonpos mul_nonneg_of_nonpos_of_nonpos
theorem mul_le_mul_of_nonneg_of_nonpos (hca : c ≤ a) (hbd : b ≤ d) (hc : 0 ≤ c) (hb : b ≤ 0) :
a * b ≤ c * d :=
(mul_le_mul_of_nonpos_right hca hb).trans <| mul_le_mul_of_nonneg_left hbd hc
#align mul_le_mul_of_nonneg_of_nonpos mul_le_mul_of_nonneg_of_nonpos
theorem mul_le_mul_of_nonneg_of_nonpos' (hca : c ≤ a) (hbd : b ≤ d) (ha : 0 ≤ a) (hd : d ≤ 0) :
a * b ≤ c * d :=
(mul_le_mul_of_nonneg_left hbd ha).trans <| mul_le_mul_of_nonpos_right hca hd
#align mul_le_mul_of_nonneg_of_nonpos' mul_le_mul_of_nonneg_of_nonpos'
theorem mul_le_mul_of_nonpos_of_nonneg (hac : a ≤ c) (hdb : d ≤ b) (hc : c ≤ 0) (hb : 0 ≤ b) :
a * b ≤ c * d :=
(mul_le_mul_of_nonneg_right hac hb).trans <| mul_le_mul_of_nonpos_left hdb hc
#align mul_le_mul_of_nonpos_of_nonneg mul_le_mul_of_nonpos_of_nonneg
theorem mul_le_mul_of_nonpos_of_nonneg' (hca : c ≤ a) (hbd : b ≤ d) (ha : 0 ≤ a) (hd : d ≤ 0) :
a * b ≤ c * d :=
(mul_le_mul_of_nonneg_left hbd ha).trans <| mul_le_mul_of_nonpos_right hca hd
#align mul_le_mul_of_nonpos_of_nonneg' mul_le_mul_of_nonpos_of_nonneg'
theorem mul_le_mul_of_nonpos_of_nonpos (hca : c ≤ a) (hdb : d ≤ b) (hc : c ≤ 0) (hb : b ≤ 0) :
a * b ≤ c * d :=
(mul_le_mul_of_nonpos_right hca hb).trans <| mul_le_mul_of_nonpos_left hdb hc
#align mul_le_mul_of_nonpos_of_nonpos mul_le_mul_of_nonpos_of_nonpos
theorem mul_le_mul_of_nonpos_of_nonpos' (hca : c ≤ a) (hdb : d ≤ b) (ha : a ≤ 0) (hd : d ≤ 0) :
a * b ≤ c * d :=
(mul_le_mul_of_nonpos_left hdb ha).trans <| mul_le_mul_of_nonpos_right hca hd
#align mul_le_mul_of_nonpos_of_nonpos' mul_le_mul_of_nonpos_of_nonpos'
/-- Variant of `mul_le_of_le_one_left` for `b` non-positive instead of non-negative. -/
theorem le_mul_of_le_one_left (hb : b ≤ 0) (h : a ≤ 1) : b ≤ a * b := by
simpa only [one_mul] using mul_le_mul_of_nonpos_right h hb
#align le_mul_of_le_one_left le_mul_of_le_one_left
/-- Variant of `le_mul_of_one_le_left` for `b` non-positive instead of non-negative. -/
theorem mul_le_of_one_le_left (hb : b ≤ 0) (h : 1 ≤ a) : a * b ≤ b := by
simpa only [one_mul] using mul_le_mul_of_nonpos_right h hb
#align mul_le_of_one_le_left mul_le_of_one_le_left
/-- Variant of `mul_le_of_le_one_right` for `a` non-positive instead of non-negative. -/
theorem le_mul_of_le_one_right (ha : a ≤ 0) (h : b ≤ 1) : a ≤ a * b := by
simpa only [mul_one] using mul_le_mul_of_nonpos_left h ha
#align le_mul_of_le_one_right le_mul_of_le_one_right
/-- Variant of `le_mul_of_one_le_right` for `a` non-positive instead of non-negative. -/
theorem mul_le_of_one_le_right (ha : a ≤ 0) (h : 1 ≤ b) : a * b ≤ a := by
simpa only [mul_one] using mul_le_mul_of_nonpos_left h ha
#align mul_le_of_one_le_right mul_le_of_one_le_right
section Monotone
variable [Preorder β] {f g : β → α}
theorem antitone_mul_left {a : α} (ha : a ≤ 0) : Antitone (a * ·) := fun _ _ b_le_c =>
mul_le_mul_of_nonpos_left b_le_c ha
#align antitone_mul_left antitone_mul_left
theorem antitone_mul_right {a : α} (ha : a ≤ 0) : Antitone fun x => x * a := fun _ _ b_le_c =>
mul_le_mul_of_nonpos_right b_le_c ha
#align antitone_mul_right antitone_mul_right
theorem Monotone.const_mul_of_nonpos (hf : Monotone f) (ha : a ≤ 0) : Antitone fun x => a * f x :=
(antitone_mul_left ha).comp_monotone hf
#align monotone.const_mul_of_nonpos Monotone.const_mul_of_nonpos
theorem Monotone.mul_const_of_nonpos (hf : Monotone f) (ha : a ≤ 0) : Antitone fun x => f x * a :=
(antitone_mul_right ha).comp_monotone hf
#align monotone.mul_const_of_nonpos Monotone.mul_const_of_nonpos
theorem Antitone.const_mul_of_nonpos (hf : Antitone f) (ha : a ≤ 0) : Monotone fun x => a * f x :=
(antitone_mul_left ha).comp hf
#align antitone.const_mul_of_nonpos Antitone.const_mul_of_nonpos
theorem Antitone.mul_const_of_nonpos (hf : Antitone f) (ha : a ≤ 0) : Monotone fun x => f x * a :=
(antitone_mul_right ha).comp hf
#align antitone.mul_const_of_nonpos Antitone.mul_const_of_nonpos
theorem Antitone.mul_monotone (hf : Antitone f) (hg : Monotone g) (hf₀ : ∀ x, f x ≤ 0)
(hg₀ : ∀ x, 0 ≤ g x) : Antitone (f * g) := fun _ _ h =>
mul_le_mul_of_nonpos_of_nonneg (hf h) (hg h) (hf₀ _) (hg₀ _)
#align antitone.mul_monotone Antitone.mul_monotone
theorem Monotone.mul_antitone (hf : Monotone f) (hg : Antitone g) (hf₀ : ∀ x, 0 ≤ f x)
(hg₀ : ∀ x, g x ≤ 0) : Antitone (f * g) := fun _ _ h =>
mul_le_mul_of_nonneg_of_nonpos (hf h) (hg h) (hf₀ _) (hg₀ _)
#align monotone.mul_antitone Monotone.mul_antitone
theorem Antitone.mul (hf : Antitone f) (hg : Antitone g) (hf₀ : ∀ x, f x ≤ 0) (hg₀ : ∀ x, g x ≤ 0) :
Monotone (f * g) := fun _ _ h => mul_le_mul_of_nonpos_of_nonpos (hf h) (hg h) (hf₀ _) (hg₀ _)
#align antitone.mul Antitone.mul
end Monotone
variable [ContravariantClass α α (· + ·) (· ≤ ·)]
lemma le_iff_exists_nonneg_add (a b : α) : a ≤ b ↔ ∃ c ≥ 0, b = a + c := by
refine ⟨fun h ↦ ?_, ?_⟩
· obtain ⟨c, rfl⟩ := exists_add_of_le h
exact ⟨c, nonneg_of_le_add_right h, rfl⟩
· rintro ⟨c, hc, rfl⟩
exact le_add_of_nonneg_right hc
#align le_iff_exists_nonneg_add le_iff_exists_nonneg_add
end OrderedSemiring
section OrderedRing
variable [OrderedRing α] {a b c d : α}
-- see Note [lower instance priority]
instance (priority := 100) OrderedRing.toOrderedSemiring : OrderedSemiring α :=
{ ‹OrderedRing α›, (Ring.toSemiring : Semiring α) with
mul_le_mul_of_nonneg_left := fun a b c h hc => by
simpa only [mul_sub, sub_nonneg] using OrderedRing.mul_nonneg _ _ hc (sub_nonneg.2 h),
mul_le_mul_of_nonneg_right := fun a b c h hc => by
simpa only [sub_mul, sub_nonneg] using OrderedRing.mul_nonneg _ _ (sub_nonneg.2 h) hc }
#align ordered_ring.to_ordered_semiring OrderedRing.toOrderedSemiring
end OrderedRing
section OrderedCommRing
variable [OrderedCommRing α]
-- See note [lower instance priority]
instance (priority := 100) OrderedCommRing.toOrderedCommSemiring : OrderedCommSemiring α :=
{ OrderedRing.toOrderedSemiring, ‹OrderedCommRing α› with }
#align ordered_comm_ring.to_ordered_comm_semiring OrderedCommRing.toOrderedCommSemiring
end OrderedCommRing
section StrictOrderedSemiring
variable [StrictOrderedSemiring α] {a b c d : α}
-- see Note [lower instance priority]
instance (priority := 200) StrictOrderedSemiring.toPosMulStrictMono : PosMulStrictMono α :=
⟨fun x _ _ h => StrictOrderedSemiring.mul_lt_mul_of_pos_left _ _ _ h x.prop⟩
#align strict_ordered_semiring.to_pos_mul_strict_mono StrictOrderedSemiring.toPosMulStrictMono
-- see Note [lower instance priority]
instance (priority := 200) StrictOrderedSemiring.toMulPosStrictMono : MulPosStrictMono α :=
⟨fun x _ _ h => StrictOrderedSemiring.mul_lt_mul_of_pos_right _ _ _ h x.prop⟩
#align strict_ordered_semiring.to_mul_pos_strict_mono StrictOrderedSemiring.toMulPosStrictMono
-- See note [reducible non-instances]
/-- A choice-free version of `StrictOrderedSemiring.toOrderedSemiring` to avoid using choice in
basic `Nat` lemmas. -/
abbrev StrictOrderedSemiring.toOrderedSemiring' [@DecidableRel α (· ≤ ·)] : OrderedSemiring α :=
{ ‹StrictOrderedSemiring α› with
mul_le_mul_of_nonneg_left := fun a b c hab hc => by
obtain rfl | hab := Decidable.eq_or_lt_of_le hab
· rfl
obtain rfl | hc := Decidable.eq_or_lt_of_le hc
· simp
· exact (mul_lt_mul_of_pos_left hab hc).le,
mul_le_mul_of_nonneg_right := fun a b c hab hc => by
obtain rfl | hab := Decidable.eq_or_lt_of_le hab
· rfl
obtain rfl | hc := Decidable.eq_or_lt_of_le hc
· simp
· exact (mul_lt_mul_of_pos_right hab hc).le }
#align strict_ordered_semiring.to_ordered_semiring' StrictOrderedSemiring.toOrderedSemiring'
-- see Note [lower instance priority]
instance (priority := 100) StrictOrderedSemiring.toOrderedSemiring : OrderedSemiring α :=
{ ‹StrictOrderedSemiring α› with
mul_le_mul_of_nonneg_left := fun _ _ _ =>
letI := @StrictOrderedSemiring.toOrderedSemiring' α _ (Classical.decRel _)
mul_le_mul_of_nonneg_left,
mul_le_mul_of_nonneg_right := fun _ _ _ =>
letI := @StrictOrderedSemiring.toOrderedSemiring' α _ (Classical.decRel _)
mul_le_mul_of_nonneg_right }
#align strict_ordered_semiring.to_ordered_semiring StrictOrderedSemiring.toOrderedSemiring
-- see Note [lower instance priority]
instance (priority := 100) StrictOrderedSemiring.toCharZero [StrictOrderedSemiring α] :
CharZero α where
cast_injective :=
(strictMono_nat_of_lt_succ fun n ↦ by rw [Nat.cast_succ]; apply lt_add_one).injective
#align strict_ordered_semiring.to_char_zero StrictOrderedSemiring.toCharZero
theorem mul_lt_mul (hac : a < c) (hbd : b ≤ d) (hb : 0 < b) (hc : 0 ≤ c) : a * b < c * d :=
(mul_lt_mul_of_pos_right hac hb).trans_le <| mul_le_mul_of_nonneg_left hbd hc
#align mul_lt_mul mul_lt_mul
theorem mul_lt_mul' (hac : a ≤ c) (hbd : b < d) (hb : 0 ≤ b) (hc : 0 < c) : a * b < c * d :=
(mul_le_mul_of_nonneg_right hac hb).trans_lt <| mul_lt_mul_of_pos_left hbd hc
#align mul_lt_mul' mul_lt_mul'
@[simp]
theorem pow_pos (H : 0 < a) : ∀ n : ℕ, 0 < a ^ n
| 0 => by
nontriviality
rw [pow_zero]
exact zero_lt_one
| n + 1 => by
rw [pow_succ]
exact mul_pos (pow_pos H _) H
#align pow_pos pow_pos
theorem mul_self_lt_mul_self (h1 : 0 ≤ a) (h2 : a < b) : a * a < b * b :=
mul_lt_mul' h2.le h2 h1 <| h1.trans_lt h2
#align mul_self_lt_mul_self mul_self_lt_mul_self
-- In the next lemma, we used to write `Set.Ici 0` instead of `{x | 0 ≤ x}`.
-- As this lemma is not used outside this file,
-- and the import for `Set.Ici` is not otherwise needed until later,
-- we choose not to use it here.
theorem strictMonoOn_mul_self : StrictMonoOn (fun x : α => x * x) { x | 0 ≤ x } :=
fun _ hx _ _ hxy => mul_self_lt_mul_self hx hxy
#align strict_mono_on_mul_self strictMonoOn_mul_self
-- See Note [decidable namespace]
protected theorem Decidable.mul_lt_mul'' [@DecidableRel α (· ≤ ·)] (h1 : a < c) (h2 : b < d)
(h3 : 0 ≤ a) (h4 : 0 ≤ b) : a * b < c * d :=
h4.lt_or_eq_dec.elim (fun b0 => mul_lt_mul h1 h2.le b0 <| h3.trans h1.le) fun b0 => by
rw [← b0, mul_zero]; exact mul_pos (h3.trans_lt h1) (h4.trans_lt h2)
#align decidable.mul_lt_mul'' Decidable.mul_lt_mul''
@[gcongr]
theorem mul_lt_mul'' : a < c → b < d → 0 ≤ a → 0 ≤ b → a * b < c * d := by classical
exact Decidable.mul_lt_mul''
#align mul_lt_mul'' mul_lt_mul''
theorem lt_mul_left (hn : 0 < a) (hm : 1 < b) : a < b * a := by
convert mul_lt_mul_of_pos_right hm hn
rw [one_mul]
#align lt_mul_left lt_mul_left
theorem lt_mul_right (hn : 0 < a) (hm : 1 < b) : a < a * b := by
convert mul_lt_mul_of_pos_left hm hn
rw [mul_one]
#align lt_mul_right lt_mul_right
theorem lt_mul_self (hn : 1 < a) : a < a * a :=
lt_mul_left (hn.trans_le' zero_le_one) hn
#align lt_mul_self lt_mul_self
section Monotone
variable [Preorder β] {f g : β → α}
theorem strictMono_mul_left_of_pos (ha : 0 < a) : StrictMono fun x => a * x := fun _ _ b_lt_c =>
mul_lt_mul_of_pos_left b_lt_c ha
#align strict_mono_mul_left_of_pos strictMono_mul_left_of_pos
theorem strictMono_mul_right_of_pos (ha : 0 < a) : StrictMono fun x => x * a := fun _ _ b_lt_c =>
mul_lt_mul_of_pos_right b_lt_c ha
#align strict_mono_mul_right_of_pos strictMono_mul_right_of_pos
theorem StrictMono.mul_const (hf : StrictMono f) (ha : 0 < a) : StrictMono fun x => f x * a :=
(strictMono_mul_right_of_pos ha).comp hf
#align strict_mono.mul_const StrictMono.mul_const
theorem StrictMono.const_mul (hf : StrictMono f) (ha : 0 < a) : StrictMono fun x => a * f x :=
(strictMono_mul_left_of_pos ha).comp hf
#align strict_mono.const_mul StrictMono.const_mul
theorem StrictAnti.mul_const (hf : StrictAnti f) (ha : 0 < a) : StrictAnti fun x => f x * a :=
(strictMono_mul_right_of_pos ha).comp_strictAnti hf
#align strict_anti.mul_const StrictAnti.mul_const
theorem StrictAnti.const_mul (hf : StrictAnti f) (ha : 0 < a) : StrictAnti fun x => a * f x :=
(strictMono_mul_left_of_pos ha).comp_strictAnti hf
#align strict_anti.const_mul StrictAnti.const_mul
theorem StrictMono.mul_monotone (hf : StrictMono f) (hg : Monotone g) (hf₀ : ∀ x, 0 ≤ f x)
(hg₀ : ∀ x, 0 < g x) : StrictMono (f * g) := fun _ _ h =>
mul_lt_mul (hf h) (hg h.le) (hg₀ _) (hf₀ _)
#align strict_mono.mul_monotone StrictMono.mul_monotone
theorem Monotone.mul_strictMono (hf : Monotone f) (hg : StrictMono g) (hf₀ : ∀ x, 0 < f x)
(hg₀ : ∀ x, 0 ≤ g x) : StrictMono (f * g) := fun _ _ h =>
mul_lt_mul' (hf h.le) (hg h) (hg₀ _) (hf₀ _)
#align monotone.mul_strict_mono Monotone.mul_strictMono
theorem StrictMono.mul (hf : StrictMono f) (hg : StrictMono g) (hf₀ : ∀ x, 0 ≤ f x)
(hg₀ : ∀ x, 0 ≤ g x) : StrictMono (f * g) := fun _ _ h =>
mul_lt_mul'' (hf h) (hg h) (hf₀ _) (hg₀ _)
#align strict_mono.mul StrictMono.mul
end Monotone
theorem lt_two_mul_self (ha : 0 < a) : a < 2 * a :=
lt_mul_of_one_lt_left ha one_lt_two
#align lt_two_mul_self lt_two_mul_self
-- see Note [lower instance priority]
instance (priority := 100) StrictOrderedSemiring.toNoMaxOrder : NoMaxOrder α :=
⟨fun a => ⟨a + 1, lt_add_of_pos_right _ one_pos⟩⟩
#align strict_ordered_semiring.to_no_max_order StrictOrderedSemiring.toNoMaxOrder
variable [ExistsAddOfLE α]
theorem mul_lt_mul_of_neg_left (h : b < a) (hc : c < 0) : c * a < c * b := by
obtain ⟨d, hcd⟩ := exists_add_of_le hc.le
refine (add_lt_add_iff_right (d * b + d * a)).1 ?_
calc
_ = d * b := by rw [add_left_comm, ← add_mul, ← hcd, zero_mul, add_zero]
_ < d * a := mul_lt_mul_of_pos_left h <| hcd.trans_lt <| add_lt_of_neg_left _ hc
_ = _ := by rw [← add_assoc, ← add_mul, ← hcd, zero_mul, zero_add]
#align mul_lt_mul_of_neg_left mul_lt_mul_of_neg_left
theorem mul_lt_mul_of_neg_right (h : b < a) (hc : c < 0) : a * c < b * c := by
obtain ⟨d, hcd⟩ := exists_add_of_le hc.le
refine (add_lt_add_iff_right (b * d + a * d)).1 ?_
calc
_ = b * d := by rw [add_left_comm, ← mul_add, ← hcd, mul_zero, add_zero]
_ < a * d := mul_lt_mul_of_pos_right h <| hcd.trans_lt <| add_lt_of_neg_left _ hc
_ = _ := by rw [← add_assoc, ← mul_add, ← hcd, mul_zero, zero_add]
#align mul_lt_mul_of_neg_right mul_lt_mul_of_neg_right
theorem mul_pos_of_neg_of_neg {a b : α} (ha : a < 0) (hb : b < 0) : 0 < a * b := by
simpa only [zero_mul] using mul_lt_mul_of_neg_right ha hb
#align mul_pos_of_neg_of_neg mul_pos_of_neg_of_neg
/-- Variant of `mul_lt_of_lt_one_left` for `b` negative instead of positive. -/
theorem lt_mul_of_lt_one_left (hb : b < 0) (h : a < 1) : b < a * b := by
simpa only [one_mul] using mul_lt_mul_of_neg_right h hb
#align lt_mul_of_lt_one_left lt_mul_of_lt_one_left
/-- Variant of `lt_mul_of_one_lt_left` for `b` negative instead of positive. -/
theorem mul_lt_of_one_lt_left (hb : b < 0) (h : 1 < a) : a * b < b := by
simpa only [one_mul] using mul_lt_mul_of_neg_right h hb
#align mul_lt_of_one_lt_left mul_lt_of_one_lt_left
/-- Variant of `mul_lt_of_lt_one_right` for `a` negative instead of positive. -/
theorem lt_mul_of_lt_one_right (ha : a < 0) (h : b < 1) : a < a * b := by
simpa only [mul_one] using mul_lt_mul_of_neg_left h ha
#align lt_mul_of_lt_one_right lt_mul_of_lt_one_right
/-- Variant of `lt_mul_of_lt_one_right` for `a` negative instead of positive. -/
theorem mul_lt_of_one_lt_right (ha : a < 0) (h : 1 < b) : a * b < a := by
simpa only [mul_one] using mul_lt_mul_of_neg_left h ha
#align mul_lt_of_one_lt_right mul_lt_of_one_lt_right
section Monotone
variable [Preorder β] {f g : β → α}
theorem strictAnti_mul_left {a : α} (ha : a < 0) : StrictAnti (a * ·) := fun _ _ b_lt_c =>
mul_lt_mul_of_neg_left b_lt_c ha
#align strict_anti_mul_left strictAnti_mul_left
theorem strictAnti_mul_right {a : α} (ha : a < 0) : StrictAnti fun x => x * a := fun _ _ b_lt_c =>
mul_lt_mul_of_neg_right b_lt_c ha
#align strict_anti_mul_right strictAnti_mul_right
theorem StrictMono.const_mul_of_neg (hf : StrictMono f) (ha : a < 0) :
StrictAnti fun x => a * f x :=
(strictAnti_mul_left ha).comp_strictMono hf
#align strict_mono.const_mul_of_neg StrictMono.const_mul_of_neg
theorem StrictMono.mul_const_of_neg (hf : StrictMono f) (ha : a < 0) :
StrictAnti fun x => f x * a :=
(strictAnti_mul_right ha).comp_strictMono hf
#align strict_mono.mul_const_of_neg StrictMono.mul_const_of_neg
theorem StrictAnti.const_mul_of_neg (hf : StrictAnti f) (ha : a < 0) :
StrictMono fun x => a * f x :=
(strictAnti_mul_left ha).comp hf
#align strict_anti.const_mul_of_neg StrictAnti.const_mul_of_neg
theorem StrictAnti.mul_const_of_neg (hf : StrictAnti f) (ha : a < 0) :
StrictMono fun x => f x * a :=
(strictAnti_mul_right ha).comp hf
#align strict_anti.mul_const_of_neg StrictAnti.mul_const_of_neg
end Monotone
/-- Binary **rearrangement inequality**. -/
lemma mul_add_mul_le_mul_add_mul (hab : a ≤ b) (hcd : c ≤ d) : a * d + b * c ≤ a * c + b * d := by
obtain ⟨b, rfl⟩ := exists_add_of_le hab
obtain ⟨d, rfl⟩ := exists_add_of_le hcd
rw [mul_add, add_right_comm, mul_add, ← add_assoc]
exact add_le_add_left (mul_le_mul_of_nonneg_right hab <| (le_add_iff_nonneg_right _).1 hcd) _
#align mul_add_mul_le_mul_add_mul mul_add_mul_le_mul_add_mul
/-- Binary **rearrangement inequality**. -/
lemma mul_add_mul_le_mul_add_mul' (hba : b ≤ a) (hdc : d ≤ c) : a * d + b * c ≤ a * c + b * d := by
rw [add_comm (a * d), add_comm (a * c)]; exact mul_add_mul_le_mul_add_mul hba hdc
#align mul_add_mul_le_mul_add_mul' mul_add_mul_le_mul_add_mul'
/-- Binary strict **rearrangement inequality**. -/
lemma mul_add_mul_lt_mul_add_mul (hab : a < b) (hcd : c < d) : a * d + b * c < a * c + b * d := by
obtain ⟨b, rfl⟩ := exists_add_of_le hab.le
obtain ⟨d, rfl⟩ := exists_add_of_le hcd.le
rw [mul_add, add_right_comm, mul_add, ← add_assoc]
exact add_lt_add_left (mul_lt_mul_of_pos_right hab <| (lt_add_iff_pos_right _).1 hcd) _
#align mul_add_mul_lt_mul_add_mul mul_add_mul_lt_mul_add_mul
/-- Binary **rearrangement inequality**. -/
lemma mul_add_mul_lt_mul_add_mul' (hba : b < a) (hdc : d < c) : a * d + b * c < a * c + b * d := by
rw [add_comm (a * d), add_comm (a * c)]
exact mul_add_mul_lt_mul_add_mul hba hdc
#align mul_add_mul_lt_mul_add_mul' mul_add_mul_lt_mul_add_mul'
end StrictOrderedSemiring
section StrictOrderedCommSemiring
variable [StrictOrderedCommSemiring α]
-- See note [reducible non-instances]
/-- A choice-free version of `StrictOrderedCommSemiring.toOrderedCommSemiring'` to avoid using
choice in basic `Nat` lemmas. -/
abbrev StrictOrderedCommSemiring.toOrderedCommSemiring' [@DecidableRel α (· ≤ ·)] :
OrderedCommSemiring α :=
{ ‹StrictOrderedCommSemiring α›, StrictOrderedSemiring.toOrderedSemiring' with }
#align strict_ordered_comm_semiring.to_ordered_comm_semiring' StrictOrderedCommSemiring.toOrderedCommSemiring'
-- see Note [lower instance priority]
instance (priority := 100) StrictOrderedCommSemiring.toOrderedCommSemiring :
OrderedCommSemiring α :=
{ ‹StrictOrderedCommSemiring α›, StrictOrderedSemiring.toOrderedSemiring with }
#align strict_ordered_comm_semiring.to_ordered_comm_semiring StrictOrderedCommSemiring.toOrderedCommSemiring
end StrictOrderedCommSemiring
section StrictOrderedRing
variable [StrictOrderedRing α] {a b c : α}
-- see Note [lower instance priority]
instance (priority := 100) StrictOrderedRing.toStrictOrderedSemiring : StrictOrderedSemiring α :=
{ ‹StrictOrderedRing α›, (Ring.toSemiring : Semiring α) with
le_of_add_le_add_left := @le_of_add_le_add_left α _ _ _,
mul_lt_mul_of_pos_left := fun a b c h hc => by
simpa only [mul_sub, sub_pos] using StrictOrderedRing.mul_pos _ _ hc (sub_pos.2 h),
mul_lt_mul_of_pos_right := fun a b c h hc => by
simpa only [sub_mul, sub_pos] using StrictOrderedRing.mul_pos _ _ (sub_pos.2 h) hc }
#align strict_ordered_ring.to_strict_ordered_semiring StrictOrderedRing.toStrictOrderedSemiring
-- See note [reducible non-instances]
/-- A choice-free version of `StrictOrderedRing.toOrderedRing` to avoid using choice in basic
`Int` lemmas. -/
abbrev StrictOrderedRing.toOrderedRing' [@DecidableRel α (· ≤ ·)] : OrderedRing α :=
{ ‹StrictOrderedRing α›, (Ring.toSemiring : Semiring α) with
mul_nonneg := fun a b ha hb => by
obtain ha | ha := Decidable.eq_or_lt_of_le ha
· rw [← ha, zero_mul]
obtain hb | hb := Decidable.eq_or_lt_of_le hb
· rw [← hb, mul_zero]
· exact (StrictOrderedRing.mul_pos _ _ ha hb).le }
#align strict_ordered_ring.to_ordered_ring' StrictOrderedRing.toOrderedRing'
-- see Note [lower instance priority]
instance (priority := 100) StrictOrderedRing.toOrderedRing : OrderedRing α where
__ := ‹StrictOrderedRing α›
mul_nonneg := fun _ _ => mul_nonneg
#align strict_ordered_ring.to_ordered_ring StrictOrderedRing.toOrderedRing
end StrictOrderedRing
section StrictOrderedCommRing
variable [StrictOrderedCommRing α]
-- See note [reducible non-instances]
/-- A choice-free version of `StrictOrderedCommRing.toOrderedCommRing` to avoid using
choice in basic `Int` lemmas. -/
abbrev StrictOrderedCommRing.toOrderedCommRing' [@DecidableRel α (· ≤ ·)] : OrderedCommRing α :=
{ ‹StrictOrderedCommRing α›, StrictOrderedRing.toOrderedRing' with }
#align strict_ordered_comm_ring.to_ordered_comm_ring' StrictOrderedCommRing.toOrderedCommRing'
-- See note [lower instance priority]
instance (priority := 100) StrictOrderedCommRing.toStrictOrderedCommSemiring :
StrictOrderedCommSemiring α :=
{ ‹StrictOrderedCommRing α›, StrictOrderedRing.toStrictOrderedSemiring with }
#align strict_ordered_comm_ring.to_strict_ordered_comm_semiring StrictOrderedCommRing.toStrictOrderedCommSemiring
-- See note [lower instance priority]
instance (priority := 100) StrictOrderedCommRing.toOrderedCommRing : OrderedCommRing α :=
{ ‹StrictOrderedCommRing α›, StrictOrderedRing.toOrderedRing with }
#align strict_ordered_comm_ring.to_ordered_comm_ring StrictOrderedCommRing.toOrderedCommRing
end StrictOrderedCommRing
section LinearOrderedSemiring
variable [LinearOrderedSemiring α] {a b c d : α}
-- see Note [lower instance priority]
instance (priority := 200) LinearOrderedSemiring.toPosMulReflectLT : PosMulReflectLT α :=
⟨fun a _ _ => (monotone_mul_left_of_nonneg a.2).reflect_lt⟩
#align linear_ordered_semiring.to_pos_mul_reflect_lt LinearOrderedSemiring.toPosMulReflectLT
-- see Note [lower instance priority]
instance (priority := 200) LinearOrderedSemiring.toMulPosReflectLT : MulPosReflectLT α :=
⟨fun a _ _ => (monotone_mul_right_of_nonneg a.2).reflect_lt⟩
#align linear_ordered_semiring.to_mul_pos_reflect_lt LinearOrderedSemiring.toMulPosReflectLT
attribute [local instance] LinearOrderedSemiring.decidableLE LinearOrderedSemiring.decidableLT
theorem nonneg_and_nonneg_or_nonpos_and_nonpos_of_mul_nonneg (hab : 0 ≤ a * b) :
0 ≤ a ∧ 0 ≤ b ∨ a ≤ 0 ∧ b ≤ 0 := by
refine Decidable.or_iff_not_and_not.2 ?_
simp only [not_and, not_le]; intro ab nab; apply not_lt_of_le hab _
rcases lt_trichotomy 0 a with (ha | rfl | ha)
· exact mul_neg_of_pos_of_neg ha (ab ha.le)
· exact ((ab le_rfl).asymm (nab le_rfl)).elim
· exact mul_neg_of_neg_of_pos ha (nab ha.le)
#align nonneg_and_nonneg_or_nonpos_and_nonpos_of_mul_nnonneg nonneg_and_nonneg_or_nonpos_and_nonpos_of_mul_nonneg
theorem nonneg_of_mul_nonneg_left (h : 0 ≤ a * b) (hb : 0 < b) : 0 ≤ a :=
le_of_not_gt fun ha => (mul_neg_of_neg_of_pos ha hb).not_le h
#align nonneg_of_mul_nonneg_left nonneg_of_mul_nonneg_left
theorem nonneg_of_mul_nonneg_right (h : 0 ≤ a * b) (ha : 0 < a) : 0 ≤ b :=
le_of_not_gt fun hb => (mul_neg_of_pos_of_neg ha hb).not_le h
#align nonneg_of_mul_nonneg_right nonneg_of_mul_nonneg_right
theorem neg_of_mul_neg_left (h : a * b < 0) (hb : 0 ≤ b) : a < 0 :=
lt_of_not_ge fun ha => (mul_nonneg ha hb).not_lt h
#align neg_of_mul_neg_left neg_of_mul_neg_left
theorem neg_of_mul_neg_right (h : a * b < 0) (ha : 0 ≤ a) : b < 0 :=
lt_of_not_ge fun hb => (mul_nonneg ha hb).not_lt h
#align neg_of_mul_neg_right neg_of_mul_neg_right
theorem nonpos_of_mul_nonpos_left (h : a * b ≤ 0) (hb : 0 < b) : a ≤ 0 :=
le_of_not_gt fun ha : a > 0 => (mul_pos ha hb).not_le h
#align nonpos_of_mul_nonpos_left nonpos_of_mul_nonpos_left
theorem nonpos_of_mul_nonpos_right (h : a * b ≤ 0) (ha : 0 < a) : b ≤ 0 :=
le_of_not_gt fun hb : b > 0 => (mul_pos ha hb).not_le h
#align nonpos_of_mul_nonpos_right nonpos_of_mul_nonpos_right
@[simp]
theorem mul_nonneg_iff_of_pos_left (h : 0 < c) : 0 ≤ c * b ↔ 0 ≤ b := by
convert mul_le_mul_left h
simp
#align zero_le_mul_left mul_nonneg_iff_of_pos_left
@[simp]
theorem mul_nonneg_iff_of_pos_right (h : 0 < c) : 0 ≤ b * c ↔ 0 ≤ b := by
simpa using (mul_le_mul_right h : 0 * c ≤ b * c ↔ 0 ≤ b)
#align zero_le_mul_right mul_nonneg_iff_of_pos_right
-- Porting note: we used to not need the type annotation on `(0 : α)` at the start of the `calc`.
theorem add_le_mul_of_left_le_right (a2 : 2 ≤ a) (ab : a ≤ b) : a + b ≤ a * b :=
have : 0 < b :=
calc (0 : α)
_ < 2 := zero_lt_two
_ ≤ a := a2
_ ≤ b := ab
calc
a + b ≤ b + b := add_le_add_right ab b
_ = 2 * b := (two_mul b).symm
_ ≤ a * b := (mul_le_mul_right this).mpr a2
#align add_le_mul_of_left_le_right add_le_mul_of_left_le_right
-- Porting note: we used to not need the type annotation on `(0 : α)` at the start of the `calc`.
theorem add_le_mul_of_right_le_left (b2 : 2 ≤ b) (ba : b ≤ a) : a + b ≤ a * b :=
have : 0 < a :=
calc (0 : α)
_ < 2 := zero_lt_two
_ ≤ b := b2
_ ≤ a := ba
calc
a + b ≤ a + a := add_le_add_left ba a
_ = a * 2 := (mul_two a).symm
_ ≤ a * b := (mul_le_mul_left this).mpr b2
#align add_le_mul_of_right_le_left add_le_mul_of_right_le_left
theorem add_le_mul (a2 : 2 ≤ a) (b2 : 2 ≤ b) : a + b ≤ a * b :=
if hab : a ≤ b then add_le_mul_of_left_le_right a2 hab
else add_le_mul_of_right_le_left b2 (le_of_not_le hab)
#align add_le_mul add_le_mul
theorem add_le_mul' (a2 : 2 ≤ a) (b2 : 2 ≤ b) : a + b ≤ b * a :=
(le_of_eq (add_comm _ _)).trans (add_le_mul b2 a2)
#align add_le_mul' add_le_mul'
set_option linter.deprecated false in
section
@[simp]
theorem bit0_le_bit0 : bit0 a ≤ bit0 b ↔ a ≤ b := by
rw [bit0, bit0, ← two_mul, ← two_mul, mul_le_mul_left (zero_lt_two : 0 < (2 : α))]
#align bit0_le_bit0 bit0_le_bit0
@[simp]
theorem bit0_lt_bit0 : bit0 a < bit0 b ↔ a < b := by
rw [bit0, bit0, ← two_mul, ← two_mul, mul_lt_mul_left (zero_lt_two : 0 < (2 : α))]
#align bit0_lt_bit0 bit0_lt_bit0
@[simp]
theorem bit1_le_bit1 : bit1 a ≤ bit1 b ↔ a ≤ b :=
(add_le_add_iff_right 1).trans bit0_le_bit0
#align bit1_le_bit1 bit1_le_bit1
@[simp]
theorem bit1_lt_bit1 : bit1 a < bit1 b ↔ a < b :=
(add_lt_add_iff_right 1).trans bit0_lt_bit0
#align bit1_lt_bit1 bit1_lt_bit1
@[simp]
theorem one_le_bit1 : (1 : α) ≤ bit1 a ↔ 0 ≤ a := by
rw [bit1, le_add_iff_nonneg_left, bit0, ← two_mul, mul_nonneg_iff_of_pos_left (zero_lt_two' α)]
#align one_le_bit1 one_le_bit1
@[simp]
theorem one_lt_bit1 : (1 : α) < bit1 a ↔ 0 < a := by
rw [bit1, lt_add_iff_pos_left, bit0, ← two_mul, mul_pos_iff_of_pos_left (zero_lt_two' α)]
#align one_lt_bit1 one_lt_bit1
@[simp]
theorem zero_le_bit0 : (0 : α) ≤ bit0 a ↔ 0 ≤ a := by
rw [bit0, ← two_mul, mul_nonneg_iff_of_pos_left (zero_lt_two : 0 < (2 : α))]
#align zero_le_bit0 zero_le_bit0
@[simp]
theorem zero_lt_bit0 : (0 : α) < bit0 a ↔ 0 < a := by
rw [bit0, ← two_mul, mul_pos_iff_of_pos_left (zero_lt_two : 0 < (2 : α))]
#align zero_lt_bit0 zero_lt_bit0
end
theorem mul_nonneg_iff_right_nonneg_of_pos (ha : 0 < a) : 0 ≤ a * b ↔ 0 ≤ b :=
⟨fun h => nonneg_of_mul_nonneg_right h ha, mul_nonneg ha.le⟩
#align mul_nonneg_iff_right_nonneg_of_pos mul_nonneg_iff_right_nonneg_of_pos
theorem mul_nonneg_iff_left_nonneg_of_pos (hb : 0 < b) : 0 ≤ a * b ↔ 0 ≤ a :=
⟨fun h => nonneg_of_mul_nonneg_left h hb, fun h => mul_nonneg h hb.le⟩
#align mul_nonneg_iff_left_nonneg_of_pos mul_nonneg_iff_left_nonneg_of_pos
theorem nonpos_of_mul_nonneg_left (h : 0 ≤ a * b) (hb : b < 0) : a ≤ 0 :=
le_of_not_gt fun ha => absurd h (mul_neg_of_pos_of_neg ha hb).not_le
#align nonpos_of_mul_nonneg_left nonpos_of_mul_nonneg_left
theorem nonpos_of_mul_nonneg_right (h : 0 ≤ a * b) (ha : a < 0) : b ≤ 0 :=
le_of_not_gt fun hb => absurd h (mul_neg_of_neg_of_pos ha hb).not_le
#align nonpos_of_mul_nonneg_right nonpos_of_mul_nonneg_right
@[simp]
theorem Units.inv_pos {u : αˣ} : (0 : α) < ↑u⁻¹ ↔ (0 : α) < u :=
have : ∀ {u : αˣ}, (0 : α) < u → (0 : α) < ↑u⁻¹ := @fun u h =>
(mul_pos_iff_of_pos_left h).mp <| u.mul_inv.symm ▸ zero_lt_one
⟨this, this⟩
#align units.inv_pos Units.inv_pos
@[simp]
theorem Units.inv_neg {u : αˣ} : ↑u⁻¹ < (0 : α) ↔ ↑u < (0 : α) :=
have : ∀ {u : αˣ}, ↑u < (0 : α) → ↑u⁻¹ < (0 : α) := @fun u h =>
neg_of_mul_pos_right (u.mul_inv.symm ▸ zero_lt_one) h.le
⟨this, this⟩
#align units.inv_neg Units.inv_neg
theorem cmp_mul_pos_left (ha : 0 < a) (b c : α) : cmp (a * b) (a * c) = cmp b c :=
(strictMono_mul_left_of_pos ha).cmp_map_eq b c
#align cmp_mul_pos_left cmp_mul_pos_left
theorem cmp_mul_pos_right (ha : 0 < a) (b c : α) : cmp (b * a) (c * a) = cmp b c :=
(strictMono_mul_right_of_pos ha).cmp_map_eq b c
#align cmp_mul_pos_right cmp_mul_pos_right
theorem mul_max_of_nonneg (b c : α) (ha : 0 ≤ a) : a * max b c = max (a * b) (a * c) :=
(monotone_mul_left_of_nonneg ha).map_max
#align mul_max_of_nonneg mul_max_of_nonneg
theorem mul_min_of_nonneg (b c : α) (ha : 0 ≤ a) : a * min b c = min (a * b) (a * c) :=
(monotone_mul_left_of_nonneg ha).map_min
#align mul_min_of_nonneg mul_min_of_nonneg
theorem max_mul_of_nonneg (a b : α) (hc : 0 ≤ c) : max a b * c = max (a * c) (b * c) :=
(monotone_mul_right_of_nonneg hc).map_max
#align max_mul_of_nonneg max_mul_of_nonneg
theorem min_mul_of_nonneg (a b : α) (hc : 0 ≤ c) : min a b * c = min (a * c) (b * c) :=
(monotone_mul_right_of_nonneg hc).map_min
#align min_mul_of_nonneg min_mul_of_nonneg
theorem le_of_mul_le_of_one_le {a b c : α} (h : a * c ≤ b) (hb : 0 ≤ b) (hc : 1 ≤ c) : a ≤ b :=
le_of_mul_le_mul_right (h.trans <| le_mul_of_one_le_right hb hc) <| zero_lt_one.trans_le hc
#align le_of_mul_le_of_one_le le_of_mul_le_of_one_le
theorem nonneg_le_nonneg_of_sq_le_sq {a b : α} (hb : 0 ≤ b) (h : a * a ≤ b * b) : a ≤ b :=
le_of_not_gt fun hab => (mul_self_lt_mul_self hb hab).not_le h
#align nonneg_le_nonneg_of_sq_le_sq nonneg_le_nonneg_of_sq_le_sq
theorem mul_self_le_mul_self_iff {a b : α} (h1 : 0 ≤ a) (h2 : 0 ≤ b) : a ≤ b ↔ a * a ≤ b * b :=
⟨mul_self_le_mul_self h1, nonneg_le_nonneg_of_sq_le_sq h2⟩
#align mul_self_le_mul_self_iff mul_self_le_mul_self_iff
theorem mul_self_lt_mul_self_iff {a b : α} (h1 : 0 ≤ a) (h2 : 0 ≤ b) : a < b ↔ a * a < b * b :=
((@strictMonoOn_mul_self α _).lt_iff_lt h1 h2).symm
#align mul_self_lt_mul_self_iff mul_self_lt_mul_self_iff
theorem mul_self_inj {a b : α} (h1 : 0 ≤ a) (h2 : 0 ≤ b) : a * a = b * b ↔ a = b :=
(@strictMonoOn_mul_self α _).eq_iff_eq h1 h2
#align mul_self_inj mul_self_inj
lemma sign_cases_of_C_mul_pow_nonneg (h : ∀ n, 0 ≤ a * b ^ n) : a = 0 ∨ 0 < a ∧ 0 ≤ b := by
have : 0 ≤ a := by simpa only [pow_zero, mul_one] using h 0
refine this.eq_or_gt.imp_right fun ha ↦ ⟨ha, nonneg_of_mul_nonneg_right ?_ ha⟩
simpa only [pow_one] using h 1
set_option linter.uppercaseLean3 false in
#align sign_cases_of_C_mul_pow_nonneg sign_cases_of_C_mul_pow_nonneg
variable [ExistsAddOfLE α]
-- See note [lower instance priority]
instance (priority := 100) LinearOrderedSemiring.noZeroDivisors : NoZeroDivisors α where
eq_zero_or_eq_zero_of_mul_eq_zero {a b} hab := by
contrapose! hab
obtain ha | ha := hab.1.lt_or_lt <;> obtain hb | hb := hab.2.lt_or_lt
exacts [(mul_pos_of_neg_of_neg ha hb).ne', (mul_neg_of_neg_of_pos ha hb).ne,
(mul_neg_of_pos_of_neg ha hb).ne, (mul_pos ha hb).ne']
#align linear_ordered_ring.no_zero_divisors LinearOrderedSemiring.noZeroDivisors
-- Note that we can't use `NoZeroDivisors.to_isDomain` since we are merely in a semiring.
-- See note [lower instance priority]
instance (priority := 100) LinearOrderedRing.isDomain : IsDomain α where
mul_left_cancel_of_ne_zero {a b c} ha h := by
obtain ha | ha := ha.lt_or_lt
exacts [(strictAnti_mul_left ha).injective h, (strictMono_mul_left_of_pos ha).injective h]
mul_right_cancel_of_ne_zero {b a c} ha h := by
obtain ha | ha := ha.lt_or_lt
exacts [(strictAnti_mul_right ha).injective h, (strictMono_mul_right_of_pos ha).injective h]
#align linear_ordered_ring.is_domain LinearOrderedRing.isDomain
theorem mul_pos_iff : 0 < a * b ↔ 0 < a ∧ 0 < b ∨ a < 0 ∧ b < 0 :=
⟨pos_and_pos_or_neg_and_neg_of_mul_pos, fun h =>
h.elim (and_imp.2 mul_pos) (and_imp.2 mul_pos_of_neg_of_neg)⟩
#align mul_pos_iff mul_pos_iff
theorem mul_nonneg_iff : 0 ≤ a * b ↔ 0 ≤ a ∧ 0 ≤ b ∨ a ≤ 0 ∧ b ≤ 0 :=
⟨nonneg_and_nonneg_or_nonpos_and_nonpos_of_mul_nonneg, fun h =>
h.elim (and_imp.2 mul_nonneg) (and_imp.2 mul_nonneg_of_nonpos_of_nonpos)⟩
#align mul_nonneg_iff mul_nonneg_iff
/-- Out of three elements of a `LinearOrderedRing`, two must have the same sign. -/
| Mathlib/Algebra/Order/Ring/Defs.lean | 1,106 | 1,128 | theorem mul_nonneg_of_three (a b c : α) : 0 ≤ a * b ∨ 0 ≤ b * c ∨ 0 ≤ c * a := by |
iterate 3 rw [mul_nonneg_iff]
have or_a := le_total 0 a
have or_b := le_total 0 b
have or_c := le_total 0 c
-- Porting note used to be by `itauto` from here
exact Or.elim or_c
(fun (h0 : 0 ≤ c) =>
Or.elim or_b
(fun (h1 : 0 ≤ b) =>
Or.elim or_a (fun (h2 : 0 ≤ a) => Or.inl (Or.inl ⟨h2, h1⟩))
(fun (_ : a ≤ 0) => Or.inr (Or.inl (Or.inl ⟨h1, h0⟩))))
(fun (h1 : b ≤ 0) =>
Or.elim or_a (fun (h3 : 0 ≤ a) => Or.inr (Or.inr (Or.inl ⟨h0, h3⟩)))
(fun (h3 : a ≤ 0) => Or.inl (Or.inr ⟨h3, h1⟩))))
(fun (h0 : c ≤ 0) =>
Or.elim or_b
(fun (h4 : 0 ≤ b) =>
Or.elim or_a (fun (h5 : 0 ≤ a) => Or.inl (Or.inl ⟨h5, h4⟩))
(fun (h5 : a ≤ 0) => Or.inr (Or.inr (Or.inr ⟨h0, h5⟩))))
(fun (h4 : b ≤ 0) =>
Or.elim or_a (fun (_ : 0 ≤ a) => Or.inr (Or.inl (Or.inr ⟨h4, h0⟩)))
(fun (h6 : a ≤ 0) => Or.inl (Or.inr ⟨h6, h4⟩))))
|
/-
Copyright (c) 2020 Johan Commelin. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johan Commelin
-/
import Mathlib.Analysis.SpecialFunctions.Complex.Log
import Mathlib.RingTheory.RootsOfUnity.Basic
#align_import ring_theory.roots_of_unity.complex from "leanprover-community/mathlib"@"7fdeecc0d03cd40f7a165e6cf00a4d2286db599f"
/-!
# Complex roots of unity
In this file we show that the `n`-th complex roots of unity
are exactly the complex numbers `exp (2 * π * I * (i / n))` for `i ∈ Finset.range n`.
## Main declarations
* `Complex.mem_rootsOfUnity`: the complex `n`-th roots of unity are exactly the
complex numbers of the form `exp (2 * π * I * (i / n))` for some `i < n`.
* `Complex.card_rootsOfUnity`: the number of `n`-th roots of unity is exactly `n`.
* `Complex.norm_rootOfUnity_eq_one`: A complex root of unity has norm `1`.
-/
namespace Complex
open Polynomial Real
open scoped Nat Real
theorem isPrimitiveRoot_exp_of_coprime (i n : ℕ) (h0 : n ≠ 0) (hi : i.Coprime n) :
IsPrimitiveRoot (exp (2 * π * I * (i / n))) n := by
rw [IsPrimitiveRoot.iff_def]
simp only [← exp_nat_mul, exp_eq_one_iff]
have hn0 : (n : ℂ) ≠ 0 := mod_cast h0
constructor
· use i
field_simp [hn0, mul_comm (i : ℂ), mul_comm (n : ℂ)]
· simp only [hn0, mul_right_comm _ _ ↑n, mul_left_inj' two_pi_I_ne_zero, Ne, not_false_iff,
mul_comm _ (i : ℂ), ← mul_assoc _ (i : ℂ), exists_imp, field_simps]
norm_cast
rintro l k hk
conv_rhs at hk => rw [mul_comm, ← mul_assoc]
have hz : 2 * ↑π * I ≠ 0 := by simp [pi_pos.ne.symm, I_ne_zero]
field_simp [hz] at hk
norm_cast at hk
have : n ∣ i * l := by rw [← Int.natCast_dvd_natCast, hk, mul_comm]; apply dvd_mul_left
exact hi.symm.dvd_of_dvd_mul_left this
#align complex.is_primitive_root_exp_of_coprime Complex.isPrimitiveRoot_exp_of_coprime
theorem isPrimitiveRoot_exp (n : ℕ) (h0 : n ≠ 0) : IsPrimitiveRoot (exp (2 * π * I / n)) n := by
simpa only [Nat.cast_one, one_div] using
isPrimitiveRoot_exp_of_coprime 1 n h0 n.coprime_one_left
#align complex.is_primitive_root_exp Complex.isPrimitiveRoot_exp
| Mathlib/RingTheory/RootsOfUnity/Complex.lean | 58 | 69 | theorem isPrimitiveRoot_iff (ζ : ℂ) (n : ℕ) (hn : n ≠ 0) :
IsPrimitiveRoot ζ n ↔ ∃ i < (n : ℕ), ∃ _ : i.Coprime n, exp (2 * π * I * (i / n)) = ζ := by |
have hn0 : (n : ℂ) ≠ 0 := mod_cast hn
constructor; swap
· rintro ⟨i, -, hi, rfl⟩; exact isPrimitiveRoot_exp_of_coprime i n hn hi
intro h
obtain ⟨i, hi, rfl⟩ :=
(isPrimitiveRoot_exp n hn).eq_pow_of_pow_eq_one h.pow_eq_one (Nat.pos_of_ne_zero hn)
refine ⟨i, hi, ((isPrimitiveRoot_exp n hn).pow_iff_coprime (Nat.pos_of_ne_zero hn) i).mp h, ?_⟩
rw [← exp_nat_mul]
congr 1
field_simp [hn0, mul_comm (i : ℂ)]
|
/-
Copyright (c) 2016 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad, Mario Carneiro
-/
import Mathlib.Algebra.Order.Ring.Int
#align_import data.int.least_greatest from "leanprover-community/mathlib"@"3342d1b2178381196f818146ff79bc0e7ccd9e2d"
/-! # Least upper bound and greatest lower bound properties for integers
In this file we prove that a bounded above nonempty set of integers has the greatest element, and a
counterpart of this statement for the least element.
## Main definitions
* `Int.leastOfBdd`: if `P : ℤ → Prop` is a decidable predicate, `b` is a lower bound of the set
`{m | P m}`, and there exists `m : ℤ` such that `P m` (this time, no witness is required), then
`Int.leastOfBdd` returns the least number `m` such that `P m`, together with proofs of `P m` and
of the minimality. This definition is computable and does not rely on the axiom of choice.
* `Int.greatestOfBdd`: a similar definition with all inequalities reversed.
## Main statements
* `Int.exists_least_of_bdd`: if `P : ℤ → Prop` is a predicate such that the set `{m : P m}` is
bounded below and nonempty, then this set has the least element. This lemma uses classical logic
to avoid assumption `[DecidablePred P]`. See `Int.leastOfBdd` for a constructive counterpart.
* `Int.coe_leastOfBdd_eq`: `(Int.leastOfBdd b Hb Hinh : ℤ)` does not depend on `b`.
* `Int.exists_greatest_of_bdd`, `Int.coe_greatest_of_bdd_eq`: versions of the above lemmas with all
inequalities reversed.
## Tags
integer numbers, least element, greatest element
-/
namespace Int
/-- A computable version of `exists_least_of_bdd`: given a decidable predicate on the
integers, with an explicit lower bound and a proof that it is somewhere true, return
the least value for which the predicate is true. -/
def leastOfBdd {P : ℤ → Prop} [DecidablePred P] (b : ℤ) (Hb : ∀ z : ℤ, P z → b ≤ z)
(Hinh : ∃ z : ℤ, P z) : { lb : ℤ // P lb ∧ ∀ z : ℤ, P z → lb ≤ z } :=
have EX : ∃ n : ℕ, P (b + n) :=
let ⟨elt, Helt⟩ := Hinh
match elt, le.dest (Hb _ Helt), Helt with
| _, ⟨n, rfl⟩, Hn => ⟨n, Hn⟩
⟨b + (Nat.find EX : ℤ), Nat.find_spec EX, fun z h =>
match z, le.dest (Hb _ h), h with
| _, ⟨_, rfl⟩, h => add_le_add_left (Int.ofNat_le.2 <| Nat.find_min' _ h) _⟩
#align int.least_of_bdd Int.leastOfBdd
/--
If `P : ℤ → Prop` is a predicate such that the set `{m : P m}` is bounded below and nonempty,
then this set has the least element. This lemma uses classical logic to avoid assumption
`[DecidablePred P]`. See `Int.leastOfBdd` for a constructive counterpart. -/
theorem exists_least_of_bdd
{P : ℤ → Prop}
(Hbdd : ∃ b : ℤ , ∀ z : ℤ , P z → b ≤ z)
(Hinh : ∃ z : ℤ , P z) : ∃ lb : ℤ , P lb ∧ ∀ z : ℤ , P z → lb ≤ z := by
classical
let ⟨b , Hb⟩ := Hbdd
let ⟨lb , H⟩ := leastOfBdd b Hb Hinh
exact ⟨lb , H⟩
#align int.exists_least_of_bdd Int.exists_least_of_bdd
| Mathlib/Data/Int/LeastGreatest.lean | 71 | 76 | theorem coe_leastOfBdd_eq {P : ℤ → Prop} [DecidablePred P] {b b' : ℤ} (Hb : ∀ z : ℤ, P z → b ≤ z)
(Hb' : ∀ z : ℤ, P z → b' ≤ z) (Hinh : ∃ z : ℤ, P z) :
(leastOfBdd b Hb Hinh : ℤ) = leastOfBdd b' Hb' Hinh := by |
rcases leastOfBdd b Hb Hinh with ⟨n, hn, h2n⟩
rcases leastOfBdd b' Hb' Hinh with ⟨n', hn', h2n'⟩
exact le_antisymm (h2n _ hn') (h2n' _ hn)
|
/-
Copyright (c) 2019 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes
-/
import Mathlib.NumberTheory.Zsqrtd.Basic
import Mathlib.RingTheory.PrincipalIdealDomain
import Mathlib.Data.Complex.Basic
import Mathlib.Data.Real.Archimedean
#align_import number_theory.zsqrtd.gaussian_int from "leanprover-community/mathlib"@"5b2fe80501ff327b9109fb09b7cc8c325cd0d7d9"
/-!
# Gaussian integers
The Gaussian integers are complex integer, complex numbers whose real and imaginary parts are both
integers.
## Main definitions
The Euclidean domain structure on `ℤ[i]` is defined in this file.
The homomorphism `GaussianInt.toComplex` into the complex numbers is also defined in this file.
## See also
See `NumberTheory.Zsqrtd.QuadraticReciprocity` for:
* `prime_iff_mod_four_eq_three_of_nat_prime`:
A prime natural number is prime in `ℤ[i]` if and only if it is `3` mod `4`
## Notations
This file uses the local notation `ℤ[i]` for `GaussianInt`
## Implementation notes
Gaussian integers are implemented using the more general definition `Zsqrtd`, the type of integers
adjoined a square root of `d`, in this case `-1`. The definition is reducible, so that properties
and definitions about `Zsqrtd` can easily be used.
-/
open Zsqrtd Complex
open scoped ComplexConjugate
/-- The Gaussian integers, defined as `ℤ√(-1)`. -/
abbrev GaussianInt : Type :=
Zsqrtd (-1)
#align gaussian_int GaussianInt
local notation "ℤ[i]" => GaussianInt
namespace GaussianInt
instance : Repr ℤ[i] :=
⟨fun x _ => "⟨" ++ repr x.re ++ ", " ++ repr x.im ++ "⟩"⟩
instance instCommRing : CommRing ℤ[i] :=
Zsqrtd.commRing
#align gaussian_int.comm_ring GaussianInt.instCommRing
section
attribute [-instance] Complex.instField -- Avoid making things noncomputable unnecessarily.
/-- The embedding of the Gaussian integers into the complex numbers, as a ring homomorphism. -/
def toComplex : ℤ[i] →+* ℂ :=
Zsqrtd.lift ⟨I, by simp⟩
#align gaussian_int.to_complex GaussianInt.toComplex
end
instance : Coe ℤ[i] ℂ :=
⟨toComplex⟩
theorem toComplex_def (x : ℤ[i]) : (x : ℂ) = x.re + x.im * I :=
rfl
#align gaussian_int.to_complex_def GaussianInt.toComplex_def
theorem toComplex_def' (x y : ℤ) : ((⟨x, y⟩ : ℤ[i]) : ℂ) = x + y * I := by simp [toComplex_def]
#align gaussian_int.to_complex_def' GaussianInt.toComplex_def'
theorem toComplex_def₂ (x : ℤ[i]) : (x : ℂ) = ⟨x.re, x.im⟩ := by
apply Complex.ext <;> simp [toComplex_def]
#align gaussian_int.to_complex_def₂ GaussianInt.toComplex_def₂
@[simp]
theorem to_real_re (x : ℤ[i]) : ((x.re : ℤ) : ℝ) = (x : ℂ).re := by simp [toComplex_def]
#align gaussian_int.to_real_re GaussianInt.to_real_re
@[simp]
theorem to_real_im (x : ℤ[i]) : ((x.im : ℤ) : ℝ) = (x : ℂ).im := by simp [toComplex_def]
#align gaussian_int.to_real_im GaussianInt.to_real_im
@[simp]
theorem toComplex_re (x y : ℤ) : ((⟨x, y⟩ : ℤ[i]) : ℂ).re = x := by simp [toComplex_def]
#align gaussian_int.to_complex_re GaussianInt.toComplex_re
@[simp]
theorem toComplex_im (x y : ℤ) : ((⟨x, y⟩ : ℤ[i]) : ℂ).im = y := by simp [toComplex_def]
#align gaussian_int.to_complex_im GaussianInt.toComplex_im
-- Porting note (#10618): @[simp] can prove this
theorem toComplex_add (x y : ℤ[i]) : ((x + y : ℤ[i]) : ℂ) = x + y :=
toComplex.map_add _ _
#align gaussian_int.to_complex_add GaussianInt.toComplex_add
-- Porting note (#10618): @[simp] can prove this
theorem toComplex_mul (x y : ℤ[i]) : ((x * y : ℤ[i]) : ℂ) = x * y :=
toComplex.map_mul _ _
#align gaussian_int.to_complex_mul GaussianInt.toComplex_mul
-- Porting note (#10618): @[simp] can prove this
theorem toComplex_one : ((1 : ℤ[i]) : ℂ) = 1 :=
toComplex.map_one
#align gaussian_int.to_complex_one GaussianInt.toComplex_one
-- Porting note (#10618): @[simp] can prove this
theorem toComplex_zero : ((0 : ℤ[i]) : ℂ) = 0 :=
toComplex.map_zero
#align gaussian_int.to_complex_zero GaussianInt.toComplex_zero
-- Porting note (#10618): @[simp] can prove this
theorem toComplex_neg (x : ℤ[i]) : ((-x : ℤ[i]) : ℂ) = -x :=
toComplex.map_neg _
#align gaussian_int.to_complex_neg GaussianInt.toComplex_neg
-- Porting note (#10618): @[simp] can prove this
theorem toComplex_sub (x y : ℤ[i]) : ((x - y : ℤ[i]) : ℂ) = x - y :=
toComplex.map_sub _ _
#align gaussian_int.to_complex_sub GaussianInt.toComplex_sub
@[simp]
theorem toComplex_star (x : ℤ[i]) : ((star x : ℤ[i]) : ℂ) = conj (x : ℂ) := by
rw [toComplex_def₂, toComplex_def₂]
exact congr_arg₂ _ rfl (Int.cast_neg _)
#align gaussian_int.to_complex_star GaussianInt.toComplex_star
@[simp]
theorem toComplex_inj {x y : ℤ[i]} : (x : ℂ) = y ↔ x = y := by
cases x; cases y; simp [toComplex_def₂]
#align gaussian_int.to_complex_inj GaussianInt.toComplex_inj
lemma toComplex_injective : Function.Injective GaussianInt.toComplex :=
fun ⦃_ _⦄ ↦ toComplex_inj.mp
@[simp]
theorem toComplex_eq_zero {x : ℤ[i]} : (x : ℂ) = 0 ↔ x = 0 := by
rw [← toComplex_zero, toComplex_inj]
#align gaussian_int.to_complex_eq_zero GaussianInt.toComplex_eq_zero
@[simp]
theorem intCast_real_norm (x : ℤ[i]) : (x.norm : ℝ) = Complex.normSq (x : ℂ) := by
rw [Zsqrtd.norm, normSq]; simp
#align gaussian_int.nat_cast_real_norm GaussianInt.intCast_real_norm
@[deprecated (since := "2024-04-17")]
alias int_cast_real_norm := intCast_real_norm
@[simp]
theorem intCast_complex_norm (x : ℤ[i]) : (x.norm : ℂ) = Complex.normSq (x : ℂ) := by
cases x; rw [Zsqrtd.norm, normSq]; simp
#align gaussian_int.nat_cast_complex_norm GaussianInt.intCast_complex_norm
@[deprecated (since := "2024-04-17")]
alias int_cast_complex_norm := intCast_complex_norm
theorem norm_nonneg (x : ℤ[i]) : 0 ≤ norm x :=
Zsqrtd.norm_nonneg (by norm_num) _
#align gaussian_int.norm_nonneg GaussianInt.norm_nonneg
@[simp]
theorem norm_eq_zero {x : ℤ[i]} : norm x = 0 ↔ x = 0 := by rw [← @Int.cast_inj ℝ _ _ _]; simp
#align gaussian_int.norm_eq_zero GaussianInt.norm_eq_zero
theorem norm_pos {x : ℤ[i]} : 0 < norm x ↔ x ≠ 0 := by
rw [lt_iff_le_and_ne, Ne, eq_comm, norm_eq_zero]; simp [norm_nonneg]
#align gaussian_int.norm_pos GaussianInt.norm_pos
theorem abs_natCast_norm (x : ℤ[i]) : (x.norm.natAbs : ℤ) = x.norm :=
Int.natAbs_of_nonneg (norm_nonneg _)
#align gaussian_int.abs_coe_nat_norm GaussianInt.abs_natCast_norm
-- 2024-04-05
@[deprecated] alias abs_coe_nat_norm := abs_natCast_norm
@[simp]
theorem natCast_natAbs_norm {α : Type*} [Ring α] (x : ℤ[i]) : (x.norm.natAbs : α) = x.norm := by
rw [← Int.cast_natCast, abs_natCast_norm]
#align gaussian_int.nat_cast_nat_abs_norm GaussianInt.natCast_natAbs_norm
@[deprecated (since := "2024-04-17")]
alias nat_cast_natAbs_norm := natCast_natAbs_norm
theorem natAbs_norm_eq (x : ℤ[i]) :
x.norm.natAbs = x.re.natAbs * x.re.natAbs + x.im.natAbs * x.im.natAbs :=
Int.ofNat.inj <| by simp; simp [Zsqrtd.norm]
#align gaussian_int.nat_abs_norm_eq GaussianInt.natAbs_norm_eq
instance : Div ℤ[i] :=
⟨fun x y =>
let n := (norm y : ℚ)⁻¹
let c := star y
⟨round ((x * c).re * n : ℚ), round ((x * c).im * n : ℚ)⟩⟩
theorem div_def (x y : ℤ[i]) :
x / y = ⟨round ((x * star y).re / norm y : ℚ), round ((x * star y).im / norm y : ℚ)⟩ :=
show Zsqrtd.mk _ _ = _ by simp [div_eq_mul_inv]
#align gaussian_int.div_def GaussianInt.div_def
theorem toComplex_div_re (x y : ℤ[i]) : ((x / y : ℤ[i]) : ℂ).re = round (x / y : ℂ).re := by
rw [div_def, ← @Rat.round_cast ℝ _ _]
simp [-Rat.round_cast, mul_assoc, div_eq_mul_inv, mul_add, add_mul]
#align gaussian_int.to_complex_div_re GaussianInt.toComplex_div_re
theorem toComplex_div_im (x y : ℤ[i]) : ((x / y : ℤ[i]) : ℂ).im = round (x / y : ℂ).im := by
rw [div_def, ← @Rat.round_cast ℝ _ _, ← @Rat.round_cast ℝ _ _]
simp [-Rat.round_cast, mul_assoc, div_eq_mul_inv, mul_add, add_mul]
#align gaussian_int.to_complex_div_im GaussianInt.toComplex_div_im
theorem normSq_le_normSq_of_re_le_of_im_le {x y : ℂ} (hre : |x.re| ≤ |y.re|)
(him : |x.im| ≤ |y.im|) : Complex.normSq x ≤ Complex.normSq y := by
rw [normSq_apply, normSq_apply, ← _root_.abs_mul_self, _root_.abs_mul, ←
_root_.abs_mul_self y.re, _root_.abs_mul y.re, ← _root_.abs_mul_self x.im,
_root_.abs_mul x.im, ← _root_.abs_mul_self y.im, _root_.abs_mul y.im]
exact
add_le_add (mul_self_le_mul_self (abs_nonneg _) hre) (mul_self_le_mul_self (abs_nonneg _) him)
#align gaussian_int.norm_sq_le_norm_sq_of_re_le_of_im_le GaussianInt.normSq_le_normSq_of_re_le_of_im_le
| Mathlib/NumberTheory/Zsqrtd/GaussianInt.lean | 231 | 244 | theorem normSq_div_sub_div_lt_one (x y : ℤ[i]) :
Complex.normSq ((x / y : ℂ) - ((x / y : ℤ[i]) : ℂ)) < 1 :=
calc
Complex.normSq ((x / y : ℂ) - ((x / y : ℤ[i]) : ℂ))
_ = Complex.normSq
((x / y : ℂ).re - ((x / y : ℤ[i]) : ℂ).re + ((x / y : ℂ).im - ((x / y : ℤ[i]) : ℂ).im) *
I : ℂ) :=
congr_arg _ <| by apply Complex.ext <;> simp
_ ≤ Complex.normSq (1 / 2 + 1 / 2 * I) := by |
have : |(2⁻¹ : ℝ)| = 2⁻¹ := abs_of_nonneg (by norm_num)
exact normSq_le_normSq_of_re_le_of_im_le
(by rw [toComplex_div_re]; simp [normSq, this]; simpa using abs_sub_round (x / y : ℂ).re)
(by rw [toComplex_div_im]; simp [normSq, this]; simpa using abs_sub_round (x / y : ℂ).im)
_ < 1 := by simp [normSq]; norm_num
|
/-
Copyright (c) 2024 Lawrence Wu. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Lawrence Wu
-/
import Mathlib.MeasureTheory.Group.Measure
import Mathlib.MeasureTheory.Integral.IntegrableOn
import Mathlib.MeasureTheory.Function.LocallyIntegrable
/-!
# Bounding of integrals by asymptotics
We establish integrability of `f` from `f = O(g)`.
## Main results
* `Asymptotics.IsBigO.integrableAtFilter`: If `f = O[l] g` on measurably generated `l`,
`f` is strongly measurable at `l`, and `g` is integrable at `l`, then `f` is integrable at `l`.
* `MeasureTheory.LocallyIntegrable.integrable_of_isBigO_cocompact`: If `f` is locally integrable,
and `f =O[cocompact] g` for some `g` integrable at `cocompact`, then `f` is integrable.
* `MeasureTheory.LocallyIntegrable.integrable_of_isBigO_atBot_atTop`: If `f` is locally integrable,
and `f =O[atBot] g`, `f =O[atTop] g'` for some `g`, `g'` integrable `atBot` and `atTop`
respectively, then `f` is integrable.
* `MeasureTheory.LocallyIntegrable.integrable_of_isBigO_atTop_of_norm_isNegInvariant`:
If `f` is locally integrable, `‖f(-x)‖ = ‖f(x)‖`, and `f =O[atTop] g` for some
`g` integrable `atTop`, then `f` is integrable.
-/
open Asymptotics MeasureTheory Set Filter
variable {α E F : Type*} [MeasurableSpace α] [NormedAddCommGroup E] [NormedAddCommGroup F]
{f : α → E} {g : α → F} {a b : α} {μ : Measure α} {l : Filter α}
/-- If `f = O[l] g` on measurably generated `l`, `f` is strongly measurable at `l`,
and `g` is integrable at `l`, then `f` is integrable at `l`. -/
theorem _root_.Asymptotics.IsBigO.integrableAtFilter [IsMeasurablyGenerated l]
(hf : f =O[l] g) (hfm : StronglyMeasurableAtFilter f l μ) (hg : IntegrableAtFilter g l μ) :
IntegrableAtFilter f l μ := by
obtain ⟨C, hC⟩ := hf.bound
obtain ⟨s, hsl, hsm, hfg, hf, hg⟩ :=
(hC.smallSets.and <| hfm.eventually.and hg.eventually).exists_measurable_mem_of_smallSets
refine ⟨s, hsl, (hg.norm.const_mul C).mono hf ?_⟩
refine (ae_restrict_mem hsm).mono fun x hx ↦ ?_
exact (hfg x hx).trans (le_abs_self _)
/-- Variant of `MeasureTheory.Integrable.mono` taking `f =O[⊤] (g)` instead of `‖f(x)‖ ≤ ‖g(x)‖` -/
theorem _root_.Asymptotics.IsBigO.integrable (hfm : AEStronglyMeasurable f μ)
(hf : f =O[⊤] g) (hg : Integrable g μ) : Integrable f μ := by
rewrite [← integrableAtFilter_top] at *
exact hf.integrableAtFilter ⟨univ, univ_mem, hfm.restrict⟩ hg
variable [TopologicalSpace α] [SecondCountableTopology α]
namespace MeasureTheory
/-- If `f` is locally integrable, and `f =O[cocompact] g` for some `g` integrable at `cocompact`,
then `f` is integrable. -/
| Mathlib/MeasureTheory/Integral/Asymptotics.lean | 58 | 62 | theorem LocallyIntegrable.integrable_of_isBigO_cocompact [IsMeasurablyGenerated (cocompact α)]
(hf : LocallyIntegrable f μ) (ho : f =O[cocompact α] g)
(hg : IntegrableAtFilter g (cocompact α) μ) : Integrable f μ := by |
refine integrable_iff_integrableAtFilter_cocompact.mpr ⟨ho.integrableAtFilter ?_ hg, hf⟩
exact hf.aestronglyMeasurable.stronglyMeasurableAtFilter
|
/-
Copyright (c) 2020 Thomas Browning, Patrick Lutz. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Thomas Browning, Patrick Lutz
-/
import Mathlib.Algebra.Algebra.Subalgebra.Directed
import Mathlib.FieldTheory.IntermediateField
import Mathlib.FieldTheory.Separable
import Mathlib.FieldTheory.SplittingField.IsSplittingField
import Mathlib.RingTheory.TensorProduct.Basic
#align_import field_theory.adjoin from "leanprover-community/mathlib"@"df76f43357840485b9d04ed5dee5ab115d420e87"
/-!
# Adjoining Elements to Fields
In this file we introduce the notion of adjoining elements to fields.
This isn't quite the same as adjoining elements to rings.
For example, `Algebra.adjoin K {x}` might not include `x⁻¹`.
## Main results
- `adjoin_adjoin_left`: adjoining S and then T is the same as adjoining `S ∪ T`.
- `bot_eq_top_of_rank_adjoin_eq_one`: if `F⟮x⟯` has dimension `1` over `F` for every `x`
in `E` then `F = E`
## Notation
- `F⟮α⟯`: adjoin a single element `α` to `F` (in scope `IntermediateField`).
-/
set_option autoImplicit true
open FiniteDimensional Polynomial
open scoped Classical Polynomial
namespace IntermediateField
section AdjoinDef
variable (F : Type*) [Field F] {E : Type*} [Field E] [Algebra F E] (S : Set E)
-- Porting note: not adding `neg_mem'` causes an error.
/-- `adjoin F S` extends a field `F` by adjoining a set `S ⊆ E`. -/
def adjoin : IntermediateField F E :=
{ Subfield.closure (Set.range (algebraMap F E) ∪ S) with
algebraMap_mem' := fun x => Subfield.subset_closure (Or.inl (Set.mem_range_self x)) }
#align intermediate_field.adjoin IntermediateField.adjoin
variable {S}
theorem mem_adjoin_iff (x : E) :
x ∈ adjoin F S ↔ ∃ r s : MvPolynomial S F,
x = MvPolynomial.aeval Subtype.val r / MvPolynomial.aeval Subtype.val s := by
simp only [adjoin, mem_mk, Subring.mem_toSubsemiring, Subfield.mem_toSubring,
Subfield.mem_closure_iff, ← Algebra.adjoin_eq_ring_closure, Subalgebra.mem_toSubring,
Algebra.adjoin_eq_range, AlgHom.mem_range, exists_exists_eq_and]
tauto
theorem mem_adjoin_simple_iff {α : E} (x : E) :
x ∈ adjoin F {α} ↔ ∃ r s : F[X], x = aeval α r / aeval α s := by
simp only [adjoin, mem_mk, Subring.mem_toSubsemiring, Subfield.mem_toSubring,
Subfield.mem_closure_iff, ← Algebra.adjoin_eq_ring_closure, Subalgebra.mem_toSubring,
Algebra.adjoin_singleton_eq_range_aeval, AlgHom.mem_range, exists_exists_eq_and]
tauto
end AdjoinDef
section Lattice
variable {F : Type*} [Field F] {E : Type*} [Field E] [Algebra F E]
@[simp]
theorem adjoin_le_iff {S : Set E} {T : IntermediateField F E} : adjoin F S ≤ T ↔ S ≤ T :=
⟨fun H => le_trans (le_trans Set.subset_union_right Subfield.subset_closure) H, fun H =>
(@Subfield.closure_le E _ (Set.range (algebraMap F E) ∪ S) T.toSubfield).mpr
(Set.union_subset (IntermediateField.set_range_subset T) H)⟩
#align intermediate_field.adjoin_le_iff IntermediateField.adjoin_le_iff
theorem gc : GaloisConnection (adjoin F : Set E → IntermediateField F E)
(fun (x : IntermediateField F E) => (x : Set E)) := fun _ _ =>
adjoin_le_iff
#align intermediate_field.gc IntermediateField.gc
/-- Galois insertion between `adjoin` and `coe`. -/
def gi : GaloisInsertion (adjoin F : Set E → IntermediateField F E)
(fun (x : IntermediateField F E) => (x : Set E)) where
choice s hs := (adjoin F s).copy s <| le_antisymm (gc.le_u_l s) hs
gc := IntermediateField.gc
le_l_u S := (IntermediateField.gc (S : Set E) (adjoin F S)).1 <| le_rfl
choice_eq _ _ := copy_eq _ _ _
#align intermediate_field.gi IntermediateField.gi
instance : CompleteLattice (IntermediateField F E) where
__ := GaloisInsertion.liftCompleteLattice IntermediateField.gi
bot :=
{ toSubalgebra := ⊥
inv_mem' := by rintro x ⟨r, rfl⟩; exact ⟨r⁻¹, map_inv₀ _ _⟩ }
bot_le x := (bot_le : ⊥ ≤ x.toSubalgebra)
instance : Inhabited (IntermediateField F E) :=
⟨⊤⟩
instance : Unique (IntermediateField F F) :=
{ inferInstanceAs (Inhabited (IntermediateField F F)) with
uniq := fun _ ↦ toSubalgebra_injective <| Subsingleton.elim _ _ }
theorem coe_bot : ↑(⊥ : IntermediateField F E) = Set.range (algebraMap F E) := rfl
#align intermediate_field.coe_bot IntermediateField.coe_bot
theorem mem_bot {x : E} : x ∈ (⊥ : IntermediateField F E) ↔ x ∈ Set.range (algebraMap F E) :=
Iff.rfl
#align intermediate_field.mem_bot IntermediateField.mem_bot
@[simp]
theorem bot_toSubalgebra : (⊥ : IntermediateField F E).toSubalgebra = ⊥ := rfl
#align intermediate_field.bot_to_subalgebra IntermediateField.bot_toSubalgebra
@[simp]
theorem coe_top : ↑(⊤ : IntermediateField F E) = (Set.univ : Set E) :=
rfl
#align intermediate_field.coe_top IntermediateField.coe_top
@[simp]
theorem mem_top {x : E} : x ∈ (⊤ : IntermediateField F E) :=
trivial
#align intermediate_field.mem_top IntermediateField.mem_top
@[simp]
theorem top_toSubalgebra : (⊤ : IntermediateField F E).toSubalgebra = ⊤ :=
rfl
#align intermediate_field.top_to_subalgebra IntermediateField.top_toSubalgebra
@[simp]
theorem top_toSubfield : (⊤ : IntermediateField F E).toSubfield = ⊤ :=
rfl
#align intermediate_field.top_to_subfield IntermediateField.top_toSubfield
@[simp, norm_cast]
theorem coe_inf (S T : IntermediateField F E) : (↑(S ⊓ T) : Set E) = (S : Set E) ∩ T :=
rfl
#align intermediate_field.coe_inf IntermediateField.coe_inf
@[simp]
theorem mem_inf {S T : IntermediateField F E} {x : E} : x ∈ S ⊓ T ↔ x ∈ S ∧ x ∈ T :=
Iff.rfl
#align intermediate_field.mem_inf IntermediateField.mem_inf
@[simp]
theorem inf_toSubalgebra (S T : IntermediateField F E) :
(S ⊓ T).toSubalgebra = S.toSubalgebra ⊓ T.toSubalgebra :=
rfl
#align intermediate_field.inf_to_subalgebra IntermediateField.inf_toSubalgebra
@[simp]
theorem inf_toSubfield (S T : IntermediateField F E) :
(S ⊓ T).toSubfield = S.toSubfield ⊓ T.toSubfield :=
rfl
#align intermediate_field.inf_to_subfield IntermediateField.inf_toSubfield
@[simp, norm_cast]
theorem coe_sInf (S : Set (IntermediateField F E)) : (↑(sInf S) : Set E) =
sInf ((fun (x : IntermediateField F E) => (x : Set E)) '' S) :=
rfl
#align intermediate_field.coe_Inf IntermediateField.coe_sInf
@[simp]
theorem sInf_toSubalgebra (S : Set (IntermediateField F E)) :
(sInf S).toSubalgebra = sInf (toSubalgebra '' S) :=
SetLike.coe_injective <| by simp [Set.sUnion_image]
#align intermediate_field.Inf_to_subalgebra IntermediateField.sInf_toSubalgebra
@[simp]
theorem sInf_toSubfield (S : Set (IntermediateField F E)) :
(sInf S).toSubfield = sInf (toSubfield '' S) :=
SetLike.coe_injective <| by simp [Set.sUnion_image]
#align intermediate_field.Inf_to_subfield IntermediateField.sInf_toSubfield
@[simp, norm_cast]
theorem coe_iInf {ι : Sort*} (S : ι → IntermediateField F E) : (↑(iInf S) : Set E) = ⋂ i, S i := by
simp [iInf]
#align intermediate_field.coe_infi IntermediateField.coe_iInf
@[simp]
theorem iInf_toSubalgebra {ι : Sort*} (S : ι → IntermediateField F E) :
(iInf S).toSubalgebra = ⨅ i, (S i).toSubalgebra :=
SetLike.coe_injective <| by simp [iInf]
#align intermediate_field.infi_to_subalgebra IntermediateField.iInf_toSubalgebra
@[simp]
theorem iInf_toSubfield {ι : Sort*} (S : ι → IntermediateField F E) :
(iInf S).toSubfield = ⨅ i, (S i).toSubfield :=
SetLike.coe_injective <| by simp [iInf]
#align intermediate_field.infi_to_subfield IntermediateField.iInf_toSubfield
/-- Construct an algebra isomorphism from an equality of intermediate fields -/
@[simps! apply]
def equivOfEq {S T : IntermediateField F E} (h : S = T) : S ≃ₐ[F] T :=
Subalgebra.equivOfEq _ _ (congr_arg toSubalgebra h)
#align intermediate_field.equiv_of_eq IntermediateField.equivOfEq
@[simp]
theorem equivOfEq_symm {S T : IntermediateField F E} (h : S = T) :
(equivOfEq h).symm = equivOfEq h.symm :=
rfl
#align intermediate_field.equiv_of_eq_symm IntermediateField.equivOfEq_symm
@[simp]
theorem equivOfEq_rfl (S : IntermediateField F E) : equivOfEq (rfl : S = S) = AlgEquiv.refl := by
ext; rfl
#align intermediate_field.equiv_of_eq_rfl IntermediateField.equivOfEq_rfl
@[simp]
theorem equivOfEq_trans {S T U : IntermediateField F E} (hST : S = T) (hTU : T = U) :
(equivOfEq hST).trans (equivOfEq hTU) = equivOfEq (hST.trans hTU) :=
rfl
#align intermediate_field.equiv_of_eq_trans IntermediateField.equivOfEq_trans
variable (F E)
/-- The bottom intermediate_field is isomorphic to the field. -/
noncomputable def botEquiv : (⊥ : IntermediateField F E) ≃ₐ[F] F :=
(Subalgebra.equivOfEq _ _ bot_toSubalgebra).trans (Algebra.botEquiv F E)
#align intermediate_field.bot_equiv IntermediateField.botEquiv
variable {F E}
-- Porting note: this was tagged `simp`.
theorem botEquiv_def (x : F) : botEquiv F E (algebraMap F (⊥ : IntermediateField F E) x) = x := by
simp
#align intermediate_field.bot_equiv_def IntermediateField.botEquiv_def
@[simp]
theorem botEquiv_symm (x : F) : (botEquiv F E).symm x = algebraMap F _ x :=
rfl
#align intermediate_field.bot_equiv_symm IntermediateField.botEquiv_symm
noncomputable instance algebraOverBot : Algebra (⊥ : IntermediateField F E) F :=
(IntermediateField.botEquiv F E).toAlgHom.toRingHom.toAlgebra
#align intermediate_field.algebra_over_bot IntermediateField.algebraOverBot
theorem coe_algebraMap_over_bot :
(algebraMap (⊥ : IntermediateField F E) F : (⊥ : IntermediateField F E) → F) =
IntermediateField.botEquiv F E :=
rfl
#align intermediate_field.coe_algebra_map_over_bot IntermediateField.coe_algebraMap_over_bot
instance isScalarTower_over_bot : IsScalarTower (⊥ : IntermediateField F E) F E :=
IsScalarTower.of_algebraMap_eq
(by
intro x
obtain ⟨y, rfl⟩ := (botEquiv F E).symm.surjective x
rw [coe_algebraMap_over_bot, (botEquiv F E).apply_symm_apply, botEquiv_symm,
IsScalarTower.algebraMap_apply F (⊥ : IntermediateField F E) E])
#align intermediate_field.is_scalar_tower_over_bot IntermediateField.isScalarTower_over_bot
/-- The top `IntermediateField` is isomorphic to the field.
This is the intermediate field version of `Subalgebra.topEquiv`. -/
@[simps!]
def topEquiv : (⊤ : IntermediateField F E) ≃ₐ[F] E :=
(Subalgebra.equivOfEq _ _ top_toSubalgebra).trans Subalgebra.topEquiv
#align intermediate_field.top_equiv IntermediateField.topEquiv
-- Porting note: this theorem is now generated by the `@[simps!]` above.
#align intermediate_field.top_equiv_symm_apply_coe IntermediateField.topEquiv_symm_apply_coe
@[simp]
theorem restrictScalars_bot_eq_self (K : IntermediateField F E) :
(⊥ : IntermediateField K E).restrictScalars _ = K :=
SetLike.coe_injective Subtype.range_coe
#align intermediate_field.restrict_scalars_bot_eq_self IntermediateField.restrictScalars_bot_eq_self
@[simp]
theorem restrictScalars_top {K : Type*} [Field K] [Algebra K E] [Algebra K F]
[IsScalarTower K F E] : (⊤ : IntermediateField F E).restrictScalars K = ⊤ :=
rfl
#align intermediate_field.restrict_scalars_top IntermediateField.restrictScalars_top
variable {K : Type*} [Field K] [Algebra F K]
@[simp]
theorem map_bot (f : E →ₐ[F] K) :
IntermediateField.map f ⊥ = ⊥ :=
toSubalgebra_injective <| Algebra.map_bot _
theorem map_sup (s t : IntermediateField F E) (f : E →ₐ[F] K) : (s ⊔ t).map f = s.map f ⊔ t.map f :=
(gc_map_comap f).l_sup
theorem map_iSup {ι : Sort*} (f : E →ₐ[F] K) (s : ι → IntermediateField F E) :
(iSup s).map f = ⨆ i, (s i).map f :=
(gc_map_comap f).l_iSup
theorem _root_.AlgHom.fieldRange_eq_map (f : E →ₐ[F] K) :
f.fieldRange = IntermediateField.map f ⊤ :=
SetLike.ext' Set.image_univ.symm
#align alg_hom.field_range_eq_map AlgHom.fieldRange_eq_map
theorem _root_.AlgHom.map_fieldRange {L : Type*} [Field L] [Algebra F L]
(f : E →ₐ[F] K) (g : K →ₐ[F] L) : f.fieldRange.map g = (g.comp f).fieldRange :=
SetLike.ext' (Set.range_comp g f).symm
#align alg_hom.map_field_range AlgHom.map_fieldRange
theorem _root_.AlgHom.fieldRange_eq_top {f : E →ₐ[F] K} :
f.fieldRange = ⊤ ↔ Function.Surjective f :=
SetLike.ext'_iff.trans Set.range_iff_surjective
#align alg_hom.field_range_eq_top AlgHom.fieldRange_eq_top
@[simp]
theorem _root_.AlgEquiv.fieldRange_eq_top (f : E ≃ₐ[F] K) :
(f : E →ₐ[F] K).fieldRange = ⊤ :=
AlgHom.fieldRange_eq_top.mpr f.surjective
#align alg_equiv.field_range_eq_top AlgEquiv.fieldRange_eq_top
end Lattice
section equivMap
variable {F : Type*} [Field F] {E : Type*} [Field E] [Algebra F E]
{K : Type*} [Field K] [Algebra F K] (L : IntermediateField F E) (f : E →ₐ[F] K)
theorem fieldRange_comp_val : (f.comp L.val).fieldRange = L.map f := toSubalgebra_injective <| by
rw [toSubalgebra_map, AlgHom.fieldRange_toSubalgebra, AlgHom.range_comp, range_val]
/-- An intermediate field is isomorphic to its image under an `AlgHom`
(which is automatically injective) -/
noncomputable def equivMap : L ≃ₐ[F] L.map f :=
(AlgEquiv.ofInjective _ (f.comp L.val).injective).trans (equivOfEq (fieldRange_comp_val L f))
@[simp]
theorem coe_equivMap_apply (x : L) : ↑(equivMap L f x) = f x := rfl
end equivMap
section AdjoinDef
variable (F : Type*) [Field F] {E : Type*} [Field E] [Algebra F E] (S : Set E)
theorem adjoin_eq_range_algebraMap_adjoin :
(adjoin F S : Set E) = Set.range (algebraMap (adjoin F S) E) :=
Subtype.range_coe.symm
#align intermediate_field.adjoin_eq_range_algebra_map_adjoin IntermediateField.adjoin_eq_range_algebraMap_adjoin
theorem adjoin.algebraMap_mem (x : F) : algebraMap F E x ∈ adjoin F S :=
IntermediateField.algebraMap_mem (adjoin F S) x
#align intermediate_field.adjoin.algebra_map_mem IntermediateField.adjoin.algebraMap_mem
theorem adjoin.range_algebraMap_subset : Set.range (algebraMap F E) ⊆ adjoin F S := by
intro x hx
cases' hx with f hf
rw [← hf]
exact adjoin.algebraMap_mem F S f
#align intermediate_field.adjoin.range_algebra_map_subset IntermediateField.adjoin.range_algebraMap_subset
instance adjoin.fieldCoe : CoeTC F (adjoin F S) where
coe x := ⟨algebraMap F E x, adjoin.algebraMap_mem F S x⟩
#align intermediate_field.adjoin.field_coe IntermediateField.adjoin.fieldCoe
theorem subset_adjoin : S ⊆ adjoin F S := fun _ hx => Subfield.subset_closure (Or.inr hx)
#align intermediate_field.subset_adjoin IntermediateField.subset_adjoin
instance adjoin.setCoe : CoeTC S (adjoin F S) where coe x := ⟨x, subset_adjoin F S (Subtype.mem x)⟩
#align intermediate_field.adjoin.set_coe IntermediateField.adjoin.setCoe
@[mono]
theorem adjoin.mono (T : Set E) (h : S ⊆ T) : adjoin F S ≤ adjoin F T :=
GaloisConnection.monotone_l gc h
#align intermediate_field.adjoin.mono IntermediateField.adjoin.mono
theorem adjoin_contains_field_as_subfield (F : Subfield E) : (F : Set E) ⊆ adjoin F S := fun x hx =>
adjoin.algebraMap_mem F S ⟨x, hx⟩
#align intermediate_field.adjoin_contains_field_as_subfield IntermediateField.adjoin_contains_field_as_subfield
theorem subset_adjoin_of_subset_left {F : Subfield E} {T : Set E} (HT : T ⊆ F) : T ⊆ adjoin F S :=
fun x hx => (adjoin F S).algebraMap_mem ⟨x, HT hx⟩
#align intermediate_field.subset_adjoin_of_subset_left IntermediateField.subset_adjoin_of_subset_left
theorem subset_adjoin_of_subset_right {T : Set E} (H : T ⊆ S) : T ⊆ adjoin F S := fun _ hx =>
subset_adjoin F S (H hx)
#align intermediate_field.subset_adjoin_of_subset_right IntermediateField.subset_adjoin_of_subset_right
@[simp]
theorem adjoin_empty (F E : Type*) [Field F] [Field E] [Algebra F E] : adjoin F (∅ : Set E) = ⊥ :=
eq_bot_iff.mpr (adjoin_le_iff.mpr (Set.empty_subset _))
#align intermediate_field.adjoin_empty IntermediateField.adjoin_empty
@[simp]
theorem adjoin_univ (F E : Type*) [Field F] [Field E] [Algebra F E] :
adjoin F (Set.univ : Set E) = ⊤ :=
eq_top_iff.mpr <| subset_adjoin _ _
#align intermediate_field.adjoin_univ IntermediateField.adjoin_univ
/-- If `K` is a field with `F ⊆ K` and `S ⊆ K` then `adjoin F S ≤ K`. -/
theorem adjoin_le_subfield {K : Subfield E} (HF : Set.range (algebraMap F E) ⊆ K) (HS : S ⊆ K) :
(adjoin F S).toSubfield ≤ K := by
apply Subfield.closure_le.mpr
rw [Set.union_subset_iff]
exact ⟨HF, HS⟩
#align intermediate_field.adjoin_le_subfield IntermediateField.adjoin_le_subfield
theorem adjoin_subset_adjoin_iff {F' : Type*} [Field F'] [Algebra F' E] {S S' : Set E} :
(adjoin F S : Set E) ⊆ adjoin F' S' ↔
Set.range (algebraMap F E) ⊆ adjoin F' S' ∧ S ⊆ adjoin F' S' :=
⟨fun h => ⟨(adjoin.range_algebraMap_subset _ _).trans h,
(subset_adjoin _ _).trans h⟩, fun ⟨hF, hS⟩ =>
(Subfield.closure_le (t := (adjoin F' S').toSubfield)).mpr (Set.union_subset hF hS)⟩
#align intermediate_field.adjoin_subset_adjoin_iff IntermediateField.adjoin_subset_adjoin_iff
/-- `F[S][T] = F[S ∪ T]` -/
theorem adjoin_adjoin_left (T : Set E) :
(adjoin (adjoin F S) T).restrictScalars _ = adjoin F (S ∪ T) := by
rw [SetLike.ext'_iff]
change (↑(adjoin (adjoin F S) T) : Set E) = _
apply Set.eq_of_subset_of_subset <;> rw [adjoin_subset_adjoin_iff] <;> constructor
· rintro _ ⟨⟨x, hx⟩, rfl⟩; exact adjoin.mono _ _ _ Set.subset_union_left hx
· exact subset_adjoin_of_subset_right _ _ Set.subset_union_right
-- Porting note: orginal proof times out
· rintro x ⟨f, rfl⟩
refine Subfield.subset_closure ?_
left
exact ⟨f, rfl⟩
-- Porting note: orginal proof times out
· refine Set.union_subset (fun x hx => Subfield.subset_closure ?_)
(fun x hx => Subfield.subset_closure ?_)
· left
refine ⟨⟨x, Subfield.subset_closure ?_⟩, rfl⟩
right
exact hx
· right
exact hx
#align intermediate_field.adjoin_adjoin_left IntermediateField.adjoin_adjoin_left
@[simp]
theorem adjoin_insert_adjoin (x : E) :
adjoin F (insert x (adjoin F S : Set E)) = adjoin F (insert x S) :=
le_antisymm
(adjoin_le_iff.mpr
(Set.insert_subset_iff.mpr
⟨subset_adjoin _ _ (Set.mem_insert _ _),
adjoin_le_iff.mpr (subset_adjoin_of_subset_right _ _ (Set.subset_insert _ _))⟩))
(adjoin.mono _ _ _ (Set.insert_subset_insert (subset_adjoin _ _)))
#align intermediate_field.adjoin_insert_adjoin IntermediateField.adjoin_insert_adjoin
/-- `F[S][T] = F[T][S]` -/
theorem adjoin_adjoin_comm (T : Set E) :
(adjoin (adjoin F S) T).restrictScalars F = (adjoin (adjoin F T) S).restrictScalars F := by
rw [adjoin_adjoin_left, adjoin_adjoin_left, Set.union_comm]
#align intermediate_field.adjoin_adjoin_comm IntermediateField.adjoin_adjoin_comm
theorem adjoin_map {E' : Type*} [Field E'] [Algebra F E'] (f : E →ₐ[F] E') :
(adjoin F S).map f = adjoin F (f '' S) := by
ext x
show
x ∈ (Subfield.closure (Set.range (algebraMap F E) ∪ S)).map (f : E →+* E') ↔
x ∈ Subfield.closure (Set.range (algebraMap F E') ∪ f '' S)
rw [RingHom.map_field_closure, Set.image_union, ← Set.range_comp, ← RingHom.coe_comp,
f.comp_algebraMap]
rfl
#align intermediate_field.adjoin_map IntermediateField.adjoin_map
@[simp]
theorem lift_adjoin (K : IntermediateField F E) (S : Set K) :
lift (adjoin F S) = adjoin F (Subtype.val '' S) :=
adjoin_map _ _ _
theorem lift_adjoin_simple (K : IntermediateField F E) (α : K) :
lift (adjoin F {α}) = adjoin F {α.1} := by
simp only [lift_adjoin, Set.image_singleton]
@[simp]
theorem lift_bot (K : IntermediateField F E) :
lift (F := K) ⊥ = ⊥ := map_bot _
@[simp]
theorem lift_top (K : IntermediateField F E) :
lift (F := K) ⊤ = K := by rw [lift, ← AlgHom.fieldRange_eq_map, fieldRange_val]
@[simp]
theorem adjoin_self (K : IntermediateField F E) :
adjoin F K = K := le_antisymm (adjoin_le_iff.2 fun _ ↦ id) (subset_adjoin F _)
theorem restrictScalars_adjoin (K : IntermediateField F E) (S : Set E) :
restrictScalars F (adjoin K S) = adjoin F (K ∪ S) := by
rw [← adjoin_self _ K, adjoin_adjoin_left, adjoin_self _ K]
variable {F} in
theorem extendScalars_adjoin {K : IntermediateField F E} {S : Set E} (h : K ≤ adjoin F S) :
extendScalars h = adjoin K S := restrictScalars_injective F <| by
rw [extendScalars_restrictScalars, restrictScalars_adjoin]
exact le_antisymm (adjoin.mono F S _ Set.subset_union_right) <| adjoin_le_iff.2 <|
Set.union_subset h (subset_adjoin F S)
variable {F} in
/-- If `E / L / F` and `E / L' / F` are two field extension towers, `L ≃ₐ[F] L'` is an isomorphism
compatible with `E / L` and `E / L'`, then for any subset `S` of `E`, `L(S)` and `L'(S)` are
equal as intermediate fields of `E / F`. -/
theorem restrictScalars_adjoin_of_algEquiv
{L L' : Type*} [Field L] [Field L']
[Algebra F L] [Algebra L E] [Algebra F L'] [Algebra L' E]
[IsScalarTower F L E] [IsScalarTower F L' E] (i : L ≃ₐ[F] L')
(hi : algebraMap L E = (algebraMap L' E) ∘ i) (S : Set E) :
(adjoin L S).restrictScalars F = (adjoin L' S).restrictScalars F := by
apply_fun toSubfield using (fun K K' h ↦ by
ext x; change x ∈ K.toSubfield ↔ x ∈ K'.toSubfield; rw [h])
change Subfield.closure _ = Subfield.closure _
congr
ext x
exact ⟨fun ⟨y, h⟩ ↦ ⟨i y, by rw [← h, hi]; rfl⟩,
fun ⟨y, h⟩ ↦ ⟨i.symm y, by rw [← h, hi, Function.comp_apply, AlgEquiv.apply_symm_apply]⟩⟩
theorem algebra_adjoin_le_adjoin : Algebra.adjoin F S ≤ (adjoin F S).toSubalgebra :=
Algebra.adjoin_le (subset_adjoin _ _)
#align intermediate_field.algebra_adjoin_le_adjoin IntermediateField.algebra_adjoin_le_adjoin
theorem adjoin_eq_algebra_adjoin (inv_mem : ∀ x ∈ Algebra.adjoin F S, x⁻¹ ∈ Algebra.adjoin F S) :
(adjoin F S).toSubalgebra = Algebra.adjoin F S :=
le_antisymm
(show adjoin F S ≤
{ Algebra.adjoin F S with
inv_mem' := inv_mem }
from adjoin_le_iff.mpr Algebra.subset_adjoin)
(algebra_adjoin_le_adjoin _ _)
#align intermediate_field.adjoin_eq_algebra_adjoin IntermediateField.adjoin_eq_algebra_adjoin
| Mathlib/FieldTheory/Adjoin.lean | 527 | 533 | theorem eq_adjoin_of_eq_algebra_adjoin (K : IntermediateField F E)
(h : K.toSubalgebra = Algebra.adjoin F S) : K = adjoin F S := by |
apply toSubalgebra_injective
rw [h]
refine (adjoin_eq_algebra_adjoin F _ ?_).symm
intro x
convert K.inv_mem (x := x) <;> rw [← h] <;> rfl
|
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