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/-
Copyright (c) 2022 Matej Penciak. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Matej Penciak, Moritz Doll, Fabien Clery
-/
import Mathlib.LinearAlgebra.Matrix.NonsingularInverse
#align_import linear_algebra.symplectic_group from "leanprover-community/mathlib"@"70fd9563a21e7b963887c9360bd29b2393e6225a"
/-!
# The Symplectic Group
This file defines the symplectic group and proves elementary properties.
## Main Definitions
* `Matrix.J`: the canonical `2n × 2n` skew-symmetric matrix
* `symplecticGroup`: the group of symplectic matrices
## TODO
* Every symplectic matrix has determinant 1.
* For `n = 1` the symplectic group coincides with the special linear group.
-/
open Matrix
variable {l R : Type*}
namespace Matrix
variable (l) [DecidableEq l] (R) [CommRing R]
section JMatrixLemmas
/-- The matrix defining the canonical skew-symmetric bilinear form. -/
def J : Matrix (Sum l l) (Sum l l) R :=
Matrix.fromBlocks 0 (-1) 1 0
set_option linter.uppercaseLean3 false in
#align matrix.J Matrix.J
@[simp]
| Mathlib/LinearAlgebra/SymplecticGroup.lean | 43 | 46 | theorem J_transpose : (J l R)ᵀ = -J l R := by |
rw [J, fromBlocks_transpose, ← neg_one_smul R (fromBlocks _ _ _ _ : Matrix (l ⊕ l) (l ⊕ l) R),
fromBlocks_smul, Matrix.transpose_zero, Matrix.transpose_one, transpose_neg]
simp [fromBlocks]
|
/-
Copyright (c) 2022 Mario Carneiro. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Mario Carneiro
-/
import Batteries.Data.Rat.Basic
import Batteries.Tactic.SeqFocus
/-! # Additional lemmas about the Rational Numbers -/
namespace Rat
theorem ext : {p q : Rat} → p.num = q.num → p.den = q.den → p = q
| ⟨_,_,_,_⟩, ⟨_,_,_,_⟩, rfl, rfl => rfl
@[simp] theorem mk_den_one {r : Int} :
⟨r, 1, Nat.one_ne_zero, (Nat.coprime_one_right _)⟩ = (r : Rat) := rfl
@[simp] theorem zero_num : (0 : Rat).num = 0 := rfl
@[simp] theorem zero_den : (0 : Rat).den = 1 := rfl
@[simp] theorem one_num : (1 : Rat).num = 1 := rfl
@[simp] theorem one_den : (1 : Rat).den = 1 := rfl
@[simp] theorem maybeNormalize_eq {num den g} (den_nz reduced) :
maybeNormalize num den g den_nz reduced =
{ num := num.div g, den := den / g, den_nz, reduced } := by
unfold maybeNormalize; split
· subst g; simp
· rfl
theorem normalize.reduced' {num : Int} {den g : Nat} (den_nz : den ≠ 0)
(e : g = num.natAbs.gcd den) : (num / g).natAbs.Coprime (den / g) := by
rw [← Int.div_eq_ediv_of_dvd (e ▸ Int.ofNat_dvd_left.2 (Nat.gcd_dvd_left ..))]
exact normalize.reduced den_nz e
theorem normalize_eq {num den} (den_nz) : normalize num den den_nz =
{ num := num / num.natAbs.gcd den
den := den / num.natAbs.gcd den
den_nz := normalize.den_nz den_nz rfl
reduced := normalize.reduced' den_nz rfl } := by
simp only [normalize, maybeNormalize_eq,
Int.div_eq_ediv_of_dvd (Int.ofNat_dvd_left.2 (Nat.gcd_dvd_left ..))]
@[simp] theorem normalize_zero (nz) : normalize 0 d nz = 0 := by
simp [normalize, Int.zero_div, Int.natAbs_zero, Nat.div_self (Nat.pos_of_ne_zero nz)]; rfl
theorem mk_eq_normalize (num den nz c) : ⟨num, den, nz, c⟩ = normalize num den nz := by
simp [normalize_eq, c.gcd_eq_one]
theorem normalize_self (r : Rat) : normalize r.num r.den r.den_nz = r := (mk_eq_normalize ..).symm
theorem normalize_mul_left {a : Nat} (d0 : d ≠ 0) (a0 : a ≠ 0) :
normalize (↑a * n) (a * d) (Nat.mul_ne_zero a0 d0) = normalize n d d0 := by
simp [normalize_eq, mk'.injEq, Int.natAbs_mul, Nat.gcd_mul_left,
Nat.mul_div_mul_left _ _ (Nat.pos_of_ne_zero a0), Int.ofNat_mul,
Int.mul_ediv_mul_of_pos _ _ (Int.ofNat_pos.2 <| Nat.pos_of_ne_zero a0)]
theorem normalize_mul_right {a : Nat} (d0 : d ≠ 0) (a0 : a ≠ 0) :
normalize (n * a) (d * a) (Nat.mul_ne_zero d0 a0) = normalize n d d0 := by
rw [← normalize_mul_left (d0 := d0) a0]; congr 1 <;> [apply Int.mul_comm; apply Nat.mul_comm]
theorem normalize_eq_iff (z₁ : d₁ ≠ 0) (z₂ : d₂ ≠ 0) :
normalize n₁ d₁ z₁ = normalize n₂ d₂ z₂ ↔ n₁ * d₂ = n₂ * d₁ := by
constructor <;> intro h
· simp only [normalize_eq, mk'.injEq] at h
have' hn₁ := Int.ofNat_dvd_left.2 <| Nat.gcd_dvd_left n₁.natAbs d₁
have' hn₂ := Int.ofNat_dvd_left.2 <| Nat.gcd_dvd_left n₂.natAbs d₂
have' hd₁ := Int.ofNat_dvd.2 <| Nat.gcd_dvd_right n₁.natAbs d₁
have' hd₂ := Int.ofNat_dvd.2 <| Nat.gcd_dvd_right n₂.natAbs d₂
rw [← Int.ediv_mul_cancel (Int.dvd_trans hd₂ (Int.dvd_mul_left ..)),
Int.mul_ediv_assoc _ hd₂, ← Int.ofNat_ediv, ← h.2, Int.ofNat_ediv,
← Int.mul_ediv_assoc _ hd₁, Int.mul_ediv_assoc' _ hn₁,
Int.mul_right_comm, h.1, Int.ediv_mul_cancel hn₂]
· rw [← normalize_mul_right _ z₂, ← normalize_mul_left z₂ z₁, Int.mul_comm d₁, h]
theorem maybeNormalize_eq_normalize {num : Int} {den g : Nat} (den_nz reduced)
(hn : ↑g ∣ num) (hd : g ∣ den) :
maybeNormalize num den g den_nz reduced = normalize num den (mt (by simp [·]) den_nz) := by
simp only [maybeNormalize_eq, mk_eq_normalize, Int.div_eq_ediv_of_dvd hn]
have : g ≠ 0 := mt (by simp [·]) den_nz
rw [← normalize_mul_right _ this, Int.ediv_mul_cancel hn]
congr 1; exact Nat.div_mul_cancel hd
@[simp] theorem normalize_eq_zero (d0 : d ≠ 0) : normalize n d d0 = 0 ↔ n = 0 := by
have' := normalize_eq_iff d0 Nat.one_ne_zero
rw [normalize_zero (d := 1)] at this; rw [this]; simp
theorem normalize_num_den' (num den nz) : ∃ d : Nat, d ≠ 0 ∧
num = (normalize num den nz).num * d ∧ den = (normalize num den nz).den * d := by
refine ⟨num.natAbs.gcd den, Nat.gcd_ne_zero_right nz, ?_⟩
simp [normalize_eq, Int.ediv_mul_cancel (Int.ofNat_dvd_left.2 <| Nat.gcd_dvd_left ..),
Nat.div_mul_cancel (Nat.gcd_dvd_right ..)]
theorem normalize_num_den (h : normalize n d z = ⟨n', d', z', c⟩) :
∃ m : Nat, m ≠ 0 ∧ n = n' * m ∧ d = d' * m := by
have := normalize_num_den' n d z; rwa [h] at this
| .lake/packages/batteries/Batteries/Data/Rat/Lemmas.lean | 98 | 99 | theorem normalize_eq_mkRat {num den} (den_nz) : normalize num den den_nz = mkRat num den := by |
simp [mkRat, den_nz]
|
/-
Copyright (c) 2022 Sébastien Gouëzel. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Sébastien Gouëzel
-/
import Mathlib.Algebra.Group.Support
import Mathlib.Data.Set.Pointwise.SMul
#align_import data.set.pointwise.support from "leanprover-community/mathlib"@"f7fc89d5d5ff1db2d1242c7bb0e9062ce47ef47c"
/-!
# Support of a function composed with a scalar action
We show that the support of `x ↦ f (c⁻¹ • x)` is equal to `c • support f`.
-/
open Pointwise
open Function Set
section Group
variable {α β γ : Type*} [Group α] [MulAction α β]
theorem mulSupport_comp_inv_smul [One γ] (c : α) (f : β → γ) :
(mulSupport fun x ↦ f (c⁻¹ • x)) = c • mulSupport f := by
ext x
simp only [mem_smul_set_iff_inv_smul_mem, mem_mulSupport]
#align mul_support_comp_inv_smul mulSupport_comp_inv_smul
/- Note: to_additive also automatically translates `SMul` to `VAdd`, so we give the additive version
manually. -/
theorem support_comp_inv_smul [Zero γ] (c : α) (f : β → γ) :
(support fun x ↦ f (c⁻¹ • x)) = c • support f := by
ext x
simp only [mem_smul_set_iff_inv_smul_mem, mem_support]
#align support_comp_inv_smul support_comp_inv_smul
attribute [to_additive existing support_comp_inv_smul] mulSupport_comp_inv_smul
end Group
section GroupWithZero
variable {α β γ : Type*} [GroupWithZero α] [MulAction α β]
theorem mulSupport_comp_inv_smul₀ [One γ] {c : α} (hc : c ≠ 0) (f : β → γ) :
(mulSupport fun x ↦ f (c⁻¹ • x)) = c • mulSupport f := by
ext x
simp only [mem_smul_set_iff_inv_smul_mem₀ hc, mem_mulSupport]
#align mul_support_comp_inv_smul₀ mulSupport_comp_inv_smul₀
/- Note: to_additive also automatically translates `SMul` to `VAdd`, so we give the additive version
manually. -/
| Mathlib/Data/Set/Pointwise/Support.lean | 56 | 59 | theorem support_comp_inv_smul₀ [Zero γ] {c : α} (hc : c ≠ 0) (f : β → γ) :
(support fun x ↦ f (c⁻¹ • x)) = c • support f := by |
ext x
simp only [mem_smul_set_iff_inv_smul_mem₀ hc, mem_support]
|
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Yury Kudryashov
-/
import Mathlib.Data.ENNReal.Inv
#align_import data.real.ennreal from "leanprover-community/mathlib"@"c14c8fcde993801fca8946b0d80131a1a81d1520"
/-!
# Maps between real and extended non-negative real numbers
This file focuses on the functions `ENNReal.toReal : ℝ≥0∞ → ℝ` and `ENNReal.ofReal : ℝ → ℝ≥0∞` which
were defined in `Data.ENNReal.Basic`. It collects all the basic results of the interactions between
these functions and the algebraic and lattice operations, although a few may appear in earlier
files.
This file provides a `positivity` extension for `ENNReal.ofReal`.
# Main theorems
- `trichotomy (p : ℝ≥0∞) : p = 0 ∨ p = ∞ ∨ 0 < p.toReal`: often used for `WithLp` and `lp`
- `dichotomy (p : ℝ≥0∞) [Fact (1 ≤ p)] : p = ∞ ∨ 1 ≤ p.toReal`: often used for `WithLp` and `lp`
- `toNNReal_iInf` through `toReal_sSup`: these declarations allow for easy conversions between
indexed or set infima and suprema in `ℝ`, `ℝ≥0` and `ℝ≥0∞`. This is especially useful because
`ℝ≥0∞` is a complete lattice.
-/
open Set NNReal ENNReal
namespace ENNReal
section Real
variable {a b c d : ℝ≥0∞} {r p q : ℝ≥0}
theorem toReal_add (ha : a ≠ ∞) (hb : b ≠ ∞) : (a + b).toReal = a.toReal + b.toReal := by
lift a to ℝ≥0 using ha
lift b to ℝ≥0 using hb
rfl
#align ennreal.to_real_add ENNReal.toReal_add
theorem toReal_sub_of_le {a b : ℝ≥0∞} (h : b ≤ a) (ha : a ≠ ∞) :
(a - b).toReal = a.toReal - b.toReal := by
lift b to ℝ≥0 using ne_top_of_le_ne_top ha h
lift a to ℝ≥0 using ha
simp only [← ENNReal.coe_sub, ENNReal.coe_toReal, NNReal.coe_sub (ENNReal.coe_le_coe.mp h)]
#align ennreal.to_real_sub_of_le ENNReal.toReal_sub_of_le
theorem le_toReal_sub {a b : ℝ≥0∞} (hb : b ≠ ∞) : a.toReal - b.toReal ≤ (a - b).toReal := by
lift b to ℝ≥0 using hb
induction a
· simp
· simp only [← coe_sub, NNReal.sub_def, Real.coe_toNNReal', coe_toReal]
exact le_max_left _ _
#align ennreal.le_to_real_sub ENNReal.le_toReal_sub
theorem toReal_add_le : (a + b).toReal ≤ a.toReal + b.toReal :=
if ha : a = ∞ then by simp only [ha, top_add, top_toReal, zero_add, toReal_nonneg]
else
if hb : b = ∞ then by simp only [hb, add_top, top_toReal, add_zero, toReal_nonneg]
else le_of_eq (toReal_add ha hb)
#align ennreal.to_real_add_le ENNReal.toReal_add_le
theorem ofReal_add {p q : ℝ} (hp : 0 ≤ p) (hq : 0 ≤ q) :
ENNReal.ofReal (p + q) = ENNReal.ofReal p + ENNReal.ofReal q := by
rw [ENNReal.ofReal, ENNReal.ofReal, ENNReal.ofReal, ← coe_add, coe_inj,
Real.toNNReal_add hp hq]
#align ennreal.of_real_add ENNReal.ofReal_add
theorem ofReal_add_le {p q : ℝ} : ENNReal.ofReal (p + q) ≤ ENNReal.ofReal p + ENNReal.ofReal q :=
coe_le_coe.2 Real.toNNReal_add_le
#align ennreal.of_real_add_le ENNReal.ofReal_add_le
@[simp]
theorem toReal_le_toReal (ha : a ≠ ∞) (hb : b ≠ ∞) : a.toReal ≤ b.toReal ↔ a ≤ b := by
lift a to ℝ≥0 using ha
lift b to ℝ≥0 using hb
norm_cast
#align ennreal.to_real_le_to_real ENNReal.toReal_le_toReal
@[gcongr]
theorem toReal_mono (hb : b ≠ ∞) (h : a ≤ b) : a.toReal ≤ b.toReal :=
(toReal_le_toReal (ne_top_of_le_ne_top hb h) hb).2 h
#align ennreal.to_real_mono ENNReal.toReal_mono
-- Porting note (#10756): new lemma
theorem toReal_mono' (h : a ≤ b) (ht : b = ∞ → a = ∞) : a.toReal ≤ b.toReal := by
rcases eq_or_ne a ∞ with rfl | ha
· exact toReal_nonneg
· exact toReal_mono (mt ht ha) h
@[simp]
| Mathlib/Data/ENNReal/Real.lean | 94 | 97 | theorem toReal_lt_toReal (ha : a ≠ ∞) (hb : b ≠ ∞) : a.toReal < b.toReal ↔ a < b := by |
lift a to ℝ≥0 using ha
lift b to ℝ≥0 using hb
norm_cast
|
/-
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.LinearAlgebra.CliffordAlgebra.Conjugation
import Mathlib.LinearAlgebra.CliffordAlgebra.Even
import Mathlib.LinearAlgebra.QuadraticForm.Prod
import Mathlib.Tactic.LiftLets
#align_import linear_algebra.clifford_algebra.even_equiv from "leanprover-community/mathlib"@"2196ab363eb097c008d4497125e0dde23fb36db2"
/-!
# Isomorphisms with the even subalgebra of a Clifford algebra
This file provides some notable isomorphisms regarding the even subalgebra, `CliffordAlgebra.even`.
## Main definitions
* `CliffordAlgebra.equivEven`: Every Clifford algebra is isomorphic as an algebra to the even
subalgebra of a Clifford algebra with one more dimension.
* `CliffordAlgebra.EquivEven.Q'`: The quadratic form used by this "one-up" algebra.
* `CliffordAlgebra.toEven`: The simp-normal form of the forward direction of this isomorphism.
* `CliffordAlgebra.ofEven`: The simp-normal form of the reverse direction of this isomorphism.
* `CliffordAlgebra.evenEquivEvenNeg`: Every even subalgebra is isomorphic to the even subalgebra
of the Clifford algebra with negated quadratic form.
* `CliffordAlgebra.evenToNeg`: The simp-normal form of each direction of this isomorphism.
## Main results
* `CliffordAlgebra.coe_toEven_reverse_involute`: the behavior of `CliffordAlgebra.toEven` on the
"Clifford conjugate", that is `CliffordAlgebra.reverse` composed with
`CliffordAlgebra.involute`.
-/
namespace CliffordAlgebra
variable {R M : Type*} [CommRing R] [AddCommGroup M] [Module R M]
variable (Q : QuadraticForm R M)
/-! ### Constructions needed for `CliffordAlgebra.equivEven` -/
namespace EquivEven
/-- The quadratic form on the augmented vector space `M × R` sending `v + r•e0` to `Q v - r^2`. -/
abbrev Q' : QuadraticForm R (M × R) :=
Q.prod <| -@QuadraticForm.sq R _
set_option linter.uppercaseLean3 false in
#align clifford_algebra.equiv_even.Q' CliffordAlgebra.EquivEven.Q'
theorem Q'_apply (m : M × R) : Q' Q m = Q m.1 - m.2 * m.2 :=
(sub_eq_add_neg _ _).symm
set_option linter.uppercaseLean3 false in
#align clifford_algebra.equiv_even.Q'_apply CliffordAlgebra.EquivEven.Q'_apply
/-- The unit vector in the new dimension -/
def e0 : CliffordAlgebra (Q' Q) :=
ι (Q' Q) (0, 1)
#align clifford_algebra.equiv_even.e0 CliffordAlgebra.EquivEven.e0
/-- The embedding from the existing vector space -/
def v : M →ₗ[R] CliffordAlgebra (Q' Q) :=
ι (Q' Q) ∘ₗ LinearMap.inl _ _ _
#align clifford_algebra.equiv_even.v CliffordAlgebra.EquivEven.v
theorem ι_eq_v_add_smul_e0 (m : M) (r : R) : ι (Q' Q) (m, r) = v Q m + r • e0 Q := by
rw [e0, v, LinearMap.comp_apply, LinearMap.inl_apply, ← LinearMap.map_smul, Prod.smul_mk,
smul_zero, smul_eq_mul, mul_one, ← LinearMap.map_add, Prod.mk_add_mk, zero_add, add_zero]
#align clifford_algebra.equiv_even.ι_eq_v_add_smul_e0 CliffordAlgebra.EquivEven.ι_eq_v_add_smul_e0
theorem e0_mul_e0 : e0 Q * e0 Q = -1 :=
(ι_sq_scalar _ _).trans <| by simp
#align clifford_algebra.equiv_even.e0_mul_e0 CliffordAlgebra.EquivEven.e0_mul_e0
theorem v_sq_scalar (m : M) : v Q m * v Q m = algebraMap _ _ (Q m) :=
(ι_sq_scalar _ _).trans <| by simp
#align clifford_algebra.equiv_even.v_sq_scalar CliffordAlgebra.EquivEven.v_sq_scalar
| Mathlib/LinearAlgebra/CliffordAlgebra/EvenEquiv.lean | 82 | 86 | theorem neg_e0_mul_v (m : M) : -(e0 Q * v Q m) = v Q m * e0 Q := by |
refine neg_eq_of_add_eq_zero_right ((ι_mul_ι_add_swap _ _).trans ?_)
dsimp [QuadraticForm.polar]
simp only [add_zero, mul_zero, mul_one, zero_add, neg_zero, QuadraticForm.map_zero,
add_sub_cancel_right, sub_self, map_zero, zero_sub]
|
/-
Copyright (c) 2023 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov
-/
import Mathlib.Dynamics.BirkhoffSum.Basic
import Mathlib.Algebra.Module.Basic
/-!
# Birkhoff average
In this file we define `birkhoffAverage f g n x` to be
$$
\frac{1}{n}\sum_{k=0}^{n-1}g(f^{[k]}(x)),
$$
where `f : α → α` is a self-map on some type `α`,
`g : α → M` is a function from `α` to a module over a division semiring `R`,
and `R` is used to formalize division by `n` as `(n : R)⁻¹ • _`.
While we need an auxiliary division semiring `R` to define `birkhoffAverage`,
the definition does not depend on the choice of `R`,
see `birkhoffAverage_congr_ring`.
-/
open Finset
section birkhoffAverage
variable (R : Type*) {α M : Type*} [DivisionSemiring R] [AddCommMonoid M] [Module R M]
/-- The average value of `g` on the first `n` points of the orbit of `x` under `f`,
i.e. the Birkhoff sum `∑ k ∈ Finset.range n, g (f^[k] x)` divided by `n`.
This average appears in many ergodic theorems
which say that `(birkhoffAverage R f g · x)`
converges to the "space average" `⨍ x, g x ∂μ` as `n → ∞`.
We use an auxiliary `[DivisionSemiring R]` to define division by `n`.
However, the definition does not depend on the choice of `R`,
see `birkhoffAverage_congr_ring`. -/
def birkhoffAverage (f : α → α) (g : α → M) (n : ℕ) (x : α) : M := (n : R)⁻¹ • birkhoffSum f g n x
theorem birkhoffAverage_zero (f : α → α) (g : α → M) (x : α) :
birkhoffAverage R f g 0 x = 0 := by simp [birkhoffAverage]
@[simp] theorem birkhoffAverage_zero' (f : α → α) (g : α → M) : birkhoffAverage R f g 0 = 0 :=
funext <| birkhoffAverage_zero _ _ _
theorem birkhoffAverage_one (f : α → α) (g : α → M) (x : α) :
birkhoffAverage R f g 1 x = g x := by simp [birkhoffAverage]
@[simp]
theorem birkhoffAverage_one' (f : α → α) (g : α → M) : birkhoffAverage R f g 1 = g :=
funext <| birkhoffAverage_one R f g
| Mathlib/Dynamics/BirkhoffSum/Average.lean | 57 | 61 | theorem map_birkhoffAverage (S : Type*) {F N : Type*}
[DivisionSemiring S] [AddCommMonoid N] [Module S N] [FunLike F M N]
[AddMonoidHomClass F M N] (g' : F) (f : α → α) (g : α → M) (n : ℕ) (x : α) :
g' (birkhoffAverage R f g n x) = birkhoffAverage S f (g' ∘ g) n x := by |
simp only [birkhoffAverage, map_inv_natCast_smul g' R S, map_birkhoffSum]
|
/-
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]
| Mathlib/Topology/Order/DenselyOrdered.lean | 83 | 84 | 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]
|
/-
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.LinearAlgebra.Matrix.Charpoly.Coeff
import Mathlib.LinearAlgebra.Matrix.ToLin
#align_import linear_algebra.matrix.charpoly.linear_map from "leanprover-community/mathlib"@"62c0a4ef1441edb463095ea02a06e87f3dfe135c"
/-!
# Cayley-Hamilton theorem for f.g. modules.
Given a fixed finite spanning set `b : ι → M` of an `R`-module `M`, we say that a matrix `M`
represents an endomorphism `f : M →ₗ[R] M` if the matrix as an endomorphism of `ι → R` commutes
with `f` via the projection `(ι → R) →ₗ[R] M` given by `b`.
We show that every endomorphism has a matrix representation, and if `f.range ≤ I • ⊤` for some
ideal `I`, we may furthermore obtain a matrix representation whose entries fall in `I`.
This is used to conclude the Cayley-Hamilton theorem for f.g. modules over arbitrary rings.
-/
variable {ι : Type*} [Fintype ι]
variable {M : Type*} [AddCommGroup M] (R : Type*) [CommRing R] [Module R M] (I : Ideal R)
variable (b : ι → M) (hb : Submodule.span R (Set.range b) = ⊤)
open Polynomial Matrix
/-- The composition of a matrix (as an endomorphism of `ι → R`) with the projection
`(ι → R) →ₗ[R] M`. -/
def PiToModule.fromMatrix [DecidableEq ι] : Matrix ι ι R →ₗ[R] (ι → R) →ₗ[R] M :=
(LinearMap.llcomp R _ _ _ (Fintype.total R R b)).comp algEquivMatrix'.symm.toLinearMap
#align pi_to_module.from_matrix PiToModule.fromMatrix
theorem PiToModule.fromMatrix_apply [DecidableEq ι] (A : Matrix ι ι R) (w : ι → R) :
PiToModule.fromMatrix R b A w = Fintype.total R R b (A *ᵥ w) :=
rfl
#align pi_to_module.from_matrix_apply PiToModule.fromMatrix_apply
theorem PiToModule.fromMatrix_apply_single_one [DecidableEq ι] (A : Matrix ι ι R) (j : ι) :
PiToModule.fromMatrix R b A (Pi.single j 1) = ∑ i : ι, A i j • b i := by
rw [PiToModule.fromMatrix_apply, Fintype.total_apply, Matrix.mulVec_single]
simp_rw [mul_one]
#align pi_to_module.from_matrix_apply_single_one PiToModule.fromMatrix_apply_single_one
/-- The endomorphisms of `M` acts on `(ι → R) →ₗ[R] M`, and takes the projection
to a `(ι → R) →ₗ[R] M`. -/
def PiToModule.fromEnd : Module.End R M →ₗ[R] (ι → R) →ₗ[R] M :=
LinearMap.lcomp _ _ (Fintype.total R R b)
#align pi_to_module.from_End PiToModule.fromEnd
theorem PiToModule.fromEnd_apply (f : Module.End R M) (w : ι → R) :
PiToModule.fromEnd R b f w = f (Fintype.total R R b w) :=
rfl
#align pi_to_module.from_End_apply PiToModule.fromEnd_apply
theorem PiToModule.fromEnd_apply_single_one [DecidableEq ι] (f : Module.End R M) (i : ι) :
PiToModule.fromEnd R b f (Pi.single i 1) = f (b i) := by
rw [PiToModule.fromEnd_apply]
congr
convert Fintype.total_apply_single (S := R) R b i (1 : R)
rw [one_smul]
#align pi_to_module.from_End_apply_single_one PiToModule.fromEnd_apply_single_one
| Mathlib/LinearAlgebra/Matrix/Charpoly/LinearMap.lean | 68 | 75 | theorem PiToModule.fromEnd_injective (hb : Submodule.span R (Set.range b) = ⊤) :
Function.Injective (PiToModule.fromEnd R b) := by |
intro x y e
ext m
obtain ⟨m, rfl⟩ : m ∈ LinearMap.range (Fintype.total R R b) := by
rw [(Fintype.range_total R b).trans hb]
exact Submodule.mem_top
exact (LinearMap.congr_fun e m : _)
|
/-
Copyright (c) 2020 Kenny Lau. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kenny Lau, Wrenna Robson
-/
import Mathlib.Algebra.BigOperators.Group.Finset
import Mathlib.LinearAlgebra.Vandermonde
import Mathlib.RingTheory.Polynomial.Basic
#align_import linear_algebra.lagrange from "leanprover-community/mathlib"@"70fd9563a21e7b963887c9360bd29b2393e6225a"
/-!
# Lagrange interpolation
## Main definitions
* In everything that follows, `s : Finset ι` is a finite set of indexes, with `v : ι → F` an
indexing of the field over some type. We call the image of v on s the interpolation nodes,
though strictly unique nodes are only defined when v is injective on s.
* `Lagrange.basisDivisor x y`, with `x y : F`. These are the normalised irreducible factors of
the Lagrange basis polynomials. They evaluate to `1` at `x` and `0` at `y` when `x` and `y`
are distinct.
* `Lagrange.basis v i` with `i : ι`: the Lagrange basis polynomial that evaluates to `1` at `v i`
and `0` at `v j` for `i ≠ j`.
* `Lagrange.interpolate v r` where `r : ι → F` is a function from the fintype to the field: the
Lagrange interpolant that evaluates to `r i` at `x i` for all `i : ι`. The `r i` are the _values_
associated with the _nodes_`x i`.
-/
open Polynomial
section PolynomialDetermination
namespace Polynomial
variable {R : Type*} [CommRing R] [IsDomain R] {f g : R[X]}
section Finset
open Function Fintype
variable (s : Finset R)
theorem eq_zero_of_degree_lt_of_eval_finset_eq_zero (degree_f_lt : f.degree < s.card)
(eval_f : ∀ x ∈ s, f.eval x = 0) : f = 0 := by
rw [← mem_degreeLT] at degree_f_lt
simp_rw [eval_eq_sum_degreeLTEquiv degree_f_lt] at eval_f
rw [← degreeLTEquiv_eq_zero_iff_eq_zero degree_f_lt]
exact
Matrix.eq_zero_of_forall_index_sum_mul_pow_eq_zero
(Injective.comp (Embedding.subtype _).inj' (equivFinOfCardEq (card_coe _)).symm.injective)
fun _ => eval_f _ (Finset.coe_mem _)
#align polynomial.eq_zero_of_degree_lt_of_eval_finset_eq_zero Polynomial.eq_zero_of_degree_lt_of_eval_finset_eq_zero
theorem eq_of_degree_sub_lt_of_eval_finset_eq (degree_fg_lt : (f - g).degree < s.card)
(eval_fg : ∀ x ∈ s, f.eval x = g.eval x) : f = g := by
rw [← sub_eq_zero]
refine eq_zero_of_degree_lt_of_eval_finset_eq_zero _ degree_fg_lt ?_
simp_rw [eval_sub, sub_eq_zero]
exact eval_fg
#align polynomial.eq_of_degree_sub_lt_of_eval_finset_eq Polynomial.eq_of_degree_sub_lt_of_eval_finset_eq
| Mathlib/LinearAlgebra/Lagrange.lean | 63 | 67 | theorem eq_of_degrees_lt_of_eval_finset_eq (degree_f_lt : f.degree < s.card)
(degree_g_lt : g.degree < s.card) (eval_fg : ∀ x ∈ s, f.eval x = g.eval x) : f = g := by |
rw [← mem_degreeLT] at degree_f_lt degree_g_lt
refine eq_of_degree_sub_lt_of_eval_finset_eq _ ?_ eval_fg
rw [← mem_degreeLT]; exact Submodule.sub_mem _ degree_f_lt degree_g_lt
|
/-
Copyright (c) 2022 Kalle Kytölä. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kalle Kytölä
-/
import Mathlib.Data.ENNReal.Basic
import Mathlib.Topology.ContinuousFunction.Bounded
import Mathlib.Topology.MetricSpace.Thickening
#align_import topology.metric_space.thickened_indicator from "leanprover-community/mathlib"@"f2ce6086713c78a7f880485f7917ea547a215982"
/-!
# Thickened indicators
This file is about thickened indicators of sets in (pseudo e)metric spaces. For a decreasing
sequence of thickening radii tending to 0, the thickened indicators of a closed set form a
decreasing pointwise converging approximation of the indicator function of the set, where the
members of the approximating sequence are nonnegative bounded continuous functions.
## Main definitions
* `thickenedIndicatorAux δ E`: The `δ`-thickened indicator of a set `E` as an
unbundled `ℝ≥0∞`-valued function.
* `thickenedIndicator δ E`: The `δ`-thickened indicator of a set `E` as a bundled
bounded continuous `ℝ≥0`-valued function.
## Main results
* For a sequence of thickening radii tending to 0, the `δ`-thickened indicators of a set `E` tend
pointwise to the indicator of `closure E`.
- `thickenedIndicatorAux_tendsto_indicator_closure`: The version is for the
unbundled `ℝ≥0∞`-valued functions.
- `thickenedIndicator_tendsto_indicator_closure`: The version is for the bundled `ℝ≥0`-valued
bounded continuous functions.
-/
open scoped Classical
open NNReal ENNReal Topology BoundedContinuousFunction
open NNReal ENNReal Set Metric EMetric Filter
noncomputable section thickenedIndicator
variable {α : Type*} [PseudoEMetricSpace α]
/-- The `δ`-thickened indicator of a set `E` is the function that equals `1` on `E`
and `0` outside a `δ`-thickening of `E` and interpolates (continuously) between
these values using `infEdist _ E`.
`thickenedIndicatorAux` is the unbundled `ℝ≥0∞`-valued function. See `thickenedIndicator`
for the (bundled) bounded continuous function with `ℝ≥0`-values. -/
def thickenedIndicatorAux (δ : ℝ) (E : Set α) : α → ℝ≥0∞ :=
fun x : α => (1 : ℝ≥0∞) - infEdist x E / ENNReal.ofReal δ
#align thickened_indicator_aux thickenedIndicatorAux
theorem continuous_thickenedIndicatorAux {δ : ℝ} (δ_pos : 0 < δ) (E : Set α) :
Continuous (thickenedIndicatorAux δ E) := by
unfold thickenedIndicatorAux
let f := fun x : α => (⟨1, infEdist x E / ENNReal.ofReal δ⟩ : ℝ≥0 × ℝ≥0∞)
let sub := fun p : ℝ≥0 × ℝ≥0∞ => (p.1 : ℝ≥0∞) - p.2
rw [show (fun x : α => (1 : ℝ≥0∞) - infEdist x E / ENNReal.ofReal δ) = sub ∘ f by rfl]
apply (@ENNReal.continuous_nnreal_sub 1).comp
apply (ENNReal.continuous_div_const (ENNReal.ofReal δ) _).comp continuous_infEdist
set_option tactic.skipAssignedInstances false in norm_num [δ_pos]
#align continuous_thickened_indicator_aux continuous_thickenedIndicatorAux
theorem thickenedIndicatorAux_le_one (δ : ℝ) (E : Set α) (x : α) :
thickenedIndicatorAux δ E x ≤ 1 := by
apply @tsub_le_self _ _ _ _ (1 : ℝ≥0∞)
#align thickened_indicator_aux_le_one thickenedIndicatorAux_le_one
theorem thickenedIndicatorAux_lt_top {δ : ℝ} {E : Set α} {x : α} :
thickenedIndicatorAux δ E x < ∞ :=
lt_of_le_of_lt (thickenedIndicatorAux_le_one _ _ _) one_lt_top
#align thickened_indicator_aux_lt_top thickenedIndicatorAux_lt_top
theorem thickenedIndicatorAux_closure_eq (δ : ℝ) (E : Set α) :
thickenedIndicatorAux δ (closure E) = thickenedIndicatorAux δ E := by
simp (config := { unfoldPartialApp := true }) only [thickenedIndicatorAux, infEdist_closure]
#align thickened_indicator_aux_closure_eq thickenedIndicatorAux_closure_eq
theorem thickenedIndicatorAux_one (δ : ℝ) (E : Set α) {x : α} (x_in_E : x ∈ E) :
thickenedIndicatorAux δ E x = 1 := by
simp [thickenedIndicatorAux, infEdist_zero_of_mem x_in_E, tsub_zero]
#align thickened_indicator_aux_one thickenedIndicatorAux_one
theorem thickenedIndicatorAux_one_of_mem_closure (δ : ℝ) (E : Set α) {x : α}
(x_mem : x ∈ closure E) : thickenedIndicatorAux δ E x = 1 := by
rw [← thickenedIndicatorAux_closure_eq, thickenedIndicatorAux_one δ (closure E) x_mem]
#align thickened_indicator_aux_one_of_mem_closure thickenedIndicatorAux_one_of_mem_closure
theorem thickenedIndicatorAux_zero {δ : ℝ} (δ_pos : 0 < δ) (E : Set α) {x : α}
(x_out : x ∉ thickening δ E) : thickenedIndicatorAux δ E x = 0 := by
rw [thickening, mem_setOf_eq, not_lt] at x_out
unfold thickenedIndicatorAux
apply le_antisymm _ bot_le
have key := tsub_le_tsub
(@rfl _ (1 : ℝ≥0∞)).le (ENNReal.div_le_div x_out (@rfl _ (ENNReal.ofReal δ : ℝ≥0∞)).le)
rw [ENNReal.div_self (ne_of_gt (ENNReal.ofReal_pos.mpr δ_pos)) ofReal_ne_top] at key
simpa using key
#align thickened_indicator_aux_zero thickenedIndicatorAux_zero
theorem thickenedIndicatorAux_mono {δ₁ δ₂ : ℝ} (hle : δ₁ ≤ δ₂) (E : Set α) :
thickenedIndicatorAux δ₁ E ≤ thickenedIndicatorAux δ₂ E :=
fun _ => tsub_le_tsub (@rfl ℝ≥0∞ 1).le (ENNReal.div_le_div rfl.le (ofReal_le_ofReal hle))
#align thickened_indicator_aux_mono thickenedIndicatorAux_mono
| Mathlib/Topology/MetricSpace/ThickenedIndicator.lean | 110 | 115 | theorem indicator_le_thickenedIndicatorAux (δ : ℝ) (E : Set α) :
(E.indicator fun _ => (1 : ℝ≥0∞)) ≤ thickenedIndicatorAux δ E := by |
intro a
by_cases h : a ∈ E
· simp only [h, indicator_of_mem, thickenedIndicatorAux_one δ E h, le_refl]
· simp only [h, indicator_of_not_mem, not_false_iff, zero_le]
|
/-
Copyright (c) 2021 Andrew Yang. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Andrew Yang
-/
import Mathlib.CategoryTheory.Sites.DenseSubsite
#align_import category_theory.sites.induced_topology from "leanprover-community/mathlib"@"ba43124c37cfe0009bbfc57505f9503ae0e8c1af"
/-!
# Induced Topology
We say that a functor `G : C ⥤ (D, K)` is locally dense if for each covering sieve `T` in `D` of
some `X : C`, `T ∩ mor(C)` generates a covering sieve of `X` in `D`. A locally dense fully faithful
functor then induces a topology on `C` via `{ T ∩ mor(C) | T ∈ K }`. Note that this is equal to
the collection of sieves on `C` whose image generates a covering sieve. This construction would
make `C` both cover-lifting and cover-preserving.
Some typical examples are full and cover-dense functors (for example the functor from a basis of a
topological space `X` into `Opens X`). The functor `Over X ⥤ C` is also locally dense, and the
induced topology can then be used to construct the big sites associated to a scheme.
Given a fully faithful cover-dense functor `G : C ⥤ (D, K)` between small sites, we then have
`Sheaf (H.inducedTopology) A ≌ Sheaf K A`. This is known as the comparison lemma.
## References
* [Elephant]: *Sketches of an Elephant*, P. T. Johnstone: C2.2.
* https://ncatlab.org/nlab/show/dense+sub-site
* https://ncatlab.org/nlab/show/comparison+lemma
-/
namespace CategoryTheory
universe v u
open Limits Opposite Presieve
section
variable {C : Type*} [Category C] {D : Type*} [Category D] {G : C ⥤ D}
variable {J : GrothendieckTopology C} {K : GrothendieckTopology D}
variable (A : Type v) [Category.{u} A]
-- variables (A) [full G] [faithful G]
/-- We say that a functor `C ⥤ D` into a site is "locally dense" if
for each covering sieve `T` in `D`, `T ∩ mor(C)` generates a covering sieve in `D`.
-/
def LocallyCoverDense (K : GrothendieckTopology D) (G : C ⥤ D) : Prop :=
∀ ⦃X : C⦄ (T : K (G.obj X)), (T.val.functorPullback G).functorPushforward G ∈ K (G.obj X)
#align category_theory.locally_cover_dense CategoryTheory.LocallyCoverDense
namespace LocallyCoverDense
variable [G.Full] [G.Faithful] (Hld : LocallyCoverDense K G)
| Mathlib/CategoryTheory/Sites/InducedTopology.lean | 59 | 65 | theorem pushforward_cover_iff_cover_pullback {X : C} (S : Sieve X) :
K _ (S.functorPushforward G) ↔ ∃ T : K (G.obj X), T.val.functorPullback G = S := by |
constructor
· intro hS
exact ⟨⟨_, hS⟩, (Sieve.fullyFaithfulFunctorGaloisCoinsertion G X).u_l_eq S⟩
· rintro ⟨T, rfl⟩
exact Hld T
|
/-
Copyright (c) 2023 Josha Dekker. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Josha Dekker
-/
import Mathlib.Topology.Bases
import Mathlib.Order.Filter.CountableInter
import Mathlib.Topology.Compactness.SigmaCompact
/-!
# Lindelöf sets and Lindelöf spaces
## Main definitions
We define the following properties for sets in a topological space:
* `IsLindelof s`: Two definitions are possible here. The more standard definition is that
every open cover that contains `s` contains a countable subcover. We choose for the equivalent
definition where we require that every nontrivial filter on `s` with the countable intersection
property has a clusterpoint. Equivalence is established in `isLindelof_iff_countable_subcover`.
* `LindelofSpace X`: `X` is Lindelöf if it is Lindelöf as a set.
* `NonLindelofSpace`: a space that is not a Lindëlof space, e.g. the Long Line.
## Main results
* `isLindelof_iff_countable_subcover`: A set is Lindelöf iff every open cover has a
countable subcover.
## Implementation details
* This API is mainly based on the API for IsCompact and follows notation and style as much
as possible.
-/
open Set Filter Topology TopologicalSpace
universe u v
variable {X : Type u} {Y : Type v} {ι : Type*}
variable [TopologicalSpace X] [TopologicalSpace Y] {s t : Set X}
section Lindelof
/-- A set `s` is Lindelöf if every nontrivial filter `f` with the countable intersection
property that contains `s`, has a clusterpoint in `s`. The filter-free definition is given by
`isLindelof_iff_countable_subcover`. -/
def IsLindelof (s : Set X) :=
∀ ⦃f⦄ [NeBot f] [CountableInterFilter f], f ≤ 𝓟 s → ∃ x ∈ s, ClusterPt x f
/-- The complement to a Lindelöf set belongs to a filter `f` with the countable intersection
property if it belongs to each filter `𝓝 x ⊓ f`, `x ∈ s`. -/
theorem IsLindelof.compl_mem_sets (hs : IsLindelof s) {f : Filter X} [CountableInterFilter f]
(hf : ∀ x ∈ s, sᶜ ∈ 𝓝 x ⊓ f) : sᶜ ∈ f := by
contrapose! hf
simp only [not_mem_iff_inf_principal_compl, compl_compl, inf_assoc] at hf ⊢
exact hs inf_le_right
/-- The complement to a Lindelöf set belongs to a filter `f` with the countable intersection
property if each `x ∈ s` has a neighborhood `t` within `s` such that `tᶜ` belongs to `f`. -/
| Mathlib/Topology/Compactness/Lindelof.lean | 60 | 64 | theorem IsLindelof.compl_mem_sets_of_nhdsWithin (hs : IsLindelof s) {f : Filter X}
[CountableInterFilter f] (hf : ∀ x ∈ s, ∃ t ∈ 𝓝[s] x, tᶜ ∈ f) : sᶜ ∈ f := by |
refine hs.compl_mem_sets fun x hx ↦ ?_
rw [← disjoint_principal_right, disjoint_right_comm, (basis_sets _).disjoint_iff_left]
exact hf x hx
|
/-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Aaron Anderson, Yakov Pechersky
-/
import Mathlib.Algebra.Group.Commute.Basic
import Mathlib.Data.Fintype.Card
import Mathlib.GroupTheory.Perm.Basic
#align_import group_theory.perm.support from "leanprover-community/mathlib"@"9003f28797c0664a49e4179487267c494477d853"
/-!
# support of a permutation
## Main definitions
In the following, `f g : Equiv.Perm α`.
* `Equiv.Perm.Disjoint`: two permutations `f` and `g` are `Disjoint` if every element is fixed
either by `f`, or by `g`.
Equivalently, `f` and `g` are `Disjoint` iff their `support` are disjoint.
* `Equiv.Perm.IsSwap`: `f = swap x y` for `x ≠ y`.
* `Equiv.Perm.support`: the elements `x : α` that are not fixed by `f`.
Assume `α` is a Fintype:
* `Equiv.Perm.fixed_point_card_lt_of_ne_one f` says that `f` has
strictly less than `Fintype.card α - 1` fixed points, unless `f = 1`.
(Equivalently, `f.support` has at least 2 elements.)
-/
open Equiv Finset
namespace Equiv.Perm
variable {α : Type*}
section Disjoint
/-- Two permutations `f` and `g` are `Disjoint` if their supports are disjoint, i.e.,
every element is fixed either by `f`, or by `g`. -/
def Disjoint (f g : Perm α) :=
∀ x, f x = x ∨ g x = x
#align equiv.perm.disjoint Equiv.Perm.Disjoint
variable {f g h : Perm α}
@[symm]
theorem Disjoint.symm : Disjoint f g → Disjoint g f := by simp only [Disjoint, or_comm, imp_self]
#align equiv.perm.disjoint.symm Equiv.Perm.Disjoint.symm
theorem Disjoint.symmetric : Symmetric (@Disjoint α) := fun _ _ => Disjoint.symm
#align equiv.perm.disjoint.symmetric Equiv.Perm.Disjoint.symmetric
instance : IsSymm (Perm α) Disjoint :=
⟨Disjoint.symmetric⟩
theorem disjoint_comm : Disjoint f g ↔ Disjoint g f :=
⟨Disjoint.symm, Disjoint.symm⟩
#align equiv.perm.disjoint_comm Equiv.Perm.disjoint_comm
theorem Disjoint.commute (h : Disjoint f g) : Commute f g :=
Equiv.ext fun x =>
(h x).elim
(fun hf =>
(h (g x)).elim (fun hg => by simp [mul_apply, hf, hg]) fun hg => by
simp [mul_apply, hf, g.injective hg])
fun hg =>
(h (f x)).elim (fun hf => by simp [mul_apply, f.injective hf, hg]) fun hf => by
simp [mul_apply, hf, hg]
#align equiv.perm.disjoint.commute Equiv.Perm.Disjoint.commute
@[simp]
theorem disjoint_one_left (f : Perm α) : Disjoint 1 f := fun _ => Or.inl rfl
#align equiv.perm.disjoint_one_left Equiv.Perm.disjoint_one_left
@[simp]
theorem disjoint_one_right (f : Perm α) : Disjoint f 1 := fun _ => Or.inr rfl
#align equiv.perm.disjoint_one_right Equiv.Perm.disjoint_one_right
theorem disjoint_iff_eq_or_eq : Disjoint f g ↔ ∀ x : α, f x = x ∨ g x = x :=
Iff.rfl
#align equiv.perm.disjoint_iff_eq_or_eq Equiv.Perm.disjoint_iff_eq_or_eq
@[simp]
theorem disjoint_refl_iff : Disjoint f f ↔ f = 1 := by
refine ⟨fun h => ?_, fun h => h.symm ▸ disjoint_one_left 1⟩
ext x
cases' h x with hx hx <;> simp [hx]
#align equiv.perm.disjoint_refl_iff Equiv.Perm.disjoint_refl_iff
theorem Disjoint.inv_left (h : Disjoint f g) : Disjoint f⁻¹ g := by
intro x
rw [inv_eq_iff_eq, eq_comm]
exact h x
#align equiv.perm.disjoint.inv_left Equiv.Perm.Disjoint.inv_left
theorem Disjoint.inv_right (h : Disjoint f g) : Disjoint f g⁻¹ :=
h.symm.inv_left.symm
#align equiv.perm.disjoint.inv_right Equiv.Perm.Disjoint.inv_right
@[simp]
theorem disjoint_inv_left_iff : Disjoint f⁻¹ g ↔ Disjoint f g := by
refine ⟨fun h => ?_, Disjoint.inv_left⟩
convert h.inv_left
#align equiv.perm.disjoint_inv_left_iff Equiv.Perm.disjoint_inv_left_iff
@[simp]
| Mathlib/GroupTheory/Perm/Support.lean | 110 | 111 | theorem disjoint_inv_right_iff : Disjoint f g⁻¹ ↔ Disjoint f g := by |
rw [disjoint_comm, disjoint_inv_left_iff, disjoint_comm]
|
/-
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]
| Mathlib/RingTheory/LaurentSeries.lean | 87 | 89 | 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]
|
/-
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, Patrick Massot
-/
import Mathlib.Data.Set.Function
import Mathlib.Order.Interval.Set.OrdConnected
#align_import data.set.intervals.proj_Icc from "leanprover-community/mathlib"@"4e24c4bfcff371c71f7ba22050308aa17815626c"
/-!
# Projection of a line onto a closed interval
Given a linearly ordered type `α`, in this file we define
* `Set.projIci (a : α)` to be the map `α → [a, ∞)` sending `(-∞, a]` to `a`, and each point
`x ∈ [a, ∞)` to itself;
* `Set.projIic (b : α)` to be the map `α → (-∞, b[` sending `[b, ∞)` to `b`, and each point
`x ∈ (-∞, b]` to itself;
* `Set.projIcc (a b : α) (h : a ≤ b)` to be the map `α → [a, b]` sending `(-∞, a]` to `a`, `[b, ∞)`
to `b`, and each point `x ∈ [a, b]` to itself;
* `Set.IccExtend {a b : α} (h : a ≤ b) (f : Icc a b → β)` to be the extension of `f` to `α` defined
as `f ∘ projIcc a b h`.
* `Set.IciExtend {a : α} (f : Ici a → β)` to be the extension of `f` to `α` defined
as `f ∘ projIci a`.
* `Set.IicExtend {b : α} (f : Iic b → β)` to be the extension of `f` to `α` defined
as `f ∘ projIic b`.
We also prove some trivial properties of these maps.
-/
variable {α β : Type*} [LinearOrder α]
open Function
namespace Set
/-- Projection of `α` to the closed interval `[a, ∞)`. -/
def projIci (a x : α) : Ici a := ⟨max a x, le_max_left _ _⟩
#align set.proj_Ici Set.projIci
/-- Projection of `α` to the closed interval `(-∞, b]`. -/
def projIic (b x : α) : Iic b := ⟨min b x, min_le_left _ _⟩
#align set.proj_Iic Set.projIic
/-- Projection of `α` to the closed interval `[a, b]`. -/
def projIcc (a b : α) (h : a ≤ b) (x : α) : Icc a b :=
⟨max a (min b x), le_max_left _ _, max_le h (min_le_left _ _)⟩
#align set.proj_Icc Set.projIcc
variable {a b : α} (h : a ≤ b) {x : α}
@[norm_cast]
theorem coe_projIci (a x : α) : (projIci a x : α) = max a x := rfl
#align set.coe_proj_Ici Set.coe_projIci
@[norm_cast]
theorem coe_projIic (b x : α) : (projIic b x : α) = min b x := rfl
#align set.coe_proj_Iic Set.coe_projIic
@[norm_cast]
theorem coe_projIcc (a b : α) (h : a ≤ b) (x : α) : (projIcc a b h x : α) = max a (min b x) := rfl
#align set.coe_proj_Icc Set.coe_projIcc
theorem projIci_of_le (hx : x ≤ a) : projIci a x = ⟨a, le_rfl⟩ := Subtype.ext <| max_eq_left hx
#align set.proj_Ici_of_le Set.projIci_of_le
theorem projIic_of_le (hx : b ≤ x) : projIic b x = ⟨b, le_rfl⟩ := Subtype.ext <| min_eq_left hx
#align set.proj_Iic_of_le Set.projIic_of_le
theorem projIcc_of_le_left (hx : x ≤ a) : projIcc a b h x = ⟨a, left_mem_Icc.2 h⟩ := by
simp [projIcc, hx, hx.trans h]
#align set.proj_Icc_of_le_left Set.projIcc_of_le_left
| Mathlib/Order/Interval/Set/ProjIcc.lean | 77 | 78 | theorem projIcc_of_right_le (hx : b ≤ x) : projIcc a b h x = ⟨b, right_mem_Icc.2 h⟩ := by |
simp [projIcc, hx, h]
|
/-
Copyright (c) 2018 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad
-/
import Mathlib.Order.Filter.Partial
import Mathlib.Topology.Basic
#align_import topology.partial from "leanprover-community/mathlib"@"4c19a16e4b705bf135cf9a80ac18fcc99c438514"
/-!
# Partial functions and topological spaces
In this file we prove properties of `Filter.PTendsto` etc in topological spaces. We also introduce
`PContinuous`, a version of `Continuous` for partially defined functions.
-/
open Filter
open Topology
variable {X Y : Type*} [TopologicalSpace X]
theorem rtendsto_nhds {r : Rel Y X} {l : Filter Y} {x : X} :
RTendsto r l (𝓝 x) ↔ ∀ s, IsOpen s → x ∈ s → r.core s ∈ l :=
all_mem_nhds_filter _ _ (fun _s _t => id) _
#align rtendsto_nhds rtendsto_nhds
| Mathlib/Topology/Partial.lean | 30 | 34 | theorem rtendsto'_nhds {r : Rel Y X} {l : Filter Y} {x : X} :
RTendsto' r l (𝓝 x) ↔ ∀ s, IsOpen s → x ∈ s → r.preimage s ∈ l := by |
rw [rtendsto'_def]
apply all_mem_nhds_filter
apply Rel.preimage_mono
|
/-
Copyright (c) 2019 Scott Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Scott Morrison, Simon Hudon
-/
import Mathlib.CategoryTheory.Monoidal.Braided.Basic
import Mathlib.CategoryTheory.Monoidal.OfChosenFiniteProducts.Basic
#align_import category_theory.monoidal.of_chosen_finite_products.symmetric from "leanprover-community/mathlib"@"95a87616d63b3cb49d3fe678d416fbe9c4217bf4"
/-!
# The symmetric monoidal structure on a category with chosen finite products.
-/
universe v u
namespace CategoryTheory
variable {C : Type u} [Category.{v} C] {X Y : C}
open CategoryTheory.Limits
variable (𝒯 : LimitCone (Functor.empty.{0} C))
variable (ℬ : ∀ X Y : C, LimitCone (pair X Y))
open MonoidalOfChosenFiniteProducts
namespace MonoidalOfChosenFiniteProducts
open MonoidalCategory
| Mathlib/CategoryTheory/Monoidal/OfChosenFiniteProducts/Symmetric.lean | 34 | 39 | theorem braiding_naturality {X X' Y Y' : C} (f : X ⟶ Y) (g : X' ⟶ Y') :
tensorHom ℬ f g ≫ (Limits.BinaryFan.braiding (ℬ Y Y').isLimit (ℬ Y' Y).isLimit).hom =
(Limits.BinaryFan.braiding (ℬ X X').isLimit (ℬ X' X).isLimit).hom ≫ tensorHom ℬ g f := by |
dsimp [tensorHom, Limits.BinaryFan.braiding]
apply (ℬ _ _).isLimit.hom_ext
rintro ⟨⟨⟩⟩ <;> · dsimp [Limits.IsLimit.conePointUniqueUpToIso]; simp
|
/-
Copyright (c) 2022 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov
-/
import Mathlib.Analysis.Complex.UpperHalfPlane.Topology
import Mathlib.Analysis.SpecialFunctions.Arsinh
import Mathlib.Geometry.Euclidean.Inversion.Basic
#align_import analysis.complex.upper_half_plane.metric from "leanprover-community/mathlib"@"caa58cbf5bfb7f81ccbaca4e8b8ac4bc2b39cc1c"
/-!
# Metric on the upper half-plane
In this file we define a `MetricSpace` structure on the `UpperHalfPlane`. We use hyperbolic
(Poincaré) distance given by
`dist z w = 2 * arsinh (dist (z : ℂ) w / (2 * √(z.im * w.im)))` instead of the induced
Euclidean distance because the hyperbolic distance is invariant under holomorphic automorphisms of
the upper half-plane. However, we ensure that the projection to `TopologicalSpace` is
definitionally equal to the induced topological space structure.
We also prove that a metric ball/closed ball/sphere in Poincaré metric is a Euclidean ball/closed
ball/sphere with another center and radius.
-/
noncomputable section
open scoped UpperHalfPlane ComplexConjugate NNReal Topology MatrixGroups
open Set Metric Filter Real
variable {z w : ℍ} {r R : ℝ}
namespace UpperHalfPlane
instance : Dist ℍ :=
⟨fun z w => 2 * arsinh (dist (z : ℂ) w / (2 * √(z.im * w.im)))⟩
theorem dist_eq (z w : ℍ) : dist z w = 2 * arsinh (dist (z : ℂ) w / (2 * √(z.im * w.im))) :=
rfl
#align upper_half_plane.dist_eq UpperHalfPlane.dist_eq
theorem sinh_half_dist (z w : ℍ) :
sinh (dist z w / 2) = dist (z : ℂ) w / (2 * √(z.im * w.im)) := by
rw [dist_eq, mul_div_cancel_left₀ (arsinh _) two_ne_zero, sinh_arsinh]
#align upper_half_plane.sinh_half_dist UpperHalfPlane.sinh_half_dist
theorem cosh_half_dist (z w : ℍ) :
cosh (dist z w / 2) = dist (z : ℂ) (conj (w : ℂ)) / (2 * √(z.im * w.im)) := by
rw [← sq_eq_sq, cosh_sq', sinh_half_dist, div_pow, div_pow, one_add_div, mul_pow, sq_sqrt]
· congr 1
simp only [Complex.dist_eq, Complex.sq_abs, Complex.normSq_sub, Complex.normSq_conj,
Complex.conj_conj, Complex.mul_re, Complex.conj_re, Complex.conj_im, coe_im]
ring
all_goals positivity
#align upper_half_plane.cosh_half_dist UpperHalfPlane.cosh_half_dist
| Mathlib/Analysis/Complex/UpperHalfPlane/Metric.lean | 60 | 63 | theorem tanh_half_dist (z w : ℍ) :
tanh (dist z w / 2) = dist (z : ℂ) w / dist (z : ℂ) (conj ↑w) := by |
rw [tanh_eq_sinh_div_cosh, sinh_half_dist, cosh_half_dist, div_div_div_comm, div_self, div_one]
positivity
|
/-
Copyright (c) 2014 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad, Leonardo de Moura
-/
import Mathlib.Algebra.GroupWithZero.Divisibility
import Mathlib.Algebra.Order.Ring.Nat
import Mathlib.Tactic.NthRewrite
#align_import data.nat.gcd.basic from "leanprover-community/mathlib"@"e8638a0fcaf73e4500469f368ef9494e495099b3"
/-!
# Definitions and properties of `Nat.gcd`, `Nat.lcm`, and `Nat.coprime`
Generalizations of these are provided in a later file as `GCDMonoid.gcd` and
`GCDMonoid.lcm`.
Note that the global `IsCoprime` is not a straightforward generalization of `Nat.coprime`, see
`Nat.isCoprime_iff_coprime` for the connection between the two.
-/
namespace Nat
/-! ### `gcd` -/
theorem gcd_greatest {a b d : ℕ} (hda : d ∣ a) (hdb : d ∣ b) (hd : ∀ e : ℕ, e ∣ a → e ∣ b → e ∣ d) :
d = a.gcd b :=
(dvd_antisymm (hd _ (gcd_dvd_left a b) (gcd_dvd_right a b)) (dvd_gcd hda hdb)).symm
#align nat.gcd_greatest Nat.gcd_greatest
/-! Lemmas where one argument consists of addition of a multiple of the other -/
@[simp]
theorem gcd_add_mul_right_right (m n k : ℕ) : gcd m (n + k * m) = gcd m n := by
simp [gcd_rec m (n + k * m), gcd_rec m n]
#align nat.gcd_add_mul_right_right Nat.gcd_add_mul_right_right
@[simp]
theorem gcd_add_mul_left_right (m n k : ℕ) : gcd m (n + m * k) = gcd m n := by
simp [gcd_rec m (n + m * k), gcd_rec m n]
#align nat.gcd_add_mul_left_right Nat.gcd_add_mul_left_right
@[simp]
theorem gcd_mul_right_add_right (m n k : ℕ) : gcd m (k * m + n) = gcd m n := by simp [add_comm _ n]
#align nat.gcd_mul_right_add_right Nat.gcd_mul_right_add_right
@[simp]
theorem gcd_mul_left_add_right (m n k : ℕ) : gcd m (m * k + n) = gcd m n := by simp [add_comm _ n]
#align nat.gcd_mul_left_add_right Nat.gcd_mul_left_add_right
@[simp]
theorem gcd_add_mul_right_left (m n k : ℕ) : gcd (m + k * n) n = gcd m n := by
rw [gcd_comm, gcd_add_mul_right_right, gcd_comm]
#align nat.gcd_add_mul_right_left Nat.gcd_add_mul_right_left
@[simp]
theorem gcd_add_mul_left_left (m n k : ℕ) : gcd (m + n * k) n = gcd m n := by
rw [gcd_comm, gcd_add_mul_left_right, gcd_comm]
#align nat.gcd_add_mul_left_left Nat.gcd_add_mul_left_left
@[simp]
theorem gcd_mul_right_add_left (m n k : ℕ) : gcd (k * n + m) n = gcd m n := by
rw [gcd_comm, gcd_mul_right_add_right, gcd_comm]
#align nat.gcd_mul_right_add_left Nat.gcd_mul_right_add_left
@[simp]
theorem gcd_mul_left_add_left (m n k : ℕ) : gcd (n * k + m) n = gcd m n := by
rw [gcd_comm, gcd_mul_left_add_right, gcd_comm]
#align nat.gcd_mul_left_add_left Nat.gcd_mul_left_add_left
/-! Lemmas where one argument consists of an addition of the other -/
@[simp]
theorem gcd_add_self_right (m n : ℕ) : gcd m (n + m) = gcd m n :=
Eq.trans (by rw [one_mul]) (gcd_add_mul_right_right m n 1)
#align nat.gcd_add_self_right Nat.gcd_add_self_right
@[simp]
theorem gcd_add_self_left (m n : ℕ) : gcd (m + n) n = gcd m n := by
rw [gcd_comm, gcd_add_self_right, gcd_comm]
#align nat.gcd_add_self_left Nat.gcd_add_self_left
@[simp]
theorem gcd_self_add_left (m n : ℕ) : gcd (m + n) m = gcd n m := by rw [add_comm, gcd_add_self_left]
#align nat.gcd_self_add_left Nat.gcd_self_add_left
@[simp]
theorem gcd_self_add_right (m n : ℕ) : gcd m (m + n) = gcd m n := by
rw [add_comm, gcd_add_self_right]
#align nat.gcd_self_add_right Nat.gcd_self_add_right
/-! Lemmas where one argument consists of a subtraction of the other -/
@[simp]
| Mathlib/Data/Nat/GCD/Basic.lean | 96 | 99 | theorem gcd_sub_self_left {m n : ℕ} (h : m ≤ n) : gcd (n - m) m = gcd n m := by |
calc
gcd (n - m) m = gcd (n - m + m) m := by rw [← gcd_add_self_left (n - m) m]
_ = gcd n m := by rw [Nat.sub_add_cancel h]
|
/-
Copyright (c) 2024 Xavier Roblot. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Xavier Roblot
-/
import Mathlib.RingTheory.FractionalIdeal.Basic
import Mathlib.RingTheory.Ideal.Norm
/-!
# Fractional ideal norms
This file defines the absolute ideal norm of a fractional ideal `I : FractionalIdeal R⁰ K` where
`K` is a fraction field of `R`. The norm is defined by
`FractionalIdeal.absNorm I = Ideal.absNorm I.num / |Algebra.norm ℤ I.den|` where `I.num` is an
ideal of `R` and `I.den` an element of `R⁰` such that `I.den • I = I.num`.
## Main definitions and results
* `FractionalIdeal.absNorm`: the norm as a zero preserving morphism with values in `ℚ`.
* `FractionalIdeal.absNorm_eq'`: the value of the norm does not depend on the choice of
`I.num` and `I.den`.
* `FractionalIdeal.abs_det_basis_change`: the norm is given by the determinant
of the basis change matrix.
* `FractionalIdeal.absNorm_span_singleton`: the norm of a principal fractional ideal is the
norm of its generator
-/
namespace FractionalIdeal
open scoped Pointwise nonZeroDivisors
variable {R : Type*} [CommRing R] [IsDedekindDomain R] [Module.Free ℤ R] [Module.Finite ℤ R]
variable {K : Type*} [CommRing K] [Algebra R K] [IsFractionRing R K]
theorem absNorm_div_norm_eq_absNorm_div_norm {I : FractionalIdeal R⁰ K} (a : R⁰) (I₀ : Ideal R)
(h : a • (I : Submodule R K) = Submodule.map (Algebra.linearMap R K) I₀) :
(Ideal.absNorm I.num : ℚ) / |Algebra.norm ℤ (I.den:R)| =
(Ideal.absNorm I₀ : ℚ) / |Algebra.norm ℤ (a:R)| := by
rw [div_eq_div_iff]
· replace h := congr_arg (I.den • ·) h
have h' := congr_arg (a • ·) (den_mul_self_eq_num I)
dsimp only at h h'
rw [smul_comm] at h
rw [h, Submonoid.smul_def, Submonoid.smul_def, ← Submodule.ideal_span_singleton_smul,
← Submodule.ideal_span_singleton_smul, ← Submodule.map_smul'', ← Submodule.map_smul'',
(LinearMap.map_injective ?_).eq_iff, smul_eq_mul, smul_eq_mul] at h'
· simp_rw [← Int.cast_natAbs, ← Nat.cast_mul, ← Ideal.absNorm_span_singleton]
rw [← _root_.map_mul, ← _root_.map_mul, mul_comm, ← h', mul_comm]
· exact LinearMap.ker_eq_bot.mpr (IsFractionRing.injective R K)
all_goals simpa [Algebra.norm_eq_zero_iff] using nonZeroDivisors.coe_ne_zero _
/-- The absolute norm of the fractional ideal `I` extending by multiplicativity the absolute norm
on (integral) ideals. -/
noncomputable def absNorm : FractionalIdeal R⁰ K →*₀ ℚ where
toFun I := (Ideal.absNorm I.num : ℚ) / |Algebra.norm ℤ (I.den : R)|
map_zero' := by
dsimp only
rw [num_zero_eq, Submodule.zero_eq_bot, Ideal.absNorm_bot, Nat.cast_zero, zero_div]
exact IsFractionRing.injective R K
map_one' := by
dsimp only
rw [absNorm_div_norm_eq_absNorm_div_norm 1 ⊤ (by simp [Submodule.one_eq_range]),
Ideal.absNorm_top, Nat.cast_one, OneMemClass.coe_one, _root_.map_one, abs_one, Int.cast_one,
one_div_one]
map_mul' I J := by
dsimp only
rw [absNorm_div_norm_eq_absNorm_div_norm (I.den * J.den) (I.num * J.num) (by
have : Algebra.linearMap R K = (IsScalarTower.toAlgHom R R K).toLinearMap := rfl
rw [coe_mul, this, Submodule.map_mul, ← this, ← den_mul_self_eq_num, ← den_mul_self_eq_num]
exact Submodule.mul_smul_mul_eq_smul_mul_smul _ _ _ _),
Submonoid.coe_mul, _root_.map_mul, _root_.map_mul, Nat.cast_mul, div_mul_div_comm,
Int.cast_abs, Int.cast_abs, Int.cast_abs, ← abs_mul, Int.cast_mul]
theorem absNorm_eq (I : FractionalIdeal R⁰ K) :
absNorm I = (Ideal.absNorm I.num : ℚ) / |Algebra.norm ℤ (I.den : R)| := rfl
theorem absNorm_eq' {I : FractionalIdeal R⁰ K} (a : R⁰) (I₀ : Ideal R)
(h : a • (I : Submodule R K) = Submodule.map (Algebra.linearMap R K) I₀) :
absNorm I = (Ideal.absNorm I₀ : ℚ) / |Algebra.norm ℤ (a:R)| := by
rw [absNorm, ← absNorm_div_norm_eq_absNorm_div_norm a I₀ h, MonoidWithZeroHom.coe_mk,
ZeroHom.coe_mk]
| Mathlib/RingTheory/FractionalIdeal/Norm.lean | 84 | 84 | theorem absNorm_nonneg (I : FractionalIdeal R⁰ K) : 0 ≤ absNorm I := by | dsimp [absNorm]; positivity
|
/-
Copyright (c) 2021 Lu-Ming Zhang. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Lu-Ming Zhang
-/
import Mathlib.Algebra.Group.Fin
import Mathlib.LinearAlgebra.Matrix.Symmetric
#align_import linear_algebra.matrix.circulant from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
/-!
# Circulant matrices
This file contains the definition and basic results about circulant matrices.
Given a vector `v : n → α` indexed by a type that is endowed with subtraction,
`Matrix.circulant v` is the matrix whose `(i, j)`th entry is `v (i - j)`.
## Main results
- `Matrix.circulant`: the circulant matrix generated by a given vector `v : n → α`.
- `Matrix.circulant_mul`: the product of two circulant matrices `circulant v` and `circulant w` is
the circulant matrix generated by `circulant v *ᵥ w`.
- `Matrix.circulant_mul_comm`: multiplication of circulant matrices commutes when the elements do.
## Implementation notes
`Matrix.Fin.foo` is the `Fin n` version of `Matrix.foo`.
Namely, the index type of the circulant matrices in discussion is `Fin n`.
## Tags
circulant, matrix
-/
variable {α β m n R : Type*}
namespace Matrix
open Function
open Matrix
/-- Given the condition `[Sub n]` and a vector `v : n → α`,
we define `circulant v` to be the circulant matrix generated by `v` of type `Matrix n n α`.
The `(i,j)`th entry is defined to be `v (i - j)`. -/
def circulant [Sub n] (v : n → α) : Matrix n n α :=
of fun i j => v (i - j)
#align matrix.circulant Matrix.circulant
-- TODO: set as an equation lemma for `circulant`, see mathlib4#3024
@[simp]
theorem circulant_apply [Sub n] (v : n → α) (i j) : circulant v i j = v (i - j) := rfl
#align matrix.circulant_apply Matrix.circulant_apply
theorem circulant_col_zero_eq [AddGroup n] (v : n → α) (i : n) : circulant v i 0 = v i :=
congr_arg v (sub_zero _)
#align matrix.circulant_col_zero_eq Matrix.circulant_col_zero_eq
theorem circulant_injective [AddGroup n] : Injective (circulant : (n → α) → Matrix n n α) := by
intro v w h
ext k
rw [← circulant_col_zero_eq v, ← circulant_col_zero_eq w, h]
#align matrix.circulant_injective Matrix.circulant_injective
theorem Fin.circulant_injective : ∀ n, Injective fun v : Fin n → α => circulant v
| 0 => by simp [Injective]
| n + 1 => Matrix.circulant_injective
#align matrix.fin.circulant_injective Matrix.Fin.circulant_injective
@[simp]
theorem circulant_inj [AddGroup n] {v w : n → α} : circulant v = circulant w ↔ v = w :=
circulant_injective.eq_iff
#align matrix.circulant_inj Matrix.circulant_inj
@[simp]
theorem Fin.circulant_inj {n} {v w : Fin n → α} : circulant v = circulant w ↔ v = w :=
(Fin.circulant_injective n).eq_iff
#align matrix.fin.circulant_inj Matrix.Fin.circulant_inj
theorem transpose_circulant [AddGroup n] (v : n → α) :
(circulant v)ᵀ = circulant fun i => v (-i) := by ext; simp
#align matrix.transpose_circulant Matrix.transpose_circulant
theorem conjTranspose_circulant [Star α] [AddGroup n] (v : n → α) :
(circulant v)ᴴ = circulant (star fun i => v (-i)) := by ext; simp
#align matrix.conj_transpose_circulant Matrix.conjTranspose_circulant
theorem Fin.transpose_circulant : ∀ {n} (v : Fin n → α), (circulant v)ᵀ = circulant fun i => v (-i)
| 0 => by simp [Injective, eq_iff_true_of_subsingleton]
| n + 1 => Matrix.transpose_circulant
#align matrix.fin.transpose_circulant Matrix.Fin.transpose_circulant
theorem Fin.conjTranspose_circulant [Star α] :
∀ {n} (v : Fin n → α), (circulant v)ᴴ = circulant (star fun i => v (-i))
| 0 => by simp [Injective, eq_iff_true_of_subsingleton]
| n + 1 => Matrix.conjTranspose_circulant
#align matrix.fin.conj_transpose_circulant Matrix.Fin.conjTranspose_circulant
theorem map_circulant [Sub n] (v : n → α) (f : α → β) :
(circulant v).map f = circulant fun i => f (v i) :=
ext fun _ _ => rfl
#align matrix.map_circulant Matrix.map_circulant
theorem circulant_neg [Neg α] [Sub n] (v : n → α) : circulant (-v) = -circulant v :=
ext fun _ _ => rfl
#align matrix.circulant_neg Matrix.circulant_neg
@[simp]
theorem circulant_zero (α n) [Zero α] [Sub n] : circulant 0 = (0 : Matrix n n α) :=
ext fun _ _ => rfl
#align matrix.circulant_zero Matrix.circulant_zero
theorem circulant_add [Add α] [Sub n] (v w : n → α) :
circulant (v + w) = circulant v + circulant w :=
ext fun _ _ => rfl
#align matrix.circulant_add Matrix.circulant_add
theorem circulant_sub [Sub α] [Sub n] (v w : n → α) :
circulant (v - w) = circulant v - circulant w :=
ext fun _ _ => rfl
#align matrix.circulant_sub Matrix.circulant_sub
/-- The product of two circulant matrices `circulant v` and `circulant w` is
the circulant matrix generated by `circulant v *ᵥ w`. -/
| Mathlib/LinearAlgebra/Matrix/Circulant.lean | 126 | 132 | theorem circulant_mul [Semiring α] [Fintype n] [AddGroup n] (v w : n → α) :
circulant v * circulant w = circulant (circulant v *ᵥ w) := by |
ext i j
simp only [mul_apply, mulVec, circulant_apply, dotProduct]
refine Fintype.sum_equiv (Equiv.subRight j) _ _ ?_
intro x
simp only [Equiv.subRight_apply, sub_sub_sub_cancel_right]
|
/-
Copyright (c) 2018 Reid Barton. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Reid Barton
-/
import Mathlib.Topology.Bases
import Mathlib.Topology.DenseEmbedding
#align_import topology.stone_cech from "leanprover-community/mathlib"@"0a0ec35061ed9960bf0e7ffb0335f44447b58977"
/-! # Stone-Čech compactification
Construction of the Stone-Čech compactification using ultrafilters.
Parts of the formalization are based on "Ultrafilters and Topology"
by Marius Stekelenburg, particularly section 5.
-/
noncomputable section
open Filter Set
open Topology
universe u v
section Ultrafilter
/- The set of ultrafilters on α carries a natural topology which makes
it the Stone-Čech compactification of α (viewed as a discrete space). -/
/-- Basis for the topology on `Ultrafilter α`. -/
def ultrafilterBasis (α : Type u) : Set (Set (Ultrafilter α)) :=
range fun s : Set α => { u | s ∈ u }
#align ultrafilter_basis ultrafilterBasis
variable {α : Type u}
instance Ultrafilter.topologicalSpace : TopologicalSpace (Ultrafilter α) :=
TopologicalSpace.generateFrom (ultrafilterBasis α)
#align ultrafilter.topological_space Ultrafilter.topologicalSpace
theorem ultrafilterBasis_is_basis : TopologicalSpace.IsTopologicalBasis (ultrafilterBasis α) :=
⟨by
rintro _ ⟨a, rfl⟩ _ ⟨b, rfl⟩ u ⟨ua, ub⟩
refine ⟨_, ⟨a ∩ b, rfl⟩, inter_mem ua ub, fun v hv => ⟨?_, ?_⟩⟩ <;> apply mem_of_superset hv <;>
simp [inter_subset_right],
eq_univ_of_univ_subset <| subset_sUnion_of_mem <| ⟨univ, eq_univ_of_forall fun u => univ_mem⟩,
rfl⟩
#align ultrafilter_basis_is_basis ultrafilterBasis_is_basis
/-- The basic open sets for the topology on ultrafilters are open. -/
theorem ultrafilter_isOpen_basic (s : Set α) : IsOpen { u : Ultrafilter α | s ∈ u } :=
ultrafilterBasis_is_basis.isOpen ⟨s, rfl⟩
#align ultrafilter_is_open_basic ultrafilter_isOpen_basic
/-- The basic open sets for the topology on ultrafilters are also closed. -/
theorem ultrafilter_isClosed_basic (s : Set α) : IsClosed { u : Ultrafilter α | s ∈ u } := by
rw [← isOpen_compl_iff]
convert ultrafilter_isOpen_basic sᶜ using 1
ext u
exact Ultrafilter.compl_mem_iff_not_mem.symm
#align ultrafilter_is_closed_basic ultrafilter_isClosed_basic
/-- Every ultrafilter `u` on `Ultrafilter α` converges to a unique
point of `Ultrafilter α`, namely `joinM u`. -/
theorem ultrafilter_converges_iff {u : Ultrafilter (Ultrafilter α)} {x : Ultrafilter α} :
↑u ≤ 𝓝 x ↔ x = joinM u := by
rw [eq_comm, ← Ultrafilter.coe_le_coe]
change ↑u ≤ 𝓝 x ↔ ∀ s ∈ x, { v : Ultrafilter α | s ∈ v } ∈ u
simp only [TopologicalSpace.nhds_generateFrom, le_iInf_iff, ultrafilterBasis, le_principal_iff,
mem_setOf_eq]
constructor
· intro h a ha
exact h _ ⟨ha, a, rfl⟩
· rintro h a ⟨xi, a, rfl⟩
exact h _ xi
#align ultrafilter_converges_iff ultrafilter_converges_iff
instance ultrafilter_compact : CompactSpace (Ultrafilter α) :=
⟨isCompact_iff_ultrafilter_le_nhds.mpr fun f _ =>
⟨joinM f, trivial, ultrafilter_converges_iff.mpr rfl⟩⟩
#align ultrafilter_compact ultrafilter_compact
instance Ultrafilter.t2Space : T2Space (Ultrafilter α) :=
t2_iff_ultrafilter.mpr @fun x y f fx fy =>
have hx : x = joinM f := ultrafilter_converges_iff.mp fx
have hy : y = joinM f := ultrafilter_converges_iff.mp fy
hx.trans hy.symm
#align ultrafilter.t2_space Ultrafilter.t2Space
instance : TotallyDisconnectedSpace (Ultrafilter α) := by
rw [totallyDisconnectedSpace_iff_connectedComponent_singleton]
intro A
simp only [Set.eq_singleton_iff_unique_mem, mem_connectedComponent, true_and_iff]
intro B hB
rw [← Ultrafilter.coe_le_coe]
intro s hs
rw [connectedComponent_eq_iInter_isClopen, Set.mem_iInter] at hB
let Z := { F : Ultrafilter α | s ∈ F }
have hZ : IsClopen Z := ⟨ultrafilter_isClosed_basic s, ultrafilter_isOpen_basic s⟩
exact hB ⟨Z, hZ, hs⟩
@[simp] theorem Ultrafilter.tendsto_pure_self (b : Ultrafilter α) : Tendsto pure b (𝓝 b) := by
rw [Tendsto, ← coe_map, ultrafilter_converges_iff]
ext s
change s ∈ b ↔ {t | s ∈ t} ∈ map pure b
simp_rw [mem_map, preimage_setOf_eq, mem_pure, setOf_mem_eq]
theorem ultrafilter_comap_pure_nhds (b : Ultrafilter α) : comap pure (𝓝 b) ≤ b := by
rw [TopologicalSpace.nhds_generateFrom]
simp only [comap_iInf, comap_principal]
intro s hs
rw [← le_principal_iff]
refine iInf_le_of_le { u | s ∈ u } ?_
refine iInf_le_of_le ⟨hs, ⟨s, rfl⟩⟩ ?_
exact principal_mono.2 fun a => id
#align ultrafilter_comap_pure_nhds ultrafilter_comap_pure_nhds
section Embedding
| Mathlib/Topology/StoneCech.lean | 122 | 126 | theorem ultrafilter_pure_injective : Function.Injective (pure : α → Ultrafilter α) := by |
intro x y h
have : {x} ∈ (pure x : Ultrafilter α) := singleton_mem_pure
rw [h] at this
exact (mem_singleton_iff.mp (mem_pure.mp this)).symm
|
/-
Copyright (c) 2022 Justin Thomas. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Justin Thomas
-/
import Mathlib.FieldTheory.Minpoly.Field
import Mathlib.RingTheory.PrincipalIdealDomain
import Mathlib.Algebra.Polynomial.Module.AEval
#align_import linear_algebra.annihilating_polynomial from "leanprover-community/mathlib"@"d3e8e0a0237c10c2627bf52c246b15ff8e7df4c0"
/-!
# Annihilating Ideal
Given a commutative ring `R` and an `R`-algebra `A`
Every element `a : A` defines
an ideal `Polynomial.annIdeal a ⊆ R[X]`.
Simply put, this is the set of polynomials `p` where
the polynomial evaluation `p(a)` is 0.
## Special case where the ground ring is a field
In the special case that `R` is a field, we use the notation `R = 𝕜`.
Here `𝕜[X]` is a PID, so there is a polynomial `g ∈ Polynomial.annIdeal a`
which generates the ideal. We show that if this generator is
chosen to be monic, then it is the minimal polynomial of `a`,
as defined in `FieldTheory.Minpoly`.
## Special case: endomorphism algebra
Given an `R`-module `M` (`[AddCommGroup M] [Module R M]`)
there are some common specializations which may be more familiar.
* Example 1: `A = M →ₗ[R] M`, the endomorphism algebra of an `R`-module M.
* Example 2: `A = n × n` matrices with entries in `R`.
-/
open Polynomial
namespace Polynomial
section Semiring
variable {R A : Type*} [CommSemiring R] [Semiring A] [Algebra R A]
variable (R)
/-- `annIdeal R a` is the *annihilating ideal* of all `p : R[X]` such that `p(a) = 0`.
The informal notation `p(a)` stand for `Polynomial.aeval a p`.
Again informally, the annihilating ideal of `a` is
`{ p ∈ R[X] | p(a) = 0 }`. This is an ideal in `R[X]`.
The formal definition uses the kernel of the aeval map. -/
noncomputable def annIdeal (a : A) : Ideal R[X] :=
RingHom.ker ((aeval a).toRingHom : R[X] →+* A)
#align polynomial.ann_ideal Polynomial.annIdeal
variable {R}
/-- It is useful to refer to ideal membership sometimes
and the annihilation condition other times. -/
theorem mem_annIdeal_iff_aeval_eq_zero {a : A} {p : R[X]} : p ∈ annIdeal R a ↔ aeval a p = 0 :=
Iff.rfl
#align polynomial.mem_ann_ideal_iff_aeval_eq_zero Polynomial.mem_annIdeal_iff_aeval_eq_zero
end Semiring
section Field
variable {𝕜 A : Type*} [Field 𝕜] [Ring A] [Algebra 𝕜 A]
variable (𝕜)
open Submodule
/-- `annIdealGenerator 𝕜 a` is the monic generator of `annIdeal 𝕜 a`
if one exists, otherwise `0`.
Since `𝕜[X]` is a principal ideal domain there is a polynomial `g` such that
`span 𝕜 {g} = annIdeal a`. This picks some generator.
We prefer the monic generator of the ideal. -/
noncomputable def annIdealGenerator (a : A) : 𝕜[X] :=
let g := IsPrincipal.generator <| annIdeal 𝕜 a
g * C g.leadingCoeff⁻¹
#align polynomial.ann_ideal_generator Polynomial.annIdealGenerator
section
variable {𝕜}
@[simp]
theorem annIdealGenerator_eq_zero_iff {a : A} : annIdealGenerator 𝕜 a = 0 ↔ annIdeal 𝕜 a = ⊥ := by
simp only [annIdealGenerator, mul_eq_zero, IsPrincipal.eq_bot_iff_generator_eq_zero,
Polynomial.C_eq_zero, inv_eq_zero, Polynomial.leadingCoeff_eq_zero, or_self_iff]
#align polynomial.ann_ideal_generator_eq_zero_iff Polynomial.annIdealGenerator_eq_zero_iff
end
/-- `annIdealGenerator 𝕜 a` is indeed a generator. -/
@[simp]
theorem span_singleton_annIdealGenerator (a : A) :
Ideal.span {annIdealGenerator 𝕜 a} = annIdeal 𝕜 a := by
by_cases h : annIdealGenerator 𝕜 a = 0
· rw [h, annIdealGenerator_eq_zero_iff.mp h, Set.singleton_zero, Ideal.span_zero]
· rw [annIdealGenerator, Ideal.span_singleton_mul_right_unit, Ideal.span_singleton_generator]
apply Polynomial.isUnit_C.mpr
apply IsUnit.mk0
apply inv_eq_zero.not.mpr
apply Polynomial.leadingCoeff_eq_zero.not.mpr
apply (mul_ne_zero_iff.mp h).1
#align polynomial.span_singleton_ann_ideal_generator Polynomial.span_singleton_annIdealGenerator
/-- The annihilating ideal generator is a member of the annihilating ideal. -/
theorem annIdealGenerator_mem (a : A) : annIdealGenerator 𝕜 a ∈ annIdeal 𝕜 a :=
Ideal.mul_mem_right _ _ (Submodule.IsPrincipal.generator_mem _)
#align polynomial.ann_ideal_generator_mem Polynomial.annIdealGenerator_mem
theorem mem_iff_eq_smul_annIdealGenerator {p : 𝕜[X]} (a : A) :
p ∈ annIdeal 𝕜 a ↔ ∃ s : 𝕜[X], p = s • annIdealGenerator 𝕜 a := by
simp_rw [@eq_comm _ p, ← mem_span_singleton, ← span_singleton_annIdealGenerator 𝕜 a, Ideal.span]
#align polynomial.mem_iff_eq_smul_ann_ideal_generator Polynomial.mem_iff_eq_smul_annIdealGenerator
/-- The generator we chose for the annihilating ideal is monic when the ideal is non-zero. -/
theorem monic_annIdealGenerator (a : A) (hg : annIdealGenerator 𝕜 a ≠ 0) :
Monic (annIdealGenerator 𝕜 a) :=
monic_mul_leadingCoeff_inv (mul_ne_zero_iff.mp hg).1
#align polynomial.monic_ann_ideal_generator Polynomial.monic_annIdealGenerator
/-! We are working toward showing the generator of the annihilating ideal
in the field case is the minimal polynomial. We are going to use a uniqueness
theorem of the minimal polynomial.
This is the first condition: it must annihilate the original element `a : A`. -/
theorem annIdealGenerator_aeval_eq_zero (a : A) : aeval a (annIdealGenerator 𝕜 a) = 0 :=
mem_annIdeal_iff_aeval_eq_zero.mp (annIdealGenerator_mem 𝕜 a)
#align polynomial.ann_ideal_generator_aeval_eq_zero Polynomial.annIdealGenerator_aeval_eq_zero
variable {𝕜}
| Mathlib/LinearAlgebra/AnnihilatingPolynomial.lean | 140 | 142 | theorem mem_iff_annIdealGenerator_dvd {p : 𝕜[X]} {a : A} :
p ∈ annIdeal 𝕜 a ↔ annIdealGenerator 𝕜 a ∣ p := by |
rw [← Ideal.mem_span_singleton, span_singleton_annIdealGenerator]
|
/-
Copyright (c) 2021 Alena Gusakov, Bhavik Mehta, Kyle Miller. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Alena Gusakov, Bhavik Mehta, Kyle Miller
-/
import Mathlib.Combinatorics.Hall.Finite
import Mathlib.CategoryTheory.CofilteredSystem
import Mathlib.Data.Rel
#align_import combinatorics.hall.basic from "leanprover-community/mathlib"@"8195826f5c428fc283510bc67303dd4472d78498"
/-!
# Hall's Marriage Theorem
Given a list of finite subsets $X_1, X_2, \dots, X_n$ of some given set
$S$, P. Hall in [Hall1935] gave a necessary and sufficient condition for
there to be a list of distinct elements $x_1, x_2, \dots, x_n$ with
$x_i\in X_i$ for each $i$: it is when for each $k$, the union of every
$k$ of these subsets has at least $k$ elements.
Rather than a list of finite subsets, one may consider indexed families
`t : ι → Finset α` of finite subsets with `ι` a `Fintype`, and then the list
of distinct representatives is given by an injective function `f : ι → α`
such that `∀ i, f i ∈ t i`, called a *matching*.
This version is formalized as `Finset.all_card_le_biUnion_card_iff_exists_injective'`
in a separate module.
The theorem can be generalized to remove the constraint that `ι` be a `Fintype`.
As observed in [Halpern1966], one may use the constrained version of the theorem
in a compactness argument to remove this constraint.
The formulation of compactness we use is that inverse limits of nonempty finite sets
are nonempty (`nonempty_sections_of_finite_inverse_system`), which uses the
Tychonoff theorem.
The core of this module is constructing the inverse system: for every finite subset `ι'` of
`ι`, we can consider the matchings on the restriction of the indexed family `t` to `ι'`.
## Main statements
* `Finset.all_card_le_biUnion_card_iff_exists_injective` is in terms of `t : ι → Finset α`.
* `Fintype.all_card_le_rel_image_card_iff_exists_injective` is in terms of a relation
`r : α → β → Prop` such that `Rel.image r {a}` is a finite set for all `a : α`.
* `Fintype.all_card_le_filter_rel_iff_exists_injective` is in terms of a relation
`r : α → β → Prop` on finite types, with the Hall condition given in terms of
`finset.univ.filter`.
## Todo
* The statement of the theorem in terms of bipartite graphs is in preparation.
## Tags
Hall's Marriage Theorem, indexed families
-/
open Finset CategoryTheory
universe u v
/-- The set of matchings for `t` when restricted to a `Finset` of `ι`. -/
def hallMatchingsOn {ι : Type u} {α : Type v} (t : ι → Finset α) (ι' : Finset ι) :=
{ f : ι' → α | Function.Injective f ∧ ∀ x, f x ∈ t x }
#align hall_matchings_on hallMatchingsOn
/-- Given a matching on a finset, construct the restriction of that matching to a subset. -/
def hallMatchingsOn.restrict {ι : Type u} {α : Type v} (t : ι → Finset α) {ι' ι'' : Finset ι}
(h : ι' ⊆ ι'') (f : hallMatchingsOn t ι'') : hallMatchingsOn t ι' := by
refine ⟨fun i => f.val ⟨i, h i.property⟩, ?_⟩
cases' f.property with hinj hc
refine ⟨?_, fun i => hc ⟨i, h i.property⟩⟩
rintro ⟨i, hi⟩ ⟨j, hj⟩ hh
simpa only [Subtype.mk_eq_mk] using hinj hh
#align hall_matchings_on.restrict hallMatchingsOn.restrict
/-- When the Hall condition is satisfied, the set of matchings on a finite set is nonempty.
This is where `Finset.all_card_le_biUnion_card_iff_existsInjective'` comes into the argument. -/
| Mathlib/Combinatorics/Hall/Basic.lean | 77 | 86 | theorem hallMatchingsOn.nonempty {ι : Type u} {α : Type v} [DecidableEq α] (t : ι → Finset α)
(h : ∀ s : Finset ι, s.card ≤ (s.biUnion t).card) (ι' : Finset ι) :
Nonempty (hallMatchingsOn t ι') := by |
classical
refine ⟨Classical.indefiniteDescription _ ?_⟩
apply (all_card_le_biUnion_card_iff_existsInjective' fun i : ι' => t i).mp
intro s'
convert h (s'.image (↑)) using 1
· simp only [card_image_of_injective s' Subtype.coe_injective]
· rw [image_biUnion]
|
/-
Copyright (c) 2019 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Mario Carneiro
-/
import Mathlib.Algebra.Order.Ring.Abs
import Mathlib.Algebra.Order.Ring.Rat
import Mathlib.Data.Rat.Lemmas
import Mathlib.Data.Int.Sqrt
#align_import data.rat.sqrt from "leanprover-community/mathlib"@"46a64b5b4268c594af770c44d9e502afc6a515cb"
/-!
# Square root on rational numbers
This file defines the square root function on rational numbers `Rat.sqrt`
and proves several theorems about it.
-/
namespace Rat
/-- Square root function on rational numbers, defined by taking the (integer) square root of the
numerator and the square root (on natural numbers) of the denominator. -/
-- @[pp_nodot] porting note: unknown attribute
def sqrt (q : ℚ) : ℚ := mkRat (Int.sqrt q.num) (Nat.sqrt q.den)
#align rat.sqrt Rat.sqrt
| Mathlib/Data/Rat/Sqrt.lean | 30 | 31 | theorem sqrt_eq (q : ℚ) : Rat.sqrt (q * q) = |q| := by |
rw [sqrt, mul_self_num, mul_self_den, Int.sqrt_eq, Nat.sqrt_eq, abs_def, divInt_ofNat]
|
/-
Copyright (c) 2023 Rémi Bottinelli. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Rémi Bottinelli
-/
import Mathlib.Data.Set.Function
import Mathlib.Analysis.BoundedVariation
#align_import analysis.constant_speed from "leanprover-community/mathlib"@"f0c8bf9245297a541f468be517f1bde6195105e9"
/-!
# Constant speed
This file defines the notion of constant (and unit) speed for a function `f : ℝ → E` with
pseudo-emetric structure on `E` with respect to a set `s : Set ℝ` and "speed" `l : ℝ≥0`, and shows
that if `f` has locally bounded variation on `s`, it can be obtained (up to distance zero, on `s`),
as a composite `φ ∘ (variationOnFromTo f s a)`, where `φ` has unit speed and `a ∈ s`.
## Main definitions
* `HasConstantSpeedOnWith f s l`, stating that the speed of `f` on `s` is `l`.
* `HasUnitSpeedOn f s`, stating that the speed of `f` on `s` is `1`.
* `naturalParameterization f s a : ℝ → E`, the unit speed reparameterization of `f` on `s` relative
to `a`.
## Main statements
* `unique_unit_speed_on_Icc_zero` proves that if `f` and `f ∘ φ` are both naturally
parameterized on closed intervals starting at `0`, then `φ` must be the identity on
those intervals.
* `edist_naturalParameterization_eq_zero` proves that if `f` has locally bounded variation, then
precomposing `naturalParameterization f s a` with `variationOnFromTo f s a` yields a function
at distance zero from `f` on `s`.
* `has_unit_speed_naturalParameterization` proves that if `f` has locally bounded
variation, then `naturalParameterization f s a` has unit speed on `s`.
## Tags
arc-length, parameterization
-/
open scoped NNReal ENNReal
open Set MeasureTheory Classical
variable {α : Type*} [LinearOrder α] {E : Type*} [PseudoEMetricSpace E]
variable (f : ℝ → E) (s : Set ℝ) (l : ℝ≥0)
/-- `f` has constant speed `l` on `s` if the variation of `f` on `s ∩ Icc x y` is equal to
`l * (y - x)` for any `x y` in `s`.
-/
def HasConstantSpeedOnWith :=
∀ ⦃x⦄ (_ : x ∈ s) ⦃y⦄ (_ : y ∈ s), eVariationOn f (s ∩ Icc x y) = ENNReal.ofReal (l * (y - x))
#align has_constant_speed_on_with HasConstantSpeedOnWith
variable {f s l}
theorem HasConstantSpeedOnWith.hasLocallyBoundedVariationOn (h : HasConstantSpeedOnWith f s l) :
LocallyBoundedVariationOn f s := fun x y hx hy => by
simp only [BoundedVariationOn, h hx hy, Ne, ENNReal.ofReal_ne_top, not_false_iff]
#align has_constant_speed_on_with.has_locally_bounded_variation_on HasConstantSpeedOnWith.hasLocallyBoundedVariationOn
| Mathlib/Analysis/ConstantSpeed.lean | 64 | 68 | theorem hasConstantSpeedOnWith_of_subsingleton (f : ℝ → E) {s : Set ℝ} (hs : s.Subsingleton)
(l : ℝ≥0) : HasConstantSpeedOnWith f s l := by |
rintro x hx y hy; cases hs hx hy
rw [eVariationOn.subsingleton f (fun y hy z hz => hs hy.1 hz.1 : (s ∩ Icc x x).Subsingleton)]
simp only [sub_self, mul_zero, ENNReal.ofReal_zero]
|
/-
Copyright (c) 2020 Thomas Browning. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Thomas Browning
-/
import Mathlib.Algebra.GCDMonoid.Multiset
import Mathlib.Combinatorics.Enumerative.Partition
import Mathlib.Data.List.Rotate
import Mathlib.GroupTheory.Perm.Cycle.Factors
import Mathlib.GroupTheory.Perm.Closure
import Mathlib.Algebra.GCDMonoid.Nat
import Mathlib.Tactic.NormNum.GCD
#align_import group_theory.perm.cycle.type from "leanprover-community/mathlib"@"47adfab39a11a072db552f47594bf8ed2cf8a722"
/-!
# Cycle Types
In this file we define the cycle type of a permutation.
## Main definitions
- `Equiv.Perm.cycleType σ` where `σ` is a permutation of a `Fintype`
- `Equiv.Perm.partition σ` where `σ` is a permutation of a `Fintype`
## Main results
- `sum_cycleType` : The sum of `σ.cycleType` equals `σ.support.card`
- `lcm_cycleType` : The lcm of `σ.cycleType` equals `orderOf σ`
- `isConj_iff_cycleType_eq` : Two permutations are conjugate if and only if they have the same
cycle type.
- `exists_prime_orderOf_dvd_card`: For every prime `p` dividing the order of a finite group `G`
there exists an element of order `p` in `G`. This is known as Cauchy's theorem.
-/
namespace Equiv.Perm
open Equiv List Multiset
variable {α : Type*} [Fintype α]
section CycleType
variable [DecidableEq α]
/-- The cycle type of a permutation -/
def cycleType (σ : Perm α) : Multiset ℕ :=
σ.cycleFactorsFinset.1.map (Finset.card ∘ support)
#align equiv.perm.cycle_type Equiv.Perm.cycleType
theorem cycleType_def (σ : Perm α) :
σ.cycleType = σ.cycleFactorsFinset.1.map (Finset.card ∘ support) :=
rfl
#align equiv.perm.cycle_type_def Equiv.Perm.cycleType_def
theorem cycleType_eq' {σ : Perm α} (s : Finset (Perm α)) (h1 : ∀ f : Perm α, f ∈ s → f.IsCycle)
(h2 : (s : Set (Perm α)).Pairwise Disjoint)
(h0 : s.noncommProd id (h2.imp fun _ _ => Disjoint.commute) = σ) :
σ.cycleType = s.1.map (Finset.card ∘ support) := by
rw [cycleType_def]
congr
rw [cycleFactorsFinset_eq_finset]
exact ⟨h1, h2, h0⟩
#align equiv.perm.cycle_type_eq' Equiv.Perm.cycleType_eq'
theorem cycleType_eq {σ : Perm α} (l : List (Perm α)) (h0 : l.prod = σ)
(h1 : ∀ σ : Perm α, σ ∈ l → σ.IsCycle) (h2 : l.Pairwise Disjoint) :
σ.cycleType = l.map (Finset.card ∘ support) := by
have hl : l.Nodup := nodup_of_pairwise_disjoint_cycles h1 h2
rw [cycleType_eq' l.toFinset]
· simp [List.dedup_eq_self.mpr hl, (· ∘ ·)]
· simpa using h1
· simpa [hl] using h2
· simp [hl, h0]
#align equiv.perm.cycle_type_eq Equiv.Perm.cycleType_eq
@[simp] -- Porting note: new attr
| Mathlib/GroupTheory/Perm/Cycle/Type.lean | 79 | 80 | theorem cycleType_eq_zero {σ : Perm α} : σ.cycleType = 0 ↔ σ = 1 := by |
simp [cycleType_def, cycleFactorsFinset_eq_empty_iff]
|
/-
Copyright (c) 2021 Kyle Miller. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kyle Miller
-/
import Mathlib.Combinatorics.SimpleGraph.Subgraph
import Mathlib.Data.List.Rotate
#align_import combinatorics.simple_graph.connectivity from "leanprover-community/mathlib"@"b99e2d58a5e6861833fa8de11e51a81144258db4"
/-!
# Graph connectivity
In a simple graph,
* A *walk* is a finite sequence of adjacent vertices, and can be
thought of equally well as a sequence of directed edges.
* A *trail* is a walk whose edges each appear no more than once.
* A *path* is a trail whose vertices appear no more than once.
* A *cycle* is a nonempty trail whose first and last vertices are the
same and whose vertices except for the first appear no more than once.
**Warning:** graph theorists mean something different by "path" than
do homotopy theorists. A "walk" in graph theory is a "path" in
homotopy theory. Another warning: some graph theorists use "path" and
"simple path" for "walk" and "path."
Some definitions and theorems have inspiration from multigraph
counterparts in [Chou1994].
## Main definitions
* `SimpleGraph.Walk` (with accompanying pattern definitions
`SimpleGraph.Walk.nil'` and `SimpleGraph.Walk.cons'`)
* `SimpleGraph.Walk.IsTrail`, `SimpleGraph.Walk.IsPath`, and `SimpleGraph.Walk.IsCycle`.
* `SimpleGraph.Path`
* `SimpleGraph.Walk.map` and `SimpleGraph.Path.map` for the induced map on walks,
given an (injective) graph homomorphism.
* `SimpleGraph.Reachable` for the relation of whether there exists
a walk between a given pair of vertices
* `SimpleGraph.Preconnected` and `SimpleGraph.Connected` are predicates
on simple graphs for whether every vertex can be reached from every other,
and in the latter case, whether the vertex type is nonempty.
* `SimpleGraph.ConnectedComponent` is the type of connected components of
a given graph.
* `SimpleGraph.IsBridge` for whether an edge is a bridge edge
## Main statements
* `SimpleGraph.isBridge_iff_mem_and_forall_cycle_not_mem` characterizes bridge edges in terms of
there being no cycle containing them.
## Tags
walks, trails, paths, circuits, cycles, bridge edges
-/
open Function
universe u v w
namespace SimpleGraph
variable {V : Type u} {V' : Type v} {V'' : Type w}
variable (G : SimpleGraph V) (G' : SimpleGraph V') (G'' : SimpleGraph V'')
/-- A walk is a sequence of adjacent vertices. For vertices `u v : V`,
the type `walk u v` consists of all walks starting at `u` and ending at `v`.
We say that a walk *visits* the vertices it contains. The set of vertices a
walk visits is `SimpleGraph.Walk.support`.
See `SimpleGraph.Walk.nil'` and `SimpleGraph.Walk.cons'` for patterns that
can be useful in definitions since they make the vertices explicit. -/
inductive Walk : V → V → Type u
| nil {u : V} : Walk u u
| cons {u v w : V} (h : G.Adj u v) (p : Walk v w) : Walk u w
deriving DecidableEq
#align simple_graph.walk SimpleGraph.Walk
attribute [refl] Walk.nil
@[simps]
instance Walk.instInhabited (v : V) : Inhabited (G.Walk v v) := ⟨Walk.nil⟩
#align simple_graph.walk.inhabited SimpleGraph.Walk.instInhabited
/-- The one-edge walk associated to a pair of adjacent vertices. -/
@[match_pattern, reducible]
def Adj.toWalk {G : SimpleGraph V} {u v : V} (h : G.Adj u v) : G.Walk u v :=
Walk.cons h Walk.nil
#align simple_graph.adj.to_walk SimpleGraph.Adj.toWalk
namespace Walk
variable {G}
/-- Pattern to get `Walk.nil` with the vertex as an explicit argument. -/
@[match_pattern]
abbrev nil' (u : V) : G.Walk u u := Walk.nil
#align simple_graph.walk.nil' SimpleGraph.Walk.nil'
/-- Pattern to get `Walk.cons` with the vertices as explicit arguments. -/
@[match_pattern]
abbrev cons' (u v w : V) (h : G.Adj u v) (p : G.Walk v w) : G.Walk u w := Walk.cons h p
#align simple_graph.walk.cons' SimpleGraph.Walk.cons'
/-- Change the endpoints of a walk using equalities. This is helpful for relaxing
definitional equality constraints and to be able to state otherwise difficult-to-state
lemmas. While this is a simple wrapper around `Eq.rec`, it gives a canonical way to write it.
The simp-normal form is for the `copy` to be pushed outward. That way calculations can
occur within the "copy context." -/
protected def copy {u v u' v'} (p : G.Walk u v) (hu : u = u') (hv : v = v') : G.Walk u' v' :=
hu ▸ hv ▸ p
#align simple_graph.walk.copy SimpleGraph.Walk.copy
@[simp]
theorem copy_rfl_rfl {u v} (p : G.Walk u v) : p.copy rfl rfl = p := rfl
#align simple_graph.walk.copy_rfl_rfl SimpleGraph.Walk.copy_rfl_rfl
@[simp]
theorem copy_copy {u v u' v' u'' v''} (p : G.Walk u v)
(hu : u = u') (hv : v = v') (hu' : u' = u'') (hv' : v' = v'') :
(p.copy hu hv).copy hu' hv' = p.copy (hu.trans hu') (hv.trans hv') := by
subst_vars
rfl
#align simple_graph.walk.copy_copy SimpleGraph.Walk.copy_copy
@[simp]
theorem copy_nil {u u'} (hu : u = u') : (Walk.nil : G.Walk u u).copy hu hu = Walk.nil := by
subst_vars
rfl
#align simple_graph.walk.copy_nil SimpleGraph.Walk.copy_nil
| Mathlib/Combinatorics/SimpleGraph/Connectivity.lean | 146 | 149 | theorem copy_cons {u v w u' w'} (h : G.Adj u v) (p : G.Walk v w) (hu : u = u') (hw : w = w') :
(Walk.cons h p).copy hu hw = Walk.cons (hu ▸ h) (p.copy rfl hw) := by |
subst_vars
rfl
|
/-
Copyright (c) 2022 Junyan Xu. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Damiano Testa, Junyan Xu
-/
import Mathlib.Algebra.Order.Group.PiLex
import Mathlib.Data.DFinsupp.Order
import Mathlib.Data.DFinsupp.NeLocus
import Mathlib.Order.WellFoundedSet
#align_import data.dfinsupp.lex from "leanprover-community/mathlib"@"dde670c9a3f503647fd5bfdf1037bad526d3397a"
/-!
# Lexicographic order on finitely supported dependent functions
This file defines the lexicographic order on `DFinsupp`.
-/
variable {ι : Type*} {α : ι → Type*}
namespace DFinsupp
section Zero
variable [∀ i, Zero (α i)]
/-- `DFinsupp.Lex r s` is the lexicographic relation on `Π₀ i, α i`, where `ι` is ordered by `r`,
and `α i` is ordered by `s i`.
The type synonym `Lex (Π₀ i, α i)` has an order given by `DFinsupp.Lex (· < ·) (· < ·)`.
-/
protected def Lex (r : ι → ι → Prop) (s : ∀ i, α i → α i → Prop) (x y : Π₀ i, α i) : Prop :=
Pi.Lex r (s _) x y
#align dfinsupp.lex DFinsupp.Lex
-- Porting note: Added `_root_` to match more closely with Lean 3. Also updated `s`'s type.
theorem _root_.Pi.lex_eq_dfinsupp_lex {r : ι → ι → Prop} {s : ∀ i, α i → α i → Prop}
(a b : Π₀ i, α i) : Pi.Lex r (s _) (a : ∀ i, α i) b = DFinsupp.Lex r s a b :=
rfl
#align pi.lex_eq_dfinsupp_lex Pi.lex_eq_dfinsupp_lex
-- Porting note: Updated `s`'s type.
theorem lex_def {r : ι → ι → Prop} {s : ∀ i, α i → α i → Prop} {a b : Π₀ i, α i} :
DFinsupp.Lex r s a b ↔ ∃ j, (∀ d, r d j → a d = b d) ∧ s j (a j) (b j) :=
Iff.rfl
#align dfinsupp.lex_def DFinsupp.lex_def
instance [LT ι] [∀ i, LT (α i)] : LT (Lex (Π₀ i, α i)) :=
⟨fun f g ↦ DFinsupp.Lex (· < ·) (fun _ ↦ (· < ·)) (ofLex f) (ofLex g)⟩
| Mathlib/Data/DFinsupp/Lex.lean | 51 | 58 | theorem lex_lt_of_lt_of_preorder [∀ i, Preorder (α i)] (r) [IsStrictOrder ι r] {x y : Π₀ i, α i}
(hlt : x < y) : ∃ i, (∀ j, r j i → x j ≤ y j ∧ y j ≤ x j) ∧ x i < y i := by |
obtain ⟨hle, j, hlt⟩ := Pi.lt_def.1 hlt
classical
have : (x.neLocus y : Set ι).WellFoundedOn r := (x.neLocus y).finite_toSet.wellFoundedOn
obtain ⟨i, hi, hl⟩ := this.has_min { i | x i < y i } ⟨⟨j, mem_neLocus.2 hlt.ne⟩, hlt⟩
refine ⟨i, fun k hk ↦ ⟨hle k, ?_⟩, hi⟩
exact of_not_not fun h ↦ hl ⟨k, mem_neLocus.2 (ne_of_not_le h).symm⟩ ((hle k).lt_of_not_le h) hk
|
/-
Copyright (c) 2021 Anne Baanen. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Anne Baanen
-/
import Mathlib.RingTheory.IntegralClosure
import Mathlib.RingTheory.Localization.Integral
#align_import ring_theory.integrally_closed from "leanprover-community/mathlib"@"d35b4ff446f1421bd551fafa4b8efd98ac3ac408"
/-!
# Integrally closed rings
An integrally closed ring `R` contains all the elements of `Frac(R)` that are
integral over `R`. A special case of integrally closed rings are the Dedekind domains.
## Main definitions
* `IsIntegrallyClosedIn R A` states `R` contains all integral elements of `A`
* `IsIntegrallyClosed R` states `R` contains all integral elements of `Frac(R)`
## Main results
* `isIntegrallyClosed_iff K`, where `K` is a fraction field of `R`, states `R`
is integrally closed iff it is the integral closure of `R` in `K`
## TODO: Related notions
The following definitions are closely related, especially in their applications in Mathlib.
A *normal domain* is a domain that is integrally closed in its field of fractions.
[Stacks: normal domain](https://stacks.math.columbia.edu/tag/037B#0309)
Normal domains are the major use case of `IsIntegrallyClosed` at the time of writing, and we have
quite a few results that can be moved wholesale to a new `NormalDomain` definition.
In fact, before PR #6126 `IsIntegrallyClosed` was exactly defined to be a normal domain.
(So you might want to copy some of its API when you define normal domains.)
A normal ring means that localizations at all prime ideals are normal domains.
[Stacks: normal ring](https://stacks.math.columbia.edu/tag/037B#00GV)
This implies `IsIntegrallyClosed`,
[Stacks: Tag 034M](https://stacks.math.columbia.edu/tag/037B#034M)
but is equivalent to it only under some conditions (reduced + finitely many minimal primes),
[Stacks: Tag 030C](https://stacks.math.columbia.edu/tag/037B#030C)
in which case it's also equivalent to being a finite product of normal domains.
We'd need to add these conditions if we want exactly the products of Dedekind domains.
In fact noetherianity is sufficient to guarantee finitely many minimal primes, so `IsDedekindRing`
could be defined as `IsReduced`, `IsNoetherian`, `Ring.DimensionLEOne`, and either
`IsIntegrallyClosed` or `NormalDomain`. If we use `NormalDomain` then `IsReduced` is automatic,
but we could also consider a version of `NormalDomain` that only requires the localizations are
`IsIntegrallyClosed` but may not be domains, and that may not equivalent to the ring itself being
`IsIntegallyClosed` (even for noetherian rings?).
-/
open scoped nonZeroDivisors Polynomial
open Polynomial
/-- `R` is integrally closed in `A` if all integral elements of `A` are also elements of `R`.
-/
abbrev IsIntegrallyClosedIn (R A : Type*) [CommRing R] [CommRing A] [Algebra R A] :=
IsIntegralClosure R R A
/-- `R` is integrally closed if all integral elements of `Frac(R)` are also elements of `R`.
This definition uses `FractionRing R` to denote `Frac(R)`. See `isIntegrallyClosed_iff`
if you want to choose another field of fractions for `R`.
-/
abbrev IsIntegrallyClosed (R : Type*) [CommRing R] := IsIntegrallyClosedIn R (FractionRing R)
#align is_integrally_closed IsIntegrallyClosed
section Iff
variable {R : Type*} [CommRing R]
variable {A B : Type*} [CommRing A] [CommRing B] [Algebra R A] [Algebra R B]
/-- Being integrally closed is preserved under injective algebra homomorphisms. -/
theorem AlgHom.isIntegrallyClosedIn (f : A →ₐ[R] B) (hf : Function.Injective f) :
IsIntegrallyClosedIn R B → IsIntegrallyClosedIn R A := by
rintro ⟨inj, cl⟩
refine ⟨Function.Injective.of_comp (f := f) ?_, fun hx => ?_, ?_⟩
· convert inj
aesop
· obtain ⟨y, fx_eq⟩ := cl.mp ((isIntegral_algHom_iff f hf).mpr hx)
aesop
· rintro ⟨y, rfl⟩
apply (isIntegral_algHom_iff f hf).mp
aesop
/-- Being integrally closed is preserved under algebra isomorphisms. -/
theorem AlgEquiv.isIntegrallyClosedIn (e : A ≃ₐ[R] B) :
IsIntegrallyClosedIn R A ↔ IsIntegrallyClosedIn R B :=
⟨AlgHom.isIntegrallyClosedIn e.symm e.symm.injective, AlgHom.isIntegrallyClosedIn e e.injective⟩
variable (K : Type*) [CommRing K] [Algebra R K] [IsFractionRing R K]
/-- `R` is integrally closed iff it is the integral closure of itself in its field of fractions. -/
theorem isIntegrallyClosed_iff_isIntegrallyClosedIn :
IsIntegrallyClosed R ↔ IsIntegrallyClosedIn R K :=
(IsLocalization.algEquiv R⁰ _ _).isIntegrallyClosedIn
/-- `R` is integrally closed iff it is the integral closure of itself in its field of fractions. -/
theorem isIntegrallyClosed_iff_isIntegralClosure : IsIntegrallyClosed R ↔ IsIntegralClosure R R K :=
isIntegrallyClosed_iff_isIntegrallyClosedIn K
#align is_integrally_closed_iff_is_integral_closure isIntegrallyClosed_iff_isIntegralClosure
/-- `R` is integrally closed in `A` iff all integral elements of `A` are also elements of `R`. -/
| Mathlib/RingTheory/IntegrallyClosed.lean | 110 | 120 | theorem isIntegrallyClosedIn_iff {R A : Type*} [CommRing R] [CommRing A] [Algebra R A] :
IsIntegrallyClosedIn R A ↔
Function.Injective (algebraMap R A) ∧
∀ {x : A}, IsIntegral R x → ∃ y, algebraMap R A y = x := by |
constructor
· rintro ⟨_, cl⟩
aesop
· rintro ⟨inj, cl⟩
refine ⟨inj, by aesop, ?_⟩
rintro ⟨y, rfl⟩
apply isIntegral_algebraMap
|
/-
Copyright (c) 2022 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov
-/
import Mathlib.Order.Monotone.Union
import Mathlib.Algebra.Order.Group.Instances
#align_import order.monotone.odd from "leanprover-community/mathlib"@"9116dd6709f303dcf781632e15fdef382b0fc579"
/-!
# Monotonicity of odd functions
An odd function on a linear ordered additive commutative group `G` is monotone on the whole group
provided that it is monotone on `Set.Ici 0`, see `monotone_of_odd_of_monotoneOn_nonneg`. We also
prove versions of this lemma for `Antitone`, `StrictMono`, and `StrictAnti`.
-/
open Set
variable {G H : Type*} [LinearOrderedAddCommGroup G] [OrderedAddCommGroup H]
/-- An odd function on a linear ordered additive commutative group is strictly monotone on the whole
group provided that it is strictly monotone on `Set.Ici 0`. -/
| Mathlib/Order/Monotone/Odd.lean | 26 | 30 | theorem strictMono_of_odd_strictMonoOn_nonneg {f : G → H} (h₁ : ∀ x, f (-x) = -f x)
(h₂ : StrictMonoOn f (Ici 0)) : StrictMono f := by |
refine StrictMonoOn.Iic_union_Ici (fun x hx y hy hxy => neg_lt_neg_iff.1 ?_) h₂
rw [← h₁, ← h₁]
exact h₂ (neg_nonneg.2 hy) (neg_nonneg.2 hx) (neg_lt_neg hxy)
|
/-
Copyright (c) 2022 Yakov Pechersky. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yakov Pechersky
-/
import Mathlib.Data.List.Infix
#align_import data.list.rdrop from "leanprover-community/mathlib"@"26f081a2fb920140ed5bc5cc5344e84bcc7cb2b2"
/-!
# Dropping or taking from lists on the right
Taking or removing element from the tail end of a list
## Main definitions
- `rdrop n`: drop `n : ℕ` elements from the tail
- `rtake n`: take `n : ℕ` elements from the tail
- `rdropWhile p`: remove all the elements from the tail of a list until it finds the first element
for which `p : α → Bool` returns false. This element and everything before is returned.
- `rtakeWhile p`: Returns the longest terminal segment of a list for which `p : α → Bool` returns
true.
## Implementation detail
The two predicate-based methods operate by performing the regular "from-left" operation on
`List.reverse`, followed by another `List.reverse`, so they are not the most performant.
The other two rely on `List.length l` so they still traverse the list twice. One could construct
another function that takes a `L : ℕ` and use `L - n`. Under a proof condition that
`L = l.length`, the function would do the right thing.
-/
-- Make sure we don't import algebra
assert_not_exists Monoid
variable {α : Type*} (p : α → Bool) (l : List α) (n : ℕ)
namespace List
/-- Drop `n` elements from the tail end of a list. -/
def rdrop : List α :=
l.take (l.length - n)
#align list.rdrop List.rdrop
@[simp]
theorem rdrop_nil : rdrop ([] : List α) n = [] := by simp [rdrop]
#align list.rdrop_nil List.rdrop_nil
@[simp]
theorem rdrop_zero : rdrop l 0 = l := by simp [rdrop]
#align list.rdrop_zero List.rdrop_zero
theorem rdrop_eq_reverse_drop_reverse : l.rdrop n = reverse (l.reverse.drop n) := by
rw [rdrop]
induction' l using List.reverseRecOn with xs x IH generalizing n
· simp
· cases n
· simp [take_append]
· simp [take_append_eq_append_take, IH]
#align list.rdrop_eq_reverse_drop_reverse List.rdrop_eq_reverse_drop_reverse
@[simp]
theorem rdrop_concat_succ (x : α) : rdrop (l ++ [x]) (n + 1) = rdrop l n := by
simp [rdrop_eq_reverse_drop_reverse]
#align list.rdrop_concat_succ List.rdrop_concat_succ
/-- Take `n` elements from the tail end of a list. -/
def rtake : List α :=
l.drop (l.length - n)
#align list.rtake List.rtake
@[simp]
theorem rtake_nil : rtake ([] : List α) n = [] := by simp [rtake]
#align list.rtake_nil List.rtake_nil
@[simp]
theorem rtake_zero : rtake l 0 = [] := by simp [rtake]
#align list.rtake_zero List.rtake_zero
| Mathlib/Data/List/DropRight.lean | 81 | 87 | theorem rtake_eq_reverse_take_reverse : l.rtake n = reverse (l.reverse.take n) := by |
rw [rtake]
induction' l using List.reverseRecOn with xs x IH generalizing n
· simp
· cases n
· exact drop_length _
· simp [drop_append_eq_append_drop, IH]
|
/-
Copyright (c) 2023 Antoine Chambert-Loir and María Inés de Frutos-Fernández. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Antoine Chambert-Loir, María Inés de Frutos-Fernández, Bhavik Mehta, Eric Wieser
-/
import Mathlib.Algebra.Order.Sub.Defs
import Mathlib.Data.Finset.Basic
import Mathlib.Order.Interval.Finset.Defs
/-! # Antidiagonal with values in general types
We define a type class `Finset.HasAntidiagonal A` which contains a function
`antidiagonal : A → Finset (A × A)` such that `antidiagonal n`
is the finset of all pairs adding to `n`, as witnessed by `mem_antidiagonal`.
When `A` is a canonically ordered add monoid with locally finite order
this typeclass can be instantiated with `Finset.antidiagonalOfLocallyFinite`.
This applies in particular when `A` is `ℕ`, more generally or `σ →₀ ℕ`,
or even `ι →₀ A` under the additional assumption `OrderedSub A`
that make it a canonically ordered add monoid.
(In fact, we would just need an `AddMonoid` with a compatible order,
finite `Iic`, such that if `a + b = n`, then `a, b ≤ n`,
and any finiteness condition would be OK.)
For computational reasons it is better to manually provide instances for `ℕ`
and `σ →₀ ℕ`, to avoid quadratic runtime performance.
These instances are provided as `Finset.Nat.instHasAntidiagonal` and `Finsupp.instHasAntidiagonal`.
This is why `Finset.antidiagonalOfLocallyFinite` is an `abbrev` and not an `instance`.
This definition does not exactly match with that of `Multiset.antidiagonal`
defined in `Mathlib.Data.Multiset.Antidiagonal`, because of the multiplicities.
Indeed, by counting multiplicities, `Multiset α` is equivalent to `α →₀ ℕ`,
but `Finset.antidiagonal` and `Multiset.antidiagonal` will return different objects.
For example, for `s : Multiset ℕ := {0,0,0}`, `Multiset.antidiagonal s` has 8 elements
but `Finset.antidiagonal s` has only 4.
```lean
def s : Multiset ℕ := {0, 0, 0}
#eval (Finset.antidiagonal s).card -- 4
#eval Multiset.card (Multiset.antidiagonal s) -- 8
```
## TODO
* Define `HasMulAntidiagonal` (for monoids).
For `PNat`, we will recover the set of divisors of a strictly positive integer.
-/
open Function
namespace Finset
/-- The class of additive monoids with an antidiagonal -/
class HasAntidiagonal (A : Type*) [AddMonoid A] where
/-- The antidiagonal of an element `n` is the finset of pairs `(i, j)` such that `i + j = n`. -/
antidiagonal : A → Finset (A × A)
/-- A pair belongs to `antidiagonal n` iff the sum of its components is equal to `n`. -/
mem_antidiagonal {n} {a} : a ∈ antidiagonal n ↔ a.fst + a.snd = n
export HasAntidiagonal (antidiagonal mem_antidiagonal)
attribute [simp] mem_antidiagonal
variable {A : Type*}
/-- All `HasAntidiagonal` instances are equal -/
instance [AddMonoid A] : Subsingleton (HasAntidiagonal A) :=
⟨by
rintro ⟨a, ha⟩ ⟨b, hb⟩
congr with n xy
rw [ha, hb]⟩
-- The goal of this lemma is to allow to rewrite antidiagonal
-- when the decidability instances obsucate Lean
lemma hasAntidiagonal_congr (A : Type*) [AddMonoid A]
[H1 : HasAntidiagonal A] [H2 : HasAntidiagonal A] :
H1.antidiagonal = H2.antidiagonal := by congr!; apply Subsingleton.elim
theorem swap_mem_antidiagonal [AddCommMonoid A] [HasAntidiagonal A] {n : A} {xy : A × A}:
xy.swap ∈ antidiagonal n ↔ xy ∈ antidiagonal n := by
simp [add_comm]
@[simp] theorem map_prodComm_antidiagonal [AddCommMonoid A] [HasAntidiagonal A] {n : A} :
(antidiagonal n).map (Equiv.prodComm A A) = antidiagonal n :=
Finset.ext fun ⟨a, b⟩ => by simp [add_comm]
/-- See also `Finset.map_prodComm_antidiagonal`. -/
@[simp] theorem map_swap_antidiagonal [AddCommMonoid A] [HasAntidiagonal A] {n : A} :
(antidiagonal n).map ⟨Prod.swap, Prod.swap_injective⟩ = antidiagonal n :=
map_prodComm_antidiagonal
#align finset.nat.map_swap_antidiagonal Finset.map_swap_antidiagonal
section AddCancelMonoid
variable [AddCancelMonoid A] [HasAntidiagonal A] {p q : A × A} {n : A}
/-- A point in the antidiagonal is determined by its first coordinate.
See also `Finset.antidiagonal_congr'`. -/
theorem antidiagonal_congr (hp : p ∈ antidiagonal n) (hq : q ∈ antidiagonal n) :
p = q ↔ p.1 = q.1 := by
refine ⟨congr_arg Prod.fst, fun h ↦ Prod.ext h ((add_right_inj q.fst).mp ?_)⟩
rw [mem_antidiagonal] at hp hq
rw [hq, ← h, hp]
#align finset.nat.antidiagonal_congr Finset.antidiagonal_congr
/-- A point in the antidiagonal is determined by its first co-ordinate (subtype version of
`Finset.antidiagonal_congr`). This lemma is used by the `ext` tactic. -/
@[ext] theorem antidiagonal_subtype_ext {p q : antidiagonal n} (h : p.val.1 = q.val.1) : p = q :=
Subtype.ext ((antidiagonal_congr p.prop q.prop).mpr h)
end AddCancelMonoid
section AddCancelCommMonoid
variable [AddCancelCommMonoid A] [HasAntidiagonal A] {p q : A × A} {n : A}
/-- A point in the antidiagonal is determined by its second coordinate.
See also `Finset.antidiagonal_congr`. -/
lemma antidiagonal_congr' (hp : p ∈ antidiagonal n) (hq : q ∈ antidiagonal n) :
p = q ↔ p.2 = q.2 := by
rw [← Prod.swap_inj]
exact antidiagonal_congr (swap_mem_antidiagonal.2 hp) (swap_mem_antidiagonal.2 hq)
end AddCancelCommMonoid
section CanonicallyOrderedAddCommMonoid
variable [CanonicallyOrderedAddCommMonoid A] [HasAntidiagonal A]
@[simp]
| Mathlib/Data/Finset/Antidiagonal.lean | 131 | 133 | theorem antidiagonal_zero : antidiagonal (0 : A) = {(0, 0)} := by |
ext ⟨x, y⟩
simp
|
/-
Copyright (c) 2023 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov
-/
import Mathlib.Geometry.Euclidean.Inversion.Basic
import Mathlib.Analysis.InnerProductSpace.Calculus
import Mathlib.Analysis.Calculus.Deriv.Inv
import Mathlib.Tactic.AdaptationNote
/-!
# Derivative of the inversion
In this file we prove a formula for the derivative of `EuclideanGeometry.inversion c R`.
## Implementation notes
Since `fderiv` and related definitions do not work for affine spaces, we deal with an inner product
space in this file.
## Keywords
inversion, derivative
-/
open Metric Function AffineMap Set AffineSubspace
open scoped Topology RealInnerProductSpace
variable {E F : Type*} [NormedAddCommGroup E] [NormedSpace ℝ E]
[NormedAddCommGroup F] [InnerProductSpace ℝ F]
open EuclideanGeometry
section DotNotation
variable {c x : E → F} {R : E → ℝ} {s : Set E} {a : E} {n : ℕ∞}
protected theorem ContDiffWithinAt.inversion (hc : ContDiffWithinAt ℝ n c s a)
(hR : ContDiffWithinAt ℝ n R s a) (hx : ContDiffWithinAt ℝ n x s a) (hne : x a ≠ c a) :
ContDiffWithinAt ℝ n (fun a ↦ inversion (c a) (R a) (x a)) s a :=
(((hR.div (hx.dist ℝ hc hne) (dist_ne_zero.2 hne)).pow _).smul (hx.sub hc)).add hc
protected theorem ContDiffOn.inversion (hc : ContDiffOn ℝ n c s) (hR : ContDiffOn ℝ n R s)
(hx : ContDiffOn ℝ n x s) (hne : ∀ a ∈ s, x a ≠ c a) :
ContDiffOn ℝ n (fun a ↦ inversion (c a) (R a) (x a)) s := fun a ha ↦
(hc a ha).inversion (hR a ha) (hx a ha) (hne a ha)
protected nonrec theorem ContDiffAt.inversion (hc : ContDiffAt ℝ n c a) (hR : ContDiffAt ℝ n R a)
(hx : ContDiffAt ℝ n x a) (hne : x a ≠ c a) :
ContDiffAt ℝ n (fun a ↦ inversion (c a) (R a) (x a)) a :=
hc.inversion hR hx hne
protected nonrec theorem ContDiff.inversion (hc : ContDiff ℝ n c) (hR : ContDiff ℝ n R)
(hx : ContDiff ℝ n x) (hne : ∀ a, x a ≠ c a) :
ContDiff ℝ n (fun a ↦ inversion (c a) (R a) (x a)) :=
contDiff_iff_contDiffAt.2 fun a ↦ hc.contDiffAt.inversion hR.contDiffAt hx.contDiffAt (hne a)
protected theorem DifferentiableWithinAt.inversion (hc : DifferentiableWithinAt ℝ c s a)
(hR : DifferentiableWithinAt ℝ R s a) (hx : DifferentiableWithinAt ℝ x s a) (hne : x a ≠ c a) :
DifferentiableWithinAt ℝ (fun a ↦ inversion (c a) (R a) (x a)) s a :=
-- TODO: Use `.div` #5870
(((hR.mul <| (hx.dist ℝ hc hne).inv (dist_ne_zero.2 hne)).pow _).smul (hx.sub hc)).add hc
protected theorem DifferentiableOn.inversion (hc : DifferentiableOn ℝ c s)
(hR : DifferentiableOn ℝ R s) (hx : DifferentiableOn ℝ x s) (hne : ∀ a ∈ s, x a ≠ c a) :
DifferentiableOn ℝ (fun a ↦ inversion (c a) (R a) (x a)) s := fun a ha ↦
(hc a ha).inversion (hR a ha) (hx a ha) (hne a ha)
protected theorem DifferentiableAt.inversion (hc : DifferentiableAt ℝ c a)
(hR : DifferentiableAt ℝ R a) (hx : DifferentiableAt ℝ x a) (hne : x a ≠ c a) :
DifferentiableAt ℝ (fun a ↦ inversion (c a) (R a) (x a)) a := by
rw [← differentiableWithinAt_univ] at *
exact hc.inversion hR hx hne
protected theorem Differentiable.inversion (hc : Differentiable ℝ c)
(hR : Differentiable ℝ R) (hx : Differentiable ℝ x) (hne : ∀ a, x a ≠ c a) :
Differentiable ℝ (fun a ↦ inversion (c a) (R a) (x a)) := fun a ↦
(hc a).inversion (hR a) (hx a) (hne a)
end DotNotation
namespace EuclideanGeometry
variable {a b c d x y z : F} {r R : ℝ}
/-- Formula for the Fréchet derivative of `EuclideanGeometry.inversion c R`. -/
| Mathlib/Geometry/Euclidean/Inversion/Calculus.lean | 87 | 108 | theorem hasFDerivAt_inversion (hx : x ≠ c) :
HasFDerivAt (inversion c R)
((R / dist x c) ^ 2 • (reflection (ℝ ∙ (x - c))ᗮ : F →L[ℝ] F)) x := by |
rcases add_left_surjective c x with ⟨x, rfl⟩
have : HasFDerivAt (inversion c R) (?_ : F →L[ℝ] F) (c + x) := by
#adaptation_note /-- nightly-2024-03-16: simp was
simp (config := { unfoldPartialApp := true }) only [inversion] -/
simp only [inversion_def]
simp_rw [dist_eq_norm, div_pow, div_eq_mul_inv]
have A := (hasFDerivAt_id (𝕜 := ℝ) (c + x)).sub_const c
have B := ((hasDerivAt_inv <| by simpa using hx).comp_hasFDerivAt _ A.norm_sq).const_mul
(R ^ 2)
exact (B.smul A).add_const c
refine this.congr_fderiv (LinearMap.ext_on_codisjoint
(Submodule.isCompl_orthogonal_of_completeSpace (K := ℝ ∙ x)).codisjoint
(LinearMap.eqOn_span' ?_) fun y hy ↦ ?_)
· have : ((‖x‖ ^ 2) ^ 2)⁻¹ * (‖x‖ ^ 2) = (‖x‖ ^ 2)⁻¹ := by
rw [← div_eq_inv_mul, sq (‖x‖ ^ 2), div_self_mul_self']
simp [reflection_orthogonalComplement_singleton_eq_neg, real_inner_self_eq_norm_sq,
two_mul, this, div_eq_mul_inv, mul_add, add_smul, mul_pow]
· simp [Submodule.mem_orthogonal_singleton_iff_inner_right.1 hy,
reflection_mem_subspace_eq_self hy, div_eq_mul_inv, mul_pow]
|
/-
Copyright (c) 2020 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov, Eric Wieser
-/
import Mathlib.Algebra.Quaternion
import Mathlib.Analysis.InnerProductSpace.Basic
import Mathlib.Analysis.InnerProductSpace.PiL2
import Mathlib.Topology.Algebra.Algebra
#align_import analysis.quaternion from "leanprover-community/mathlib"@"07992a1d1f7a4176c6d3f160209608be4e198566"
/-!
# Quaternions as a normed algebra
In this file we define the following structures on the space `ℍ := ℍ[ℝ]` of quaternions:
* inner product space;
* normed ring;
* normed space over `ℝ`.
We show that the norm on `ℍ[ℝ]` agrees with the euclidean norm of its components.
## Notation
The following notation is available with `open Quaternion` or `open scoped Quaternion`:
* `ℍ` : quaternions
## Tags
quaternion, normed ring, normed space, normed algebra
-/
@[inherit_doc] scoped[Quaternion] notation "ℍ" => Quaternion ℝ
open scoped RealInnerProductSpace
namespace Quaternion
instance : Inner ℝ ℍ :=
⟨fun a b => (a * star b).re⟩
theorem inner_self (a : ℍ) : ⟪a, a⟫ = normSq a :=
rfl
#align quaternion.inner_self Quaternion.inner_self
theorem inner_def (a b : ℍ) : ⟪a, b⟫ = (a * star b).re :=
rfl
#align quaternion.inner_def Quaternion.inner_def
noncomputable instance : NormedAddCommGroup ℍ :=
@InnerProductSpace.Core.toNormedAddCommGroup ℝ ℍ _ _ _
{ toInner := inferInstance
conj_symm := fun x y => by simp [inner_def, mul_comm]
nonneg_re := fun x => normSq_nonneg
definite := fun x => normSq_eq_zero.1
add_left := fun x y z => by simp only [inner_def, add_mul, add_re]
smul_left := fun x y r => by simp [inner_def] }
noncomputable instance : InnerProductSpace ℝ ℍ :=
InnerProductSpace.ofCore _
theorem normSq_eq_norm_mul_self (a : ℍ) : normSq a = ‖a‖ * ‖a‖ := by
rw [← inner_self, real_inner_self_eq_norm_mul_norm]
#align quaternion.norm_sq_eq_norm_sq Quaternion.normSq_eq_norm_mul_self
instance : NormOneClass ℍ :=
⟨by rw [norm_eq_sqrt_real_inner, inner_self, normSq.map_one, Real.sqrt_one]⟩
@[simp, norm_cast]
theorem norm_coe (a : ℝ) : ‖(a : ℍ)‖ = ‖a‖ := by
rw [norm_eq_sqrt_real_inner, inner_self, normSq_coe, Real.sqrt_sq_eq_abs, Real.norm_eq_abs]
#align quaternion.norm_coe Quaternion.norm_coe
@[simp, norm_cast]
theorem nnnorm_coe (a : ℝ) : ‖(a : ℍ)‖₊ = ‖a‖₊ :=
Subtype.ext <| norm_coe a
#align quaternion.nnnorm_coe Quaternion.nnnorm_coe
@[simp, nolint simpNF] -- Porting note (#10959): simp cannot prove this
theorem norm_star (a : ℍ) : ‖star a‖ = ‖a‖ := by
simp_rw [norm_eq_sqrt_real_inner, inner_self, normSq_star]
#align quaternion.norm_star Quaternion.norm_star
@[simp, nolint simpNF] -- Porting note (#10959): simp cannot prove this
theorem nnnorm_star (a : ℍ) : ‖star a‖₊ = ‖a‖₊ :=
Subtype.ext <| norm_star a
#align quaternion.nnnorm_star Quaternion.nnnorm_star
noncomputable instance : NormedDivisionRing ℍ where
dist_eq _ _ := rfl
norm_mul' a b := by
simp only [norm_eq_sqrt_real_inner, inner_self, normSq.map_mul]
exact Real.sqrt_mul normSq_nonneg _
-- Porting note: added `noncomputable`
noncomputable instance : NormedAlgebra ℝ ℍ where
norm_smul_le := norm_smul_le
toAlgebra := Quaternion.algebra
instance : CstarRing ℍ where
norm_star_mul_self {x} := (norm_mul _ _).trans <| congr_arg (· * ‖x‖) (norm_star x)
/-- Coercion from `ℂ` to `ℍ`. -/
@[coe] def coeComplex (z : ℂ) : ℍ := ⟨z.re, z.im, 0, 0⟩
instance : Coe ℂ ℍ := ⟨coeComplex⟩
@[simp, norm_cast]
theorem coeComplex_re (z : ℂ) : (z : ℍ).re = z.re :=
rfl
#align quaternion.coe_complex_re Quaternion.coeComplex_re
@[simp, norm_cast]
theorem coeComplex_imI (z : ℂ) : (z : ℍ).imI = z.im :=
rfl
#align quaternion.coe_complex_im_i Quaternion.coeComplex_imI
@[simp, norm_cast]
theorem coeComplex_imJ (z : ℂ) : (z : ℍ).imJ = 0 :=
rfl
#align quaternion.coe_complex_im_j Quaternion.coeComplex_imJ
@[simp, norm_cast]
theorem coeComplex_imK (z : ℂ) : (z : ℍ).imK = 0 :=
rfl
#align quaternion.coe_complex_im_k Quaternion.coeComplex_imK
@[simp, norm_cast]
theorem coeComplex_add (z w : ℂ) : ↑(z + w) = (z + w : ℍ) := by ext <;> simp
#align quaternion.coe_complex_add Quaternion.coeComplex_add
@[simp, norm_cast]
| Mathlib/Analysis/Quaternion.lean | 136 | 136 | theorem coeComplex_mul (z w : ℂ) : ↑(z * w) = (z * w : ℍ) := by | ext <;> simp
|
/-
Copyright (c) 2018 Simon Hudon. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Simon Hudon
-/
import Mathlib.Control.Functor
import Mathlib.Tactic.Common
#align_import control.bifunctor from "leanprover-community/mathlib"@"dc1525fb3ef6eb4348fb1749c302d8abc303d34a"
/-!
# Functors with two arguments
This file defines bifunctors.
A bifunctor is a function `F : Type* → Type* → Type*` along with a bimap which turns `F α β`into
`F α' β'` given two functions `α → α'` and `β → β'`. It further
* respects the identity: `bimap id id = id`
* composes in the obvious way: `(bimap f' g') ∘ (bimap f g) = bimap (f' ∘ f) (g' ∘ g)`
## Main declarations
* `Bifunctor`: A typeclass for the bare bimap of a bifunctor.
* `LawfulBifunctor`: A typeclass asserting this bimap respects the bifunctor laws.
-/
universe u₀ u₁ u₂ v₀ v₁ v₂
open Function
/-- Lawless bifunctor. This typeclass only holds the data for the bimap. -/
class Bifunctor (F : Type u₀ → Type u₁ → Type u₂) where
bimap : ∀ {α α' β β'}, (α → α') → (β → β') → F α β → F α' β'
#align bifunctor Bifunctor
export Bifunctor (bimap)
/-- Bifunctor. This typeclass asserts that a lawless `Bifunctor` is lawful. -/
class LawfulBifunctor (F : Type u₀ → Type u₁ → Type u₂) [Bifunctor F] : Prop where
id_bimap : ∀ {α β} (x : F α β), bimap id id x = x
bimap_bimap :
∀ {α₀ α₁ α₂ β₀ β₁ β₂} (f : α₀ → α₁) (f' : α₁ → α₂) (g : β₀ → β₁) (g' : β₁ → β₂) (x : F α₀ β₀),
bimap f' g' (bimap f g x) = bimap (f' ∘ f) (g' ∘ g) x
#align is_lawful_bifunctor LawfulBifunctor
export LawfulBifunctor (id_bimap bimap_bimap)
attribute [higher_order bimap_id_id] id_bimap
#align is_lawful_bifunctor.bimap_id_id LawfulBifunctor.bimap_id_id
attribute [higher_order bimap_comp_bimap] bimap_bimap
#align is_lawful_bifunctor.bimap_comp_bimap LawfulBifunctor.bimap_comp_bimap
export LawfulBifunctor (bimap_id_id bimap_comp_bimap)
variable {F : Type u₀ → Type u₁ → Type u₂} [Bifunctor F]
namespace Bifunctor
/-- Left map of a bifunctor. -/
abbrev fst {α α' β} (f : α → α') : F α β → F α' β :=
bimap f id
#align bifunctor.fst Bifunctor.fst
/-- Right map of a bifunctor. -/
abbrev snd {α β β'} (f : β → β') : F α β → F α β' :=
bimap id f
#align bifunctor.snd Bifunctor.snd
variable [LawfulBifunctor F]
@[higher_order fst_id]
theorem id_fst : ∀ {α β} (x : F α β), fst id x = x :=
@id_bimap _ _ _
#align bifunctor.id_fst Bifunctor.id_fst
#align bifunctor.fst_id Bifunctor.fst_id
@[higher_order snd_id]
theorem id_snd : ∀ {α β} (x : F α β), snd id x = x :=
@id_bimap _ _ _
#align bifunctor.id_snd Bifunctor.id_snd
#align bifunctor.snd_id Bifunctor.snd_id
@[higher_order fst_comp_fst]
theorem comp_fst {α₀ α₁ α₂ β} (f : α₀ → α₁) (f' : α₁ → α₂) (x : F α₀ β) :
fst f' (fst f x) = fst (f' ∘ f) x := by simp [fst, bimap_bimap]
#align bifunctor.comp_fst Bifunctor.comp_fst
#align bifunctor.fst_comp_fst Bifunctor.fst_comp_fst
@[higher_order fst_comp_snd]
theorem fst_snd {α₀ α₁ β₀ β₁} (f : α₀ → α₁) (f' : β₀ → β₁) (x : F α₀ β₀) :
fst f (snd f' x) = bimap f f' x := by simp [fst, bimap_bimap]
#align bifunctor.fst_snd Bifunctor.fst_snd
#align bifunctor.fst_comp_snd Bifunctor.fst_comp_snd
@[higher_order snd_comp_fst]
| Mathlib/Control/Bifunctor.lean | 98 | 99 | theorem snd_fst {α₀ α₁ β₀ β₁} (f : α₀ → α₁) (f' : β₀ → β₁) (x : F α₀ β₀) :
snd f' (fst f x) = bimap f f' x := by | simp [snd, bimap_bimap]
|
/-
Copyright (c) 2019 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Johan Commelin
-/
import Mathlib.RingTheory.IntegralClosure
#align_import field_theory.minpoly.basic from "leanprover-community/mathlib"@"df0098f0db291900600f32070f6abb3e178be2ba"
/-!
# Minimal polynomials
This file defines the minimal polynomial of an element `x` of an `A`-algebra `B`,
under the assumption that x is integral over `A`, and derives some basic properties
such as irreducibility under the assumption `B` is a domain.
-/
open scoped Classical
open Polynomial Set Function
variable {A B B' : Type*}
section MinPolyDef
variable (A) [CommRing A] [Ring B] [Algebra A B]
/-- Suppose `x : B`, where `B` is an `A`-algebra.
The minimal polynomial `minpoly A x` of `x`
is a monic polynomial with coefficients in `A` of smallest degree that has `x` as its root,
if such exists (`IsIntegral A x`) or zero otherwise.
For example, if `V` is a `𝕜`-vector space for some field `𝕜` and `f : V →ₗ[𝕜] V` then
the minimal polynomial of `f` is `minpoly 𝕜 f`.
-/
noncomputable def minpoly (x : B) : A[X] :=
if hx : IsIntegral A x then degree_lt_wf.min _ hx else 0
#align minpoly minpoly
end MinPolyDef
namespace minpoly
section Ring
variable [CommRing A] [Ring B] [Ring B'] [Algebra A B] [Algebra A B']
variable {x : B}
/-- A minimal polynomial is monic. -/
theorem monic (hx : IsIntegral A x) : Monic (minpoly A x) := by
delta minpoly
rw [dif_pos hx]
exact (degree_lt_wf.min_mem _ hx).1
#align minpoly.monic minpoly.monic
/-- A minimal polynomial is nonzero. -/
theorem ne_zero [Nontrivial A] (hx : IsIntegral A x) : minpoly A x ≠ 0 :=
(monic hx).ne_zero
#align minpoly.ne_zero minpoly.ne_zero
theorem eq_zero (hx : ¬IsIntegral A x) : minpoly A x = 0 :=
dif_neg hx
#align minpoly.eq_zero minpoly.eq_zero
theorem algHom_eq (f : B →ₐ[A] B') (hf : Function.Injective f) (x : B) :
minpoly A (f x) = minpoly A x := by
refine dif_ctx_congr (isIntegral_algHom_iff _ hf) (fun _ => ?_) fun _ => rfl
simp_rw [← Polynomial.aeval_def, aeval_algHom, AlgHom.comp_apply, _root_.map_eq_zero_iff f hf]
#align minpoly.minpoly_alg_hom minpoly.algHom_eq
theorem algebraMap_eq {B} [CommRing B] [Algebra A B] [Algebra B B'] [IsScalarTower A B B']
(h : Function.Injective (algebraMap B B')) (x : B) :
minpoly A (algebraMap B B' x) = minpoly A x :=
algHom_eq (IsScalarTower.toAlgHom A B B') h x
@[simp]
theorem algEquiv_eq (f : B ≃ₐ[A] B') (x : B) : minpoly A (f x) = minpoly A x :=
algHom_eq (f : B →ₐ[A] B') f.injective x
#align minpoly.minpoly_alg_equiv minpoly.algEquiv_eq
variable (A x)
/-- An element is a root of its minimal polynomial. -/
@[simp]
theorem aeval : aeval x (minpoly A x) = 0 := by
delta minpoly
split_ifs with hx
· exact (degree_lt_wf.min_mem _ hx).2
· exact aeval_zero _
#align minpoly.aeval minpoly.aeval
/-- Given any `f : B →ₐ[A] B'` and any `x : L`, the minimal polynomial of `x` vanishes at `f x`. -/
@[simp]
theorem aeval_algHom (f : B →ₐ[A] B') (x : B) : (Polynomial.aeval (f x)) (minpoly A x) = 0 := by
rw [Polynomial.aeval_algHom, AlgHom.coe_comp, comp_apply, aeval, map_zero]
/-- A minimal polynomial is not `1`. -/
theorem ne_one [Nontrivial B] : minpoly A x ≠ 1 := by
intro h
refine (one_ne_zero : (1 : B) ≠ 0) ?_
simpa using congr_arg (Polynomial.aeval x) h
#align minpoly.ne_one minpoly.ne_one
theorem map_ne_one [Nontrivial B] {R : Type*} [Semiring R] [Nontrivial R] (f : A →+* R) :
(minpoly A x).map f ≠ 1 := by
by_cases hx : IsIntegral A x
· exact mt ((monic hx).eq_one_of_map_eq_one f) (ne_one A x)
· rw [eq_zero hx, Polynomial.map_zero]
exact zero_ne_one
#align minpoly.map_ne_one minpoly.map_ne_one
/-- A minimal polynomial is not a unit. -/
theorem not_isUnit [Nontrivial B] : ¬IsUnit (minpoly A x) := by
haveI : Nontrivial A := (algebraMap A B).domain_nontrivial
by_cases hx : IsIntegral A x
· exact mt (monic hx).eq_one_of_isUnit (ne_one A x)
· rw [eq_zero hx]
exact not_isUnit_zero
#align minpoly.not_is_unit minpoly.not_isUnit
| Mathlib/FieldTheory/Minpoly/Basic.lean | 123 | 132 | theorem mem_range_of_degree_eq_one (hx : (minpoly A x).degree = 1) :
x ∈ (algebraMap A B).range := by |
have h : IsIntegral A x := by
by_contra h
rw [eq_zero h, degree_zero, ← WithBot.coe_one] at hx
exact ne_of_lt (show ⊥ < ↑1 from WithBot.bot_lt_coe 1) hx
have key := minpoly.aeval A x
rw [eq_X_add_C_of_degree_eq_one hx, (minpoly.monic h).leadingCoeff, C_1, one_mul, aeval_add,
aeval_C, aeval_X, ← eq_neg_iff_add_eq_zero, ← RingHom.map_neg] at key
exact ⟨-(minpoly A x).coeff 0, key.symm⟩
|
/-
Copyright (c) 2023 Adrian Wüthrich. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Adrian Wüthrich
-/
import Mathlib.Combinatorics.SimpleGraph.AdjMatrix
import Mathlib.LinearAlgebra.Matrix.PosDef
/-!
# Laplacian Matrix
This module defines the Laplacian matrix of a graph, and proves some of its elementary properties.
## Main definitions & Results
* `SimpleGraph.degMatrix`: The degree matrix of a simple graph
* `SimpleGraph.lapMatrix`: The Laplacian matrix of a simple graph, defined as the difference
between the degree matrix and the adjacency matrix.
* `isPosSemidef_lapMatrix`: The Laplacian matrix is positive semidefinite.
* `rank_ker_lapMatrix_eq_card_ConnectedComponent`: The number of connected components in `G` is
the dimension of the nullspace of its Laplacian matrix.
-/
open Finset Matrix
namespace SimpleGraph
variable {V : Type*} (R : Type*)
variable [Fintype V] [DecidableEq V] (G : SimpleGraph V) [DecidableRel G.Adj]
/-- The diagonal matrix consisting of the degrees of the vertices in the graph. -/
def degMatrix [AddMonoidWithOne R] : Matrix V V R := Matrix.diagonal (G.degree ·)
/-- The *Laplacian matrix* `lapMatrix G R` of a graph `G`
is the matrix `L = D - A` where `D` is the degree and `A` the adjacency matrix of `G`. -/
def lapMatrix [AddGroupWithOne R] : Matrix V V R := G.degMatrix R - G.adjMatrix R
variable {R}
theorem isSymm_degMatrix [AddMonoidWithOne R] : (G.degMatrix R).IsSymm :=
isSymm_diagonal _
theorem isSymm_lapMatrix [AddGroupWithOne R] : (G.lapMatrix R).IsSymm :=
(isSymm_degMatrix _).sub (isSymm_adjMatrix _)
theorem degMatrix_mulVec_apply [NonAssocSemiring R] (v : V) (vec : V → R) :
(G.degMatrix R *ᵥ vec) v = G.degree v * vec v := by
rw [degMatrix, mulVec_diagonal]
theorem lapMatrix_mulVec_apply [NonAssocRing R] (v : V) (vec : V → R) :
(G.lapMatrix R *ᵥ vec) v = G.degree v * vec v - ∑ u ∈ G.neighborFinset v, vec u := by
simp_rw [lapMatrix, sub_mulVec, Pi.sub_apply, degMatrix_mulVec_apply, adjMatrix_mulVec_apply]
theorem lapMatrix_mulVec_const_eq_zero [Ring R] : mulVec (G.lapMatrix R) (fun _ ↦ 1) = 0 := by
ext1 i
rw [lapMatrix_mulVec_apply]
simp
theorem dotProduct_mulVec_degMatrix [CommRing R] (x : V → R) :
x ⬝ᵥ (G.degMatrix R *ᵥ x) = ∑ i : V, G.degree i * x i * x i := by
simp only [dotProduct, degMatrix, mulVec_diagonal, ← mul_assoc, mul_comm]
variable (R)
theorem degree_eq_sum_if_adj [AddCommMonoidWithOne R] (i : V) :
(G.degree i : R) = ∑ j : V, if G.Adj i j then 1 else 0 := by
unfold degree neighborFinset neighborSet
rw [sum_boole, Set.toFinset_setOf]
/-- Let $L$ be the graph Laplacian and let $x \in \mathbb{R}$, then
$$x^{\top} L x = \sum_{i \sim j} (x_{i}-x_{j})^{2}$$,
where $\sim$ denotes the adjacency relation -/
theorem lapMatrix_toLinearMap₂' [Field R] [CharZero R] (x : V → R) :
toLinearMap₂' (G.lapMatrix R) x x =
(∑ i : V, ∑ j : V, if G.Adj i j then (x i - x j)^2 else 0) / 2 := by
simp_rw [toLinearMap₂'_apply', lapMatrix, sub_mulVec, dotProduct_sub, dotProduct_mulVec_degMatrix,
dotProduct_mulVec_adjMatrix, ← sum_sub_distrib, degree_eq_sum_if_adj, sum_mul, ite_mul, one_mul,
zero_mul, ← sum_sub_distrib, ite_sub_ite, sub_zero]
rw [← half_add_self (∑ x_1 : V, ∑ x_2 : V, _)]
conv_lhs => enter [1,2,2,i,2,j]; rw [if_congr (adj_comm G i j) rfl rfl]
conv_lhs => enter [1,2]; rw [Finset.sum_comm]
simp_rw [← sum_add_distrib, ite_add_ite]
congr 2 with i
congr 2 with j
ring_nf
/-- The Laplacian matrix is positive semidefinite -/
theorem posSemidef_lapMatrix [LinearOrderedField R] [StarRing R] [StarOrderedRing R]
[TrivialStar R] : PosSemidef (G.lapMatrix R) := by
constructor
· rw [IsHermitian, conjTranspose_eq_transpose_of_trivial, isSymm_lapMatrix]
· intro x
rw [star_trivial, ← toLinearMap₂'_apply', lapMatrix_toLinearMap₂']
positivity
| Mathlib/Combinatorics/SimpleGraph/LapMatrix.lean | 98 | 101 | theorem lapMatrix_toLinearMap₂'_apply'_eq_zero_iff_forall_adj [LinearOrderedField R] (x : V → R) :
Matrix.toLinearMap₂' (G.lapMatrix R) x x = 0 ↔ ∀ i j : V, G.Adj i j → x i = x j := by |
simp (disch := intros; positivity)
[lapMatrix_toLinearMap₂', sum_eq_zero_iff_of_nonneg, sub_eq_zero]
|
/-
Copyright (c) 2021 Eric Wieser. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Eric Wieser
-/
import Mathlib.LinearAlgebra.TensorAlgebra.Basic
import Mathlib.LinearAlgebra.TensorPower
#align_import linear_algebra.tensor_algebra.to_tensor_power from "leanprover-community/mathlib"@"d97a0c9f7a7efe6d76d652c5a6b7c9c634b70e0a"
/-!
# Tensor algebras as direct sums of tensor powers
In this file we show that `TensorAlgebra R M` is isomorphic to a direct sum of tensor powers, as
`TensorAlgebra.equivDirectSum`.
-/
suppress_compilation
open scoped DirectSum TensorProduct
variable {R M : Type*} [CommSemiring R] [AddCommMonoid M] [Module R M]
namespace TensorPower
/-- The canonical embedding from a tensor power to the tensor algebra -/
def toTensorAlgebra {n} : ⨂[R]^n M →ₗ[R] TensorAlgebra R M :=
PiTensorProduct.lift (TensorAlgebra.tprod R M n)
#align tensor_power.to_tensor_algebra TensorPower.toTensorAlgebra
@[simp]
theorem toTensorAlgebra_tprod {n} (x : Fin n → M) :
TensorPower.toTensorAlgebra (PiTensorProduct.tprod R x) = TensorAlgebra.tprod R M n x :=
PiTensorProduct.lift.tprod _
#align tensor_power.to_tensor_algebra_tprod TensorPower.toTensorAlgebra_tprod
@[simp]
theorem toTensorAlgebra_gOne :
TensorPower.toTensorAlgebra (@GradedMonoid.GOne.one _ (fun n => ⨂[R]^n M) _ _) = 1 :=
TensorPower.toTensorAlgebra_tprod _
#align tensor_power.to_tensor_algebra_ghas_one TensorPower.toTensorAlgebra_gOne
@[simp]
theorem toTensorAlgebra_gMul {i j} (a : (⨂[R]^i) M) (b : (⨂[R]^j) M) :
TensorPower.toTensorAlgebra (@GradedMonoid.GMul.mul _ (fun n => ⨂[R]^n M) _ _ _ _ a b) =
TensorPower.toTensorAlgebra a * TensorPower.toTensorAlgebra b := by
-- change `a` and `b` to `tprod R a` and `tprod R b`
rw [TensorPower.gMul_eq_coe_linearMap, ← LinearMap.compr₂_apply, ← @LinearMap.mul_apply' R, ←
LinearMap.compl₂_apply, ← LinearMap.comp_apply]
refine LinearMap.congr_fun (LinearMap.congr_fun ?_ a) b
clear! a b
ext (a b)
-- Porting note: pulled the next two lines out of the long `simp only` below.
simp only [LinearMap.compMultilinearMap_apply]
rw [LinearMap.compr₂_apply, ← gMul_eq_coe_linearMap]
simp only [LinearMap.compr₂_apply, LinearMap.mul_apply', LinearMap.compl₂_apply,
LinearMap.comp_apply, LinearMap.compMultilinearMap_apply, PiTensorProduct.lift.tprod,
TensorPower.tprod_mul_tprod, TensorPower.toTensorAlgebra_tprod, TensorAlgebra.tprod_apply, ←
gMul_eq_coe_linearMap]
refine Eq.trans ?_ List.prod_append
congr
-- Porting note: `erw` for `Function.comp`
erw [← List.map_ofFn _ (TensorAlgebra.ι R), ← List.map_ofFn _ (TensorAlgebra.ι R), ←
List.map_ofFn _ (TensorAlgebra.ι R), ← List.map_append, List.ofFn_fin_append]
#align tensor_power.to_tensor_algebra_ghas_mul TensorPower.toTensorAlgebra_gMul
@[simp]
| Mathlib/LinearAlgebra/TensorAlgebra/ToTensorPower.lean | 68 | 72 | theorem toTensorAlgebra_galgebra_toFun (r : R) :
TensorPower.toTensorAlgebra (DirectSum.GAlgebra.toFun (R := R) (A := fun n => ⨂[R]^n M) r) =
algebraMap _ _ r := by |
rw [TensorPower.galgebra_toFun_def, TensorPower.algebraMap₀_eq_smul_one, LinearMap.map_smul,
TensorPower.toTensorAlgebra_gOne, Algebra.algebraMap_eq_smul_one]
|
/-
Copyright (c) 2021 Floris van Doorn. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Floris van Doorn
-/
import Mathlib.Logic.Function.Basic
#align_import logic.is_empty from "leanprover-community/mathlib"@"c4658a649d216f57e99621708b09dcb3dcccbd23"
/-!
# Types that are empty
In this file we define a typeclass `IsEmpty`, which expresses that a type has no elements.
## Main declaration
* `IsEmpty`: a typeclass that expresses that a type is empty.
-/
variable {α β γ : Sort*}
/-- `IsEmpty α` expresses that `α` is empty. -/
class IsEmpty (α : Sort*) : Prop where
protected false : α → False
#align is_empty IsEmpty
instance instIsEmptyEmpty : IsEmpty Empty :=
⟨Empty.elim⟩
instance instIsEmptyPEmpty : IsEmpty PEmpty :=
⟨PEmpty.elim⟩
instance : IsEmpty False :=
⟨id⟩
instance Fin.isEmpty : IsEmpty (Fin 0) :=
⟨fun n ↦ Nat.not_lt_zero n.1 n.2⟩
instance Fin.isEmpty' : IsEmpty (Fin Nat.zero) :=
Fin.isEmpty
protected theorem Function.isEmpty [IsEmpty β] (f : α → β) : IsEmpty α :=
⟨fun x ↦ IsEmpty.false (f x)⟩
#align function.is_empty Function.isEmpty
theorem Function.Surjective.isEmpty [IsEmpty α] {f : α → β} (hf : f.Surjective) : IsEmpty β :=
⟨fun y ↦ let ⟨x, _⟩ := hf y; IsEmpty.false x⟩
instance {p : α → Sort*} [h : Nonempty α] [∀ x, IsEmpty (p x)] : IsEmpty (∀ x, p x) :=
h.elim fun x ↦ Function.isEmpty <| Function.eval x
instance PProd.isEmpty_left [IsEmpty α] : IsEmpty (PProd α β) :=
Function.isEmpty PProd.fst
instance PProd.isEmpty_right [IsEmpty β] : IsEmpty (PProd α β) :=
Function.isEmpty PProd.snd
instance Prod.isEmpty_left {α β} [IsEmpty α] : IsEmpty (α × β) :=
Function.isEmpty Prod.fst
instance Prod.isEmpty_right {α β} [IsEmpty β] : IsEmpty (α × β) :=
Function.isEmpty Prod.snd
instance Quot.instIsEmpty {α : Sort*} [IsEmpty α] {r : α → α → Prop} : IsEmpty (Quot r) :=
Function.Surjective.isEmpty Quot.exists_rep
instance Quotient.instIsEmpty {α : Sort*} [IsEmpty α] {s : Setoid α} : IsEmpty (Quotient s) :=
Quot.instIsEmpty
instance [IsEmpty α] [IsEmpty β] : IsEmpty (PSum α β) :=
⟨fun x ↦ PSum.rec IsEmpty.false IsEmpty.false x⟩
instance instIsEmptySum {α β} [IsEmpty α] [IsEmpty β] : IsEmpty (Sum α β) :=
⟨fun x ↦ Sum.rec IsEmpty.false IsEmpty.false x⟩
/-- subtypes of an empty type are empty -/
instance [IsEmpty α] (p : α → Prop) : IsEmpty (Subtype p) :=
⟨fun x ↦ IsEmpty.false x.1⟩
/-- subtypes by an all-false predicate are false. -/
theorem Subtype.isEmpty_of_false {p : α → Prop} (hp : ∀ a, ¬p a) : IsEmpty (Subtype p) :=
⟨fun x ↦ hp _ x.2⟩
#align subtype.is_empty_of_false Subtype.isEmpty_of_false
/-- subtypes by false are false. -/
instance Subtype.isEmpty_false : IsEmpty { _a : α // False } :=
Subtype.isEmpty_of_false fun _ ↦ id
instance Sigma.isEmpty_left {α} [IsEmpty α] {E : α → Type*} : IsEmpty (Sigma E) :=
Function.isEmpty Sigma.fst
example [h : Nonempty α] [IsEmpty β] : IsEmpty (α → β) := by infer_instance
/-- Eliminate out of a type that `IsEmpty` (without using projection notation). -/
@[elab_as_elim]
def isEmptyElim [IsEmpty α] {p : α → Sort*} (a : α) : p a :=
(IsEmpty.false a).elim
#align is_empty_elim isEmptyElim
theorem isEmpty_iff : IsEmpty α ↔ α → False :=
⟨@IsEmpty.false α, IsEmpty.mk⟩
#align is_empty_iff isEmpty_iff
namespace IsEmpty
open Function
universe u in
/-- Eliminate out of a type that `IsEmpty` (using projection notation). -/
@[elab_as_elim]
protected def elim {α : Sort u} (_ : IsEmpty α) {p : α → Sort*} (a : α) : p a :=
isEmptyElim a
#align is_empty.elim IsEmpty.elim
/-- Non-dependent version of `IsEmpty.elim`. Helpful if the elaborator cannot elaborate `h.elim a`
correctly. -/
protected def elim' {β : Sort*} (h : IsEmpty α) (a : α) : β :=
(h.false a).elim
#align is_empty.elim' IsEmpty.elim'
protected theorem prop_iff {p : Prop} : IsEmpty p ↔ ¬p :=
isEmpty_iff
#align is_empty.prop_iff IsEmpty.prop_iff
variable [IsEmpty α]
@[simp]
theorem forall_iff {p : α → Prop} : (∀ a, p a) ↔ True :=
iff_true_intro isEmptyElim
#align is_empty.forall_iff IsEmpty.forall_iff
@[simp]
theorem exists_iff {p : α → Prop} : (∃ a, p a) ↔ False :=
iff_false_intro fun ⟨x, _⟩ ↦ IsEmpty.false x
#align is_empty.exists_iff IsEmpty.exists_iff
-- see Note [lower instance priority]
instance (priority := 100) : Subsingleton α :=
⟨isEmptyElim⟩
end IsEmpty
@[simp]
theorem not_nonempty_iff : ¬Nonempty α ↔ IsEmpty α :=
⟨fun h ↦ ⟨fun x ↦ h ⟨x⟩⟩, fun h1 h2 ↦ h2.elim h1.elim⟩
#align not_nonempty_iff not_nonempty_iff
@[simp]
theorem not_isEmpty_iff : ¬IsEmpty α ↔ Nonempty α :=
not_iff_comm.mp not_nonempty_iff
#align not_is_empty_iff not_isEmpty_iff
@[simp]
| Mathlib/Logic/IsEmpty.lean | 154 | 155 | theorem isEmpty_Prop {p : Prop} : IsEmpty p ↔ ¬p := by |
simp only [← not_nonempty_iff, nonempty_Prop]
|
/-
Copyright (c) 2021 Shing Tak Lam. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Shing Tak Lam
-/
import Mathlib.CategoryTheory.Category.Grpd
import Mathlib.CategoryTheory.Groupoid
import Mathlib.Topology.Category.TopCat.Basic
import Mathlib.Topology.Homotopy.Path
import Mathlib.Data.Set.Subsingleton
#align_import algebraic_topology.fundamental_groupoid.basic from "leanprover-community/mathlib"@"3d7987cda72abc473c7cdbbb075170e9ac620042"
/-!
# Fundamental groupoid of a space
Given a topological space `X`, we can define the fundamental groupoid of `X` to be the category with
objects being points of `X`, and morphisms `x ⟶ y` being paths from `x` to `y`, quotiented by
homotopy equivalence. With this, the fundamental group of `X` based at `x` is just the automorphism
group of `x`.
-/
open CategoryTheory
universe u v
variable {X : Type u} {Y : Type v} [TopologicalSpace X] [TopologicalSpace Y]
variable {x₀ x₁ : X}
noncomputable section
open unitInterval
namespace Path
namespace Homotopy
section
/-- Auxiliary function for `reflTransSymm`. -/
def reflTransSymmAux (x : I × I) : ℝ :=
if (x.2 : ℝ) ≤ 1 / 2 then x.1 * 2 * x.2 else x.1 * (2 - 2 * x.2)
#align path.homotopy.refl_trans_symm_aux Path.Homotopy.reflTransSymmAux
@[continuity]
theorem continuous_reflTransSymmAux : Continuous reflTransSymmAux := by
refine continuous_if_le ?_ ?_ (Continuous.continuousOn ?_) (Continuous.continuousOn ?_) ?_
· continuity
· continuity
· continuity
· continuity
intro x hx
norm_num [hx, mul_assoc]
#align path.homotopy.continuous_refl_trans_symm_aux Path.Homotopy.continuous_reflTransSymmAux
| Mathlib/AlgebraicTopology/FundamentalGroupoid/Basic.lean | 56 | 79 | theorem reflTransSymmAux_mem_I (x : I × I) : reflTransSymmAux x ∈ I := by |
dsimp only [reflTransSymmAux]
split_ifs
· constructor
· apply mul_nonneg
· apply mul_nonneg
· unit_interval
· norm_num
· unit_interval
· rw [mul_assoc]
apply mul_le_one
· unit_interval
· apply mul_nonneg
· norm_num
· unit_interval
· linarith
· constructor
· apply mul_nonneg
· unit_interval
linarith [unitInterval.nonneg x.2, unitInterval.le_one x.2]
· apply mul_le_one
· unit_interval
· linarith [unitInterval.nonneg x.2, unitInterval.le_one x.2]
· linarith [unitInterval.nonneg x.2, unitInterval.le_one x.2]
|
/-
Copyright (c) 2021 Jakob Scholbach. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jakob Scholbach
-/
import Mathlib.Algebra.CharP.Basic
import Mathlib.Algebra.CharP.Algebra
import Mathlib.Data.Nat.Prime
#align_import algebra.char_p.exp_char from "leanprover-community/mathlib"@"70fd9563a21e7b963887c9360bd29b2393e6225a"
/-!
# Exponential characteristic
This file defines the exponential characteristic, which is defined to be 1 for a ring with
characteristic 0 and the same as the ordinary characteristic, if the ordinary characteristic is
prime. This concept is useful to simplify some theorem statements.
This file establishes a few basic results relating it to the (ordinary characteristic).
The definition is stated for a semiring, but the actual results are for nontrivial rings
(as far as exponential characteristic one is concerned), respectively a ring without zero-divisors
(for prime characteristic).
## Main results
- `ExpChar`: the definition of exponential characteristic
- `expChar_is_prime_or_one`: the exponential characteristic is a prime or one
- `char_eq_expChar_iff`: the characteristic equals the exponential characteristic iff the
characteristic is prime
## Tags
exponential characteristic, characteristic
-/
universe u
variable (R : Type u)
section Semiring
variable [Semiring R]
/-- The definition of the exponential characteristic of a semiring. -/
class inductive ExpChar (R : Type u) [Semiring R] : ℕ → Prop
| zero [CharZero R] : ExpChar R 1
| prime {q : ℕ} (hprime : q.Prime) [hchar : CharP R q] : ExpChar R q
#align exp_char ExpChar
#align exp_char.prime ExpChar.prime
instance expChar_prime (p) [CharP R p] [Fact p.Prime] : ExpChar R p := ExpChar.prime Fact.out
instance expChar_zero [CharZero R] : ExpChar R 1 := ExpChar.zero
instance (S : Type*) [Semiring S] (p) [ExpChar R p] [ExpChar S p] : ExpChar (R × S) p := by
obtain hp | ⟨hp⟩ := ‹ExpChar R p›
· have := Prod.charZero_of_left R S; exact .zero
obtain _ | _ := ‹ExpChar S p›
· exact (Nat.not_prime_one hp).elim
· have := Prod.charP R S p; exact .prime hp
variable {R} in
/-- The exponential characteristic is unique. -/
theorem ExpChar.eq {p q : ℕ} (hp : ExpChar R p) (hq : ExpChar R q) : p = q := by
cases' hp with hp _ hp' hp
· cases' hq with hq _ hq' hq
exacts [rfl, False.elim (Nat.not_prime_zero (CharP.eq R hq (CharP.ofCharZero R) ▸ hq'))]
· cases' hq with hq _ hq' hq
exacts [False.elim (Nat.not_prime_zero (CharP.eq R hp (CharP.ofCharZero R) ▸ hp')),
CharP.eq R hp hq]
theorem ExpChar.congr {p : ℕ} (q : ℕ) [hq : ExpChar R q] (h : q = p) : ExpChar R p := h ▸ hq
/-- Noncomputable function that outputs the unique exponential characteristic of a semiring. -/
noncomputable def ringExpChar (R : Type*) [NonAssocSemiring R] : ℕ := max (ringChar R) 1
theorem ringExpChar.eq (q : ℕ) [h : ExpChar R q] : ringExpChar R = q := by
cases' h with _ _ h _
· haveI := CharP.ofCharZero R
rw [ringExpChar, ringChar.eq R 0]; rfl
rw [ringExpChar, ringChar.eq R q]
exact Nat.max_eq_left h.one_lt.le
@[simp]
theorem ringExpChar.eq_one (R : Type*) [NonAssocSemiring R] [CharZero R] : ringExpChar R = 1 := by
rw [ringExpChar, ringChar.eq_zero, max_eq_right zero_le_one]
/-- The exponential characteristic is one if the characteristic is zero. -/
theorem expChar_one_of_char_zero (q : ℕ) [hp : CharP R 0] [hq : ExpChar R q] : q = 1 := by
cases' hq with q hq_one hq_prime hq_hchar
· rfl
· exact False.elim <| hq_prime.ne_zero <| hq_hchar.eq R hp
#align exp_char_one_of_char_zero expChar_one_of_char_zero
/-- The characteristic equals the exponential characteristic iff the former is prime. -/
theorem char_eq_expChar_iff (p q : ℕ) [hp : CharP R p] [hq : ExpChar R q] : p = q ↔ p.Prime := by
cases' hq with q hq_one hq_prime hq_hchar
· rw [(CharP.eq R hp inferInstance : p = 0)]
decide
· exact ⟨fun hpq => hpq.symm ▸ hq_prime, fun _ => CharP.eq R hp hq_hchar⟩
#align char_eq_exp_char_iff char_eq_expChar_iff
section Nontrivial
variable [Nontrivial R]
/-- The exponential characteristic is one if the characteristic is zero. -/
theorem char_zero_of_expChar_one (p : ℕ) [hp : CharP R p] [hq : ExpChar R 1] : p = 0 := by
cases hq
· exact CharP.eq R hp inferInstance
· exact False.elim (CharP.char_ne_one R 1 rfl)
#align char_zero_of_exp_char_one char_zero_of_expChar_one
-- This could be an instance, but there are no `ExpChar R 1` instances in mathlib.
/-- The characteristic is zero if the exponential characteristic is one. -/
theorem charZero_of_expChar_one' [hq : ExpChar R 1] : CharZero R := by
cases hq
· assumption
· exact False.elim (CharP.char_ne_one R 1 rfl)
#align char_zero_of_exp_char_one' charZero_of_expChar_one'
/-- The exponential characteristic is one iff the characteristic is zero. -/
theorem expChar_one_iff_char_zero (p q : ℕ) [CharP R p] [ExpChar R q] : q = 1 ↔ p = 0 := by
constructor
· rintro rfl
exact char_zero_of_expChar_one R p
· rintro rfl
exact expChar_one_of_char_zero R q
#align exp_char_one_iff_char_zero expChar_one_iff_char_zero
section NoZeroDivisors
variable [NoZeroDivisors R]
/-- A helper lemma: the characteristic is prime if it is non-zero. -/
| Mathlib/Algebra/CharP/ExpChar.lean | 133 | 136 | theorem char_prime_of_ne_zero {p : ℕ} [hp : CharP R p] (p_ne_zero : p ≠ 0) : Nat.Prime p := by |
cases' CharP.char_is_prime_or_zero R p with h h
· exact h
· contradiction
|
/-
Copyright (c) 2021 Yakov Pechersky. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yakov Pechersky
-/
import Mathlib.Algebra.Polynomial.BigOperators
import Mathlib.Algebra.Polynomial.Degree.Lemmas
import Mathlib.LinearAlgebra.Matrix.Determinant.Basic
import Mathlib.Tactic.ComputeDegree
#align_import linear_algebra.matrix.polynomial from "leanprover-community/mathlib"@"70fd9563a21e7b963887c9360bd29b2393e6225a"
/-!
# Matrices of polynomials and polynomials of matrices
In this file, we prove results about matrices over a polynomial ring.
In particular, we give results about the polynomial given by
`det (t * I + A)`.
## References
* "The trace Cayley-Hamilton theorem" by Darij Grinberg, Section 5.3
## Tags
matrix determinant, polynomial
-/
set_option linter.uppercaseLean3 false
open Matrix Polynomial
variable {n α : Type*} [DecidableEq n] [Fintype n] [CommRing α]
open Polynomial Matrix Equiv.Perm
namespace Polynomial
theorem natDegree_det_X_add_C_le (A B : Matrix n n α) :
natDegree (det ((X : α[X]) • A.map C + B.map C : Matrix n n α[X])) ≤ Fintype.card n := by
rw [det_apply]
refine (natDegree_sum_le _ _).trans ?_
refine Multiset.max_le_of_forall_le _ _ ?_
simp only [forall_apply_eq_imp_iff, true_and_iff, Function.comp_apply, Multiset.map_map,
Multiset.mem_map, exists_imp, Finset.mem_univ_val]
intro g
calc
natDegree (sign g • ∏ i : n, (X • A.map C + B.map C : Matrix n n α[X]) (g i) i) ≤
natDegree (∏ i : n, (X • A.map C + B.map C : Matrix n n α[X]) (g i) i) := by
cases' Int.units_eq_one_or (sign g) with sg sg
· rw [sg, one_smul]
· rw [sg, Units.neg_smul, one_smul, natDegree_neg]
_ ≤ ∑ i : n, natDegree (((X : α[X]) • A.map C + B.map C : Matrix n n α[X]) (g i) i) :=
(natDegree_prod_le (Finset.univ : Finset n) fun i : n =>
(X • A.map C + B.map C : Matrix n n α[X]) (g i) i)
_ ≤ Finset.univ.card • 1 := (Finset.sum_le_card_nsmul _ _ 1 fun (i : n) _ => ?_)
_ ≤ Fintype.card n := by simp [mul_one, Algebra.id.smul_eq_mul, Finset.card_univ]
dsimp only [add_apply, smul_apply, map_apply, smul_eq_mul]
compute_degree
#align polynomial.nat_degree_det_X_add_C_le Polynomial.natDegree_det_X_add_C_le
theorem coeff_det_X_add_C_zero (A B : Matrix n n α) :
coeff (det ((X : α[X]) • A.map C + B.map C)) 0 = det B := by
rw [det_apply, finset_sum_coeff, det_apply]
refine Finset.sum_congr rfl ?_
rintro g -
convert coeff_smul (R := α) (sign g) _ 0
rw [coeff_zero_prod]
refine Finset.prod_congr rfl ?_
simp
#align polynomial.coeff_det_X_add_C_zero Polynomial.coeff_det_X_add_C_zero
theorem coeff_det_X_add_C_card (A B : Matrix n n α) :
coeff (det ((X : α[X]) • A.map C + B.map C)) (Fintype.card n) = det A := by
rw [det_apply, det_apply, finset_sum_coeff]
refine Finset.sum_congr rfl ?_
simp only [Algebra.id.smul_eq_mul, Finset.mem_univ, RingHom.mapMatrix_apply, forall_true_left,
map_apply, Pi.smul_apply]
intro g
convert coeff_smul (R := α) (sign g) _ _
rw [← mul_one (Fintype.card n)]
convert (coeff_prod_of_natDegree_le (R := α) _ _ _ _).symm
· simp [coeff_C]
· rintro p -
dsimp only [add_apply, smul_apply, map_apply, smul_eq_mul]
compute_degree
#align polynomial.coeff_det_X_add_C_card Polynomial.coeff_det_X_add_C_card
| Mathlib/LinearAlgebra/Matrix/Polynomial.lean | 89 | 102 | theorem leadingCoeff_det_X_one_add_C (A : Matrix n n α) :
leadingCoeff (det ((X : α[X]) • (1 : Matrix n n α[X]) + A.map C)) = 1 := by |
cases subsingleton_or_nontrivial α
· simp [eq_iff_true_of_subsingleton]
rw [← @det_one n, ← coeff_det_X_add_C_card _ A, leadingCoeff]
simp only [Matrix.map_one, C_eq_zero, RingHom.map_one]
rcases (natDegree_det_X_add_C_le 1 A).eq_or_lt with h | h
· simp only [RingHom.map_one, Matrix.map_one, C_eq_zero] at h
rw [h]
· -- contradiction. we have a hypothesis that the degree is less than |n|
-- but we know that coeff _ n = 1
have H := coeff_eq_zero_of_natDegree_lt h
rw [coeff_det_X_add_C_card] at H
simp at H
|
/-
Copyright (c) 2018 Kenny Lau. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kenny Lau
-/
import Mathlib.Algebra.Algebra.Operations
import Mathlib.Data.Fintype.Lattice
import Mathlib.RingTheory.Coprime.Lemmas
#align_import ring_theory.ideal.operations from "leanprover-community/mathlib"@"e7f0ddbf65bd7181a85edb74b64bdc35ba4bdc74"
/-!
# More operations on modules and ideals
-/
assert_not_exists Basis -- See `RingTheory.Ideal.Basis`
assert_not_exists Submodule.hasQuotient -- See `RingTheory.Ideal.QuotientOperations`
universe u v w x
open Pointwise
namespace Submodule
variable {R : Type u} {M : Type v} {M' F G : Type*}
section CommSemiring
variable [CommSemiring R] [AddCommMonoid M] [Module R M] [AddCommMonoid M'] [Module R M']
open Pointwise
instance hasSMul' : SMul (Ideal R) (Submodule R M) :=
⟨Submodule.map₂ (LinearMap.lsmul R M)⟩
#align submodule.has_smul' Submodule.hasSMul'
/-- This duplicates the global `smul_eq_mul`, but doesn't have to unfold anywhere near as much to
apply. -/
protected theorem _root_.Ideal.smul_eq_mul (I J : Ideal R) : I • J = I * J :=
rfl
#align ideal.smul_eq_mul Ideal.smul_eq_mul
variable (R M) in
/-- `Module.annihilator R M` is the ideal of all elements `r : R` such that `r • M = 0`. -/
def _root_.Module.annihilator : Ideal R := LinearMap.ker (LinearMap.lsmul R M)
theorem _root_.Module.mem_annihilator {r} : r ∈ Module.annihilator R M ↔ ∀ m : M, r • m = 0 :=
⟨fun h ↦ (congr($h ·)), (LinearMap.ext ·)⟩
theorem _root_.LinearMap.annihilator_le_of_injective (f : M →ₗ[R] M') (hf : Function.Injective f) :
Module.annihilator R M' ≤ Module.annihilator R M := fun x h ↦ by
rw [Module.mem_annihilator] at h ⊢; exact fun m ↦ hf (by rw [map_smul, h, f.map_zero])
theorem _root_.LinearMap.annihilator_le_of_surjective (f : M →ₗ[R] M')
(hf : Function.Surjective f) : Module.annihilator R M ≤ Module.annihilator R M' := fun x h ↦ by
rw [Module.mem_annihilator] at h ⊢
intro m; obtain ⟨m, rfl⟩ := hf m
rw [← map_smul, h, f.map_zero]
theorem _root_.LinearEquiv.annihilator_eq (e : M ≃ₗ[R] M') :
Module.annihilator R M = Module.annihilator R M' :=
(e.annihilator_le_of_surjective e.surjective).antisymm (e.annihilator_le_of_injective e.injective)
/-- `N.annihilator` is the ideal of all elements `r : R` such that `r • N = 0`. -/
abbrev annihilator (N : Submodule R M) : Ideal R :=
Module.annihilator R N
#align submodule.annihilator Submodule.annihilator
theorem annihilator_top : (⊤ : Submodule R M).annihilator = Module.annihilator R M :=
topEquiv.annihilator_eq
variable {I J : Ideal R} {N P : Submodule R M}
theorem mem_annihilator {r} : r ∈ N.annihilator ↔ ∀ n ∈ N, r • n = (0 : M) := by
simp_rw [annihilator, Module.mem_annihilator, Subtype.forall, Subtype.ext_iff]; rfl
#align submodule.mem_annihilator Submodule.mem_annihilator
theorem mem_annihilator' {r} : r ∈ N.annihilator ↔ N ≤ comap (r • (LinearMap.id : M →ₗ[R] M)) ⊥ :=
mem_annihilator.trans ⟨fun H n hn => (mem_bot R).2 <| H n hn, fun H _ hn => (mem_bot R).1 <| H hn⟩
#align submodule.mem_annihilator' Submodule.mem_annihilator'
| Mathlib/RingTheory/Ideal/Operations.lean | 82 | 96 | theorem mem_annihilator_span (s : Set M) (r : R) :
r ∈ (Submodule.span R s).annihilator ↔ ∀ n : s, r • (n : M) = 0 := by |
rw [Submodule.mem_annihilator]
constructor
· intro h n
exact h _ (Submodule.subset_span n.prop)
· intro h n hn
refine Submodule.span_induction hn ?_ ?_ ?_ ?_
· intro x hx
exact h ⟨x, hx⟩
· exact smul_zero _
· intro x y hx hy
rw [smul_add, hx, hy, zero_add]
· intro a x hx
rw [smul_comm, hx, smul_zero]
|
/-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Mitchell Lee
-/
import Mathlib.Topology.Algebra.InfiniteSum.Defs
import Mathlib.Data.Fintype.BigOperators
import Mathlib.Topology.Algebra.Monoid
/-!
# Lemmas on infinite sums and products in topological monoids
This file contains many simple lemmas on `tsum`, `HasSum` etc, which are placed here in order to
keep the basic file of definitions as short as possible.
Results requiring a group (rather than monoid) structure on the target should go in `Group.lean`.
-/
noncomputable section
open Filter Finset Function
open scoped Topology
variable {α β γ δ : Type*}
section HasProd
variable [CommMonoid α] [TopologicalSpace α]
variable {f g : β → α} {a b : α} {s : Finset β}
/-- Constant one function has product `1` -/
@[to_additive "Constant zero function has sum `0`"]
theorem hasProd_one : HasProd (fun _ ↦ 1 : β → α) 1 := by simp [HasProd, tendsto_const_nhds]
#align has_sum_zero hasSum_zero
@[to_additive]
theorem hasProd_empty [IsEmpty β] : HasProd f 1 := by
convert @hasProd_one α β _ _
#align has_sum_empty hasSum_empty
@[to_additive]
theorem multipliable_one : Multipliable (fun _ ↦ 1 : β → α) :=
hasProd_one.multipliable
#align summable_zero summable_zero
@[to_additive]
theorem multipliable_empty [IsEmpty β] : Multipliable f :=
hasProd_empty.multipliable
#align summable_empty summable_empty
@[to_additive]
theorem multipliable_congr (hfg : ∀ b, f b = g b) : Multipliable f ↔ Multipliable g :=
iff_of_eq (congr_arg Multipliable <| funext hfg)
#align summable_congr summable_congr
@[to_additive]
theorem Multipliable.congr (hf : Multipliable f) (hfg : ∀ b, f b = g b) : Multipliable g :=
(multipliable_congr hfg).mp hf
#align summable.congr Summable.congr
@[to_additive]
lemma HasProd.congr_fun (hf : HasProd f a) (h : ∀ x : β, g x = f x) : HasProd g a :=
(funext h : g = f) ▸ hf
@[to_additive]
theorem HasProd.hasProd_of_prod_eq {g : γ → α}
(h_eq : ∀ u : Finset γ, ∃ v : Finset β, ∀ v', v ⊆ v' →
∃ u', u ⊆ u' ∧ ∏ x ∈ u', g x = ∏ b ∈ v', f b)
(hf : HasProd g a) : HasProd f a :=
le_trans (map_atTop_finset_prod_le_of_prod_eq h_eq) hf
#align has_sum.has_sum_of_sum_eq HasSum.hasSum_of_sum_eq
@[to_additive]
theorem hasProd_iff_hasProd {g : γ → α}
(h₁ : ∀ u : Finset γ, ∃ v : Finset β, ∀ v', v ⊆ v' →
∃ u', u ⊆ u' ∧ ∏ x ∈ u', g x = ∏ b ∈ v', f b)
(h₂ : ∀ v : Finset β, ∃ u : Finset γ, ∀ u', u ⊆ u' →
∃ v', v ⊆ v' ∧ ∏ b ∈ v', f b = ∏ x ∈ u', g x) :
HasProd f a ↔ HasProd g a :=
⟨HasProd.hasProd_of_prod_eq h₂, HasProd.hasProd_of_prod_eq h₁⟩
#align has_sum_iff_has_sum hasSum_iff_hasSum
@[to_additive]
theorem Function.Injective.multipliable_iff {g : γ → β} (hg : Injective g)
(hf : ∀ x ∉ Set.range g, f x = 1) : Multipliable (f ∘ g) ↔ Multipliable f :=
exists_congr fun _ ↦ hg.hasProd_iff hf
#align function.injective.summable_iff Function.Injective.summable_iff
@[to_additive (attr := simp)] theorem hasProd_extend_one {g : β → γ} (hg : Injective g) :
HasProd (extend g f 1) a ↔ HasProd f a := by
rw [← hg.hasProd_iff, extend_comp hg]
exact extend_apply' _ _
@[to_additive (attr := simp)] theorem multipliable_extend_one {g : β → γ} (hg : Injective g) :
Multipliable (extend g f 1) ↔ Multipliable f :=
exists_congr fun _ ↦ hasProd_extend_one hg
@[to_additive]
theorem hasProd_subtype_iff_mulIndicator {s : Set β} :
HasProd (f ∘ (↑) : s → α) a ↔ HasProd (s.mulIndicator f) a := by
rw [← Set.mulIndicator_range_comp, Subtype.range_coe,
hasProd_subtype_iff_of_mulSupport_subset Set.mulSupport_mulIndicator_subset]
#align has_sum_subtype_iff_indicator hasSum_subtype_iff_indicator
@[to_additive]
theorem multipliable_subtype_iff_mulIndicator {s : Set β} :
Multipliable (f ∘ (↑) : s → α) ↔ Multipliable (s.mulIndicator f) :=
exists_congr fun _ ↦ hasProd_subtype_iff_mulIndicator
#align summable_subtype_iff_indicator summable_subtype_iff_indicator
@[to_additive (attr := simp)]
theorem hasProd_subtype_mulSupport : HasProd (f ∘ (↑) : mulSupport f → α) a ↔ HasProd f a :=
hasProd_subtype_iff_of_mulSupport_subset <| Set.Subset.refl _
#align has_sum_subtype_support hasSum_subtype_support
@[to_additive]
protected theorem Finset.multipliable (s : Finset β) (f : β → α) :
Multipliable (f ∘ (↑) : (↑s : Set β) → α) :=
(s.hasProd f).multipliable
#align finset.summable Finset.summable
@[to_additive]
protected theorem Set.Finite.multipliable {s : Set β} (hs : s.Finite) (f : β → α) :
Multipliable (f ∘ (↑) : s → α) := by
have := hs.toFinset.multipliable f
rwa [hs.coe_toFinset] at this
#align set.finite.summable Set.Finite.summable
@[to_additive]
| Mathlib/Topology/Algebra/InfiniteSum/Basic.lean | 132 | 133 | theorem multipliable_of_finite_mulSupport (h : (mulSupport f).Finite) : Multipliable f := by |
apply multipliable_of_ne_finset_one (s := h.toFinset); simp
|
/-
Copyright (c) 2020 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov, Moritz Doll
-/
import Mathlib.LinearAlgebra.Prod
#align_import linear_algebra.linear_pmap from "leanprover-community/mathlib"@"8b981918a93bc45a8600de608cde7944a80d92b9"
/-!
# Partially defined linear maps
A `LinearPMap R E F` or `E →ₗ.[R] F` is a linear map from a submodule of `E` to `F`.
We define a `SemilatticeInf` with `OrderBot` instance on this, and define three operations:
* `mkSpanSingleton` defines a partial linear map defined on the span of a singleton.
* `sup` takes two partial linear maps `f`, `g` that agree on the intersection of their
domains, and returns the unique partial linear map on `f.domain ⊔ g.domain` that
extends both `f` and `g`.
* `sSup` takes a `DirectedOn (· ≤ ·)` set of partial linear maps, and returns the unique
partial linear map on the `sSup` of their domains that extends all these maps.
Moreover, we define
* `LinearPMap.graph` is the graph of the partial linear map viewed as a submodule of `E × F`.
Partially defined maps are currently used in `Mathlib` to prove Hahn-Banach theorem
and its variations. Namely, `LinearPMap.sSup` implies that every chain of `LinearPMap`s
is bounded above.
They are also the basis for the theory of unbounded operators.
-/
universe u v w
/-- A `LinearPMap R E F` or `E →ₗ.[R] F` is a linear map from a submodule of `E` to `F`. -/
structure LinearPMap (R : Type u) [Ring R] (E : Type v) [AddCommGroup E] [Module R E] (F : Type w)
[AddCommGroup F] [Module R F] where
domain : Submodule R E
toFun : domain →ₗ[R] F
#align linear_pmap LinearPMap
@[inherit_doc] notation:25 E " →ₗ.[" R:25 "] " F:0 => LinearPMap R E F
variable {R : Type*} [Ring R] {E : Type*} [AddCommGroup E] [Module R E] {F : Type*}
[AddCommGroup F] [Module R F] {G : Type*} [AddCommGroup G] [Module R G]
namespace LinearPMap
open Submodule
-- Porting note: A new definition underlying a coercion `↑`.
@[coe]
def toFun' (f : E →ₗ.[R] F) : f.domain → F := f.toFun
instance : CoeFun (E →ₗ.[R] F) fun f : E →ₗ.[R] F => f.domain → F :=
⟨toFun'⟩
@[simp]
theorem toFun_eq_coe (f : E →ₗ.[R] F) (x : f.domain) : f.toFun x = f x :=
rfl
#align linear_pmap.to_fun_eq_coe LinearPMap.toFun_eq_coe
@[ext]
| Mathlib/LinearAlgebra/LinearPMap.lean | 64 | 70 | theorem ext {f g : E →ₗ.[R] F} (h : f.domain = g.domain)
(h' : ∀ ⦃x : f.domain⦄ ⦃y : g.domain⦄ (_h : (x : E) = y), f x = g y) : f = g := by |
rcases f with ⟨f_dom, f⟩
rcases g with ⟨g_dom, g⟩
obtain rfl : f_dom = g_dom := h
obtain rfl : f = g := LinearMap.ext fun x => h' rfl
rfl
|
/-
Copyright (c) 2019 Johan Commelin. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johan Commelin, Kenny Lau
-/
import Mathlib.Algebra.CharP.Defs
import Mathlib.RingTheory.Multiplicity
import Mathlib.RingTheory.PowerSeries.Basic
#align_import ring_theory.power_series.basic from "leanprover-community/mathlib"@"2d5739b61641ee4e7e53eca5688a08f66f2e6a60"
/-! # Formal power series (in one variable) - Order
The `PowerSeries.order` of a formal power series `φ` is the multiplicity of the variable `X` in `φ`.
If the coefficients form an integral domain, then `PowerSeries.order` is an
additive valuation (`PowerSeries.order_mul`, `PowerSeries.le_order_add`).
We prove that if the commutative ring `R` of coefficients is an integral domain,
then the ring `R⟦X⟧` of formal power series in one variable over `R`
is an integral domain.
Given a non-zero power series `f`, `divided_by_X_pow_order f` is the power series obtained by
dividing out the largest power of X that divides `f`, that is its order. This is useful when
proving that `R⟦X⟧` is a normalization monoid, which is done in `PowerSeries.Inverse`.
-/
noncomputable section
open Polynomial
open Finset (antidiagonal mem_antidiagonal)
namespace PowerSeries
open Finsupp (single)
variable {R : Type*}
section OrderBasic
open multiplicity
variable [Semiring R] {φ : R⟦X⟧}
| Mathlib/RingTheory/PowerSeries/Order.lean | 47 | 51 | theorem exists_coeff_ne_zero_iff_ne_zero : (∃ n : ℕ, coeff R n φ ≠ 0) ↔ φ ≠ 0 := by |
refine not_iff_not.mp ?_
push_neg
-- FIXME: the `FunLike.coe` doesn't seem to be picked up in the expression after #8386?
simp [PowerSeries.ext_iff, (coeff R _).map_zero]
|
/-
Copyright (c) 2021 Scott Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Scott Morrison
-/
import Mathlib.Algebra.Homology.Homotopy
import Mathlib.Algebra.Category.ModuleCat.Abelian
import Mathlib.Algebra.Category.ModuleCat.Subobject
import Mathlib.CategoryTheory.Limits.Shapes.ConcreteCategory
#align_import algebra.homology.Module from "leanprover-community/mathlib"@"70fd9563a21e7b963887c9360bd29b2393e6225a"
/-!
# Complexes of modules
We provide some additional API to work with homological complexes in
`ModuleCat R`.
-/
universe v u
open scoped Classical
noncomputable section
open CategoryTheory Limits HomologicalComplex
variable {R : Type v} [Ring R]
variable {ι : Type*} {c : ComplexShape ι} {C D : HomologicalComplex (ModuleCat.{u} R) c}
namespace ModuleCat
/-- To prove that two maps out of a homology group are equal,
it suffices to check they are equal on the images of cycles.
-/
| Mathlib/Algebra/Homology/ModuleCat.lean | 37 | 49 | theorem homology'_ext {L M N K : ModuleCat.{u} R} {f : L ⟶ M} {g : M ⟶ N} (w : f ≫ g = 0)
{h k : homology' f g w ⟶ K}
(w :
∀ x : LinearMap.ker g,
h (cokernel.π (imageToKernel _ _ w) (toKernelSubobject x)) =
k (cokernel.π (imageToKernel _ _ w) (toKernelSubobject x))) :
h = k := by |
refine Concrete.cokernel_funext fun n => ?_
-- Porting note: as `equiv_rw` was not ported, it was replaced by `Equiv.surjective`
-- Gosh it would be nice if `equiv_rw` could directly use an isomorphism, or an enriched `≃`.
obtain ⟨n, rfl⟩ := (kernelSubobjectIso g ≪≫
ModuleCat.kernelIsoKer g).toLinearEquiv.toEquiv.symm.surjective n
exact w n
|
/-
Copyright (c) 2021 Junyan Xu. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Junyan Xu
-/
import Mathlib.AlgebraicGeometry.Restrict
import Mathlib.CategoryTheory.Adjunction.Limits
import Mathlib.CategoryTheory.Adjunction.Reflective
#align_import algebraic_geometry.Gamma_Spec_adjunction from "leanprover-community/mathlib"@"d39590fc8728fbf6743249802486f8c91ffe07bc"
/-!
# Adjunction between `Γ` and `Spec`
We define the adjunction `ΓSpec.adjunction : Γ ⊣ Spec` by defining the unit (`toΓSpec`,
in multiple steps in this file) and counit (done in `Spec.lean`) and checking that they satisfy
the left and right triangle identities. The constructions and proofs make use of
maps and lemmas defined and proved in structure_sheaf.lean extensively.
Notice that since the adjunction is between contravariant functors, you get to choose
one of the two categories to have arrows reversed, and it is equally valid to present
the adjunction as `Spec ⊣ Γ` (`Spec.to_LocallyRingedSpace.right_op ⊣ Γ`), in which
case the unit and the counit would switch to each other.
## Main definition
* `AlgebraicGeometry.identityToΓSpec` : The natural transformation `𝟭 _ ⟶ Γ ⋙ Spec`.
* `AlgebraicGeometry.ΓSpec.locallyRingedSpaceAdjunction` : The adjunction `Γ ⊣ Spec` from
`CommRingᵒᵖ` to `LocallyRingedSpace`.
* `AlgebraicGeometry.ΓSpec.adjunction` : The adjunction `Γ ⊣ Spec` from
`CommRingᵒᵖ` to `Scheme`.
-/
-- Explicit universe annotations were used in this file to improve perfomance #12737
set_option linter.uppercaseLean3 false
noncomputable section
universe u
open PrimeSpectrum
namespace AlgebraicGeometry
open Opposite
open CategoryTheory
open StructureSheaf
open Spec (structureSheaf)
open TopologicalSpace
open AlgebraicGeometry.LocallyRingedSpace
open TopCat.Presheaf
open TopCat.Presheaf.SheafCondition
namespace LocallyRingedSpace
variable (X : LocallyRingedSpace.{u})
/-- The map from the global sections to a stalk. -/
def ΓToStalk (x : X) : Γ.obj (op X) ⟶ X.presheaf.stalk x :=
X.presheaf.germ (⟨x, trivial⟩ : (⊤ : Opens X))
#align algebraic_geometry.LocallyRingedSpace.Γ_to_stalk AlgebraicGeometry.LocallyRingedSpace.ΓToStalk
/-- The canonical map from the underlying set to the prime spectrum of `Γ(X)`. -/
def toΓSpecFun : X → PrimeSpectrum (Γ.obj (op X)) := fun x =>
comap (X.ΓToStalk x) (LocalRing.closedPoint (X.presheaf.stalk x))
#align algebraic_geometry.LocallyRingedSpace.to_Γ_Spec_fun AlgebraicGeometry.LocallyRingedSpace.toΓSpecFun
theorem not_mem_prime_iff_unit_in_stalk (r : Γ.obj (op X)) (x : X) :
r ∉ (X.toΓSpecFun x).asIdeal ↔ IsUnit (X.ΓToStalk x r) := by
erw [LocalRing.mem_maximalIdeal, Classical.not_not]
#align algebraic_geometry.LocallyRingedSpace.not_mem_prime_iff_unit_in_stalk AlgebraicGeometry.LocallyRingedSpace.not_mem_prime_iff_unit_in_stalk
/-- The preimage of a basic open in `Spec Γ(X)` under the unit is the basic
open in `X` defined by the same element (they are equal as sets). -/
theorem toΓSpec_preim_basicOpen_eq (r : Γ.obj (op X)) :
X.toΓSpecFun ⁻¹' (basicOpen r).1 = (X.toRingedSpace.basicOpen r).1 := by
ext
erw [X.toRingedSpace.mem_top_basicOpen]; apply not_mem_prime_iff_unit_in_stalk
#align algebraic_geometry.LocallyRingedSpace.to_Γ_Spec_preim_basic_open_eq AlgebraicGeometry.LocallyRingedSpace.toΓSpec_preim_basicOpen_eq
/-- `toΓSpecFun` is continuous. -/
| Mathlib/AlgebraicGeometry/GammaSpecAdjunction.lean | 91 | 95 | theorem toΓSpec_continuous : Continuous X.toΓSpecFun := by |
rw [isTopologicalBasis_basic_opens.continuous_iff]
rintro _ ⟨r, rfl⟩
erw [X.toΓSpec_preim_basicOpen_eq r]
exact (X.toRingedSpace.basicOpen r).2
|
/-
Copyright (c) 2019 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Patrick Massot, Casper Putz, Anne Baanen
-/
import Mathlib.LinearAlgebra.Dimension.LinearMap
#align_import linear_algebra.matrix.diagonal from "leanprover-community/mathlib"@"b1c23399f01266afe392a0d8f71f599a0dad4f7b"
/-!
# Diagonal matrices
This file contains some results on the linear map corresponding to a
diagonal matrix (`range`, `ker` and `rank`).
## Tags
matrix, diagonal, linear_map
-/
noncomputable section
open LinearMap Matrix Set Submodule Matrix
universe u v w
namespace Matrix
section CommSemiring -- Porting note: generalized from `CommRing`
variable {n : Type*} [Fintype n] [DecidableEq n] {R : Type v} [CommSemiring R]
theorem proj_diagonal (i : n) (w : n → R) : (proj i).comp (toLin' (diagonal w)) = w i • proj i :=
LinearMap.ext fun _ => mulVec_diagonal _ _ _
#align matrix.proj_diagonal Matrix.proj_diagonal
theorem diagonal_comp_stdBasis (w : n → R) (i : n) :
(diagonal w).toLin'.comp (LinearMap.stdBasis R (fun _ : n => R) i) =
w i • LinearMap.stdBasis R (fun _ : n => R) i :=
LinearMap.ext fun x => (diagonal_mulVec_single w _ _).trans (Pi.single_smul' i (w i) x)
#align matrix.diagonal_comp_std_basis Matrix.diagonal_comp_stdBasis
theorem diagonal_toLin' (w : n → R) :
toLin' (diagonal w) = LinearMap.pi fun i => w i • LinearMap.proj i :=
LinearMap.ext fun _ => funext fun _ => mulVec_diagonal _ _ _
#align matrix.diagonal_to_lin' Matrix.diagonal_toLin'
end CommSemiring
section Semifield
variable {m n : Type*} [Fintype m] [Fintype n] {K : Type u} [Semifield K]
-- maybe try to relax the universe constraint
theorem ker_diagonal_toLin' [DecidableEq m] (w : m → K) :
ker (toLin' (diagonal w)) =
⨆ i ∈ { i | w i = 0 }, LinearMap.range (LinearMap.stdBasis K (fun _ => K) i) := by
rw [← comap_bot, ← iInf_ker_proj, comap_iInf]
have := fun i : m => ker_comp (toLin' (diagonal w)) (proj i)
simp only [comap_iInf, ← this, proj_diagonal, ker_smul']
have : univ ⊆ { i : m | w i = 0 } ∪ { i : m | w i = 0 }ᶜ := by rw [Set.union_compl_self]
exact (iSup_range_stdBasis_eq_iInf_ker_proj K (fun _ : m => K) disjoint_compl_right this
(Set.toFinite _)).symm
#align matrix.ker_diagonal_to_lin' Matrix.ker_diagonal_toLin'
| Mathlib/LinearAlgebra/Matrix/Diagonal.lean | 67 | 73 | theorem range_diagonal [DecidableEq m] (w : m → K) :
LinearMap.range (toLin' (diagonal w)) =
⨆ i ∈ { i | w i ≠ 0 }, LinearMap.range (LinearMap.stdBasis K (fun _ => K) i) := by |
dsimp only [mem_setOf_eq]
rw [← Submodule.map_top, ← iSup_range_stdBasis, Submodule.map_iSup]
congr; funext i
rw [← LinearMap.range_comp, diagonal_comp_stdBasis, ← range_smul']
|
/-
Copyright (c) 2020 Paul van Wamelen. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Paul van Wamelen
-/
import Mathlib.NumberTheory.FLT.Basic
import Mathlib.NumberTheory.PythagoreanTriples
import Mathlib.RingTheory.Coprime.Lemmas
import Mathlib.Tactic.LinearCombination
#align_import number_theory.fermat4 from "leanprover-community/mathlib"@"10b4e499f43088dd3bb7b5796184ad5216648ab1"
/-!
# Fermat's Last Theorem for the case n = 4
There are no non-zero integers `a`, `b` and `c` such that `a ^ 4 + b ^ 4 = c ^ 4`.
-/
noncomputable section
open scoped Classical
/-- Shorthand for three non-zero integers `a`, `b`, and `c` satisfying `a ^ 4 + b ^ 4 = c ^ 2`.
We will show that no integers satisfy this equation. Clearly Fermat's Last theorem for n = 4
follows. -/
def Fermat42 (a b c : ℤ) : Prop :=
a ≠ 0 ∧ b ≠ 0 ∧ a ^ 4 + b ^ 4 = c ^ 2
#align fermat_42 Fermat42
namespace Fermat42
theorem comm {a b c : ℤ} : Fermat42 a b c ↔ Fermat42 b a c := by
delta Fermat42
rw [add_comm]
tauto
#align fermat_42.comm Fermat42.comm
theorem mul {a b c k : ℤ} (hk0 : k ≠ 0) :
Fermat42 a b c ↔ Fermat42 (k * a) (k * b) (k ^ 2 * c) := by
delta Fermat42
constructor
· intro f42
constructor
· exact mul_ne_zero hk0 f42.1
constructor
· exact mul_ne_zero hk0 f42.2.1
· have H : a ^ 4 + b ^ 4 = c ^ 2 := f42.2.2
linear_combination k ^ 4 * H
· intro f42
constructor
· exact right_ne_zero_of_mul f42.1
constructor
· exact right_ne_zero_of_mul f42.2.1
apply (mul_right_inj' (pow_ne_zero 4 hk0)).mp
linear_combination f42.2.2
#align fermat_42.mul Fermat42.mul
theorem ne_zero {a b c : ℤ} (h : Fermat42 a b c) : c ≠ 0 := by
apply ne_zero_pow two_ne_zero _; apply ne_of_gt
rw [← h.2.2, (by ring : a ^ 4 + b ^ 4 = (a ^ 2) ^ 2 + (b ^ 2) ^ 2)]
exact
add_pos (sq_pos_of_ne_zero (pow_ne_zero 2 h.1)) (sq_pos_of_ne_zero (pow_ne_zero 2 h.2.1))
#align fermat_42.ne_zero Fermat42.ne_zero
/-- We say a solution to `a ^ 4 + b ^ 4 = c ^ 2` is minimal if there is no other solution with
a smaller `c` (in absolute value). -/
def Minimal (a b c : ℤ) : Prop :=
Fermat42 a b c ∧ ∀ a1 b1 c1 : ℤ, Fermat42 a1 b1 c1 → Int.natAbs c ≤ Int.natAbs c1
#align fermat_42.minimal Fermat42.Minimal
/-- if we have a solution to `a ^ 4 + b ^ 4 = c ^ 2` then there must be a minimal one. -/
theorem exists_minimal {a b c : ℤ} (h : Fermat42 a b c) : ∃ a0 b0 c0, Minimal a0 b0 c0 := by
let S : Set ℕ := { n | ∃ s : ℤ × ℤ × ℤ, Fermat42 s.1 s.2.1 s.2.2 ∧ n = Int.natAbs s.2.2 }
have S_nonempty : S.Nonempty := by
use Int.natAbs c
rw [Set.mem_setOf_eq]
use ⟨a, ⟨b, c⟩⟩
let m : ℕ := Nat.find S_nonempty
have m_mem : m ∈ S := Nat.find_spec S_nonempty
rcases m_mem with ⟨s0, hs0, hs1⟩
use s0.1, s0.2.1, s0.2.2, hs0
intro a1 b1 c1 h1
rw [← hs1]
apply Nat.find_min'
use ⟨a1, ⟨b1, c1⟩⟩
#align fermat_42.exists_minimal Fermat42.exists_minimal
/-- a minimal solution to `a ^ 4 + b ^ 4 = c ^ 2` must have `a` and `b` coprime. -/
| Mathlib/NumberTheory/FLT/Four.lean | 89 | 105 | theorem coprime_of_minimal {a b c : ℤ} (h : Minimal a b c) : IsCoprime a b := by |
apply Int.gcd_eq_one_iff_coprime.mp
by_contra hab
obtain ⟨p, hp, hpa, hpb⟩ := Nat.Prime.not_coprime_iff_dvd.mp hab
obtain ⟨a1, rfl⟩ := Int.natCast_dvd.mpr hpa
obtain ⟨b1, rfl⟩ := Int.natCast_dvd.mpr hpb
have hpc : (p : ℤ) ^ 2 ∣ c := by
rw [← Int.pow_dvd_pow_iff two_ne_zero, ← h.1.2.2]
apply Dvd.intro (a1 ^ 4 + b1 ^ 4)
ring
obtain ⟨c1, rfl⟩ := hpc
have hf : Fermat42 a1 b1 c1 :=
(Fermat42.mul (Int.natCast_ne_zero.mpr (Nat.Prime.ne_zero hp))).mpr h.1
apply Nat.le_lt_asymm (h.2 _ _ _ hf)
rw [Int.natAbs_mul, lt_mul_iff_one_lt_left, Int.natAbs_pow, Int.natAbs_ofNat]
· exact Nat.one_lt_pow two_ne_zero (Nat.Prime.one_lt hp)
· exact Nat.pos_of_ne_zero (Int.natAbs_ne_zero.2 (ne_zero hf))
|
/-
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.LinearAlgebra.Ray
import Mathlib.LinearAlgebra.Determinant
#align_import linear_algebra.orientation from "leanprover-community/mathlib"@"0c1d80f5a86b36c1db32e021e8d19ae7809d5b79"
/-!
# Orientations of modules
This file defines orientations of modules.
## Main definitions
* `Orientation` is a type synonym for `Module.Ray` for the case where the module is that of
alternating maps from a module to its underlying ring. An orientation may be associated with an
alternating map or with a basis.
* `Module.Oriented` is a type class for a choice of orientation of a module that is considered
the positive orientation.
## Implementation notes
`Orientation` is defined for an arbitrary index type, but the main intended use case is when
that index type is a `Fintype` and there exists a basis of the same cardinality.
## References
* https://en.wikipedia.org/wiki/Orientation_(vector_space)
-/
noncomputable section
section OrderedCommSemiring
variable (R : Type*) [StrictOrderedCommSemiring R]
variable (M : Type*) [AddCommMonoid M] [Module R M]
variable {N : Type*} [AddCommMonoid N] [Module R N]
variable (ι ι' : Type*)
/-- An orientation of a module, intended to be used when `ι` is a `Fintype` with the same
cardinality as a basis. -/
abbrev Orientation := Module.Ray R (M [⋀^ι]→ₗ[R] R)
#align orientation Orientation
/-- A type class fixing an orientation of a module. -/
class Module.Oriented where
/-- Fix a positive orientation. -/
positiveOrientation : Orientation R M ι
#align module.oriented Module.Oriented
export Module.Oriented (positiveOrientation)
variable {R M}
/-- An equivalence between modules implies an equivalence between orientations. -/
def Orientation.map (e : M ≃ₗ[R] N) : Orientation R M ι ≃ Orientation R N ι :=
Module.Ray.map <| AlternatingMap.domLCongr R R ι R e
#align orientation.map Orientation.map
@[simp]
theorem Orientation.map_apply (e : M ≃ₗ[R] N) (v : M [⋀^ι]→ₗ[R] R) (hv : v ≠ 0) :
Orientation.map ι e (rayOfNeZero _ v hv) =
rayOfNeZero _ (v.compLinearMap e.symm) (mt (v.compLinearEquiv_eq_zero_iff e.symm).mp hv) :=
rfl
#align orientation.map_apply Orientation.map_apply
@[simp]
| Mathlib/LinearAlgebra/Orientation.lean | 74 | 75 | theorem Orientation.map_refl : (Orientation.map ι <| LinearEquiv.refl R M) = Equiv.refl _ := by |
rw [Orientation.map, AlternatingMap.domLCongr_refl, Module.Ray.map_refl]
|
/-
Copyright (c) 2022 David Kurniadi Angdinata. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: David Kurniadi Angdinata
-/
import Mathlib.Algebra.Polynomial.Splits
#align_import algebra.cubic_discriminant from "leanprover-community/mathlib"@"930133160e24036d5242039fe4972407cd4f1222"
/-!
# Cubics and discriminants
This file defines cubic polynomials over a semiring and their discriminants over a splitting field.
## Main definitions
* `Cubic`: the structure representing a cubic polynomial.
* `Cubic.disc`: the discriminant of a cubic polynomial.
## Main statements
* `Cubic.disc_ne_zero_iff_roots_nodup`: the cubic discriminant is not equal to zero if and only if
the cubic has no duplicate roots.
## References
* https://en.wikipedia.org/wiki/Cubic_equation
* https://en.wikipedia.org/wiki/Discriminant
## Tags
cubic, discriminant, polynomial, root
-/
noncomputable section
/-- The structure representing a cubic polynomial. -/
@[ext]
structure Cubic (R : Type*) where
(a b c d : R)
#align cubic Cubic
namespace Cubic
open Cubic Polynomial
open Polynomial
variable {R S F K : Type*}
instance [Inhabited R] : Inhabited (Cubic R) :=
⟨⟨default, default, default, default⟩⟩
instance [Zero R] : Zero (Cubic R) :=
⟨⟨0, 0, 0, 0⟩⟩
section Basic
variable {P Q : Cubic R} {a b c d a' b' c' d' : R} [Semiring R]
/-- Convert a cubic polynomial to a polynomial. -/
def toPoly (P : Cubic R) : R[X] :=
C P.a * X ^ 3 + C P.b * X ^ 2 + C P.c * X + C P.d
#align cubic.to_poly Cubic.toPoly
theorem C_mul_prod_X_sub_C_eq [CommRing S] {w x y z : S} :
C w * (X - C x) * (X - C y) * (X - C z) =
toPoly ⟨w, w * -(x + y + z), w * (x * y + x * z + y * z), w * -(x * y * z)⟩ := by
simp only [toPoly, C_neg, C_add, C_mul]
ring1
set_option linter.uppercaseLean3 false in
#align cubic.C_mul_prod_X_sub_C_eq Cubic.C_mul_prod_X_sub_C_eq
theorem prod_X_sub_C_eq [CommRing S] {x y z : S} :
(X - C x) * (X - C y) * (X - C z) =
toPoly ⟨1, -(x + y + z), x * y + x * z + y * z, -(x * y * z)⟩ := by
rw [← one_mul <| X - C x, ← C_1, C_mul_prod_X_sub_C_eq, one_mul, one_mul, one_mul]
set_option linter.uppercaseLean3 false in
#align cubic.prod_X_sub_C_eq Cubic.prod_X_sub_C_eq
/-! ### Coefficients -/
section Coeff
private theorem coeffs : (∀ n > 3, P.toPoly.coeff n = 0) ∧ P.toPoly.coeff 3 = P.a ∧
P.toPoly.coeff 2 = P.b ∧ P.toPoly.coeff 1 = P.c ∧ P.toPoly.coeff 0 = P.d := by
simp only [toPoly, coeff_add, coeff_C, coeff_C_mul_X, coeff_C_mul_X_pow]
set_option tactic.skipAssignedInstances false in norm_num
intro n hn
repeat' rw [if_neg]
any_goals linarith only [hn]
repeat' rw [zero_add]
@[simp]
theorem coeff_eq_zero {n : ℕ} (hn : 3 < n) : P.toPoly.coeff n = 0 :=
coeffs.1 n hn
#align cubic.coeff_eq_zero Cubic.coeff_eq_zero
@[simp]
theorem coeff_eq_a : P.toPoly.coeff 3 = P.a :=
coeffs.2.1
#align cubic.coeff_eq_a Cubic.coeff_eq_a
@[simp]
theorem coeff_eq_b : P.toPoly.coeff 2 = P.b :=
coeffs.2.2.1
#align cubic.coeff_eq_b Cubic.coeff_eq_b
@[simp]
theorem coeff_eq_c : P.toPoly.coeff 1 = P.c :=
coeffs.2.2.2.1
#align cubic.coeff_eq_c Cubic.coeff_eq_c
@[simp]
theorem coeff_eq_d : P.toPoly.coeff 0 = P.d :=
coeffs.2.2.2.2
#align cubic.coeff_eq_d Cubic.coeff_eq_d
theorem a_of_eq (h : P.toPoly = Q.toPoly) : P.a = Q.a := by rw [← coeff_eq_a, h, coeff_eq_a]
#align cubic.a_of_eq Cubic.a_of_eq
theorem b_of_eq (h : P.toPoly = Q.toPoly) : P.b = Q.b := by rw [← coeff_eq_b, h, coeff_eq_b]
#align cubic.b_of_eq Cubic.b_of_eq
theorem c_of_eq (h : P.toPoly = Q.toPoly) : P.c = Q.c := by rw [← coeff_eq_c, h, coeff_eq_c]
#align cubic.c_of_eq Cubic.c_of_eq
| Mathlib/Algebra/CubicDiscriminant.lean | 130 | 130 | theorem d_of_eq (h : P.toPoly = Q.toPoly) : P.d = Q.d := by | rw [← coeff_eq_d, h, coeff_eq_d]
|
/-
Copyright (c) 2017 Kevin Buzzard. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kevin Buzzard, Mario Carneiro
-/
import Mathlib.Data.Complex.Basic
import Mathlib.Data.Real.Sqrt
#align_import data.complex.basic from "leanprover-community/mathlib"@"31c24aa72e7b3e5ed97a8412470e904f82b81004"
/-!
# Absolute values of complex numbers
-/
open Set ComplexConjugate
namespace Complex
/-! ### Absolute value -/
namespace AbsTheory
-- We develop enough theory to bundle `abs` into an `AbsoluteValue` before making things public;
-- this is so there's not two versions of it hanging around.
local notation "abs" z => Real.sqrt (normSq z)
private theorem mul_self_abs (z : ℂ) : ((abs z) * abs z) = normSq z :=
Real.mul_self_sqrt (normSq_nonneg _)
private theorem abs_nonneg' (z : ℂ) : 0 ≤ abs z :=
Real.sqrt_nonneg _
theorem abs_conj (z : ℂ) : (abs conj z) = abs z := by simp
#align complex.abs_theory.abs_conj Complex.AbsTheory.abs_conj
private theorem abs_re_le_abs (z : ℂ) : |z.re| ≤ abs z := by
rw [mul_self_le_mul_self_iff (abs_nonneg z.re) (abs_nonneg' _), abs_mul_abs_self, mul_self_abs]
apply re_sq_le_normSq
private theorem re_le_abs (z : ℂ) : z.re ≤ abs z :=
(abs_le.1 (abs_re_le_abs _)).2
private theorem abs_mul (z w : ℂ) : (abs z * w) = (abs z) * abs w := by
rw [normSq_mul, Real.sqrt_mul (normSq_nonneg _)]
private theorem abs_add (z w : ℂ) : (abs z + w) ≤ (abs z) + abs w :=
(mul_self_le_mul_self_iff (abs_nonneg' (z + w))
(add_nonneg (abs_nonneg' z) (abs_nonneg' w))).2 <| by
rw [mul_self_abs, add_mul_self_eq, mul_self_abs, mul_self_abs, add_right_comm, normSq_add,
add_le_add_iff_left, mul_assoc, mul_le_mul_left (zero_lt_two' ℝ), ←
Real.sqrt_mul <| normSq_nonneg z, ← normSq_conj w, ← map_mul]
exact re_le_abs (z * conj w)
/-- The complex absolute value function, defined as the square root of the norm squared. -/
noncomputable def _root_.Complex.abs : AbsoluteValue ℂ ℝ where
toFun x := abs x
map_mul' := abs_mul
nonneg' := abs_nonneg'
eq_zero' _ := (Real.sqrt_eq_zero <| normSq_nonneg _).trans normSq_eq_zero
add_le' := abs_add
#align complex.abs Complex.abs
end AbsTheory
theorem abs_def : (Complex.abs : ℂ → ℝ) = fun z => (normSq z).sqrt :=
rfl
#align complex.abs_def Complex.abs_def
theorem abs_apply {z : ℂ} : Complex.abs z = (normSq z).sqrt :=
rfl
#align complex.abs_apply Complex.abs_apply
@[simp, norm_cast]
theorem abs_ofReal (r : ℝ) : Complex.abs r = |r| := by
simp [Complex.abs, normSq_ofReal, Real.sqrt_mul_self_eq_abs]
#align complex.abs_of_real Complex.abs_ofReal
nonrec theorem abs_of_nonneg {r : ℝ} (h : 0 ≤ r) : Complex.abs r = r :=
(Complex.abs_ofReal _).trans (abs_of_nonneg h)
#align complex.abs_of_nonneg Complex.abs_of_nonneg
-- Porting note: removed `norm_cast` attribute because the RHS can't start with `↑`
@[simp]
theorem abs_natCast (n : ℕ) : Complex.abs n = n := Complex.abs_of_nonneg (Nat.cast_nonneg n)
#align complex.abs_of_nat Complex.abs_natCast
#align complex.abs_cast_nat Complex.abs_natCast
-- See note [no_index around OfNat.ofNat]
@[simp]
theorem abs_ofNat (n : ℕ) [n.AtLeastTwo] :
Complex.abs (no_index (OfNat.ofNat n : ℂ)) = OfNat.ofNat n :=
abs_natCast n
theorem mul_self_abs (z : ℂ) : Complex.abs z * Complex.abs z = normSq z :=
Real.mul_self_sqrt (normSq_nonneg _)
#align complex.mul_self_abs Complex.mul_self_abs
theorem sq_abs (z : ℂ) : Complex.abs z ^ 2 = normSq z :=
Real.sq_sqrt (normSq_nonneg _)
#align complex.sq_abs Complex.sq_abs
@[simp]
| Mathlib/Data/Complex/Abs.lean | 104 | 105 | theorem sq_abs_sub_sq_re (z : ℂ) : Complex.abs z ^ 2 - z.re ^ 2 = z.im ^ 2 := by |
rw [sq_abs, normSq_apply, ← sq, ← sq, add_sub_cancel_left]
|
/-
Copyright (c) 2021 Yury G. Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury G. Kudryashov
-/
import Mathlib.Data.Real.Irrational
import Mathlib.Data.Rat.Encodable
import Mathlib.Topology.GDelta
#align_import topology.instances.irrational from "leanprover-community/mathlib"@"f2ce6086713c78a7f880485f7917ea547a215982"
/-!
# Topology of irrational numbers
In this file we prove the following theorems:
* `IsGδ.setOf_irrational`, `dense_irrational`, `eventually_residual_irrational`: irrational numbers
form a dense Gδ set;
* `Irrational.eventually_forall_le_dist_cast_div`,
`Irrational.eventually_forall_le_dist_cast_div_of_denom_le`;
`Irrational.eventually_forall_le_dist_cast_rat_of_denom_le`: a sufficiently small neighborhood of
an irrational number is disjoint with the set of rational numbers with bounded denominator.
We also provide `OrderTopology`, `NoMinOrder`, `NoMaxOrder`, and `DenselyOrdered`
instances for `{x // Irrational x}`.
## Tags
irrational, residual
-/
open Set Filter Metric
open Filter Topology
protected theorem IsGδ.setOf_irrational : IsGδ { x | Irrational x } :=
(countable_range _).isGδ_compl
set_option linter.uppercaseLean3 false in
#align is_Gδ_irrational IsGδ.setOf_irrational
@[deprecated (since := "2024-02-15")] alias isGδ_irrational := IsGδ.setOf_irrational
| Mathlib/Topology/Instances/Irrational.lean | 45 | 51 | theorem dense_irrational : Dense { x : ℝ | Irrational x } := by |
refine Real.isTopologicalBasis_Ioo_rat.dense_iff.2 ?_
simp only [gt_iff_lt, Rat.cast_lt, not_lt, ge_iff_le, Rat.cast_le, mem_iUnion, mem_singleton_iff,
exists_prop, forall_exists_index, and_imp]
rintro _ a b hlt rfl _
rw [inter_comm]
exact exists_irrational_btwn (Rat.cast_lt.2 hlt)
|
/-
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
| Mathlib/Analysis/NormedSpace/Pointwise.lean | 53 | 54 | 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]
|
/-
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.LinearAlgebra.AffineSpace.AffineMap
import Mathlib.Topology.Algebra.Group.Basic
import Mathlib.Topology.Algebra.MulAction
#align_import topology.algebra.affine from "leanprover-community/mathlib"@"717c073262cd9d59b1a1dcda7e8ab570c5b63370"
/-!
# Topological properties of affine spaces and maps
For now, this contains only a few facts regarding the continuity of affine maps in the special
case when the point space and vector space are the same.
TODO: Deal with the case where the point spaces are different from the vector spaces. Note that
we do have some results in this direction under the assumption that the topologies are induced by
(semi)norms.
-/
namespace AffineMap
variable {R E F : Type*}
variable [AddCommGroup E] [TopologicalSpace E]
variable [AddCommGroup F] [TopologicalSpace F] [TopologicalAddGroup F]
section Ring
variable [Ring R] [Module R E] [Module R F]
/-- An affine map is continuous iff its underlying linear map is continuous. See also
`AffineMap.continuous_linear_iff`. -/
theorem continuous_iff {f : E →ᵃ[R] F} : Continuous f ↔ Continuous f.linear := by
constructor
· intro hc
rw [decomp' f]
exact hc.sub continuous_const
· intro hc
rw [decomp f]
exact hc.add continuous_const
#align affine_map.continuous_iff AffineMap.continuous_iff
/-- The line map is continuous. -/
@[continuity]
theorem lineMap_continuous [TopologicalSpace R] [ContinuousSMul R F] {p v : F} :
Continuous (lineMap p v : R →ᵃ[R] F) :=
continuous_iff.mpr <|
(continuous_id.smul continuous_const).add <| @continuous_const _ _ _ _ (0 : F)
#align affine_map.line_map_continuous AffineMap.lineMap_continuous
end Ring
section CommRing
variable [CommRing R] [Module R F] [ContinuousConstSMul R F]
@[continuity]
theorem homothety_continuous (x : F) (t : R) : Continuous <| homothety x t := by
suffices ⇑(homothety x t) = fun y => t • (y - x) + x by
rw [this]
exact ((continuous_id.sub continuous_const).const_smul _).add continuous_const
-- Porting note: proof was `by continuity`
ext y
simp [homothety_apply]
#align affine_map.homothety_continuous AffineMap.homothety_continuous
end CommRing
section Field
variable [Field R] [Module R F] [ContinuousConstSMul R F]
| Mathlib/Topology/Algebra/Affine.lean | 76 | 78 | theorem homothety_isOpenMap (x : F) (t : R) (ht : t ≠ 0) : IsOpenMap <| homothety x t := by |
apply IsOpenMap.of_inverse (homothety_continuous x t⁻¹) <;> intro e <;>
simp [← AffineMap.comp_apply, ← homothety_mul, ht]
|
/-
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.Multiset.Basic
#align_import data.multiset.range from "leanprover-community/mathlib"@"0a0ec35061ed9960bf0e7ffb0335f44447b58977"
/-! # `Multiset.range n` gives `{0, 1, ..., n-1}` as a multiset. -/
open List Nat
namespace Multiset
-- range
/-- `range n` is the multiset lifted from the list `range n`,
that is, the set `{0, 1, ..., n-1}`. -/
def range (n : ℕ) : Multiset ℕ :=
List.range n
#align multiset.range Multiset.range
theorem coe_range (n : ℕ) : ↑(List.range n) = range n :=
rfl
#align multiset.coe_range Multiset.coe_range
@[simp]
theorem range_zero : range 0 = 0 :=
rfl
#align multiset.range_zero Multiset.range_zero
@[simp]
| Mathlib/Data/Multiset/Range.lean | 34 | 35 | theorem range_succ (n : ℕ) : range (succ n) = n ::ₘ range n := by |
rw [range, List.range_succ, ← coe_add, add_comm]; rfl
|
/-
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]
| Mathlib/Analysis/NormedSpace/Pointwise.lean | 84 | 88 | 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]
|
/-
Copyright (c) 2014 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad, Leonardo de Moura
-/
import Mathlib.Algebra.GroupWithZero.Divisibility
import Mathlib.Algebra.Order.Ring.Nat
import Mathlib.Tactic.NthRewrite
#align_import data.nat.gcd.basic from "leanprover-community/mathlib"@"e8638a0fcaf73e4500469f368ef9494e495099b3"
/-!
# Definitions and properties of `Nat.gcd`, `Nat.lcm`, and `Nat.coprime`
Generalizations of these are provided in a later file as `GCDMonoid.gcd` and
`GCDMonoid.lcm`.
Note that the global `IsCoprime` is not a straightforward generalization of `Nat.coprime`, see
`Nat.isCoprime_iff_coprime` for the connection between the two.
-/
namespace Nat
/-! ### `gcd` -/
theorem gcd_greatest {a b d : ℕ} (hda : d ∣ a) (hdb : d ∣ b) (hd : ∀ e : ℕ, e ∣ a → e ∣ b → e ∣ d) :
d = a.gcd b :=
(dvd_antisymm (hd _ (gcd_dvd_left a b) (gcd_dvd_right a b)) (dvd_gcd hda hdb)).symm
#align nat.gcd_greatest Nat.gcd_greatest
/-! Lemmas where one argument consists of addition of a multiple of the other -/
@[simp]
theorem gcd_add_mul_right_right (m n k : ℕ) : gcd m (n + k * m) = gcd m n := by
simp [gcd_rec m (n + k * m), gcd_rec m n]
#align nat.gcd_add_mul_right_right Nat.gcd_add_mul_right_right
@[simp]
theorem gcd_add_mul_left_right (m n k : ℕ) : gcd m (n + m * k) = gcd m n := by
simp [gcd_rec m (n + m * k), gcd_rec m n]
#align nat.gcd_add_mul_left_right Nat.gcd_add_mul_left_right
@[simp]
theorem gcd_mul_right_add_right (m n k : ℕ) : gcd m (k * m + n) = gcd m n := by simp [add_comm _ n]
#align nat.gcd_mul_right_add_right Nat.gcd_mul_right_add_right
@[simp]
theorem gcd_mul_left_add_right (m n k : ℕ) : gcd m (m * k + n) = gcd m n := by simp [add_comm _ n]
#align nat.gcd_mul_left_add_right Nat.gcd_mul_left_add_right
@[simp]
| Mathlib/Data/Nat/GCD/Basic.lean | 53 | 54 | theorem gcd_add_mul_right_left (m n k : ℕ) : gcd (m + k * n) n = gcd m n := by |
rw [gcd_comm, gcd_add_mul_right_right, gcd_comm]
|
/-
Copyright (c) 2024 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov
-/
import Batteries.Data.List.Lemmas
/-!
# Basic properties of `List.eraseIdx`
`List.eraseIdx l k` erases `k`-th element of `l : List α`.
If `k ≥ length l`, then it returns `l`.
-/
namespace List
universe u v
variable {α : Type u} {β : Type v}
@[simp] theorem eraseIdx_zero (l : List α) : eraseIdx l 0 = tail l := by cases l <;> rfl
theorem eraseIdx_eq_take_drop_succ :
∀ (l : List α) (i : Nat), l.eraseIdx i = l.take i ++ l.drop (i + 1)
| nil, _ => by simp
| a::l, 0 => by simp
| a::l, i + 1 => by simp [eraseIdx_eq_take_drop_succ l i]
theorem eraseIdx_sublist : ∀ (l : List α) (k : Nat), eraseIdx l k <+ l
| [], _ => by simp
| a::l, 0 => by simp
| a::l, k + 1 => by simp [eraseIdx_sublist l k]
theorem eraseIdx_subset (l : List α) (k : Nat) : eraseIdx l k ⊆ l := (eraseIdx_sublist l k).subset
@[simp]
theorem eraseIdx_eq_self : ∀ {l : List α} {k : Nat}, eraseIdx l k = l ↔ length l ≤ k
| [], _ => by simp
| a::l, 0 => by simp [(cons_ne_self _ _).symm]
| a::l, k + 1 => by simp [eraseIdx_eq_self]
alias ⟨_, eraseIdx_of_length_le⟩ := eraseIdx_eq_self
| .lake/packages/batteries/Batteries/Data/List/EraseIdx.lean | 43 | 47 | theorem eraseIdx_append_of_lt_length {l : List α} {k : Nat} (hk : k < length l) (l' : List α) :
eraseIdx (l ++ l') k = eraseIdx l k ++ l' := by |
rw [eraseIdx_eq_take_drop_succ, take_append_of_le_length, drop_append_of_le_length,
eraseIdx_eq_take_drop_succ, append_assoc]
all_goals omega
|
/-
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.Init.Algebra.Classes
import Mathlib.Logic.Nontrivial.Basic
import Mathlib.Order.BoundedOrder
import Mathlib.Data.Option.NAry
import Mathlib.Tactic.Lift
import Mathlib.Data.Option.Basic
#align_import order.with_bot from "leanprover-community/mathlib"@"0111834459f5d7400215223ea95ae38a1265a907"
/-!
# `WithBot`, `WithTop`
Adding a `bot` or a `top` to an order.
## Main declarations
* `With<Top/Bot> α`: Equips `Option α` with the order on `α` plus `none` as the top/bottom element.
-/
variable {α β γ δ : Type*}
/-- Attach `⊥` to a type. -/
def WithBot (α : Type*) :=
Option α
#align with_bot WithBot
namespace WithBot
variable {a b : α}
instance [Repr α] : Repr (WithBot α) :=
⟨fun o _ =>
match o with
| none => "⊥"
| some a => "↑" ++ repr a⟩
/-- The canonical map from `α` into `WithBot α` -/
@[coe, match_pattern] def some : α → WithBot α :=
Option.some
-- Porting note: changed this from `CoeTC` to `Coe` but I am not 100% confident that's correct.
instance coe : Coe α (WithBot α) :=
⟨some⟩
instance bot : Bot (WithBot α) :=
⟨none⟩
instance inhabited : Inhabited (WithBot α) :=
⟨⊥⟩
instance nontrivial [Nonempty α] : Nontrivial (WithBot α) :=
Option.nontrivial
open Function
theorem coe_injective : Injective ((↑) : α → WithBot α) :=
Option.some_injective _
#align with_bot.coe_injective WithBot.coe_injective
@[simp, norm_cast]
theorem coe_inj : (a : WithBot α) = b ↔ a = b :=
Option.some_inj
#align with_bot.coe_inj WithBot.coe_inj
protected theorem «forall» {p : WithBot α → Prop} : (∀ x, p x) ↔ p ⊥ ∧ ∀ x : α, p x :=
Option.forall
#align with_bot.forall WithBot.forall
protected theorem «exists» {p : WithBot α → Prop} : (∃ x, p x) ↔ p ⊥ ∨ ∃ x : α, p x :=
Option.exists
#align with_bot.exists WithBot.exists
theorem none_eq_bot : (none : WithBot α) = (⊥ : WithBot α) :=
rfl
#align with_bot.none_eq_bot WithBot.none_eq_bot
theorem some_eq_coe (a : α) : (Option.some a : WithBot α) = (↑a : WithBot α) :=
rfl
#align with_bot.some_eq_coe WithBot.some_eq_coe
@[simp]
theorem bot_ne_coe : ⊥ ≠ (a : WithBot α) :=
nofun
#align with_bot.bot_ne_coe WithBot.bot_ne_coe
@[simp]
theorem coe_ne_bot : (a : WithBot α) ≠ ⊥ :=
nofun
#align with_bot.coe_ne_bot WithBot.coe_ne_bot
/-- Recursor for `WithBot` using the preferred forms `⊥` and `↑a`. -/
@[elab_as_elim, induction_eliminator, cases_eliminator]
def recBotCoe {C : WithBot α → Sort*} (bot : C ⊥) (coe : ∀ a : α, C a) : ∀ n : WithBot α, C n
| ⊥ => bot
| (a : α) => coe a
#align with_bot.rec_bot_coe WithBot.recBotCoe
@[simp]
theorem recBotCoe_bot {C : WithBot α → Sort*} (d : C ⊥) (f : ∀ a : α, C a) :
@recBotCoe _ C d f ⊥ = d :=
rfl
#align with_bot.rec_bot_coe_bot WithBot.recBotCoe_bot
@[simp]
theorem recBotCoe_coe {C : WithBot α → Sort*} (d : C ⊥) (f : ∀ a : α, C a) (x : α) :
@recBotCoe _ C d f ↑x = f x :=
rfl
#align with_bot.rec_bot_coe_coe WithBot.recBotCoe_coe
/-- Specialization of `Option.getD` to values in `WithBot α` that respects API boundaries.
-/
def unbot' (d : α) (x : WithBot α) : α :=
recBotCoe d id x
#align with_bot.unbot' WithBot.unbot'
@[simp]
theorem unbot'_bot {α} (d : α) : unbot' d ⊥ = d :=
rfl
#align with_bot.unbot'_bot WithBot.unbot'_bot
@[simp]
theorem unbot'_coe {α} (d x : α) : unbot' d x = x :=
rfl
#align with_bot.unbot'_coe WithBot.unbot'_coe
theorem coe_eq_coe : (a : WithBot α) = b ↔ a = b := coe_inj
#align with_bot.coe_eq_coe WithBot.coe_eq_coe
theorem unbot'_eq_iff {d y : α} {x : WithBot α} : unbot' d x = y ↔ x = y ∨ x = ⊥ ∧ y = d := by
induction x <;> simp [@eq_comm _ d]
#align with_bot.unbot'_eq_iff WithBot.unbot'_eq_iff
@[simp] theorem unbot'_eq_self_iff {d : α} {x : WithBot α} : unbot' d x = d ↔ x = d ∨ x = ⊥ := by
simp [unbot'_eq_iff]
#align with_bot.unbot'_eq_self_iff WithBot.unbot'_eq_self_iff
| Mathlib/Order/WithBot.lean | 143 | 145 | theorem unbot'_eq_unbot'_iff {d : α} {x y : WithBot α} :
unbot' d x = unbot' d y ↔ x = y ∨ x = d ∧ y = ⊥ ∨ x = ⊥ ∧ y = d := by |
induction y <;> simp [unbot'_eq_iff, or_comm]
|
/-
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.LinearAlgebra.CliffordAlgebra.Fold
import Mathlib.LinearAlgebra.ExteriorAlgebra.Basic
#align_import linear_algebra.exterior_algebra.of_alternating from "leanprover-community/mathlib"@"ce11c3c2a285bbe6937e26d9792fda4e51f3fe1a"
/-!
# Extending an alternating map to the exterior algebra
## Main definitions
* `ExteriorAlgebra.liftAlternating`: construct a linear map out of the exterior algebra
given alternating maps (corresponding to maps out of the exterior powers).
* `ExteriorAlgebra.liftAlternatingEquiv`: the above as a linear equivalence
## Main results
* `ExteriorAlgebra.lhom_ext`: linear maps from the exterior algebra agree if they agree on the
exterior powers.
-/
variable {R M N N' : Type*}
variable [CommRing R] [AddCommGroup M] [AddCommGroup N] [AddCommGroup N']
variable [Module R M] [Module R N] [Module R N']
-- This instance can't be found where it's needed if we don't remind lean that it exists.
instance AlternatingMap.instModuleAddCommGroup {ι : Type*} :
Module R (M [⋀^ι]→ₗ[R] N) := by
infer_instance
#align alternating_map.module_add_comm_group AlternatingMap.instModuleAddCommGroup
namespace ExteriorAlgebra
open CliffordAlgebra hiding ι
/-- Build a map out of the exterior algebra given a collection of alternating maps acting on each
exterior power -/
def liftAlternating : (∀ i, M [⋀^Fin i]→ₗ[R] N) →ₗ[R] ExteriorAlgebra R M →ₗ[R] N := by
suffices
(∀ i, M [⋀^Fin i]→ₗ[R] N) →ₗ[R]
ExteriorAlgebra R M →ₗ[R] ∀ i, M [⋀^Fin i]→ₗ[R] N by
refine LinearMap.compr₂ this ?_
refine (LinearEquiv.toLinearMap ?_).comp (LinearMap.proj 0)
exact AlternatingMap.constLinearEquivOfIsEmpty.symm
refine CliffordAlgebra.foldl _ ?_ ?_
· refine
LinearMap.mk₂ R (fun m f i => (f i.succ).curryLeft m) (fun m₁ m₂ f => ?_) (fun c m f => ?_)
(fun m f₁ f₂ => ?_) fun c m f => ?_
all_goals
ext i : 1
simp only [map_smul, map_add, Pi.add_apply, Pi.smul_apply, AlternatingMap.curryLeft_add,
AlternatingMap.curryLeft_smul, map_add, map_smul, LinearMap.add_apply, LinearMap.smul_apply]
· -- when applied twice with the same `m`, this recursive step produces 0
intro m x
dsimp only [LinearMap.mk₂_apply, QuadraticForm.coeFn_zero, Pi.zero_apply]
simp_rw [zero_smul]
ext i : 1
exact AlternatingMap.curryLeft_same _ _
#align exterior_algebra.lift_alternating ExteriorAlgebra.liftAlternating
@[simp]
theorem liftAlternating_ι (f : ∀ i, M [⋀^Fin i]→ₗ[R] N) (m : M) :
liftAlternating (R := R) (M := M) (N := N) f (ι R m) = f 1 ![m] := by
dsimp [liftAlternating]
rw [foldl_ι, LinearMap.mk₂_apply, AlternatingMap.curryLeft_apply_apply]
congr
-- Porting note: In Lean 3, `congr` could use the `[Subsingleton (Fin 0 → M)]` instance to finish
-- the proof. Here, the instance can be synthesized but `congr` does not use it so the following
-- line is provided.
rw [Matrix.zero_empty]
#align exterior_algebra.lift_alternating_ι ExteriorAlgebra.liftAlternating_ι
theorem liftAlternating_ι_mul (f : ∀ i, M [⋀^Fin i]→ₗ[R] N) (m : M)
(x : ExteriorAlgebra R M) :
liftAlternating (R := R) (M := M) (N := N) f (ι R m * x) =
liftAlternating (R := R) (M := M) (N := N) (fun i => (f i.succ).curryLeft m) x := by
dsimp [liftAlternating]
rw [foldl_mul, foldl_ι]
rfl
#align exterior_algebra.lift_alternating_ι_mul ExteriorAlgebra.liftAlternating_ι_mul
@[simp]
| Mathlib/LinearAlgebra/ExteriorAlgebra/OfAlternating.lean | 89 | 92 | theorem liftAlternating_one (f : ∀ i, M [⋀^Fin i]→ₗ[R] N) :
liftAlternating (R := R) (M := M) (N := N) f (1 : ExteriorAlgebra R M) = f 0 0 := by |
dsimp [liftAlternating]
rw [foldl_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.Algebra.Hom
import Mathlib.RingTheory.Ideal.Quotient
#align_import algebra.ring_quot from "leanprover-community/mathlib"@"e5820f6c8fcf1b75bcd7738ae4da1c5896191f72"
/-!
# Quotients of non-commutative rings
Unfortunately, ideals have only been developed in the commutative case as `Ideal`,
and it's not immediately clear how one should formalise ideals in the non-commutative case.
In this file, we directly define the quotient of a semiring by any relation,
by building a bigger relation that represents the ideal generated by that relation.
We prove the universal properties of the quotient, and recommend avoiding relying on the actual
definition, which is made irreducible for this purpose.
Since everything runs in parallel for quotients of `R`-algebras, we do that case at the same time.
-/
universe uR uS uT uA u₄
variable {R : Type uR} [Semiring R]
variable {S : Type uS} [CommSemiring S]
variable {T : Type uT}
variable {A : Type uA} [Semiring A] [Algebra S A]
namespace RingCon
instance (c : RingCon A) : Algebra S c.Quotient where
smul := (· • ·)
toRingHom := c.mk'.comp (algebraMap S A)
commutes' _ := Quotient.ind' fun _ ↦ congr_arg Quotient.mk'' <| Algebra.commutes _ _
smul_def' _ := Quotient.ind' fun _ ↦ congr_arg Quotient.mk'' <| Algebra.smul_def _ _
@[simp, norm_cast]
theorem coe_algebraMap (c : RingCon A) (s : S) :
(algebraMap S A s : c.Quotient) = algebraMap S _ s :=
rfl
#align ring_con.coe_algebra_map RingCon.coe_algebraMap
end RingCon
namespace RingQuot
/-- Given an arbitrary relation `r` on a ring, we strengthen it to a relation `Rel r`,
such that the equivalence relation generated by `Rel r` has `x ~ y` if and only if
`x - y` is in the ideal generated by elements `a - b` such that `r a b`.
-/
inductive Rel (r : R → R → Prop) : R → R → Prop
| of ⦃x y : R⦄ (h : r x y) : Rel r x y
| add_left ⦃a b c⦄ : Rel r a b → Rel r (a + c) (b + c)
| mul_left ⦃a b c⦄ : Rel r a b → Rel r (a * c) (b * c)
| mul_right ⦃a b c⦄ : Rel r b c → Rel r (a * b) (a * c)
#align ring_quot.rel RingQuot.Rel
theorem Rel.add_right {r : R → R → Prop} ⦃a b c : R⦄ (h : Rel r b c) : Rel r (a + b) (a + c) := by
rw [add_comm a b, add_comm a c]
exact Rel.add_left h
#align ring_quot.rel.add_right RingQuot.Rel.add_right
theorem Rel.neg {R : Type uR} [Ring R] {r : R → R → Prop} ⦃a b : R⦄ (h : Rel r a b) :
Rel r (-a) (-b) := by simp only [neg_eq_neg_one_mul a, neg_eq_neg_one_mul b, Rel.mul_right h]
#align ring_quot.rel.neg RingQuot.Rel.neg
theorem Rel.sub_left {R : Type uR} [Ring R] {r : R → R → Prop} ⦃a b c : R⦄ (h : Rel r a b) :
Rel r (a - c) (b - c) := by simp only [sub_eq_add_neg, h.add_left]
#align ring_quot.rel.sub_left RingQuot.Rel.sub_left
theorem Rel.sub_right {R : Type uR} [Ring R] {r : R → R → Prop} ⦃a b c : R⦄ (h : Rel r b c) :
Rel r (a - b) (a - c) := by simp only [sub_eq_add_neg, h.neg.add_right]
#align ring_quot.rel.sub_right RingQuot.Rel.sub_right
| Mathlib/Algebra/RingQuot.lean | 79 | 80 | theorem Rel.smul {r : A → A → Prop} (k : S) ⦃a b : A⦄ (h : Rel r a b) : Rel r (k • a) (k • b) := by |
simp only [Algebra.smul_def, Rel.mul_right h]
|
/-
Copyright (c) 2022 Kyle Miller. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kyle Miller
-/
import Mathlib.SetTheory.Cardinal.Finite
#align_import data.finite.card from "leanprover-community/mathlib"@"3ff3f2d6a3118b8711063de7111a0d77a53219a8"
/-!
# Cardinality of finite types
The cardinality of a finite type `α` is given by `Nat.card α`. This function has
the "junk value" of `0` for infinite types, but to ensure the function has valid
output, one just needs to know that it's possible to produce a `Finite` instance
for the type. (Note: we could have defined a `Finite.card` that required you to
supply a `Finite` instance, but (a) the function would be `noncomputable` anyway
so there is no need to supply the instance and (b) the function would have a more
complicated dependent type that easily leads to "motive not type correct" errors.)
## Implementation notes
Theorems about `Nat.card` are sometimes incidentally true for both finite and infinite
types. If removing a finiteness constraint results in no loss in legibility, we remove
it. We generally put such theorems into the `SetTheory.Cardinal.Finite` module.
-/
noncomputable section
open scoped Classical
variable {α β γ : Type*}
/-- There is (noncomputably) an equivalence between a finite type `α` and `Fin (Nat.card α)`. -/
def Finite.equivFin (α : Type*) [Finite α] : α ≃ Fin (Nat.card α) := by
have := (Finite.exists_equiv_fin α).choose_spec.some
rwa [Nat.card_eq_of_equiv_fin this]
#align finite.equiv_fin Finite.equivFin
/-- Similar to `Finite.equivFin` but with control over the term used for the cardinality. -/
def Finite.equivFinOfCardEq [Finite α] {n : ℕ} (h : Nat.card α = n) : α ≃ Fin n := by
subst h
apply Finite.equivFin
#align finite.equiv_fin_of_card_eq Finite.equivFinOfCardEq
theorem Nat.card_eq (α : Type*) :
Nat.card α = if h : Finite α then @Fintype.card α (Fintype.ofFinite α) else 0 := by
cases finite_or_infinite α
· letI := Fintype.ofFinite α
simp only [*, Nat.card_eq_fintype_card, dif_pos]
· simp only [*, card_eq_zero_of_infinite, not_finite_iff_infinite.mpr, dite_false]
#align nat.card_eq Nat.card_eq
theorem Finite.card_pos_iff [Finite α] : 0 < Nat.card α ↔ Nonempty α := by
haveI := Fintype.ofFinite α
rw [Nat.card_eq_fintype_card, Fintype.card_pos_iff]
#align finite.card_pos_iff Finite.card_pos_iff
theorem Finite.card_pos [Finite α] [h : Nonempty α] : 0 < Nat.card α :=
Finite.card_pos_iff.mpr h
#align finite.card_pos Finite.card_pos
namespace Finite
theorem cast_card_eq_mk {α : Type*} [Finite α] : ↑(Nat.card α) = Cardinal.mk α :=
Cardinal.cast_toNat_of_lt_aleph0 (Cardinal.lt_aleph0_of_finite α)
#align finite.cast_card_eq_mk Finite.cast_card_eq_mk
theorem card_eq [Finite α] [Finite β] : Nat.card α = Nat.card β ↔ Nonempty (α ≃ β) := by
haveI := Fintype.ofFinite α
haveI := Fintype.ofFinite β
simp only [Nat.card_eq_fintype_card, Fintype.card_eq]
#align finite.card_eq Finite.card_eq
| Mathlib/Data/Finite/Card.lean | 78 | 80 | theorem card_le_one_iff_subsingleton [Finite α] : Nat.card α ≤ 1 ↔ Subsingleton α := by |
haveI := Fintype.ofFinite α
simp only [Nat.card_eq_fintype_card, Fintype.card_le_one_iff_subsingleton]
|
/-
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.Polynomial.Degree.Definitions
import Mathlib.Algebra.Polynomial.Eval
import Mathlib.Algebra.Polynomial.Monic
import Mathlib.Algebra.Polynomial.RingDivision
import Mathlib.Tactic.Abel
#align_import ring_theory.polynomial.pochhammer from "leanprover-community/mathlib"@"53b216bcc1146df1c4a0a86877890ea9f1f01589"
/-!
# The Pochhammer polynomials
We define and prove some basic relations about
`ascPochhammer S n : S[X] := X * (X + 1) * ... * (X + n - 1)`
which is also known as the rising factorial and about
`descPochhammer R n : R[X] := X * (X - 1) * ... * (X - n + 1)`
which is also known as the falling factorial. Versions of this definition
that are focused on `Nat` can be found in `Data.Nat.Factorial` as `Nat.ascFactorial` and
`Nat.descFactorial`.
## Implementation
As with many other families of polynomials, even though the coefficients are always in `ℕ` or `ℤ` ,
we define the polynomial with coefficients in any `[Semiring S]` or `[Ring R]`.
## TODO
There is lots more in this direction:
* q-factorials, q-binomials, q-Pochhammer.
-/
universe u v
open Polynomial
open Polynomial
section Semiring
variable (S : Type u) [Semiring S]
/-- `ascPochhammer S n` is the polynomial `X * (X + 1) * ... * (X + n - 1)`,
with coefficients in the semiring `S`.
-/
noncomputable def ascPochhammer : ℕ → S[X]
| 0 => 1
| n + 1 => X * (ascPochhammer n).comp (X + 1)
#align pochhammer ascPochhammer
@[simp]
theorem ascPochhammer_zero : ascPochhammer S 0 = 1 :=
rfl
#align pochhammer_zero ascPochhammer_zero
@[simp]
theorem ascPochhammer_one : ascPochhammer S 1 = X := by simp [ascPochhammer]
#align pochhammer_one ascPochhammer_one
theorem ascPochhammer_succ_left (n : ℕ) :
ascPochhammer S (n + 1) = X * (ascPochhammer S n).comp (X + 1) := by
rw [ascPochhammer]
#align pochhammer_succ_left ascPochhammer_succ_left
theorem monic_ascPochhammer (n : ℕ) [Nontrivial S] [NoZeroDivisors S] :
Monic <| ascPochhammer S n := by
induction' n with n hn
· simp
· have : leadingCoeff (X + 1 : S[X]) = 1 := leadingCoeff_X_add_C 1
rw [ascPochhammer_succ_left, Monic.def, leadingCoeff_mul,
leadingCoeff_comp (ne_zero_of_eq_one <| natDegree_X_add_C 1 : natDegree (X + 1) ≠ 0), hn,
monic_X, one_mul, one_mul, this, one_pow]
section
variable {S} {T : Type v} [Semiring T]
@[simp]
theorem ascPochhammer_map (f : S →+* T) (n : ℕ) :
(ascPochhammer S n).map f = ascPochhammer T n := by
induction' n with n ih
· simp
· simp [ih, ascPochhammer_succ_left, map_comp]
#align pochhammer_map ascPochhammer_map
theorem ascPochhammer_eval₂ (f : S →+* T) (n : ℕ) (t : T) :
(ascPochhammer T n).eval t = (ascPochhammer S n).eval₂ f t := by
rw [← ascPochhammer_map f]
exact eval_map f t
theorem ascPochhammer_eval_comp {R : Type*} [CommSemiring R] (n : ℕ) (p : R[X]) [Algebra R S]
(x : S) : ((ascPochhammer S n).comp (p.map (algebraMap R S))).eval x =
(ascPochhammer S n).eval (p.eval₂ (algebraMap R S) x) := by
rw [ascPochhammer_eval₂ (algebraMap R S), ← eval₂_comp', ← ascPochhammer_map (algebraMap R S),
← map_comp, eval_map]
end
@[simp, norm_cast]
| Mathlib/RingTheory/Polynomial/Pochhammer.lean | 104 | 107 | theorem ascPochhammer_eval_cast (n k : ℕ) :
(((ascPochhammer ℕ n).eval k : ℕ) : S) = ((ascPochhammer S n).eval k : S) := by |
rw [← ascPochhammer_map (algebraMap ℕ S), eval_map, ← eq_natCast (algebraMap ℕ S),
eval₂_at_natCast,Nat.cast_id]
|
/-
Copyright (c) 2022 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov
-/
import Mathlib.Analysis.Complex.Circle
import Mathlib.Analysis.NormedSpace.BallAction
#align_import analysis.complex.unit_disc.basic from "leanprover-community/mathlib"@"70fd9563a21e7b963887c9360bd29b2393e6225a"
/-!
# Poincaré disc
In this file we define `Complex.UnitDisc` to be the unit disc in the complex plane. We also
introduce some basic operations on this disc.
-/
open Set Function Metric
noncomputable section
local notation "conj'" => starRingEnd ℂ
namespace Complex
/-- Complex unit disc. -/
def UnitDisc : Type :=
ball (0 : ℂ) 1 deriving TopologicalSpace
#align complex.unit_disc Complex.UnitDisc
@[inherit_doc] scoped[UnitDisc] notation "𝔻" => Complex.UnitDisc
open UnitDisc
namespace UnitDisc
instance instCommSemigroup : CommSemigroup UnitDisc := by unfold UnitDisc; infer_instance
instance instHasDistribNeg : HasDistribNeg UnitDisc := by unfold UnitDisc; infer_instance
instance instCoe : Coe UnitDisc ℂ := ⟨Subtype.val⟩
theorem coe_injective : Injective ((↑) : 𝔻 → ℂ) :=
Subtype.coe_injective
#align complex.unit_disc.coe_injective Complex.UnitDisc.coe_injective
theorem abs_lt_one (z : 𝔻) : abs (z : ℂ) < 1 :=
mem_ball_zero_iff.1 z.2
#align complex.unit_disc.abs_lt_one Complex.UnitDisc.abs_lt_one
theorem abs_ne_one (z : 𝔻) : abs (z : ℂ) ≠ 1 :=
z.abs_lt_one.ne
#align complex.unit_disc.abs_ne_one Complex.UnitDisc.abs_ne_one
| Mathlib/Analysis/Complex/UnitDisc/Basic.lean | 53 | 55 | theorem normSq_lt_one (z : 𝔻) : normSq z < 1 := by |
convert (Real.sqrt_lt' one_pos).1 z.abs_lt_one
exact (one_pow 2).symm
|
/-
Copyright (c) 2023 Felix Weilacher. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Felix Weilacher, Yury G. Kudryashov, Rémy Degenne
-/
import Mathlib.MeasureTheory.MeasurableSpace.Basic
import Mathlib.Data.Set.MemPartition
import Mathlib.Order.Filter.CountableSeparatingOn
/-!
# Countably generated measurable spaces
We say a measurable space is countably generated if it can be generated by a countable set of sets.
In such a space, we can also build a sequence of finer and finer finite measurable partitions of
the space such that the measurable space is generated by the union of all partitions.
## Main definitions
* `MeasurableSpace.CountablyGenerated`: class stating that a measurable space is countably
generated.
* `MeasurableSpace.countableGeneratingSet`: a countable set of sets that generates the σ-algebra.
* `MeasurableSpace.countablePartition`: sequences of finer and finer partitions of
a countably generated space, defined by taking the `memPartion` of an enumeration of the sets in
`countableGeneratingSet`.
* `MeasurableSpace.SeparatesPoints` : class stating that a measurable space separates points.
## Main statements
* `MeasurableSpace.measurable_equiv_nat_bool_of_countablyGenerated`: if a measurable space is
countably generated and separates points, it is measure equivalent to a subset of the Cantor Space
`ℕ → Bool` (equipped with the product sigma algebra).
* `MeasurableSpace.measurable_injection_nat_bool_of_countablyGenerated`: If a measurable space
admits a countable sequence of measurable sets separating points,
it admits a measurable injection into the Cantor space `ℕ → Bool`
`ℕ → Bool` (equipped with the product sigma algebra).
The file also contains measurability results about `memPartition`, from which the properties of
`countablePartition` are deduced.
-/
open Set MeasureTheory
namespace MeasurableSpace
variable {α β : Type*}
/-- We say a measurable space is countably generated
if it can be generated by a countable set of sets. -/
class CountablyGenerated (α : Type*) [m : MeasurableSpace α] : Prop where
isCountablyGenerated : ∃ b : Set (Set α), b.Countable ∧ m = generateFrom b
#align measurable_space.countably_generated MeasurableSpace.CountablyGenerated
/-- A countable set of sets that generate the measurable space.
We insert `∅` to ensure it is nonempty. -/
def countableGeneratingSet (α : Type*) [MeasurableSpace α] [h : CountablyGenerated α] :
Set (Set α) :=
insert ∅ h.isCountablyGenerated.choose
lemma countable_countableGeneratingSet [MeasurableSpace α] [h : CountablyGenerated α] :
Set.Countable (countableGeneratingSet α) :=
Countable.insert _ h.isCountablyGenerated.choose_spec.1
lemma generateFrom_countableGeneratingSet [m : MeasurableSpace α] [h : CountablyGenerated α] :
generateFrom (countableGeneratingSet α) = m :=
(generateFrom_insert_empty _).trans <| h.isCountablyGenerated.choose_spec.2.symm
lemma empty_mem_countableGeneratingSet [MeasurableSpace α] [CountablyGenerated α] :
∅ ∈ countableGeneratingSet α := mem_insert _ _
lemma nonempty_countableGeneratingSet [MeasurableSpace α] [CountablyGenerated α] :
Set.Nonempty (countableGeneratingSet α) :=
⟨∅, mem_insert _ _⟩
lemma measurableSet_countableGeneratingSet [MeasurableSpace α] [CountablyGenerated α]
{s : Set α} (hs : s ∈ countableGeneratingSet α) :
MeasurableSet s := by
rw [← generateFrom_countableGeneratingSet (α := α)]
exact measurableSet_generateFrom hs
/-- A countable sequence of sets generating the measurable space. -/
def natGeneratingSequence (α : Type*) [MeasurableSpace α] [CountablyGenerated α] : ℕ → (Set α) :=
enumerateCountable (countable_countableGeneratingSet (α := α)) ∅
lemma generateFrom_natGeneratingSequence (α : Type*) [m : MeasurableSpace α]
[CountablyGenerated α] : generateFrom (range (natGeneratingSequence _)) = m := by
rw [natGeneratingSequence, range_enumerateCountable_of_mem _ empty_mem_countableGeneratingSet,
generateFrom_countableGeneratingSet]
lemma measurableSet_natGeneratingSequence [MeasurableSpace α] [CountablyGenerated α] (n : ℕ) :
MeasurableSet (natGeneratingSequence α n) :=
measurableSet_countableGeneratingSet $ Set.enumerateCountable_mem _
empty_mem_countableGeneratingSet n
| Mathlib/MeasureTheory/MeasurableSpace/CountablyGenerated.lean | 96 | 101 | theorem CountablyGenerated.comap [m : MeasurableSpace β] [h : CountablyGenerated β] (f : α → β) :
@CountablyGenerated α (.comap f m) := by |
rcases h with ⟨⟨b, hbc, rfl⟩⟩
rw [comap_generateFrom]
letI := generateFrom (preimage f '' b)
exact ⟨_, hbc.image _, rfl⟩
|
/-
Copyright (c) 2021 Eric Weiser. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Eric Wieser
-/
import Mathlib.Algebra.Algebra.Operations
import Mathlib.Algebra.Algebra.Subalgebra.Basic
import Mathlib.Algebra.Ring.Subring.Pointwise
import Mathlib.RingTheory.Adjoin.Basic
#align_import algebra.algebra.subalgebra.pointwise from "leanprover-community/mathlib"@"b2c707cd190a58ea0565c86695a19e99ccecc215"
/-!
# Pointwise actions on subalgebras.
If `R'` acts on an `R`-algebra `A` (so that `R'` and `R` actions commute)
then we get an `R'` action on the collection of `R`-subalgebras.
-/
namespace Subalgebra
section Pointwise
variable {R : Type*} {A : Type*} [CommSemiring R] [Semiring A] [Algebra R A]
| Mathlib/Algebra/Algebra/Subalgebra/Pointwise.lean | 27 | 32 | theorem mul_toSubmodule_le (S T : Subalgebra R A) :
(Subalgebra.toSubmodule S)* (Subalgebra.toSubmodule T) ≤ Subalgebra.toSubmodule (S ⊔ T) := by |
rw [Submodule.mul_le]
intro y hy z hz
show y * z ∈ S ⊔ T
exact mul_mem (Algebra.mem_sup_left hy) (Algebra.mem_sup_right hz)
|
/-
Copyright (c) 2022 Zhouhang Zhou. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Zhouhang Zhou, Yury Kudryashov, Heather Macbeth
-/
import Mathlib.MeasureTheory.Function.L1Space
import Mathlib.MeasureTheory.Function.SimpleFuncDense
#align_import measure_theory.function.simple_func_dense_lp from "leanprover-community/mathlib"@"5a2df4cd59cb31e97a516d4603a14bed5c2f9425"
/-!
# Density of simple functions
Show that each `Lᵖ` Borel measurable function can be approximated in `Lᵖ` norm
by a sequence of simple functions.
## Main definitions
* `MeasureTheory.Lp.simpleFunc`, the type of `Lp` simple functions
* `coeToLp`, the embedding of `Lp.simpleFunc E p μ` into `Lp E p μ`
## Main results
* `tendsto_approxOn_Lp_snorm` (Lᵖ convergence): If `E` is a `NormedAddCommGroup` and `f` is
measurable and `Memℒp` (for `p < ∞`), then the simple functions
`SimpleFunc.approxOn f hf s 0 h₀ n` may be considered as elements of `Lp E p μ`, and they tend
in Lᵖ to `f`.
* `Lp.simpleFunc.denseEmbedding`: the embedding `coeToLp` of the `Lp` simple functions into
`Lp` is dense.
* `Lp.simpleFunc.induction`, `Lp.induction`, `Memℒp.induction`, `Integrable.induction`: to prove
a predicate for all elements of one of these classes of functions, it suffices to check that it
behaves correctly on simple functions.
## TODO
For `E` finite-dimensional, simple functions `α →ₛ E` are dense in L^∞ -- prove this.
## Notations
* `α →ₛ β` (local notation): the type of simple functions `α → β`.
* `α →₁ₛ[μ] E`: the type of `L1` simple functions `α → β`.
-/
noncomputable section
set_option linter.uppercaseLean3 false
open Set Function Filter TopologicalSpace ENNReal EMetric Finset
open scoped Classical Topology ENNReal MeasureTheory
variable {α β ι E F 𝕜 : Type*}
namespace MeasureTheory
local infixr:25 " →ₛ " => SimpleFunc
namespace SimpleFunc
/-! ### Lp approximation by simple functions -/
section Lp
variable [MeasurableSpace β] [MeasurableSpace E] [NormedAddCommGroup E] [NormedAddCommGroup F]
{q : ℝ} {p : ℝ≥0∞}
theorem nnnorm_approxOn_le [OpensMeasurableSpace E] {f : β → E} (hf : Measurable f) {s : Set E}
{y₀ : E} (h₀ : y₀ ∈ s) [SeparableSpace s] (x : β) (n : ℕ) :
‖approxOn f hf s y₀ h₀ n x - f x‖₊ ≤ ‖f x - y₀‖₊ := by
have := edist_approxOn_le hf h₀ x n
rw [edist_comm y₀] at this
simp only [edist_nndist, nndist_eq_nnnorm] at this
exact mod_cast this
#align measure_theory.simple_func.nnnorm_approx_on_le MeasureTheory.SimpleFunc.nnnorm_approxOn_le
theorem norm_approxOn_y₀_le [OpensMeasurableSpace E] {f : β → E} (hf : Measurable f) {s : Set E}
{y₀ : E} (h₀ : y₀ ∈ s) [SeparableSpace s] (x : β) (n : ℕ) :
‖approxOn f hf s y₀ h₀ n x - y₀‖ ≤ ‖f x - y₀‖ + ‖f x - y₀‖ := by
have := edist_approxOn_y0_le hf h₀ x n
repeat rw [edist_comm y₀, edist_eq_coe_nnnorm_sub] at this
exact mod_cast this
#align measure_theory.simple_func.norm_approx_on_y₀_le MeasureTheory.SimpleFunc.norm_approxOn_y₀_le
| Mathlib/MeasureTheory/Function/SimpleFuncDenseLp.lean | 85 | 90 | theorem norm_approxOn_zero_le [OpensMeasurableSpace E] {f : β → E} (hf : Measurable f) {s : Set E}
(h₀ : (0 : E) ∈ s) [SeparableSpace s] (x : β) (n : ℕ) :
‖approxOn f hf s 0 h₀ n x‖ ≤ ‖f x‖ + ‖f x‖ := by |
have := edist_approxOn_y0_le hf h₀ x n
simp [edist_comm (0 : E), edist_eq_coe_nnnorm] at this
exact mod_cast this
|
/-
Copyright (c) 2018 Guy Leroy. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Sangwoo Jo (aka Jason), Guy Leroy, Johannes Hölzl, Mario Carneiro
-/
import Mathlib.Algebra.Group.Commute.Units
import Mathlib.Algebra.Group.Int
import Mathlib.Algebra.GroupWithZero.Semiconj
import Mathlib.Data.Nat.GCD.Basic
import Mathlib.Order.Bounds.Basic
#align_import data.int.gcd from "leanprover-community/mathlib"@"47a1a73351de8dd6c8d3d32b569c8e434b03ca47"
/-!
# Extended GCD and divisibility over ℤ
## Main definitions
* Given `x y : ℕ`, `xgcd x y` computes the pair of integers `(a, b)` such that
`gcd x y = x * a + y * b`. `gcdA x y` and `gcdB x y` are defined to be `a` and `b`,
respectively.
## Main statements
* `gcd_eq_gcd_ab`: Bézout's lemma, given `x y : ℕ`, `gcd x y = x * gcdA x y + y * gcdB x y`.
## Tags
Bézout's lemma, Bezout's lemma
-/
/-! ### Extended Euclidean algorithm -/
namespace Nat
/-- Helper function for the extended GCD algorithm (`Nat.xgcd`). -/
def xgcdAux : ℕ → ℤ → ℤ → ℕ → ℤ → ℤ → ℕ × ℤ × ℤ
| 0, _, _, r', s', t' => (r', s', t')
| succ k, s, t, r', s', t' =>
let q := r' / succ k
xgcdAux (r' % succ k) (s' - q * s) (t' - q * t) (succ k) s t
termination_by k => k
decreasing_by exact mod_lt _ <| (succ_pos _).gt
#align nat.xgcd_aux Nat.xgcdAux
@[simp]
theorem xgcd_zero_left {s t r' s' t'} : xgcdAux 0 s t r' s' t' = (r', s', t') := by simp [xgcdAux]
#align nat.xgcd_zero_left Nat.xgcd_zero_left
theorem xgcdAux_rec {r s t r' s' t'} (h : 0 < r) :
xgcdAux r s t r' s' t' = xgcdAux (r' % r) (s' - r' / r * s) (t' - r' / r * t) r s t := by
obtain ⟨r, rfl⟩ := Nat.exists_eq_succ_of_ne_zero h.ne'
simp [xgcdAux]
#align nat.xgcd_aux_rec Nat.xgcdAux_rec
/-- Use the extended GCD algorithm to generate the `a` and `b` values
satisfying `gcd x y = x * a + y * b`. -/
def xgcd (x y : ℕ) : ℤ × ℤ :=
(xgcdAux x 1 0 y 0 1).2
#align nat.xgcd Nat.xgcd
/-- The extended GCD `a` value in the equation `gcd x y = x * a + y * b`. -/
def gcdA (x y : ℕ) : ℤ :=
(xgcd x y).1
#align nat.gcd_a Nat.gcdA
/-- The extended GCD `b` value in the equation `gcd x y = x * a + y * b`. -/
def gcdB (x y : ℕ) : ℤ :=
(xgcd x y).2
#align nat.gcd_b Nat.gcdB
@[simp]
theorem gcdA_zero_left {s : ℕ} : gcdA 0 s = 0 := by
unfold gcdA
rw [xgcd, xgcd_zero_left]
#align nat.gcd_a_zero_left Nat.gcdA_zero_left
@[simp]
theorem gcdB_zero_left {s : ℕ} : gcdB 0 s = 1 := by
unfold gcdB
rw [xgcd, xgcd_zero_left]
#align nat.gcd_b_zero_left Nat.gcdB_zero_left
@[simp]
theorem gcdA_zero_right {s : ℕ} (h : s ≠ 0) : gcdA s 0 = 1 := by
unfold gcdA xgcd
obtain ⟨s, rfl⟩ := Nat.exists_eq_succ_of_ne_zero h
rw [xgcdAux]
simp
#align nat.gcd_a_zero_right Nat.gcdA_zero_right
@[simp]
| Mathlib/Data/Int/GCD.lean | 94 | 98 | theorem gcdB_zero_right {s : ℕ} (h : s ≠ 0) : gcdB s 0 = 0 := by |
unfold gcdB xgcd
obtain ⟨s, rfl⟩ := Nat.exists_eq_succ_of_ne_zero h
rw [xgcdAux]
simp
|
/-
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
| Mathlib/MeasureTheory/Measure/MeasureSpace.lean | 128 | 132 | 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
|
/-
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.Algebra.MvPolynomial.Rename
#align_import data.mv_polynomial.comap from "leanprover-community/mathlib"@"aba31c938d3243cc671be7091b28a1e0814647ee"
/-!
# `comap` operation on `MvPolynomial`
This file defines the `comap` function on `MvPolynomial`.
`MvPolynomial.comap` is a low-tech example of a map of "algebraic varieties," modulo the fact that
`mathlib` does not yet define varieties.
## Notation
As in other polynomial files, we typically use the notation:
+ `σ : Type*` (indexing the variables)
+ `R : Type*` `[CommSemiring R]` (the coefficients)
-/
namespace MvPolynomial
variable {σ : Type*} {τ : Type*} {υ : Type*} {R : Type*} [CommSemiring R]
/-- Given an algebra hom `f : MvPolynomial σ R →ₐ[R] MvPolynomial τ R`
and a variable evaluation `v : τ → R`,
`comap f v` produces a variable evaluation `σ → R`.
-/
noncomputable def comap (f : MvPolynomial σ R →ₐ[R] MvPolynomial τ R) : (τ → R) → σ → R :=
fun x i => aeval x (f (X i))
#align mv_polynomial.comap MvPolynomial.comap
@[simp]
theorem comap_apply (f : MvPolynomial σ R →ₐ[R] MvPolynomial τ R) (x : τ → R) (i : σ) :
comap f x i = aeval x (f (X i)) :=
rfl
#align mv_polynomial.comap_apply MvPolynomial.comap_apply
@[simp]
theorem comap_id_apply (x : σ → R) : comap (AlgHom.id R (MvPolynomial σ R)) x = x := by
funext i
simp only [comap, AlgHom.id_apply, id, aeval_X]
#align mv_polynomial.comap_id_apply MvPolynomial.comap_id_apply
variable (σ R)
theorem comap_id : comap (AlgHom.id R (MvPolynomial σ R)) = id := by
funext x
exact comap_id_apply x
#align mv_polynomial.comap_id MvPolynomial.comap_id
variable {σ R}
| Mathlib/Algebra/MvPolynomial/Comap.lean | 62 | 74 | theorem comap_comp_apply (f : MvPolynomial σ R →ₐ[R] MvPolynomial τ R)
(g : MvPolynomial τ R →ₐ[R] MvPolynomial υ R) (x : υ → R) :
comap (g.comp f) x = comap f (comap g x) := by |
funext i
trans aeval x (aeval (fun i => g (X i)) (f (X i)))
· apply eval₂Hom_congr rfl rfl
rw [AlgHom.comp_apply]
suffices g = aeval fun i => g (X i) by rw [← this]
exact aeval_unique g
· simp only [comap, aeval_eq_eval₂Hom, map_eval₂Hom, AlgHom.comp_apply]
refine eval₂Hom_congr ?_ rfl rfl
ext r
apply aeval_C
|
/-
Copyright (c) 2021 Anne Baanen. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Anne Baanen
-/
import Mathlib.GroupTheory.QuotientGroup
import Mathlib.RingTheory.DedekindDomain.Ideal
#align_import ring_theory.class_group from "leanprover-community/mathlib"@"565eb991e264d0db702722b4bde52ee5173c9950"
/-!
# The ideal class group
This file defines the ideal class group `ClassGroup R` of fractional ideals of `R`
inside its field of fractions.
## Main definitions
- `toPrincipalIdeal` sends an invertible `x : K` to an invertible fractional ideal
- `ClassGroup` is the quotient of invertible fractional ideals modulo `toPrincipalIdeal.range`
- `ClassGroup.mk0` sends a nonzero integral ideal in a Dedekind domain to its class
## Main results
- `ClassGroup.mk0_eq_mk0_iff` shows the equivalence with the "classical" definition,
where `I ~ J` iff `x I = y J` for `x y ≠ (0 : R)`
## Implementation details
The definition of `ClassGroup R` involves `FractionRing R`. However, the API should be completely
identical no matter the choice of field of fractions for `R`.
-/
variable {R K L : Type*} [CommRing R]
variable [Field K] [Field L] [DecidableEq L]
variable [Algebra R K] [IsFractionRing R K]
variable [Algebra K L] [FiniteDimensional K L]
variable [Algebra R L] [IsScalarTower R K L]
open scoped nonZeroDivisors
open IsLocalization IsFractionRing FractionalIdeal Units
section
variable (R K)
/-- `toPrincipalIdeal R K x` sends `x ≠ 0 : K` to the fractional `R`-ideal generated by `x` -/
irreducible_def toPrincipalIdeal : Kˣ →* (FractionalIdeal R⁰ K)ˣ :=
{ toFun := fun x =>
⟨spanSingleton _ x, spanSingleton _ x⁻¹, by
simp only [spanSingleton_one, Units.mul_inv', spanSingleton_mul_spanSingleton], by
simp only [spanSingleton_one, Units.inv_mul', spanSingleton_mul_spanSingleton]⟩
map_mul' := fun x y =>
ext (by simp only [Units.val_mk, Units.val_mul, spanSingleton_mul_spanSingleton])
map_one' := ext (by simp only [spanSingleton_one, Units.val_mk, Units.val_one]) }
#align to_principal_ideal toPrincipalIdeal
variable {R K}
@[simp]
theorem coe_toPrincipalIdeal (x : Kˣ) :
(toPrincipalIdeal R K x : FractionalIdeal R⁰ K) = spanSingleton _ (x : K) := by
simp only [toPrincipalIdeal]; rfl
#align coe_to_principal_ideal coe_toPrincipalIdeal
@[simp]
theorem toPrincipalIdeal_eq_iff {I : (FractionalIdeal R⁰ K)ˣ} {x : Kˣ} :
toPrincipalIdeal R K x = I ↔ spanSingleton R⁰ (x : K) = I := by
simp only [toPrincipalIdeal]; exact Units.ext_iff
#align to_principal_ideal_eq_iff toPrincipalIdeal_eq_iff
theorem mem_principal_ideals_iff {I : (FractionalIdeal R⁰ K)ˣ} :
I ∈ (toPrincipalIdeal R K).range ↔ ∃ x : K, spanSingleton R⁰ x = I := by
simp only [MonoidHom.mem_range, toPrincipalIdeal_eq_iff]
constructor <;> rintro ⟨x, hx⟩
· exact ⟨x, hx⟩
· refine ⟨Units.mk0 x ?_, hx⟩
rintro rfl
simp [I.ne_zero.symm] at hx
#align mem_principal_ideals_iff mem_principal_ideals_iff
instance PrincipalIdeals.normal : (toPrincipalIdeal R K).range.Normal :=
Subgroup.normal_of_comm _
#align principal_ideals.normal PrincipalIdeals.normal
end
variable (R)
variable [IsDomain R]
/-- The ideal class group of `R` is the group of invertible fractional ideals
modulo the principal ideals. -/
def ClassGroup :=
(FractionalIdeal R⁰ (FractionRing R))ˣ ⧸ (toPrincipalIdeal R (FractionRing R)).range
#align class_group ClassGroup
noncomputable instance : CommGroup (ClassGroup R) :=
QuotientGroup.Quotient.commGroup (toPrincipalIdeal R (FractionRing R)).range
noncomputable instance : Inhabited (ClassGroup R) := ⟨1⟩
variable {R}
/-- Send a nonzero fractional ideal to the corresponding class in the class group. -/
noncomputable def ClassGroup.mk : (FractionalIdeal R⁰ K)ˣ →* ClassGroup R :=
(QuotientGroup.mk' (toPrincipalIdeal R (FractionRing R)).range).comp
(Units.map (FractionalIdeal.canonicalEquiv R⁰ K (FractionRing R)))
#align class_group.mk ClassGroup.mk
-- Can't be `@[simp]` because it can't figure out the quotient relation.
| Mathlib/RingTheory/ClassGroup.lean | 111 | 117 | theorem ClassGroup.Quot_mk_eq_mk (I : (FractionalIdeal R⁰ (FractionRing R))ˣ) :
Quot.mk _ I = ClassGroup.mk I := by |
rw [ClassGroup.mk, canonicalEquiv_self, RingEquiv.coe_monoidHom_refl, Units.map_id]
-- This used to be `rw`, but we need `erw` after leanprover/lean4#2644
erw [MonoidHom.comp_apply]
rw [MonoidHom.id_apply, QuotientGroup.mk'_apply]
rfl
|
/-
Copyright (c) 2019 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl
-/
import Mathlib.Algebra.CharP.Defs
import Mathlib.Algebra.MvPolynomial.Degrees
import Mathlib.Algebra.Polynomial.AlgebraMap
import Mathlib.LinearAlgebra.FinsuppVectorSpace
import Mathlib.LinearAlgebra.FreeModule.Finite.Basic
#align_import ring_theory.mv_polynomial.basic from "leanprover-community/mathlib"@"2f5b500a507264de86d666a5f87ddb976e2d8de4"
/-!
# Multivariate polynomials over commutative rings
This file contains basic facts about multivariate polynomials over commutative rings, for example
that the monomials form a basis.
## Main definitions
* `restrictTotalDegree σ R m`: the subspace of multivariate polynomials indexed by `σ` over the
commutative ring `R` of total degree at most `m`.
* `restrictDegree σ R m`: the subspace of multivariate polynomials indexed by `σ` over the
commutative ring `R` such that the degree in each individual variable is at most `m`.
## Main statements
* The multivariate polynomial ring over a commutative semiring of characteristic `p` has
characteristic `p`, and similarly for `CharZero`.
* `basisMonomials`: shows that the monomials form a basis of the vector space of multivariate
polynomials.
## TODO
Generalise to noncommutative (semi)rings
-/
noncomputable section
open Set LinearMap Submodule
open Polynomial
universe u v
variable (σ : Type u) (R : Type v) [CommSemiring R] (p m : ℕ)
namespace MvPolynomial
section CharP
instance [CharP R p] : CharP (MvPolynomial σ R) p where
cast_eq_zero_iff' n := by rw [← C_eq_coe_nat, ← C_0, C_inj, CharP.cast_eq_zero_iff R p]
end CharP
section CharZero
instance [CharZero R] : CharZero (MvPolynomial σ R) where
cast_injective x y hxy := by rwa [← C_eq_coe_nat, ← C_eq_coe_nat, C_inj, Nat.cast_inj] at hxy
end CharZero
section Homomorphism
| Mathlib/RingTheory/MvPolynomial/Basic.lean | 68 | 72 | theorem mapRange_eq_map {R S : Type*} [CommSemiring R] [CommSemiring S] (p : MvPolynomial σ R)
(f : R →+* S) : Finsupp.mapRange f f.map_zero p = map f p := by |
rw [p.as_sum, Finsupp.mapRange_finset_sum, map_sum (map f)]
refine Finset.sum_congr rfl fun n _ => ?_
rw [map_monomial, ← single_eq_monomial, Finsupp.mapRange_single, single_eq_monomial]
|
/-
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.Measure.GiryMonad
import Mathlib.Dynamics.Ergodic.MeasurePreserving
import Mathlib.MeasureTheory.Integral.Lebesgue
import Mathlib.MeasureTheory.Measure.OpenPos
#align_import measure_theory.constructions.prod.basic from "leanprover-community/mathlib"@"00abe0695d8767201e6d008afa22393978bb324d"
/-!
# The product measure
In this file we define and prove properties about the binary product measure. If `α` and `β` have
s-finite measures `μ` resp. `ν` then `α × β` can be equipped with a s-finite measure `μ.prod ν` that
satisfies `(μ.prod ν) s = ∫⁻ x, ν {y | (x, y) ∈ s} ∂μ`.
We also have `(μ.prod ν) (s ×ˢ t) = μ s * ν t`, i.e. the measure of a rectangle is the product of
the measures of the sides.
We also prove Tonelli's theorem.
## Main definition
* `MeasureTheory.Measure.prod`: The product of two measures.
## Main results
* `MeasureTheory.Measure.prod_apply` states `μ.prod ν s = ∫⁻ x, ν {y | (x, y) ∈ s} ∂μ`
for measurable `s`. `MeasureTheory.Measure.prod_apply_symm` is the reversed version.
* `MeasureTheory.Measure.prod_prod` states `μ.prod ν (s ×ˢ t) = μ s * ν t` for measurable sets
`s` and `t`.
* `MeasureTheory.lintegral_prod`: Tonelli's theorem. It states that for a measurable function
`α × β → ℝ≥0∞` we have `∫⁻ z, f z ∂(μ.prod ν) = ∫⁻ x, ∫⁻ y, f (x, y) ∂ν ∂μ`. The version
for functions `α → β → ℝ≥0∞` is reversed, and called `lintegral_lintegral`. Both versions have
a variant with `_symm` appended, where the order of integration is reversed.
The lemma `Measurable.lintegral_prod_right'` states that the inner integral of the right-hand side
is measurable.
## Implementation Notes
Many results are proven twice, once for functions in curried form (`α → β → γ`) and one for
functions in uncurried form (`α × β → γ`). The former often has an assumption
`Measurable (uncurry f)`, which could be inconvenient to discharge, but for the latter it is more
common that the function has to be given explicitly, since Lean cannot synthesize the function by
itself. We name the lemmas about the uncurried form with a prime.
Tonelli's theorem has a different naming scheme, since the version for the uncurried version is
reversed.
## Tags
product measure, Tonelli's theorem, Fubini-Tonelli theorem
-/
noncomputable section
open scoped Classical
open Topology ENNReal MeasureTheory
open Set Function Real ENNReal
open MeasureTheory MeasurableSpace MeasureTheory.Measure
open TopologicalSpace hiding generateFrom
open Filter hiding prod_eq map
variable {α α' β β' γ E : Type*}
/-- Rectangles formed by π-systems form a π-system. -/
theorem IsPiSystem.prod {C : Set (Set α)} {D : Set (Set β)} (hC : IsPiSystem C)
(hD : IsPiSystem D) : IsPiSystem (image2 (· ×ˢ ·) C D) := by
rintro _ ⟨s₁, hs₁, t₁, ht₁, rfl⟩ _ ⟨s₂, hs₂, t₂, ht₂, rfl⟩ hst
rw [prod_inter_prod] at hst ⊢; rw [prod_nonempty_iff] at hst
exact mem_image2_of_mem (hC _ hs₁ _ hs₂ hst.1) (hD _ ht₁ _ ht₂ hst.2)
#align is_pi_system.prod IsPiSystem.prod
/-- Rectangles of countably spanning sets are countably spanning. -/
| Mathlib/MeasureTheory/Constructions/Prod/Basic.lean | 81 | 85 | theorem IsCountablySpanning.prod {C : Set (Set α)} {D : Set (Set β)} (hC : IsCountablySpanning C)
(hD : IsCountablySpanning D) : IsCountablySpanning (image2 (· ×ˢ ·) C D) := by |
rcases hC, hD with ⟨⟨s, h1s, h2s⟩, t, h1t, h2t⟩
refine ⟨fun n => s n.unpair.1 ×ˢ t n.unpair.2, fun n => mem_image2_of_mem (h1s _) (h1t _), ?_⟩
rw [iUnion_unpair_prod, h2s, h2t, univ_prod_univ]
|
/-
Copyright (c) 2020 Kevin Buzzard. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Kevin Buzzard
-/
import Mathlib.RingTheory.PrincipalIdealDomain
import Mathlib.RingTheory.Ideal.LocalRing
import Mathlib.RingTheory.Valuation.PrimeMultiplicity
import Mathlib.RingTheory.AdicCompletion.Basic
#align_import ring_theory.discrete_valuation_ring.basic from "leanprover-community/mathlib"@"c163ec99dfc664628ca15d215fce0a5b9c265b68"
/-!
# Discrete valuation rings
This file defines discrete valuation rings (DVRs) and develops a basic interface
for them.
## Important definitions
There are various definitions of a DVR in the literature; we define a DVR to be a local PID
which is not a field (the first definition in Wikipedia) and prove that this is equivalent
to being a PID with a unique non-zero prime ideal (the definition in Serre's
book "Local Fields").
Let R be an integral domain, assumed to be a principal ideal ring and a local ring.
* `DiscreteValuationRing R` : a predicate expressing that R is a DVR.
### Definitions
* `addVal R : AddValuation R PartENat` : the additive valuation on a DVR.
## Implementation notes
It's a theorem that an element of a DVR is a uniformizer if and only if it's irreducible.
We do not hence define `Uniformizer` at all, because we can use `Irreducible` instead.
## Tags
discrete valuation ring
-/
open scoped Classical
universe u
open Ideal LocalRing
/-- An integral domain is a *discrete valuation ring* (DVR) if it's a local PID which
is not a field. -/
class DiscreteValuationRing (R : Type u) [CommRing R] [IsDomain R]
extends IsPrincipalIdealRing R, LocalRing R : Prop where
not_a_field' : maximalIdeal R ≠ ⊥
#align discrete_valuation_ring DiscreteValuationRing
namespace DiscreteValuationRing
variable (R : Type u) [CommRing R] [IsDomain R] [DiscreteValuationRing R]
theorem not_a_field : maximalIdeal R ≠ ⊥ :=
not_a_field'
#align discrete_valuation_ring.not_a_field DiscreteValuationRing.not_a_field
/-- A discrete valuation ring `R` is not a field. -/
theorem not_isField : ¬IsField R :=
LocalRing.isField_iff_maximalIdeal_eq.not.mpr (not_a_field R)
#align discrete_valuation_ring.not_is_field DiscreteValuationRing.not_isField
variable {R}
open PrincipalIdealRing
| Mathlib/RingTheory/DiscreteValuationRing/Basic.lean | 75 | 88 | theorem irreducible_of_span_eq_maximalIdeal {R : Type*} [CommRing R] [LocalRing R] [IsDomain R]
(ϖ : R) (hϖ : ϖ ≠ 0) (h : maximalIdeal R = Ideal.span {ϖ}) : Irreducible ϖ := by |
have h2 : ¬IsUnit ϖ := show ϖ ∈ maximalIdeal R from h.symm ▸ Submodule.mem_span_singleton_self ϖ
refine ⟨h2, ?_⟩
intro a b hab
by_contra! h
obtain ⟨ha : a ∈ maximalIdeal R, hb : b ∈ maximalIdeal R⟩ := h
rw [h, mem_span_singleton'] at ha hb
rcases ha with ⟨a, rfl⟩
rcases hb with ⟨b, rfl⟩
rw [show a * ϖ * (b * ϖ) = ϖ * (ϖ * (a * b)) by ring] at hab
apply hϖ
apply eq_zero_of_mul_eq_self_right _ hab.symm
exact fun hh => h2 (isUnit_of_dvd_one ⟨_, hh.symm⟩)
|
/-
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.RingTheory.WittVector.Frobenius
import Mathlib.RingTheory.WittVector.Verschiebung
import Mathlib.RingTheory.WittVector.MulP
#align_import ring_theory.witt_vector.identities from "leanprover-community/mathlib"@"0798037604b2d91748f9b43925fb7570a5f3256c"
/-!
## Identities between operations on the ring of Witt vectors
In this file we derive common identities between the Frobenius and Verschiebung operators.
## Main declarations
* `frobenius_verschiebung`: the composition of Frobenius and Verschiebung is multiplication by `p`
* `verschiebung_mul_frobenius`: the “projection formula”: `V(x * F y) = V x * y`
* `iterate_verschiebung_mul_coeff`: an identity from [Haze09] 6.2
## References
* [Hazewinkel, *Witt Vectors*][Haze09]
* [Commelin and Lewis, *Formalizing the Ring of Witt Vectors*][CL21]
-/
namespace WittVector
variable {p : ℕ} {R : Type*} [hp : Fact p.Prime] [CommRing R]
-- type as `\bbW`
local notation "𝕎" => WittVector p
noncomputable section
-- Porting note: `ghost_calc` failure: `simp only []` and the manual instances had to be added.
/-- The composition of Frobenius and Verschiebung is multiplication by `p`. -/
theorem frobenius_verschiebung (x : 𝕎 R) : frobenius (verschiebung x) = x * p := by
have : IsPoly p fun {R} [CommRing R] x ↦ frobenius (verschiebung x) :=
IsPoly.comp (hg := frobenius_isPoly p) (hf := verschiebung_isPoly)
have : IsPoly p fun {R} [CommRing R] x ↦ x * p := mulN_isPoly p p
ghost_calc x
ghost_simp [mul_comm]
#align witt_vector.frobenius_verschiebung WittVector.frobenius_verschiebung
/-- Verschiebung is the same as multiplication by `p` on the ring of Witt vectors of `ZMod p`. -/
theorem verschiebung_zmod (x : 𝕎 (ZMod p)) : verschiebung x = x * p := by
rw [← frobenius_verschiebung, frobenius_zmodp]
#align witt_vector.verschiebung_zmod WittVector.verschiebung_zmod
variable (p R)
theorem coeff_p_pow [CharP R p] (i : ℕ) : ((p : 𝕎 R) ^ i).coeff i = 1 := by
induction' i with i h
· simp only [Nat.zero_eq, one_coeff_zero, Ne, pow_zero]
· rw [pow_succ, ← frobenius_verschiebung, coeff_frobenius_charP,
verschiebung_coeff_succ, h, one_pow]
#align witt_vector.coeff_p_pow WittVector.coeff_p_pow
theorem coeff_p_pow_eq_zero [CharP R p] {i j : ℕ} (hj : j ≠ i) : ((p : 𝕎 R) ^ i).coeff j = 0 := by
induction' i with i hi generalizing j
· rw [pow_zero, one_coeff_eq_of_pos]
exact Nat.pos_of_ne_zero hj
· rw [pow_succ, ← frobenius_verschiebung, coeff_frobenius_charP]
cases j
· rw [verschiebung_coeff_zero, zero_pow hp.out.ne_zero]
· rw [verschiebung_coeff_succ, hi (ne_of_apply_ne _ hj), zero_pow hp.out.ne_zero]
#align witt_vector.coeff_p_pow_eq_zero WittVector.coeff_p_pow_eq_zero
theorem coeff_p [CharP R p] (i : ℕ) : (p : 𝕎 R).coeff i = if i = 1 then 1 else 0 := by
split_ifs with hi
· simpa only [hi, pow_one] using coeff_p_pow p R 1
· simpa only [pow_one] using coeff_p_pow_eq_zero p R hi
#align witt_vector.coeff_p WittVector.coeff_p
@[simp]
theorem coeff_p_zero [CharP R p] : (p : 𝕎 R).coeff 0 = 0 := by
rw [coeff_p, if_neg]
exact zero_ne_one
#align witt_vector.coeff_p_zero WittVector.coeff_p_zero
@[simp]
theorem coeff_p_one [CharP R p] : (p : 𝕎 R).coeff 1 = 1 := by rw [coeff_p, if_pos rfl]
#align witt_vector.coeff_p_one WittVector.coeff_p_one
theorem p_nonzero [Nontrivial R] [CharP R p] : (p : 𝕎 R) ≠ 0 := by
intro h
simpa only [h, zero_coeff, zero_ne_one] using coeff_p_one p R
#align witt_vector.p_nonzero WittVector.p_nonzero
theorem FractionRing.p_nonzero [Nontrivial R] [CharP R p] : (p : FractionRing (𝕎 R)) ≠ 0 := by
simpa using (IsFractionRing.injective (𝕎 R) (FractionRing (𝕎 R))).ne (WittVector.p_nonzero _ _)
#align witt_vector.fraction_ring.p_nonzero WittVector.FractionRing.p_nonzero
variable {p R}
-- Porting note: `ghost_calc` failure: `simp only []` and the manual instances had to be added.
/-- The “projection formula” for Frobenius and Verschiebung. -/
theorem verschiebung_mul_frobenius (x y : 𝕎 R) :
verschiebung (x * frobenius y) = verschiebung x * y := by
have : IsPoly₂ p fun {R} [Rcr : CommRing R] x y ↦ verschiebung (x * frobenius y) :=
IsPoly.comp₂ (hg := verschiebung_isPoly)
(hf := IsPoly₂.comp (hh := mulIsPoly₂) (hf := idIsPolyI' p) (hg := frobenius_isPoly p))
have : IsPoly₂ p fun {R} [CommRing R] x y ↦ verschiebung x * y :=
IsPoly₂.comp (hh := mulIsPoly₂) (hf := verschiebung_isPoly) (hg := idIsPolyI' p)
ghost_calc x y
rintro ⟨⟩ <;> ghost_simp [mul_assoc]
#align witt_vector.verschiebung_mul_frobenius WittVector.verschiebung_mul_frobenius
| Mathlib/RingTheory/WittVector/Identities.lean | 114 | 116 | theorem mul_charP_coeff_zero [CharP R p] (x : 𝕎 R) : (x * p).coeff 0 = 0 := by |
rw [← frobenius_verschiebung, coeff_frobenius_charP, verschiebung_coeff_zero,
zero_pow hp.out.ne_zero]
|
/-
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.Polynomial.Degree.Definitions
import Mathlib.Algebra.Polynomial.Induction
#align_import data.polynomial.eval from "leanprover-community/mathlib"@"728baa2f54e6062c5879a3e397ac6bac323e506f"
/-!
# Theory of univariate polynomials
The main defs here are `eval₂`, `eval`, and `map`.
We give several lemmas about their interaction with each other and with module operations.
-/
set_option linter.uppercaseLean3 false
noncomputable section
open Finset AddMonoidAlgebra
open Polynomial
namespace Polynomial
universe u v w y
variable {R : Type u} {S : Type v} {T : Type w} {ι : Type y} {a b : R} {m n : ℕ}
section Semiring
variable [Semiring R] {p q r : R[X]}
section
variable [Semiring S]
variable (f : R →+* S) (x : S)
/-- Evaluate a polynomial `p` given a ring hom `f` from the scalar ring
to the target and a value `x` for the variable in the target -/
irreducible_def eval₂ (p : R[X]) : S :=
p.sum fun e a => f a * x ^ e
#align polynomial.eval₂ Polynomial.eval₂
theorem eval₂_eq_sum {f : R →+* S} {x : S} : p.eval₂ f x = p.sum fun e a => f a * x ^ e := by
rw [eval₂_def]
#align polynomial.eval₂_eq_sum Polynomial.eval₂_eq_sum
theorem eval₂_congr {R S : Type*} [Semiring R] [Semiring S] {f g : R →+* S} {s t : S}
{φ ψ : R[X]} : f = g → s = t → φ = ψ → eval₂ f s φ = eval₂ g t ψ := by
rintro rfl rfl rfl; rfl
#align polynomial.eval₂_congr Polynomial.eval₂_congr
@[simp]
theorem eval₂_at_zero : p.eval₂ f 0 = f (coeff p 0) := by
simp (config := { contextual := true }) only [eval₂_eq_sum, zero_pow_eq, mul_ite, mul_zero,
mul_one, sum, Classical.not_not, mem_support_iff, sum_ite_eq', ite_eq_left_iff,
RingHom.map_zero, imp_true_iff, eq_self_iff_true]
#align polynomial.eval₂_at_zero Polynomial.eval₂_at_zero
@[simp]
theorem eval₂_zero : (0 : R[X]).eval₂ f x = 0 := by simp [eval₂_eq_sum]
#align polynomial.eval₂_zero Polynomial.eval₂_zero
@[simp]
theorem eval₂_C : (C a).eval₂ f x = f a := by simp [eval₂_eq_sum]
#align polynomial.eval₂_C Polynomial.eval₂_C
@[simp]
theorem eval₂_X : X.eval₂ f x = x := by simp [eval₂_eq_sum]
#align polynomial.eval₂_X Polynomial.eval₂_X
@[simp]
theorem eval₂_monomial {n : ℕ} {r : R} : (monomial n r).eval₂ f x = f r * x ^ n := by
simp [eval₂_eq_sum]
#align polynomial.eval₂_monomial Polynomial.eval₂_monomial
@[simp]
theorem eval₂_X_pow {n : ℕ} : (X ^ n).eval₂ f x = x ^ n := by
rw [X_pow_eq_monomial]
convert eval₂_monomial f x (n := n) (r := 1)
simp
#align polynomial.eval₂_X_pow Polynomial.eval₂_X_pow
@[simp]
theorem eval₂_add : (p + q).eval₂ f x = p.eval₂ f x + q.eval₂ f x := by
simp only [eval₂_eq_sum]
apply sum_add_index <;> simp [add_mul]
#align polynomial.eval₂_add Polynomial.eval₂_add
@[simp]
| Mathlib/Algebra/Polynomial/Eval.lean | 95 | 95 | theorem eval₂_one : (1 : R[X]).eval₂ f x = 1 := by | rw [← C_1, eval₂_C, f.map_one]
|
/-
Copyright (c) 2020 Sébastien Gouëzel. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Sébastien Gouëzel, Yury Kudryashov
-/
import Mathlib.Analysis.Calculus.Deriv.Inv
import Mathlib.Analysis.Calculus.Deriv.Polynomial
import Mathlib.Analysis.SpecialFunctions.ExpDeriv
import Mathlib.Analysis.SpecialFunctions.PolynomialExp
#align_import analysis.calculus.bump_function_inner from "leanprover-community/mathlib"@"3bce8d800a6f2b8f63fe1e588fd76a9ff4adcebe"
/-!
# Infinitely smooth transition function
In this file we construct two infinitely smooth functions with properties that an analytic function
cannot have:
* `expNegInvGlue` is equal to zero for `x ≤ 0` and is strictly positive otherwise; it is given by
`x ↦ exp (-1/x)` for `x > 0`;
* `Real.smoothTransition` is equal to zero for `x ≤ 0` and is equal to one for `x ≥ 1`; it is given
by `expNegInvGlue x / (expNegInvGlue x + expNegInvGlue (1 - x))`;
-/
noncomputable section
open scoped Classical Topology
open Polynomial Real Filter Set Function
open scoped Polynomial
/-- `expNegInvGlue` is the real function given by `x ↦ exp (-1/x)` for `x > 0` and `0`
for `x ≤ 0`. It is a basic building block to construct smooth partitions of unity. Its main property
is that it vanishes for `x ≤ 0`, it is positive for `x > 0`, and the junction between the two
behaviors is flat enough to retain smoothness. The fact that this function is `C^∞` is proved in
`expNegInvGlue.contDiff`. -/
def expNegInvGlue (x : ℝ) : ℝ :=
if x ≤ 0 then 0 else exp (-x⁻¹)
#align exp_neg_inv_glue expNegInvGlue
namespace expNegInvGlue
/-- The function `expNegInvGlue` vanishes on `(-∞, 0]`. -/
theorem zero_of_nonpos {x : ℝ} (hx : x ≤ 0) : expNegInvGlue x = 0 := by simp [expNegInvGlue, hx]
#align exp_neg_inv_glue.zero_of_nonpos expNegInvGlue.zero_of_nonpos
@[simp] -- Porting note (#10756): new lemma
protected theorem zero : expNegInvGlue 0 = 0 := zero_of_nonpos le_rfl
/-- The function `expNegInvGlue` is positive on `(0, +∞)`. -/
theorem pos_of_pos {x : ℝ} (hx : 0 < x) : 0 < expNegInvGlue x := by
simp [expNegInvGlue, not_le.2 hx, exp_pos]
#align exp_neg_inv_glue.pos_of_pos expNegInvGlue.pos_of_pos
/-- The function `expNegInvGlue` is nonnegative. -/
theorem nonneg (x : ℝ) : 0 ≤ expNegInvGlue x := by
cases le_or_gt x 0 with
| inl h => exact ge_of_eq (zero_of_nonpos h)
| inr h => exact le_of_lt (pos_of_pos h)
#align exp_neg_inv_glue.nonneg expNegInvGlue.nonneg
-- Porting note (#10756): new lemma
@[simp] theorem zero_iff_nonpos {x : ℝ} : expNegInvGlue x = 0 ↔ x ≤ 0 :=
⟨fun h ↦ not_lt.mp fun h' ↦ (pos_of_pos h').ne' h, zero_of_nonpos⟩
/-!
### Smoothness of `expNegInvGlue`
Porting note: Yury Kudryashov rewrote the proof while porting, generalizing auxiliary lemmas and
removing some auxiliary definitions.
In this section we prove that the function `f = expNegInvGlue` is infinitely smooth. To do
this, we show that $g_p(x)=p(x^{-1})f(x)$ is infinitely smooth for any polynomial `p` with real
coefficients. First we show that $g_p(x)$ tends to zero at zero, then we show that it is
differentiable with derivative $g_p'=g_{x^2(p-p')}$. Finally, we prove smoothness of $g_p$ by
induction, then deduce smoothness of $f$ by setting $p=1$.
-/
#noalign exp_neg_inv_glue.P_aux
#noalign exp_neg_inv_glue.f_aux
#noalign exp_neg_inv_glue.f_aux_zero_eq
#noalign exp_neg_inv_glue.f_aux_deriv
#noalign exp_neg_inv_glue.f_aux_deriv_pos
#noalign exp_neg_inv_glue.f_aux_limit
#noalign exp_neg_inv_glue.f_aux_deriv_zero
#noalign exp_neg_inv_glue.f_aux_has_deriv_at
/-- Our function tends to zero at zero faster than any $P(x^{-1})$, $P∈ℝ[X]$, tends to infinity. -/
theorem tendsto_polynomial_inv_mul_zero (p : ℝ[X]) :
Tendsto (fun x ↦ p.eval x⁻¹ * expNegInvGlue x) (𝓝 0) (𝓝 0) := by
simp only [expNegInvGlue, mul_ite, mul_zero]
refine tendsto_const_nhds.if ?_
simp only [not_le]
have : Tendsto (fun x ↦ p.eval x⁻¹ / exp x⁻¹) (𝓝[>] 0) (𝓝 0) :=
p.tendsto_div_exp_atTop.comp tendsto_inv_zero_atTop
refine this.congr' <| mem_of_superset self_mem_nhdsWithin fun x hx ↦ ?_
simp [expNegInvGlue, hx.out.not_le, exp_neg, div_eq_mul_inv]
| Mathlib/Analysis/SpecialFunctions/SmoothTransition.lean | 101 | 117 | theorem hasDerivAt_polynomial_eval_inv_mul (p : ℝ[X]) (x : ℝ) :
HasDerivAt (fun x ↦ p.eval x⁻¹ * expNegInvGlue x)
((X ^ 2 * (p - derivative (R := ℝ) p)).eval x⁻¹ * expNegInvGlue x) x := by |
rcases lt_trichotomy x 0 with hx | rfl | hx
· rw [zero_of_nonpos hx.le, mul_zero]
refine (hasDerivAt_const _ 0).congr_of_eventuallyEq ?_
filter_upwards [gt_mem_nhds hx] with y hy
rw [zero_of_nonpos hy.le, mul_zero]
· rw [expNegInvGlue.zero, mul_zero, hasDerivAt_iff_tendsto_slope]
refine ((tendsto_polynomial_inv_mul_zero (p * X)).mono_left inf_le_left).congr fun x ↦ ?_
simp [slope_def_field, div_eq_mul_inv, mul_right_comm]
· have := ((p.hasDerivAt x⁻¹).mul (hasDerivAt_neg _).exp).comp x (hasDerivAt_inv hx.ne')
convert this.congr_of_eventuallyEq _ using 1
· simp [expNegInvGlue, hx.not_le]
ring
· filter_upwards [lt_mem_nhds hx] with y hy
simp [expNegInvGlue, hy.not_le]
|
/-
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
-/
import Mathlib.Analysis.SpecialFunctions.Pow.Continuity
import Mathlib.Analysis.SpecialFunctions.Complex.LogDeriv
import Mathlib.Analysis.Calculus.FDeriv.Extend
import Mathlib.Analysis.Calculus.Deriv.Prod
import Mathlib.Analysis.SpecialFunctions.Log.Deriv
import Mathlib.Analysis.SpecialFunctions.Trigonometric.Deriv
#align_import analysis.special_functions.pow.deriv from "leanprover-community/mathlib"@"3bce8d800a6f2b8f63fe1e588fd76a9ff4adcebe"
/-!
# Derivatives of power function on `ℂ`, `ℝ`, `ℝ≥0`, and `ℝ≥0∞`
We also prove differentiability and provide derivatives for the power functions `x ^ y`.
-/
noncomputable section
open scoped Classical Real Topology NNReal ENNReal Filter
open Filter
namespace Complex
theorem hasStrictFDerivAt_cpow {p : ℂ × ℂ} (hp : p.1 ∈ slitPlane) :
HasStrictFDerivAt (fun x : ℂ × ℂ => x.1 ^ x.2)
((p.2 * p.1 ^ (p.2 - 1)) • ContinuousLinearMap.fst ℂ ℂ ℂ +
(p.1 ^ p.2 * log p.1) • ContinuousLinearMap.snd ℂ ℂ ℂ) p := by
have A : p.1 ≠ 0 := slitPlane_ne_zero hp
have : (fun x : ℂ × ℂ => x.1 ^ x.2) =ᶠ[𝓝 p] fun x => exp (log x.1 * x.2) :=
((isOpen_ne.preimage continuous_fst).eventually_mem A).mono fun p hp =>
cpow_def_of_ne_zero hp _
rw [cpow_sub _ _ A, cpow_one, mul_div_left_comm, mul_smul, mul_smul]
refine HasStrictFDerivAt.congr_of_eventuallyEq ?_ this.symm
simpa only [cpow_def_of_ne_zero A, div_eq_mul_inv, mul_smul, add_comm, smul_add] using
((hasStrictFDerivAt_fst.clog hp).mul hasStrictFDerivAt_snd).cexp
#align complex.has_strict_fderiv_at_cpow Complex.hasStrictFDerivAt_cpow
theorem hasStrictFDerivAt_cpow' {x y : ℂ} (hp : x ∈ slitPlane) :
HasStrictFDerivAt (fun x : ℂ × ℂ => x.1 ^ x.2)
((y * x ^ (y - 1)) • ContinuousLinearMap.fst ℂ ℂ ℂ +
(x ^ y * log x) • ContinuousLinearMap.snd ℂ ℂ ℂ) (x, y) :=
@hasStrictFDerivAt_cpow (x, y) hp
#align complex.has_strict_fderiv_at_cpow' Complex.hasStrictFDerivAt_cpow'
| Mathlib/Analysis/SpecialFunctions/Pow/Deriv.lean | 52 | 60 | theorem hasStrictDerivAt_const_cpow {x y : ℂ} (h : x ≠ 0 ∨ y ≠ 0) :
HasStrictDerivAt (fun y => x ^ y) (x ^ y * log x) y := by |
rcases em (x = 0) with (rfl | hx)
· replace h := h.neg_resolve_left rfl
rw [log_zero, mul_zero]
refine (hasStrictDerivAt_const _ 0).congr_of_eventuallyEq ?_
exact (isOpen_ne.eventually_mem h).mono fun y hy => (zero_cpow hy).symm
· simpa only [cpow_def_of_ne_zero hx, mul_one] using
((hasStrictDerivAt_id y).const_mul (log x)).cexp
|
/-
Copyright (c) 2019 Johan Commelin. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johan Commelin, Kenny Lau
-/
import Mathlib.RingTheory.MvPowerSeries.Basic
import Mathlib.Data.Finsupp.Interval
/-!
# Formal (multivariate) power series - Truncation
`MvPowerSeries.trunc n φ` truncates a formal multivariate power series
to the multivariate polynomial that has the same coefficients as `φ`,
for all `m < n`, and `0` otherwise.
Note that here, `m` and `n` have types `σ →₀ ℕ`,
so that `m < n` means that `m ≠ n` and `m s ≤ n s` for all `s : σ`.
-/
noncomputable section
open Finset (antidiagonal mem_antidiagonal)
namespace MvPowerSeries
open Finsupp
variable {σ R : Type*}
section Trunc
variable [CommSemiring R] (n : σ →₀ ℕ)
/-- Auxiliary definition for the truncation function. -/
def truncFun (φ : MvPowerSeries σ R) : MvPolynomial σ R :=
∑ m ∈ Finset.Iio n, MvPolynomial.monomial m (coeff R m φ)
#align mv_power_series.trunc_fun MvPowerSeries.truncFun
theorem coeff_truncFun (m : σ →₀ ℕ) (φ : MvPowerSeries σ R) :
(truncFun n φ).coeff m = if m < n then coeff R m φ else 0 := by
classical
simp [truncFun, MvPolynomial.coeff_sum]
#align mv_power_series.coeff_trunc_fun MvPowerSeries.coeff_truncFun
variable (R)
/-- The `n`th truncation of a multivariate formal power series to a multivariate polynomial -/
def trunc : MvPowerSeries σ R →+ MvPolynomial σ R where
toFun := truncFun n
map_zero' := by
classical
ext
simp [coeff_truncFun]
map_add' := by
classical
intros x y
ext m
simp only [coeff_truncFun, MvPolynomial.coeff_add]
split_ifs
· rw [map_add]
· rw [zero_add]
#align mv_power_series.trunc MvPowerSeries.trunc
variable {R}
| Mathlib/RingTheory/MvPowerSeries/Trunc.lean | 71 | 73 | theorem coeff_trunc (m : σ →₀ ℕ) (φ : MvPowerSeries σ R) :
(trunc R n φ).coeff m = if m < n then coeff R m φ else 0 := by |
classical simp [trunc, coeff_truncFun]
|
/-
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.SetTheory.Game.Ordinal
import Mathlib.SetTheory.Ordinal.NaturalOps
#align_import set_theory.game.birthday from "leanprover-community/mathlib"@"a347076985674932c0e91da09b9961ed0a79508c"
/-!
# Birthdays of games
The birthday of a game is an ordinal that represents at which "step" the game was constructed. We
define it recursively as the least ordinal larger than the birthdays of its left and right games. We
prove the basic properties about these.
# Main declarations
- `SetTheory.PGame.birthday`: The birthday of a pre-game.
# Todo
- Define the birthdays of `SetTheory.Game`s and `Surreal`s.
- Characterize the birthdays of basic arithmetical operations.
-/
universe u
open Ordinal
namespace SetTheory
open scoped NaturalOps PGame
namespace PGame
/-- The birthday of a pre-game is inductively defined as the least strict upper bound of the
birthdays of its left and right games. It may be thought as the "step" in which a certain game is
constructed. -/
noncomputable def birthday : PGame.{u} → Ordinal.{u}
| ⟨_, _, xL, xR⟩ =>
max (lsub.{u, u} fun i => birthday (xL i)) (lsub.{u, u} fun i => birthday (xR i))
#align pgame.birthday SetTheory.PGame.birthday
theorem birthday_def (x : PGame) :
birthday x =
max (lsub.{u, u} fun i => birthday (x.moveLeft i))
(lsub.{u, u} fun i => birthday (x.moveRight i)) := by
cases x; rw [birthday]; rfl
#align pgame.birthday_def SetTheory.PGame.birthday_def
theorem birthday_moveLeft_lt {x : PGame} (i : x.LeftMoves) :
(x.moveLeft i).birthday < x.birthday := by
cases x; rw [birthday]; exact lt_max_of_lt_left (lt_lsub _ i)
#align pgame.birthday_move_left_lt SetTheory.PGame.birthday_moveLeft_lt
theorem birthday_moveRight_lt {x : PGame} (i : x.RightMoves) :
(x.moveRight i).birthday < x.birthday := by
cases x; rw [birthday]; exact lt_max_of_lt_right (lt_lsub _ i)
#align pgame.birthday_move_right_lt SetTheory.PGame.birthday_moveRight_lt
| Mathlib/SetTheory/Game/Birthday.lean | 64 | 78 | theorem lt_birthday_iff {x : PGame} {o : Ordinal} :
o < x.birthday ↔
(∃ i : x.LeftMoves, o ≤ (x.moveLeft i).birthday) ∨
∃ i : x.RightMoves, o ≤ (x.moveRight i).birthday := by |
constructor
· rw [birthday_def]
intro h
cases' lt_max_iff.1 h with h' h'
· left
rwa [lt_lsub_iff] at h'
· right
rwa [lt_lsub_iff] at h'
· rintro (⟨i, hi⟩ | ⟨i, hi⟩)
· exact hi.trans_lt (birthday_moveLeft_lt i)
· exact hi.trans_lt (birthday_moveRight_lt i)
|
/-
Copyright (c) 2014 Jeremy Avigad. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Jeremy Avigad, Andrew Zipperer, Haitao Zhang, Minchao Wu, Yury Kudryashov
-/
import Mathlib.Data.Set.Prod
import Mathlib.Logic.Function.Conjugate
#align_import data.set.function from "leanprover-community/mathlib"@"996b0ff959da753a555053a480f36e5f264d4207"
/-!
# Functions over sets
## Main definitions
### Predicate
* `Set.EqOn f₁ f₂ s` : functions `f₁` and `f₂` are equal at every point of `s`;
* `Set.MapsTo f s t` : `f` sends every point of `s` to a point of `t`;
* `Set.InjOn f s` : restriction of `f` to `s` is injective;
* `Set.SurjOn f s t` : every point in `s` has a preimage in `s`;
* `Set.BijOn f s t` : `f` is a bijection between `s` and `t`;
* `Set.LeftInvOn f' f s` : for every `x ∈ s` we have `f' (f x) = x`;
* `Set.RightInvOn f' f t` : for every `y ∈ t` we have `f (f' y) = y`;
* `Set.InvOn f' f s t` : `f'` is a two-side inverse of `f` on `s` and `t`, i.e.
we have `Set.LeftInvOn f' f s` and `Set.RightInvOn f' f t`.
### Functions
* `Set.restrict f s` : restrict the domain of `f` to the set `s`;
* `Set.codRestrict f s h` : given `h : ∀ x, f x ∈ s`, restrict the codomain of `f` to the set `s`;
* `Set.MapsTo.restrict f s t h`: given `h : MapsTo f s t`, restrict the domain of `f` to `s`
and the codomain to `t`.
-/
variable {α β γ : Type*} {ι : Sort*} {π : α → Type*}
open Equiv Equiv.Perm Function
namespace Set
/-! ### Restrict -/
section restrict
/-- Restrict domain of a function `f` to a set `s`. Same as `Subtype.restrict` but this version
takes an argument `↥s` instead of `Subtype s`. -/
def restrict (s : Set α) (f : ∀ a : α, π a) : ∀ a : s, π a := fun x => f x
#align set.restrict Set.restrict
theorem restrict_eq (f : α → β) (s : Set α) : s.restrict f = f ∘ Subtype.val :=
rfl
#align set.restrict_eq Set.restrict_eq
@[simp]
theorem restrict_apply (f : α → β) (s : Set α) (x : s) : s.restrict f x = f x :=
rfl
#align set.restrict_apply Set.restrict_apply
theorem restrict_eq_iff {f : ∀ a, π a} {s : Set α} {g : ∀ a : s, π a} :
restrict s f = g ↔ ∀ (a) (ha : a ∈ s), f a = g ⟨a, ha⟩ :=
funext_iff.trans Subtype.forall
#align set.restrict_eq_iff Set.restrict_eq_iff
theorem eq_restrict_iff {s : Set α} {f : ∀ a : s, π a} {g : ∀ a, π a} :
f = restrict s g ↔ ∀ (a) (ha : a ∈ s), f ⟨a, ha⟩ = g a :=
funext_iff.trans Subtype.forall
#align set.eq_restrict_iff Set.eq_restrict_iff
@[simp]
theorem range_restrict (f : α → β) (s : Set α) : Set.range (s.restrict f) = f '' s :=
(range_comp _ _).trans <| congr_arg (f '' ·) Subtype.range_coe
#align set.range_restrict Set.range_restrict
theorem image_restrict (f : α → β) (s t : Set α) :
s.restrict f '' (Subtype.val ⁻¹' t) = f '' (t ∩ s) := by
rw [restrict_eq, image_comp, image_preimage_eq_inter_range, Subtype.range_coe]
#align set.image_restrict Set.image_restrict
@[simp]
theorem restrict_dite {s : Set α} [∀ x, Decidable (x ∈ s)] (f : ∀ a ∈ s, β)
(g : ∀ a ∉ s, β) :
(s.restrict fun a => if h : a ∈ s then f a h else g a h) = (fun a : s => f a a.2) :=
funext fun a => dif_pos a.2
#align set.restrict_dite Set.restrict_dite
@[simp]
theorem restrict_dite_compl {s : Set α} [∀ x, Decidable (x ∈ s)] (f : ∀ a ∈ s, β)
(g : ∀ a ∉ s, β) :
(sᶜ.restrict fun a => if h : a ∈ s then f a h else g a h) = (fun a : (sᶜ : Set α) => g a a.2) :=
funext fun a => dif_neg a.2
#align set.restrict_dite_compl Set.restrict_dite_compl
@[simp]
theorem restrict_ite (f g : α → β) (s : Set α) [∀ x, Decidable (x ∈ s)] :
(s.restrict fun a => if a ∈ s then f a else g a) = s.restrict f :=
restrict_dite _ _
#align set.restrict_ite Set.restrict_ite
@[simp]
theorem restrict_ite_compl (f g : α → β) (s : Set α) [∀ x, Decidable (x ∈ s)] :
(sᶜ.restrict fun a => if a ∈ s then f a else g a) = sᶜ.restrict g :=
restrict_dite_compl _ _
#align set.restrict_ite_compl Set.restrict_ite_compl
@[simp]
theorem restrict_piecewise (f g : α → β) (s : Set α) [∀ x, Decidable (x ∈ s)] :
s.restrict (piecewise s f g) = s.restrict f :=
restrict_ite _ _ _
#align set.restrict_piecewise Set.restrict_piecewise
@[simp]
theorem restrict_piecewise_compl (f g : α → β) (s : Set α) [∀ x, Decidable (x ∈ s)] :
sᶜ.restrict (piecewise s f g) = sᶜ.restrict g :=
restrict_ite_compl _ _ _
#align set.restrict_piecewise_compl Set.restrict_piecewise_compl
| Mathlib/Data/Set/Function.lean | 117 | 120 | theorem restrict_extend_range (f : α → β) (g : α → γ) (g' : β → γ) :
(range f).restrict (extend f g g') = fun x => g x.coe_prop.choose := by |
classical
exact restrict_dite _ _
|
/-
Copyright (c) 2022 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov, Yaël Dillies
-/
import Mathlib.LinearAlgebra.Ray
import Mathlib.Analysis.NormedSpace.Real
#align_import analysis.normed_space.ray from "leanprover-community/mathlib"@"92ca63f0fb391a9ca5f22d2409a6080e786d99f7"
/-!
# Rays in a real normed vector space
In this file we prove some lemmas about the `SameRay` predicate in case of a real normed space. In
this case, for two vectors `x y` in the same ray, the norm of their sum is equal to the sum of their
norms and `‖y‖ • x = ‖x‖ • y`.
-/
open Real
variable {E : Type*} [SeminormedAddCommGroup E] [NormedSpace ℝ E] {F : Type*}
[NormedAddCommGroup F] [NormedSpace ℝ F]
namespace SameRay
variable {x y : E}
/-- If `x` and `y` are on the same ray, then the triangle inequality becomes the equality: the norm
of `x + y` is the sum of the norms of `x` and `y`. The converse is true for a strictly convex
space. -/
theorem norm_add (h : SameRay ℝ x y) : ‖x + y‖ = ‖x‖ + ‖y‖ := by
rcases h.exists_eq_smul with ⟨u, a, b, ha, hb, -, rfl, rfl⟩
rw [← add_smul, norm_smul_of_nonneg (add_nonneg ha hb), norm_smul_of_nonneg ha,
norm_smul_of_nonneg hb, add_mul]
#align same_ray.norm_add SameRay.norm_add
theorem norm_sub (h : SameRay ℝ x y) : ‖x - y‖ = |‖x‖ - ‖y‖| := by
rcases h.exists_eq_smul with ⟨u, a, b, ha, hb, -, rfl, rfl⟩
wlog hab : b ≤ a generalizing a b with H
· rw [SameRay.sameRay_comm] at h
rw [norm_sub_rev, abs_sub_comm]
exact H b a hb ha h (le_of_not_le hab)
rw [← sub_nonneg] at hab
rw [← sub_smul, norm_smul_of_nonneg hab, norm_smul_of_nonneg ha, norm_smul_of_nonneg hb, ←
sub_mul, abs_of_nonneg (mul_nonneg hab (norm_nonneg _))]
#align same_ray.norm_sub SameRay.norm_sub
theorem norm_smul_eq (h : SameRay ℝ x y) : ‖x‖ • y = ‖y‖ • x := by
rcases h.exists_eq_smul with ⟨u, a, b, ha, hb, -, rfl, rfl⟩
simp only [norm_smul_of_nonneg, *, mul_smul]
rw [smul_comm, smul_comm b, smul_comm a b u]
#align same_ray.norm_smul_eq SameRay.norm_smul_eq
end SameRay
variable {x y : F}
theorem norm_injOn_ray_left (hx : x ≠ 0) : { y | SameRay ℝ x y }.InjOn norm := by
rintro y hy z hz h
rcases hy.exists_nonneg_left hx with ⟨r, hr, rfl⟩
rcases hz.exists_nonneg_left hx with ⟨s, hs, rfl⟩
rw [norm_smul, norm_smul, mul_left_inj' (norm_ne_zero_iff.2 hx), norm_of_nonneg hr,
norm_of_nonneg hs] at h
rw [h]
#align norm_inj_on_ray_left norm_injOn_ray_left
| Mathlib/Analysis/NormedSpace/Ray.lean | 68 | 69 | theorem norm_injOn_ray_right (hy : y ≠ 0) : { x | SameRay ℝ x y }.InjOn norm := by |
simpa only [SameRay.sameRay_comm] using norm_injOn_ray_left hy
|
/-
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.Data.Fin.Tuple.Basic
import Mathlib.Data.List.Range
#align_import data.fin.vec_notation from "leanprover-community/mathlib"@"2445c98ae4b87eabebdde552593519b9b6dc350c"
/-!
# Matrix and vector notation
This file defines notation for vectors and matrices. Given `a b c d : α`,
the notation allows us to write `![a, b, c, d] : Fin 4 → α`.
Nesting vectors gives coefficients of a matrix, so `![![a, b], ![c, d]] : Fin 2 → Fin 2 → α`.
In later files we introduce `!![a, b; c, d]` as notation for `Matrix.of ![![a, b], ![c, d]]`.
## Main definitions
* `vecEmpty` is the empty vector (or `0` by `n` matrix) `![]`
* `vecCons` prepends an entry to a vector, so `![a, b]` is `vecCons a (vecCons b vecEmpty)`
## Implementation notes
The `simp` lemmas require that one of the arguments is of the form `vecCons _ _`.
This ensures `simp` works with entries only when (some) entries are already given.
In other words, this notation will only appear in the output of `simp` if it
already appears in the input.
## Notations
The main new notation is `![a, b]`, which gets expanded to `vecCons a (vecCons b vecEmpty)`.
## Examples
Examples of usage can be found in the `test/matrix.lean` file.
-/
namespace Matrix
universe u
variable {α : Type u}
section MatrixNotation
/-- `![]` is the vector with no entries. -/
def vecEmpty : Fin 0 → α :=
Fin.elim0
#align matrix.vec_empty Matrix.vecEmpty
/-- `vecCons h t` prepends an entry `h` to a vector `t`.
The inverse functions are `vecHead` and `vecTail`.
The notation `![a, b, ...]` expands to `vecCons a (vecCons b ...)`.
-/
def vecCons {n : ℕ} (h : α) (t : Fin n → α) : Fin n.succ → α :=
Fin.cons h t
#align matrix.vec_cons Matrix.vecCons
/-- `![...]` notation is used to construct a vector `Fin n → α` using `Matrix.vecEmpty` and
`Matrix.vecCons`.
For instance, `![a, b, c] : Fin 3` is syntax for `vecCons a (vecCons b (vecCons c vecEmpty))`.
Note that this should not be used as syntax for `Matrix` as it generates a term with the wrong type.
The `!![a, b; c, d]` syntax (provided by `Matrix.matrixNotation`) should be used instead.
-/
syntax (name := vecNotation) "![" term,* "]" : term
macro_rules
| `(![$term:term, $terms:term,*]) => `(vecCons $term ![$terms,*])
| `(![$term:term]) => `(vecCons $term ![])
| `(![]) => `(vecEmpty)
/-- Unexpander for the `![x, y, ...]` notation. -/
@[app_unexpander vecCons]
def vecConsUnexpander : Lean.PrettyPrinter.Unexpander
| `($_ $term ![$term2, $terms,*]) => `(![$term, $term2, $terms,*])
| `($_ $term ![$term2]) => `(![$term, $term2])
| `($_ $term ![]) => `(![$term])
| _ => throw ()
/-- Unexpander for the `![]` notation. -/
@[app_unexpander vecEmpty]
def vecEmptyUnexpander : Lean.PrettyPrinter.Unexpander
| `($_:ident) => `(![])
| _ => throw ()
/-- `vecHead v` gives the first entry of the vector `v` -/
def vecHead {n : ℕ} (v : Fin n.succ → α) : α :=
v 0
#align matrix.vec_head Matrix.vecHead
/-- `vecTail v` gives a vector consisting of all entries of `v` except the first -/
def vecTail {n : ℕ} (v : Fin n.succ → α) : Fin n → α :=
v ∘ Fin.succ
#align matrix.vec_tail Matrix.vecTail
variable {m n : ℕ}
/-- Use `![...]` notation for displaying a vector `Fin n → α`, for example:
```
#eval ![1, 2] + ![3, 4] -- ![4, 6]
```
-/
instance _root_.PiFin.hasRepr [Repr α] : Repr (Fin n → α) where
reprPrec f _ :=
Std.Format.bracket "![" (Std.Format.joinSep
((List.finRange n).map fun n => repr (f n)) ("," ++ Std.Format.line)) "]"
#align pi_fin.has_repr PiFin.hasRepr
end MatrixNotation
variable {m n o : ℕ} {m' n' o' : Type*}
theorem empty_eq (v : Fin 0 → α) : v = ![] :=
Subsingleton.elim _ _
#align matrix.empty_eq Matrix.empty_eq
section Val
@[simp]
theorem head_fin_const (a : α) : (vecHead fun _ : Fin (n + 1) => a) = a :=
rfl
#align matrix.head_fin_const Matrix.head_fin_const
@[simp]
theorem cons_val_zero (x : α) (u : Fin m → α) : vecCons x u 0 = x :=
rfl
#align matrix.cons_val_zero Matrix.cons_val_zero
theorem cons_val_zero' (h : 0 < m.succ) (x : α) (u : Fin m → α) : vecCons x u ⟨0, h⟩ = x :=
rfl
#align matrix.cons_val_zero' Matrix.cons_val_zero'
@[simp]
theorem cons_val_succ (x : α) (u : Fin m → α) (i : Fin m) : vecCons x u i.succ = u i := by
simp [vecCons]
#align matrix.cons_val_succ Matrix.cons_val_succ
@[simp]
| Mathlib/Data/Fin/VecNotation.lean | 146 | 148 | theorem cons_val_succ' {i : ℕ} (h : i.succ < m.succ) (x : α) (u : Fin m → α) :
vecCons x u ⟨i.succ, h⟩ = u ⟨i, Nat.lt_of_succ_lt_succ h⟩ := by |
simp only [vecCons, Fin.cons, Fin.cases_succ']
|
/-
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.Analysis.Normed.Group.Basic
#align_import analysis.normed.group.hom from "leanprover-community/mathlib"@"3c4225288b55380a90df078ebae0991080b12393"
/-!
# Normed groups homomorphisms
This file gathers definitions and elementary constructions about bounded group homomorphisms
between normed (abelian) groups (abbreviated to "normed group homs").
The main lemmas relate the boundedness condition to continuity and Lipschitzness.
The main construction is to endow the type of normed group homs between two given normed groups
with a group structure and a norm, giving rise to a normed group structure. We provide several
simple constructions for normed group homs, like kernel, range and equalizer.
Some easy other constructions are related to subgroups of normed groups.
Since a lot of elementary properties don't require `‖x‖ = 0 → x = 0` we start setting up the
theory of `SeminormedAddGroupHom` and we specialize to `NormedAddGroupHom` when needed.
-/
noncomputable section
open NNReal
-- TODO: migrate to the new morphism / morphism_class style
/-- A morphism of seminormed abelian groups is a bounded group homomorphism. -/
structure NormedAddGroupHom (V W : Type*) [SeminormedAddCommGroup V]
[SeminormedAddCommGroup W] where
/-- The function underlying a `NormedAddGroupHom` -/
toFun : V → W
/-- A `NormedAddGroupHom` is additive. -/
map_add' : ∀ v₁ v₂, toFun (v₁ + v₂) = toFun v₁ + toFun v₂
/-- A `NormedAddGroupHom` is bounded. -/
bound' : ∃ C, ∀ v, ‖toFun v‖ ≤ C * ‖v‖
#align normed_add_group_hom NormedAddGroupHom
namespace AddMonoidHom
variable {V W : Type*} [SeminormedAddCommGroup V] [SeminormedAddCommGroup W]
{f g : NormedAddGroupHom V W}
/-- Associate to a group homomorphism a bounded group homomorphism under a norm control condition.
See `AddMonoidHom.mkNormedAddGroupHom'` for a version that uses `ℝ≥0` for the bound. -/
def mkNormedAddGroupHom (f : V →+ W) (C : ℝ) (h : ∀ v, ‖f v‖ ≤ C * ‖v‖) : NormedAddGroupHom V W :=
{ f with bound' := ⟨C, h⟩ }
#align add_monoid_hom.mk_normed_add_group_hom AddMonoidHom.mkNormedAddGroupHom
/-- Associate to a group homomorphism a bounded group homomorphism under a norm control condition.
See `AddMonoidHom.mkNormedAddGroupHom` for a version that uses `ℝ` for the bound. -/
def mkNormedAddGroupHom' (f : V →+ W) (C : ℝ≥0) (hC : ∀ x, ‖f x‖₊ ≤ C * ‖x‖₊) :
NormedAddGroupHom V W :=
{ f with bound' := ⟨C, hC⟩ }
#align add_monoid_hom.mk_normed_add_group_hom' AddMonoidHom.mkNormedAddGroupHom'
end AddMonoidHom
theorem exists_pos_bound_of_bound {V W : Type*} [SeminormedAddCommGroup V]
[SeminormedAddCommGroup W] {f : V → W} (M : ℝ) (h : ∀ x, ‖f x‖ ≤ M * ‖x‖) :
∃ N, 0 < N ∧ ∀ x, ‖f x‖ ≤ N * ‖x‖ :=
⟨max M 1, lt_of_lt_of_le zero_lt_one (le_max_right _ _), fun x =>
calc
‖f x‖ ≤ M * ‖x‖ := h x
_ ≤ max M 1 * ‖x‖ := by gcongr; apply le_max_left
⟩
#align exists_pos_bound_of_bound exists_pos_bound_of_bound
namespace NormedAddGroupHom
variable {V V₁ V₂ V₃ : Type*} [SeminormedAddCommGroup V] [SeminormedAddCommGroup V₁]
[SeminormedAddCommGroup V₂] [SeminormedAddCommGroup V₃]
variable {f g : NormedAddGroupHom V₁ V₂}
/-- A Lipschitz continuous additive homomorphism is a normed additive group homomorphism. -/
def ofLipschitz (f : V₁ →+ V₂) {K : ℝ≥0} (h : LipschitzWith K f) : NormedAddGroupHom V₁ V₂ :=
f.mkNormedAddGroupHom K fun x ↦ by simpa only [map_zero, dist_zero_right] using h.dist_le_mul x 0
instance funLike : FunLike (NormedAddGroupHom V₁ V₂) V₁ V₂ where
coe := toFun
coe_injective' := fun f g h => by cases f; cases g; congr
-- Porting note: moved this declaration up so we could get a `FunLike` instance sooner.
instance toAddMonoidHomClass : AddMonoidHomClass (NormedAddGroupHom V₁ V₂) V₁ V₂ where
map_add f := f.map_add'
map_zero f := (AddMonoidHom.mk' f.toFun f.map_add').map_zero
initialize_simps_projections NormedAddGroupHom (toFun → apply)
theorem coe_inj (H : (f : V₁ → V₂) = g) : f = g := by
cases f; cases g; congr
#align normed_add_group_hom.coe_inj NormedAddGroupHom.coe_inj
| Mathlib/Analysis/Normed/Group/Hom.lean | 103 | 104 | theorem coe_injective : @Function.Injective (NormedAddGroupHom V₁ V₂) (V₁ → V₂) toFun := by |
apply coe_inj
|
/-
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.AlgebraMap
import Mathlib.Algebra.Polynomial.Degree.Lemmas
import Mathlib.Algebra.Polynomial.HasseDeriv
#align_import data.polynomial.taylor from "leanprover-community/mathlib"@"70fd9563a21e7b963887c9360bd29b2393e6225a"
/-!
# Taylor expansions of polynomials
## Main declarations
* `Polynomial.taylor`: the Taylor expansion of the polynomial `f` at `r`
* `Polynomial.taylor_coeff`: the `k`th coefficient of `taylor r f` is
`(Polynomial.hasseDeriv k f).eval r`
* `Polynomial.eq_zero_of_hasseDeriv_eq_zero`:
the identity principle: a polynomial is 0 iff all its Hasse derivatives are zero
-/
noncomputable section
namespace Polynomial
open Polynomial
variable {R : Type*} [Semiring R] (r : R) (f : R[X])
/-- The Taylor expansion of a polynomial `f` at `r`. -/
def taylor (r : R) : R[X] →ₗ[R] R[X] where
toFun f := f.comp (X + C r)
map_add' f g := add_comp
map_smul' c f := by simp only [smul_eq_C_mul, C_mul_comp, RingHom.id_apply]
#align polynomial.taylor Polynomial.taylor
theorem taylor_apply : taylor r f = f.comp (X + C r) :=
rfl
#align polynomial.taylor_apply Polynomial.taylor_apply
@[simp]
theorem taylor_X : taylor r X = X + C r := by simp only [taylor_apply, X_comp]
set_option linter.uppercaseLean3 false in
#align polynomial.taylor_X Polynomial.taylor_X
@[simp]
theorem taylor_C (x : R) : taylor r (C x) = C x := by simp only [taylor_apply, C_comp]
set_option linter.uppercaseLean3 false in
#align polynomial.taylor_C Polynomial.taylor_C
@[simp]
| Mathlib/Algebra/Polynomial/Taylor.lean | 56 | 59 | theorem taylor_zero' : taylor (0 : R) = LinearMap.id := by |
ext
simp only [taylor_apply, add_zero, comp_X, _root_.map_zero, LinearMap.id_comp,
Function.comp_apply, LinearMap.coe_comp]
|
/-
Copyright (c) 2020 Heather Macbeth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Heather Macbeth
-/
import Mathlib.Analysis.NormedSpace.HahnBanach.Extension
import Mathlib.Analysis.NormedSpace.RCLike
import Mathlib.Analysis.LocallyConvex.Polar
#align_import analysis.normed_space.dual from "leanprover-community/mathlib"@"f2ce6086713c78a7f880485f7917ea547a215982"
/-!
# The topological dual of a normed space
In this file we define the topological dual `NormedSpace.Dual` of a normed space, and the
continuous linear map `NormedSpace.inclusionInDoubleDual` from a normed space into its double
dual.
For base field `𝕜 = ℝ` or `𝕜 = ℂ`, this map is actually an isometric embedding; we provide a
version `NormedSpace.inclusionInDoubleDualLi` of the map which is of type a bundled linear
isometric embedding, `E →ₗᵢ[𝕜] (Dual 𝕜 (Dual 𝕜 E))`.
Since a lot of elementary properties don't require `eq_of_dist_eq_zero` we start setting up the
theory for `SeminormedAddCommGroup` and we specialize to `NormedAddCommGroup` when needed.
## Main definitions
* `inclusionInDoubleDual` and `inclusionInDoubleDualLi` are the inclusion of a normed space
in its double dual, considered as a bounded linear map and as a linear isometry, respectively.
* `polar 𝕜 s` is the subset of `Dual 𝕜 E` consisting of those functionals `x'` for which
`‖x' z‖ ≤ 1` for every `z ∈ s`.
## Tags
dual
-/
noncomputable section
open scoped Classical
open Topology Bornology
universe u v
namespace NormedSpace
section General
variable (𝕜 : Type*) [NontriviallyNormedField 𝕜]
variable (E : Type*) [SeminormedAddCommGroup E] [NormedSpace 𝕜 E]
variable (F : Type*) [NormedAddCommGroup F] [NormedSpace 𝕜 F]
/-- The topological dual of a seminormed space `E`. -/
abbrev Dual : Type _ := E →L[𝕜] 𝕜
#align normed_space.dual NormedSpace.Dual
-- TODO: helper instance for elaboration of inclusionInDoubleDual_norm_eq until
-- leanprover/lean4#2522 is resolved; remove once fixed
instance : NormedSpace 𝕜 (Dual 𝕜 E) := inferInstance
-- TODO: helper instance for elaboration of inclusionInDoubleDual_norm_le until
-- leanprover/lean4#2522 is resolved; remove once fixed
instance : SeminormedAddCommGroup (Dual 𝕜 E) := inferInstance
/-- The inclusion of a normed space in its double (topological) dual, considered
as a bounded linear map. -/
def inclusionInDoubleDual : E →L[𝕜] Dual 𝕜 (Dual 𝕜 E) :=
ContinuousLinearMap.apply 𝕜 𝕜
#align normed_space.inclusion_in_double_dual NormedSpace.inclusionInDoubleDual
@[simp]
theorem dual_def (x : E) (f : Dual 𝕜 E) : inclusionInDoubleDual 𝕜 E x f = f x :=
rfl
#align normed_space.dual_def NormedSpace.dual_def
theorem inclusionInDoubleDual_norm_eq :
‖inclusionInDoubleDual 𝕜 E‖ = ‖ContinuousLinearMap.id 𝕜 (Dual 𝕜 E)‖ :=
ContinuousLinearMap.opNorm_flip _
#align normed_space.inclusion_in_double_dual_norm_eq NormedSpace.inclusionInDoubleDual_norm_eq
| Mathlib/Analysis/NormedSpace/Dual.lean | 82 | 84 | theorem inclusionInDoubleDual_norm_le : ‖inclusionInDoubleDual 𝕜 E‖ ≤ 1 := by |
rw [inclusionInDoubleDual_norm_eq]
exact ContinuousLinearMap.norm_id_le
|
/-
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
| Mathlib/Analysis/NormedSpace/Pointwise.lean | 57 | 66 | 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]
|
/-
Copyright (c) 2022 Yakov Pechersky. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yakov Pechersky
-/
import Mathlib.Data.List.Infix
#align_import data.list.rdrop from "leanprover-community/mathlib"@"26f081a2fb920140ed5bc5cc5344e84bcc7cb2b2"
/-!
# Dropping or taking from lists on the right
Taking or removing element from the tail end of a list
## Main definitions
- `rdrop n`: drop `n : ℕ` elements from the tail
- `rtake n`: take `n : ℕ` elements from the tail
- `rdropWhile p`: remove all the elements from the tail of a list until it finds the first element
for which `p : α → Bool` returns false. This element and everything before is returned.
- `rtakeWhile p`: Returns the longest terminal segment of a list for which `p : α → Bool` returns
true.
## Implementation detail
The two predicate-based methods operate by performing the regular "from-left" operation on
`List.reverse`, followed by another `List.reverse`, so they are not the most performant.
The other two rely on `List.length l` so they still traverse the list twice. One could construct
another function that takes a `L : ℕ` and use `L - n`. Under a proof condition that
`L = l.length`, the function would do the right thing.
-/
-- Make sure we don't import algebra
assert_not_exists Monoid
variable {α : Type*} (p : α → Bool) (l : List α) (n : ℕ)
namespace List
/-- Drop `n` elements from the tail end of a list. -/
def rdrop : List α :=
l.take (l.length - n)
#align list.rdrop List.rdrop
@[simp]
theorem rdrop_nil : rdrop ([] : List α) n = [] := by simp [rdrop]
#align list.rdrop_nil List.rdrop_nil
@[simp]
| Mathlib/Data/List/DropRight.lean | 51 | 51 | theorem rdrop_zero : rdrop l 0 = l := by | simp [rdrop]
|
/-
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.Order.Interval.Finset.Nat
#align_import data.fin.interval from "leanprover-community/mathlib"@"1d29de43a5ba4662dd33b5cfeecfc2a27a5a8a29"
/-!
# Finite intervals in `Fin n`
This file proves that `Fin n` is a `LocallyFiniteOrder` and calculates the cardinality of its
intervals as Finsets and Fintypes.
-/
assert_not_exists MonoidWithZero
namespace Fin
variable {n : ℕ} (a b : Fin n)
@[simp, norm_cast]
theorem coe_sup : ↑(a ⊔ b) = (a ⊔ b : ℕ) := rfl
#align fin.coe_sup Fin.coe_sup
@[simp, norm_cast]
theorem coe_inf : ↑(a ⊓ b) = (a ⊓ b : ℕ) := rfl
#align fin.coe_inf Fin.coe_inf
@[simp, norm_cast]
theorem coe_max : ↑(max a b) = (max a b : ℕ) := rfl
#align fin.coe_max Fin.coe_max
@[simp, norm_cast]
theorem coe_min : ↑(min a b) = (min a b : ℕ) := rfl
#align fin.coe_min Fin.coe_min
end Fin
open Finset Fin Function
namespace Fin
variable (n : ℕ)
instance instLocallyFiniteOrder : LocallyFiniteOrder (Fin n) :=
OrderIso.locallyFiniteOrder Fin.orderIsoSubtype
instance instLocallyFiniteOrderBot : LocallyFiniteOrderBot (Fin n) :=
OrderIso.locallyFiniteOrderBot Fin.orderIsoSubtype
instance instLocallyFiniteOrderTop : ∀ n, LocallyFiniteOrderTop (Fin n)
| 0 => IsEmpty.toLocallyFiniteOrderTop
| _ + 1 => inferInstance
variable {n} (a b : Fin n)
theorem Icc_eq_finset_subtype : Icc a b = (Icc (a : ℕ) b).fin n :=
rfl
#align fin.Icc_eq_finset_subtype Fin.Icc_eq_finset_subtype
theorem Ico_eq_finset_subtype : Ico a b = (Ico (a : ℕ) b).fin n :=
rfl
#align fin.Ico_eq_finset_subtype Fin.Ico_eq_finset_subtype
theorem Ioc_eq_finset_subtype : Ioc a b = (Ioc (a : ℕ) b).fin n :=
rfl
#align fin.Ioc_eq_finset_subtype Fin.Ioc_eq_finset_subtype
theorem Ioo_eq_finset_subtype : Ioo a b = (Ioo (a : ℕ) b).fin n :=
rfl
#align fin.Ioo_eq_finset_subtype Fin.Ioo_eq_finset_subtype
theorem uIcc_eq_finset_subtype : uIcc a b = (uIcc (a : ℕ) b).fin n := rfl
#align fin.uIcc_eq_finset_subtype Fin.uIcc_eq_finset_subtype
@[simp]
theorem map_valEmbedding_Icc : (Icc a b).map Fin.valEmbedding = Icc ↑a ↑b := by
simp [Icc_eq_finset_subtype, Finset.fin, Finset.map_map, Icc_filter_lt_of_lt_right]
#align fin.map_subtype_embedding_Icc Fin.map_valEmbedding_Icc
@[simp]
theorem map_valEmbedding_Ico : (Ico a b).map Fin.valEmbedding = Ico ↑a ↑b := by
simp [Ico_eq_finset_subtype, Finset.fin, Finset.map_map]
#align fin.map_subtype_embedding_Ico Fin.map_valEmbedding_Ico
@[simp]
theorem map_valEmbedding_Ioc : (Ioc a b).map Fin.valEmbedding = Ioc ↑a ↑b := by
simp [Ioc_eq_finset_subtype, Finset.fin, Finset.map_map, Ioc_filter_lt_of_lt_right]
#align fin.map_subtype_embedding_Ioc Fin.map_valEmbedding_Ioc
@[simp]
theorem map_valEmbedding_Ioo : (Ioo a b).map Fin.valEmbedding = Ioo ↑a ↑b := by
simp [Ioo_eq_finset_subtype, Finset.fin, Finset.map_map]
#align fin.map_subtype_embedding_Ioo Fin.map_valEmbedding_Ioo
@[simp]
theorem map_subtype_embedding_uIcc : (uIcc a b).map valEmbedding = uIcc ↑a ↑b :=
map_valEmbedding_Icc _ _
#align fin.map_subtype_embedding_uIcc Fin.map_subtype_embedding_uIcc
@[simp]
theorem card_Icc : (Icc a b).card = b + 1 - a := by
rw [← Nat.card_Icc, ← map_valEmbedding_Icc, card_map]
#align fin.card_Icc Fin.card_Icc
@[simp]
theorem card_Ico : (Ico a b).card = b - a := by
rw [← Nat.card_Ico, ← map_valEmbedding_Ico, card_map]
#align fin.card_Ico Fin.card_Ico
@[simp]
theorem card_Ioc : (Ioc a b).card = b - a := by
rw [← Nat.card_Ioc, ← map_valEmbedding_Ioc, card_map]
#align fin.card_Ioc Fin.card_Ioc
@[simp]
theorem card_Ioo : (Ioo a b).card = b - a - 1 := by
rw [← Nat.card_Ioo, ← map_valEmbedding_Ioo, card_map]
#align fin.card_Ioo Fin.card_Ioo
@[simp]
| Mathlib/Order/Interval/Finset/Fin.lean | 124 | 125 | theorem card_uIcc : (uIcc a b).card = (b - a : ℤ).natAbs + 1 := by |
rw [← Nat.card_uIcc, ← map_subtype_embedding_uIcc, card_map]
|
/-
Copyright (c) 2020 Anne Baanen. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Anne Baanen, Devon Tuma
-/
import Mathlib.Algebra.GroupWithZero.NonZeroDivisors
import Mathlib.Algebra.Polynomial.AlgebraMap
import Mathlib.RingTheory.Coprime.Basic
import Mathlib.Tactic.AdaptationNote
#align_import ring_theory.polynomial.scale_roots from "leanprover-community/mathlib"@"40ac1b258344e0c2b4568dc37bfad937ec35a727"
/-!
# Scaling the roots of a polynomial
This file defines `scaleRoots p s` for a polynomial `p` in one variable and a ring element `s` to
be the polynomial with root `r * s` for each root `r` of `p` and proves some basic results about it.
-/
variable {R S A K : Type*}
namespace Polynomial
open Polynomial
section Semiring
variable [Semiring R] [Semiring S]
/-- `scaleRoots p s` is a polynomial with root `r * s` for each root `r` of `p`. -/
noncomputable def scaleRoots (p : R[X]) (s : R) : R[X] :=
∑ i ∈ p.support, monomial i (p.coeff i * s ^ (p.natDegree - i))
#align polynomial.scale_roots Polynomial.scaleRoots
@[simp]
theorem coeff_scaleRoots (p : R[X]) (s : R) (i : ℕ) :
(scaleRoots p s).coeff i = coeff p i * s ^ (p.natDegree - i) := by
simp (config := { contextual := true }) [scaleRoots, coeff_monomial]
#align polynomial.coeff_scale_roots Polynomial.coeff_scaleRoots
theorem coeff_scaleRoots_natDegree (p : R[X]) (s : R) :
(scaleRoots p s).coeff p.natDegree = p.leadingCoeff := by
rw [leadingCoeff, coeff_scaleRoots, tsub_self, pow_zero, mul_one]
#align polynomial.coeff_scale_roots_nat_degree Polynomial.coeff_scaleRoots_natDegree
@[simp]
theorem zero_scaleRoots (s : R) : scaleRoots 0 s = 0 := by
ext
simp
#align polynomial.zero_scale_roots Polynomial.zero_scaleRoots
| Mathlib/RingTheory/Polynomial/ScaleRoots.lean | 53 | 59 | theorem scaleRoots_ne_zero {p : R[X]} (hp : p ≠ 0) (s : R) : scaleRoots p s ≠ 0 := by |
intro h
have : p.coeff p.natDegree ≠ 0 := mt leadingCoeff_eq_zero.mp hp
have : (scaleRoots p s).coeff p.natDegree = 0 :=
congr_fun (congr_arg (coeff : R[X] → ℕ → R) h) p.natDegree
rw [coeff_scaleRoots_natDegree] at this
contradiction
|
/-
Copyright (c) 2020 Yury Kudryashov. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Yury Kudryashov, Eric Wieser
-/
import Mathlib.Algebra.Quaternion
import Mathlib.Analysis.InnerProductSpace.Basic
import Mathlib.Analysis.InnerProductSpace.PiL2
import Mathlib.Topology.Algebra.Algebra
#align_import analysis.quaternion from "leanprover-community/mathlib"@"07992a1d1f7a4176c6d3f160209608be4e198566"
/-!
# Quaternions as a normed algebra
In this file we define the following structures on the space `ℍ := ℍ[ℝ]` of quaternions:
* inner product space;
* normed ring;
* normed space over `ℝ`.
We show that the norm on `ℍ[ℝ]` agrees with the euclidean norm of its components.
## Notation
The following notation is available with `open Quaternion` or `open scoped Quaternion`:
* `ℍ` : quaternions
## Tags
quaternion, normed ring, normed space, normed algebra
-/
@[inherit_doc] scoped[Quaternion] notation "ℍ" => Quaternion ℝ
open scoped RealInnerProductSpace
namespace Quaternion
instance : Inner ℝ ℍ :=
⟨fun a b => (a * star b).re⟩
theorem inner_self (a : ℍ) : ⟪a, a⟫ = normSq a :=
rfl
#align quaternion.inner_self Quaternion.inner_self
theorem inner_def (a b : ℍ) : ⟪a, b⟫ = (a * star b).re :=
rfl
#align quaternion.inner_def Quaternion.inner_def
noncomputable instance : NormedAddCommGroup ℍ :=
@InnerProductSpace.Core.toNormedAddCommGroup ℝ ℍ _ _ _
{ toInner := inferInstance
conj_symm := fun x y => by simp [inner_def, mul_comm]
nonneg_re := fun x => normSq_nonneg
definite := fun x => normSq_eq_zero.1
add_left := fun x y z => by simp only [inner_def, add_mul, add_re]
smul_left := fun x y r => by simp [inner_def] }
noncomputable instance : InnerProductSpace ℝ ℍ :=
InnerProductSpace.ofCore _
theorem normSq_eq_norm_mul_self (a : ℍ) : normSq a = ‖a‖ * ‖a‖ := by
rw [← inner_self, real_inner_self_eq_norm_mul_norm]
#align quaternion.norm_sq_eq_norm_sq Quaternion.normSq_eq_norm_mul_self
instance : NormOneClass ℍ :=
⟨by rw [norm_eq_sqrt_real_inner, inner_self, normSq.map_one, Real.sqrt_one]⟩
@[simp, norm_cast]
theorem norm_coe (a : ℝ) : ‖(a : ℍ)‖ = ‖a‖ := by
rw [norm_eq_sqrt_real_inner, inner_self, normSq_coe, Real.sqrt_sq_eq_abs, Real.norm_eq_abs]
#align quaternion.norm_coe Quaternion.norm_coe
@[simp, norm_cast]
theorem nnnorm_coe (a : ℝ) : ‖(a : ℍ)‖₊ = ‖a‖₊ :=
Subtype.ext <| norm_coe a
#align quaternion.nnnorm_coe Quaternion.nnnorm_coe
@[simp, nolint simpNF] -- Porting note (#10959): simp cannot prove this
theorem norm_star (a : ℍ) : ‖star a‖ = ‖a‖ := by
simp_rw [norm_eq_sqrt_real_inner, inner_self, normSq_star]
#align quaternion.norm_star Quaternion.norm_star
@[simp, nolint simpNF] -- Porting note (#10959): simp cannot prove this
theorem nnnorm_star (a : ℍ) : ‖star a‖₊ = ‖a‖₊ :=
Subtype.ext <| norm_star a
#align quaternion.nnnorm_star Quaternion.nnnorm_star
noncomputable instance : NormedDivisionRing ℍ where
dist_eq _ _ := rfl
norm_mul' a b := by
simp only [norm_eq_sqrt_real_inner, inner_self, normSq.map_mul]
exact Real.sqrt_mul normSq_nonneg _
-- Porting note: added `noncomputable`
noncomputable instance : NormedAlgebra ℝ ℍ where
norm_smul_le := norm_smul_le
toAlgebra := Quaternion.algebra
instance : CstarRing ℍ where
norm_star_mul_self {x} := (norm_mul _ _).trans <| congr_arg (· * ‖x‖) (norm_star x)
/-- Coercion from `ℂ` to `ℍ`. -/
@[coe] def coeComplex (z : ℂ) : ℍ := ⟨z.re, z.im, 0, 0⟩
instance : Coe ℂ ℍ := ⟨coeComplex⟩
@[simp, norm_cast]
theorem coeComplex_re (z : ℂ) : (z : ℍ).re = z.re :=
rfl
#align quaternion.coe_complex_re Quaternion.coeComplex_re
@[simp, norm_cast]
theorem coeComplex_imI (z : ℂ) : (z : ℍ).imI = z.im :=
rfl
#align quaternion.coe_complex_im_i Quaternion.coeComplex_imI
@[simp, norm_cast]
theorem coeComplex_imJ (z : ℂ) : (z : ℍ).imJ = 0 :=
rfl
#align quaternion.coe_complex_im_j Quaternion.coeComplex_imJ
@[simp, norm_cast]
theorem coeComplex_imK (z : ℂ) : (z : ℍ).imK = 0 :=
rfl
#align quaternion.coe_complex_im_k Quaternion.coeComplex_imK
@[simp, norm_cast]
theorem coeComplex_add (z w : ℂ) : ↑(z + w) = (z + w : ℍ) := by ext <;> simp
#align quaternion.coe_complex_add Quaternion.coeComplex_add
@[simp, norm_cast]
theorem coeComplex_mul (z w : ℂ) : ↑(z * w) = (z * w : ℍ) := by ext <;> simp
#align quaternion.coe_complex_mul Quaternion.coeComplex_mul
@[simp, norm_cast]
theorem coeComplex_zero : ((0 : ℂ) : ℍ) = 0 :=
rfl
#align quaternion.coe_complex_zero Quaternion.coeComplex_zero
@[simp, norm_cast]
theorem coeComplex_one : ((1 : ℂ) : ℍ) = 1 :=
rfl
#align quaternion.coe_complex_one Quaternion.coeComplex_one
@[simp, norm_cast, nolint simpNF] -- Porting note (#10959): simp cannot prove this
| Mathlib/Analysis/Quaternion.lean | 150 | 150 | theorem coe_real_complex_mul (r : ℝ) (z : ℂ) : (r • z : ℍ) = ↑r * ↑z := by | ext <;> simp
|
/-
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
| Mathlib/Algebra/Polynomial/HasseDeriv.lean | 100 | 102 | 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]
|
/-
Copyright (c) 2020 Scott Morrison. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johan Commelin, Scott Morrison
-/
import Mathlib.Analysis.Convex.Combination
import Mathlib.LinearAlgebra.AffineSpace.Independent
import Mathlib.Tactic.FieldSimp
#align_import analysis.convex.caratheodory from "leanprover-community/mathlib"@"e6fab1dc073396d45da082c644642c4f8bff2264"
/-!
# Carathéodory's convexity theorem
Convex hull can be regarded as a refinement of affine span. Both are closure operators but whereas
convex hull takes values in the lattice of convex subsets, affine span takes values in the much
coarser sublattice of affine subspaces.
The cost of this refinement is that one no longer has bases. However Carathéodory's convexity
theorem offers some compensation. Given a set `s` together with a point `x` in its convex hull,
Carathéodory says that one may find an affine-independent family of elements `s` whose convex hull
contains `x`. Thus the difference from the case of affine span is that the affine-independent family
depends on `x`.
In particular, in finite dimensions Carathéodory's theorem implies that the convex hull of a set `s`
in `𝕜ᵈ` is the union of the convex hulls of the `(d + 1)`-tuples in `s`.
## Main results
* `convexHull_eq_union`: Carathéodory's convexity theorem
## Implementation details
This theorem was formalized as part of the Sphere Eversion project.
## Tags
convex hull, caratheodory
-/
open Set Finset
universe u
variable {𝕜 : Type*} {E : Type u} [LinearOrderedField 𝕜] [AddCommGroup E] [Module 𝕜 E]
namespace Caratheodory
/-- If `x` is in the convex hull of some finset `t` whose elements are not affine-independent,
then it is in the convex hull of a strict subset of `t`. -/
| Mathlib/Analysis/Convex/Caratheodory.lean | 52 | 98 | theorem mem_convexHull_erase [DecidableEq E] {t : Finset E} (h : ¬AffineIndependent 𝕜 ((↑) : t → E))
{x : E} (m : x ∈ convexHull 𝕜 (↑t : Set E)) :
∃ y : (↑t : Set E), x ∈ convexHull 𝕜 (↑(t.erase y) : Set E) := by |
simp only [Finset.convexHull_eq, mem_setOf_eq] at m ⊢
obtain ⟨f, fpos, fsum, rfl⟩ := m
obtain ⟨g, gcombo, gsum, gpos⟩ := exists_nontrivial_relation_sum_zero_of_not_affine_ind h
replace gpos := exists_pos_of_sum_zero_of_exists_nonzero g gsum gpos
clear h
let s := @Finset.filter _ (fun z => 0 < g z) (fun _ => LinearOrder.decidableLT _ _) t
obtain ⟨i₀, mem, w⟩ : ∃ i₀ ∈ s, ∀ i ∈ s, f i₀ / g i₀ ≤ f i / g i := by
apply s.exists_min_image fun z => f z / g z
obtain ⟨x, hx, hgx⟩ : ∃ x ∈ t, 0 < g x := gpos
exact ⟨x, mem_filter.mpr ⟨hx, hgx⟩⟩
have hg : 0 < g i₀ := by
rw [mem_filter] at mem
exact mem.2
have hi₀ : i₀ ∈ t := filter_subset _ _ mem
let k : E → 𝕜 := fun z => f z - f i₀ / g i₀ * g z
have hk : k i₀ = 0 := by field_simp [k, ne_of_gt hg]
have ksum : ∑ e ∈ t.erase i₀, k e = 1 := by
calc
∑ e ∈ t.erase i₀, k e = ∑ e ∈ t, k e := by
conv_rhs => rw [← insert_erase hi₀, sum_insert (not_mem_erase i₀ t), hk, zero_add]
_ = ∑ e ∈ t, (f e - f i₀ / g i₀ * g e) := rfl
_ = 1 := by rw [sum_sub_distrib, fsum, ← mul_sum, gsum, mul_zero, sub_zero]
refine ⟨⟨i₀, hi₀⟩, k, ?_, by convert ksum, ?_⟩
· simp only [k, and_imp, sub_nonneg, mem_erase, Ne, Subtype.coe_mk]
intro e _ het
by_cases hes : e ∈ s
· have hge : 0 < g e := by
rw [mem_filter] at hes
exact hes.2
rw [← le_div_iff hge]
exact w _ hes
· calc
_ ≤ 0 := by
apply mul_nonpos_of_nonneg_of_nonpos
· apply div_nonneg (fpos i₀ (mem_of_subset (filter_subset _ t) mem)) (le_of_lt hg)
· simpa only [s, mem_filter, het, true_and_iff, not_lt] using hes
_ ≤ f e := fpos e het
· rw [Subtype.coe_mk, centerMass_eq_of_sum_1 _ id ksum]
calc
∑ e ∈ t.erase i₀, k e • e = ∑ e ∈ t, k e • e := sum_erase _ (by rw [hk, zero_smul])
_ = ∑ e ∈ t, (f e - f i₀ / g i₀ * g e) • e := rfl
_ = t.centerMass f id := by
simp only [sub_smul, mul_smul, sum_sub_distrib, ← smul_sum, gcombo, smul_zero, sub_zero,
centerMass, fsum, inv_one, one_smul, id]
|
/-
Copyright (c) 2022 Joël Riou. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Joël Riou
-/
import Mathlib.AlgebraicTopology.DoldKan.Projections
import Mathlib.CategoryTheory.Idempotents.FunctorCategories
import Mathlib.CategoryTheory.Idempotents.FunctorExtension
#align_import algebraic_topology.dold_kan.p_infty from "leanprover-community/mathlib"@"32a7e535287f9c73f2e4d2aef306a39190f0b504"
/-!
# Construction of the projection `PInfty` for the Dold-Kan correspondence
In this file, we construct the projection `PInfty : K[X] ⟶ K[X]` by passing
to the limit the projections `P q` defined in `Projections.lean`. This
projection is a critical tool in this formalisation of the Dold-Kan correspondence,
because in the case of abelian categories, `PInfty` corresponds to the
projection on the normalized Moore subcomplex, with kernel the degenerate subcomplex.
(See `Equivalence.lean` for the general strategy of proof of the Dold-Kan equivalence.)
-/
open CategoryTheory CategoryTheory.Category CategoryTheory.Preadditive
CategoryTheory.SimplicialObject CategoryTheory.Idempotents Opposite Simplicial DoldKan
namespace AlgebraicTopology
namespace DoldKan
variable {C : Type*} [Category C] [Preadditive C] {X : SimplicialObject C}
theorem P_is_eventually_constant {q n : ℕ} (hqn : n ≤ q) :
((P (q + 1)).f n : X _[n] ⟶ _) = (P q).f n := by
rcases n with (_|n)
· simp only [Nat.zero_eq, P_f_0_eq]
· simp only [P_succ, add_right_eq_self, comp_add, HomologicalComplex.comp_f,
HomologicalComplex.add_f_apply, comp_id]
exact (HigherFacesVanish.of_P q n).comp_Hσ_eq_zero (Nat.succ_le_iff.mp hqn)
set_option linter.uppercaseLean3 false in
#align algebraic_topology.dold_kan.P_is_eventually_constant AlgebraicTopology.DoldKan.P_is_eventually_constant
theorem Q_is_eventually_constant {q n : ℕ} (hqn : n ≤ q) :
((Q (q + 1)).f n : X _[n] ⟶ _) = (Q q).f n := by
simp only [Q, HomologicalComplex.sub_f_apply, P_is_eventually_constant hqn]
set_option linter.uppercaseLean3 false in
#align algebraic_topology.dold_kan.Q_is_eventually_constant AlgebraicTopology.DoldKan.Q_is_eventually_constant
/-- The endomorphism `PInfty : K[X] ⟶ K[X]` obtained from the `P q` by passing to the limit. -/
noncomputable def PInfty : K[X] ⟶ K[X] :=
ChainComplex.ofHom _ _ _ _ _ _ (fun n => ((P n).f n : X _[n] ⟶ _)) fun n => by
simpa only [← P_is_eventually_constant (show n ≤ n by rfl),
AlternatingFaceMapComplex.obj_d_eq] using (P (n + 1) : K[X] ⟶ _).comm (n + 1) n
set_option linter.uppercaseLean3 false in
#align algebraic_topology.dold_kan.P_infty AlgebraicTopology.DoldKan.PInfty
/-- The endomorphism `QInfty : K[X] ⟶ K[X]` obtained from the `Q q` by passing to the limit. -/
noncomputable def QInfty : K[X] ⟶ K[X] :=
𝟙 _ - PInfty
set_option linter.uppercaseLean3 false in
#align algebraic_topology.dold_kan.Q_infty AlgebraicTopology.DoldKan.QInfty
@[simp]
theorem PInfty_f_0 : (PInfty.f 0 : X _[0] ⟶ X _[0]) = 𝟙 _ :=
rfl
set_option linter.uppercaseLean3 false in
#align algebraic_topology.dold_kan.P_infty_f_0 AlgebraicTopology.DoldKan.PInfty_f_0
theorem PInfty_f (n : ℕ) : (PInfty.f n : X _[n] ⟶ X _[n]) = (P n).f n :=
rfl
set_option linter.uppercaseLean3 false in
#align algebraic_topology.dold_kan.P_infty_f AlgebraicTopology.DoldKan.PInfty_f
@[simp]
theorem QInfty_f_0 : (QInfty.f 0 : X _[0] ⟶ X _[0]) = 0 := by
dsimp [QInfty]
simp only [sub_self]
set_option linter.uppercaseLean3 false in
#align algebraic_topology.dold_kan.Q_infty_f_0 AlgebraicTopology.DoldKan.QInfty_f_0
theorem QInfty_f (n : ℕ) : (QInfty.f n : X _[n] ⟶ X _[n]) = (Q n).f n :=
rfl
set_option linter.uppercaseLean3 false in
#align algebraic_topology.dold_kan.Q_infty_f AlgebraicTopology.DoldKan.QInfty_f
@[reassoc (attr := simp)]
theorem PInfty_f_naturality (n : ℕ) {X Y : SimplicialObject C} (f : X ⟶ Y) :
f.app (op [n]) ≫ PInfty.f n = PInfty.f n ≫ f.app (op [n]) :=
P_f_naturality n n f
set_option linter.uppercaseLean3 false in
#align algebraic_topology.dold_kan.P_infty_f_naturality AlgebraicTopology.DoldKan.PInfty_f_naturality
@[reassoc (attr := simp)]
theorem QInfty_f_naturality (n : ℕ) {X Y : SimplicialObject C} (f : X ⟶ Y) :
f.app (op [n]) ≫ QInfty.f n = QInfty.f n ≫ f.app (op [n]) :=
Q_f_naturality n n f
set_option linter.uppercaseLean3 false in
#align algebraic_topology.dold_kan.Q_infty_f_naturality AlgebraicTopology.DoldKan.QInfty_f_naturality
@[reassoc (attr := simp)]
theorem PInfty_f_idem (n : ℕ) : (PInfty.f n : X _[n] ⟶ _) ≫ PInfty.f n = PInfty.f n := by
simp only [PInfty_f, P_f_idem]
set_option linter.uppercaseLean3 false in
#align algebraic_topology.dold_kan.P_infty_f_idem AlgebraicTopology.DoldKan.PInfty_f_idem
@[reassoc (attr := simp)]
| Mathlib/AlgebraicTopology/DoldKan/PInfty.lean | 110 | 112 | theorem PInfty_idem : (PInfty : K[X] ⟶ _) ≫ PInfty = PInfty := by |
ext n
exact PInfty_f_idem n
|
/-
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.Data.Finset.Lattice
import Mathlib.Data.Multiset.Powerset
#align_import data.finset.powerset from "leanprover-community/mathlib"@"9003f28797c0664a49e4179487267c494477d853"
/-!
# The powerset of a finset
-/
namespace Finset
open Function Multiset
variable {α : Type*} {s t : Finset α}
/-! ### powerset -/
section Powerset
/-- When `s` is a finset, `s.powerset` is the finset of all subsets of `s` (seen as finsets). -/
def powerset (s : Finset α) : Finset (Finset α) :=
⟨(s.1.powerset.pmap Finset.mk) fun _t h => nodup_of_le (mem_powerset.1 h) s.nodup,
s.nodup.powerset.pmap fun _a _ha _b _hb => congr_arg Finset.val⟩
#align finset.powerset Finset.powerset
@[simp]
theorem mem_powerset {s t : Finset α} : s ∈ powerset t ↔ s ⊆ t := by
cases s
simp [powerset, mem_mk, mem_pmap, mk.injEq, mem_powerset, exists_prop, exists_eq_right,
← val_le_iff]
#align finset.mem_powerset Finset.mem_powerset
@[simp, norm_cast]
| Mathlib/Data/Finset/Powerset.lean | 41 | 44 | theorem coe_powerset (s : Finset α) :
(s.powerset : Set (Finset α)) = ((↑) : Finset α → Set α) ⁻¹' (s : Set α).powerset := by |
ext
simp
|
/-
Copyright (c) 2021 Eric Wieser. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Eric Wieser
-/
import Mathlib.Algebra.DualNumber
import Mathlib.Algebra.QuaternionBasis
import Mathlib.Data.Complex.Module
import Mathlib.LinearAlgebra.CliffordAlgebra.Conjugation
import Mathlib.LinearAlgebra.CliffordAlgebra.Star
import Mathlib.LinearAlgebra.QuadraticForm.Prod
#align_import linear_algebra.clifford_algebra.equivs from "leanprover-community/mathlib"@"cf7a7252c1989efe5800e0b3cdfeb4228ac6b40e"
/-!
# Other constructions isomorphic to Clifford Algebras
This file contains isomorphisms showing that other types are equivalent to some `CliffordAlgebra`.
## Rings
* `CliffordAlgebraRing.equiv`: any ring is equivalent to a `CliffordAlgebra` over a
zero-dimensional vector space.
## Complex numbers
* `CliffordAlgebraComplex.equiv`: the `Complex` numbers are equivalent as an `ℝ`-algebra to a
`CliffordAlgebra` over a one-dimensional vector space with a quadratic form that satisfies
`Q (ι Q 1) = -1`.
* `CliffordAlgebraComplex.toComplex`: the forward direction of this equiv
* `CliffordAlgebraComplex.ofComplex`: the reverse direction of this equiv
We show additionally that this equivalence sends `Complex.conj` to `CliffordAlgebra.involute` and
vice-versa:
* `CliffordAlgebraComplex.toComplex_involute`
* `CliffordAlgebraComplex.ofComplex_conj`
Note that in this algebra `CliffordAlgebra.reverse` is the identity and so the clifford conjugate
is the same as `CliffordAlgebra.involute`.
## Quaternion algebras
* `CliffordAlgebraQuaternion.equiv`: a `QuaternionAlgebra` over `R` is equivalent as an
`R`-algebra to a clifford algebra over `R × R`, sending `i` to `(0, 1)` and `j` to `(1, 0)`.
* `CliffordAlgebraQuaternion.toQuaternion`: the forward direction of this equiv
* `CliffordAlgebraQuaternion.ofQuaternion`: the reverse direction of this equiv
We show additionally that this equivalence sends `QuaternionAlgebra.conj` to the clifford conjugate
and vice-versa:
* `CliffordAlgebraQuaternion.toQuaternion_star`
* `CliffordAlgebraQuaternion.ofQuaternion_star`
## Dual numbers
* `CliffordAlgebraDualNumber.equiv`: `R[ε]` is equivalent as an `R`-algebra to a clifford
algebra over `R` where `Q = 0`.
-/
open CliffordAlgebra
/-! ### The clifford algebra isomorphic to a ring -/
namespace CliffordAlgebraRing
open scoped ComplexConjugate
variable {R : Type*} [CommRing R]
@[simp]
theorem ι_eq_zero : ι (0 : QuadraticForm R Unit) = 0 :=
Subsingleton.elim _ _
#align clifford_algebra_ring.ι_eq_zero CliffordAlgebraRing.ι_eq_zero
/-- Since the vector space is empty the ring is commutative. -/
instance : CommRing (CliffordAlgebra (0 : QuadraticForm R Unit)) :=
{ CliffordAlgebra.instRing _ with
mul_comm := fun x y => by
induction x using CliffordAlgebra.induction with
| algebraMap r => apply Algebra.commutes
| ι x => simp
| add x₁ x₂ hx₁ hx₂ => rw [mul_add, add_mul, hx₁, hx₂]
| mul x₁ x₂ hx₁ hx₂ => rw [mul_assoc, hx₂, ← mul_assoc, hx₁, ← mul_assoc] }
-- Porting note: Changed `x.reverse` to `reverse (R := R) x`
| Mathlib/LinearAlgebra/CliffordAlgebra/Equivs.lean | 90 | 96 | theorem reverse_apply (x : CliffordAlgebra (0 : QuadraticForm R Unit)) :
reverse (R := R) x = x := by |
induction x using CliffordAlgebra.induction with
| algebraMap r => exact reverse.commutes _
| ι x => rw [ι_eq_zero, LinearMap.zero_apply, reverse.map_zero]
| mul x₁ x₂ hx₁ hx₂ => rw [reverse.map_mul, mul_comm, hx₁, hx₂]
| add x₁ x₂ hx₁ hx₂ => rw [reverse.map_add, hx₁, hx₂]
|
/-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Michael Stoll
-/
import Mathlib.NumberTheory.LegendreSymbol.QuadraticChar.Basic
#align_import number_theory.legendre_symbol.basic from "leanprover-community/mathlib"@"5b2fe80501ff327b9109fb09b7cc8c325cd0d7d9"
/-!
# Legendre symbol
This file contains results about Legendre symbols.
We define the Legendre symbol $\Bigl(\frac{a}{p}\Bigr)$ as `legendreSym p a`.
Note the order of arguments! The advantage of this form is that then `legendreSym p`
is a multiplicative map.
The Legendre symbol is used to define the Jacobi symbol, `jacobiSym a b`, for integers `a`
and (odd) natural numbers `b`, which extends the Legendre symbol.
## Main results
We also prove the supplementary laws that give conditions for when `-1`
is a square modulo a prime `p`:
`legendreSym.at_neg_one` and `ZMod.exists_sq_eq_neg_one_iff` for `-1`.
See `NumberTheory.LegendreSymbol.QuadraticReciprocity` for the conditions when `2` and `-2`
are squares:
`legendreSym.at_two` and `ZMod.exists_sq_eq_two_iff` for `2`,
`legendreSym.at_neg_two` and `ZMod.exists_sq_eq_neg_two_iff` for `-2`.
## Tags
quadratic residue, quadratic nonresidue, Legendre symbol
-/
open Nat
section Euler
namespace ZMod
variable (p : ℕ) [Fact p.Prime]
/-- Euler's Criterion: A unit `x` of `ZMod p` is a square if and only if `x ^ (p / 2) = 1`. -/
theorem euler_criterion_units (x : (ZMod p)ˣ) : (∃ y : (ZMod p)ˣ, y ^ 2 = x) ↔ x ^ (p / 2) = 1 := by
by_cases hc : p = 2
· subst hc
simp only [eq_iff_true_of_subsingleton, exists_const]
· have h₀ := FiniteField.unit_isSquare_iff (by rwa [ringChar_zmod_n]) x
have hs : (∃ y : (ZMod p)ˣ, y ^ 2 = x) ↔ IsSquare x := by
rw [isSquare_iff_exists_sq x]
simp_rw [eq_comm]
rw [hs]
rwa [card p] at h₀
#align zmod.euler_criterion_units ZMod.euler_criterion_units
/-- Euler's Criterion: a nonzero `a : ZMod p` is a square if and only if `x ^ (p / 2) = 1`. -/
theorem euler_criterion {a : ZMod p} (ha : a ≠ 0) : IsSquare (a : ZMod p) ↔ a ^ (p / 2) = 1 := by
apply (iff_congr _ (by simp [Units.ext_iff])).mp (euler_criterion_units p (Units.mk0 a ha))
simp only [Units.ext_iff, sq, Units.val_mk0, Units.val_mul]
constructor
· rintro ⟨y, hy⟩; exact ⟨y, hy.symm⟩
· rintro ⟨y, rfl⟩
have hy : y ≠ 0 := by
rintro rfl
simp [zero_pow, mul_zero, ne_eq, not_true] at ha
refine ⟨Units.mk0 y hy, ?_⟩; simp
#align zmod.euler_criterion ZMod.euler_criterion
/-- If `a : ZMod p` is nonzero, then `a^(p/2)` is either `1` or `-1`. -/
| Mathlib/NumberTheory/LegendreSymbol/Basic.lean | 74 | 81 | theorem pow_div_two_eq_neg_one_or_one {a : ZMod p} (ha : a ≠ 0) :
a ^ (p / 2) = 1 ∨ a ^ (p / 2) = -1 := by |
cases' Prime.eq_two_or_odd (@Fact.out p.Prime _) with hp2 hp_odd
· subst p; revert a ha; intro a; fin_cases a
· tauto
· simp
rw [← mul_self_eq_one_iff, ← pow_add, ← two_mul, two_mul_odd_div_two hp_odd]
exact pow_card_sub_one_eq_one ha
|
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