Context stringlengths 57 6.04k | file_name stringlengths 21 79 | start int64 14 1.49k | end int64 18 1.5k | theorem stringlengths 25 1.55k | proof stringlengths 5 7.36k | rank int64 0 2.4k |
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import Mathlib.RingTheory.RootsOfUnity.Basic
import Mathlib.FieldTheory.Minpoly.IsIntegrallyClosed
import Mathlib.Algebra.GCDMonoid.IntegrallyClosed
import Mathlib.FieldTheory.Finite.Basic
#align_import ring_theory.roots_of_unity.minpoly from "leanprover-community/mathlib"@"7fdeecc0d03cd40f7a165e6cf00a4d2286db599f"
open minpoly Polynomial
open scoped Polynomial
namespace IsPrimitiveRoot
section CommRing
variable {n : ℕ} {K : Type*} [CommRing K] {μ : K} (h : IsPrimitiveRoot μ n)
-- Porting note: `hpos` was in the `variable` line, with an `omit` in mathlib3 just after this
-- declaration. For some reason, in Lean4, `hpos` gets included also in the declarations below,
-- even if it is not used in the proof.
theorem isIntegral (hpos : 0 < n) : IsIntegral ℤ μ := by
use X ^ n - 1
constructor
· exact monic_X_pow_sub_C 1 (ne_of_lt hpos).symm
· simp only [((IsPrimitiveRoot.iff_def μ n).mp h).left, eval₂_one, eval₂_X_pow, eval₂_sub,
sub_self]
#align is_primitive_root.is_integral IsPrimitiveRoot.isIntegral
section IsDomain
variable [IsDomain K] [CharZero K]
theorem minpoly_dvd_x_pow_sub_one : minpoly ℤ μ ∣ X ^ n - 1 := by
rcases n.eq_zero_or_pos with (rfl | h0)
· simp
apply minpoly.isIntegrallyClosed_dvd (isIntegral h h0)
simp only [((IsPrimitiveRoot.iff_def μ n).mp h).left, aeval_X_pow, eq_intCast, Int.cast_one,
aeval_one, AlgHom.map_sub, sub_self]
set_option linter.uppercaseLean3 false in
#align is_primitive_root.minpoly_dvd_X_pow_sub_one IsPrimitiveRoot.minpoly_dvd_x_pow_sub_one
theorem separable_minpoly_mod {p : ℕ} [Fact p.Prime] (hdiv : ¬p ∣ n) :
Separable (map (Int.castRingHom (ZMod p)) (minpoly ℤ μ)) := by
have hdvd : map (Int.castRingHom (ZMod p)) (minpoly ℤ μ) ∣ X ^ n - 1 := by
convert RingHom.map_dvd (mapRingHom (Int.castRingHom (ZMod p)))
(minpoly_dvd_x_pow_sub_one h)
simp only [map_sub, map_pow, coe_mapRingHom, map_X, map_one]
refine Separable.of_dvd (separable_X_pow_sub_C 1 ?_ one_ne_zero) hdvd
by_contra hzero
exact hdiv ((ZMod.natCast_zmod_eq_zero_iff_dvd n p).1 hzero)
#align is_primitive_root.separable_minpoly_mod IsPrimitiveRoot.separable_minpoly_mod
theorem squarefree_minpoly_mod {p : ℕ} [Fact p.Prime] (hdiv : ¬p ∣ n) :
Squarefree (map (Int.castRingHom (ZMod p)) (minpoly ℤ μ)) :=
(separable_minpoly_mod h hdiv).squarefree
#align is_primitive_root.squarefree_minpoly_mod IsPrimitiveRoot.squarefree_minpoly_mod
theorem minpoly_dvd_expand {p : ℕ} (hdiv : ¬p ∣ n) :
minpoly ℤ μ ∣ expand ℤ p (minpoly ℤ (μ ^ p)) := by
rcases n.eq_zero_or_pos with (rfl | hpos)
· simp_all
letI : IsIntegrallyClosed ℤ := GCDMonoid.toIsIntegrallyClosed
refine minpoly.isIntegrallyClosed_dvd (h.isIntegral hpos) ?_
rw [aeval_def, coe_expand, ← comp, eval₂_eq_eval_map, map_comp, Polynomial.map_pow, map_X,
eval_comp, eval_pow, eval_X, ← eval₂_eq_eval_map, ← aeval_def]
exact minpoly.aeval _ _
#align is_primitive_root.minpoly_dvd_expand IsPrimitiveRoot.minpoly_dvd_expand
| Mathlib/RingTheory/RootsOfUnity/Minpoly.lean | 95 | 104 | theorem minpoly_dvd_pow_mod {p : ℕ} [hprime : Fact p.Prime] (hdiv : ¬p ∣ n) :
map (Int.castRingHom (ZMod p)) (minpoly ℤ μ) ∣
map (Int.castRingHom (ZMod p)) (minpoly ℤ (μ ^ p)) ^ p := by |
set Q := minpoly ℤ (μ ^ p)
have hfrob :
map (Int.castRingHom (ZMod p)) Q ^ p = map (Int.castRingHom (ZMod p)) (expand ℤ p Q) := by
rw [← ZMod.expand_card, map_expand]
rw [hfrob]
apply RingHom.map_dvd (mapRingHom (Int.castRingHom (ZMod p)))
exact minpoly_dvd_expand h hdiv
| 2,025 |
import Mathlib.RingTheory.RootsOfUnity.Basic
import Mathlib.FieldTheory.Minpoly.IsIntegrallyClosed
import Mathlib.Algebra.GCDMonoid.IntegrallyClosed
import Mathlib.FieldTheory.Finite.Basic
#align_import ring_theory.roots_of_unity.minpoly from "leanprover-community/mathlib"@"7fdeecc0d03cd40f7a165e6cf00a4d2286db599f"
open minpoly Polynomial
open scoped Polynomial
namespace IsPrimitiveRoot
section CommRing
variable {n : ℕ} {K : Type*} [CommRing K] {μ : K} (h : IsPrimitiveRoot μ n)
-- Porting note: `hpos` was in the `variable` line, with an `omit` in mathlib3 just after this
-- declaration. For some reason, in Lean4, `hpos` gets included also in the declarations below,
-- even if it is not used in the proof.
theorem isIntegral (hpos : 0 < n) : IsIntegral ℤ μ := by
use X ^ n - 1
constructor
· exact monic_X_pow_sub_C 1 (ne_of_lt hpos).symm
· simp only [((IsPrimitiveRoot.iff_def μ n).mp h).left, eval₂_one, eval₂_X_pow, eval₂_sub,
sub_self]
#align is_primitive_root.is_integral IsPrimitiveRoot.isIntegral
section IsDomain
variable [IsDomain K] [CharZero K]
theorem minpoly_dvd_x_pow_sub_one : minpoly ℤ μ ∣ X ^ n - 1 := by
rcases n.eq_zero_or_pos with (rfl | h0)
· simp
apply minpoly.isIntegrallyClosed_dvd (isIntegral h h0)
simp only [((IsPrimitiveRoot.iff_def μ n).mp h).left, aeval_X_pow, eq_intCast, Int.cast_one,
aeval_one, AlgHom.map_sub, sub_self]
set_option linter.uppercaseLean3 false in
#align is_primitive_root.minpoly_dvd_X_pow_sub_one IsPrimitiveRoot.minpoly_dvd_x_pow_sub_one
theorem separable_minpoly_mod {p : ℕ} [Fact p.Prime] (hdiv : ¬p ∣ n) :
Separable (map (Int.castRingHom (ZMod p)) (minpoly ℤ μ)) := by
have hdvd : map (Int.castRingHom (ZMod p)) (minpoly ℤ μ) ∣ X ^ n - 1 := by
convert RingHom.map_dvd (mapRingHom (Int.castRingHom (ZMod p)))
(minpoly_dvd_x_pow_sub_one h)
simp only [map_sub, map_pow, coe_mapRingHom, map_X, map_one]
refine Separable.of_dvd (separable_X_pow_sub_C 1 ?_ one_ne_zero) hdvd
by_contra hzero
exact hdiv ((ZMod.natCast_zmod_eq_zero_iff_dvd n p).1 hzero)
#align is_primitive_root.separable_minpoly_mod IsPrimitiveRoot.separable_minpoly_mod
theorem squarefree_minpoly_mod {p : ℕ} [Fact p.Prime] (hdiv : ¬p ∣ n) :
Squarefree (map (Int.castRingHom (ZMod p)) (minpoly ℤ μ)) :=
(separable_minpoly_mod h hdiv).squarefree
#align is_primitive_root.squarefree_minpoly_mod IsPrimitiveRoot.squarefree_minpoly_mod
theorem minpoly_dvd_expand {p : ℕ} (hdiv : ¬p ∣ n) :
minpoly ℤ μ ∣ expand ℤ p (minpoly ℤ (μ ^ p)) := by
rcases n.eq_zero_or_pos with (rfl | hpos)
· simp_all
letI : IsIntegrallyClosed ℤ := GCDMonoid.toIsIntegrallyClosed
refine minpoly.isIntegrallyClosed_dvd (h.isIntegral hpos) ?_
rw [aeval_def, coe_expand, ← comp, eval₂_eq_eval_map, map_comp, Polynomial.map_pow, map_X,
eval_comp, eval_pow, eval_X, ← eval₂_eq_eval_map, ← aeval_def]
exact minpoly.aeval _ _
#align is_primitive_root.minpoly_dvd_expand IsPrimitiveRoot.minpoly_dvd_expand
theorem minpoly_dvd_pow_mod {p : ℕ} [hprime : Fact p.Prime] (hdiv : ¬p ∣ n) :
map (Int.castRingHom (ZMod p)) (minpoly ℤ μ) ∣
map (Int.castRingHom (ZMod p)) (minpoly ℤ (μ ^ p)) ^ p := by
set Q := minpoly ℤ (μ ^ p)
have hfrob :
map (Int.castRingHom (ZMod p)) Q ^ p = map (Int.castRingHom (ZMod p)) (expand ℤ p Q) := by
rw [← ZMod.expand_card, map_expand]
rw [hfrob]
apply RingHom.map_dvd (mapRingHom (Int.castRingHom (ZMod p)))
exact minpoly_dvd_expand h hdiv
#align is_primitive_root.minpoly_dvd_pow_mod IsPrimitiveRoot.minpoly_dvd_pow_mod
theorem minpoly_dvd_mod_p {p : ℕ} [Fact p.Prime] (hdiv : ¬p ∣ n) :
map (Int.castRingHom (ZMod p)) (minpoly ℤ μ) ∣
map (Int.castRingHom (ZMod p)) (minpoly ℤ (μ ^ p)) :=
(squarefree_minpoly_mod h hdiv).isRadical _ _ (minpoly_dvd_pow_mod h hdiv)
#align is_primitive_root.minpoly_dvd_mod_p IsPrimitiveRoot.minpoly_dvd_mod_p
| Mathlib/RingTheory/RootsOfUnity/Minpoly.lean | 118 | 169 | theorem minpoly_eq_pow {p : ℕ} [hprime : Fact p.Prime] (hdiv : ¬p ∣ n) :
minpoly ℤ μ = minpoly ℤ (μ ^ p) := by |
classical
by_cases hn : n = 0
· simp_all
have hpos := Nat.pos_of_ne_zero hn
by_contra hdiff
set P := minpoly ℤ μ
set Q := minpoly ℤ (μ ^ p)
have Pmonic : P.Monic := minpoly.monic (h.isIntegral hpos)
have Qmonic : Q.Monic := minpoly.monic ((h.pow_of_prime hprime.1 hdiv).isIntegral hpos)
have Pirr : Irreducible P := minpoly.irreducible (h.isIntegral hpos)
have Qirr : Irreducible Q := minpoly.irreducible ((h.pow_of_prime hprime.1 hdiv).isIntegral hpos)
have PQprim : IsPrimitive (P * Q) := Pmonic.isPrimitive.mul Qmonic.isPrimitive
have prod : P * Q ∣ X ^ n - 1 := by
rw [IsPrimitive.Int.dvd_iff_map_cast_dvd_map_cast (P * Q) (X ^ n - 1) PQprim
(monic_X_pow_sub_C (1 : ℤ) (ne_of_gt hpos)).isPrimitive,
Polynomial.map_mul]
refine IsCoprime.mul_dvd ?_ ?_ ?_
· have aux := IsPrimitive.Int.irreducible_iff_irreducible_map_cast Pmonic.isPrimitive
refine (dvd_or_coprime _ _ (aux.1 Pirr)).resolve_left ?_
rw [map_dvd_map (Int.castRingHom ℚ) Int.cast_injective Pmonic]
intro hdiv
refine hdiff (eq_of_monic_of_associated Pmonic Qmonic ?_)
exact associated_of_dvd_dvd hdiv (Pirr.dvd_symm Qirr hdiv)
· apply (map_dvd_map (Int.castRingHom ℚ) Int.cast_injective Pmonic).2
exact minpoly_dvd_x_pow_sub_one h
· apply (map_dvd_map (Int.castRingHom ℚ) Int.cast_injective Qmonic).2
exact minpoly_dvd_x_pow_sub_one (pow_of_prime h hprime.1 hdiv)
replace prod := RingHom.map_dvd (mapRingHom (Int.castRingHom (ZMod p))) prod
rw [coe_mapRingHom, Polynomial.map_mul, Polynomial.map_sub, Polynomial.map_one,
Polynomial.map_pow, map_X] at prod
obtain ⟨R, hR⟩ := minpoly_dvd_mod_p h hdiv
rw [hR, ← mul_assoc, ← Polynomial.map_mul, ← sq, Polynomial.map_pow] at prod
have habs : map (Int.castRingHom (ZMod p)) P ^ 2 ∣ map (Int.castRingHom (ZMod p)) P ^ 2 * R := by
use R
replace habs :=
lt_of_lt_of_le (PartENat.coe_lt_coe.2 one_lt_two)
(multiplicity.le_multiplicity_of_pow_dvd (dvd_trans habs prod))
have hfree : Squarefree (X ^ n - 1 : (ZMod p)[X]) :=
(separable_X_pow_sub_C 1 (fun h => hdiv <| (ZMod.natCast_zmod_eq_zero_iff_dvd n p).1 h)
one_ne_zero).squarefree
cases'
(multiplicity.squarefree_iff_multiplicity_le_one (X ^ n - 1)).1 hfree
(map (Int.castRingHom (ZMod p)) P) with
hle hunit
· rw [Nat.cast_one] at habs; exact hle.not_lt habs
· replace hunit := degree_eq_zero_of_isUnit hunit
rw [degree_map_eq_of_leadingCoeff_ne_zero (Int.castRingHom (ZMod p)) _] at hunit
· exact (minpoly.degree_pos (isIntegral h hpos)).ne' hunit
simp only [Pmonic, eq_intCast, Monic.leadingCoeff, Int.cast_one, Ne, not_false_iff,
one_ne_zero]
| 2,025 |
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.RingTheory.Localization.NumDen
import Mathlib.RingTheory.Polynomial.ScaleRoots
#align_import ring_theory.polynomial.rational_root from "leanprover-community/mathlib"@"62c0a4ef1441edb463095ea02a06e87f3dfe135c"
open scoped Polynomial
section ScaleRoots
variable {A K R S : Type*} [CommRing A] [Field K] [CommRing R] [CommRing S]
variable {M : Submonoid A} [Algebra A S] [IsLocalization M S] [Algebra A K] [IsFractionRing A K]
open Finsupp IsFractionRing IsLocalization Polynomial
| Mathlib/RingTheory/Polynomial/RationalRoot.lean | 39 | 44 | theorem scaleRoots_aeval_eq_zero_of_aeval_mk'_eq_zero {p : A[X]} {r : A} {s : M}
(hr : aeval (mk' S r s) p = 0) : aeval (algebraMap A S r) (scaleRoots p s) = 0 := by |
convert scaleRoots_eval₂_eq_zero (algebraMap A S) hr
-- Porting note: added
funext
rw [aeval_def, mk'_spec' _ r s]
| 2,026 |
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.RingTheory.Localization.NumDen
import Mathlib.RingTheory.Polynomial.ScaleRoots
#align_import ring_theory.polynomial.rational_root from "leanprover-community/mathlib"@"62c0a4ef1441edb463095ea02a06e87f3dfe135c"
open scoped Polynomial
section ScaleRoots
variable {A K R S : Type*} [CommRing A] [Field K] [CommRing R] [CommRing S]
variable {M : Submonoid A} [Algebra A S] [IsLocalization M S] [Algebra A K] [IsFractionRing A K]
open Finsupp IsFractionRing IsLocalization Polynomial
theorem scaleRoots_aeval_eq_zero_of_aeval_mk'_eq_zero {p : A[X]} {r : A} {s : M}
(hr : aeval (mk' S r s) p = 0) : aeval (algebraMap A S r) (scaleRoots p s) = 0 := by
convert scaleRoots_eval₂_eq_zero (algebraMap A S) hr
-- Porting note: added
funext
rw [aeval_def, mk'_spec' _ r s]
#align scale_roots_aeval_eq_zero_of_aeval_mk'_eq_zero scaleRoots_aeval_eq_zero_of_aeval_mk'_eq_zero
variable [IsDomain A]
| Mathlib/RingTheory/Polynomial/RationalRoot.lean | 49 | 54 | theorem num_isRoot_scaleRoots_of_aeval_eq_zero [UniqueFactorizationMonoid A] {p : A[X]} {x : K}
(hr : aeval x p = 0) : IsRoot (scaleRoots p (den A x)) (num A x) := by |
apply isRoot_of_eval₂_map_eq_zero (IsFractionRing.injective A K)
refine scaleRoots_aeval_eq_zero_of_aeval_mk'_eq_zero ?_
rw [mk'_num_den]
exact hr
| 2,026 |
import Mathlib.FieldTheory.Normal
import Mathlib.FieldTheory.Perfect
import Mathlib.RingTheory.Localization.Integral
#align_import field_theory.is_alg_closed.basic from "leanprover-community/mathlib"@"00f91228655eecdcd3ac97a7fd8dbcb139fe990a"
universe u v w
open scoped Classical Polynomial
open Polynomial
variable (k : Type u) [Field k]
class IsAlgClosed : Prop where
splits : ∀ p : k[X], p.Splits <| RingHom.id k
#align is_alg_closed IsAlgClosed
| Mathlib/FieldTheory/IsAlgClosed/Basic.lean | 68 | 69 | theorem IsAlgClosed.splits_codomain {k K : Type*} [Field k] [IsAlgClosed k] [Field K] {f : K →+* k}
(p : K[X]) : p.Splits f := by | convert IsAlgClosed.splits (p.map f); simp [splits_map_iff]
| 2,027 |
import Mathlib.FieldTheory.Normal
import Mathlib.FieldTheory.Perfect
import Mathlib.RingTheory.Localization.Integral
#align_import field_theory.is_alg_closed.basic from "leanprover-community/mathlib"@"00f91228655eecdcd3ac97a7fd8dbcb139fe990a"
universe u v w
open scoped Classical Polynomial
open Polynomial
variable (k : Type u) [Field k]
class IsAlgClosed : Prop where
splits : ∀ p : k[X], p.Splits <| RingHom.id k
#align is_alg_closed IsAlgClosed
theorem IsAlgClosed.splits_codomain {k K : Type*} [Field k] [IsAlgClosed k] [Field K] {f : K →+* k}
(p : K[X]) : p.Splits f := by convert IsAlgClosed.splits (p.map f); simp [splits_map_iff]
#align is_alg_closed.splits_codomain IsAlgClosed.splits_codomain
theorem IsAlgClosed.splits_domain {k K : Type*} [Field k] [IsAlgClosed k] [Field K] {f : k →+* K}
(p : k[X]) : p.Splits f :=
Polynomial.splits_of_splits_id _ <| IsAlgClosed.splits _
#align is_alg_closed.splits_domain IsAlgClosed.splits_domain
namespace IsAlgClosed
variable {k}
theorem exists_root [IsAlgClosed k] (p : k[X]) (hp : p.degree ≠ 0) : ∃ x, IsRoot p x :=
exists_root_of_splits _ (IsAlgClosed.splits p) hp
#align is_alg_closed.exists_root IsAlgClosed.exists_root
| Mathlib/FieldTheory/IsAlgClosed/Basic.lean | 89 | 96 | theorem exists_pow_nat_eq [IsAlgClosed k] (x : k) {n : ℕ} (hn : 0 < n) : ∃ z, z ^ n = x := by |
have : degree (X ^ n - C x) ≠ 0 := by
rw [degree_X_pow_sub_C hn x]
exact ne_of_gt (WithBot.coe_lt_coe.2 hn)
obtain ⟨z, hz⟩ := exists_root (X ^ n - C x) this
use z
simp only [eval_C, eval_X, eval_pow, eval_sub, IsRoot.def] at hz
exact sub_eq_zero.1 hz
| 2,027 |
import Mathlib.FieldTheory.Normal
import Mathlib.FieldTheory.Perfect
import Mathlib.RingTheory.Localization.Integral
#align_import field_theory.is_alg_closed.basic from "leanprover-community/mathlib"@"00f91228655eecdcd3ac97a7fd8dbcb139fe990a"
universe u v w
open scoped Classical Polynomial
open Polynomial
variable (k : Type u) [Field k]
class IsAlgClosed : Prop where
splits : ∀ p : k[X], p.Splits <| RingHom.id k
#align is_alg_closed IsAlgClosed
theorem IsAlgClosed.splits_codomain {k K : Type*} [Field k] [IsAlgClosed k] [Field K] {f : K →+* k}
(p : K[X]) : p.Splits f := by convert IsAlgClosed.splits (p.map f); simp [splits_map_iff]
#align is_alg_closed.splits_codomain IsAlgClosed.splits_codomain
theorem IsAlgClosed.splits_domain {k K : Type*} [Field k] [IsAlgClosed k] [Field K] {f : k →+* K}
(p : k[X]) : p.Splits f :=
Polynomial.splits_of_splits_id _ <| IsAlgClosed.splits _
#align is_alg_closed.splits_domain IsAlgClosed.splits_domain
namespace IsAlgClosed
variable {k}
theorem exists_root [IsAlgClosed k] (p : k[X]) (hp : p.degree ≠ 0) : ∃ x, IsRoot p x :=
exists_root_of_splits _ (IsAlgClosed.splits p) hp
#align is_alg_closed.exists_root IsAlgClosed.exists_root
theorem exists_pow_nat_eq [IsAlgClosed k] (x : k) {n : ℕ} (hn : 0 < n) : ∃ z, z ^ n = x := by
have : degree (X ^ n - C x) ≠ 0 := by
rw [degree_X_pow_sub_C hn x]
exact ne_of_gt (WithBot.coe_lt_coe.2 hn)
obtain ⟨z, hz⟩ := exists_root (X ^ n - C x) this
use z
simp only [eval_C, eval_X, eval_pow, eval_sub, IsRoot.def] at hz
exact sub_eq_zero.1 hz
#align is_alg_closed.exists_pow_nat_eq IsAlgClosed.exists_pow_nat_eq
| Mathlib/FieldTheory/IsAlgClosed/Basic.lean | 99 | 101 | theorem exists_eq_mul_self [IsAlgClosed k] (x : k) : ∃ z, x = z * z := by |
rcases exists_pow_nat_eq x zero_lt_two with ⟨z, rfl⟩
exact ⟨z, sq z⟩
| 2,027 |
import Mathlib.FieldTheory.Normal
import Mathlib.FieldTheory.Perfect
import Mathlib.RingTheory.Localization.Integral
#align_import field_theory.is_alg_closed.basic from "leanprover-community/mathlib"@"00f91228655eecdcd3ac97a7fd8dbcb139fe990a"
universe u v w
open scoped Classical Polynomial
open Polynomial
variable (k : Type u) [Field k]
class IsAlgClosed : Prop where
splits : ∀ p : k[X], p.Splits <| RingHom.id k
#align is_alg_closed IsAlgClosed
theorem IsAlgClosed.splits_codomain {k K : Type*} [Field k] [IsAlgClosed k] [Field K] {f : K →+* k}
(p : K[X]) : p.Splits f := by convert IsAlgClosed.splits (p.map f); simp [splits_map_iff]
#align is_alg_closed.splits_codomain IsAlgClosed.splits_codomain
theorem IsAlgClosed.splits_domain {k K : Type*} [Field k] [IsAlgClosed k] [Field K] {f : k →+* K}
(p : k[X]) : p.Splits f :=
Polynomial.splits_of_splits_id _ <| IsAlgClosed.splits _
#align is_alg_closed.splits_domain IsAlgClosed.splits_domain
namespace IsAlgClosed
variable {k}
theorem exists_root [IsAlgClosed k] (p : k[X]) (hp : p.degree ≠ 0) : ∃ x, IsRoot p x :=
exists_root_of_splits _ (IsAlgClosed.splits p) hp
#align is_alg_closed.exists_root IsAlgClosed.exists_root
theorem exists_pow_nat_eq [IsAlgClosed k] (x : k) {n : ℕ} (hn : 0 < n) : ∃ z, z ^ n = x := by
have : degree (X ^ n - C x) ≠ 0 := by
rw [degree_X_pow_sub_C hn x]
exact ne_of_gt (WithBot.coe_lt_coe.2 hn)
obtain ⟨z, hz⟩ := exists_root (X ^ n - C x) this
use z
simp only [eval_C, eval_X, eval_pow, eval_sub, IsRoot.def] at hz
exact sub_eq_zero.1 hz
#align is_alg_closed.exists_pow_nat_eq IsAlgClosed.exists_pow_nat_eq
theorem exists_eq_mul_self [IsAlgClosed k] (x : k) : ∃ z, x = z * z := by
rcases exists_pow_nat_eq x zero_lt_two with ⟨z, rfl⟩
exact ⟨z, sq z⟩
#align is_alg_closed.exists_eq_mul_self IsAlgClosed.exists_eq_mul_self
| Mathlib/FieldTheory/IsAlgClosed/Basic.lean | 104 | 111 | theorem roots_eq_zero_iff [IsAlgClosed k] {p : k[X]} :
p.roots = 0 ↔ p = Polynomial.C (p.coeff 0) := by |
refine ⟨fun h => ?_, fun hp => by rw [hp, roots_C]⟩
rcases le_or_lt (degree p) 0 with hd | hd
· exact eq_C_of_degree_le_zero hd
· obtain ⟨z, hz⟩ := IsAlgClosed.exists_root p hd.ne'
rw [← mem_roots (ne_zero_of_degree_gt hd), h] at hz
simp at hz
| 2,027 |
import Mathlib.FieldTheory.Normal
import Mathlib.FieldTheory.Perfect
import Mathlib.RingTheory.Localization.Integral
#align_import field_theory.is_alg_closed.basic from "leanprover-community/mathlib"@"00f91228655eecdcd3ac97a7fd8dbcb139fe990a"
universe u v w
open scoped Classical Polynomial
open Polynomial
variable (k : Type u) [Field k]
class IsAlgClosed : Prop where
splits : ∀ p : k[X], p.Splits <| RingHom.id k
#align is_alg_closed IsAlgClosed
theorem IsAlgClosed.splits_codomain {k K : Type*} [Field k] [IsAlgClosed k] [Field K] {f : K →+* k}
(p : K[X]) : p.Splits f := by convert IsAlgClosed.splits (p.map f); simp [splits_map_iff]
#align is_alg_closed.splits_codomain IsAlgClosed.splits_codomain
theorem IsAlgClosed.splits_domain {k K : Type*} [Field k] [IsAlgClosed k] [Field K] {f : k →+* K}
(p : k[X]) : p.Splits f :=
Polynomial.splits_of_splits_id _ <| IsAlgClosed.splits _
#align is_alg_closed.splits_domain IsAlgClosed.splits_domain
namespace IsAlgClosed
variable {k}
theorem exists_root [IsAlgClosed k] (p : k[X]) (hp : p.degree ≠ 0) : ∃ x, IsRoot p x :=
exists_root_of_splits _ (IsAlgClosed.splits p) hp
#align is_alg_closed.exists_root IsAlgClosed.exists_root
theorem exists_pow_nat_eq [IsAlgClosed k] (x : k) {n : ℕ} (hn : 0 < n) : ∃ z, z ^ n = x := by
have : degree (X ^ n - C x) ≠ 0 := by
rw [degree_X_pow_sub_C hn x]
exact ne_of_gt (WithBot.coe_lt_coe.2 hn)
obtain ⟨z, hz⟩ := exists_root (X ^ n - C x) this
use z
simp only [eval_C, eval_X, eval_pow, eval_sub, IsRoot.def] at hz
exact sub_eq_zero.1 hz
#align is_alg_closed.exists_pow_nat_eq IsAlgClosed.exists_pow_nat_eq
theorem exists_eq_mul_self [IsAlgClosed k] (x : k) : ∃ z, x = z * z := by
rcases exists_pow_nat_eq x zero_lt_two with ⟨z, rfl⟩
exact ⟨z, sq z⟩
#align is_alg_closed.exists_eq_mul_self IsAlgClosed.exists_eq_mul_self
theorem roots_eq_zero_iff [IsAlgClosed k] {p : k[X]} :
p.roots = 0 ↔ p = Polynomial.C (p.coeff 0) := by
refine ⟨fun h => ?_, fun hp => by rw [hp, roots_C]⟩
rcases le_or_lt (degree p) 0 with hd | hd
· exact eq_C_of_degree_le_zero hd
· obtain ⟨z, hz⟩ := IsAlgClosed.exists_root p hd.ne'
rw [← mem_roots (ne_zero_of_degree_gt hd), h] at hz
simp at hz
#align is_alg_closed.roots_eq_zero_iff IsAlgClosed.roots_eq_zero_iff
theorem exists_eval₂_eq_zero_of_injective {R : Type*} [Ring R] [IsAlgClosed k] (f : R →+* k)
(hf : Function.Injective f) (p : R[X]) (hp : p.degree ≠ 0) : ∃ x, p.eval₂ f x = 0 :=
let ⟨x, hx⟩ := exists_root (p.map f) (by rwa [degree_map_eq_of_injective hf])
⟨x, by rwa [eval₂_eq_eval_map, ← IsRoot]⟩
#align is_alg_closed.exists_eval₂_eq_zero_of_injective IsAlgClosed.exists_eval₂_eq_zero_of_injective
theorem exists_eval₂_eq_zero {R : Type*} [Field R] [IsAlgClosed k] (f : R →+* k) (p : R[X])
(hp : p.degree ≠ 0) : ∃ x, p.eval₂ f x = 0 :=
exists_eval₂_eq_zero_of_injective f f.injective p hp
#align is_alg_closed.exists_eval₂_eq_zero IsAlgClosed.exists_eval₂_eq_zero
variable (k)
theorem exists_aeval_eq_zero_of_injective {R : Type*} [CommRing R] [IsAlgClosed k] [Algebra R k]
(hinj : Function.Injective (algebraMap R k)) (p : R[X]) (hp : p.degree ≠ 0) :
∃ x : k, aeval x p = 0 :=
exists_eval₂_eq_zero_of_injective (algebraMap R k) hinj p hp
#align is_alg_closed.exists_aeval_eq_zero_of_injective IsAlgClosed.exists_aeval_eq_zero_of_injective
theorem exists_aeval_eq_zero {R : Type*} [Field R] [IsAlgClosed k] [Algebra R k] (p : R[X])
(hp : p.degree ≠ 0) : ∃ x : k, aeval x p = 0 :=
exists_eval₂_eq_zero (algebraMap R k) p hp
#align is_alg_closed.exists_aeval_eq_zero IsAlgClosed.exists_aeval_eq_zero
| Mathlib/FieldTheory/IsAlgClosed/Basic.lean | 138 | 146 | theorem of_exists_root (H : ∀ p : k[X], p.Monic → Irreducible p → ∃ x, p.eval x = 0) :
IsAlgClosed k := by |
refine ⟨fun p ↦ Or.inr ?_⟩
intro q hq _
have : Irreducible (q * C (leadingCoeff q)⁻¹) := by
rw [← coe_normUnit_of_ne_zero hq.ne_zero]
exact (associated_normalize _).irreducible hq
obtain ⟨x, hx⟩ := H (q * C (leadingCoeff q)⁻¹) (monic_mul_leadingCoeff_inv hq.ne_zero) this
exact degree_mul_leadingCoeff_inv q hq.ne_zero ▸ degree_eq_one_of_irreducible_of_root this hx
| 2,027 |
import Mathlib.FieldTheory.Normal
import Mathlib.FieldTheory.Perfect
import Mathlib.RingTheory.Localization.Integral
#align_import field_theory.is_alg_closed.basic from "leanprover-community/mathlib"@"00f91228655eecdcd3ac97a7fd8dbcb139fe990a"
universe u v w
open scoped Classical Polynomial
open Polynomial
variable (k : Type u) [Field k]
class IsAlgClosed : Prop where
splits : ∀ p : k[X], p.Splits <| RingHom.id k
#align is_alg_closed IsAlgClosed
theorem IsAlgClosed.splits_codomain {k K : Type*} [Field k] [IsAlgClosed k] [Field K] {f : K →+* k}
(p : K[X]) : p.Splits f := by convert IsAlgClosed.splits (p.map f); simp [splits_map_iff]
#align is_alg_closed.splits_codomain IsAlgClosed.splits_codomain
theorem IsAlgClosed.splits_domain {k K : Type*} [Field k] [IsAlgClosed k] [Field K] {f : k →+* K}
(p : k[X]) : p.Splits f :=
Polynomial.splits_of_splits_id _ <| IsAlgClosed.splits _
#align is_alg_closed.splits_domain IsAlgClosed.splits_domain
namespace IsAlgClosed
variable {k}
theorem exists_root [IsAlgClosed k] (p : k[X]) (hp : p.degree ≠ 0) : ∃ x, IsRoot p x :=
exists_root_of_splits _ (IsAlgClosed.splits p) hp
#align is_alg_closed.exists_root IsAlgClosed.exists_root
theorem exists_pow_nat_eq [IsAlgClosed k] (x : k) {n : ℕ} (hn : 0 < n) : ∃ z, z ^ n = x := by
have : degree (X ^ n - C x) ≠ 0 := by
rw [degree_X_pow_sub_C hn x]
exact ne_of_gt (WithBot.coe_lt_coe.2 hn)
obtain ⟨z, hz⟩ := exists_root (X ^ n - C x) this
use z
simp only [eval_C, eval_X, eval_pow, eval_sub, IsRoot.def] at hz
exact sub_eq_zero.1 hz
#align is_alg_closed.exists_pow_nat_eq IsAlgClosed.exists_pow_nat_eq
theorem exists_eq_mul_self [IsAlgClosed k] (x : k) : ∃ z, x = z * z := by
rcases exists_pow_nat_eq x zero_lt_two with ⟨z, rfl⟩
exact ⟨z, sq z⟩
#align is_alg_closed.exists_eq_mul_self IsAlgClosed.exists_eq_mul_self
theorem roots_eq_zero_iff [IsAlgClosed k] {p : k[X]} :
p.roots = 0 ↔ p = Polynomial.C (p.coeff 0) := by
refine ⟨fun h => ?_, fun hp => by rw [hp, roots_C]⟩
rcases le_or_lt (degree p) 0 with hd | hd
· exact eq_C_of_degree_le_zero hd
· obtain ⟨z, hz⟩ := IsAlgClosed.exists_root p hd.ne'
rw [← mem_roots (ne_zero_of_degree_gt hd), h] at hz
simp at hz
#align is_alg_closed.roots_eq_zero_iff IsAlgClosed.roots_eq_zero_iff
theorem exists_eval₂_eq_zero_of_injective {R : Type*} [Ring R] [IsAlgClosed k] (f : R →+* k)
(hf : Function.Injective f) (p : R[X]) (hp : p.degree ≠ 0) : ∃ x, p.eval₂ f x = 0 :=
let ⟨x, hx⟩ := exists_root (p.map f) (by rwa [degree_map_eq_of_injective hf])
⟨x, by rwa [eval₂_eq_eval_map, ← IsRoot]⟩
#align is_alg_closed.exists_eval₂_eq_zero_of_injective IsAlgClosed.exists_eval₂_eq_zero_of_injective
theorem exists_eval₂_eq_zero {R : Type*} [Field R] [IsAlgClosed k] (f : R →+* k) (p : R[X])
(hp : p.degree ≠ 0) : ∃ x, p.eval₂ f x = 0 :=
exists_eval₂_eq_zero_of_injective f f.injective p hp
#align is_alg_closed.exists_eval₂_eq_zero IsAlgClosed.exists_eval₂_eq_zero
variable (k)
theorem exists_aeval_eq_zero_of_injective {R : Type*} [CommRing R] [IsAlgClosed k] [Algebra R k]
(hinj : Function.Injective (algebraMap R k)) (p : R[X]) (hp : p.degree ≠ 0) :
∃ x : k, aeval x p = 0 :=
exists_eval₂_eq_zero_of_injective (algebraMap R k) hinj p hp
#align is_alg_closed.exists_aeval_eq_zero_of_injective IsAlgClosed.exists_aeval_eq_zero_of_injective
theorem exists_aeval_eq_zero {R : Type*} [Field R] [IsAlgClosed k] [Algebra R k] (p : R[X])
(hp : p.degree ≠ 0) : ∃ x : k, aeval x p = 0 :=
exists_eval₂_eq_zero (algebraMap R k) p hp
#align is_alg_closed.exists_aeval_eq_zero IsAlgClosed.exists_aeval_eq_zero
theorem of_exists_root (H : ∀ p : k[X], p.Monic → Irreducible p → ∃ x, p.eval x = 0) :
IsAlgClosed k := by
refine ⟨fun p ↦ Or.inr ?_⟩
intro q hq _
have : Irreducible (q * C (leadingCoeff q)⁻¹) := by
rw [← coe_normUnit_of_ne_zero hq.ne_zero]
exact (associated_normalize _).irreducible hq
obtain ⟨x, hx⟩ := H (q * C (leadingCoeff q)⁻¹) (monic_mul_leadingCoeff_inv hq.ne_zero) this
exact degree_mul_leadingCoeff_inv q hq.ne_zero ▸ degree_eq_one_of_irreducible_of_root this hx
#align is_alg_closed.of_exists_root IsAlgClosed.of_exists_root
| Mathlib/FieldTheory/IsAlgClosed/Basic.lean | 149 | 162 | theorem of_ringEquiv (k' : Type u) [Field k'] (e : k ≃+* k')
[IsAlgClosed k] : IsAlgClosed k' := by |
apply IsAlgClosed.of_exists_root
intro p hmp hp
have hpe : degree (p.map e.symm.toRingHom) ≠ 0 := by
rw [degree_map]
exact ne_of_gt (degree_pos_of_irreducible hp)
rcases IsAlgClosed.exists_root (k := k) (p.map e.symm) hpe with ⟨x, hx⟩
use e x
rw [IsRoot] at hx
apply e.symm.injective
rw [map_zero, ← hx]
clear hx hpe hp hmp
induction p using Polynomial.induction_on <;> simp_all
| 2,027 |
import Mathlib.Data.Nat.Cast.WithTop
import Mathlib.FieldTheory.IsAlgClosed.Basic
import Mathlib.RingTheory.WittVector.DiscreteValuationRing
#align_import ring_theory.witt_vector.frobenius_fraction_field from "leanprover-community/mathlib"@"cead93130da7100f8a9fe22ee210f7636a91168f"
noncomputable section
namespace WittVector
variable (p : ℕ) [hp : Fact p.Prime]
local notation "𝕎" => WittVector p
namespace RecursionMain
section CommRing
variable {k : Type*} [CommRing k] [CharP k p]
open Polynomial
def succNthDefiningPoly (n : ℕ) (a₁ a₂ : 𝕎 k) (bs : Fin (n + 1) → k) : Polynomial k :=
X ^ p * C (a₁.coeff 0 ^ p ^ (n + 1)) - X * C (a₂.coeff 0 ^ p ^ (n + 1)) +
C
(a₁.coeff (n + 1) * (bs 0 ^ p) ^ p ^ (n + 1) +
nthRemainder p n (fun v => bs v ^ p) (truncateFun (n + 1) a₁) -
a₂.coeff (n + 1) * bs 0 ^ p ^ (n + 1) -
nthRemainder p n bs (truncateFun (n + 1) a₂))
#align witt_vector.recursion_main.succ_nth_defining_poly WittVector.RecursionMain.succNthDefiningPoly
| Mathlib/RingTheory/WittVector/FrobeniusFractionField.lean | 79 | 95 | theorem succNthDefiningPoly_degree [IsDomain k] (n : ℕ) (a₁ a₂ : 𝕎 k) (bs : Fin (n + 1) → k)
(ha₁ : a₁.coeff 0 ≠ 0) (ha₂ : a₂.coeff 0 ≠ 0) :
(succNthDefiningPoly p n a₁ a₂ bs).degree = p := by |
have : (X ^ p * C (a₁.coeff 0 ^ p ^ (n + 1))).degree = (p : WithBot ℕ) := by
rw [degree_mul, degree_C]
· simp only [Nat.cast_withBot, add_zero, degree_X, degree_pow, Nat.smul_one_eq_cast]
· exact pow_ne_zero _ ha₁
have : (X ^ p * C (a₁.coeff 0 ^ p ^ (n + 1)) - X * C (a₂.coeff 0 ^ p ^ (n + 1))).degree =
(p : WithBot ℕ) := by
rw [degree_sub_eq_left_of_degree_lt, this]
rw [this, degree_mul, degree_C, degree_X, add_zero]
· exact mod_cast hp.out.one_lt
· exact pow_ne_zero _ ha₂
rw [succNthDefiningPoly, degree_add_eq_left_of_degree_lt, this]
apply lt_of_le_of_lt degree_C_le
rw [this]
exact mod_cast hp.out.pos
| 2,028 |
import Mathlib.Algebra.DirectLimit
import Mathlib.Algebra.CharP.Algebra
import Mathlib.FieldTheory.IsAlgClosed.Basic
import Mathlib.FieldTheory.SplittingField.Construction
#align_import field_theory.is_alg_closed.algebraic_closure from "leanprover-community/mathlib"@"df76f43357840485b9d04ed5dee5ab115d420e87"
universe u v w
noncomputable section
open scoped Classical Polynomial
open Polynomial
variable (k : Type u) [Field k]
namespace AlgebraicClosure
open MvPolynomial
abbrev MonicIrreducible : Type u :=
{ f : k[X] // Monic f ∧ Irreducible f }
#align algebraic_closure.monic_irreducible AlgebraicClosure.MonicIrreducible
def evalXSelf (f : MonicIrreducible k) : MvPolynomial (MonicIrreducible k) k :=
Polynomial.eval₂ MvPolynomial.C (X f) f
set_option linter.uppercaseLean3 false in
#align algebraic_closure.eval_X_self AlgebraicClosure.evalXSelf
def spanEval : Ideal (MvPolynomial (MonicIrreducible k) k) :=
Ideal.span <| Set.range <| evalXSelf k
#align algebraic_closure.span_eval AlgebraicClosure.spanEval
def toSplittingField (s : Finset (MonicIrreducible k)) :
MvPolynomial (MonicIrreducible k) k →ₐ[k] SplittingField (∏ x ∈ s, x : k[X]) :=
MvPolynomial.aeval fun f =>
if hf : f ∈ s then
rootOfSplits _
((splits_prod_iff _ fun (j : MonicIrreducible k) _ => j.2.2.ne_zero).1
(SplittingField.splits _) f hf)
(mt isUnit_iff_degree_eq_zero.2 f.2.2.not_unit)
else 37
#align algebraic_closure.to_splitting_field AlgebraicClosure.toSplittingField
| Mathlib/FieldTheory/IsAlgClosed/AlgebraicClosure.lean | 77 | 81 | theorem toSplittingField_evalXSelf {s : Finset (MonicIrreducible k)} {f} (hf : f ∈ s) :
toSplittingField k s (evalXSelf k f) = 0 := by |
rw [toSplittingField, evalXSelf, ← AlgHom.coe_toRingHom, hom_eval₂, AlgHom.coe_toRingHom,
MvPolynomial.aeval_X, dif_pos hf, ← MvPolynomial.algebraMap_eq, AlgHom.comp_algebraMap]
exact map_rootOfSplits _ _ _
| 2,029 |
import Mathlib.Algebra.DirectLimit
import Mathlib.Algebra.CharP.Algebra
import Mathlib.FieldTheory.IsAlgClosed.Basic
import Mathlib.FieldTheory.SplittingField.Construction
#align_import field_theory.is_alg_closed.algebraic_closure from "leanprover-community/mathlib"@"df76f43357840485b9d04ed5dee5ab115d420e87"
universe u v w
noncomputable section
open scoped Classical Polynomial
open Polynomial
variable (k : Type u) [Field k]
namespace AlgebraicClosure
open MvPolynomial
abbrev MonicIrreducible : Type u :=
{ f : k[X] // Monic f ∧ Irreducible f }
#align algebraic_closure.monic_irreducible AlgebraicClosure.MonicIrreducible
def evalXSelf (f : MonicIrreducible k) : MvPolynomial (MonicIrreducible k) k :=
Polynomial.eval₂ MvPolynomial.C (X f) f
set_option linter.uppercaseLean3 false in
#align algebraic_closure.eval_X_self AlgebraicClosure.evalXSelf
def spanEval : Ideal (MvPolynomial (MonicIrreducible k) k) :=
Ideal.span <| Set.range <| evalXSelf k
#align algebraic_closure.span_eval AlgebraicClosure.spanEval
def toSplittingField (s : Finset (MonicIrreducible k)) :
MvPolynomial (MonicIrreducible k) k →ₐ[k] SplittingField (∏ x ∈ s, x : k[X]) :=
MvPolynomial.aeval fun f =>
if hf : f ∈ s then
rootOfSplits _
((splits_prod_iff _ fun (j : MonicIrreducible k) _ => j.2.2.ne_zero).1
(SplittingField.splits _) f hf)
(mt isUnit_iff_degree_eq_zero.2 f.2.2.not_unit)
else 37
#align algebraic_closure.to_splitting_field AlgebraicClosure.toSplittingField
theorem toSplittingField_evalXSelf {s : Finset (MonicIrreducible k)} {f} (hf : f ∈ s) :
toSplittingField k s (evalXSelf k f) = 0 := by
rw [toSplittingField, evalXSelf, ← AlgHom.coe_toRingHom, hom_eval₂, AlgHom.coe_toRingHom,
MvPolynomial.aeval_X, dif_pos hf, ← MvPolynomial.algebraMap_eq, AlgHom.comp_algebraMap]
exact map_rootOfSplits _ _ _
set_option linter.uppercaseLean3 false in
#align algebraic_closure.to_splitting_field_eval_X_self AlgebraicClosure.toSplittingField_evalXSelf
| Mathlib/FieldTheory/IsAlgClosed/AlgebraicClosure.lean | 85 | 94 | theorem spanEval_ne_top : spanEval k ≠ ⊤ := by |
rw [Ideal.ne_top_iff_one, spanEval, Ideal.span, ← Set.image_univ,
Finsupp.mem_span_image_iff_total]
rintro ⟨v, _, hv⟩
replace hv := congr_arg (toSplittingField k v.support) hv
rw [AlgHom.map_one, Finsupp.total_apply, Finsupp.sum, AlgHom.map_sum, Finset.sum_eq_zero] at hv
· exact zero_ne_one hv
intro j hj
rw [smul_eq_mul, AlgHom.map_mul, toSplittingField_evalXSelf (s := v.support) hj,
mul_zero]
| 2,029 |
import Mathlib.Algebra.DirectLimit
import Mathlib.Algebra.CharP.Algebra
import Mathlib.FieldTheory.IsAlgClosed.Basic
import Mathlib.FieldTheory.SplittingField.Construction
#align_import field_theory.is_alg_closed.algebraic_closure from "leanprover-community/mathlib"@"df76f43357840485b9d04ed5dee5ab115d420e87"
universe u v w
noncomputable section
open scoped Classical Polynomial
open Polynomial
variable (k : Type u) [Field k]
namespace AlgebraicClosure
open MvPolynomial
abbrev MonicIrreducible : Type u :=
{ f : k[X] // Monic f ∧ Irreducible f }
#align algebraic_closure.monic_irreducible AlgebraicClosure.MonicIrreducible
def evalXSelf (f : MonicIrreducible k) : MvPolynomial (MonicIrreducible k) k :=
Polynomial.eval₂ MvPolynomial.C (X f) f
set_option linter.uppercaseLean3 false in
#align algebraic_closure.eval_X_self AlgebraicClosure.evalXSelf
def spanEval : Ideal (MvPolynomial (MonicIrreducible k) k) :=
Ideal.span <| Set.range <| evalXSelf k
#align algebraic_closure.span_eval AlgebraicClosure.spanEval
def toSplittingField (s : Finset (MonicIrreducible k)) :
MvPolynomial (MonicIrreducible k) k →ₐ[k] SplittingField (∏ x ∈ s, x : k[X]) :=
MvPolynomial.aeval fun f =>
if hf : f ∈ s then
rootOfSplits _
((splits_prod_iff _ fun (j : MonicIrreducible k) _ => j.2.2.ne_zero).1
(SplittingField.splits _) f hf)
(mt isUnit_iff_degree_eq_zero.2 f.2.2.not_unit)
else 37
#align algebraic_closure.to_splitting_field AlgebraicClosure.toSplittingField
theorem toSplittingField_evalXSelf {s : Finset (MonicIrreducible k)} {f} (hf : f ∈ s) :
toSplittingField k s (evalXSelf k f) = 0 := by
rw [toSplittingField, evalXSelf, ← AlgHom.coe_toRingHom, hom_eval₂, AlgHom.coe_toRingHom,
MvPolynomial.aeval_X, dif_pos hf, ← MvPolynomial.algebraMap_eq, AlgHom.comp_algebraMap]
exact map_rootOfSplits _ _ _
set_option linter.uppercaseLean3 false in
#align algebraic_closure.to_splitting_field_eval_X_self AlgebraicClosure.toSplittingField_evalXSelf
theorem spanEval_ne_top : spanEval k ≠ ⊤ := by
rw [Ideal.ne_top_iff_one, spanEval, Ideal.span, ← Set.image_univ,
Finsupp.mem_span_image_iff_total]
rintro ⟨v, _, hv⟩
replace hv := congr_arg (toSplittingField k v.support) hv
rw [AlgHom.map_one, Finsupp.total_apply, Finsupp.sum, AlgHom.map_sum, Finset.sum_eq_zero] at hv
· exact zero_ne_one hv
intro j hj
rw [smul_eq_mul, AlgHom.map_mul, toSplittingField_evalXSelf (s := v.support) hj,
mul_zero]
#align algebraic_closure.span_eval_ne_top AlgebraicClosure.spanEval_ne_top
def maxIdeal : Ideal (MvPolynomial (MonicIrreducible k) k) :=
Classical.choose <| Ideal.exists_le_maximal _ <| spanEval_ne_top k
#align algebraic_closure.max_ideal AlgebraicClosure.maxIdeal
instance maxIdeal.isMaximal : (maxIdeal k).IsMaximal :=
(Classical.choose_spec <| Ideal.exists_le_maximal _ <| spanEval_ne_top k).1
#align algebraic_closure.max_ideal.is_maximal AlgebraicClosure.maxIdeal.isMaximal
theorem le_maxIdeal : spanEval k ≤ maxIdeal k :=
(Classical.choose_spec <| Ideal.exists_le_maximal _ <| spanEval_ne_top k).2
#align algebraic_closure.le_max_ideal AlgebraicClosure.le_maxIdeal
def AdjoinMonic : Type u :=
MvPolynomial (MonicIrreducible k) k ⧸ maxIdeal k
#align algebraic_closure.adjoin_monic AlgebraicClosure.AdjoinMonic
instance AdjoinMonic.field : Field (AdjoinMonic k) :=
Ideal.Quotient.field _
#align algebraic_closure.adjoin_monic.field AlgebraicClosure.AdjoinMonic.field
instance AdjoinMonic.inhabited : Inhabited (AdjoinMonic k) :=
⟨37⟩
#align algebraic_closure.adjoin_monic.inhabited AlgebraicClosure.AdjoinMonic.inhabited
def toAdjoinMonic : k →+* AdjoinMonic k :=
(Ideal.Quotient.mk _).comp C
#align algebraic_closure.to_adjoin_monic AlgebraicClosure.toAdjoinMonic
instance AdjoinMonic.algebra : Algebra k (AdjoinMonic k) :=
(toAdjoinMonic k).toAlgebra
#align algebraic_closure.adjoin_monic.algebra AlgebraicClosure.AdjoinMonic.algebra
set_option backward.isDefEq.lazyWhnfCore false in -- See https://github.com/leanprover-community/mathlib4/issues/12534
-- Porting note: In the statement, the type of `C` had to be made explicit.
theorem AdjoinMonic.algebraMap : algebraMap k (AdjoinMonic k) = (Ideal.Quotient.mk _).comp
(C : k →+* MvPolynomial (MonicIrreducible k) k) := rfl
#align algebraic_closure.adjoin_monic.algebra_map AlgebraicClosure.AdjoinMonic.algebraMap
| Mathlib/FieldTheory/IsAlgClosed/AlgebraicClosure.lean | 138 | 148 | theorem AdjoinMonic.isIntegral (z : AdjoinMonic k) : IsIntegral k z := by |
let ⟨p, hp⟩ := Ideal.Quotient.mk_surjective z
rw [← hp]
induction p using MvPolynomial.induction_on generalizing z with
| h_C => exact isIntegral_algebraMap
| h_add _ _ ha hb => exact (ha _ rfl).add (hb _ rfl)
| h_X p f ih =>
refine @IsIntegral.mul k _ _ _ _ _ (Ideal.Quotient.mk (maxIdeal k) _) (ih _ rfl) ?_
refine ⟨f, f.2.1, ?_⟩
erw [AdjoinMonic.algebraMap, ← hom_eval₂, Ideal.Quotient.eq_zero_iff_mem]
exact le_maxIdeal k (Ideal.subset_span ⟨f, rfl⟩)
| 2,029 |
import Mathlib.FieldTheory.SplittingField.Construction
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Separable
import Mathlib.FieldTheory.NormalClosure
import Mathlib.RingTheory.Polynomial.SeparableDegree
open scoped Classical Polynomial
open FiniteDimensional Polynomial IntermediateField Field
noncomputable section
universe u v w
variable (F : Type u) (E : Type v) [Field F] [Field E] [Algebra F E]
variable (K : Type w) [Field K] [Algebra F K]
namespace Field
def Emb := E →ₐ[F] AlgebraicClosure E
def finSepDegree : ℕ := Nat.card (Emb F E)
instance instInhabitedEmb : Inhabited (Emb F E) := ⟨IsScalarTower.toAlgHom F E _⟩
instance instNeZeroFinSepDegree [FiniteDimensional F E] : NeZero (finSepDegree F E) :=
⟨Nat.card_ne_zero.2 ⟨inferInstance, Fintype.finite <| minpoly.AlgHom.fintype _ _ _⟩⟩
def embEquivOfEquiv (i : E ≃ₐ[F] K) :
Emb F E ≃ Emb F K := AlgEquiv.arrowCongr i <| AlgEquiv.symm <| by
let _ : Algebra E K := i.toAlgHom.toRingHom.toAlgebra
have : Algebra.IsAlgebraic E K := by
constructor
intro x
have h := isAlgebraic_algebraMap (R := E) (A := K) (i.symm.toAlgHom x)
rw [show ∀ y : E, (algebraMap E K) y = i.toAlgHom y from fun y ↦ rfl] at h
simpa only [AlgEquiv.toAlgHom_eq_coe, AlgHom.coe_coe, AlgEquiv.apply_symm_apply] using h
apply AlgEquiv.restrictScalars (R := F) (S := E)
exact IsAlgClosure.equivOfAlgebraic E K (AlgebraicClosure K) (AlgebraicClosure E)
theorem finSepDegree_eq_of_equiv (i : E ≃ₐ[F] K) :
finSepDegree F E = finSepDegree F K := Nat.card_congr (embEquivOfEquiv F E K i)
@[simp]
| Mathlib/FieldTheory/SeparableDegree.lean | 168 | 172 | theorem finSepDegree_self : finSepDegree F F = 1 := by |
have : Cardinal.mk (Emb F F) = 1 := le_antisymm
(Cardinal.le_one_iff_subsingleton.2 AlgHom.subsingleton)
(Cardinal.one_le_iff_ne_zero.2 <| Cardinal.mk_ne_zero _)
rw [finSepDegree, Nat.card, this, Cardinal.one_toNat]
| 2,030 |
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.RingTheory.IntegralDomain
#align_import field_theory.primitive_element from "leanprover-community/mathlib"@"df76f43357840485b9d04ed5dee5ab115d420e87"
noncomputable section
open scoped Classical Polynomial
open FiniteDimensional Polynomial IntermediateField
namespace Field
section PrimitiveElementFinite
variable (F : Type*) [Field F] (E : Type*) [Field E] [Algebra F E]
| Mathlib/FieldTheory/PrimitiveElement.lean | 56 | 67 | theorem exists_primitive_element_of_finite_top [Finite E] : ∃ α : E, F⟮α⟯ = ⊤ := by |
obtain ⟨α, hα⟩ := @IsCyclic.exists_generator Eˣ _ _
use α
rw [eq_top_iff]
rintro x -
by_cases hx : x = 0
· rw [hx]
exact F⟮α.val⟯.zero_mem
· obtain ⟨n, hn⟩ := Set.mem_range.mp (hα (Units.mk0 x hx))
simp only at hn
rw [show x = α ^ n by norm_cast; rw [hn, Units.val_mk0]]
exact zpow_mem (mem_adjoin_simple_self F (E := E) ↑α) n
| 2,031 |
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.RingTheory.IntegralDomain
#align_import field_theory.primitive_element from "leanprover-community/mathlib"@"df76f43357840485b9d04ed5dee5ab115d420e87"
noncomputable section
open scoped Classical Polynomial
open FiniteDimensional Polynomial IntermediateField
namespace Field
section PrimitiveElementInf
variable {F : Type*} [Field F] [Infinite F] {E : Type*} [Field E] (ϕ : F →+* E) (α β : E)
| Mathlib/FieldTheory/PrimitiveElement.lean | 86 | 96 | theorem primitive_element_inf_aux_exists_c (f g : F[X]) :
∃ c : F, ∀ α' ∈ (f.map ϕ).roots, ∀ β' ∈ (g.map ϕ).roots, -(α' - α) / (β' - β) ≠ ϕ c := by |
let sf := (f.map ϕ).roots
let sg := (g.map ϕ).roots
let s := (sf.bind fun α' => sg.map fun β' => -(α' - α) / (β' - β)).toFinset
let s' := s.preimage ϕ fun x _ y _ h => ϕ.injective h
obtain ⟨c, hc⟩ := Infinite.exists_not_mem_finset s'
simp_rw [s', s, Finset.mem_preimage, Multiset.mem_toFinset, Multiset.mem_bind, Multiset.mem_map]
at hc
push_neg at hc
exact ⟨c, hc⟩
| 2,031 |
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.RingTheory.IntegralDomain
#align_import field_theory.primitive_element from "leanprover-community/mathlib"@"df76f43357840485b9d04ed5dee5ab115d420e87"
noncomputable section
open scoped Classical Polynomial
open FiniteDimensional Polynomial IntermediateField
namespace Field
section PrimitiveElementInf
variable {F : Type*} [Field F] [Infinite F] {E : Type*} [Field E] (ϕ : F →+* E) (α β : E)
theorem primitive_element_inf_aux_exists_c (f g : F[X]) :
∃ c : F, ∀ α' ∈ (f.map ϕ).roots, ∀ β' ∈ (g.map ϕ).roots, -(α' - α) / (β' - β) ≠ ϕ c := by
let sf := (f.map ϕ).roots
let sg := (g.map ϕ).roots
let s := (sf.bind fun α' => sg.map fun β' => -(α' - α) / (β' - β)).toFinset
let s' := s.preimage ϕ fun x _ y _ h => ϕ.injective h
obtain ⟨c, hc⟩ := Infinite.exists_not_mem_finset s'
simp_rw [s', s, Finset.mem_preimage, Multiset.mem_toFinset, Multiset.mem_bind, Multiset.mem_map]
at hc
push_neg at hc
exact ⟨c, hc⟩
#align field.primitive_element_inf_aux_exists_c Field.primitive_element_inf_aux_exists_c
variable (F)
variable [Algebra F E]
| Mathlib/FieldTheory/PrimitiveElement.lean | 104 | 173 | theorem primitive_element_inf_aux [IsSeparable F E] : ∃ γ : E, F⟮α, β⟯ = F⟮γ⟯ := by |
have hα := IsSeparable.isIntegral F α
have hβ := IsSeparable.isIntegral F β
let f := minpoly F α
let g := minpoly F β
let ιFE := algebraMap F E
let ιEE' := algebraMap E (SplittingField (g.map ιFE))
obtain ⟨c, hc⟩ := primitive_element_inf_aux_exists_c (ιEE'.comp ιFE) (ιEE' α) (ιEE' β) f g
let γ := α + c • β
suffices β_in_Fγ : β ∈ F⟮γ⟯ by
use γ
apply le_antisymm
· rw [adjoin_le_iff]
have α_in_Fγ : α ∈ F⟮γ⟯ := by
rw [← add_sub_cancel_right α (c • β)]
exact F⟮γ⟯.sub_mem (mem_adjoin_simple_self F γ) (F⟮γ⟯.toSubalgebra.smul_mem β_in_Fγ c)
rintro x (rfl | rfl) <;> assumption
· rw [adjoin_simple_le_iff]
have α_in_Fαβ : α ∈ F⟮α, β⟯ := subset_adjoin F {α, β} (Set.mem_insert α {β})
have β_in_Fαβ : β ∈ F⟮α, β⟯ := subset_adjoin F {α, β} (Set.mem_insert_of_mem α rfl)
exact F⟮α, β⟯.add_mem α_in_Fαβ (F⟮α, β⟯.smul_mem β_in_Fαβ)
let p := EuclideanDomain.gcd ((f.map (algebraMap F F⟮γ⟯)).comp
(C (AdjoinSimple.gen F γ) - (C ↑c : F⟮γ⟯[X]) * X)) (g.map (algebraMap F F⟮γ⟯))
let h := EuclideanDomain.gcd ((f.map ιFE).comp (C γ - C (ιFE c) * X)) (g.map ιFE)
have map_g_ne_zero : g.map ιFE ≠ 0 := map_ne_zero (minpoly.ne_zero hβ)
have h_ne_zero : h ≠ 0 :=
mt EuclideanDomain.gcd_eq_zero_iff.mp (not_and.mpr fun _ => map_g_ne_zero)
suffices p_linear : p.map (algebraMap F⟮γ⟯ E) = C h.leadingCoeff * (X - C β) by
have finale : β = algebraMap F⟮γ⟯ E (-p.coeff 0 / p.coeff 1) := by
rw [map_div₀, RingHom.map_neg, ← coeff_map, ← coeff_map, p_linear]
-- Porting note: had to add `-map_add` to avoid going in the wrong direction.
simp [mul_sub, coeff_C, mul_div_cancel_left₀ β (mt leadingCoeff_eq_zero.mp h_ne_zero),
-map_add]
-- Porting note: an alternative solution is:
-- simp_rw [Polynomial.coeff_C_mul, Polynomial.coeff_sub, mul_sub,
-- Polynomial.coeff_X_zero, Polynomial.coeff_X_one, mul_zero, mul_one, zero_sub, neg_neg,
-- Polynomial.coeff_C, eq_self_iff_true, Nat.one_ne_zero, if_true, if_false, mul_zero,
-- sub_zero, mul_div_cancel_left β (mt leadingCoeff_eq_zero.mp h_ne_zero)]
rw [finale]
exact Subtype.mem (-p.coeff 0 / p.coeff 1)
have h_sep : h.Separable := separable_gcd_right _ (IsSeparable.separable F β).map
have h_root : h.eval β = 0 := by
apply eval_gcd_eq_zero
· rw [eval_comp, eval_sub, eval_mul, eval_C, eval_C, eval_X, eval_map, ← aeval_def, ←
Algebra.smul_def, add_sub_cancel_right, minpoly.aeval]
· rw [eval_map, ← aeval_def, minpoly.aeval]
have h_splits : Splits ιEE' h :=
splits_of_splits_gcd_right ιEE' map_g_ne_zero (SplittingField.splits _)
have h_roots : ∀ x ∈ (h.map ιEE').roots, x = ιEE' β := by
intro x hx
rw [mem_roots_map h_ne_zero] at hx
specialize hc (ιEE' γ - ιEE' (ιFE c) * x) (by
have f_root := root_left_of_root_gcd hx
rw [eval₂_comp, eval₂_sub, eval₂_mul, eval₂_C, eval₂_C, eval₂_X, eval₂_map] at f_root
exact (mem_roots_map (minpoly.ne_zero hα)).mpr f_root)
specialize hc x (by
rw [mem_roots_map (minpoly.ne_zero hβ), ← eval₂_map]
exact root_right_of_root_gcd hx)
by_contra a
apply hc
apply (div_eq_iff (sub_ne_zero.mpr a)).mpr
simp only [γ, Algebra.smul_def, RingHom.map_add, RingHom.map_mul, RingHom.comp_apply]
ring
rw [← eq_X_sub_C_of_separable_of_root_eq h_sep h_root h_splits h_roots]
trans EuclideanDomain.gcd (?_ : E[X]) (?_ : E[X])
· dsimp only [γ]
convert (gcd_map (algebraMap F⟮γ⟯ E)).symm
· simp only [map_comp, Polynomial.map_map, ← IsScalarTower.algebraMap_eq, Polynomial.map_sub,
map_C, AdjoinSimple.algebraMap_gen, map_add, Polynomial.map_mul, map_X]
congr
| 2,031 |
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.RingTheory.IntegralDomain
#align_import field_theory.primitive_element from "leanprover-community/mathlib"@"df76f43357840485b9d04ed5dee5ab115d420e87"
noncomputable section
open scoped Classical Polynomial
open FiniteDimensional Polynomial IntermediateField
namespace Field
variable (F E : Type*) [Field F] [Field E]
variable [Algebra F E]
section FiniteIntermediateField
-- TODO: show a more generalized result: [F⟮α⟯ : F⟮α ^ m⟯] = m if m > 0 and α transcendental.
| Mathlib/FieldTheory/PrimitiveElement.lean | 246 | 275 | theorem isAlgebraic_of_adjoin_eq_adjoin {α : E} {m n : ℕ} (hneq : m ≠ n)
(heq : F⟮α ^ m⟯ = F⟮α ^ n⟯) : IsAlgebraic F α := by |
wlog hmn : m < n
· exact this F E hneq.symm heq.symm (hneq.lt_or_lt.resolve_left hmn)
by_cases hm : m = 0
· rw [hm] at heq hmn
simp only [pow_zero, adjoin_one] at heq
obtain ⟨y, h⟩ := mem_bot.1 (heq.symm ▸ mem_adjoin_simple_self F (α ^ n))
refine ⟨X ^ n - C y, X_pow_sub_C_ne_zero hmn y, ?_⟩
simp only [map_sub, map_pow, aeval_X, aeval_C, h, sub_self]
obtain ⟨r, s, h⟩ := (mem_adjoin_simple_iff F _).1 (heq ▸ mem_adjoin_simple_self F (α ^ m))
by_cases hzero : aeval (α ^ n) s = 0
· simp only [hzero, div_zero, pow_eq_zero_iff hm] at h
exact h.symm ▸ isAlgebraic_zero
replace hm : 0 < m := Nat.pos_of_ne_zero hm
rw [eq_div_iff hzero, ← sub_eq_zero] at h
replace hzero : s ≠ 0 := by rintro rfl; simp only [map_zero, not_true_eq_false] at hzero
let f : F[X] := X ^ m * expand F n s - expand F n r
refine ⟨f, ?_, ?_⟩
· have : f.coeff (n * s.natDegree + m) ≠ 0 := by
have hn : 0 < n := by linarith only [hm, hmn]
have hndvd : ¬ n ∣ n * s.natDegree + m := by
rw [← Nat.dvd_add_iff_right (n.dvd_mul_right s.natDegree)]
exact Nat.not_dvd_of_pos_of_lt hm hmn
simp only [f, coeff_sub, coeff_X_pow_mul, s.coeff_expand_mul' hn, coeff_natDegree,
coeff_expand hn r, hndvd, ite_false, sub_zero]
exact leadingCoeff_ne_zero.2 hzero
intro h
simp only [h, coeff_zero, ne_eq, not_true_eq_false] at this
· simp only [f, map_sub, map_mul, map_pow, aeval_X, expand_aeval, h]
| 2,031 |
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.RingTheory.IntegralDomain
#align_import field_theory.primitive_element from "leanprover-community/mathlib"@"df76f43357840485b9d04ed5dee5ab115d420e87"
noncomputable section
open scoped Classical Polynomial
open FiniteDimensional Polynomial IntermediateField
namespace Field
variable (F E : Type*) [Field F] [Field E]
variable [Algebra F E]
section FiniteIntermediateField
-- TODO: show a more generalized result: [F⟮α⟯ : F⟮α ^ m⟯] = m if m > 0 and α transcendental.
theorem isAlgebraic_of_adjoin_eq_adjoin {α : E} {m n : ℕ} (hneq : m ≠ n)
(heq : F⟮α ^ m⟯ = F⟮α ^ n⟯) : IsAlgebraic F α := by
wlog hmn : m < n
· exact this F E hneq.symm heq.symm (hneq.lt_or_lt.resolve_left hmn)
by_cases hm : m = 0
· rw [hm] at heq hmn
simp only [pow_zero, adjoin_one] at heq
obtain ⟨y, h⟩ := mem_bot.1 (heq.symm ▸ mem_adjoin_simple_self F (α ^ n))
refine ⟨X ^ n - C y, X_pow_sub_C_ne_zero hmn y, ?_⟩
simp only [map_sub, map_pow, aeval_X, aeval_C, h, sub_self]
obtain ⟨r, s, h⟩ := (mem_adjoin_simple_iff F _).1 (heq ▸ mem_adjoin_simple_self F (α ^ m))
by_cases hzero : aeval (α ^ n) s = 0
· simp only [hzero, div_zero, pow_eq_zero_iff hm] at h
exact h.symm ▸ isAlgebraic_zero
replace hm : 0 < m := Nat.pos_of_ne_zero hm
rw [eq_div_iff hzero, ← sub_eq_zero] at h
replace hzero : s ≠ 0 := by rintro rfl; simp only [map_zero, not_true_eq_false] at hzero
let f : F[X] := X ^ m * expand F n s - expand F n r
refine ⟨f, ?_, ?_⟩
· have : f.coeff (n * s.natDegree + m) ≠ 0 := by
have hn : 0 < n := by linarith only [hm, hmn]
have hndvd : ¬ n ∣ n * s.natDegree + m := by
rw [← Nat.dvd_add_iff_right (n.dvd_mul_right s.natDegree)]
exact Nat.not_dvd_of_pos_of_lt hm hmn
simp only [f, coeff_sub, coeff_X_pow_mul, s.coeff_expand_mul' hn, coeff_natDegree,
coeff_expand hn r, hndvd, ite_false, sub_zero]
exact leadingCoeff_ne_zero.2 hzero
intro h
simp only [h, coeff_zero, ne_eq, not_true_eq_false] at this
· simp only [f, map_sub, map_mul, map_pow, aeval_X, expand_aeval, h]
theorem isAlgebraic_of_finite_intermediateField
[Finite (IntermediateField F E)] : Algebra.IsAlgebraic F E := ⟨fun α ↦
have ⟨_m, _n, hneq, heq⟩ := Finite.exists_ne_map_eq_of_infinite fun n ↦ F⟮α ^ n⟯
isAlgebraic_of_adjoin_eq_adjoin F E hneq heq⟩
| Mathlib/FieldTheory/PrimitiveElement.lean | 282 | 292 | theorem FiniteDimensional.of_finite_intermediateField
[Finite (IntermediateField F E)] : FiniteDimensional F E := by |
let IF := { K : IntermediateField F E // ∃ x, K = F⟮x⟯ }
have := isAlgebraic_of_finite_intermediateField F E
haveI : ∀ K : IF, FiniteDimensional F K.1 := fun ⟨_, x, rfl⟩ ↦ adjoin.finiteDimensional
(Algebra.IsIntegral.isIntegral _)
have hfin := finiteDimensional_iSup_of_finite (t := fun K : IF ↦ K.1)
have htop : ⨆ K : IF, K.1 = ⊤ := le_top.antisymm fun x _ ↦
le_iSup (fun K : IF ↦ K.1) ⟨F⟮x⟯, x, rfl⟩ <| mem_adjoin_simple_self F x
rw [htop] at hfin
exact topEquiv.toLinearEquiv.finiteDimensional
| 2,031 |
import Mathlib.FieldTheory.Fixed
import Mathlib.FieldTheory.NormalClosure
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.GroupTheory.GroupAction.FixingSubgroup
#align_import field_theory.galois from "leanprover-community/mathlib"@"9fb8964792b4237dac6200193a0d533f1b3f7423"
open scoped Polynomial IntermediateField
open FiniteDimensional AlgEquiv
section
variable (F : Type*) [Field F] (E : Type*) [Field E] [Algebra F E]
class IsGalois : Prop where
[to_isSeparable : IsSeparable F E]
[to_normal : Normal F E]
#align is_galois IsGalois
variable {F E}
theorem isGalois_iff : IsGalois F E ↔ IsSeparable F E ∧ Normal F E :=
⟨fun h => ⟨h.1, h.2⟩, fun h =>
{ to_isSeparable := h.1
to_normal := h.2 }⟩
#align is_galois_iff isGalois_iff
attribute [instance 100] IsGalois.to_isSeparable IsGalois.to_normal
-- see Note [lower instance priority]
variable (F E)
namespace IsGalois
instance self : IsGalois F F :=
⟨⟩
#align is_galois.self IsGalois.self
variable {E}
theorem integral [IsGalois F E] (x : E) : IsIntegral F x :=
to_normal.isIntegral x
#align is_galois.integral IsGalois.integral
theorem separable [IsGalois F E] (x : E) : (minpoly F x).Separable :=
IsSeparable.separable F x
#align is_galois.separable IsGalois.separable
theorem splits [IsGalois F E] (x : E) : (minpoly F x).Splits (algebraMap F E) :=
Normal.splits' x
#align is_galois.splits IsGalois.splits
variable (E)
instance of_fixed_field (G : Type*) [Group G] [Finite G] [MulSemiringAction G E] :
IsGalois (FixedPoints.subfield G E) E :=
⟨⟩
#align is_galois.of_fixed_field IsGalois.of_fixed_field
| Mathlib/FieldTheory/Galois.lean | 93 | 100 | theorem IntermediateField.AdjoinSimple.card_aut_eq_finrank [FiniteDimensional F E] {α : E}
(hα : IsIntegral F α) (h_sep : (minpoly F α).Separable)
(h_splits : (minpoly F α).Splits (algebraMap F F⟮α⟯)) :
Fintype.card (F⟮α⟯ ≃ₐ[F] F⟮α⟯) = finrank F F⟮α⟯ := by |
letI : Fintype (F⟮α⟯ →ₐ[F] F⟮α⟯) := IntermediateField.fintypeOfAlgHomAdjoinIntegral F hα
rw [IntermediateField.adjoin.finrank hα]
rw [← IntermediateField.card_algHom_adjoin_integral F hα h_sep h_splits]
exact Fintype.card_congr (algEquivEquivAlgHom F F⟮α⟯)
| 2,032 |
import Mathlib.FieldTheory.Fixed
import Mathlib.FieldTheory.NormalClosure
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.GroupTheory.GroupAction.FixingSubgroup
#align_import field_theory.galois from "leanprover-community/mathlib"@"9fb8964792b4237dac6200193a0d533f1b3f7423"
open scoped Polynomial IntermediateField
open FiniteDimensional AlgEquiv
section
variable (F : Type*) [Field F] (E : Type*) [Field E] [Algebra F E]
class IsGalois : Prop where
[to_isSeparable : IsSeparable F E]
[to_normal : Normal F E]
#align is_galois IsGalois
variable {F E}
theorem isGalois_iff : IsGalois F E ↔ IsSeparable F E ∧ Normal F E :=
⟨fun h => ⟨h.1, h.2⟩, fun h =>
{ to_isSeparable := h.1
to_normal := h.2 }⟩
#align is_galois_iff isGalois_iff
attribute [instance 100] IsGalois.to_isSeparable IsGalois.to_normal
-- see Note [lower instance priority]
variable (F E)
namespace IsGalois
instance self : IsGalois F F :=
⟨⟩
#align is_galois.self IsGalois.self
variable {E}
theorem integral [IsGalois F E] (x : E) : IsIntegral F x :=
to_normal.isIntegral x
#align is_galois.integral IsGalois.integral
theorem separable [IsGalois F E] (x : E) : (minpoly F x).Separable :=
IsSeparable.separable F x
#align is_galois.separable IsGalois.separable
theorem splits [IsGalois F E] (x : E) : (minpoly F x).Splits (algebraMap F E) :=
Normal.splits' x
#align is_galois.splits IsGalois.splits
variable (E)
instance of_fixed_field (G : Type*) [Group G] [Finite G] [MulSemiringAction G E] :
IsGalois (FixedPoints.subfield G E) E :=
⟨⟩
#align is_galois.of_fixed_field IsGalois.of_fixed_field
theorem IntermediateField.AdjoinSimple.card_aut_eq_finrank [FiniteDimensional F E] {α : E}
(hα : IsIntegral F α) (h_sep : (minpoly F α).Separable)
(h_splits : (minpoly F α).Splits (algebraMap F F⟮α⟯)) :
Fintype.card (F⟮α⟯ ≃ₐ[F] F⟮α⟯) = finrank F F⟮α⟯ := by
letI : Fintype (F⟮α⟯ →ₐ[F] F⟮α⟯) := IntermediateField.fintypeOfAlgHomAdjoinIntegral F hα
rw [IntermediateField.adjoin.finrank hα]
rw [← IntermediateField.card_algHom_adjoin_integral F hα h_sep h_splits]
exact Fintype.card_congr (algEquivEquivAlgHom F F⟮α⟯)
#align is_galois.intermediate_field.adjoin_simple.card_aut_eq_finrank IsGalois.IntermediateField.AdjoinSimple.card_aut_eq_finrank
| Mathlib/FieldTheory/Galois.lean | 103 | 125 | theorem card_aut_eq_finrank [FiniteDimensional F E] [IsGalois F E] :
Fintype.card (E ≃ₐ[F] E) = finrank F E := by |
cases' Field.exists_primitive_element F E with α hα
let iso : F⟮α⟯ ≃ₐ[F] E :=
{ toFun := fun e => e.val
invFun := fun e => ⟨e, by rw [hα]; exact IntermediateField.mem_top⟩
left_inv := fun _ => by ext; rfl
right_inv := fun _ => rfl
map_mul' := fun _ _ => rfl
map_add' := fun _ _ => rfl
commutes' := fun _ => rfl }
have H : IsIntegral F α := IsGalois.integral F α
have h_sep : (minpoly F α).Separable := IsGalois.separable F α
have h_splits : (minpoly F α).Splits (algebraMap F E) := IsGalois.splits F α
replace h_splits : Polynomial.Splits (algebraMap F F⟮α⟯) (minpoly F α) := by
simpa using
Polynomial.splits_comp_of_splits (algebraMap F E) iso.symm.toAlgHom.toRingHom h_splits
rw [← LinearEquiv.finrank_eq iso.toLinearEquiv]
rw [← IntermediateField.AdjoinSimple.card_aut_eq_finrank F E H h_sep h_splits]
apply Fintype.card_congr
apply Equiv.mk (fun ϕ => iso.trans (ϕ.trans iso.symm)) fun ϕ => iso.symm.trans (ϕ.trans iso)
· intro ϕ; ext1; simp only [trans_apply, apply_symm_apply]
· intro ϕ; ext1; simp only [trans_apply, symm_apply_apply]
| 2,032 |
import Mathlib.Algebra.CharP.Algebra
import Mathlib.Data.ZMod.Algebra
import Mathlib.FieldTheory.Finite.Basic
import Mathlib.FieldTheory.Galois
import Mathlib.FieldTheory.SplittingField.IsSplittingField
#align_import field_theory.finite.galois_field from "leanprover-community/mathlib"@"0723536a0522d24fc2f159a096fb3304bef77472"
noncomputable section
open Polynomial Finset
open scoped Polynomial
instance FiniteField.isSplittingField_sub (K F : Type*) [Field K] [Fintype K]
[Field F] [Algebra F K] : IsSplittingField F K (X ^ Fintype.card K - X) where
splits' := by
have h : (X ^ Fintype.card K - X : K[X]).natDegree = Fintype.card K :=
FiniteField.X_pow_card_sub_X_natDegree_eq K Fintype.one_lt_card
rw [← splits_id_iff_splits, splits_iff_card_roots, Polynomial.map_sub, Polynomial.map_pow,
map_X, h, FiniteField.roots_X_pow_card_sub_X K, ← Finset.card_def, Finset.card_univ]
adjoin_rootSet' := by
classical
trans Algebra.adjoin F ((roots (X ^ Fintype.card K - X : K[X])).toFinset : Set K)
· simp only [rootSet, aroots, Polynomial.map_pow, map_X, Polynomial.map_sub]
· rw [FiniteField.roots_X_pow_card_sub_X, val_toFinset, coe_univ, Algebra.adjoin_univ]
#align finite_field.has_sub.sub.polynomial.is_splitting_field FiniteField.isSplittingField_sub
| Mathlib/FieldTheory/Finite/GaloisField.lean | 55 | 60 | theorem galois_poly_separable {K : Type*} [Field K] (p q : ℕ) [CharP K p] (h : p ∣ q) :
Separable (X ^ q - X : K[X]) := by |
use 1, X ^ q - X - 1
rw [← CharP.cast_eq_zero_iff K[X] p] at h
rw [derivative_sub, derivative_X_pow, derivative_X, C_eq_natCast, h]
ring
| 2,033 |
import Mathlib.Algebra.CharP.Algebra
import Mathlib.Data.ZMod.Algebra
import Mathlib.FieldTheory.Finite.Basic
import Mathlib.FieldTheory.Galois
import Mathlib.FieldTheory.SplittingField.IsSplittingField
#align_import field_theory.finite.galois_field from "leanprover-community/mathlib"@"0723536a0522d24fc2f159a096fb3304bef77472"
noncomputable section
open Polynomial Finset
open scoped Polynomial
instance FiniteField.isSplittingField_sub (K F : Type*) [Field K] [Fintype K]
[Field F] [Algebra F K] : IsSplittingField F K (X ^ Fintype.card K - X) where
splits' := by
have h : (X ^ Fintype.card K - X : K[X]).natDegree = Fintype.card K :=
FiniteField.X_pow_card_sub_X_natDegree_eq K Fintype.one_lt_card
rw [← splits_id_iff_splits, splits_iff_card_roots, Polynomial.map_sub, Polynomial.map_pow,
map_X, h, FiniteField.roots_X_pow_card_sub_X K, ← Finset.card_def, Finset.card_univ]
adjoin_rootSet' := by
classical
trans Algebra.adjoin F ((roots (X ^ Fintype.card K - X : K[X])).toFinset : Set K)
· simp only [rootSet, aroots, Polynomial.map_pow, map_X, Polynomial.map_sub]
· rw [FiniteField.roots_X_pow_card_sub_X, val_toFinset, coe_univ, Algebra.adjoin_univ]
#align finite_field.has_sub.sub.polynomial.is_splitting_field FiniteField.isSplittingField_sub
theorem galois_poly_separable {K : Type*} [Field K] (p q : ℕ) [CharP K p] (h : p ∣ q) :
Separable (X ^ q - X : K[X]) := by
use 1, X ^ q - X - 1
rw [← CharP.cast_eq_zero_iff K[X] p] at h
rw [derivative_sub, derivative_X_pow, derivative_X, C_eq_natCast, h]
ring
#align galois_poly_separable galois_poly_separable
variable (p : ℕ) [Fact p.Prime] (n : ℕ)
def GaloisField := SplittingField (X ^ p ^ n - X : (ZMod p)[X])
-- deriving Field -- Porting note: see https://github.com/leanprover-community/mathlib4/issues/5020
#align galois_field GaloisField
instance : Field (GaloisField p n) :=
inferInstanceAs (Field (SplittingField _))
instance : Inhabited (@GaloisField 2 (Fact.mk Nat.prime_two) 1) := ⟨37⟩
namespace GaloisField
variable (p : ℕ) [h_prime : Fact p.Prime] (n : ℕ)
instance : Algebra (ZMod p) (GaloisField p n) := SplittingField.algebra _
instance : IsSplittingField (ZMod p) (GaloisField p n) (X ^ p ^ n - X) :=
Polynomial.IsSplittingField.splittingField _
instance : CharP (GaloisField p n) p :=
(Algebra.charP_iff (ZMod p) (GaloisField p n) p).mp (by infer_instance)
instance : FiniteDimensional (ZMod p) (GaloisField p n) := by
dsimp only [GaloisField]; infer_instance
instance : Fintype (GaloisField p n) := by
dsimp only [GaloisField]
exact FiniteDimensional.fintypeOfFintype (ZMod p) (GaloisField p n)
| Mathlib/FieldTheory/Finite/GaloisField.lean | 96 | 143 | theorem finrank {n} (h : n ≠ 0) : FiniteDimensional.finrank (ZMod p) (GaloisField p n) = n := by |
set g_poly := (X ^ p ^ n - X : (ZMod p)[X])
have hp : 1 < p := h_prime.out.one_lt
have aux : g_poly ≠ 0 := FiniteField.X_pow_card_pow_sub_X_ne_zero _ h hp
-- Porting note: in the statment of `key`, replaced `g_poly` by its value otherwise the
-- proof fails
have key : Fintype.card (g_poly.rootSet (GaloisField p n)) = g_poly.natDegree :=
card_rootSet_eq_natDegree (galois_poly_separable p _ (dvd_pow (dvd_refl p) h))
(SplittingField.splits (X ^ p ^ n - X : (ZMod p)[X]))
have nat_degree_eq : g_poly.natDegree = p ^ n :=
FiniteField.X_pow_card_pow_sub_X_natDegree_eq _ h hp
rw [nat_degree_eq] at key
suffices g_poly.rootSet (GaloisField p n) = Set.univ by
simp_rw [this, ← Fintype.ofEquiv_card (Equiv.Set.univ _)] at key
-- Porting note: prevents `card_eq_pow_finrank` from using a wrong instance for `Fintype`
rw [@card_eq_pow_finrank (ZMod p) _ _ _ _ _ (_), ZMod.card] at key
exact Nat.pow_right_injective (Nat.Prime.one_lt' p).out key
rw [Set.eq_univ_iff_forall]
suffices ∀ (x) (hx : x ∈ (⊤ : Subalgebra (ZMod p) (GaloisField p n))),
x ∈ (X ^ p ^ n - X : (ZMod p)[X]).rootSet (GaloisField p n)
by simpa
rw [← SplittingField.adjoin_rootSet]
simp_rw [Algebra.mem_adjoin_iff]
intro x hx
-- We discharge the `p = 0` separately, to avoid typeclass issues on `ZMod p`.
cases p; cases hp
refine Subring.closure_induction hx ?_ ?_ ?_ ?_ ?_ ?_ <;> simp_rw [mem_rootSet_of_ne aux]
· rintro x (⟨r, rfl⟩ | hx)
· simp only [g_poly, map_sub, map_pow, aeval_X]
rw [← map_pow, ZMod.pow_card_pow, sub_self]
· dsimp only [GaloisField] at hx
rwa [mem_rootSet_of_ne aux] at hx
· rw [← coeff_zero_eq_aeval_zero']
simp only [g_poly, coeff_X_pow, coeff_X_zero, sub_zero, _root_.map_eq_zero, ite_eq_right_iff,
one_ne_zero, coeff_sub]
intro hn
exact Nat.not_lt_zero 1 (pow_eq_zero hn.symm ▸ hp)
· simp [g_poly]
· simp only [g_poly, aeval_X_pow, aeval_X, AlgHom.map_sub, add_pow_char_pow, sub_eq_zero]
intro x y hx hy
rw [hx, hy]
· intro x hx
simp only [g_poly, sub_eq_zero, aeval_X_pow, aeval_X, AlgHom.map_sub, sub_neg_eq_add] at *
rw [neg_pow, hx, CharP.neg_one_pow_char_pow]
simp
· simp only [g_poly, aeval_X_pow, aeval_X, AlgHom.map_sub, mul_pow, sub_eq_zero]
intro x y hx hy
rw [hx, hy]
| 2,033 |
import Mathlib.FieldTheory.Galois
import Mathlib.Topology.Algebra.FilterBasis
import Mathlib.Topology.Algebra.OpenSubgroup
import Mathlib.Tactic.ByContra
#align_import field_theory.krull_topology from "leanprover-community/mathlib"@"039a089d2a4b93c761b234f3e5f5aeb752bac60f"
open scoped Classical Pointwise
theorem IntermediateField.map_id {K L : Type*} [Field K] [Field L] [Algebra K L]
(E : IntermediateField K L) : E.map (AlgHom.id K L) = E :=
SetLike.coe_injective <| Set.image_id _
#align intermediate_field.map_id IntermediateField.map_id
instance im_finiteDimensional {K L : Type*} [Field K] [Field L] [Algebra K L]
{E : IntermediateField K L} (σ : L ≃ₐ[K] L) [FiniteDimensional K E] :
FiniteDimensional K (E.map σ.toAlgHom) :=
LinearEquiv.finiteDimensional (IntermediateField.intermediateFieldMap σ E).toLinearEquiv
#align im_finite_dimensional im_finiteDimensional
def finiteExts (K : Type*) [Field K] (L : Type*) [Field L] [Algebra K L] :
Set (IntermediateField K L) :=
{E | FiniteDimensional K E}
#align finite_exts finiteExts
def fixedByFinite (K L : Type*) [Field K] [Field L] [Algebra K L] : Set (Subgroup (L ≃ₐ[K] L)) :=
IntermediateField.fixingSubgroup '' finiteExts K L
#align fixed_by_finite fixedByFinite
theorem IntermediateField.finiteDimensional_bot (K L : Type*) [Field K] [Field L] [Algebra K L] :
FiniteDimensional K (⊥ : IntermediateField K L) :=
.of_rank_eq_one IntermediateField.rank_bot
#align intermediate_field.finite_dimensional_bot IntermediateField.finiteDimensional_bot
| Mathlib/FieldTheory/KrullTopology.lean | 93 | 100 | theorem IntermediateField.fixingSubgroup.bot {K L : Type*} [Field K] [Field L] [Algebra K L] :
IntermediateField.fixingSubgroup (⊥ : IntermediateField K L) = ⊤ := by |
ext f
refine ⟨fun _ => Subgroup.mem_top _, fun _ => ?_⟩
rintro ⟨x, hx : x ∈ (⊥ : IntermediateField K L)⟩
rw [IntermediateField.mem_bot] at hx
rcases hx with ⟨y, rfl⟩
exact f.commutes y
| 2,034 |
import Mathlib.FieldTheory.Galois
import Mathlib.Topology.Algebra.FilterBasis
import Mathlib.Topology.Algebra.OpenSubgroup
import Mathlib.Tactic.ByContra
#align_import field_theory.krull_topology from "leanprover-community/mathlib"@"039a089d2a4b93c761b234f3e5f5aeb752bac60f"
open scoped Classical Pointwise
theorem IntermediateField.map_id {K L : Type*} [Field K] [Field L] [Algebra K L]
(E : IntermediateField K L) : E.map (AlgHom.id K L) = E :=
SetLike.coe_injective <| Set.image_id _
#align intermediate_field.map_id IntermediateField.map_id
instance im_finiteDimensional {K L : Type*} [Field K] [Field L] [Algebra K L]
{E : IntermediateField K L} (σ : L ≃ₐ[K] L) [FiniteDimensional K E] :
FiniteDimensional K (E.map σ.toAlgHom) :=
LinearEquiv.finiteDimensional (IntermediateField.intermediateFieldMap σ E).toLinearEquiv
#align im_finite_dimensional im_finiteDimensional
def finiteExts (K : Type*) [Field K] (L : Type*) [Field L] [Algebra K L] :
Set (IntermediateField K L) :=
{E | FiniteDimensional K E}
#align finite_exts finiteExts
def fixedByFinite (K L : Type*) [Field K] [Field L] [Algebra K L] : Set (Subgroup (L ≃ₐ[K] L)) :=
IntermediateField.fixingSubgroup '' finiteExts K L
#align fixed_by_finite fixedByFinite
theorem IntermediateField.finiteDimensional_bot (K L : Type*) [Field K] [Field L] [Algebra K L] :
FiniteDimensional K (⊥ : IntermediateField K L) :=
.of_rank_eq_one IntermediateField.rank_bot
#align intermediate_field.finite_dimensional_bot IntermediateField.finiteDimensional_bot
theorem IntermediateField.fixingSubgroup.bot {K L : Type*} [Field K] [Field L] [Algebra K L] :
IntermediateField.fixingSubgroup (⊥ : IntermediateField K L) = ⊤ := by
ext f
refine ⟨fun _ => Subgroup.mem_top _, fun _ => ?_⟩
rintro ⟨x, hx : x ∈ (⊥ : IntermediateField K L)⟩
rw [IntermediateField.mem_bot] at hx
rcases hx with ⟨y, rfl⟩
exact f.commutes y
#align intermediate_field.fixing_subgroup.bot IntermediateField.fixingSubgroup.bot
theorem top_fixedByFinite {K L : Type*} [Field K] [Field L] [Algebra K L] :
⊤ ∈ fixedByFinite K L :=
⟨⊥, IntermediateField.finiteDimensional_bot K L, IntermediateField.fixingSubgroup.bot⟩
#align top_fixed_by_finite top_fixedByFinite
theorem finiteDimensional_sup {K L : Type*} [Field K] [Field L] [Algebra K L]
(E1 E2 : IntermediateField K L) (_ : FiniteDimensional K E1) (_ : FiniteDimensional K E2) :
FiniteDimensional K (↥(E1 ⊔ E2)) :=
IntermediateField.finiteDimensional_sup E1 E2
#align finite_dimensional_sup finiteDimensional_sup
theorem IntermediateField.mem_fixingSubgroup_iff {K L : Type*} [Field K] [Field L] [Algebra K L]
(E : IntermediateField K L) (σ : L ≃ₐ[K] L) : σ ∈ E.fixingSubgroup ↔ ∀ x : L, x ∈ E → σ x = x :=
⟨fun hσ x hx => hσ ⟨x, hx⟩, fun h ⟨x, hx⟩ => h x hx⟩
#align intermediate_field.mem_fixing_subgroup_iff IntermediateField.mem_fixingSubgroup_iff
| Mathlib/FieldTheory/KrullTopology.lean | 124 | 127 | theorem IntermediateField.fixingSubgroup.antimono {K L : Type*} [Field K] [Field L] [Algebra K L]
{E1 E2 : IntermediateField K L} (h12 : E1 ≤ E2) : E2.fixingSubgroup ≤ E1.fixingSubgroup := by |
rintro σ hσ ⟨x, hx⟩
exact hσ ⟨x, h12 hx⟩
| 2,034 |
import Mathlib.FieldTheory.Galois
#align_import field_theory.polynomial_galois_group from "leanprover-community/mathlib"@"e3f4be1fcb5376c4948d7f095bec45350bfb9d1a"
noncomputable section
open scoped Polynomial
open FiniteDimensional
namespace Polynomial
variable {F : Type*} [Field F] (p q : F[X]) (E : Type*) [Field E] [Algebra F E]
def Gal :=
p.SplittingField ≃ₐ[F] p.SplittingField
-- Porting note(https://github.com/leanprover-community/mathlib4/issues/5020):
-- deriving Group, Fintype
#align polynomial.gal Polynomial.Gal
namespace Gal
instance instGroup : Group (Gal p) :=
inferInstanceAs (Group (p.SplittingField ≃ₐ[F] p.SplittingField))
instance instFintype : Fintype (Gal p) :=
inferInstanceAs (Fintype (p.SplittingField ≃ₐ[F] p.SplittingField))
instance : CoeFun p.Gal fun _ => p.SplittingField → p.SplittingField :=
-- Porting note: was AlgEquiv.hasCoeToFun
inferInstanceAs (CoeFun (p.SplittingField ≃ₐ[F] p.SplittingField) _)
instance applyMulSemiringAction : MulSemiringAction p.Gal p.SplittingField :=
AlgEquiv.applyMulSemiringAction
#align polynomial.gal.apply_mul_semiring_action Polynomial.Gal.applyMulSemiringAction
@[ext]
| Mathlib/FieldTheory/PolynomialGaloisGroup.lean | 74 | 79 | theorem ext {σ τ : p.Gal} (h : ∀ x ∈ p.rootSet p.SplittingField, σ x = τ x) : σ = τ := by |
refine
AlgEquiv.ext fun x =>
(AlgHom.mem_equalizer σ.toAlgHom τ.toAlgHom x).mp
((SetLike.ext_iff.mp ?_ x).mpr Algebra.mem_top)
rwa [eq_top_iff, ← SplittingField.adjoin_rootSet, Algebra.adjoin_le_iff]
| 2,035 |
import Mathlib.FieldTheory.Galois
#align_import field_theory.polynomial_galois_group from "leanprover-community/mathlib"@"e3f4be1fcb5376c4948d7f095bec45350bfb9d1a"
noncomputable section
open scoped Polynomial
open FiniteDimensional
namespace Polynomial
variable {F : Type*} [Field F] (p q : F[X]) (E : Type*) [Field E] [Algebra F E]
def Gal :=
p.SplittingField ≃ₐ[F] p.SplittingField
-- Porting note(https://github.com/leanprover-community/mathlib4/issues/5020):
-- deriving Group, Fintype
#align polynomial.gal Polynomial.Gal
namespace Gal
instance instGroup : Group (Gal p) :=
inferInstanceAs (Group (p.SplittingField ≃ₐ[F] p.SplittingField))
instance instFintype : Fintype (Gal p) :=
inferInstanceAs (Fintype (p.SplittingField ≃ₐ[F] p.SplittingField))
instance : CoeFun p.Gal fun _ => p.SplittingField → p.SplittingField :=
-- Porting note: was AlgEquiv.hasCoeToFun
inferInstanceAs (CoeFun (p.SplittingField ≃ₐ[F] p.SplittingField) _)
instance applyMulSemiringAction : MulSemiringAction p.Gal p.SplittingField :=
AlgEquiv.applyMulSemiringAction
#align polynomial.gal.apply_mul_semiring_action Polynomial.Gal.applyMulSemiringAction
@[ext]
theorem ext {σ τ : p.Gal} (h : ∀ x ∈ p.rootSet p.SplittingField, σ x = τ x) : σ = τ := by
refine
AlgEquiv.ext fun x =>
(AlgHom.mem_equalizer σ.toAlgHom τ.toAlgHom x).mp
((SetLike.ext_iff.mp ?_ x).mpr Algebra.mem_top)
rwa [eq_top_iff, ← SplittingField.adjoin_rootSet, Algebra.adjoin_le_iff]
#align polynomial.gal.ext Polynomial.Gal.ext
def uniqueGalOfSplits (h : p.Splits (RingHom.id F)) : Unique p.Gal where
default := 1
uniq f :=
AlgEquiv.ext fun x => by
obtain ⟨y, rfl⟩ :=
Algebra.mem_bot.mp
((SetLike.ext_iff.mp ((IsSplittingField.splits_iff _ p).mp h) x).mp Algebra.mem_top)
rw [AlgEquiv.commutes, AlgEquiv.commutes]
#align polynomial.gal.unique_gal_of_splits Polynomial.Gal.uniqueGalOfSplits
instance [h : Fact (p.Splits (RingHom.id F))] : Unique p.Gal :=
uniqueGalOfSplits _ h.1
instance uniqueGalZero : Unique (0 : F[X]).Gal :=
uniqueGalOfSplits _ (splits_zero _)
#align polynomial.gal.unique_gal_zero Polynomial.Gal.uniqueGalZero
instance uniqueGalOne : Unique (1 : F[X]).Gal :=
uniqueGalOfSplits _ (splits_one _)
#align polynomial.gal.unique_gal_one Polynomial.Gal.uniqueGalOne
instance uniqueGalC (x : F) : Unique (C x).Gal :=
uniqueGalOfSplits _ (splits_C _ _)
set_option linter.uppercaseLean3 false in
#align polynomial.gal.unique_gal_C Polynomial.Gal.uniqueGalC
instance uniqueGalX : Unique (X : F[X]).Gal :=
uniqueGalOfSplits _ (splits_X _)
set_option linter.uppercaseLean3 false in
#align polynomial.gal.unique_gal_X Polynomial.Gal.uniqueGalX
instance uniqueGalXSubC (x : F) : Unique (X - C x).Gal :=
uniqueGalOfSplits _ (splits_X_sub_C _)
set_option linter.uppercaseLean3 false in
#align polynomial.gal.unique_gal_X_sub_C Polynomial.Gal.uniqueGalXSubC
instance uniqueGalXPow (n : ℕ) : Unique (X ^ n : F[X]).Gal :=
uniqueGalOfSplits _ (splits_X_pow _ _)
set_option linter.uppercaseLean3 false in
#align polynomial.gal.unique_gal_X_pow Polynomial.Gal.uniqueGalXPow
instance [h : Fact (p.Splits (algebraMap F E))] : Algebra p.SplittingField E :=
(IsSplittingField.lift p.SplittingField p h.1).toRingHom.toAlgebra
instance [h : Fact (p.Splits (algebraMap F E))] : IsScalarTower F p.SplittingField E :=
IsScalarTower.of_algebraMap_eq fun x =>
((IsSplittingField.lift p.SplittingField p h.1).commutes x).symm
-- The `Algebra p.SplittingField E` instance above behaves badly when
-- `E := p.SplittingField`, since it may result in a unification problem
-- `IsSplittingField.lift.toRingHom.toAlgebra =?= Algebra.id`,
-- which takes an extremely long time to resolve, causing timeouts.
-- Since we don't really care about this definition, marking it as irreducible
-- causes that unification to error out early.
def restrict [Fact (p.Splits (algebraMap F E))] : (E ≃ₐ[F] E) →* p.Gal :=
AlgEquiv.restrictNormalHom p.SplittingField
#align polynomial.gal.restrict Polynomial.Gal.restrict
theorem restrict_surjective [Fact (p.Splits (algebraMap F E))] [Normal F E] :
Function.Surjective (restrict p E) :=
AlgEquiv.restrictNormalHom_surjective E
#align polynomial.gal.restrict_surjective Polynomial.Gal.restrict_surjective
section RootsAction
def mapRoots [Fact (p.Splits (algebraMap F E))] : rootSet p p.SplittingField → rootSet p E :=
Set.MapsTo.restrict (IsScalarTower.toAlgHom F p.SplittingField E) _ _ <| rootSet_mapsTo _
#align polynomial.gal.map_roots Polynomial.Gal.mapRoots
| Mathlib/FieldTheory/PolynomialGaloisGroup.lean | 155 | 168 | theorem mapRoots_bijective [h : Fact (p.Splits (algebraMap F E))] :
Function.Bijective (mapRoots p E) := by |
constructor
· exact fun _ _ h => Subtype.ext (RingHom.injective _ (Subtype.ext_iff.mp h))
· intro y
-- this is just an equality of two different ways to write the roots of `p` as an `E`-polynomial
have key :=
roots_map (IsScalarTower.toAlgHom F p.SplittingField E : p.SplittingField →+* E)
((splits_id_iff_splits _).mpr (IsSplittingField.splits p.SplittingField p))
rw [map_map, AlgHom.comp_algebraMap] at key
have hy := Subtype.mem y
simp only [rootSet, Finset.mem_coe, Multiset.mem_toFinset, key, Multiset.mem_map] at hy
rcases hy with ⟨x, hx1, hx2⟩
exact ⟨⟨x, (@Multiset.mem_toFinset _ (Classical.decEq _) _ _).mpr hx1⟩, Subtype.ext hx2⟩
| 2,035 |
import Mathlib.FieldTheory.Galois
#align_import field_theory.polynomial_galois_group from "leanprover-community/mathlib"@"e3f4be1fcb5376c4948d7f095bec45350bfb9d1a"
noncomputable section
open scoped Polynomial
open FiniteDimensional
namespace Polynomial
variable {F : Type*} [Field F] (p q : F[X]) (E : Type*) [Field E] [Algebra F E]
def Gal :=
p.SplittingField ≃ₐ[F] p.SplittingField
-- Porting note(https://github.com/leanprover-community/mathlib4/issues/5020):
-- deriving Group, Fintype
#align polynomial.gal Polynomial.Gal
namespace Gal
instance instGroup : Group (Gal p) :=
inferInstanceAs (Group (p.SplittingField ≃ₐ[F] p.SplittingField))
instance instFintype : Fintype (Gal p) :=
inferInstanceAs (Fintype (p.SplittingField ≃ₐ[F] p.SplittingField))
instance : CoeFun p.Gal fun _ => p.SplittingField → p.SplittingField :=
-- Porting note: was AlgEquiv.hasCoeToFun
inferInstanceAs (CoeFun (p.SplittingField ≃ₐ[F] p.SplittingField) _)
instance applyMulSemiringAction : MulSemiringAction p.Gal p.SplittingField :=
AlgEquiv.applyMulSemiringAction
#align polynomial.gal.apply_mul_semiring_action Polynomial.Gal.applyMulSemiringAction
@[ext]
theorem ext {σ τ : p.Gal} (h : ∀ x ∈ p.rootSet p.SplittingField, σ x = τ x) : σ = τ := by
refine
AlgEquiv.ext fun x =>
(AlgHom.mem_equalizer σ.toAlgHom τ.toAlgHom x).mp
((SetLike.ext_iff.mp ?_ x).mpr Algebra.mem_top)
rwa [eq_top_iff, ← SplittingField.adjoin_rootSet, Algebra.adjoin_le_iff]
#align polynomial.gal.ext Polynomial.Gal.ext
def uniqueGalOfSplits (h : p.Splits (RingHom.id F)) : Unique p.Gal where
default := 1
uniq f :=
AlgEquiv.ext fun x => by
obtain ⟨y, rfl⟩ :=
Algebra.mem_bot.mp
((SetLike.ext_iff.mp ((IsSplittingField.splits_iff _ p).mp h) x).mp Algebra.mem_top)
rw [AlgEquiv.commutes, AlgEquiv.commutes]
#align polynomial.gal.unique_gal_of_splits Polynomial.Gal.uniqueGalOfSplits
instance [h : Fact (p.Splits (RingHom.id F))] : Unique p.Gal :=
uniqueGalOfSplits _ h.1
instance uniqueGalZero : Unique (0 : F[X]).Gal :=
uniqueGalOfSplits _ (splits_zero _)
#align polynomial.gal.unique_gal_zero Polynomial.Gal.uniqueGalZero
instance uniqueGalOne : Unique (1 : F[X]).Gal :=
uniqueGalOfSplits _ (splits_one _)
#align polynomial.gal.unique_gal_one Polynomial.Gal.uniqueGalOne
instance uniqueGalC (x : F) : Unique (C x).Gal :=
uniqueGalOfSplits _ (splits_C _ _)
set_option linter.uppercaseLean3 false in
#align polynomial.gal.unique_gal_C Polynomial.Gal.uniqueGalC
instance uniqueGalX : Unique (X : F[X]).Gal :=
uniqueGalOfSplits _ (splits_X _)
set_option linter.uppercaseLean3 false in
#align polynomial.gal.unique_gal_X Polynomial.Gal.uniqueGalX
instance uniqueGalXSubC (x : F) : Unique (X - C x).Gal :=
uniqueGalOfSplits _ (splits_X_sub_C _)
set_option linter.uppercaseLean3 false in
#align polynomial.gal.unique_gal_X_sub_C Polynomial.Gal.uniqueGalXSubC
instance uniqueGalXPow (n : ℕ) : Unique (X ^ n : F[X]).Gal :=
uniqueGalOfSplits _ (splits_X_pow _ _)
set_option linter.uppercaseLean3 false in
#align polynomial.gal.unique_gal_X_pow Polynomial.Gal.uniqueGalXPow
instance [h : Fact (p.Splits (algebraMap F E))] : Algebra p.SplittingField E :=
(IsSplittingField.lift p.SplittingField p h.1).toRingHom.toAlgebra
instance [h : Fact (p.Splits (algebraMap F E))] : IsScalarTower F p.SplittingField E :=
IsScalarTower.of_algebraMap_eq fun x =>
((IsSplittingField.lift p.SplittingField p h.1).commutes x).symm
-- The `Algebra p.SplittingField E` instance above behaves badly when
-- `E := p.SplittingField`, since it may result in a unification problem
-- `IsSplittingField.lift.toRingHom.toAlgebra =?= Algebra.id`,
-- which takes an extremely long time to resolve, causing timeouts.
-- Since we don't really care about this definition, marking it as irreducible
-- causes that unification to error out early.
def restrict [Fact (p.Splits (algebraMap F E))] : (E ≃ₐ[F] E) →* p.Gal :=
AlgEquiv.restrictNormalHom p.SplittingField
#align polynomial.gal.restrict Polynomial.Gal.restrict
theorem restrict_surjective [Fact (p.Splits (algebraMap F E))] [Normal F E] :
Function.Surjective (restrict p E) :=
AlgEquiv.restrictNormalHom_surjective E
#align polynomial.gal.restrict_surjective Polynomial.Gal.restrict_surjective
variable {p q}
def restrictDvd (hpq : p ∣ q) : q.Gal →* p.Gal :=
haveI := Classical.dec (q = 0)
if hq : q = 0 then 1
else
@restrict F _ p _ _ _
⟨splits_of_splits_of_dvd (algebraMap F q.SplittingField) hq (SplittingField.splits q) hpq⟩
#align polynomial.gal.restrict_dvd Polynomial.Gal.restrictDvd
| Mathlib/FieldTheory/PolynomialGaloisGroup.lean | 259 | 268 | theorem restrictDvd_def [Decidable (q = 0)] (hpq : p ∣ q) :
restrictDvd hpq =
if hq : q = 0 then 1
else
@restrict F _ p _ _ _
⟨splits_of_splits_of_dvd (algebraMap F q.SplittingField) hq (SplittingField.splits q)
hpq⟩ := by |
-- Porting note: added `unfold`
unfold restrictDvd
convert rfl
| 2,035 |
import Mathlib.FieldTheory.Galois
#align_import field_theory.polynomial_galois_group from "leanprover-community/mathlib"@"e3f4be1fcb5376c4948d7f095bec45350bfb9d1a"
noncomputable section
open scoped Polynomial
open FiniteDimensional
namespace Polynomial
variable {F : Type*} [Field F] (p q : F[X]) (E : Type*) [Field E] [Algebra F E]
def Gal :=
p.SplittingField ≃ₐ[F] p.SplittingField
-- Porting note(https://github.com/leanprover-community/mathlib4/issues/5020):
-- deriving Group, Fintype
#align polynomial.gal Polynomial.Gal
namespace Gal
instance instGroup : Group (Gal p) :=
inferInstanceAs (Group (p.SplittingField ≃ₐ[F] p.SplittingField))
instance instFintype : Fintype (Gal p) :=
inferInstanceAs (Fintype (p.SplittingField ≃ₐ[F] p.SplittingField))
instance : CoeFun p.Gal fun _ => p.SplittingField → p.SplittingField :=
-- Porting note: was AlgEquiv.hasCoeToFun
inferInstanceAs (CoeFun (p.SplittingField ≃ₐ[F] p.SplittingField) _)
instance applyMulSemiringAction : MulSemiringAction p.Gal p.SplittingField :=
AlgEquiv.applyMulSemiringAction
#align polynomial.gal.apply_mul_semiring_action Polynomial.Gal.applyMulSemiringAction
@[ext]
theorem ext {σ τ : p.Gal} (h : ∀ x ∈ p.rootSet p.SplittingField, σ x = τ x) : σ = τ := by
refine
AlgEquiv.ext fun x =>
(AlgHom.mem_equalizer σ.toAlgHom τ.toAlgHom x).mp
((SetLike.ext_iff.mp ?_ x).mpr Algebra.mem_top)
rwa [eq_top_iff, ← SplittingField.adjoin_rootSet, Algebra.adjoin_le_iff]
#align polynomial.gal.ext Polynomial.Gal.ext
def uniqueGalOfSplits (h : p.Splits (RingHom.id F)) : Unique p.Gal where
default := 1
uniq f :=
AlgEquiv.ext fun x => by
obtain ⟨y, rfl⟩ :=
Algebra.mem_bot.mp
((SetLike.ext_iff.mp ((IsSplittingField.splits_iff _ p).mp h) x).mp Algebra.mem_top)
rw [AlgEquiv.commutes, AlgEquiv.commutes]
#align polynomial.gal.unique_gal_of_splits Polynomial.Gal.uniqueGalOfSplits
instance [h : Fact (p.Splits (RingHom.id F))] : Unique p.Gal :=
uniqueGalOfSplits _ h.1
instance uniqueGalZero : Unique (0 : F[X]).Gal :=
uniqueGalOfSplits _ (splits_zero _)
#align polynomial.gal.unique_gal_zero Polynomial.Gal.uniqueGalZero
instance uniqueGalOne : Unique (1 : F[X]).Gal :=
uniqueGalOfSplits _ (splits_one _)
#align polynomial.gal.unique_gal_one Polynomial.Gal.uniqueGalOne
instance uniqueGalC (x : F) : Unique (C x).Gal :=
uniqueGalOfSplits _ (splits_C _ _)
set_option linter.uppercaseLean3 false in
#align polynomial.gal.unique_gal_C Polynomial.Gal.uniqueGalC
instance uniqueGalX : Unique (X : F[X]).Gal :=
uniqueGalOfSplits _ (splits_X _)
set_option linter.uppercaseLean3 false in
#align polynomial.gal.unique_gal_X Polynomial.Gal.uniqueGalX
instance uniqueGalXSubC (x : F) : Unique (X - C x).Gal :=
uniqueGalOfSplits _ (splits_X_sub_C _)
set_option linter.uppercaseLean3 false in
#align polynomial.gal.unique_gal_X_sub_C Polynomial.Gal.uniqueGalXSubC
instance uniqueGalXPow (n : ℕ) : Unique (X ^ n : F[X]).Gal :=
uniqueGalOfSplits _ (splits_X_pow _ _)
set_option linter.uppercaseLean3 false in
#align polynomial.gal.unique_gal_X_pow Polynomial.Gal.uniqueGalXPow
instance [h : Fact (p.Splits (algebraMap F E))] : Algebra p.SplittingField E :=
(IsSplittingField.lift p.SplittingField p h.1).toRingHom.toAlgebra
instance [h : Fact (p.Splits (algebraMap F E))] : IsScalarTower F p.SplittingField E :=
IsScalarTower.of_algebraMap_eq fun x =>
((IsSplittingField.lift p.SplittingField p h.1).commutes x).symm
-- The `Algebra p.SplittingField E` instance above behaves badly when
-- `E := p.SplittingField`, since it may result in a unification problem
-- `IsSplittingField.lift.toRingHom.toAlgebra =?= Algebra.id`,
-- which takes an extremely long time to resolve, causing timeouts.
-- Since we don't really care about this definition, marking it as irreducible
-- causes that unification to error out early.
def restrict [Fact (p.Splits (algebraMap F E))] : (E ≃ₐ[F] E) →* p.Gal :=
AlgEquiv.restrictNormalHom p.SplittingField
#align polynomial.gal.restrict Polynomial.Gal.restrict
theorem restrict_surjective [Fact (p.Splits (algebraMap F E))] [Normal F E] :
Function.Surjective (restrict p E) :=
AlgEquiv.restrictNormalHom_surjective E
#align polynomial.gal.restrict_surjective Polynomial.Gal.restrict_surjective
variable {p q}
def restrictDvd (hpq : p ∣ q) : q.Gal →* p.Gal :=
haveI := Classical.dec (q = 0)
if hq : q = 0 then 1
else
@restrict F _ p _ _ _
⟨splits_of_splits_of_dvd (algebraMap F q.SplittingField) hq (SplittingField.splits q) hpq⟩
#align polynomial.gal.restrict_dvd Polynomial.Gal.restrictDvd
theorem restrictDvd_def [Decidable (q = 0)] (hpq : p ∣ q) :
restrictDvd hpq =
if hq : q = 0 then 1
else
@restrict F _ p _ _ _
⟨splits_of_splits_of_dvd (algebraMap F q.SplittingField) hq (SplittingField.splits q)
hpq⟩ := by
-- Porting note: added `unfold`
unfold restrictDvd
convert rfl
#align polynomial.gal.restrict_dvd_def Polynomial.Gal.restrictDvd_def
| Mathlib/FieldTheory/PolynomialGaloisGroup.lean | 271 | 278 | theorem restrictDvd_surjective (hpq : p ∣ q) (hq : q ≠ 0) :
Function.Surjective (restrictDvd hpq) := by |
classical
-- Porting note: was `simp only [restrictDvd_def, dif_neg hq, restrict_surjective]`
haveI := Fact.mk <|
splits_of_splits_of_dvd (algebraMap F q.SplittingField) hq (SplittingField.splits q) hpq
simp only [restrictDvd_def, dif_neg hq]
exact restrict_surjective _ _
| 2,035 |
import Mathlib.GroupTheory.Solvable
import Mathlib.FieldTheory.PolynomialGaloisGroup
import Mathlib.RingTheory.RootsOfUnity.Basic
#align_import field_theory.abel_ruffini from "leanprover-community/mathlib"@"e3f4be1fcb5376c4948d7f095bec45350bfb9d1a"
noncomputable section
open scoped Classical Polynomial IntermediateField
open Polynomial IntermediateField
section AbelRuffini
variable {F : Type*} [Field F] {E : Type*} [Field E] [Algebra F E]
| Mathlib/FieldTheory/AbelRuffini.lean | 39 | 39 | theorem gal_zero_isSolvable : IsSolvable (0 : F[X]).Gal := by | infer_instance
| 2,036 |
import Mathlib.GroupTheory.Solvable
import Mathlib.FieldTheory.PolynomialGaloisGroup
import Mathlib.RingTheory.RootsOfUnity.Basic
#align_import field_theory.abel_ruffini from "leanprover-community/mathlib"@"e3f4be1fcb5376c4948d7f095bec45350bfb9d1a"
noncomputable section
open scoped Classical Polynomial IntermediateField
open Polynomial IntermediateField
section AbelRuffini
variable {F : Type*} [Field F] {E : Type*} [Field E] [Algebra F E]
theorem gal_zero_isSolvable : IsSolvable (0 : F[X]).Gal := by infer_instance
#align gal_zero_is_solvable gal_zero_isSolvable
| Mathlib/FieldTheory/AbelRuffini.lean | 42 | 42 | theorem gal_one_isSolvable : IsSolvable (1 : F[X]).Gal := by | infer_instance
| 2,036 |
import Mathlib.GroupTheory.Solvable
import Mathlib.FieldTheory.PolynomialGaloisGroup
import Mathlib.RingTheory.RootsOfUnity.Basic
#align_import field_theory.abel_ruffini from "leanprover-community/mathlib"@"e3f4be1fcb5376c4948d7f095bec45350bfb9d1a"
noncomputable section
open scoped Classical Polynomial IntermediateField
open Polynomial IntermediateField
section AbelRuffini
variable {F : Type*} [Field F] {E : Type*} [Field E] [Algebra F E]
theorem gal_zero_isSolvable : IsSolvable (0 : F[X]).Gal := by infer_instance
#align gal_zero_is_solvable gal_zero_isSolvable
theorem gal_one_isSolvable : IsSolvable (1 : F[X]).Gal := by infer_instance
#align gal_one_is_solvable gal_one_isSolvable
| Mathlib/FieldTheory/AbelRuffini.lean | 45 | 45 | theorem gal_C_isSolvable (x : F) : IsSolvable (C x).Gal := by | infer_instance
| 2,036 |
import Mathlib.GroupTheory.Solvable
import Mathlib.FieldTheory.PolynomialGaloisGroup
import Mathlib.RingTheory.RootsOfUnity.Basic
#align_import field_theory.abel_ruffini from "leanprover-community/mathlib"@"e3f4be1fcb5376c4948d7f095bec45350bfb9d1a"
noncomputable section
open scoped Classical Polynomial IntermediateField
open Polynomial IntermediateField
section AbelRuffini
variable {F : Type*} [Field F] {E : Type*} [Field E] [Algebra F E]
theorem gal_zero_isSolvable : IsSolvable (0 : F[X]).Gal := by infer_instance
#align gal_zero_is_solvable gal_zero_isSolvable
theorem gal_one_isSolvable : IsSolvable (1 : F[X]).Gal := by infer_instance
#align gal_one_is_solvable gal_one_isSolvable
theorem gal_C_isSolvable (x : F) : IsSolvable (C x).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_C_is_solvable gal_C_isSolvable
| Mathlib/FieldTheory/AbelRuffini.lean | 49 | 49 | theorem gal_X_isSolvable : IsSolvable (X : F[X]).Gal := by | infer_instance
| 2,036 |
import Mathlib.GroupTheory.Solvable
import Mathlib.FieldTheory.PolynomialGaloisGroup
import Mathlib.RingTheory.RootsOfUnity.Basic
#align_import field_theory.abel_ruffini from "leanprover-community/mathlib"@"e3f4be1fcb5376c4948d7f095bec45350bfb9d1a"
noncomputable section
open scoped Classical Polynomial IntermediateField
open Polynomial IntermediateField
section AbelRuffini
variable {F : Type*} [Field F] {E : Type*} [Field E] [Algebra F E]
theorem gal_zero_isSolvable : IsSolvable (0 : F[X]).Gal := by infer_instance
#align gal_zero_is_solvable gal_zero_isSolvable
theorem gal_one_isSolvable : IsSolvable (1 : F[X]).Gal := by infer_instance
#align gal_one_is_solvable gal_one_isSolvable
theorem gal_C_isSolvable (x : F) : IsSolvable (C x).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_C_is_solvable gal_C_isSolvable
theorem gal_X_isSolvable : IsSolvable (X : F[X]).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_is_solvable gal_X_isSolvable
| Mathlib/FieldTheory/AbelRuffini.lean | 53 | 53 | theorem gal_X_sub_C_isSolvable (x : F) : IsSolvable (X - C x).Gal := by | infer_instance
| 2,036 |
import Mathlib.GroupTheory.Solvable
import Mathlib.FieldTheory.PolynomialGaloisGroup
import Mathlib.RingTheory.RootsOfUnity.Basic
#align_import field_theory.abel_ruffini from "leanprover-community/mathlib"@"e3f4be1fcb5376c4948d7f095bec45350bfb9d1a"
noncomputable section
open scoped Classical Polynomial IntermediateField
open Polynomial IntermediateField
section AbelRuffini
variable {F : Type*} [Field F] {E : Type*} [Field E] [Algebra F E]
theorem gal_zero_isSolvable : IsSolvable (0 : F[X]).Gal := by infer_instance
#align gal_zero_is_solvable gal_zero_isSolvable
theorem gal_one_isSolvable : IsSolvable (1 : F[X]).Gal := by infer_instance
#align gal_one_is_solvable gal_one_isSolvable
theorem gal_C_isSolvable (x : F) : IsSolvable (C x).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_C_is_solvable gal_C_isSolvable
theorem gal_X_isSolvable : IsSolvable (X : F[X]).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_is_solvable gal_X_isSolvable
theorem gal_X_sub_C_isSolvable (x : F) : IsSolvable (X - C x).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_sub_C_is_solvable gal_X_sub_C_isSolvable
| Mathlib/FieldTheory/AbelRuffini.lean | 57 | 57 | theorem gal_X_pow_isSolvable (n : ℕ) : IsSolvable (X ^ n : F[X]).Gal := by | infer_instance
| 2,036 |
import Mathlib.GroupTheory.Solvable
import Mathlib.FieldTheory.PolynomialGaloisGroup
import Mathlib.RingTheory.RootsOfUnity.Basic
#align_import field_theory.abel_ruffini from "leanprover-community/mathlib"@"e3f4be1fcb5376c4948d7f095bec45350bfb9d1a"
noncomputable section
open scoped Classical Polynomial IntermediateField
open Polynomial IntermediateField
section AbelRuffini
variable {F : Type*} [Field F] {E : Type*} [Field E] [Algebra F E]
theorem gal_zero_isSolvable : IsSolvable (0 : F[X]).Gal := by infer_instance
#align gal_zero_is_solvable gal_zero_isSolvable
theorem gal_one_isSolvable : IsSolvable (1 : F[X]).Gal := by infer_instance
#align gal_one_is_solvable gal_one_isSolvable
theorem gal_C_isSolvable (x : F) : IsSolvable (C x).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_C_is_solvable gal_C_isSolvable
theorem gal_X_isSolvable : IsSolvable (X : F[X]).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_is_solvable gal_X_isSolvable
theorem gal_X_sub_C_isSolvable (x : F) : IsSolvable (X - C x).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_sub_C_is_solvable gal_X_sub_C_isSolvable
theorem gal_X_pow_isSolvable (n : ℕ) : IsSolvable (X ^ n : F[X]).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_pow_is_solvable gal_X_pow_isSolvable
theorem gal_mul_isSolvable {p q : F[X]} (_ : IsSolvable p.Gal) (_ : IsSolvable q.Gal) :
IsSolvable (p * q).Gal :=
solvable_of_solvable_injective (Gal.restrictProd_injective p q)
#align gal_mul_is_solvable gal_mul_isSolvable
| Mathlib/FieldTheory/AbelRuffini.lean | 66 | 72 | theorem gal_prod_isSolvable {s : Multiset F[X]} (hs : ∀ p ∈ s, IsSolvable (Gal p)) :
IsSolvable s.prod.Gal := by |
apply Multiset.induction_on' s
· exact gal_one_isSolvable
· intro p t hps _ ht
rw [Multiset.insert_eq_cons, Multiset.prod_cons]
exact gal_mul_isSolvable (hs p hps) ht
| 2,036 |
import Mathlib.GroupTheory.Solvable
import Mathlib.FieldTheory.PolynomialGaloisGroup
import Mathlib.RingTheory.RootsOfUnity.Basic
#align_import field_theory.abel_ruffini from "leanprover-community/mathlib"@"e3f4be1fcb5376c4948d7f095bec45350bfb9d1a"
noncomputable section
open scoped Classical Polynomial IntermediateField
open Polynomial IntermediateField
section AbelRuffini
variable {F : Type*} [Field F] {E : Type*} [Field E] [Algebra F E]
theorem gal_zero_isSolvable : IsSolvable (0 : F[X]).Gal := by infer_instance
#align gal_zero_is_solvable gal_zero_isSolvable
theorem gal_one_isSolvable : IsSolvable (1 : F[X]).Gal := by infer_instance
#align gal_one_is_solvable gal_one_isSolvable
theorem gal_C_isSolvable (x : F) : IsSolvable (C x).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_C_is_solvable gal_C_isSolvable
theorem gal_X_isSolvable : IsSolvable (X : F[X]).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_is_solvable gal_X_isSolvable
theorem gal_X_sub_C_isSolvable (x : F) : IsSolvable (X - C x).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_sub_C_is_solvable gal_X_sub_C_isSolvable
theorem gal_X_pow_isSolvable (n : ℕ) : IsSolvable (X ^ n : F[X]).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_pow_is_solvable gal_X_pow_isSolvable
theorem gal_mul_isSolvable {p q : F[X]} (_ : IsSolvable p.Gal) (_ : IsSolvable q.Gal) :
IsSolvable (p * q).Gal :=
solvable_of_solvable_injective (Gal.restrictProd_injective p q)
#align gal_mul_is_solvable gal_mul_isSolvable
theorem gal_prod_isSolvable {s : Multiset F[X]} (hs : ∀ p ∈ s, IsSolvable (Gal p)) :
IsSolvable s.prod.Gal := by
apply Multiset.induction_on' s
· exact gal_one_isSolvable
· intro p t hps _ ht
rw [Multiset.insert_eq_cons, Multiset.prod_cons]
exact gal_mul_isSolvable (hs p hps) ht
#align gal_prod_is_solvable gal_prod_isSolvable
theorem gal_isSolvable_of_splits {p q : F[X]}
(_ : Fact (p.Splits (algebraMap F q.SplittingField))) (hq : IsSolvable q.Gal) :
IsSolvable p.Gal :=
haveI : IsSolvable (q.SplittingField ≃ₐ[F] q.SplittingField) := hq
solvable_of_surjective (AlgEquiv.restrictNormalHom_surjective q.SplittingField)
#align gal_is_solvable_of_splits gal_isSolvable_of_splits
| Mathlib/FieldTheory/AbelRuffini.lean | 82 | 93 | theorem gal_isSolvable_tower (p q : F[X]) (hpq : p.Splits (algebraMap F q.SplittingField))
(hp : IsSolvable p.Gal) (hq : IsSolvable (q.map (algebraMap F p.SplittingField)).Gal) :
IsSolvable q.Gal := by |
let K := p.SplittingField
let L := q.SplittingField
haveI : Fact (p.Splits (algebraMap F L)) := ⟨hpq⟩
let ϕ : (L ≃ₐ[K] L) ≃* (q.map (algebraMap F K)).Gal :=
(IsSplittingField.algEquiv L (q.map (algebraMap F K))).autCongr
have ϕ_inj : Function.Injective ϕ.toMonoidHom := ϕ.injective
haveI : IsSolvable (K ≃ₐ[F] K) := hp
haveI : IsSolvable (L ≃ₐ[K] L) := solvable_of_solvable_injective ϕ_inj
exact isSolvable_of_isScalarTower F p.SplittingField q.SplittingField
| 2,036 |
import Mathlib.GroupTheory.Solvable
import Mathlib.FieldTheory.PolynomialGaloisGroup
import Mathlib.RingTheory.RootsOfUnity.Basic
#align_import field_theory.abel_ruffini from "leanprover-community/mathlib"@"e3f4be1fcb5376c4948d7f095bec45350bfb9d1a"
noncomputable section
open scoped Classical Polynomial IntermediateField
open Polynomial IntermediateField
section AbelRuffini
variable {F : Type*} [Field F] {E : Type*} [Field E] [Algebra F E]
theorem gal_zero_isSolvable : IsSolvable (0 : F[X]).Gal := by infer_instance
#align gal_zero_is_solvable gal_zero_isSolvable
theorem gal_one_isSolvable : IsSolvable (1 : F[X]).Gal := by infer_instance
#align gal_one_is_solvable gal_one_isSolvable
theorem gal_C_isSolvable (x : F) : IsSolvable (C x).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_C_is_solvable gal_C_isSolvable
theorem gal_X_isSolvable : IsSolvable (X : F[X]).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_is_solvable gal_X_isSolvable
theorem gal_X_sub_C_isSolvable (x : F) : IsSolvable (X - C x).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_sub_C_is_solvable gal_X_sub_C_isSolvable
theorem gal_X_pow_isSolvable (n : ℕ) : IsSolvable (X ^ n : F[X]).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_pow_is_solvable gal_X_pow_isSolvable
theorem gal_mul_isSolvable {p q : F[X]} (_ : IsSolvable p.Gal) (_ : IsSolvable q.Gal) :
IsSolvable (p * q).Gal :=
solvable_of_solvable_injective (Gal.restrictProd_injective p q)
#align gal_mul_is_solvable gal_mul_isSolvable
theorem gal_prod_isSolvable {s : Multiset F[X]} (hs : ∀ p ∈ s, IsSolvable (Gal p)) :
IsSolvable s.prod.Gal := by
apply Multiset.induction_on' s
· exact gal_one_isSolvable
· intro p t hps _ ht
rw [Multiset.insert_eq_cons, Multiset.prod_cons]
exact gal_mul_isSolvable (hs p hps) ht
#align gal_prod_is_solvable gal_prod_isSolvable
theorem gal_isSolvable_of_splits {p q : F[X]}
(_ : Fact (p.Splits (algebraMap F q.SplittingField))) (hq : IsSolvable q.Gal) :
IsSolvable p.Gal :=
haveI : IsSolvable (q.SplittingField ≃ₐ[F] q.SplittingField) := hq
solvable_of_surjective (AlgEquiv.restrictNormalHom_surjective q.SplittingField)
#align gal_is_solvable_of_splits gal_isSolvable_of_splits
theorem gal_isSolvable_tower (p q : F[X]) (hpq : p.Splits (algebraMap F q.SplittingField))
(hp : IsSolvable p.Gal) (hq : IsSolvable (q.map (algebraMap F p.SplittingField)).Gal) :
IsSolvable q.Gal := by
let K := p.SplittingField
let L := q.SplittingField
haveI : Fact (p.Splits (algebraMap F L)) := ⟨hpq⟩
let ϕ : (L ≃ₐ[K] L) ≃* (q.map (algebraMap F K)).Gal :=
(IsSplittingField.algEquiv L (q.map (algebraMap F K))).autCongr
have ϕ_inj : Function.Injective ϕ.toMonoidHom := ϕ.injective
haveI : IsSolvable (K ≃ₐ[F] K) := hp
haveI : IsSolvable (L ≃ₐ[K] L) := solvable_of_solvable_injective ϕ_inj
exact isSolvable_of_isScalarTower F p.SplittingField q.SplittingField
#align gal_is_solvable_tower gal_isSolvable_tower
section GalXPowSubC
| Mathlib/FieldTheory/AbelRuffini.lean | 98 | 114 | theorem gal_X_pow_sub_one_isSolvable (n : ℕ) : IsSolvable (X ^ n - 1 : F[X]).Gal := by |
by_cases hn : n = 0
· rw [hn, pow_zero, sub_self]
exact gal_zero_isSolvable
have hn' : 0 < n := pos_iff_ne_zero.mpr hn
have hn'' : (X ^ n - 1 : F[X]) ≠ 0 := X_pow_sub_C_ne_zero hn' 1
apply isSolvable_of_comm
intro σ τ
ext a ha
simp only [mem_rootSet_of_ne hn'', map_sub, aeval_X_pow, aeval_one, sub_eq_zero] at ha
have key : ∀ σ : (X ^ n - 1 : F[X]).Gal, ∃ m : ℕ, σ a = a ^ m := by
intro σ
lift n to ℕ+ using hn'
exact map_rootsOfUnity_eq_pow_self σ.toAlgHom (rootsOfUnity.mkOfPowEq a ha)
obtain ⟨c, hc⟩ := key σ
obtain ⟨d, hd⟩ := key τ
rw [σ.mul_apply, τ.mul_apply, hc, τ.map_pow, hd, σ.map_pow, hc, ← pow_mul, pow_mul']
| 2,036 |
import Mathlib.GroupTheory.Solvable
import Mathlib.FieldTheory.PolynomialGaloisGroup
import Mathlib.RingTheory.RootsOfUnity.Basic
#align_import field_theory.abel_ruffini from "leanprover-community/mathlib"@"e3f4be1fcb5376c4948d7f095bec45350bfb9d1a"
noncomputable section
open scoped Classical Polynomial IntermediateField
open Polynomial IntermediateField
section AbelRuffini
variable {F : Type*} [Field F] {E : Type*} [Field E] [Algebra F E]
theorem gal_zero_isSolvable : IsSolvable (0 : F[X]).Gal := by infer_instance
#align gal_zero_is_solvable gal_zero_isSolvable
theorem gal_one_isSolvable : IsSolvable (1 : F[X]).Gal := by infer_instance
#align gal_one_is_solvable gal_one_isSolvable
theorem gal_C_isSolvable (x : F) : IsSolvable (C x).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_C_is_solvable gal_C_isSolvable
theorem gal_X_isSolvable : IsSolvable (X : F[X]).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_is_solvable gal_X_isSolvable
theorem gal_X_sub_C_isSolvable (x : F) : IsSolvable (X - C x).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_sub_C_is_solvable gal_X_sub_C_isSolvable
theorem gal_X_pow_isSolvable (n : ℕ) : IsSolvable (X ^ n : F[X]).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_pow_is_solvable gal_X_pow_isSolvable
theorem gal_mul_isSolvable {p q : F[X]} (_ : IsSolvable p.Gal) (_ : IsSolvable q.Gal) :
IsSolvable (p * q).Gal :=
solvable_of_solvable_injective (Gal.restrictProd_injective p q)
#align gal_mul_is_solvable gal_mul_isSolvable
theorem gal_prod_isSolvable {s : Multiset F[X]} (hs : ∀ p ∈ s, IsSolvable (Gal p)) :
IsSolvable s.prod.Gal := by
apply Multiset.induction_on' s
· exact gal_one_isSolvable
· intro p t hps _ ht
rw [Multiset.insert_eq_cons, Multiset.prod_cons]
exact gal_mul_isSolvable (hs p hps) ht
#align gal_prod_is_solvable gal_prod_isSolvable
theorem gal_isSolvable_of_splits {p q : F[X]}
(_ : Fact (p.Splits (algebraMap F q.SplittingField))) (hq : IsSolvable q.Gal) :
IsSolvable p.Gal :=
haveI : IsSolvable (q.SplittingField ≃ₐ[F] q.SplittingField) := hq
solvable_of_surjective (AlgEquiv.restrictNormalHom_surjective q.SplittingField)
#align gal_is_solvable_of_splits gal_isSolvable_of_splits
theorem gal_isSolvable_tower (p q : F[X]) (hpq : p.Splits (algebraMap F q.SplittingField))
(hp : IsSolvable p.Gal) (hq : IsSolvable (q.map (algebraMap F p.SplittingField)).Gal) :
IsSolvable q.Gal := by
let K := p.SplittingField
let L := q.SplittingField
haveI : Fact (p.Splits (algebraMap F L)) := ⟨hpq⟩
let ϕ : (L ≃ₐ[K] L) ≃* (q.map (algebraMap F K)).Gal :=
(IsSplittingField.algEquiv L (q.map (algebraMap F K))).autCongr
have ϕ_inj : Function.Injective ϕ.toMonoidHom := ϕ.injective
haveI : IsSolvable (K ≃ₐ[F] K) := hp
haveI : IsSolvable (L ≃ₐ[K] L) := solvable_of_solvable_injective ϕ_inj
exact isSolvable_of_isScalarTower F p.SplittingField q.SplittingField
#align gal_is_solvable_tower gal_isSolvable_tower
section GalXPowSubC
theorem gal_X_pow_sub_one_isSolvable (n : ℕ) : IsSolvable (X ^ n - 1 : F[X]).Gal := by
by_cases hn : n = 0
· rw [hn, pow_zero, sub_self]
exact gal_zero_isSolvable
have hn' : 0 < n := pos_iff_ne_zero.mpr hn
have hn'' : (X ^ n - 1 : F[X]) ≠ 0 := X_pow_sub_C_ne_zero hn' 1
apply isSolvable_of_comm
intro σ τ
ext a ha
simp only [mem_rootSet_of_ne hn'', map_sub, aeval_X_pow, aeval_one, sub_eq_zero] at ha
have key : ∀ σ : (X ^ n - 1 : F[X]).Gal, ∃ m : ℕ, σ a = a ^ m := by
intro σ
lift n to ℕ+ using hn'
exact map_rootsOfUnity_eq_pow_self σ.toAlgHom (rootsOfUnity.mkOfPowEq a ha)
obtain ⟨c, hc⟩ := key σ
obtain ⟨d, hd⟩ := key τ
rw [σ.mul_apply, τ.mul_apply, hc, τ.map_pow, hd, σ.map_pow, hc, ← pow_mul, pow_mul']
set_option linter.uppercaseLean3 false in
#align gal_X_pow_sub_one_is_solvable gal_X_pow_sub_one_isSolvable
| Mathlib/FieldTheory/AbelRuffini.lean | 118 | 153 | theorem gal_X_pow_sub_C_isSolvable_aux (n : ℕ) (a : F)
(h : (X ^ n - 1 : F[X]).Splits (RingHom.id F)) : IsSolvable (X ^ n - C a).Gal := by |
by_cases ha : a = 0
· rw [ha, C_0, sub_zero]
exact gal_X_pow_isSolvable n
have ha' : algebraMap F (X ^ n - C a).SplittingField a ≠ 0 :=
mt ((injective_iff_map_eq_zero _).mp (RingHom.injective _) a) ha
by_cases hn : n = 0
· rw [hn, pow_zero, ← C_1, ← C_sub]
exact gal_C_isSolvable (1 - a)
have hn' : 0 < n := pos_iff_ne_zero.mpr hn
have hn'' : X ^ n - C a ≠ 0 := X_pow_sub_C_ne_zero hn' a
have hn''' : (X ^ n - 1 : F[X]) ≠ 0 := X_pow_sub_C_ne_zero hn' 1
have mem_range : ∀ {c : (X ^ n - C a).SplittingField},
(c ^ n = 1 → (∃ d, algebraMap F (X ^ n - C a).SplittingField d = c)) := fun {c} hc =>
RingHom.mem_range.mp (minpoly.mem_range_of_degree_eq_one F c (h.def.resolve_left hn'''
(minpoly.irreducible ((SplittingField.instNormal (X ^ n - C a)).isIntegral c))
(minpoly.dvd F c (by rwa [map_id, AlgHom.map_sub, sub_eq_zero, aeval_X_pow, aeval_one]))))
apply isSolvable_of_comm
intro σ τ
ext b hb
rw [mem_rootSet_of_ne hn'', map_sub, aeval_X_pow, aeval_C, sub_eq_zero] at hb
have hb' : b ≠ 0 := by
intro hb'
rw [hb', zero_pow hn] at hb
exact ha' hb.symm
have key : ∀ σ : (X ^ n - C a).Gal, ∃ c, σ b = b * algebraMap F _ c := by
intro σ
have key : (σ b / b) ^ n = 1 := by rw [div_pow, ← σ.map_pow, hb, σ.commutes, div_self ha']
obtain ⟨c, hc⟩ := mem_range key
use c
rw [hc, mul_div_cancel₀ (σ b) hb']
obtain ⟨c, hc⟩ := key σ
obtain ⟨d, hd⟩ := key τ
rw [σ.mul_apply, τ.mul_apply, hc, τ.map_mul, τ.commutes, hd, σ.map_mul, σ.commutes, hc,
mul_assoc, mul_assoc, mul_right_inj' hb', mul_comm]
| 2,036 |
import Mathlib.GroupTheory.Solvable
import Mathlib.FieldTheory.PolynomialGaloisGroup
import Mathlib.RingTheory.RootsOfUnity.Basic
#align_import field_theory.abel_ruffini from "leanprover-community/mathlib"@"e3f4be1fcb5376c4948d7f095bec45350bfb9d1a"
noncomputable section
open scoped Classical Polynomial IntermediateField
open Polynomial IntermediateField
section AbelRuffini
variable {F : Type*} [Field F] {E : Type*} [Field E] [Algebra F E]
theorem gal_zero_isSolvable : IsSolvable (0 : F[X]).Gal := by infer_instance
#align gal_zero_is_solvable gal_zero_isSolvable
theorem gal_one_isSolvable : IsSolvable (1 : F[X]).Gal := by infer_instance
#align gal_one_is_solvable gal_one_isSolvable
theorem gal_C_isSolvable (x : F) : IsSolvable (C x).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_C_is_solvable gal_C_isSolvable
theorem gal_X_isSolvable : IsSolvable (X : F[X]).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_is_solvable gal_X_isSolvable
theorem gal_X_sub_C_isSolvable (x : F) : IsSolvable (X - C x).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_sub_C_is_solvable gal_X_sub_C_isSolvable
theorem gal_X_pow_isSolvable (n : ℕ) : IsSolvable (X ^ n : F[X]).Gal := by infer_instance
set_option linter.uppercaseLean3 false in
#align gal_X_pow_is_solvable gal_X_pow_isSolvable
theorem gal_mul_isSolvable {p q : F[X]} (_ : IsSolvable p.Gal) (_ : IsSolvable q.Gal) :
IsSolvable (p * q).Gal :=
solvable_of_solvable_injective (Gal.restrictProd_injective p q)
#align gal_mul_is_solvable gal_mul_isSolvable
theorem gal_prod_isSolvable {s : Multiset F[X]} (hs : ∀ p ∈ s, IsSolvable (Gal p)) :
IsSolvable s.prod.Gal := by
apply Multiset.induction_on' s
· exact gal_one_isSolvable
· intro p t hps _ ht
rw [Multiset.insert_eq_cons, Multiset.prod_cons]
exact gal_mul_isSolvable (hs p hps) ht
#align gal_prod_is_solvable gal_prod_isSolvable
theorem gal_isSolvable_of_splits {p q : F[X]}
(_ : Fact (p.Splits (algebraMap F q.SplittingField))) (hq : IsSolvable q.Gal) :
IsSolvable p.Gal :=
haveI : IsSolvable (q.SplittingField ≃ₐ[F] q.SplittingField) := hq
solvable_of_surjective (AlgEquiv.restrictNormalHom_surjective q.SplittingField)
#align gal_is_solvable_of_splits gal_isSolvable_of_splits
theorem gal_isSolvable_tower (p q : F[X]) (hpq : p.Splits (algebraMap F q.SplittingField))
(hp : IsSolvable p.Gal) (hq : IsSolvable (q.map (algebraMap F p.SplittingField)).Gal) :
IsSolvable q.Gal := by
let K := p.SplittingField
let L := q.SplittingField
haveI : Fact (p.Splits (algebraMap F L)) := ⟨hpq⟩
let ϕ : (L ≃ₐ[K] L) ≃* (q.map (algebraMap F K)).Gal :=
(IsSplittingField.algEquiv L (q.map (algebraMap F K))).autCongr
have ϕ_inj : Function.Injective ϕ.toMonoidHom := ϕ.injective
haveI : IsSolvable (K ≃ₐ[F] K) := hp
haveI : IsSolvable (L ≃ₐ[K] L) := solvable_of_solvable_injective ϕ_inj
exact isSolvable_of_isScalarTower F p.SplittingField q.SplittingField
#align gal_is_solvable_tower gal_isSolvable_tower
variable (F)
inductive IsSolvableByRad : E → Prop
| base (α : F) : IsSolvableByRad (algebraMap F E α)
| add (α β : E) : IsSolvableByRad α → IsSolvableByRad β → IsSolvableByRad (α + β)
| neg (α : E) : IsSolvableByRad α → IsSolvableByRad (-α)
| mul (α β : E) : IsSolvableByRad α → IsSolvableByRad β → IsSolvableByRad (α * β)
| inv (α : E) : IsSolvableByRad α → IsSolvableByRad α⁻¹
| rad (α : E) (n : ℕ) (hn : n ≠ 0) : IsSolvableByRad (α ^ n) → IsSolvableByRad α
#align is_solvable_by_rad IsSolvableByRad
variable (E)
def solvableByRad : IntermediateField F E where
carrier := IsSolvableByRad F
zero_mem' := by
change IsSolvableByRad F 0
convert IsSolvableByRad.base (E := E) (0 : F); rw [RingHom.map_zero]
add_mem' := by apply IsSolvableByRad.add
one_mem' := by
change IsSolvableByRad F 1
convert IsSolvableByRad.base (E := E) (1 : F); rw [RingHom.map_one]
mul_mem' := by apply IsSolvableByRad.mul
inv_mem' := IsSolvableByRad.inv
algebraMap_mem' := IsSolvableByRad.base
#align solvable_by_rad solvableByRad
namespace solvableByRad
variable {F} {E} {α : E}
| Mathlib/FieldTheory/AbelRuffini.lean | 248 | 280 | theorem induction (P : solvableByRad F E → Prop)
(base : ∀ α : F, P (algebraMap F (solvableByRad F E) α))
(add : ∀ α β : solvableByRad F E, P α → P β → P (α + β))
(neg : ∀ α : solvableByRad F E, P α → P (-α))
(mul : ∀ α β : solvableByRad F E, P α → P β → P (α * β))
(inv : ∀ α : solvableByRad F E, P α → P α⁻¹)
(rad : ∀ α : solvableByRad F E, ∀ n : ℕ, n ≠ 0 → P (α ^ n) → P α) (α : solvableByRad F E) :
P α := by |
revert α
suffices ∀ α : E, IsSolvableByRad F α → ∃ β : solvableByRad F E, ↑β = α ∧ P β by
intro α
obtain ⟨α₀, hα₀, Pα⟩ := this α (Subtype.mem α)
convert Pα
exact Subtype.ext hα₀.symm
apply IsSolvableByRad.rec
· exact fun α => ⟨algebraMap F (solvableByRad F E) α, rfl, base α⟩
· intro α β _ _ Pα Pβ
obtain ⟨⟨α₀, hα₀, Pα⟩, β₀, hβ₀, Pβ⟩ := Pα, Pβ
exact ⟨α₀ + β₀, by rw [← hα₀, ← hβ₀]; rfl, add α₀ β₀ Pα Pβ⟩
· intro α _ Pα
obtain ⟨α₀, hα₀, Pα⟩ := Pα
exact ⟨-α₀, by rw [← hα₀]; rfl, neg α₀ Pα⟩
· intro α β _ _ Pα Pβ
obtain ⟨⟨α₀, hα₀, Pα⟩, β₀, hβ₀, Pβ⟩ := Pα, Pβ
exact ⟨α₀ * β₀, by rw [← hα₀, ← hβ₀]; rfl, mul α₀ β₀ Pα Pβ⟩
· intro α _ Pα
obtain ⟨α₀, hα₀, Pα⟩ := Pα
exact ⟨α₀⁻¹, by rw [← hα₀]; rfl, inv α₀ Pα⟩
· intro α n hn hα Pα
obtain ⟨α₀, hα₀, Pα⟩ := Pα
refine ⟨⟨α, IsSolvableByRad.rad α n hn hα⟩, rfl, rad _ n hn ?_⟩
convert Pα
exact Subtype.ext (Eq.trans ((solvableByRad F E).coe_pow _ n) hα₀.symm)
| 2,036 |
import Mathlib.LinearAlgebra.Matrix.BilinearForm
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Vandermonde
import Mathlib.LinearAlgebra.Trace
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.FieldTheory.Galois
import Mathlib.RingTheory.PowerBasis
import Mathlib.FieldTheory.Minpoly.MinpolyDiv
#align_import ring_theory.trace from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
variable {R S T : Type*} [CommRing R] [CommRing S] [CommRing T]
variable [Algebra R S] [Algebra R T]
variable {K L : Type*} [Field K] [Field L] [Algebra K L]
variable {ι κ : Type w} [Fintype ι]
open FiniteDimensional
open LinearMap (BilinForm)
open LinearMap
open Matrix
open scoped Matrix
namespace Algebra
variable (b : Basis ι R S)
variable (R S)
noncomputable def trace : S →ₗ[R] R :=
(LinearMap.trace R S).comp (lmul R S).toLinearMap
#align algebra.trace Algebra.trace
variable {S}
-- Not a `simp` lemma since there are more interesting ways to rewrite `trace R S x`,
-- for example `trace_trace`
theorem trace_apply (x) : trace R S x = LinearMap.trace R S (lmul R S x) :=
rfl
#align algebra.trace_apply Algebra.trace_apply
| Mathlib/RingTheory/Trace.lean | 102 | 103 | theorem trace_eq_zero_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) :
trace R S = 0 := by | ext s; simp [trace_apply, LinearMap.trace, h]
| 2,037 |
import Mathlib.LinearAlgebra.Matrix.BilinearForm
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Vandermonde
import Mathlib.LinearAlgebra.Trace
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.FieldTheory.Galois
import Mathlib.RingTheory.PowerBasis
import Mathlib.FieldTheory.Minpoly.MinpolyDiv
#align_import ring_theory.trace from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
variable {R S T : Type*} [CommRing R] [CommRing S] [CommRing T]
variable [Algebra R S] [Algebra R T]
variable {K L : Type*} [Field K] [Field L] [Algebra K L]
variable {ι κ : Type w} [Fintype ι]
open FiniteDimensional
open LinearMap (BilinForm)
open LinearMap
open Matrix
open scoped Matrix
namespace Algebra
variable (b : Basis ι R S)
variable (R S)
noncomputable def trace : S →ₗ[R] R :=
(LinearMap.trace R S).comp (lmul R S).toLinearMap
#align algebra.trace Algebra.trace
variable {S}
-- Not a `simp` lemma since there are more interesting ways to rewrite `trace R S x`,
-- for example `trace_trace`
theorem trace_apply (x) : trace R S x = LinearMap.trace R S (lmul R S x) :=
rfl
#align algebra.trace_apply Algebra.trace_apply
theorem trace_eq_zero_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) :
trace R S = 0 := by ext s; simp [trace_apply, LinearMap.trace, h]
#align algebra.trace_eq_zero_of_not_exists_basis Algebra.trace_eq_zero_of_not_exists_basis
variable {R}
-- Can't be a `simp` lemma because it depends on a choice of basis
| Mathlib/RingTheory/Trace.lean | 109 | 111 | theorem trace_eq_matrix_trace [DecidableEq ι] (b : Basis ι R S) (s : S) :
trace R S s = Matrix.trace (Algebra.leftMulMatrix b s) := by |
rw [trace_apply, LinearMap.trace_eq_matrix_trace _ b, ← toMatrix_lmul_eq]; rfl
| 2,037 |
import Mathlib.LinearAlgebra.Matrix.BilinearForm
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Vandermonde
import Mathlib.LinearAlgebra.Trace
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.FieldTheory.Galois
import Mathlib.RingTheory.PowerBasis
import Mathlib.FieldTheory.Minpoly.MinpolyDiv
#align_import ring_theory.trace from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
variable {R S T : Type*} [CommRing R] [CommRing S] [CommRing T]
variable [Algebra R S] [Algebra R T]
variable {K L : Type*} [Field K] [Field L] [Algebra K L]
variable {ι κ : Type w} [Fintype ι]
open FiniteDimensional
open LinearMap (BilinForm)
open LinearMap
open Matrix
open scoped Matrix
namespace Algebra
variable (b : Basis ι R S)
variable (R S)
noncomputable def trace : S →ₗ[R] R :=
(LinearMap.trace R S).comp (lmul R S).toLinearMap
#align algebra.trace Algebra.trace
variable {S}
-- Not a `simp` lemma since there are more interesting ways to rewrite `trace R S x`,
-- for example `trace_trace`
theorem trace_apply (x) : trace R S x = LinearMap.trace R S (lmul R S x) :=
rfl
#align algebra.trace_apply Algebra.trace_apply
theorem trace_eq_zero_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) :
trace R S = 0 := by ext s; simp [trace_apply, LinearMap.trace, h]
#align algebra.trace_eq_zero_of_not_exists_basis Algebra.trace_eq_zero_of_not_exists_basis
variable {R}
-- Can't be a `simp` lemma because it depends on a choice of basis
theorem trace_eq_matrix_trace [DecidableEq ι] (b : Basis ι R S) (s : S) :
trace R S s = Matrix.trace (Algebra.leftMulMatrix b s) := by
rw [trace_apply, LinearMap.trace_eq_matrix_trace _ b, ← toMatrix_lmul_eq]; rfl
#align algebra.trace_eq_matrix_trace Algebra.trace_eq_matrix_trace
| Mathlib/RingTheory/Trace.lean | 115 | 119 | theorem trace_algebraMap_of_basis (x : R) : trace R S (algebraMap R S x) = Fintype.card ι • x := by |
haveI := Classical.decEq ι
rw [trace_apply, LinearMap.trace_eq_matrix_trace R b, Matrix.trace]
convert Finset.sum_const x
simp [-coe_lmul_eq_mul]
| 2,037 |
import Mathlib.LinearAlgebra.Matrix.BilinearForm
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Vandermonde
import Mathlib.LinearAlgebra.Trace
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.FieldTheory.Galois
import Mathlib.RingTheory.PowerBasis
import Mathlib.FieldTheory.Minpoly.MinpolyDiv
#align_import ring_theory.trace from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
variable {R S T : Type*} [CommRing R] [CommRing S] [CommRing T]
variable [Algebra R S] [Algebra R T]
variable {K L : Type*} [Field K] [Field L] [Algebra K L]
variable {ι κ : Type w} [Fintype ι]
open FiniteDimensional
open LinearMap (BilinForm)
open LinearMap
open Matrix
open scoped Matrix
namespace Algebra
variable (b : Basis ι R S)
variable (R S)
noncomputable def trace : S →ₗ[R] R :=
(LinearMap.trace R S).comp (lmul R S).toLinearMap
#align algebra.trace Algebra.trace
variable {S}
-- Not a `simp` lemma since there are more interesting ways to rewrite `trace R S x`,
-- for example `trace_trace`
theorem trace_apply (x) : trace R S x = LinearMap.trace R S (lmul R S x) :=
rfl
#align algebra.trace_apply Algebra.trace_apply
theorem trace_eq_zero_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) :
trace R S = 0 := by ext s; simp [trace_apply, LinearMap.trace, h]
#align algebra.trace_eq_zero_of_not_exists_basis Algebra.trace_eq_zero_of_not_exists_basis
variable {R}
-- Can't be a `simp` lemma because it depends on a choice of basis
theorem trace_eq_matrix_trace [DecidableEq ι] (b : Basis ι R S) (s : S) :
trace R S s = Matrix.trace (Algebra.leftMulMatrix b s) := by
rw [trace_apply, LinearMap.trace_eq_matrix_trace _ b, ← toMatrix_lmul_eq]; rfl
#align algebra.trace_eq_matrix_trace Algebra.trace_eq_matrix_trace
theorem trace_algebraMap_of_basis (x : R) : trace R S (algebraMap R S x) = Fintype.card ι • x := by
haveI := Classical.decEq ι
rw [trace_apply, LinearMap.trace_eq_matrix_trace R b, Matrix.trace]
convert Finset.sum_const x
simp [-coe_lmul_eq_mul]
#align algebra.trace_algebra_map_of_basis Algebra.trace_algebraMap_of_basis
@[simp]
| Mathlib/RingTheory/Trace.lean | 128 | 131 | theorem trace_algebraMap (x : K) : trace K L (algebraMap K L x) = finrank K L • x := by |
by_cases H : ∃ s : Finset L, Nonempty (Basis s K L)
· rw [trace_algebraMap_of_basis H.choose_spec.some, finrank_eq_card_basis H.choose_spec.some]
· simp [trace_eq_zero_of_not_exists_basis K H, finrank_eq_zero_of_not_exists_basis_finset H]
| 2,037 |
import Mathlib.LinearAlgebra.Matrix.BilinearForm
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Vandermonde
import Mathlib.LinearAlgebra.Trace
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.FieldTheory.Galois
import Mathlib.RingTheory.PowerBasis
import Mathlib.FieldTheory.Minpoly.MinpolyDiv
#align_import ring_theory.trace from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
variable {R S T : Type*} [CommRing R] [CommRing S] [CommRing T]
variable [Algebra R S] [Algebra R T]
variable {K L : Type*} [Field K] [Field L] [Algebra K L]
variable {ι κ : Type w} [Fintype ι]
open FiniteDimensional
open LinearMap (BilinForm)
open LinearMap
open Matrix
open scoped Matrix
namespace Algebra
variable (b : Basis ι R S)
variable (R S)
noncomputable def trace : S →ₗ[R] R :=
(LinearMap.trace R S).comp (lmul R S).toLinearMap
#align algebra.trace Algebra.trace
variable {S}
-- Not a `simp` lemma since there are more interesting ways to rewrite `trace R S x`,
-- for example `trace_trace`
theorem trace_apply (x) : trace R S x = LinearMap.trace R S (lmul R S x) :=
rfl
#align algebra.trace_apply Algebra.trace_apply
theorem trace_eq_zero_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) :
trace R S = 0 := by ext s; simp [trace_apply, LinearMap.trace, h]
#align algebra.trace_eq_zero_of_not_exists_basis Algebra.trace_eq_zero_of_not_exists_basis
variable {R}
-- Can't be a `simp` lemma because it depends on a choice of basis
theorem trace_eq_matrix_trace [DecidableEq ι] (b : Basis ι R S) (s : S) :
trace R S s = Matrix.trace (Algebra.leftMulMatrix b s) := by
rw [trace_apply, LinearMap.trace_eq_matrix_trace _ b, ← toMatrix_lmul_eq]; rfl
#align algebra.trace_eq_matrix_trace Algebra.trace_eq_matrix_trace
theorem trace_algebraMap_of_basis (x : R) : trace R S (algebraMap R S x) = Fintype.card ι • x := by
haveI := Classical.decEq ι
rw [trace_apply, LinearMap.trace_eq_matrix_trace R b, Matrix.trace]
convert Finset.sum_const x
simp [-coe_lmul_eq_mul]
#align algebra.trace_algebra_map_of_basis Algebra.trace_algebraMap_of_basis
@[simp]
theorem trace_algebraMap (x : K) : trace K L (algebraMap K L x) = finrank K L • x := by
by_cases H : ∃ s : Finset L, Nonempty (Basis s K L)
· rw [trace_algebraMap_of_basis H.choose_spec.some, finrank_eq_card_basis H.choose_spec.some]
· simp [trace_eq_zero_of_not_exists_basis K H, finrank_eq_zero_of_not_exists_basis_finset H]
#align algebra.trace_algebra_map Algebra.trace_algebraMap
| Mathlib/RingTheory/Trace.lean | 134 | 146 | theorem trace_trace_of_basis [Algebra S T] [IsScalarTower R S T] {ι κ : Type*} [Finite ι]
[Finite κ] (b : Basis ι R S) (c : Basis κ S T) (x : T) :
trace R S (trace S T x) = trace R T x := by |
haveI := Classical.decEq ι
haveI := Classical.decEq κ
cases nonempty_fintype ι
cases nonempty_fintype κ
rw [trace_eq_matrix_trace (b.smul c), trace_eq_matrix_trace b, trace_eq_matrix_trace c,
Matrix.trace, Matrix.trace, Matrix.trace, ← Finset.univ_product_univ, Finset.sum_product]
refine Finset.sum_congr rfl fun i _ ↦ ?_
simp only [AlgHom.map_sum, smul_leftMulMatrix, Finset.sum_apply,
Matrix.diag, Finset.sum_apply
i (Finset.univ : Finset κ) fun y => leftMulMatrix b (leftMulMatrix c x y y)]
| 2,037 |
import Mathlib.LinearAlgebra.Matrix.BilinearForm
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Vandermonde
import Mathlib.LinearAlgebra.Trace
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.FieldTheory.Galois
import Mathlib.RingTheory.PowerBasis
import Mathlib.FieldTheory.Minpoly.MinpolyDiv
#align_import ring_theory.trace from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
variable {R S T : Type*} [CommRing R] [CommRing S] [CommRing T]
variable [Algebra R S] [Algebra R T]
variable {K L : Type*} [Field K] [Field L] [Algebra K L]
variable {ι κ : Type w} [Fintype ι]
open FiniteDimensional
open LinearMap (BilinForm)
open LinearMap
open Matrix
open scoped Matrix
namespace Algebra
variable (b : Basis ι R S)
variable (R S)
noncomputable def trace : S →ₗ[R] R :=
(LinearMap.trace R S).comp (lmul R S).toLinearMap
#align algebra.trace Algebra.trace
variable {S}
-- Not a `simp` lemma since there are more interesting ways to rewrite `trace R S x`,
-- for example `trace_trace`
theorem trace_apply (x) : trace R S x = LinearMap.trace R S (lmul R S x) :=
rfl
#align algebra.trace_apply Algebra.trace_apply
theorem trace_eq_zero_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) :
trace R S = 0 := by ext s; simp [trace_apply, LinearMap.trace, h]
#align algebra.trace_eq_zero_of_not_exists_basis Algebra.trace_eq_zero_of_not_exists_basis
variable {R}
-- Can't be a `simp` lemma because it depends on a choice of basis
theorem trace_eq_matrix_trace [DecidableEq ι] (b : Basis ι R S) (s : S) :
trace R S s = Matrix.trace (Algebra.leftMulMatrix b s) := by
rw [trace_apply, LinearMap.trace_eq_matrix_trace _ b, ← toMatrix_lmul_eq]; rfl
#align algebra.trace_eq_matrix_trace Algebra.trace_eq_matrix_trace
theorem trace_algebraMap_of_basis (x : R) : trace R S (algebraMap R S x) = Fintype.card ι • x := by
haveI := Classical.decEq ι
rw [trace_apply, LinearMap.trace_eq_matrix_trace R b, Matrix.trace]
convert Finset.sum_const x
simp [-coe_lmul_eq_mul]
#align algebra.trace_algebra_map_of_basis Algebra.trace_algebraMap_of_basis
@[simp]
theorem trace_algebraMap (x : K) : trace K L (algebraMap K L x) = finrank K L • x := by
by_cases H : ∃ s : Finset L, Nonempty (Basis s K L)
· rw [trace_algebraMap_of_basis H.choose_spec.some, finrank_eq_card_basis H.choose_spec.some]
· simp [trace_eq_zero_of_not_exists_basis K H, finrank_eq_zero_of_not_exists_basis_finset H]
#align algebra.trace_algebra_map Algebra.trace_algebraMap
theorem trace_trace_of_basis [Algebra S T] [IsScalarTower R S T] {ι κ : Type*} [Finite ι]
[Finite κ] (b : Basis ι R S) (c : Basis κ S T) (x : T) :
trace R S (trace S T x) = trace R T x := by
haveI := Classical.decEq ι
haveI := Classical.decEq κ
cases nonempty_fintype ι
cases nonempty_fintype κ
rw [trace_eq_matrix_trace (b.smul c), trace_eq_matrix_trace b, trace_eq_matrix_trace c,
Matrix.trace, Matrix.trace, Matrix.trace, ← Finset.univ_product_univ, Finset.sum_product]
refine Finset.sum_congr rfl fun i _ ↦ ?_
simp only [AlgHom.map_sum, smul_leftMulMatrix, Finset.sum_apply,
Matrix.diag, Finset.sum_apply
i (Finset.univ : Finset κ) fun y => leftMulMatrix b (leftMulMatrix c x y y)]
#align algebra.trace_trace_of_basis Algebra.trace_trace_of_basis
| Mathlib/RingTheory/Trace.lean | 149 | 153 | theorem trace_comp_trace_of_basis [Algebra S T] [IsScalarTower R S T] {ι κ : Type*} [Finite ι]
[Finite κ] (b : Basis ι R S) (c : Basis κ S T) :
(trace R S).comp ((trace S T).restrictScalars R) = trace R T := by |
ext
rw [LinearMap.comp_apply, LinearMap.restrictScalars_apply, trace_trace_of_basis b c]
| 2,037 |
import Mathlib.LinearAlgebra.Matrix.BilinearForm
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Vandermonde
import Mathlib.LinearAlgebra.Trace
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.FieldTheory.Galois
import Mathlib.RingTheory.PowerBasis
import Mathlib.FieldTheory.Minpoly.MinpolyDiv
#align_import ring_theory.trace from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
variable {R S T : Type*} [CommRing R] [CommRing S] [CommRing T]
variable [Algebra R S] [Algebra R T]
variable {K L : Type*} [Field K] [Field L] [Algebra K L]
variable {ι κ : Type w} [Fintype ι]
open FiniteDimensional
open LinearMap (BilinForm)
open LinearMap
open Matrix
open scoped Matrix
namespace Algebra
variable (b : Basis ι R S)
variable (R S)
noncomputable def trace : S →ₗ[R] R :=
(LinearMap.trace R S).comp (lmul R S).toLinearMap
#align algebra.trace Algebra.trace
variable {S}
-- Not a `simp` lemma since there are more interesting ways to rewrite `trace R S x`,
-- for example `trace_trace`
theorem trace_apply (x) : trace R S x = LinearMap.trace R S (lmul R S x) :=
rfl
#align algebra.trace_apply Algebra.trace_apply
theorem trace_eq_zero_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) :
trace R S = 0 := by ext s; simp [trace_apply, LinearMap.trace, h]
#align algebra.trace_eq_zero_of_not_exists_basis Algebra.trace_eq_zero_of_not_exists_basis
variable {R}
-- Can't be a `simp` lemma because it depends on a choice of basis
theorem trace_eq_matrix_trace [DecidableEq ι] (b : Basis ι R S) (s : S) :
trace R S s = Matrix.trace (Algebra.leftMulMatrix b s) := by
rw [trace_apply, LinearMap.trace_eq_matrix_trace _ b, ← toMatrix_lmul_eq]; rfl
#align algebra.trace_eq_matrix_trace Algebra.trace_eq_matrix_trace
theorem trace_algebraMap_of_basis (x : R) : trace R S (algebraMap R S x) = Fintype.card ι • x := by
haveI := Classical.decEq ι
rw [trace_apply, LinearMap.trace_eq_matrix_trace R b, Matrix.trace]
convert Finset.sum_const x
simp [-coe_lmul_eq_mul]
#align algebra.trace_algebra_map_of_basis Algebra.trace_algebraMap_of_basis
@[simp]
theorem trace_algebraMap (x : K) : trace K L (algebraMap K L x) = finrank K L • x := by
by_cases H : ∃ s : Finset L, Nonempty (Basis s K L)
· rw [trace_algebraMap_of_basis H.choose_spec.some, finrank_eq_card_basis H.choose_spec.some]
· simp [trace_eq_zero_of_not_exists_basis K H, finrank_eq_zero_of_not_exists_basis_finset H]
#align algebra.trace_algebra_map Algebra.trace_algebraMap
theorem trace_trace_of_basis [Algebra S T] [IsScalarTower R S T] {ι κ : Type*} [Finite ι]
[Finite κ] (b : Basis ι R S) (c : Basis κ S T) (x : T) :
trace R S (trace S T x) = trace R T x := by
haveI := Classical.decEq ι
haveI := Classical.decEq κ
cases nonempty_fintype ι
cases nonempty_fintype κ
rw [trace_eq_matrix_trace (b.smul c), trace_eq_matrix_trace b, trace_eq_matrix_trace c,
Matrix.trace, Matrix.trace, Matrix.trace, ← Finset.univ_product_univ, Finset.sum_product]
refine Finset.sum_congr rfl fun i _ ↦ ?_
simp only [AlgHom.map_sum, smul_leftMulMatrix, Finset.sum_apply,
Matrix.diag, Finset.sum_apply
i (Finset.univ : Finset κ) fun y => leftMulMatrix b (leftMulMatrix c x y y)]
#align algebra.trace_trace_of_basis Algebra.trace_trace_of_basis
theorem trace_comp_trace_of_basis [Algebra S T] [IsScalarTower R S T] {ι κ : Type*} [Finite ι]
[Finite κ] (b : Basis ι R S) (c : Basis κ S T) :
(trace R S).comp ((trace S T).restrictScalars R) = trace R T := by
ext
rw [LinearMap.comp_apply, LinearMap.restrictScalars_apply, trace_trace_of_basis b c]
#align algebra.trace_comp_trace_of_basis Algebra.trace_comp_trace_of_basis
@[simp]
theorem trace_trace [Algebra K T] [Algebra L T] [IsScalarTower K L T] [FiniteDimensional K L]
[FiniteDimensional L T] (x : T) : trace K L (trace L T x) = trace K T x :=
trace_trace_of_basis (Basis.ofVectorSpace K L) (Basis.ofVectorSpace L T) x
#align algebra.trace_trace Algebra.trace_trace
@[simp]
| Mathlib/RingTheory/Trace.lean | 163 | 165 | theorem trace_comp_trace [Algebra K T] [Algebra L T] [IsScalarTower K L T] [FiniteDimensional K L]
[FiniteDimensional L T] : (trace K L).comp ((trace L T).restrictScalars K) = trace K T := by |
ext; rw [LinearMap.comp_apply, LinearMap.restrictScalars_apply, trace_trace]
| 2,037 |
import Mathlib.LinearAlgebra.Matrix.BilinearForm
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Vandermonde
import Mathlib.LinearAlgebra.Trace
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.FieldTheory.Galois
import Mathlib.RingTheory.PowerBasis
import Mathlib.FieldTheory.Minpoly.MinpolyDiv
#align_import ring_theory.trace from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
variable {R S T : Type*} [CommRing R] [CommRing S] [CommRing T]
variable [Algebra R S] [Algebra R T]
variable {K L : Type*} [Field K] [Field L] [Algebra K L]
variable {ι κ : Type w} [Fintype ι]
open FiniteDimensional
open LinearMap (BilinForm)
open LinearMap
open Matrix
open scoped Matrix
namespace Algebra
variable (b : Basis ι R S)
variable (R S)
noncomputable def trace : S →ₗ[R] R :=
(LinearMap.trace R S).comp (lmul R S).toLinearMap
#align algebra.trace Algebra.trace
variable {S}
-- Not a `simp` lemma since there are more interesting ways to rewrite `trace R S x`,
-- for example `trace_trace`
theorem trace_apply (x) : trace R S x = LinearMap.trace R S (lmul R S x) :=
rfl
#align algebra.trace_apply Algebra.trace_apply
theorem trace_eq_zero_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) :
trace R S = 0 := by ext s; simp [trace_apply, LinearMap.trace, h]
#align algebra.trace_eq_zero_of_not_exists_basis Algebra.trace_eq_zero_of_not_exists_basis
variable {R}
-- Can't be a `simp` lemma because it depends on a choice of basis
theorem trace_eq_matrix_trace [DecidableEq ι] (b : Basis ι R S) (s : S) :
trace R S s = Matrix.trace (Algebra.leftMulMatrix b s) := by
rw [trace_apply, LinearMap.trace_eq_matrix_trace _ b, ← toMatrix_lmul_eq]; rfl
#align algebra.trace_eq_matrix_trace Algebra.trace_eq_matrix_trace
theorem trace_algebraMap_of_basis (x : R) : trace R S (algebraMap R S x) = Fintype.card ι • x := by
haveI := Classical.decEq ι
rw [trace_apply, LinearMap.trace_eq_matrix_trace R b, Matrix.trace]
convert Finset.sum_const x
simp [-coe_lmul_eq_mul]
#align algebra.trace_algebra_map_of_basis Algebra.trace_algebraMap_of_basis
@[simp]
theorem trace_algebraMap (x : K) : trace K L (algebraMap K L x) = finrank K L • x := by
by_cases H : ∃ s : Finset L, Nonempty (Basis s K L)
· rw [trace_algebraMap_of_basis H.choose_spec.some, finrank_eq_card_basis H.choose_spec.some]
· simp [trace_eq_zero_of_not_exists_basis K H, finrank_eq_zero_of_not_exists_basis_finset H]
#align algebra.trace_algebra_map Algebra.trace_algebraMap
theorem trace_trace_of_basis [Algebra S T] [IsScalarTower R S T] {ι κ : Type*} [Finite ι]
[Finite κ] (b : Basis ι R S) (c : Basis κ S T) (x : T) :
trace R S (trace S T x) = trace R T x := by
haveI := Classical.decEq ι
haveI := Classical.decEq κ
cases nonempty_fintype ι
cases nonempty_fintype κ
rw [trace_eq_matrix_trace (b.smul c), trace_eq_matrix_trace b, trace_eq_matrix_trace c,
Matrix.trace, Matrix.trace, Matrix.trace, ← Finset.univ_product_univ, Finset.sum_product]
refine Finset.sum_congr rfl fun i _ ↦ ?_
simp only [AlgHom.map_sum, smul_leftMulMatrix, Finset.sum_apply,
Matrix.diag, Finset.sum_apply
i (Finset.univ : Finset κ) fun y => leftMulMatrix b (leftMulMatrix c x y y)]
#align algebra.trace_trace_of_basis Algebra.trace_trace_of_basis
theorem trace_comp_trace_of_basis [Algebra S T] [IsScalarTower R S T] {ι κ : Type*} [Finite ι]
[Finite κ] (b : Basis ι R S) (c : Basis κ S T) :
(trace R S).comp ((trace S T).restrictScalars R) = trace R T := by
ext
rw [LinearMap.comp_apply, LinearMap.restrictScalars_apply, trace_trace_of_basis b c]
#align algebra.trace_comp_trace_of_basis Algebra.trace_comp_trace_of_basis
@[simp]
theorem trace_trace [Algebra K T] [Algebra L T] [IsScalarTower K L T] [FiniteDimensional K L]
[FiniteDimensional L T] (x : T) : trace K L (trace L T x) = trace K T x :=
trace_trace_of_basis (Basis.ofVectorSpace K L) (Basis.ofVectorSpace L T) x
#align algebra.trace_trace Algebra.trace_trace
@[simp]
theorem trace_comp_trace [Algebra K T] [Algebra L T] [IsScalarTower K L T] [FiniteDimensional K L]
[FiniteDimensional L T] : (trace K L).comp ((trace L T).restrictScalars K) = trace K T := by
ext; rw [LinearMap.comp_apply, LinearMap.restrictScalars_apply, trace_trace]
#align algebra.trace_comp_trace Algebra.trace_comp_trace
@[simp]
| Mathlib/RingTheory/Trace.lean | 169 | 176 | theorem trace_prod_apply [Module.Free R S] [Module.Free R T] [Module.Finite R S] [Module.Finite R T]
(x : S × T) : trace R (S × T) x = trace R S x.fst + trace R T x.snd := by |
nontriviality R
let f := (lmul R S).toLinearMap.prodMap (lmul R T).toLinearMap
have : (lmul R (S × T)).toLinearMap = (prodMapLinear R S T S T R).comp f :=
LinearMap.ext₂ Prod.mul_def
simp_rw [trace, this]
exact trace_prodMap' _ _
| 2,037 |
import Mathlib.RingTheory.Trace
import Mathlib.FieldTheory.Finite.GaloisField
#align_import field_theory.finite.trace from "leanprover-community/mathlib"@"0723536a0522d24fc2f159a096fb3304bef77472"
namespace FiniteField
| Mathlib/FieldTheory/Finite/Trace.lean | 25 | 32 | theorem trace_to_zmod_nondegenerate (F : Type*) [Field F] [Finite F]
[Algebra (ZMod (ringChar F)) F] {a : F} (ha : a ≠ 0) :
∃ b : F, Algebra.trace (ZMod (ringChar F)) F (a * b) ≠ 0 := by |
haveI : Fact (ringChar F).Prime := ⟨CharP.char_is_prime F _⟩
have htr := traceForm_nondegenerate (ZMod (ringChar F)) F a
simp_rw [Algebra.traceForm_apply] at htr
by_contra! hf
exact ha (htr hf)
| 2,038 |
import Mathlib.LinearAlgebra.FreeModule.PID
import Mathlib.LinearAlgebra.FreeModule.Finite.Basic
import Mathlib.LinearAlgebra.BilinearForm.DualLattice
import Mathlib.RingTheory.DedekindDomain.Basic
import Mathlib.RingTheory.Localization.Module
import Mathlib.RingTheory.Trace
#align_import ring_theory.dedekind_domain.integral_closure from "leanprover-community/mathlib"@"4cf7ca0e69e048b006674cf4499e5c7d296a89e0"
variable (R A K : Type*) [CommRing R] [CommRing A] [Field K]
open scoped nonZeroDivisors Polynomial
variable [IsDomain A]
section IsIntegralClosure
open Algebra
variable [Algebra A K] [IsFractionRing A K]
variable (L : Type*) [Field L] (C : Type*) [CommRing C]
variable [Algebra K L] [Algebra A L] [IsScalarTower A K L]
variable [Algebra C L] [IsIntegralClosure C A L] [Algebra A C] [IsScalarTower A C L]
| Mathlib/RingTheory/DedekindDomain/IntegralClosure.lean | 65 | 83 | theorem IsIntegralClosure.isLocalization [Algebra.IsAlgebraic K L] :
IsLocalization (Algebra.algebraMapSubmonoid C A⁰) L := by |
haveI : IsDomain C :=
(IsIntegralClosure.equiv A C L (integralClosure A L)).toMulEquiv.isDomain (integralClosure A L)
haveI : NoZeroSMulDivisors A L := NoZeroSMulDivisors.trans A K L
haveI : NoZeroSMulDivisors A C := IsIntegralClosure.noZeroSMulDivisors A L
refine ⟨?_, fun z => ?_, fun {x y} h => ⟨1, ?_⟩⟩
· rintro ⟨_, x, hx, rfl⟩
rw [isUnit_iff_ne_zero, map_ne_zero_iff _ (IsIntegralClosure.algebraMap_injective C A L),
Subtype.coe_mk, map_ne_zero_iff _ (NoZeroSMulDivisors.algebraMap_injective A C)]
exact mem_nonZeroDivisors_iff_ne_zero.mp hx
· obtain ⟨m, hm⟩ :=
IsIntegral.exists_multiple_integral_of_isLocalization A⁰ z
(Algebra.IsIntegral.isIntegral (R := K) z)
obtain ⟨x, hx⟩ : ∃ x, algebraMap C L x = m • z := IsIntegralClosure.isIntegral_iff.mp hm
refine ⟨⟨x, algebraMap A C m, m, SetLike.coe_mem m, rfl⟩, ?_⟩
rw [Subtype.coe_mk, ← IsScalarTower.algebraMap_apply, hx, mul_comm, Submonoid.smul_def,
smul_def]
· simp only [IsIntegralClosure.algebraMap_injective C A L h]
| 2,039 |
import Mathlib.LinearAlgebra.FreeModule.PID
import Mathlib.LinearAlgebra.FreeModule.Finite.Basic
import Mathlib.LinearAlgebra.BilinearForm.DualLattice
import Mathlib.RingTheory.DedekindDomain.Basic
import Mathlib.RingTheory.Localization.Module
import Mathlib.RingTheory.Trace
#align_import ring_theory.dedekind_domain.integral_closure from "leanprover-community/mathlib"@"4cf7ca0e69e048b006674cf4499e5c7d296a89e0"
variable (R A K : Type*) [CommRing R] [CommRing A] [Field K]
open scoped nonZeroDivisors Polynomial
variable [IsDomain A]
section IsIntegralClosure
open Algebra
variable [Algebra A K] [IsFractionRing A K]
variable (L : Type*) [Field L] (C : Type*) [CommRing C]
variable [Algebra K L] [Algebra A L] [IsScalarTower A K L]
variable [Algebra C L] [IsIntegralClosure C A L] [Algebra A C] [IsScalarTower A C L]
theorem IsIntegralClosure.isLocalization [Algebra.IsAlgebraic K L] :
IsLocalization (Algebra.algebraMapSubmonoid C A⁰) L := by
haveI : IsDomain C :=
(IsIntegralClosure.equiv A C L (integralClosure A L)).toMulEquiv.isDomain (integralClosure A L)
haveI : NoZeroSMulDivisors A L := NoZeroSMulDivisors.trans A K L
haveI : NoZeroSMulDivisors A C := IsIntegralClosure.noZeroSMulDivisors A L
refine ⟨?_, fun z => ?_, fun {x y} h => ⟨1, ?_⟩⟩
· rintro ⟨_, x, hx, rfl⟩
rw [isUnit_iff_ne_zero, map_ne_zero_iff _ (IsIntegralClosure.algebraMap_injective C A L),
Subtype.coe_mk, map_ne_zero_iff _ (NoZeroSMulDivisors.algebraMap_injective A C)]
exact mem_nonZeroDivisors_iff_ne_zero.mp hx
· obtain ⟨m, hm⟩ :=
IsIntegral.exists_multiple_integral_of_isLocalization A⁰ z
(Algebra.IsIntegral.isIntegral (R := K) z)
obtain ⟨x, hx⟩ : ∃ x, algebraMap C L x = m • z := IsIntegralClosure.isIntegral_iff.mp hm
refine ⟨⟨x, algebraMap A C m, m, SetLike.coe_mem m, rfl⟩, ?_⟩
rw [Subtype.coe_mk, ← IsScalarTower.algebraMap_apply, hx, mul_comm, Submonoid.smul_def,
smul_def]
· simp only [IsIntegralClosure.algebraMap_injective C A L h]
theorem IsIntegralClosure.isLocalization_of_isSeparable [IsSeparable K L] :
IsLocalization (Algebra.algebraMapSubmonoid C A⁰) L :=
IsIntegralClosure.isLocalization A K L C
#align is_integral_closure.is_localization IsIntegralClosure.isLocalization_of_isSeparable
variable [FiniteDimensional K L]
variable {A K L}
| Mathlib/RingTheory/DedekindDomain/IntegralClosure.lean | 93 | 103 | theorem IsIntegralClosure.range_le_span_dualBasis [IsSeparable K L] {ι : Type*} [Fintype ι]
[DecidableEq ι] (b : Basis ι K L) (hb_int : ∀ i, IsIntegral A (b i)) [IsIntegrallyClosed A] :
LinearMap.range ((Algebra.linearMap C L).restrictScalars A) ≤
Submodule.span A (Set.range <| (traceForm K L).dualBasis (traceForm_nondegenerate K L) b) := by |
rw [← LinearMap.BilinForm.dualSubmodule_span_of_basis,
← LinearMap.BilinForm.le_flip_dualSubmodule, Submodule.span_le]
rintro _ ⟨i, rfl⟩ _ ⟨y, rfl⟩
simp only [LinearMap.coe_restrictScalars, linearMap_apply, LinearMap.BilinForm.flip_apply,
traceForm_apply]
refine IsIntegrallyClosed.isIntegral_iff.mp ?_
exact isIntegral_trace ((IsIntegralClosure.isIntegral A L y).algebraMap.mul (hb_int i))
| 2,039 |
import Mathlib.LinearAlgebra.FreeModule.PID
import Mathlib.LinearAlgebra.FreeModule.Finite.Basic
import Mathlib.LinearAlgebra.BilinearForm.DualLattice
import Mathlib.RingTheory.DedekindDomain.Basic
import Mathlib.RingTheory.Localization.Module
import Mathlib.RingTheory.Trace
#align_import ring_theory.dedekind_domain.integral_closure from "leanprover-community/mathlib"@"4cf7ca0e69e048b006674cf4499e5c7d296a89e0"
variable (R A K : Type*) [CommRing R] [CommRing A] [Field K]
open scoped nonZeroDivisors Polynomial
variable [IsDomain A]
section IsIntegralClosure
open Algebra
variable [Algebra A K] [IsFractionRing A K]
variable (L : Type*) [Field L] (C : Type*) [CommRing C]
variable [Algebra K L] [Algebra A L] [IsScalarTower A K L]
variable [Algebra C L] [IsIntegralClosure C A L] [Algebra A C] [IsScalarTower A C L]
theorem IsIntegralClosure.isLocalization [Algebra.IsAlgebraic K L] :
IsLocalization (Algebra.algebraMapSubmonoid C A⁰) L := by
haveI : IsDomain C :=
(IsIntegralClosure.equiv A C L (integralClosure A L)).toMulEquiv.isDomain (integralClosure A L)
haveI : NoZeroSMulDivisors A L := NoZeroSMulDivisors.trans A K L
haveI : NoZeroSMulDivisors A C := IsIntegralClosure.noZeroSMulDivisors A L
refine ⟨?_, fun z => ?_, fun {x y} h => ⟨1, ?_⟩⟩
· rintro ⟨_, x, hx, rfl⟩
rw [isUnit_iff_ne_zero, map_ne_zero_iff _ (IsIntegralClosure.algebraMap_injective C A L),
Subtype.coe_mk, map_ne_zero_iff _ (NoZeroSMulDivisors.algebraMap_injective A C)]
exact mem_nonZeroDivisors_iff_ne_zero.mp hx
· obtain ⟨m, hm⟩ :=
IsIntegral.exists_multiple_integral_of_isLocalization A⁰ z
(Algebra.IsIntegral.isIntegral (R := K) z)
obtain ⟨x, hx⟩ : ∃ x, algebraMap C L x = m • z := IsIntegralClosure.isIntegral_iff.mp hm
refine ⟨⟨x, algebraMap A C m, m, SetLike.coe_mem m, rfl⟩, ?_⟩
rw [Subtype.coe_mk, ← IsScalarTower.algebraMap_apply, hx, mul_comm, Submonoid.smul_def,
smul_def]
· simp only [IsIntegralClosure.algebraMap_injective C A L h]
theorem IsIntegralClosure.isLocalization_of_isSeparable [IsSeparable K L] :
IsLocalization (Algebra.algebraMapSubmonoid C A⁰) L :=
IsIntegralClosure.isLocalization A K L C
#align is_integral_closure.is_localization IsIntegralClosure.isLocalization_of_isSeparable
variable [FiniteDimensional K L]
variable {A K L}
theorem IsIntegralClosure.range_le_span_dualBasis [IsSeparable K L] {ι : Type*} [Fintype ι]
[DecidableEq ι] (b : Basis ι K L) (hb_int : ∀ i, IsIntegral A (b i)) [IsIntegrallyClosed A] :
LinearMap.range ((Algebra.linearMap C L).restrictScalars A) ≤
Submodule.span A (Set.range <| (traceForm K L).dualBasis (traceForm_nondegenerate K L) b) := by
rw [← LinearMap.BilinForm.dualSubmodule_span_of_basis,
← LinearMap.BilinForm.le_flip_dualSubmodule, Submodule.span_le]
rintro _ ⟨i, rfl⟩ _ ⟨y, rfl⟩
simp only [LinearMap.coe_restrictScalars, linearMap_apply, LinearMap.BilinForm.flip_apply,
traceForm_apply]
refine IsIntegrallyClosed.isIntegral_iff.mp ?_
exact isIntegral_trace ((IsIntegralClosure.isIntegral A L y).algebraMap.mul (hb_int i))
#align is_integral_closure.range_le_span_dual_basis IsIntegralClosure.range_le_span_dualBasis
| Mathlib/RingTheory/DedekindDomain/IntegralClosure.lean | 106 | 112 | theorem integralClosure_le_span_dualBasis [IsSeparable K L] {ι : Type*} [Fintype ι] [DecidableEq ι]
(b : Basis ι K L) (hb_int : ∀ i, IsIntegral A (b i)) [IsIntegrallyClosed A] :
Subalgebra.toSubmodule (integralClosure A L) ≤
Submodule.span A (Set.range <| (traceForm K L).dualBasis (traceForm_nondegenerate K L) b) := by |
refine le_trans ?_ (IsIntegralClosure.range_le_span_dualBasis (integralClosure A L) b hb_int)
intro x hx
exact ⟨⟨x, hx⟩, rfl⟩
| 2,039 |
import Mathlib.LinearAlgebra.FreeModule.PID
import Mathlib.LinearAlgebra.FreeModule.Finite.Basic
import Mathlib.LinearAlgebra.BilinearForm.DualLattice
import Mathlib.RingTheory.DedekindDomain.Basic
import Mathlib.RingTheory.Localization.Module
import Mathlib.RingTheory.Trace
#align_import ring_theory.dedekind_domain.integral_closure from "leanprover-community/mathlib"@"4cf7ca0e69e048b006674cf4499e5c7d296a89e0"
variable (R A K : Type*) [CommRing R] [CommRing A] [Field K]
open scoped nonZeroDivisors Polynomial
variable [IsDomain A]
section IsIntegralClosure
open Algebra
variable [Algebra A K] [IsFractionRing A K]
variable (L : Type*) [Field L] (C : Type*) [CommRing C]
variable [Algebra K L] [Algebra A L] [IsScalarTower A K L]
variable [Algebra C L] [IsIntegralClosure C A L] [Algebra A C] [IsScalarTower A C L]
theorem IsIntegralClosure.isLocalization [Algebra.IsAlgebraic K L] :
IsLocalization (Algebra.algebraMapSubmonoid C A⁰) L := by
haveI : IsDomain C :=
(IsIntegralClosure.equiv A C L (integralClosure A L)).toMulEquiv.isDomain (integralClosure A L)
haveI : NoZeroSMulDivisors A L := NoZeroSMulDivisors.trans A K L
haveI : NoZeroSMulDivisors A C := IsIntegralClosure.noZeroSMulDivisors A L
refine ⟨?_, fun z => ?_, fun {x y} h => ⟨1, ?_⟩⟩
· rintro ⟨_, x, hx, rfl⟩
rw [isUnit_iff_ne_zero, map_ne_zero_iff _ (IsIntegralClosure.algebraMap_injective C A L),
Subtype.coe_mk, map_ne_zero_iff _ (NoZeroSMulDivisors.algebraMap_injective A C)]
exact mem_nonZeroDivisors_iff_ne_zero.mp hx
· obtain ⟨m, hm⟩ :=
IsIntegral.exists_multiple_integral_of_isLocalization A⁰ z
(Algebra.IsIntegral.isIntegral (R := K) z)
obtain ⟨x, hx⟩ : ∃ x, algebraMap C L x = m • z := IsIntegralClosure.isIntegral_iff.mp hm
refine ⟨⟨x, algebraMap A C m, m, SetLike.coe_mem m, rfl⟩, ?_⟩
rw [Subtype.coe_mk, ← IsScalarTower.algebraMap_apply, hx, mul_comm, Submonoid.smul_def,
smul_def]
· simp only [IsIntegralClosure.algebraMap_injective C A L h]
theorem IsIntegralClosure.isLocalization_of_isSeparable [IsSeparable K L] :
IsLocalization (Algebra.algebraMapSubmonoid C A⁰) L :=
IsIntegralClosure.isLocalization A K L C
#align is_integral_closure.is_localization IsIntegralClosure.isLocalization_of_isSeparable
variable [FiniteDimensional K L]
variable {A K L}
theorem IsIntegralClosure.range_le_span_dualBasis [IsSeparable K L] {ι : Type*} [Fintype ι]
[DecidableEq ι] (b : Basis ι K L) (hb_int : ∀ i, IsIntegral A (b i)) [IsIntegrallyClosed A] :
LinearMap.range ((Algebra.linearMap C L).restrictScalars A) ≤
Submodule.span A (Set.range <| (traceForm K L).dualBasis (traceForm_nondegenerate K L) b) := by
rw [← LinearMap.BilinForm.dualSubmodule_span_of_basis,
← LinearMap.BilinForm.le_flip_dualSubmodule, Submodule.span_le]
rintro _ ⟨i, rfl⟩ _ ⟨y, rfl⟩
simp only [LinearMap.coe_restrictScalars, linearMap_apply, LinearMap.BilinForm.flip_apply,
traceForm_apply]
refine IsIntegrallyClosed.isIntegral_iff.mp ?_
exact isIntegral_trace ((IsIntegralClosure.isIntegral A L y).algebraMap.mul (hb_int i))
#align is_integral_closure.range_le_span_dual_basis IsIntegralClosure.range_le_span_dualBasis
theorem integralClosure_le_span_dualBasis [IsSeparable K L] {ι : Type*} [Fintype ι] [DecidableEq ι]
(b : Basis ι K L) (hb_int : ∀ i, IsIntegral A (b i)) [IsIntegrallyClosed A] :
Subalgebra.toSubmodule (integralClosure A L) ≤
Submodule.span A (Set.range <| (traceForm K L).dualBasis (traceForm_nondegenerate K L) b) := by
refine le_trans ?_ (IsIntegralClosure.range_le_span_dualBasis (integralClosure A L) b hb_int)
intro x hx
exact ⟨⟨x, hx⟩, rfl⟩
#align integral_closure_le_span_dual_basis integralClosure_le_span_dualBasis
variable (A K)
| Mathlib/RingTheory/DedekindDomain/IntegralClosure.lean | 119 | 138 | theorem exists_integral_multiples (s : Finset L) :
∃ y ≠ (0 : A), ∀ x ∈ s, IsIntegral A (y • x) := by |
haveI := Classical.decEq L
refine s.induction ?_ ?_
· use 1, one_ne_zero
rintro x ⟨⟩
· rintro x s hx ⟨y, hy, hs⟩
have := exists_integral_multiple
((IsFractionRing.isAlgebraic_iff A K L).mpr (.of_finite _ x))
((injective_iff_map_eq_zero (algebraMap A L)).mp ?_)
· rcases this with ⟨x', y', hy', hx'⟩
refine ⟨y * y', mul_ne_zero hy hy', fun x'' hx'' => ?_⟩
rcases Finset.mem_insert.mp hx'' with (rfl | hx'')
· rw [mul_smul, Algebra.smul_def, Algebra.smul_def, mul_comm _ x'', hx']
exact isIntegral_algebraMap.mul x'.2
· rw [mul_comm, mul_smul, Algebra.smul_def]
exact isIntegral_algebraMap.mul (hs _ hx'')
· rw [IsScalarTower.algebraMap_eq A K L]
apply (algebraMap K L).injective.comp
exact IsFractionRing.injective _ _
| 2,039 |
import Mathlib.LinearAlgebra.FreeModule.PID
import Mathlib.LinearAlgebra.FreeModule.Finite.Basic
import Mathlib.LinearAlgebra.BilinearForm.DualLattice
import Mathlib.RingTheory.DedekindDomain.Basic
import Mathlib.RingTheory.Localization.Module
import Mathlib.RingTheory.Trace
#align_import ring_theory.dedekind_domain.integral_closure from "leanprover-community/mathlib"@"4cf7ca0e69e048b006674cf4499e5c7d296a89e0"
variable (R A K : Type*) [CommRing R] [CommRing A] [Field K]
open scoped nonZeroDivisors Polynomial
variable [IsDomain A]
section IsIntegralClosure
open Algebra
variable [Algebra A K] [IsFractionRing A K]
variable (L : Type*) [Field L] (C : Type*) [CommRing C]
variable [Algebra K L] [Algebra A L] [IsScalarTower A K L]
variable [Algebra C L] [IsIntegralClosure C A L] [Algebra A C] [IsScalarTower A C L]
theorem IsIntegralClosure.isLocalization [Algebra.IsAlgebraic K L] :
IsLocalization (Algebra.algebraMapSubmonoid C A⁰) L := by
haveI : IsDomain C :=
(IsIntegralClosure.equiv A C L (integralClosure A L)).toMulEquiv.isDomain (integralClosure A L)
haveI : NoZeroSMulDivisors A L := NoZeroSMulDivisors.trans A K L
haveI : NoZeroSMulDivisors A C := IsIntegralClosure.noZeroSMulDivisors A L
refine ⟨?_, fun z => ?_, fun {x y} h => ⟨1, ?_⟩⟩
· rintro ⟨_, x, hx, rfl⟩
rw [isUnit_iff_ne_zero, map_ne_zero_iff _ (IsIntegralClosure.algebraMap_injective C A L),
Subtype.coe_mk, map_ne_zero_iff _ (NoZeroSMulDivisors.algebraMap_injective A C)]
exact mem_nonZeroDivisors_iff_ne_zero.mp hx
· obtain ⟨m, hm⟩ :=
IsIntegral.exists_multiple_integral_of_isLocalization A⁰ z
(Algebra.IsIntegral.isIntegral (R := K) z)
obtain ⟨x, hx⟩ : ∃ x, algebraMap C L x = m • z := IsIntegralClosure.isIntegral_iff.mp hm
refine ⟨⟨x, algebraMap A C m, m, SetLike.coe_mem m, rfl⟩, ?_⟩
rw [Subtype.coe_mk, ← IsScalarTower.algebraMap_apply, hx, mul_comm, Submonoid.smul_def,
smul_def]
· simp only [IsIntegralClosure.algebraMap_injective C A L h]
theorem IsIntegralClosure.isLocalization_of_isSeparable [IsSeparable K L] :
IsLocalization (Algebra.algebraMapSubmonoid C A⁰) L :=
IsIntegralClosure.isLocalization A K L C
#align is_integral_closure.is_localization IsIntegralClosure.isLocalization_of_isSeparable
variable [FiniteDimensional K L]
variable {A K L}
theorem IsIntegralClosure.range_le_span_dualBasis [IsSeparable K L] {ι : Type*} [Fintype ι]
[DecidableEq ι] (b : Basis ι K L) (hb_int : ∀ i, IsIntegral A (b i)) [IsIntegrallyClosed A] :
LinearMap.range ((Algebra.linearMap C L).restrictScalars A) ≤
Submodule.span A (Set.range <| (traceForm K L).dualBasis (traceForm_nondegenerate K L) b) := by
rw [← LinearMap.BilinForm.dualSubmodule_span_of_basis,
← LinearMap.BilinForm.le_flip_dualSubmodule, Submodule.span_le]
rintro _ ⟨i, rfl⟩ _ ⟨y, rfl⟩
simp only [LinearMap.coe_restrictScalars, linearMap_apply, LinearMap.BilinForm.flip_apply,
traceForm_apply]
refine IsIntegrallyClosed.isIntegral_iff.mp ?_
exact isIntegral_trace ((IsIntegralClosure.isIntegral A L y).algebraMap.mul (hb_int i))
#align is_integral_closure.range_le_span_dual_basis IsIntegralClosure.range_le_span_dualBasis
theorem integralClosure_le_span_dualBasis [IsSeparable K L] {ι : Type*} [Fintype ι] [DecidableEq ι]
(b : Basis ι K L) (hb_int : ∀ i, IsIntegral A (b i)) [IsIntegrallyClosed A] :
Subalgebra.toSubmodule (integralClosure A L) ≤
Submodule.span A (Set.range <| (traceForm K L).dualBasis (traceForm_nondegenerate K L) b) := by
refine le_trans ?_ (IsIntegralClosure.range_le_span_dualBasis (integralClosure A L) b hb_int)
intro x hx
exact ⟨⟨x, hx⟩, rfl⟩
#align integral_closure_le_span_dual_basis integralClosure_le_span_dualBasis
variable (A K)
theorem exists_integral_multiples (s : Finset L) :
∃ y ≠ (0 : A), ∀ x ∈ s, IsIntegral A (y • x) := by
haveI := Classical.decEq L
refine s.induction ?_ ?_
· use 1, one_ne_zero
rintro x ⟨⟩
· rintro x s hx ⟨y, hy, hs⟩
have := exists_integral_multiple
((IsFractionRing.isAlgebraic_iff A K L).mpr (.of_finite _ x))
((injective_iff_map_eq_zero (algebraMap A L)).mp ?_)
· rcases this with ⟨x', y', hy', hx'⟩
refine ⟨y * y', mul_ne_zero hy hy', fun x'' hx'' => ?_⟩
rcases Finset.mem_insert.mp hx'' with (rfl | hx'')
· rw [mul_smul, Algebra.smul_def, Algebra.smul_def, mul_comm _ x'', hx']
exact isIntegral_algebraMap.mul x'.2
· rw [mul_comm, mul_smul, Algebra.smul_def]
exact isIntegral_algebraMap.mul (hs _ hx'')
· rw [IsScalarTower.algebraMap_eq A K L]
apply (algebraMap K L).injective.comp
exact IsFractionRing.injective _ _
#align exists_integral_multiples exists_integral_multiples
variable (L)
| Mathlib/RingTheory/DedekindDomain/IntegralClosure.lean | 145 | 167 | theorem FiniteDimensional.exists_is_basis_integral :
∃ (s : Finset L) (b : Basis s K L), ∀ x, IsIntegral A (b x) := by |
letI := Classical.decEq L
letI : IsNoetherian K L := IsNoetherian.iff_fg.2 inferInstance
let s' := IsNoetherian.finsetBasisIndex K L
let bs' := IsNoetherian.finsetBasis K L
obtain ⟨y, hy, his'⟩ := exists_integral_multiples A K (Finset.univ.image bs')
have hy' : algebraMap A L y ≠ 0 := by
refine mt ((injective_iff_map_eq_zero (algebraMap A L)).mp ?_ _) hy
rw [IsScalarTower.algebraMap_eq A K L]
exact (algebraMap K L).injective.comp (IsFractionRing.injective A K)
refine ⟨s', bs'.map {Algebra.lmul _ _ (algebraMap A L y) with
toFun := fun x => algebraMap A L y * x
invFun := fun x => (algebraMap A L y)⁻¹ * x
left_inv := ?_
right_inv := ?_}, ?_⟩
· intro x; simp only [inv_mul_cancel_left₀ hy']
· intro x; simp only [mul_inv_cancel_left₀ hy']
· rintro ⟨x', hx'⟩
simp only [Algebra.smul_def, Finset.mem_image, exists_prop, Finset.mem_univ,
true_and_iff] at his'
simp only [Basis.map_apply, LinearEquiv.coe_mk]
exact his' _ ⟨_, rfl⟩
| 2,039 |
import Mathlib.Algebra.Order.Group.TypeTags
import Mathlib.FieldTheory.RatFunc.Degree
import Mathlib.RingTheory.DedekindDomain.IntegralClosure
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.Topology.Algebra.ValuedField
#align_import number_theory.function_field from "leanprover-community/mathlib"@"70fd9563a21e7b963887c9360bd29b2393e6225a"
noncomputable section
open scoped nonZeroDivisors Polynomial DiscreteValuation
variable (Fq F : Type) [Field Fq] [Field F]
abbrev FunctionField [Algebra (RatFunc Fq) F] : Prop :=
FiniteDimensional (RatFunc Fq) F
#align function_field FunctionField
-- Porting note: Removed `protected`
| Mathlib/NumberTheory/FunctionField.lean | 62 | 80 | theorem functionField_iff (Fqt : Type*) [Field Fqt] [Algebra Fq[X] Fqt]
[IsFractionRing Fq[X] Fqt] [Algebra (RatFunc Fq) F] [Algebra Fqt F] [Algebra Fq[X] F]
[IsScalarTower Fq[X] Fqt F] [IsScalarTower Fq[X] (RatFunc Fq) F] :
FunctionField Fq F ↔ FiniteDimensional Fqt F := by |
let e := IsLocalization.algEquiv Fq[X]⁰ (RatFunc Fq) Fqt
have : ∀ (c) (x : F), e c • x = c • x := by
intro c x
rw [Algebra.smul_def, Algebra.smul_def]
congr
refine congr_fun (f := fun c => algebraMap Fqt F (e c)) ?_ c -- Porting note: Added `(f := _)`
refine IsLocalization.ext (nonZeroDivisors Fq[X]) _ _ ?_ ?_ ?_ ?_ ?_ <;> intros <;>
simp only [AlgEquiv.map_one, RingHom.map_one, AlgEquiv.map_mul, RingHom.map_mul,
AlgEquiv.commutes, ← IsScalarTower.algebraMap_apply]
constructor <;> intro h
· let b := FiniteDimensional.finBasis (RatFunc Fq) F
exact FiniteDimensional.of_fintype_basis (b.mapCoeffs e this)
· let b := FiniteDimensional.finBasis Fqt F
refine FiniteDimensional.of_fintype_basis (b.mapCoeffs e.symm ?_)
intro c x; convert (this (e.symm c) x).symm; simp only [e.apply_symm_apply]
| 2,040 |
import Mathlib.Algebra.Order.Group.TypeTags
import Mathlib.FieldTheory.RatFunc.Degree
import Mathlib.RingTheory.DedekindDomain.IntegralClosure
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.Topology.Algebra.ValuedField
#align_import number_theory.function_field from "leanprover-community/mathlib"@"70fd9563a21e7b963887c9360bd29b2393e6225a"
noncomputable section
open scoped nonZeroDivisors Polynomial DiscreteValuation
variable (Fq F : Type) [Field Fq] [Field F]
abbrev FunctionField [Algebra (RatFunc Fq) F] : Prop :=
FiniteDimensional (RatFunc Fq) F
#align function_field FunctionField
-- Porting note: Removed `protected`
theorem functionField_iff (Fqt : Type*) [Field Fqt] [Algebra Fq[X] Fqt]
[IsFractionRing Fq[X] Fqt] [Algebra (RatFunc Fq) F] [Algebra Fqt F] [Algebra Fq[X] F]
[IsScalarTower Fq[X] Fqt F] [IsScalarTower Fq[X] (RatFunc Fq) F] :
FunctionField Fq F ↔ FiniteDimensional Fqt F := by
let e := IsLocalization.algEquiv Fq[X]⁰ (RatFunc Fq) Fqt
have : ∀ (c) (x : F), e c • x = c • x := by
intro c x
rw [Algebra.smul_def, Algebra.smul_def]
congr
refine congr_fun (f := fun c => algebraMap Fqt F (e c)) ?_ c -- Porting note: Added `(f := _)`
refine IsLocalization.ext (nonZeroDivisors Fq[X]) _ _ ?_ ?_ ?_ ?_ ?_ <;> intros <;>
simp only [AlgEquiv.map_one, RingHom.map_one, AlgEquiv.map_mul, RingHom.map_mul,
AlgEquiv.commutes, ← IsScalarTower.algebraMap_apply]
constructor <;> intro h
· let b := FiniteDimensional.finBasis (RatFunc Fq) F
exact FiniteDimensional.of_fintype_basis (b.mapCoeffs e this)
· let b := FiniteDimensional.finBasis Fqt F
refine FiniteDimensional.of_fintype_basis (b.mapCoeffs e.symm ?_)
intro c x; convert (this (e.symm c) x).symm; simp only [e.apply_symm_apply]
#align function_field_iff functionField_iff
| Mathlib/NumberTheory/FunctionField.lean | 83 | 86 | theorem algebraMap_injective [Algebra Fq[X] F] [Algebra (RatFunc Fq) F]
[IsScalarTower Fq[X] (RatFunc Fq) F] : Function.Injective (⇑(algebraMap Fq[X] F)) := by |
rw [IsScalarTower.algebraMap_eq Fq[X] (RatFunc Fq) F]
exact (algebraMap (RatFunc Fq) F).injective.comp (IsFractionRing.injective Fq[X] (RatFunc Fq))
| 2,040 |
import Mathlib.Algebra.Order.Group.TypeTags
import Mathlib.FieldTheory.RatFunc.Degree
import Mathlib.RingTheory.DedekindDomain.IntegralClosure
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.Topology.Algebra.ValuedField
#align_import number_theory.function_field from "leanprover-community/mathlib"@"70fd9563a21e7b963887c9360bd29b2393e6225a"
noncomputable section
open scoped nonZeroDivisors Polynomial DiscreteValuation
variable (Fq F : Type) [Field Fq] [Field F]
abbrev FunctionField [Algebra (RatFunc Fq) F] : Prop :=
FiniteDimensional (RatFunc Fq) F
#align function_field FunctionField
-- Porting note: Removed `protected`
theorem functionField_iff (Fqt : Type*) [Field Fqt] [Algebra Fq[X] Fqt]
[IsFractionRing Fq[X] Fqt] [Algebra (RatFunc Fq) F] [Algebra Fqt F] [Algebra Fq[X] F]
[IsScalarTower Fq[X] Fqt F] [IsScalarTower Fq[X] (RatFunc Fq) F] :
FunctionField Fq F ↔ FiniteDimensional Fqt F := by
let e := IsLocalization.algEquiv Fq[X]⁰ (RatFunc Fq) Fqt
have : ∀ (c) (x : F), e c • x = c • x := by
intro c x
rw [Algebra.smul_def, Algebra.smul_def]
congr
refine congr_fun (f := fun c => algebraMap Fqt F (e c)) ?_ c -- Porting note: Added `(f := _)`
refine IsLocalization.ext (nonZeroDivisors Fq[X]) _ _ ?_ ?_ ?_ ?_ ?_ <;> intros <;>
simp only [AlgEquiv.map_one, RingHom.map_one, AlgEquiv.map_mul, RingHom.map_mul,
AlgEquiv.commutes, ← IsScalarTower.algebraMap_apply]
constructor <;> intro h
· let b := FiniteDimensional.finBasis (RatFunc Fq) F
exact FiniteDimensional.of_fintype_basis (b.mapCoeffs e this)
· let b := FiniteDimensional.finBasis Fqt F
refine FiniteDimensional.of_fintype_basis (b.mapCoeffs e.symm ?_)
intro c x; convert (this (e.symm c) x).symm; simp only [e.apply_symm_apply]
#align function_field_iff functionField_iff
theorem algebraMap_injective [Algebra Fq[X] F] [Algebra (RatFunc Fq) F]
[IsScalarTower Fq[X] (RatFunc Fq) F] : Function.Injective (⇑(algebraMap Fq[X] F)) := by
rw [IsScalarTower.algebraMap_eq Fq[X] (RatFunc Fq) F]
exact (algebraMap (RatFunc Fq) F).injective.comp (IsFractionRing.injective Fq[X] (RatFunc Fq))
#align algebra_map_injective algebraMap_injective
namespace FunctionField
def ringOfIntegers [Algebra Fq[X] F] :=
integralClosure Fq[X] F
#align function_field.ring_of_integers FunctionField.ringOfIntegers
namespace ringOfIntegers
variable [Algebra Fq[X] F]
instance : IsDomain (ringOfIntegers Fq F) :=
(ringOfIntegers Fq F).isDomain
instance : IsIntegralClosure (ringOfIntegers Fq F) Fq[X] F :=
integralClosure.isIntegralClosure _ _
variable [Algebra (RatFunc Fq) F] [IsScalarTower Fq[X] (RatFunc Fq) F]
| Mathlib/NumberTheory/FunctionField.lean | 113 | 121 | theorem algebraMap_injective : Function.Injective (⇑(algebraMap Fq[X] (ringOfIntegers Fq F))) := by |
have hinj : Function.Injective (⇑(algebraMap Fq[X] F)) := by
rw [IsScalarTower.algebraMap_eq Fq[X] (RatFunc Fq) F]
exact (algebraMap (RatFunc Fq) F).injective.comp (IsFractionRing.injective Fq[X] (RatFunc Fq))
rw [injective_iff_map_eq_zero (algebraMap Fq[X] (↥(ringOfIntegers Fq F)))]
intro p hp
rw [← Subtype.coe_inj, Subalgebra.coe_zero] at hp
rw [injective_iff_map_eq_zero (algebraMap Fq[X] F)] at hinj
exact hinj p hp
| 2,040 |
import Mathlib.Algebra.Order.Group.TypeTags
import Mathlib.FieldTheory.RatFunc.Degree
import Mathlib.RingTheory.DedekindDomain.IntegralClosure
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.Topology.Algebra.ValuedField
#align_import number_theory.function_field from "leanprover-community/mathlib"@"70fd9563a21e7b963887c9360bd29b2393e6225a"
noncomputable section
open scoped nonZeroDivisors Polynomial DiscreteValuation
variable (Fq F : Type) [Field Fq] [Field F]
abbrev FunctionField [Algebra (RatFunc Fq) F] : Prop :=
FiniteDimensional (RatFunc Fq) F
#align function_field FunctionField
-- Porting note: Removed `protected`
theorem functionField_iff (Fqt : Type*) [Field Fqt] [Algebra Fq[X] Fqt]
[IsFractionRing Fq[X] Fqt] [Algebra (RatFunc Fq) F] [Algebra Fqt F] [Algebra Fq[X] F]
[IsScalarTower Fq[X] Fqt F] [IsScalarTower Fq[X] (RatFunc Fq) F] :
FunctionField Fq F ↔ FiniteDimensional Fqt F := by
let e := IsLocalization.algEquiv Fq[X]⁰ (RatFunc Fq) Fqt
have : ∀ (c) (x : F), e c • x = c • x := by
intro c x
rw [Algebra.smul_def, Algebra.smul_def]
congr
refine congr_fun (f := fun c => algebraMap Fqt F (e c)) ?_ c -- Porting note: Added `(f := _)`
refine IsLocalization.ext (nonZeroDivisors Fq[X]) _ _ ?_ ?_ ?_ ?_ ?_ <;> intros <;>
simp only [AlgEquiv.map_one, RingHom.map_one, AlgEquiv.map_mul, RingHom.map_mul,
AlgEquiv.commutes, ← IsScalarTower.algebraMap_apply]
constructor <;> intro h
· let b := FiniteDimensional.finBasis (RatFunc Fq) F
exact FiniteDimensional.of_fintype_basis (b.mapCoeffs e this)
· let b := FiniteDimensional.finBasis Fqt F
refine FiniteDimensional.of_fintype_basis (b.mapCoeffs e.symm ?_)
intro c x; convert (this (e.symm c) x).symm; simp only [e.apply_symm_apply]
#align function_field_iff functionField_iff
theorem algebraMap_injective [Algebra Fq[X] F] [Algebra (RatFunc Fq) F]
[IsScalarTower Fq[X] (RatFunc Fq) F] : Function.Injective (⇑(algebraMap Fq[X] F)) := by
rw [IsScalarTower.algebraMap_eq Fq[X] (RatFunc Fq) F]
exact (algebraMap (RatFunc Fq) F).injective.comp (IsFractionRing.injective Fq[X] (RatFunc Fq))
#align algebra_map_injective algebraMap_injective
namespace FunctionField
def ringOfIntegers [Algebra Fq[X] F] :=
integralClosure Fq[X] F
#align function_field.ring_of_integers FunctionField.ringOfIntegers
namespace ringOfIntegers
variable [Algebra Fq[X] F]
instance : IsDomain (ringOfIntegers Fq F) :=
(ringOfIntegers Fq F).isDomain
instance : IsIntegralClosure (ringOfIntegers Fq F) Fq[X] F :=
integralClosure.isIntegralClosure _ _
variable [Algebra (RatFunc Fq) F] [IsScalarTower Fq[X] (RatFunc Fq) F]
theorem algebraMap_injective : Function.Injective (⇑(algebraMap Fq[X] (ringOfIntegers Fq F))) := by
have hinj : Function.Injective (⇑(algebraMap Fq[X] F)) := by
rw [IsScalarTower.algebraMap_eq Fq[X] (RatFunc Fq) F]
exact (algebraMap (RatFunc Fq) F).injective.comp (IsFractionRing.injective Fq[X] (RatFunc Fq))
rw [injective_iff_map_eq_zero (algebraMap Fq[X] (↥(ringOfIntegers Fq F)))]
intro p hp
rw [← Subtype.coe_inj, Subalgebra.coe_zero] at hp
rw [injective_iff_map_eq_zero (algebraMap Fq[X] F)] at hinj
exact hinj p hp
#align function_field.ring_of_integers.algebra_map_injective FunctionField.ringOfIntegers.algebraMap_injective
| Mathlib/NumberTheory/FunctionField.lean | 124 | 127 | theorem not_isField : ¬IsField (ringOfIntegers Fq F) := by |
simpa [← (IsIntegralClosure.isIntegral_algebra Fq[X] F).isField_iff_isField
(algebraMap_injective Fq F)] using
Polynomial.not_isField Fq
| 2,040 |
import Mathlib.Algebra.Order.Group.TypeTags
import Mathlib.FieldTheory.RatFunc.Degree
import Mathlib.RingTheory.DedekindDomain.IntegralClosure
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.Topology.Algebra.ValuedField
#align_import number_theory.function_field from "leanprover-community/mathlib"@"70fd9563a21e7b963887c9360bd29b2393e6225a"
noncomputable section
open scoped nonZeroDivisors Polynomial DiscreteValuation
variable (Fq F : Type) [Field Fq] [Field F]
abbrev FunctionField [Algebra (RatFunc Fq) F] : Prop :=
FiniteDimensional (RatFunc Fq) F
#align function_field FunctionField
-- Porting note: Removed `protected`
theorem functionField_iff (Fqt : Type*) [Field Fqt] [Algebra Fq[X] Fqt]
[IsFractionRing Fq[X] Fqt] [Algebra (RatFunc Fq) F] [Algebra Fqt F] [Algebra Fq[X] F]
[IsScalarTower Fq[X] Fqt F] [IsScalarTower Fq[X] (RatFunc Fq) F] :
FunctionField Fq F ↔ FiniteDimensional Fqt F := by
let e := IsLocalization.algEquiv Fq[X]⁰ (RatFunc Fq) Fqt
have : ∀ (c) (x : F), e c • x = c • x := by
intro c x
rw [Algebra.smul_def, Algebra.smul_def]
congr
refine congr_fun (f := fun c => algebraMap Fqt F (e c)) ?_ c -- Porting note: Added `(f := _)`
refine IsLocalization.ext (nonZeroDivisors Fq[X]) _ _ ?_ ?_ ?_ ?_ ?_ <;> intros <;>
simp only [AlgEquiv.map_one, RingHom.map_one, AlgEquiv.map_mul, RingHom.map_mul,
AlgEquiv.commutes, ← IsScalarTower.algebraMap_apply]
constructor <;> intro h
· let b := FiniteDimensional.finBasis (RatFunc Fq) F
exact FiniteDimensional.of_fintype_basis (b.mapCoeffs e this)
· let b := FiniteDimensional.finBasis Fqt F
refine FiniteDimensional.of_fintype_basis (b.mapCoeffs e.symm ?_)
intro c x; convert (this (e.symm c) x).symm; simp only [e.apply_symm_apply]
#align function_field_iff functionField_iff
theorem algebraMap_injective [Algebra Fq[X] F] [Algebra (RatFunc Fq) F]
[IsScalarTower Fq[X] (RatFunc Fq) F] : Function.Injective (⇑(algebraMap Fq[X] F)) := by
rw [IsScalarTower.algebraMap_eq Fq[X] (RatFunc Fq) F]
exact (algebraMap (RatFunc Fq) F).injective.comp (IsFractionRing.injective Fq[X] (RatFunc Fq))
#align algebra_map_injective algebraMap_injective
namespace FunctionField
def ringOfIntegers [Algebra Fq[X] F] :=
integralClosure Fq[X] F
#align function_field.ring_of_integers FunctionField.ringOfIntegers
section InftyValuation
variable [DecidableEq (RatFunc Fq)]
def inftyValuationDef (r : RatFunc Fq) : ℤₘ₀ :=
if r = 0 then 0 else ↑(Multiplicative.ofAdd r.intDegree)
#align function_field.infty_valuation_def FunctionField.inftyValuationDef
theorem InftyValuation.map_zero' : inftyValuationDef Fq 0 = 0 :=
if_pos rfl
#align function_field.infty_valuation.map_zero' FunctionField.InftyValuation.map_zero'
theorem InftyValuation.map_one' : inftyValuationDef Fq 1 = 1 :=
(if_neg one_ne_zero).trans <| by rw [RatFunc.intDegree_one, ofAdd_zero, WithZero.coe_one]
#align function_field.infty_valuation.map_one' FunctionField.InftyValuation.map_one'
| Mathlib/NumberTheory/FunctionField.lean | 168 | 176 | theorem InftyValuation.map_mul' (x y : RatFunc Fq) :
inftyValuationDef Fq (x * y) = inftyValuationDef Fq x * inftyValuationDef Fq y := by |
rw [inftyValuationDef, inftyValuationDef, inftyValuationDef]
by_cases hx : x = 0
· rw [hx, zero_mul, if_pos (Eq.refl _), zero_mul]
· by_cases hy : y = 0
· rw [hy, mul_zero, if_pos (Eq.refl _), mul_zero]
· rw [if_neg hx, if_neg hy, if_neg (mul_ne_zero hx hy), ← WithZero.coe_mul, WithZero.coe_inj,
← ofAdd_add, RatFunc.intDegree_mul hx hy]
| 2,040 |
import Mathlib.Algebra.Order.Group.TypeTags
import Mathlib.FieldTheory.RatFunc.Degree
import Mathlib.RingTheory.DedekindDomain.IntegralClosure
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.Topology.Algebra.ValuedField
#align_import number_theory.function_field from "leanprover-community/mathlib"@"70fd9563a21e7b963887c9360bd29b2393e6225a"
noncomputable section
open scoped nonZeroDivisors Polynomial DiscreteValuation
variable (Fq F : Type) [Field Fq] [Field F]
abbrev FunctionField [Algebra (RatFunc Fq) F] : Prop :=
FiniteDimensional (RatFunc Fq) F
#align function_field FunctionField
-- Porting note: Removed `protected`
theorem functionField_iff (Fqt : Type*) [Field Fqt] [Algebra Fq[X] Fqt]
[IsFractionRing Fq[X] Fqt] [Algebra (RatFunc Fq) F] [Algebra Fqt F] [Algebra Fq[X] F]
[IsScalarTower Fq[X] Fqt F] [IsScalarTower Fq[X] (RatFunc Fq) F] :
FunctionField Fq F ↔ FiniteDimensional Fqt F := by
let e := IsLocalization.algEquiv Fq[X]⁰ (RatFunc Fq) Fqt
have : ∀ (c) (x : F), e c • x = c • x := by
intro c x
rw [Algebra.smul_def, Algebra.smul_def]
congr
refine congr_fun (f := fun c => algebraMap Fqt F (e c)) ?_ c -- Porting note: Added `(f := _)`
refine IsLocalization.ext (nonZeroDivisors Fq[X]) _ _ ?_ ?_ ?_ ?_ ?_ <;> intros <;>
simp only [AlgEquiv.map_one, RingHom.map_one, AlgEquiv.map_mul, RingHom.map_mul,
AlgEquiv.commutes, ← IsScalarTower.algebraMap_apply]
constructor <;> intro h
· let b := FiniteDimensional.finBasis (RatFunc Fq) F
exact FiniteDimensional.of_fintype_basis (b.mapCoeffs e this)
· let b := FiniteDimensional.finBasis Fqt F
refine FiniteDimensional.of_fintype_basis (b.mapCoeffs e.symm ?_)
intro c x; convert (this (e.symm c) x).symm; simp only [e.apply_symm_apply]
#align function_field_iff functionField_iff
theorem algebraMap_injective [Algebra Fq[X] F] [Algebra (RatFunc Fq) F]
[IsScalarTower Fq[X] (RatFunc Fq) F] : Function.Injective (⇑(algebraMap Fq[X] F)) := by
rw [IsScalarTower.algebraMap_eq Fq[X] (RatFunc Fq) F]
exact (algebraMap (RatFunc Fq) F).injective.comp (IsFractionRing.injective Fq[X] (RatFunc Fq))
#align algebra_map_injective algebraMap_injective
namespace FunctionField
def ringOfIntegers [Algebra Fq[X] F] :=
integralClosure Fq[X] F
#align function_field.ring_of_integers FunctionField.ringOfIntegers
section InftyValuation
variable [DecidableEq (RatFunc Fq)]
def inftyValuationDef (r : RatFunc Fq) : ℤₘ₀ :=
if r = 0 then 0 else ↑(Multiplicative.ofAdd r.intDegree)
#align function_field.infty_valuation_def FunctionField.inftyValuationDef
theorem InftyValuation.map_zero' : inftyValuationDef Fq 0 = 0 :=
if_pos rfl
#align function_field.infty_valuation.map_zero' FunctionField.InftyValuation.map_zero'
theorem InftyValuation.map_one' : inftyValuationDef Fq 1 = 1 :=
(if_neg one_ne_zero).trans <| by rw [RatFunc.intDegree_one, ofAdd_zero, WithZero.coe_one]
#align function_field.infty_valuation.map_one' FunctionField.InftyValuation.map_one'
theorem InftyValuation.map_mul' (x y : RatFunc Fq) :
inftyValuationDef Fq (x * y) = inftyValuationDef Fq x * inftyValuationDef Fq y := by
rw [inftyValuationDef, inftyValuationDef, inftyValuationDef]
by_cases hx : x = 0
· rw [hx, zero_mul, if_pos (Eq.refl _), zero_mul]
· by_cases hy : y = 0
· rw [hy, mul_zero, if_pos (Eq.refl _), mul_zero]
· rw [if_neg hx, if_neg hy, if_neg (mul_ne_zero hx hy), ← WithZero.coe_mul, WithZero.coe_inj,
← ofAdd_add, RatFunc.intDegree_mul hx hy]
#align function_field.infty_valuation.map_mul' FunctionField.InftyValuation.map_mul'
| Mathlib/NumberTheory/FunctionField.lean | 179 | 195 | theorem InftyValuation.map_add_le_max' (x y : RatFunc Fq) :
inftyValuationDef Fq (x + y) ≤ max (inftyValuationDef Fq x) (inftyValuationDef Fq y) := by |
by_cases hx : x = 0
· rw [hx, zero_add]
conv_rhs => rw [inftyValuationDef, if_pos (Eq.refl _)]
rw [max_eq_right (WithZero.zero_le (inftyValuationDef Fq y))]
· by_cases hy : y = 0
· rw [hy, add_zero]
conv_rhs => rw [max_comm, inftyValuationDef, if_pos (Eq.refl _)]
rw [max_eq_right (WithZero.zero_le (inftyValuationDef Fq x))]
· by_cases hxy : x + y = 0
· rw [inftyValuationDef, if_pos hxy]; exact zero_le'
· rw [inftyValuationDef, inftyValuationDef, inftyValuationDef, if_neg hx, if_neg hy,
if_neg hxy]
rw [le_max_iff, WithZero.coe_le_coe, Multiplicative.ofAdd_le, WithZero.coe_le_coe,
Multiplicative.ofAdd_le, ← le_max_iff]
exact RatFunc.intDegree_add_le hy hxy
| 2,040 |
import Mathlib.Algebra.Order.Group.TypeTags
import Mathlib.FieldTheory.RatFunc.Degree
import Mathlib.RingTheory.DedekindDomain.IntegralClosure
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.Topology.Algebra.ValuedField
#align_import number_theory.function_field from "leanprover-community/mathlib"@"70fd9563a21e7b963887c9360bd29b2393e6225a"
noncomputable section
open scoped nonZeroDivisors Polynomial DiscreteValuation
variable (Fq F : Type) [Field Fq] [Field F]
abbrev FunctionField [Algebra (RatFunc Fq) F] : Prop :=
FiniteDimensional (RatFunc Fq) F
#align function_field FunctionField
-- Porting note: Removed `protected`
theorem functionField_iff (Fqt : Type*) [Field Fqt] [Algebra Fq[X] Fqt]
[IsFractionRing Fq[X] Fqt] [Algebra (RatFunc Fq) F] [Algebra Fqt F] [Algebra Fq[X] F]
[IsScalarTower Fq[X] Fqt F] [IsScalarTower Fq[X] (RatFunc Fq) F] :
FunctionField Fq F ↔ FiniteDimensional Fqt F := by
let e := IsLocalization.algEquiv Fq[X]⁰ (RatFunc Fq) Fqt
have : ∀ (c) (x : F), e c • x = c • x := by
intro c x
rw [Algebra.smul_def, Algebra.smul_def]
congr
refine congr_fun (f := fun c => algebraMap Fqt F (e c)) ?_ c -- Porting note: Added `(f := _)`
refine IsLocalization.ext (nonZeroDivisors Fq[X]) _ _ ?_ ?_ ?_ ?_ ?_ <;> intros <;>
simp only [AlgEquiv.map_one, RingHom.map_one, AlgEquiv.map_mul, RingHom.map_mul,
AlgEquiv.commutes, ← IsScalarTower.algebraMap_apply]
constructor <;> intro h
· let b := FiniteDimensional.finBasis (RatFunc Fq) F
exact FiniteDimensional.of_fintype_basis (b.mapCoeffs e this)
· let b := FiniteDimensional.finBasis Fqt F
refine FiniteDimensional.of_fintype_basis (b.mapCoeffs e.symm ?_)
intro c x; convert (this (e.symm c) x).symm; simp only [e.apply_symm_apply]
#align function_field_iff functionField_iff
theorem algebraMap_injective [Algebra Fq[X] F] [Algebra (RatFunc Fq) F]
[IsScalarTower Fq[X] (RatFunc Fq) F] : Function.Injective (⇑(algebraMap Fq[X] F)) := by
rw [IsScalarTower.algebraMap_eq Fq[X] (RatFunc Fq) F]
exact (algebraMap (RatFunc Fq) F).injective.comp (IsFractionRing.injective Fq[X] (RatFunc Fq))
#align algebra_map_injective algebraMap_injective
namespace FunctionField
def ringOfIntegers [Algebra Fq[X] F] :=
integralClosure Fq[X] F
#align function_field.ring_of_integers FunctionField.ringOfIntegers
section InftyValuation
variable [DecidableEq (RatFunc Fq)]
def inftyValuationDef (r : RatFunc Fq) : ℤₘ₀ :=
if r = 0 then 0 else ↑(Multiplicative.ofAdd r.intDegree)
#align function_field.infty_valuation_def FunctionField.inftyValuationDef
theorem InftyValuation.map_zero' : inftyValuationDef Fq 0 = 0 :=
if_pos rfl
#align function_field.infty_valuation.map_zero' FunctionField.InftyValuation.map_zero'
theorem InftyValuation.map_one' : inftyValuationDef Fq 1 = 1 :=
(if_neg one_ne_zero).trans <| by rw [RatFunc.intDegree_one, ofAdd_zero, WithZero.coe_one]
#align function_field.infty_valuation.map_one' FunctionField.InftyValuation.map_one'
theorem InftyValuation.map_mul' (x y : RatFunc Fq) :
inftyValuationDef Fq (x * y) = inftyValuationDef Fq x * inftyValuationDef Fq y := by
rw [inftyValuationDef, inftyValuationDef, inftyValuationDef]
by_cases hx : x = 0
· rw [hx, zero_mul, if_pos (Eq.refl _), zero_mul]
· by_cases hy : y = 0
· rw [hy, mul_zero, if_pos (Eq.refl _), mul_zero]
· rw [if_neg hx, if_neg hy, if_neg (mul_ne_zero hx hy), ← WithZero.coe_mul, WithZero.coe_inj,
← ofAdd_add, RatFunc.intDegree_mul hx hy]
#align function_field.infty_valuation.map_mul' FunctionField.InftyValuation.map_mul'
theorem InftyValuation.map_add_le_max' (x y : RatFunc Fq) :
inftyValuationDef Fq (x + y) ≤ max (inftyValuationDef Fq x) (inftyValuationDef Fq y) := by
by_cases hx : x = 0
· rw [hx, zero_add]
conv_rhs => rw [inftyValuationDef, if_pos (Eq.refl _)]
rw [max_eq_right (WithZero.zero_le (inftyValuationDef Fq y))]
· by_cases hy : y = 0
· rw [hy, add_zero]
conv_rhs => rw [max_comm, inftyValuationDef, if_pos (Eq.refl _)]
rw [max_eq_right (WithZero.zero_le (inftyValuationDef Fq x))]
· by_cases hxy : x + y = 0
· rw [inftyValuationDef, if_pos hxy]; exact zero_le'
· rw [inftyValuationDef, inftyValuationDef, inftyValuationDef, if_neg hx, if_neg hy,
if_neg hxy]
rw [le_max_iff, WithZero.coe_le_coe, Multiplicative.ofAdd_le, WithZero.coe_le_coe,
Multiplicative.ofAdd_le, ← le_max_iff]
exact RatFunc.intDegree_add_le hy hxy
#align function_field.infty_valuation.map_add_le_max' FunctionField.InftyValuation.map_add_le_max'
@[simp]
| Mathlib/NumberTheory/FunctionField.lean | 199 | 201 | theorem inftyValuation_of_nonzero {x : RatFunc Fq} (hx : x ≠ 0) :
inftyValuationDef Fq x = Multiplicative.ofAdd x.intDegree := by |
rw [inftyValuationDef, if_neg hx]
| 2,040 |
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
universe u v w
open scoped Classical Polynomial
open Polynomial
variable (k : Type u) [Field k] (K : Type v) [Field K]
class IsSepClosed : Prop where
splits_of_separable : ∀ p : k[X], p.Separable → (p.Splits <| RingHom.id k)
instance IsSepClosed.of_isAlgClosed [IsAlgClosed k] : IsSepClosed k :=
⟨fun p _ ↦ IsAlgClosed.splits p⟩
variable {k} {K}
| Mathlib/FieldTheory/IsSepClosed.lean | 78 | 80 | theorem IsSepClosed.splits_codomain [IsSepClosed K] {f : k →+* K}
(p : k[X]) (h : p.Separable) : p.Splits f := by |
convert IsSepClosed.splits_of_separable (p.map f) (Separable.map h); simp [splits_map_iff]
| 2,041 |
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
universe u v w
open scoped Classical Polynomial
open Polynomial
variable (k : Type u) [Field k] (K : Type v) [Field K]
class IsSepClosed : Prop where
splits_of_separable : ∀ p : k[X], p.Separable → (p.Splits <| RingHom.id k)
instance IsSepClosed.of_isAlgClosed [IsAlgClosed k] : IsSepClosed k :=
⟨fun p _ ↦ IsAlgClosed.splits p⟩
variable {k} {K}
theorem IsSepClosed.splits_codomain [IsSepClosed K] {f : k →+* K}
(p : k[X]) (h : p.Separable) : p.Splits f := by
convert IsSepClosed.splits_of_separable (p.map f) (Separable.map h); simp [splits_map_iff]
theorem IsSepClosed.splits_domain [IsSepClosed k] {f : k →+* K}
(p : k[X]) (h : p.Separable) : p.Splits f :=
Polynomial.splits_of_splits_id _ <| IsSepClosed.splits_of_separable _ h
namespace IsSepClosed
theorem exists_root [IsSepClosed k] (p : k[X]) (hp : p.degree ≠ 0) (hsep : p.Separable) :
∃ x, IsRoot p x :=
exists_root_of_splits _ (IsSepClosed.splits_of_separable p hsep) hp
variable (k) in
instance (priority := 100) isAlgClosed_of_perfectField [IsSepClosed k] [PerfectField k] :
IsAlgClosed k :=
IsAlgClosed.of_exists_root k fun p _ h ↦ exists_root p ((degree_pos_of_irreducible h).ne')
(PerfectField.separable_of_irreducible h)
| Mathlib/FieldTheory/IsSepClosed.lean | 104 | 116 | theorem exists_pow_nat_eq [IsSepClosed k] (x : k) (n : ℕ) [hn : NeZero (n : k)] :
∃ z, z ^ n = x := by |
have hn' : 0 < n := Nat.pos_of_ne_zero fun h => by
rw [h, Nat.cast_zero] at hn
exact hn.out rfl
have : degree (X ^ n - C x) ≠ 0 := by
rw [degree_X_pow_sub_C hn' x]
exact (WithBot.coe_lt_coe.2 hn').ne'
by_cases hx : x = 0
· exact ⟨0, by rw [hx, pow_eq_zero_iff hn'.ne']⟩
· obtain ⟨z, hz⟩ := exists_root _ this <| separable_X_pow_sub_C x hn.out hx
use z
simpa [eval_C, eval_X, eval_pow, eval_sub, IsRoot.def, sub_eq_zero] using hz
| 2,041 |
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
universe u v w
open scoped Classical Polynomial
open Polynomial
variable (k : Type u) [Field k] (K : Type v) [Field K]
class IsSepClosed : Prop where
splits_of_separable : ∀ p : k[X], p.Separable → (p.Splits <| RingHom.id k)
instance IsSepClosed.of_isAlgClosed [IsAlgClosed k] : IsSepClosed k :=
⟨fun p _ ↦ IsAlgClosed.splits p⟩
variable {k} {K}
theorem IsSepClosed.splits_codomain [IsSepClosed K] {f : k →+* K}
(p : k[X]) (h : p.Separable) : p.Splits f := by
convert IsSepClosed.splits_of_separable (p.map f) (Separable.map h); simp [splits_map_iff]
theorem IsSepClosed.splits_domain [IsSepClosed k] {f : k →+* K}
(p : k[X]) (h : p.Separable) : p.Splits f :=
Polynomial.splits_of_splits_id _ <| IsSepClosed.splits_of_separable _ h
namespace IsSepClosed
theorem exists_root [IsSepClosed k] (p : k[X]) (hp : p.degree ≠ 0) (hsep : p.Separable) :
∃ x, IsRoot p x :=
exists_root_of_splits _ (IsSepClosed.splits_of_separable p hsep) hp
variable (k) in
instance (priority := 100) isAlgClosed_of_perfectField [IsSepClosed k] [PerfectField k] :
IsAlgClosed k :=
IsAlgClosed.of_exists_root k fun p _ h ↦ exists_root p ((degree_pos_of_irreducible h).ne')
(PerfectField.separable_of_irreducible h)
theorem exists_pow_nat_eq [IsSepClosed k] (x : k) (n : ℕ) [hn : NeZero (n : k)] :
∃ z, z ^ n = x := by
have hn' : 0 < n := Nat.pos_of_ne_zero fun h => by
rw [h, Nat.cast_zero] at hn
exact hn.out rfl
have : degree (X ^ n - C x) ≠ 0 := by
rw [degree_X_pow_sub_C hn' x]
exact (WithBot.coe_lt_coe.2 hn').ne'
by_cases hx : x = 0
· exact ⟨0, by rw [hx, pow_eq_zero_iff hn'.ne']⟩
· obtain ⟨z, hz⟩ := exists_root _ this <| separable_X_pow_sub_C x hn.out hx
use z
simpa [eval_C, eval_X, eval_pow, eval_sub, IsRoot.def, sub_eq_zero] using hz
| Mathlib/FieldTheory/IsSepClosed.lean | 118 | 120 | theorem exists_eq_mul_self [IsSepClosed k] (x : k) [h2 : NeZero (2 : k)] : ∃ z, x = z * z := by |
rcases exists_pow_nat_eq x 2 with ⟨z, rfl⟩
exact ⟨z, sq z⟩
| 2,041 |
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
universe u v w
open scoped Classical Polynomial
open Polynomial
variable (k : Type u) [Field k] (K : Type v) [Field K]
class IsSepClosed : Prop where
splits_of_separable : ∀ p : k[X], p.Separable → (p.Splits <| RingHom.id k)
instance IsSepClosed.of_isAlgClosed [IsAlgClosed k] : IsSepClosed k :=
⟨fun p _ ↦ IsAlgClosed.splits p⟩
variable {k} {K}
theorem IsSepClosed.splits_codomain [IsSepClosed K] {f : k →+* K}
(p : k[X]) (h : p.Separable) : p.Splits f := by
convert IsSepClosed.splits_of_separable (p.map f) (Separable.map h); simp [splits_map_iff]
theorem IsSepClosed.splits_domain [IsSepClosed k] {f : k →+* K}
(p : k[X]) (h : p.Separable) : p.Splits f :=
Polynomial.splits_of_splits_id _ <| IsSepClosed.splits_of_separable _ h
namespace IsSepClosed
theorem exists_root [IsSepClosed k] (p : k[X]) (hp : p.degree ≠ 0) (hsep : p.Separable) :
∃ x, IsRoot p x :=
exists_root_of_splits _ (IsSepClosed.splits_of_separable p hsep) hp
variable (k) in
instance (priority := 100) isAlgClosed_of_perfectField [IsSepClosed k] [PerfectField k] :
IsAlgClosed k :=
IsAlgClosed.of_exists_root k fun p _ h ↦ exists_root p ((degree_pos_of_irreducible h).ne')
(PerfectField.separable_of_irreducible h)
theorem exists_pow_nat_eq [IsSepClosed k] (x : k) (n : ℕ) [hn : NeZero (n : k)] :
∃ z, z ^ n = x := by
have hn' : 0 < n := Nat.pos_of_ne_zero fun h => by
rw [h, Nat.cast_zero] at hn
exact hn.out rfl
have : degree (X ^ n - C x) ≠ 0 := by
rw [degree_X_pow_sub_C hn' x]
exact (WithBot.coe_lt_coe.2 hn').ne'
by_cases hx : x = 0
· exact ⟨0, by rw [hx, pow_eq_zero_iff hn'.ne']⟩
· obtain ⟨z, hz⟩ := exists_root _ this <| separable_X_pow_sub_C x hn.out hx
use z
simpa [eval_C, eval_X, eval_pow, eval_sub, IsRoot.def, sub_eq_zero] using hz
theorem exists_eq_mul_self [IsSepClosed k] (x : k) [h2 : NeZero (2 : k)] : ∃ z, x = z * z := by
rcases exists_pow_nat_eq x 2 with ⟨z, rfl⟩
exact ⟨z, sq z⟩
| Mathlib/FieldTheory/IsSepClosed.lean | 122 | 129 | theorem roots_eq_zero_iff [IsSepClosed k] {p : k[X]} (hsep : p.Separable) :
p.roots = 0 ↔ p = Polynomial.C (p.coeff 0) := by |
refine ⟨fun h => ?_, fun hp => by rw [hp, roots_C]⟩
rcases le_or_lt (degree p) 0 with hd | hd
· exact eq_C_of_degree_le_zero hd
· obtain ⟨z, hz⟩ := IsSepClosed.exists_root p hd.ne' hsep
rw [← mem_roots (ne_zero_of_degree_gt hd), h] at hz
simp at hz
| 2,041 |
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
universe u v w
open scoped Classical Polynomial
open Polynomial
variable (k : Type u) [Field k] (K : Type v) [Field K]
class IsSepClosed : Prop where
splits_of_separable : ∀ p : k[X], p.Separable → (p.Splits <| RingHom.id k)
instance IsSepClosed.of_isAlgClosed [IsAlgClosed k] : IsSepClosed k :=
⟨fun p _ ↦ IsAlgClosed.splits p⟩
variable {k} {K}
theorem IsSepClosed.splits_codomain [IsSepClosed K] {f : k →+* K}
(p : k[X]) (h : p.Separable) : p.Splits f := by
convert IsSepClosed.splits_of_separable (p.map f) (Separable.map h); simp [splits_map_iff]
theorem IsSepClosed.splits_domain [IsSepClosed k] {f : k →+* K}
(p : k[X]) (h : p.Separable) : p.Splits f :=
Polynomial.splits_of_splits_id _ <| IsSepClosed.splits_of_separable _ h
namespace IsSepClosed
theorem exists_root [IsSepClosed k] (p : k[X]) (hp : p.degree ≠ 0) (hsep : p.Separable) :
∃ x, IsRoot p x :=
exists_root_of_splits _ (IsSepClosed.splits_of_separable p hsep) hp
variable (k) in
instance (priority := 100) isAlgClosed_of_perfectField [IsSepClosed k] [PerfectField k] :
IsAlgClosed k :=
IsAlgClosed.of_exists_root k fun p _ h ↦ exists_root p ((degree_pos_of_irreducible h).ne')
(PerfectField.separable_of_irreducible h)
theorem exists_pow_nat_eq [IsSepClosed k] (x : k) (n : ℕ) [hn : NeZero (n : k)] :
∃ z, z ^ n = x := by
have hn' : 0 < n := Nat.pos_of_ne_zero fun h => by
rw [h, Nat.cast_zero] at hn
exact hn.out rfl
have : degree (X ^ n - C x) ≠ 0 := by
rw [degree_X_pow_sub_C hn' x]
exact (WithBot.coe_lt_coe.2 hn').ne'
by_cases hx : x = 0
· exact ⟨0, by rw [hx, pow_eq_zero_iff hn'.ne']⟩
· obtain ⟨z, hz⟩ := exists_root _ this <| separable_X_pow_sub_C x hn.out hx
use z
simpa [eval_C, eval_X, eval_pow, eval_sub, IsRoot.def, sub_eq_zero] using hz
theorem exists_eq_mul_self [IsSepClosed k] (x : k) [h2 : NeZero (2 : k)] : ∃ z, x = z * z := by
rcases exists_pow_nat_eq x 2 with ⟨z, rfl⟩
exact ⟨z, sq z⟩
theorem roots_eq_zero_iff [IsSepClosed k] {p : k[X]} (hsep : p.Separable) :
p.roots = 0 ↔ p = Polynomial.C (p.coeff 0) := by
refine ⟨fun h => ?_, fun hp => by rw [hp, roots_C]⟩
rcases le_or_lt (degree p) 0 with hd | hd
· exact eq_C_of_degree_le_zero hd
· obtain ⟨z, hz⟩ := IsSepClosed.exists_root p hd.ne' hsep
rw [← mem_roots (ne_zero_of_degree_gt hd), h] at hz
simp at hz
theorem exists_eval₂_eq_zero [IsSepClosed K] (f : k →+* K)
(p : k[X]) (hp : p.degree ≠ 0) (hsep : p.Separable) :
∃ x, p.eval₂ f x = 0 :=
let ⟨x, hx⟩ := exists_root (p.map f) (by rwa [degree_map_eq_of_injective f.injective])
(Separable.map hsep)
⟨x, by rwa [eval₂_eq_eval_map, ← IsRoot]⟩
variable (K)
theorem exists_aeval_eq_zero [IsSepClosed K] [Algebra k K] (p : k[X])
(hp : p.degree ≠ 0) (hsep : p.Separable) : ∃ x : K, aeval x p = 0 :=
exists_eval₂_eq_zero (algebraMap k K) p hp hsep
variable (k) {K}
| Mathlib/FieldTheory/IsSepClosed.lean | 146 | 160 | theorem of_exists_root (H : ∀ p : k[X], p.Monic → Irreducible p → Separable p → ∃ x, p.eval x = 0) :
IsSepClosed k := by |
refine ⟨fun p hsep ↦ Or.inr ?_⟩
intro q hq hdvd
simp only [map_id] at hdvd
have hlc : IsUnit (leadingCoeff q)⁻¹ := IsUnit.inv <| Ne.isUnit <|
leadingCoeff_ne_zero.2 <| Irreducible.ne_zero hq
have hsep' : Separable (q * C (leadingCoeff q)⁻¹) :=
Separable.mul (Separable.of_dvd hsep hdvd) ((separable_C _).2 hlc)
(by simpa only [← isCoprime_mul_unit_right_right (isUnit_C.2 hlc) q 1, one_mul]
using isCoprime_one_right (x := q))
have hirr' := hq
rw [← irreducible_mul_isUnit (isUnit_C.2 hlc)] at hirr'
obtain ⟨x, hx⟩ := H (q * C (leadingCoeff q)⁻¹) (monic_mul_leadingCoeff_inv hq.ne_zero) hirr' hsep'
exact degree_mul_leadingCoeff_inv q hq.ne_zero ▸ degree_eq_one_of_irreducible_of_root hirr' hx
| 2,041 |
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
universe u v w
open scoped Classical Polynomial
open Polynomial
variable (k : Type u) [Field k] (K : Type v) [Field K]
class IsSepClosed : Prop where
splits_of_separable : ∀ p : k[X], p.Separable → (p.Splits <| RingHom.id k)
instance IsSepClosed.of_isAlgClosed [IsAlgClosed k] : IsSepClosed k :=
⟨fun p _ ↦ IsAlgClosed.splits p⟩
variable {k} {K}
theorem IsSepClosed.splits_codomain [IsSepClosed K] {f : k →+* K}
(p : k[X]) (h : p.Separable) : p.Splits f := by
convert IsSepClosed.splits_of_separable (p.map f) (Separable.map h); simp [splits_map_iff]
theorem IsSepClosed.splits_domain [IsSepClosed k] {f : k →+* K}
(p : k[X]) (h : p.Separable) : p.Splits f :=
Polynomial.splits_of_splits_id _ <| IsSepClosed.splits_of_separable _ h
namespace IsSepClosed
theorem exists_root [IsSepClosed k] (p : k[X]) (hp : p.degree ≠ 0) (hsep : p.Separable) :
∃ x, IsRoot p x :=
exists_root_of_splits _ (IsSepClosed.splits_of_separable p hsep) hp
variable (k) in
instance (priority := 100) isAlgClosed_of_perfectField [IsSepClosed k] [PerfectField k] :
IsAlgClosed k :=
IsAlgClosed.of_exists_root k fun p _ h ↦ exists_root p ((degree_pos_of_irreducible h).ne')
(PerfectField.separable_of_irreducible h)
theorem exists_pow_nat_eq [IsSepClosed k] (x : k) (n : ℕ) [hn : NeZero (n : k)] :
∃ z, z ^ n = x := by
have hn' : 0 < n := Nat.pos_of_ne_zero fun h => by
rw [h, Nat.cast_zero] at hn
exact hn.out rfl
have : degree (X ^ n - C x) ≠ 0 := by
rw [degree_X_pow_sub_C hn' x]
exact (WithBot.coe_lt_coe.2 hn').ne'
by_cases hx : x = 0
· exact ⟨0, by rw [hx, pow_eq_zero_iff hn'.ne']⟩
· obtain ⟨z, hz⟩ := exists_root _ this <| separable_X_pow_sub_C x hn.out hx
use z
simpa [eval_C, eval_X, eval_pow, eval_sub, IsRoot.def, sub_eq_zero] using hz
theorem exists_eq_mul_self [IsSepClosed k] (x : k) [h2 : NeZero (2 : k)] : ∃ z, x = z * z := by
rcases exists_pow_nat_eq x 2 with ⟨z, rfl⟩
exact ⟨z, sq z⟩
theorem roots_eq_zero_iff [IsSepClosed k] {p : k[X]} (hsep : p.Separable) :
p.roots = 0 ↔ p = Polynomial.C (p.coeff 0) := by
refine ⟨fun h => ?_, fun hp => by rw [hp, roots_C]⟩
rcases le_or_lt (degree p) 0 with hd | hd
· exact eq_C_of_degree_le_zero hd
· obtain ⟨z, hz⟩ := IsSepClosed.exists_root p hd.ne' hsep
rw [← mem_roots (ne_zero_of_degree_gt hd), h] at hz
simp at hz
theorem exists_eval₂_eq_zero [IsSepClosed K] (f : k →+* K)
(p : k[X]) (hp : p.degree ≠ 0) (hsep : p.Separable) :
∃ x, p.eval₂ f x = 0 :=
let ⟨x, hx⟩ := exists_root (p.map f) (by rwa [degree_map_eq_of_injective f.injective])
(Separable.map hsep)
⟨x, by rwa [eval₂_eq_eval_map, ← IsRoot]⟩
variable (K)
theorem exists_aeval_eq_zero [IsSepClosed K] [Algebra k K] (p : k[X])
(hp : p.degree ≠ 0) (hsep : p.Separable) : ∃ x : K, aeval x p = 0 :=
exists_eval₂_eq_zero (algebraMap k K) p hp hsep
variable (k) {K}
theorem of_exists_root (H : ∀ p : k[X], p.Monic → Irreducible p → Separable p → ∃ x, p.eval x = 0) :
IsSepClosed k := by
refine ⟨fun p hsep ↦ Or.inr ?_⟩
intro q hq hdvd
simp only [map_id] at hdvd
have hlc : IsUnit (leadingCoeff q)⁻¹ := IsUnit.inv <| Ne.isUnit <|
leadingCoeff_ne_zero.2 <| Irreducible.ne_zero hq
have hsep' : Separable (q * C (leadingCoeff q)⁻¹) :=
Separable.mul (Separable.of_dvd hsep hdvd) ((separable_C _).2 hlc)
(by simpa only [← isCoprime_mul_unit_right_right (isUnit_C.2 hlc) q 1, one_mul]
using isCoprime_one_right (x := q))
have hirr' := hq
rw [← irreducible_mul_isUnit (isUnit_C.2 hlc)] at hirr'
obtain ⟨x, hx⟩ := H (q * C (leadingCoeff q)⁻¹) (monic_mul_leadingCoeff_inv hq.ne_zero) hirr' hsep'
exact degree_mul_leadingCoeff_inv q hq.ne_zero ▸ degree_eq_one_of_irreducible_of_root hirr' hx
theorem degree_eq_one_of_irreducible [IsSepClosed k] {p : k[X]}
(hp : Irreducible p) (hsep : p.Separable) : p.degree = 1 :=
degree_eq_one_of_irreducible_of_splits hp (IsSepClosed.splits_codomain p hsep)
variable (K)
| Mathlib/FieldTheory/IsSepClosed.lean | 168 | 179 | theorem algebraMap_surjective
[IsSepClosed k] [Algebra k K] [IsSeparable k K] :
Function.Surjective (algebraMap k K) := by |
refine fun x => ⟨-(minpoly k x).coeff 0, ?_⟩
have hq : (minpoly k x).leadingCoeff = 1 := minpoly.monic (IsSeparable.isIntegral k x)
have hsep : (minpoly k x).Separable := IsSeparable.separable k x
have h : (minpoly k x).degree = 1 :=
degree_eq_one_of_irreducible k (minpoly.irreducible (IsSeparable.isIntegral k x)) hsep
have : aeval x (minpoly k x) = 0 := minpoly.aeval k x
rw [eq_X_add_C_of_degree_eq_one h, hq, C_1, one_mul, aeval_add, aeval_X, aeval_C,
add_eq_zero_iff_eq_neg] at this
exact (RingHom.map_neg (algebraMap k K) ((minpoly k x).coeff 0)).symm ▸ this.symm
| 2,041 |
import Mathlib.FieldTheory.SeparableDegree
import Mathlib.FieldTheory.IsSepClosed
open scoped Classical Polynomial
open FiniteDimensional Polynomial IntermediateField Field
noncomputable section
universe u v w
variable (F : Type u) (E : Type v) [Field F] [Field E] [Algebra F E]
variable (K : Type w) [Field K] [Algebra F K]
section separableClosure
def separableClosure : IntermediateField F E where
carrier := {x | (minpoly F x).Separable}
mul_mem' := separable_mul
add_mem' := separable_add
algebraMap_mem' := separable_algebraMap E
inv_mem' := separable_inv
variable {F E K}
theorem mem_separableClosure_iff {x : E} :
x ∈ separableClosure F E ↔ (minpoly F x).Separable := Iff.rfl
| Mathlib/FieldTheory/SeparableClosure.lean | 94 | 96 | theorem map_mem_separableClosure_iff (i : E →ₐ[F] K) {x : E} :
i x ∈ separableClosure F K ↔ x ∈ separableClosure F E := by |
simp_rw [mem_separableClosure_iff, minpoly.algHom_eq i i.injective]
| 2,042 |
import Mathlib.FieldTheory.SeparableDegree
import Mathlib.FieldTheory.IsSepClosed
open scoped Classical Polynomial
open FiniteDimensional Polynomial IntermediateField Field
noncomputable section
universe u v w
variable (F : Type u) (E : Type v) [Field F] [Field E] [Algebra F E]
variable (K : Type w) [Field K] [Algebra F K]
section separableClosure
def separableClosure : IntermediateField F E where
carrier := {x | (minpoly F x).Separable}
mul_mem' := separable_mul
add_mem' := separable_add
algebraMap_mem' := separable_algebraMap E
inv_mem' := separable_inv
variable {F E K}
theorem mem_separableClosure_iff {x : E} :
x ∈ separableClosure F E ↔ (minpoly F x).Separable := Iff.rfl
theorem map_mem_separableClosure_iff (i : E →ₐ[F] K) {x : E} :
i x ∈ separableClosure F K ↔ x ∈ separableClosure F E := by
simp_rw [mem_separableClosure_iff, minpoly.algHom_eq i i.injective]
| Mathlib/FieldTheory/SeparableClosure.lean | 100 | 103 | theorem separableClosure.comap_eq_of_algHom (i : E →ₐ[F] K) :
(separableClosure F K).comap i = separableClosure F E := by |
ext x
exact map_mem_separableClosure_iff i
| 2,042 |
import Mathlib.FieldTheory.SeparableDegree
import Mathlib.FieldTheory.IsSepClosed
open scoped Classical Polynomial
open FiniteDimensional Polynomial IntermediateField Field
noncomputable section
universe u v w
variable (F : Type u) (E : Type v) [Field F] [Field E] [Algebra F E]
variable (K : Type w) [Field K] [Algebra F K]
section separableClosure
def separableClosure : IntermediateField F E where
carrier := {x | (minpoly F x).Separable}
mul_mem' := separable_mul
add_mem' := separable_add
algebraMap_mem' := separable_algebraMap E
inv_mem' := separable_inv
variable {F E K}
theorem mem_separableClosure_iff {x : E} :
x ∈ separableClosure F E ↔ (minpoly F x).Separable := Iff.rfl
theorem map_mem_separableClosure_iff (i : E →ₐ[F] K) {x : E} :
i x ∈ separableClosure F K ↔ x ∈ separableClosure F E := by
simp_rw [mem_separableClosure_iff, minpoly.algHom_eq i i.injective]
theorem separableClosure.comap_eq_of_algHom (i : E →ₐ[F] K) :
(separableClosure F K).comap i = separableClosure F E := by
ext x
exact map_mem_separableClosure_iff i
theorem separableClosure.map_le_of_algHom (i : E →ₐ[F] K) :
(separableClosure F E).map i ≤ separableClosure F K :=
map_le_iff_le_comap.2 (comap_eq_of_algHom i).ge
variable (F) in
| Mathlib/FieldTheory/SeparableClosure.lean | 115 | 121 | theorem separableClosure.map_eq_of_separableClosure_eq_bot [Algebra E K] [IsScalarTower F E K]
(h : separableClosure E K = ⊥) :
(separableClosure F E).map (IsScalarTower.toAlgHom F E K) = separableClosure F K := by |
refine le_antisymm (map_le_of_algHom _) (fun x hx ↦ ?_)
obtain ⟨y, rfl⟩ := mem_bot.1 <| h ▸ mem_separableClosure_iff.2
(mem_separableClosure_iff.1 hx |>.map_minpoly E)
exact ⟨y, (map_mem_separableClosure_iff <| IsScalarTower.toAlgHom F E K).mp hx, rfl⟩
| 2,042 |
import Mathlib.FieldTheory.SeparableDegree
import Mathlib.FieldTheory.IsSepClosed
open scoped Classical Polynomial
open FiniteDimensional Polynomial IntermediateField Field
noncomputable section
universe u v w
variable (F : Type u) (E : Type v) [Field F] [Field E] [Algebra F E]
variable (K : Type w) [Field K] [Algebra F K]
section separableClosure
def separableClosure : IntermediateField F E where
carrier := {x | (minpoly F x).Separable}
mul_mem' := separable_mul
add_mem' := separable_add
algebraMap_mem' := separable_algebraMap E
inv_mem' := separable_inv
variable {F E K}
theorem mem_separableClosure_iff {x : E} :
x ∈ separableClosure F E ↔ (minpoly F x).Separable := Iff.rfl
theorem map_mem_separableClosure_iff (i : E →ₐ[F] K) {x : E} :
i x ∈ separableClosure F K ↔ x ∈ separableClosure F E := by
simp_rw [mem_separableClosure_iff, minpoly.algHom_eq i i.injective]
theorem separableClosure.comap_eq_of_algHom (i : E →ₐ[F] K) :
(separableClosure F K).comap i = separableClosure F E := by
ext x
exact map_mem_separableClosure_iff i
theorem separableClosure.map_le_of_algHom (i : E →ₐ[F] K) :
(separableClosure F E).map i ≤ separableClosure F K :=
map_le_iff_le_comap.2 (comap_eq_of_algHom i).ge
variable (F) in
theorem separableClosure.map_eq_of_separableClosure_eq_bot [Algebra E K] [IsScalarTower F E K]
(h : separableClosure E K = ⊥) :
(separableClosure F E).map (IsScalarTower.toAlgHom F E K) = separableClosure F K := by
refine le_antisymm (map_le_of_algHom _) (fun x hx ↦ ?_)
obtain ⟨y, rfl⟩ := mem_bot.1 <| h ▸ mem_separableClosure_iff.2
(mem_separableClosure_iff.1 hx |>.map_minpoly E)
exact ⟨y, (map_mem_separableClosure_iff <| IsScalarTower.toAlgHom F E K).mp hx, rfl⟩
theorem separableClosure.map_eq_of_algEquiv (i : E ≃ₐ[F] K) :
(separableClosure F E).map i = separableClosure F K :=
(map_le_of_algHom i.toAlgHom).antisymm
(fun x h ↦ ⟨_, (map_mem_separableClosure_iff i.symm).2 h, by simp⟩)
def separableClosure.algEquivOfAlgEquiv (i : E ≃ₐ[F] K) :
separableClosure F E ≃ₐ[F] separableClosure F K :=
(intermediateFieldMap i _).trans (equivOfEq (map_eq_of_algEquiv i))
alias AlgEquiv.separableClosure := separableClosure.algEquivOfAlgEquiv
variable (F E K)
instance separableClosure.isAlgebraic : Algebra.IsAlgebraic F (separableClosure F E) :=
⟨fun x ↦ isAlgebraic_iff.2 x.2.isIntegral.isAlgebraic⟩
instance separableClosure.isSeparable : IsSeparable F (separableClosure F E) :=
⟨fun x ↦ by simpa only [minpoly_eq] using x.2⟩
theorem le_separableClosure' {L : IntermediateField F E} (hs : ∀ x : L, (minpoly F x).Separable) :
L ≤ separableClosure F E := fun x h ↦ by simpa only [minpoly_eq] using hs ⟨x, h⟩
theorem le_separableClosure (L : IntermediateField F E) [IsSeparable F L] :
L ≤ separableClosure F E := le_separableClosure' F E (IsSeparable.separable F)
theorem le_separableClosure_iff (L : IntermediateField F E) :
L ≤ separableClosure F E ↔ IsSeparable F L :=
⟨fun h ↦ ⟨fun x ↦ by simpa only [minpoly_eq] using h x.2⟩, fun _ ↦ le_separableClosure _ _ _⟩
theorem separableClosure.separableClosure_eq_bot :
separableClosure (separableClosure F E) E = ⊥ := bot_unique fun x hx ↦
mem_bot.2 ⟨⟨x, mem_separableClosure_iff.1 hx |>.comap_minpoly_of_isSeparable F⟩, rfl⟩
theorem separableClosure.normalClosure_eq_self :
normalClosure F (separableClosure F E) E = separableClosure F E :=
le_antisymm (normalClosure_le_iff.2 fun i ↦
haveI : IsSeparable F i.fieldRange := (AlgEquiv.ofInjectiveField i).isSeparable
le_separableClosure F E _) (le_normalClosure _)
instance separableClosure.isGalois [Normal F E] : IsGalois F (separableClosure F E) where
to_isSeparable := separableClosure.isSeparable F E
to_normal := by
rw [← separableClosure.normalClosure_eq_self]
exact normalClosure.normal F _ E
| Mathlib/FieldTheory/SeparableClosure.lean | 186 | 192 | theorem IsSepClosed.separableClosure_eq_bot_iff [IsSepClosed E] :
separableClosure F E = ⊥ ↔ IsSepClosed F := by |
refine ⟨fun h ↦ IsSepClosed.of_exists_root _ fun p _ hirr hsep ↦ ?_,
fun _ ↦ IntermediateField.eq_bot_of_isSepClosed_of_isSeparable _⟩
obtain ⟨x, hx⟩ := IsSepClosed.exists_aeval_eq_zero E p (degree_pos_of_irreducible hirr).ne' hsep
obtain ⟨x, rfl⟩ := h ▸ mem_separableClosure_iff.2 (hsep.of_dvd <| minpoly.dvd _ x hx)
exact ⟨x, by simpa [Algebra.ofId_apply] using hx⟩
| 2,042 |
import Mathlib.FieldTheory.SeparableClosure
import Mathlib.Algebra.CharP.IntermediateField
open FiniteDimensional Polynomial IntermediateField Field
noncomputable section
universe u v w
variable (F : Type u) (E : Type v) [Field F] [Field E] [Algebra F E]
variable (K : Type w) [Field K] [Algebra F K]
section IsPurelyInseparable
class IsPurelyInseparable : Prop where
isIntegral : Algebra.IsIntegral F E
inseparable' (x : E) : (minpoly F x).Separable → x ∈ (algebraMap F E).range
attribute [instance] IsPurelyInseparable.isIntegral
variable {E} in
theorem IsPurelyInseparable.isIntegral' [IsPurelyInseparable F E] (x : E) : IsIntegral F x :=
Algebra.IsIntegral.isIntegral _
theorem IsPurelyInseparable.isAlgebraic [IsPurelyInseparable F E] :
Algebra.IsAlgebraic F E := inferInstance
variable {E}
theorem IsPurelyInseparable.inseparable [IsPurelyInseparable F E] :
∀ x : E, (minpoly F x).Separable → x ∈ (algebraMap F E).range :=
IsPurelyInseparable.inseparable'
variable {F K}
theorem isPurelyInseparable_iff : IsPurelyInseparable F E ↔ ∀ x : E,
IsIntegral F x ∧ ((minpoly F x).Separable → x ∈ (algebraMap F E).range) :=
⟨fun h x ↦ ⟨h.isIntegral' x, h.inseparable' x⟩, fun h ↦ ⟨⟨fun x ↦ (h x).1⟩, fun x ↦ (h x).2⟩⟩
| Mathlib/FieldTheory/PurelyInseparable.lean | 169 | 174 | theorem AlgEquiv.isPurelyInseparable (e : K ≃ₐ[F] E) [IsPurelyInseparable F K] :
IsPurelyInseparable F E := by |
refine ⟨⟨fun _ ↦ by rw [← isIntegral_algEquiv e.symm]; exact IsPurelyInseparable.isIntegral' F _⟩,
fun x h ↦ ?_⟩
rw [← minpoly.algEquiv_eq e.symm] at h
simpa only [RingHom.mem_range, algebraMap_eq_apply] using IsPurelyInseparable.inseparable F _ h
| 2,043 |
import Mathlib.FieldTheory.SeparableClosure
import Mathlib.Algebra.CharP.IntermediateField
open FiniteDimensional Polynomial IntermediateField Field
noncomputable section
universe u v w
variable (F : Type u) (E : Type v) [Field F] [Field E] [Algebra F E]
variable (K : Type w) [Field K] [Algebra F K]
section IsPurelyInseparable
class IsPurelyInseparable : Prop where
isIntegral : Algebra.IsIntegral F E
inseparable' (x : E) : (minpoly F x).Separable → x ∈ (algebraMap F E).range
attribute [instance] IsPurelyInseparable.isIntegral
variable {E} in
theorem IsPurelyInseparable.isIntegral' [IsPurelyInseparable F E] (x : E) : IsIntegral F x :=
Algebra.IsIntegral.isIntegral _
theorem IsPurelyInseparable.isAlgebraic [IsPurelyInseparable F E] :
Algebra.IsAlgebraic F E := inferInstance
variable {E}
theorem IsPurelyInseparable.inseparable [IsPurelyInseparable F E] :
∀ x : E, (minpoly F x).Separable → x ∈ (algebraMap F E).range :=
IsPurelyInseparable.inseparable'
variable {F K}
theorem isPurelyInseparable_iff : IsPurelyInseparable F E ↔ ∀ x : E,
IsIntegral F x ∧ ((minpoly F x).Separable → x ∈ (algebraMap F E).range) :=
⟨fun h x ↦ ⟨h.isIntegral' x, h.inseparable' x⟩, fun h ↦ ⟨⟨fun x ↦ (h x).1⟩, fun x ↦ (h x).2⟩⟩
theorem AlgEquiv.isPurelyInseparable (e : K ≃ₐ[F] E) [IsPurelyInseparable F K] :
IsPurelyInseparable F E := by
refine ⟨⟨fun _ ↦ by rw [← isIntegral_algEquiv e.symm]; exact IsPurelyInseparable.isIntegral' F _⟩,
fun x h ↦ ?_⟩
rw [← minpoly.algEquiv_eq e.symm] at h
simpa only [RingHom.mem_range, algebraMap_eq_apply] using IsPurelyInseparable.inseparable F _ h
theorem AlgEquiv.isPurelyInseparable_iff (e : K ≃ₐ[F] E) :
IsPurelyInseparable F K ↔ IsPurelyInseparable F E :=
⟨fun _ ↦ e.isPurelyInseparable, fun _ ↦ e.symm.isPurelyInseparable⟩
theorem Algebra.IsAlgebraic.isPurelyInseparable_of_isSepClosed [Algebra.IsAlgebraic F E]
[IsSepClosed F] : IsPurelyInseparable F E :=
⟨inferInstance, fun x h ↦ minpoly.mem_range_of_degree_eq_one F x <|
IsSepClosed.degree_eq_one_of_irreducible F (minpoly.irreducible
(Algebra.IsIntegral.isIntegral _)) h⟩
variable (F E K)
theorem IsPurelyInseparable.surjective_algebraMap_of_isSeparable
[IsPurelyInseparable F E] [IsSeparable F E] : Function.Surjective (algebraMap F E) :=
fun x ↦ IsPurelyInseparable.inseparable F x (IsSeparable.separable F x)
theorem IsPurelyInseparable.bijective_algebraMap_of_isSeparable
[IsPurelyInseparable F E] [IsSeparable F E] : Function.Bijective (algebraMap F E) :=
⟨(algebraMap F E).injective, surjective_algebraMap_of_isSeparable F E⟩
variable {F E} in
theorem IntermediateField.eq_bot_of_isPurelyInseparable_of_isSeparable (L : IntermediateField F E)
[IsPurelyInseparable F L] [IsSeparable F L] : L = ⊥ := bot_unique fun x hx ↦ by
obtain ⟨y, hy⟩ := IsPurelyInseparable.surjective_algebraMap_of_isSeparable F L ⟨x, hx⟩
exact ⟨y, congr_arg (algebraMap L E) hy⟩
theorem separableClosure.eq_bot_of_isPurelyInseparable [IsPurelyInseparable F E] :
separableClosure F E = ⊥ :=
bot_unique fun x h ↦ IsPurelyInseparable.inseparable F x (mem_separableClosure_iff.1 h)
variable {F E} in
theorem separableClosure.eq_bot_iff [Algebra.IsAlgebraic F E] :
separableClosure F E = ⊥ ↔ IsPurelyInseparable F E :=
⟨fun h ↦ isPurelyInseparable_iff.2 fun x ↦ ⟨Algebra.IsIntegral.isIntegral x, fun hs ↦ by
simpa only [h] using mem_separableClosure_iff.2 hs⟩, fun _ ↦ eq_bot_of_isPurelyInseparable F E⟩
instance isPurelyInseparable_self : IsPurelyInseparable F F :=
⟨inferInstance, fun x _ ↦ ⟨x, rfl⟩⟩
variable {E}
| Mathlib/FieldTheory/PurelyInseparable.lean | 230 | 243 | theorem isPurelyInseparable_iff_pow_mem (q : ℕ) [ExpChar F q] :
IsPurelyInseparable F E ↔ ∀ x : E, ∃ n : ℕ, x ^ q ^ n ∈ (algebraMap F E).range := by |
rw [isPurelyInseparable_iff]
refine ⟨fun h x ↦ ?_, fun h x ↦ ?_⟩
· obtain ⟨g, h1, n, h2⟩ := (minpoly.irreducible (h x).1).hasSeparableContraction q
exact ⟨n, (h _).2 <| h1.of_dvd <| minpoly.dvd F _ <| by
simpa only [expand_aeval, minpoly.aeval] using congr_arg (aeval x) h2⟩
have hdeg := (minpoly.natSepDegree_eq_one_iff_pow_mem q).2 (h x)
have halg : IsIntegral F x := by_contra fun h' ↦ by
simp only [minpoly.eq_zero h', natSepDegree_zero, zero_ne_one] at hdeg
refine ⟨halg, fun hsep ↦ ?_⟩
rw [hsep.natSepDegree_eq_natDegree, ← adjoin.finrank halg,
IntermediateField.finrank_eq_one_iff] at hdeg
simpa only [hdeg] using mem_adjoin_simple_self F x
| 2,043 |
import Mathlib.FieldTheory.SeparableClosure
import Mathlib.Algebra.CharP.IntermediateField
open FiniteDimensional Polynomial IntermediateField Field
noncomputable section
universe u v w
variable (F : Type u) (E : Type v) [Field F] [Field E] [Algebra F E]
variable (K : Type w) [Field K] [Algebra F K]
section perfectClosure
def perfectClosure : IntermediateField F E where
carrier := {x : E | ∃ n : ℕ, x ^ (ringExpChar F) ^ n ∈ (algebraMap F E).range}
add_mem' := by
rintro x y ⟨n, hx⟩ ⟨m, hy⟩
use n + m
have := expChar_of_injective_algebraMap (algebraMap F E).injective (ringExpChar F)
rw [add_pow_expChar_pow, pow_add, pow_mul, mul_comm (_ ^ n), pow_mul]
exact add_mem (pow_mem hx _) (pow_mem hy _)
mul_mem' := by
rintro x y ⟨n, hx⟩ ⟨m, hy⟩
use n + m
rw [mul_pow, pow_add, pow_mul, mul_comm (_ ^ n), pow_mul]
exact mul_mem (pow_mem hx _) (pow_mem hy _)
inv_mem' := by
rintro x ⟨n, hx⟩
use n; rw [inv_pow]
apply inv_mem (id hx : _ ∈ (⊥ : IntermediateField F E))
algebraMap_mem' := fun x ↦ ⟨0, by rw [pow_zero, pow_one]; exact ⟨x, rfl⟩⟩
variable {F E}
theorem mem_perfectClosure_iff {x : E} :
x ∈ perfectClosure F E ↔ ∃ n : ℕ, x ^ (ringExpChar F) ^ n ∈ (algebraMap F E).range := Iff.rfl
| Mathlib/FieldTheory/PurelyInseparable.lean | 281 | 283 | theorem mem_perfectClosure_iff_pow_mem (q : ℕ) [ExpChar F q] {x : E} :
x ∈ perfectClosure F E ↔ ∃ n : ℕ, x ^ q ^ n ∈ (algebraMap F E).range := by |
rw [mem_perfectClosure_iff, ringExpChar.eq F q]
| 2,043 |
import Mathlib.FieldTheory.SeparableClosure
import Mathlib.Algebra.CharP.IntermediateField
open FiniteDimensional Polynomial IntermediateField Field
noncomputable section
universe u v w
variable (F : Type u) (E : Type v) [Field F] [Field E] [Algebra F E]
variable (K : Type w) [Field K] [Algebra F K]
section perfectClosure
def perfectClosure : IntermediateField F E where
carrier := {x : E | ∃ n : ℕ, x ^ (ringExpChar F) ^ n ∈ (algebraMap F E).range}
add_mem' := by
rintro x y ⟨n, hx⟩ ⟨m, hy⟩
use n + m
have := expChar_of_injective_algebraMap (algebraMap F E).injective (ringExpChar F)
rw [add_pow_expChar_pow, pow_add, pow_mul, mul_comm (_ ^ n), pow_mul]
exact add_mem (pow_mem hx _) (pow_mem hy _)
mul_mem' := by
rintro x y ⟨n, hx⟩ ⟨m, hy⟩
use n + m
rw [mul_pow, pow_add, pow_mul, mul_comm (_ ^ n), pow_mul]
exact mul_mem (pow_mem hx _) (pow_mem hy _)
inv_mem' := by
rintro x ⟨n, hx⟩
use n; rw [inv_pow]
apply inv_mem (id hx : _ ∈ (⊥ : IntermediateField F E))
algebraMap_mem' := fun x ↦ ⟨0, by rw [pow_zero, pow_one]; exact ⟨x, rfl⟩⟩
variable {F E}
theorem mem_perfectClosure_iff {x : E} :
x ∈ perfectClosure F E ↔ ∃ n : ℕ, x ^ (ringExpChar F) ^ n ∈ (algebraMap F E).range := Iff.rfl
theorem mem_perfectClosure_iff_pow_mem (q : ℕ) [ExpChar F q] {x : E} :
x ∈ perfectClosure F E ↔ ∃ n : ℕ, x ^ q ^ n ∈ (algebraMap F E).range := by
rw [mem_perfectClosure_iff, ringExpChar.eq F q]
| Mathlib/FieldTheory/PurelyInseparable.lean | 287 | 289 | theorem mem_perfectClosure_iff_natSepDegree_eq_one {x : E} :
x ∈ perfectClosure F E ↔ (minpoly F x).natSepDegree = 1 := by |
rw [mem_perfectClosure_iff, minpoly.natSepDegree_eq_one_iff_pow_mem (ringExpChar F)]
| 2,043 |
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Matrix.ToLinearEquiv
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
#align_import ring_theory.norm from "leanprover-community/mathlib"@"fecd3520d2a236856f254f27714b80dcfe28ea57"
universe u v w
variable {R S T : Type*} [CommRing R] [Ring S]
variable [Algebra R S]
variable {K L F : Type*} [Field K] [Field L] [Field F]
variable [Algebra K L] [Algebra K F]
variable {ι : Type w}
open FiniteDimensional
open LinearMap
open Matrix Polynomial
open scoped Matrix
namespace Algebra
variable (R)
noncomputable def norm : S →* R :=
LinearMap.det.comp (lmul R S).toRingHom.toMonoidHom
#align algebra.norm Algebra.norm
theorem norm_apply (x : S) : norm R x = LinearMap.det (lmul R S x) := rfl
#align algebra.norm_apply Algebra.norm_apply
| Mathlib/RingTheory/Norm.lean | 72 | 73 | theorem norm_eq_one_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) (x : S) :
norm R x = 1 := by | rw [norm_apply, LinearMap.det]; split_ifs <;> trivial
| 2,044 |
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Matrix.ToLinearEquiv
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
#align_import ring_theory.norm from "leanprover-community/mathlib"@"fecd3520d2a236856f254f27714b80dcfe28ea57"
universe u v w
variable {R S T : Type*} [CommRing R] [Ring S]
variable [Algebra R S]
variable {K L F : Type*} [Field K] [Field L] [Field F]
variable [Algebra K L] [Algebra K F]
variable {ι : Type w}
open FiniteDimensional
open LinearMap
open Matrix Polynomial
open scoped Matrix
namespace Algebra
variable (R)
noncomputable def norm : S →* R :=
LinearMap.det.comp (lmul R S).toRingHom.toMonoidHom
#align algebra.norm Algebra.norm
theorem norm_apply (x : S) : norm R x = LinearMap.det (lmul R S x) := rfl
#align algebra.norm_apply Algebra.norm_apply
theorem norm_eq_one_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) (x : S) :
norm R x = 1 := by rw [norm_apply, LinearMap.det]; split_ifs <;> trivial
#align algebra.norm_eq_one_of_not_exists_basis Algebra.norm_eq_one_of_not_exists_basis
variable {R}
| Mathlib/RingTheory/Norm.lean | 78 | 81 | theorem norm_eq_one_of_not_module_finite (h : ¬Module.Finite R S) (x : S) : norm R x = 1 := by |
refine norm_eq_one_of_not_exists_basis _ (mt ?_ h) _
rintro ⟨s, ⟨b⟩⟩
exact Module.Finite.of_basis b
| 2,044 |
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Matrix.ToLinearEquiv
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
#align_import ring_theory.norm from "leanprover-community/mathlib"@"fecd3520d2a236856f254f27714b80dcfe28ea57"
universe u v w
variable {R S T : Type*} [CommRing R] [Ring S]
variable [Algebra R S]
variable {K L F : Type*} [Field K] [Field L] [Field F]
variable [Algebra K L] [Algebra K F]
variable {ι : Type w}
open FiniteDimensional
open LinearMap
open Matrix Polynomial
open scoped Matrix
namespace Algebra
variable (R)
noncomputable def norm : S →* R :=
LinearMap.det.comp (lmul R S).toRingHom.toMonoidHom
#align algebra.norm Algebra.norm
theorem norm_apply (x : S) : norm R x = LinearMap.det (lmul R S x) := rfl
#align algebra.norm_apply Algebra.norm_apply
theorem norm_eq_one_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) (x : S) :
norm R x = 1 := by rw [norm_apply, LinearMap.det]; split_ifs <;> trivial
#align algebra.norm_eq_one_of_not_exists_basis Algebra.norm_eq_one_of_not_exists_basis
variable {R}
theorem norm_eq_one_of_not_module_finite (h : ¬Module.Finite R S) (x : S) : norm R x = 1 := by
refine norm_eq_one_of_not_exists_basis _ (mt ?_ h) _
rintro ⟨s, ⟨b⟩⟩
exact Module.Finite.of_basis b
#align algebra.norm_eq_one_of_not_module_finite Algebra.norm_eq_one_of_not_module_finite
-- Can't be a `simp` lemma because it depends on a choice of basis
| Mathlib/RingTheory/Norm.lean | 85 | 87 | theorem norm_eq_matrix_det [Fintype ι] [DecidableEq ι] (b : Basis ι R S) (s : S) :
norm R s = Matrix.det (Algebra.leftMulMatrix b s) := by |
rw [norm_apply, ← LinearMap.det_toMatrix b, ← toMatrix_lmul_eq]; rfl
| 2,044 |
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Matrix.ToLinearEquiv
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
#align_import ring_theory.norm from "leanprover-community/mathlib"@"fecd3520d2a236856f254f27714b80dcfe28ea57"
universe u v w
variable {R S T : Type*} [CommRing R] [Ring S]
variable [Algebra R S]
variable {K L F : Type*} [Field K] [Field L] [Field F]
variable [Algebra K L] [Algebra K F]
variable {ι : Type w}
open FiniteDimensional
open LinearMap
open Matrix Polynomial
open scoped Matrix
namespace Algebra
variable (R)
noncomputable def norm : S →* R :=
LinearMap.det.comp (lmul R S).toRingHom.toMonoidHom
#align algebra.norm Algebra.norm
theorem norm_apply (x : S) : norm R x = LinearMap.det (lmul R S x) := rfl
#align algebra.norm_apply Algebra.norm_apply
theorem norm_eq_one_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) (x : S) :
norm R x = 1 := by rw [norm_apply, LinearMap.det]; split_ifs <;> trivial
#align algebra.norm_eq_one_of_not_exists_basis Algebra.norm_eq_one_of_not_exists_basis
variable {R}
theorem norm_eq_one_of_not_module_finite (h : ¬Module.Finite R S) (x : S) : norm R x = 1 := by
refine norm_eq_one_of_not_exists_basis _ (mt ?_ h) _
rintro ⟨s, ⟨b⟩⟩
exact Module.Finite.of_basis b
#align algebra.norm_eq_one_of_not_module_finite Algebra.norm_eq_one_of_not_module_finite
-- Can't be a `simp` lemma because it depends on a choice of basis
theorem norm_eq_matrix_det [Fintype ι] [DecidableEq ι] (b : Basis ι R S) (s : S) :
norm R s = Matrix.det (Algebra.leftMulMatrix b s) := by
rw [norm_apply, ← LinearMap.det_toMatrix b, ← toMatrix_lmul_eq]; rfl
#align algebra.norm_eq_matrix_det Algebra.norm_eq_matrix_det
| Mathlib/RingTheory/Norm.lean | 91 | 97 | theorem norm_algebraMap_of_basis [Fintype ι] (b : Basis ι R S) (x : R) :
norm R (algebraMap R S x) = x ^ Fintype.card ι := by |
haveI := Classical.decEq ι
rw [norm_apply, ← det_toMatrix b, lmul_algebraMap]
convert @det_diagonal _ _ _ _ _ fun _ : ι => x
· ext (i j); rw [toMatrix_lsmul]
· rw [Finset.prod_const, Finset.card_univ]
| 2,044 |
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Matrix.ToLinearEquiv
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
#align_import ring_theory.norm from "leanprover-community/mathlib"@"fecd3520d2a236856f254f27714b80dcfe28ea57"
universe u v w
variable {R S T : Type*} [CommRing R] [Ring S]
variable [Algebra R S]
variable {K L F : Type*} [Field K] [Field L] [Field F]
variable [Algebra K L] [Algebra K F]
variable {ι : Type w}
open FiniteDimensional
open LinearMap
open Matrix Polynomial
open scoped Matrix
namespace Algebra
variable (R)
noncomputable def norm : S →* R :=
LinearMap.det.comp (lmul R S).toRingHom.toMonoidHom
#align algebra.norm Algebra.norm
theorem norm_apply (x : S) : norm R x = LinearMap.det (lmul R S x) := rfl
#align algebra.norm_apply Algebra.norm_apply
theorem norm_eq_one_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) (x : S) :
norm R x = 1 := by rw [norm_apply, LinearMap.det]; split_ifs <;> trivial
#align algebra.norm_eq_one_of_not_exists_basis Algebra.norm_eq_one_of_not_exists_basis
variable {R}
theorem norm_eq_one_of_not_module_finite (h : ¬Module.Finite R S) (x : S) : norm R x = 1 := by
refine norm_eq_one_of_not_exists_basis _ (mt ?_ h) _
rintro ⟨s, ⟨b⟩⟩
exact Module.Finite.of_basis b
#align algebra.norm_eq_one_of_not_module_finite Algebra.norm_eq_one_of_not_module_finite
-- Can't be a `simp` lemma because it depends on a choice of basis
theorem norm_eq_matrix_det [Fintype ι] [DecidableEq ι] (b : Basis ι R S) (s : S) :
norm R s = Matrix.det (Algebra.leftMulMatrix b s) := by
rw [norm_apply, ← LinearMap.det_toMatrix b, ← toMatrix_lmul_eq]; rfl
#align algebra.norm_eq_matrix_det Algebra.norm_eq_matrix_det
theorem norm_algebraMap_of_basis [Fintype ι] (b : Basis ι R S) (x : R) :
norm R (algebraMap R S x) = x ^ Fintype.card ι := by
haveI := Classical.decEq ι
rw [norm_apply, ← det_toMatrix b, lmul_algebraMap]
convert @det_diagonal _ _ _ _ _ fun _ : ι => x
· ext (i j); rw [toMatrix_lsmul]
· rw [Finset.prod_const, Finset.card_univ]
#align algebra.norm_algebra_map_of_basis Algebra.norm_algebraMap_of_basis
@[simp]
protected theorem norm_algebraMap {L : Type*} [Ring L] [Algebra K L] (x : K) :
norm K (algebraMap K L x) = x ^ finrank K L := by
by_cases H : ∃ s : Finset L, Nonempty (Basis s K L)
· rw [norm_algebraMap_of_basis H.choose_spec.some, finrank_eq_card_basis H.choose_spec.some]
· rw [norm_eq_one_of_not_exists_basis K H, finrank_eq_zero_of_not_exists_basis, pow_zero]
rintro ⟨s, ⟨b⟩⟩
exact H ⟨s, ⟨b⟩⟩
#align algebra.norm_algebra_map Algebra.norm_algebraMap
section EqProdRoots
| Mathlib/RingTheory/Norm.lean | 118 | 121 | theorem PowerBasis.norm_gen_eq_coeff_zero_minpoly (pb : PowerBasis R S) :
norm R pb.gen = (-1) ^ pb.dim * coeff (minpoly R pb.gen) 0 := by |
rw [norm_eq_matrix_det pb.basis, det_eq_sign_charpoly_coeff, charpoly_leftMulMatrix,
Fintype.card_fin]
| 2,044 |
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Matrix.ToLinearEquiv
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
#align_import ring_theory.norm from "leanprover-community/mathlib"@"fecd3520d2a236856f254f27714b80dcfe28ea57"
universe u v w
variable {R S T : Type*} [CommRing R] [Ring S]
variable [Algebra R S]
variable {K L F : Type*} [Field K] [Field L] [Field F]
variable [Algebra K L] [Algebra K F]
variable {ι : Type w}
open FiniteDimensional
open LinearMap
open Matrix Polynomial
open scoped Matrix
namespace Algebra
variable (R)
noncomputable def norm : S →* R :=
LinearMap.det.comp (lmul R S).toRingHom.toMonoidHom
#align algebra.norm Algebra.norm
theorem norm_apply (x : S) : norm R x = LinearMap.det (lmul R S x) := rfl
#align algebra.norm_apply Algebra.norm_apply
theorem norm_eq_one_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) (x : S) :
norm R x = 1 := by rw [norm_apply, LinearMap.det]; split_ifs <;> trivial
#align algebra.norm_eq_one_of_not_exists_basis Algebra.norm_eq_one_of_not_exists_basis
variable {R}
theorem norm_eq_one_of_not_module_finite (h : ¬Module.Finite R S) (x : S) : norm R x = 1 := by
refine norm_eq_one_of_not_exists_basis _ (mt ?_ h) _
rintro ⟨s, ⟨b⟩⟩
exact Module.Finite.of_basis b
#align algebra.norm_eq_one_of_not_module_finite Algebra.norm_eq_one_of_not_module_finite
-- Can't be a `simp` lemma because it depends on a choice of basis
theorem norm_eq_matrix_det [Fintype ι] [DecidableEq ι] (b : Basis ι R S) (s : S) :
norm R s = Matrix.det (Algebra.leftMulMatrix b s) := by
rw [norm_apply, ← LinearMap.det_toMatrix b, ← toMatrix_lmul_eq]; rfl
#align algebra.norm_eq_matrix_det Algebra.norm_eq_matrix_det
theorem norm_algebraMap_of_basis [Fintype ι] (b : Basis ι R S) (x : R) :
norm R (algebraMap R S x) = x ^ Fintype.card ι := by
haveI := Classical.decEq ι
rw [norm_apply, ← det_toMatrix b, lmul_algebraMap]
convert @det_diagonal _ _ _ _ _ fun _ : ι => x
· ext (i j); rw [toMatrix_lsmul]
· rw [Finset.prod_const, Finset.card_univ]
#align algebra.norm_algebra_map_of_basis Algebra.norm_algebraMap_of_basis
@[simp]
protected theorem norm_algebraMap {L : Type*} [Ring L] [Algebra K L] (x : K) :
norm K (algebraMap K L x) = x ^ finrank K L := by
by_cases H : ∃ s : Finset L, Nonempty (Basis s K L)
· rw [norm_algebraMap_of_basis H.choose_spec.some, finrank_eq_card_basis H.choose_spec.some]
· rw [norm_eq_one_of_not_exists_basis K H, finrank_eq_zero_of_not_exists_basis, pow_zero]
rintro ⟨s, ⟨b⟩⟩
exact H ⟨s, ⟨b⟩⟩
#align algebra.norm_algebra_map Algebra.norm_algebraMap
section EqProdRoots
theorem PowerBasis.norm_gen_eq_coeff_zero_minpoly (pb : PowerBasis R S) :
norm R pb.gen = (-1) ^ pb.dim * coeff (minpoly R pb.gen) 0 := by
rw [norm_eq_matrix_det pb.basis, det_eq_sign_charpoly_coeff, charpoly_leftMulMatrix,
Fintype.card_fin]
#align algebra.power_basis.norm_gen_eq_coeff_zero_minpoly Algebra.PowerBasis.norm_gen_eq_coeff_zero_minpoly
| Mathlib/RingTheory/Norm.lean | 126 | 135 | theorem PowerBasis.norm_gen_eq_prod_roots [Algebra R F] (pb : PowerBasis R S)
(hf : (minpoly R pb.gen).Splits (algebraMap R F)) :
algebraMap R F (norm R pb.gen) = ((minpoly R pb.gen).aroots F).prod := by |
haveI := Module.nontrivial R F
have := minpoly.monic pb.isIntegral_gen
rw [PowerBasis.norm_gen_eq_coeff_zero_minpoly, ← pb.natDegree_minpoly, RingHom.map_mul,
← coeff_map,
prod_roots_eq_coeff_zero_of_monic_of_split (this.map _) ((splits_id_iff_splits _).2 hf),
this.natDegree_map, map_pow, ← mul_assoc, ← mul_pow]
simp only [map_neg, _root_.map_one, neg_mul, neg_neg, one_pow, one_mul]
| 2,044 |
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Matrix.ToLinearEquiv
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
#align_import ring_theory.norm from "leanprover-community/mathlib"@"fecd3520d2a236856f254f27714b80dcfe28ea57"
universe u v w
variable {R S T : Type*} [CommRing R] [Ring S]
variable [Algebra R S]
variable {K L F : Type*} [Field K] [Field L] [Field F]
variable [Algebra K L] [Algebra K F]
variable {ι : Type w}
open FiniteDimensional
open LinearMap
open Matrix Polynomial
open scoped Matrix
namespace Algebra
variable (R)
noncomputable def norm : S →* R :=
LinearMap.det.comp (lmul R S).toRingHom.toMonoidHom
#align algebra.norm Algebra.norm
theorem norm_apply (x : S) : norm R x = LinearMap.det (lmul R S x) := rfl
#align algebra.norm_apply Algebra.norm_apply
theorem norm_eq_one_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) (x : S) :
norm R x = 1 := by rw [norm_apply, LinearMap.det]; split_ifs <;> trivial
#align algebra.norm_eq_one_of_not_exists_basis Algebra.norm_eq_one_of_not_exists_basis
variable {R}
theorem norm_eq_one_of_not_module_finite (h : ¬Module.Finite R S) (x : S) : norm R x = 1 := by
refine norm_eq_one_of_not_exists_basis _ (mt ?_ h) _
rintro ⟨s, ⟨b⟩⟩
exact Module.Finite.of_basis b
#align algebra.norm_eq_one_of_not_module_finite Algebra.norm_eq_one_of_not_module_finite
-- Can't be a `simp` lemma because it depends on a choice of basis
theorem norm_eq_matrix_det [Fintype ι] [DecidableEq ι] (b : Basis ι R S) (s : S) :
norm R s = Matrix.det (Algebra.leftMulMatrix b s) := by
rw [norm_apply, ← LinearMap.det_toMatrix b, ← toMatrix_lmul_eq]; rfl
#align algebra.norm_eq_matrix_det Algebra.norm_eq_matrix_det
theorem norm_algebraMap_of_basis [Fintype ι] (b : Basis ι R S) (x : R) :
norm R (algebraMap R S x) = x ^ Fintype.card ι := by
haveI := Classical.decEq ι
rw [norm_apply, ← det_toMatrix b, lmul_algebraMap]
convert @det_diagonal _ _ _ _ _ fun _ : ι => x
· ext (i j); rw [toMatrix_lsmul]
· rw [Finset.prod_const, Finset.card_univ]
#align algebra.norm_algebra_map_of_basis Algebra.norm_algebraMap_of_basis
@[simp]
protected theorem norm_algebraMap {L : Type*} [Ring L] [Algebra K L] (x : K) :
norm K (algebraMap K L x) = x ^ finrank K L := by
by_cases H : ∃ s : Finset L, Nonempty (Basis s K L)
· rw [norm_algebraMap_of_basis H.choose_spec.some, finrank_eq_card_basis H.choose_spec.some]
· rw [norm_eq_one_of_not_exists_basis K H, finrank_eq_zero_of_not_exists_basis, pow_zero]
rintro ⟨s, ⟨b⟩⟩
exact H ⟨s, ⟨b⟩⟩
#align algebra.norm_algebra_map Algebra.norm_algebraMap
section EqZeroIff
variable [Finite ι]
@[simp]
| Mathlib/RingTheory/Norm.lean | 145 | 147 | theorem norm_zero [Nontrivial S] [Module.Free R S] [Module.Finite R S] : norm R (0 : S) = 0 := by |
nontriviality
rw [norm_apply, coe_lmul_eq_mul, map_zero, LinearMap.det_zero' (Module.Free.chooseBasis R S)]
| 2,044 |
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Matrix.ToLinearEquiv
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
#align_import ring_theory.norm from "leanprover-community/mathlib"@"fecd3520d2a236856f254f27714b80dcfe28ea57"
universe u v w
variable {R S T : Type*} [CommRing R] [Ring S]
variable [Algebra R S]
variable {K L F : Type*} [Field K] [Field L] [Field F]
variable [Algebra K L] [Algebra K F]
variable {ι : Type w}
open FiniteDimensional
open LinearMap
open Matrix Polynomial
open scoped Matrix
namespace Algebra
variable (R)
noncomputable def norm : S →* R :=
LinearMap.det.comp (lmul R S).toRingHom.toMonoidHom
#align algebra.norm Algebra.norm
theorem norm_apply (x : S) : norm R x = LinearMap.det (lmul R S x) := rfl
#align algebra.norm_apply Algebra.norm_apply
theorem norm_eq_one_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) (x : S) :
norm R x = 1 := by rw [norm_apply, LinearMap.det]; split_ifs <;> trivial
#align algebra.norm_eq_one_of_not_exists_basis Algebra.norm_eq_one_of_not_exists_basis
variable {R}
theorem norm_eq_one_of_not_module_finite (h : ¬Module.Finite R S) (x : S) : norm R x = 1 := by
refine norm_eq_one_of_not_exists_basis _ (mt ?_ h) _
rintro ⟨s, ⟨b⟩⟩
exact Module.Finite.of_basis b
#align algebra.norm_eq_one_of_not_module_finite Algebra.norm_eq_one_of_not_module_finite
-- Can't be a `simp` lemma because it depends on a choice of basis
theorem norm_eq_matrix_det [Fintype ι] [DecidableEq ι] (b : Basis ι R S) (s : S) :
norm R s = Matrix.det (Algebra.leftMulMatrix b s) := by
rw [norm_apply, ← LinearMap.det_toMatrix b, ← toMatrix_lmul_eq]; rfl
#align algebra.norm_eq_matrix_det Algebra.norm_eq_matrix_det
theorem norm_algebraMap_of_basis [Fintype ι] (b : Basis ι R S) (x : R) :
norm R (algebraMap R S x) = x ^ Fintype.card ι := by
haveI := Classical.decEq ι
rw [norm_apply, ← det_toMatrix b, lmul_algebraMap]
convert @det_diagonal _ _ _ _ _ fun _ : ι => x
· ext (i j); rw [toMatrix_lsmul]
· rw [Finset.prod_const, Finset.card_univ]
#align algebra.norm_algebra_map_of_basis Algebra.norm_algebraMap_of_basis
@[simp]
protected theorem norm_algebraMap {L : Type*} [Ring L] [Algebra K L] (x : K) :
norm K (algebraMap K L x) = x ^ finrank K L := by
by_cases H : ∃ s : Finset L, Nonempty (Basis s K L)
· rw [norm_algebraMap_of_basis H.choose_spec.some, finrank_eq_card_basis H.choose_spec.some]
· rw [norm_eq_one_of_not_exists_basis K H, finrank_eq_zero_of_not_exists_basis, pow_zero]
rintro ⟨s, ⟨b⟩⟩
exact H ⟨s, ⟨b⟩⟩
#align algebra.norm_algebra_map Algebra.norm_algebraMap
section EqZeroIff
variable [Finite ι]
@[simp]
theorem norm_zero [Nontrivial S] [Module.Free R S] [Module.Finite R S] : norm R (0 : S) = 0 := by
nontriviality
rw [norm_apply, coe_lmul_eq_mul, map_zero, LinearMap.det_zero' (Module.Free.chooseBasis R S)]
#align algebra.norm_zero Algebra.norm_zero
@[simp]
| Mathlib/RingTheory/Norm.lean | 151 | 166 | theorem norm_eq_zero_iff [IsDomain R] [IsDomain S] [Module.Free R S] [Module.Finite R S] {x : S} :
norm R x = 0 ↔ x = 0 := by |
constructor
on_goal 1 => let b := Module.Free.chooseBasis R S
swap
· rintro rfl; exact norm_zero
· letI := Classical.decEq (Module.Free.ChooseBasisIndex R S)
rw [norm_eq_matrix_det b, ← Matrix.exists_mulVec_eq_zero_iff]
rintro ⟨v, v_ne, hv⟩
rw [← b.equivFun.apply_symm_apply v, b.equivFun_symm_apply, b.equivFun_apply,
leftMulMatrix_mulVec_repr] at hv
refine (mul_eq_zero.mp (b.ext_elem fun i => ?_)).resolve_right (show ∑ i, v i • b i ≠ 0 from ?_)
· simpa only [LinearEquiv.map_zero, Pi.zero_apply] using congr_fun hv i
· contrapose! v_ne with sum_eq
apply b.equivFun.symm.injective
rw [b.equivFun_symm_apply, sum_eq, LinearEquiv.map_zero]
| 2,044 |
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Matrix.ToLinearEquiv
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
#align_import ring_theory.norm from "leanprover-community/mathlib"@"fecd3520d2a236856f254f27714b80dcfe28ea57"
universe u v w
variable {R S T : Type*} [CommRing R] [Ring S]
variable [Algebra R S]
variable {K L F : Type*} [Field K] [Field L] [Field F]
variable [Algebra K L] [Algebra K F]
variable {ι : Type w}
open FiniteDimensional
open LinearMap
open Matrix Polynomial
open scoped Matrix
namespace Algebra
variable (R)
noncomputable def norm : S →* R :=
LinearMap.det.comp (lmul R S).toRingHom.toMonoidHom
#align algebra.norm Algebra.norm
theorem norm_apply (x : S) : norm R x = LinearMap.det (lmul R S x) := rfl
#align algebra.norm_apply Algebra.norm_apply
theorem norm_eq_one_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) (x : S) :
norm R x = 1 := by rw [norm_apply, LinearMap.det]; split_ifs <;> trivial
#align algebra.norm_eq_one_of_not_exists_basis Algebra.norm_eq_one_of_not_exists_basis
variable {R}
theorem norm_eq_one_of_not_module_finite (h : ¬Module.Finite R S) (x : S) : norm R x = 1 := by
refine norm_eq_one_of_not_exists_basis _ (mt ?_ h) _
rintro ⟨s, ⟨b⟩⟩
exact Module.Finite.of_basis b
#align algebra.norm_eq_one_of_not_module_finite Algebra.norm_eq_one_of_not_module_finite
-- Can't be a `simp` lemma because it depends on a choice of basis
theorem norm_eq_matrix_det [Fintype ι] [DecidableEq ι] (b : Basis ι R S) (s : S) :
norm R s = Matrix.det (Algebra.leftMulMatrix b s) := by
rw [norm_apply, ← LinearMap.det_toMatrix b, ← toMatrix_lmul_eq]; rfl
#align algebra.norm_eq_matrix_det Algebra.norm_eq_matrix_det
theorem norm_algebraMap_of_basis [Fintype ι] (b : Basis ι R S) (x : R) :
norm R (algebraMap R S x) = x ^ Fintype.card ι := by
haveI := Classical.decEq ι
rw [norm_apply, ← det_toMatrix b, lmul_algebraMap]
convert @det_diagonal _ _ _ _ _ fun _ : ι => x
· ext (i j); rw [toMatrix_lsmul]
· rw [Finset.prod_const, Finset.card_univ]
#align algebra.norm_algebra_map_of_basis Algebra.norm_algebraMap_of_basis
@[simp]
protected theorem norm_algebraMap {L : Type*} [Ring L] [Algebra K L] (x : K) :
norm K (algebraMap K L x) = x ^ finrank K L := by
by_cases H : ∃ s : Finset L, Nonempty (Basis s K L)
· rw [norm_algebraMap_of_basis H.choose_spec.some, finrank_eq_card_basis H.choose_spec.some]
· rw [norm_eq_one_of_not_exists_basis K H, finrank_eq_zero_of_not_exists_basis, pow_zero]
rintro ⟨s, ⟨b⟩⟩
exact H ⟨s, ⟨b⟩⟩
#align algebra.norm_algebra_map Algebra.norm_algebraMap
section EqZeroIff
variable [Finite ι]
@[simp]
theorem norm_zero [Nontrivial S] [Module.Free R S] [Module.Finite R S] : norm R (0 : S) = 0 := by
nontriviality
rw [norm_apply, coe_lmul_eq_mul, map_zero, LinearMap.det_zero' (Module.Free.chooseBasis R S)]
#align algebra.norm_zero Algebra.norm_zero
@[simp]
theorem norm_eq_zero_iff [IsDomain R] [IsDomain S] [Module.Free R S] [Module.Finite R S] {x : S} :
norm R x = 0 ↔ x = 0 := by
constructor
on_goal 1 => let b := Module.Free.chooseBasis R S
swap
· rintro rfl; exact norm_zero
· letI := Classical.decEq (Module.Free.ChooseBasisIndex R S)
rw [norm_eq_matrix_det b, ← Matrix.exists_mulVec_eq_zero_iff]
rintro ⟨v, v_ne, hv⟩
rw [← b.equivFun.apply_symm_apply v, b.equivFun_symm_apply, b.equivFun_apply,
leftMulMatrix_mulVec_repr] at hv
refine (mul_eq_zero.mp (b.ext_elem fun i => ?_)).resolve_right (show ∑ i, v i • b i ≠ 0 from ?_)
· simpa only [LinearEquiv.map_zero, Pi.zero_apply] using congr_fun hv i
· contrapose! v_ne with sum_eq
apply b.equivFun.symm.injective
rw [b.equivFun_symm_apply, sum_eq, LinearEquiv.map_zero]
#align algebra.norm_eq_zero_iff Algebra.norm_eq_zero_iff
theorem norm_ne_zero_iff [IsDomain R] [IsDomain S] [Module.Free R S] [Module.Finite R S] {x : S} :
norm R x ≠ 0 ↔ x ≠ 0 := not_iff_not.mpr norm_eq_zero_iff
#align algebra.norm_ne_zero_iff Algebra.norm_ne_zero_iff
@[simp]
theorem norm_eq_zero_iff' [IsDomain R] [IsDomain S] [Module.Free R S] [Module.Finite R S] {x : S} :
LinearMap.det (LinearMap.mul R S x) = 0 ↔ x = 0 := norm_eq_zero_iff
#align algebra.norm_eq_zero_iff' Algebra.norm_eq_zero_iff'
| Mathlib/RingTheory/Norm.lean | 179 | 183 | theorem norm_eq_zero_iff_of_basis [IsDomain R] [IsDomain S] (b : Basis ι R S) {x : S} :
Algebra.norm R x = 0 ↔ x = 0 := by |
haveI : Module.Free R S := Module.Free.of_basis b
haveI : Module.Finite R S := Module.Finite.of_basis b
exact norm_eq_zero_iff
| 2,044 |
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Matrix.ToLinearEquiv
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
#align_import ring_theory.norm from "leanprover-community/mathlib"@"fecd3520d2a236856f254f27714b80dcfe28ea57"
universe u v w
variable {R S T : Type*} [CommRing R] [Ring S]
variable [Algebra R S]
variable {K L F : Type*} [Field K] [Field L] [Field F]
variable [Algebra K L] [Algebra K F]
variable {ι : Type w}
open FiniteDimensional
open LinearMap
open Matrix Polynomial
open scoped Matrix
namespace Algebra
variable (R)
noncomputable def norm : S →* R :=
LinearMap.det.comp (lmul R S).toRingHom.toMonoidHom
#align algebra.norm Algebra.norm
theorem norm_apply (x : S) : norm R x = LinearMap.det (lmul R S x) := rfl
#align algebra.norm_apply Algebra.norm_apply
theorem norm_eq_one_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) (x : S) :
norm R x = 1 := by rw [norm_apply, LinearMap.det]; split_ifs <;> trivial
#align algebra.norm_eq_one_of_not_exists_basis Algebra.norm_eq_one_of_not_exists_basis
variable {R}
theorem norm_eq_one_of_not_module_finite (h : ¬Module.Finite R S) (x : S) : norm R x = 1 := by
refine norm_eq_one_of_not_exists_basis _ (mt ?_ h) _
rintro ⟨s, ⟨b⟩⟩
exact Module.Finite.of_basis b
#align algebra.norm_eq_one_of_not_module_finite Algebra.norm_eq_one_of_not_module_finite
-- Can't be a `simp` lemma because it depends on a choice of basis
theorem norm_eq_matrix_det [Fintype ι] [DecidableEq ι] (b : Basis ι R S) (s : S) :
norm R s = Matrix.det (Algebra.leftMulMatrix b s) := by
rw [norm_apply, ← LinearMap.det_toMatrix b, ← toMatrix_lmul_eq]; rfl
#align algebra.norm_eq_matrix_det Algebra.norm_eq_matrix_det
theorem norm_algebraMap_of_basis [Fintype ι] (b : Basis ι R S) (x : R) :
norm R (algebraMap R S x) = x ^ Fintype.card ι := by
haveI := Classical.decEq ι
rw [norm_apply, ← det_toMatrix b, lmul_algebraMap]
convert @det_diagonal _ _ _ _ _ fun _ : ι => x
· ext (i j); rw [toMatrix_lsmul]
· rw [Finset.prod_const, Finset.card_univ]
#align algebra.norm_algebra_map_of_basis Algebra.norm_algebraMap_of_basis
@[simp]
protected theorem norm_algebraMap {L : Type*} [Ring L] [Algebra K L] (x : K) :
norm K (algebraMap K L x) = x ^ finrank K L := by
by_cases H : ∃ s : Finset L, Nonempty (Basis s K L)
· rw [norm_algebraMap_of_basis H.choose_spec.some, finrank_eq_card_basis H.choose_spec.some]
· rw [norm_eq_one_of_not_exists_basis K H, finrank_eq_zero_of_not_exists_basis, pow_zero]
rintro ⟨s, ⟨b⟩⟩
exact H ⟨s, ⟨b⟩⟩
#align algebra.norm_algebra_map Algebra.norm_algebraMap
open IntermediateField
variable (K)
| Mathlib/RingTheory/Norm.lean | 197 | 207 | theorem norm_eq_norm_adjoin [FiniteDimensional K L] [IsSeparable K L] (x : L) :
norm K x = norm K (AdjoinSimple.gen K x) ^ finrank K⟮x⟯ L := by |
letI := isSeparable_tower_top_of_isSeparable K K⟮x⟯ L
let pbL := Field.powerBasisOfFiniteOfSeparable K⟮x⟯ L
let pbx := IntermediateField.adjoin.powerBasis (IsSeparable.isIntegral K x)
-- This used to be `rw`, but we need `erw` after leanprover/lean4#2644
erw [← AdjoinSimple.algebraMap_gen K x, norm_eq_matrix_det (pbx.basis.smul pbL.basis) _,
smul_leftMulMatrix_algebraMap, det_blockDiagonal, norm_eq_matrix_det pbx.basis]
simp only [Finset.card_fin, Finset.prod_const]
congr
rw [← PowerBasis.finrank, AdjoinSimple.algebraMap_gen K x]
| 2,044 |
import Mathlib.FieldTheory.PrimitiveElement
import Mathlib.LinearAlgebra.Determinant
import Mathlib.LinearAlgebra.FiniteDimensional
import Mathlib.LinearAlgebra.Matrix.Charpoly.Minpoly
import Mathlib.LinearAlgebra.Matrix.ToLinearEquiv
import Mathlib.FieldTheory.IsAlgClosed.AlgebraicClosure
import Mathlib.FieldTheory.Galois
#align_import ring_theory.norm from "leanprover-community/mathlib"@"fecd3520d2a236856f254f27714b80dcfe28ea57"
universe u v w
variable {R S T : Type*} [CommRing R] [Ring S]
variable [Algebra R S]
variable {K L F : Type*} [Field K] [Field L] [Field F]
variable [Algebra K L] [Algebra K F]
variable {ι : Type w}
open FiniteDimensional
open LinearMap
open Matrix Polynomial
open scoped Matrix
namespace Algebra
variable (R)
noncomputable def norm : S →* R :=
LinearMap.det.comp (lmul R S).toRingHom.toMonoidHom
#align algebra.norm Algebra.norm
theorem norm_apply (x : S) : norm R x = LinearMap.det (lmul R S x) := rfl
#align algebra.norm_apply Algebra.norm_apply
theorem norm_eq_one_of_not_exists_basis (h : ¬∃ s : Finset S, Nonempty (Basis s R S)) (x : S) :
norm R x = 1 := by rw [norm_apply, LinearMap.det]; split_ifs <;> trivial
#align algebra.norm_eq_one_of_not_exists_basis Algebra.norm_eq_one_of_not_exists_basis
variable {R}
theorem norm_eq_one_of_not_module_finite (h : ¬Module.Finite R S) (x : S) : norm R x = 1 := by
refine norm_eq_one_of_not_exists_basis _ (mt ?_ h) _
rintro ⟨s, ⟨b⟩⟩
exact Module.Finite.of_basis b
#align algebra.norm_eq_one_of_not_module_finite Algebra.norm_eq_one_of_not_module_finite
-- Can't be a `simp` lemma because it depends on a choice of basis
theorem norm_eq_matrix_det [Fintype ι] [DecidableEq ι] (b : Basis ι R S) (s : S) :
norm R s = Matrix.det (Algebra.leftMulMatrix b s) := by
rw [norm_apply, ← LinearMap.det_toMatrix b, ← toMatrix_lmul_eq]; rfl
#align algebra.norm_eq_matrix_det Algebra.norm_eq_matrix_det
theorem norm_algebraMap_of_basis [Fintype ι] (b : Basis ι R S) (x : R) :
norm R (algebraMap R S x) = x ^ Fintype.card ι := by
haveI := Classical.decEq ι
rw [norm_apply, ← det_toMatrix b, lmul_algebraMap]
convert @det_diagonal _ _ _ _ _ fun _ : ι => x
· ext (i j); rw [toMatrix_lsmul]
· rw [Finset.prod_const, Finset.card_univ]
#align algebra.norm_algebra_map_of_basis Algebra.norm_algebraMap_of_basis
@[simp]
protected theorem norm_algebraMap {L : Type*} [Ring L] [Algebra K L] (x : K) :
norm K (algebraMap K L x) = x ^ finrank K L := by
by_cases H : ∃ s : Finset L, Nonempty (Basis s K L)
· rw [norm_algebraMap_of_basis H.choose_spec.some, finrank_eq_card_basis H.choose_spec.some]
· rw [norm_eq_one_of_not_exists_basis K H, finrank_eq_zero_of_not_exists_basis, pow_zero]
rintro ⟨s, ⟨b⟩⟩
exact H ⟨s, ⟨b⟩⟩
#align algebra.norm_algebra_map Algebra.norm_algebraMap
open IntermediateField
variable (K)
theorem norm_eq_norm_adjoin [FiniteDimensional K L] [IsSeparable K L] (x : L) :
norm K x = norm K (AdjoinSimple.gen K x) ^ finrank K⟮x⟯ L := by
letI := isSeparable_tower_top_of_isSeparable K K⟮x⟯ L
let pbL := Field.powerBasisOfFiniteOfSeparable K⟮x⟯ L
let pbx := IntermediateField.adjoin.powerBasis (IsSeparable.isIntegral K x)
-- This used to be `rw`, but we need `erw` after leanprover/lean4#2644
erw [← AdjoinSimple.algebraMap_gen K x, norm_eq_matrix_det (pbx.basis.smul pbL.basis) _,
smul_leftMulMatrix_algebraMap, det_blockDiagonal, norm_eq_matrix_det pbx.basis]
simp only [Finset.card_fin, Finset.prod_const]
congr
rw [← PowerBasis.finrank, AdjoinSimple.algebraMap_gen K x]
#align algebra.norm_eq_norm_adjoin Algebra.norm_eq_norm_adjoin
variable {K}
section IntermediateField
| Mathlib/RingTheory/Norm.lean | 214 | 221 | theorem _root_.IntermediateField.AdjoinSimple.norm_gen_eq_one {x : L} (hx : ¬IsIntegral K x) :
norm K (AdjoinSimple.gen K x) = 1 := by |
rw [norm_eq_one_of_not_exists_basis]
contrapose! hx
obtain ⟨s, ⟨b⟩⟩ := hx
refine .of_mem_of_fg K⟮x⟯.toSubalgebra ?_ x ?_
· exact (Submodule.fg_iff_finiteDimensional _).mpr (of_fintype_basis b)
· exact IntermediateField.subset_adjoin K _ (Set.mem_singleton x)
| 2,044 |
import Mathlib.LinearAlgebra.FreeModule.IdealQuotient
import Mathlib.RingTheory.Norm
#align_import linear_algebra.free_module.norm from "leanprover-community/mathlib"@"90b0d53ee6ffa910e5c2a977ce7e2fc704647974"
open Ideal Polynomial
open scoped Polynomial
variable {R S ι : Type*} [CommRing R] [IsDomain R] [IsPrincipalIdealRing R] [CommRing S]
[IsDomain S] [Algebra R S]
section CommRing
variable (F : Type*) [CommRing F] [Algebra F R] [Algebra F S] [IsScalarTower F R S]
| Mathlib/LinearAlgebra/FreeModule/Norm.lean | 30 | 50 | theorem associated_norm_prod_smith [Fintype ι] (b : Basis ι R S) {f : S} (hf : f ≠ 0) :
Associated (Algebra.norm R f) (∏ i, smithCoeffs b _ (span_singleton_eq_bot.not.2 hf) i) := by |
have hI := span_singleton_eq_bot.not.2 hf
let b' := ringBasis b (span {f}) hI
classical
rw [← Matrix.det_diagonal, ← LinearMap.det_toLin b']
let e :=
(b'.equiv ((span {f}).selfBasis b hI) <| Equiv.refl _).trans
((LinearEquiv.coord S S f hf).restrictScalars R)
refine (LinearMap.associated_det_of_eq_comp e _ _ ?_).symm
dsimp only [e, LinearEquiv.trans_apply]
simp_rw [← LinearEquiv.coe_toLinearMap, ← LinearMap.comp_apply, ← LinearMap.ext_iff]
refine b'.ext fun i => ?_
simp_rw [LinearMap.comp_apply, LinearEquiv.coe_toLinearMap, Matrix.toLin_apply, Basis.repr_self,
Finsupp.single_eq_pi_single, Matrix.diagonal_mulVec_single, Pi.single_apply, ite_smul,
zero_smul, Finset.sum_ite_eq', mul_one, if_pos (Finset.mem_univ _), b'.equiv_apply]
change _ = f * _
-- This used to be `rw`, but we need `erw` after leanprover/lean4#2644
erw [mul_comm, ← smul_eq_mul, LinearEquiv.restrictScalars_apply, LinearEquiv.coord_apply_smul,
Ideal.selfBasis_def]
rfl
| 2,045 |
import Mathlib.RingTheory.RootsOfUnity.Basic
import Mathlib.RingTheory.AdjoinRoot
import Mathlib.FieldTheory.Galois
import Mathlib.LinearAlgebra.Eigenspace.Minpoly
import Mathlib.RingTheory.Norm
universe u
variable {K : Type u} [Field K]
open Polynomial IntermediateField AdjoinRoot
section Splits
lemma root_X_pow_sub_C_pow (n : ℕ) (a : K) :
(AdjoinRoot.root (X ^ n - C a)) ^ n = AdjoinRoot.of _ a := by
rw [← sub_eq_zero, ← AdjoinRoot.eval₂_root, eval₂_sub, eval₂_C, eval₂_pow, eval₂_X]
lemma root_X_pow_sub_C_ne_zero {n : ℕ} (hn : 1 < n) (a : K) :
(AdjoinRoot.root (X ^ n - C a)) ≠ 0 :=
mk_ne_zero_of_natDegree_lt (monic_X_pow_sub_C _ (Nat.not_eq_zero_of_lt hn))
X_ne_zero <| by rwa [natDegree_X_pow_sub_C, natDegree_X]
lemma root_X_pow_sub_C_ne_zero' {n : ℕ} {a : K} (hn : 0 < n) (ha : a ≠ 0) :
(AdjoinRoot.root (X ^ n - C a)) ≠ 0 := by
obtain (rfl|hn) := (Nat.succ_le_iff.mpr hn).eq_or_lt
· rw [← Nat.one_eq_succ_zero, pow_one]
intro e
refine mk_ne_zero_of_natDegree_lt (monic_X_sub_C a) (C_ne_zero.mpr ha) (by simp) ?_
trans AdjoinRoot.mk (X - C a) (X - (X - C a))
· rw [sub_sub_cancel]
· rw [map_sub, mk_self, sub_zero, mk_X, e]
· exact root_X_pow_sub_C_ne_zero hn a
| Mathlib/FieldTheory/KummerExtension.lean | 74 | 82 | theorem X_pow_sub_C_splits_of_isPrimitiveRoot
{n : ℕ} {ζ : K} (hζ : IsPrimitiveRoot ζ n) {α a : K} (e : α ^ n = a) :
(X ^ n - C a).Splits (RingHom.id _) := by |
cases n.eq_zero_or_pos with
| inl hn =>
rw [hn, pow_zero, ← C.map_one, ← map_sub]
exact splits_C _ _
| inr hn =>
rw [splits_iff_card_roots, ← nthRoots, hζ.card_nthRoots, natDegree_X_pow_sub_C, if_pos ⟨α, e⟩]
| 2,046 |
import Mathlib.RingTheory.RootsOfUnity.Basic
import Mathlib.RingTheory.AdjoinRoot
import Mathlib.FieldTheory.Galois
import Mathlib.LinearAlgebra.Eigenspace.Minpoly
import Mathlib.RingTheory.Norm
universe u
variable {K : Type u} [Field K]
open Polynomial IntermediateField AdjoinRoot
section Splits
lemma root_X_pow_sub_C_pow (n : ℕ) (a : K) :
(AdjoinRoot.root (X ^ n - C a)) ^ n = AdjoinRoot.of _ a := by
rw [← sub_eq_zero, ← AdjoinRoot.eval₂_root, eval₂_sub, eval₂_C, eval₂_pow, eval₂_X]
lemma root_X_pow_sub_C_ne_zero {n : ℕ} (hn : 1 < n) (a : K) :
(AdjoinRoot.root (X ^ n - C a)) ≠ 0 :=
mk_ne_zero_of_natDegree_lt (monic_X_pow_sub_C _ (Nat.not_eq_zero_of_lt hn))
X_ne_zero <| by rwa [natDegree_X_pow_sub_C, natDegree_X]
lemma root_X_pow_sub_C_ne_zero' {n : ℕ} {a : K} (hn : 0 < n) (ha : a ≠ 0) :
(AdjoinRoot.root (X ^ n - C a)) ≠ 0 := by
obtain (rfl|hn) := (Nat.succ_le_iff.mpr hn).eq_or_lt
· rw [← Nat.one_eq_succ_zero, pow_one]
intro e
refine mk_ne_zero_of_natDegree_lt (monic_X_sub_C a) (C_ne_zero.mpr ha) (by simp) ?_
trans AdjoinRoot.mk (X - C a) (X - (X - C a))
· rw [sub_sub_cancel]
· rw [map_sub, mk_self, sub_zero, mk_X, e]
· exact root_X_pow_sub_C_ne_zero hn a
theorem X_pow_sub_C_splits_of_isPrimitiveRoot
{n : ℕ} {ζ : K} (hζ : IsPrimitiveRoot ζ n) {α a : K} (e : α ^ n = a) :
(X ^ n - C a).Splits (RingHom.id _) := by
cases n.eq_zero_or_pos with
| inl hn =>
rw [hn, pow_zero, ← C.map_one, ← map_sub]
exact splits_C _ _
| inr hn =>
rw [splits_iff_card_roots, ← nthRoots, hζ.card_nthRoots, natDegree_X_pow_sub_C, if_pos ⟨α, e⟩]
open BigOperators
-- make this private, as we only use it to prove a strictly more general version
private
| Mathlib/FieldTheory/KummerExtension.lean | 88 | 93 | theorem X_pow_sub_C_eq_prod'
{n : ℕ} {ζ : K} (hζ : IsPrimitiveRoot ζ n) {α a : K} (hn : 0 < n) (e : α ^ n = a) :
(X ^ n - C a) = ∏ i ∈ Finset.range n, (X - C (ζ ^ i * α)) := by |
rw [eq_prod_roots_of_monic_of_splits_id (monic_X_pow_sub_C _ (Nat.pos_iff_ne_zero.mp hn))
(X_pow_sub_C_splits_of_isPrimitiveRoot hζ e), ← nthRoots, hζ.nthRoots_eq e, Multiset.map_map]
rfl
| 2,046 |
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.RingTheory.Trace
import Mathlib.RingTheory.Norm
#align_import ring_theory.discriminant from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
open scoped Matrix
open Matrix FiniteDimensional Fintype Polynomial Finset IntermediateField
namespace Algebra
variable (A : Type u) {B : Type v} (C : Type z) {ι : Type w} [DecidableEq ι]
variable [CommRing A] [CommRing B] [Algebra A B] [CommRing C] [Algebra A C]
section Discr
-- Porting note: using `[DecidableEq ι]` instead of `by classical...` did not work in
-- mathlib3.
noncomputable def discr (A : Type u) {B : Type v} [CommRing A] [CommRing B] [Algebra A B]
[Fintype ι] (b : ι → B) := (traceMatrix A b).det
#align algebra.discr Algebra.discr
theorem discr_def [Fintype ι] (b : ι → B) : discr A b = (traceMatrix A b).det := rfl
variable {A C} in
| Mathlib/RingTheory/Discriminant.lean | 76 | 79 | theorem discr_eq_discr_of_algEquiv [Fintype ι] (b : ι → B) (f : B ≃ₐ[A] C) :
Algebra.discr A b = Algebra.discr A (f ∘ b) := by |
rw [discr_def]; congr; ext
simp_rw [traceMatrix_apply, traceForm_apply, Function.comp, ← map_mul f, trace_eq_of_algEquiv]
| 2,047 |
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.RingTheory.Trace
import Mathlib.RingTheory.Norm
#align_import ring_theory.discriminant from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
open scoped Matrix
open Matrix FiniteDimensional Fintype Polynomial Finset IntermediateField
namespace Algebra
variable (A : Type u) {B : Type v} (C : Type z) {ι : Type w} [DecidableEq ι]
variable [CommRing A] [CommRing B] [Algebra A B] [CommRing C] [Algebra A C]
section Discr
-- Porting note: using `[DecidableEq ι]` instead of `by classical...` did not work in
-- mathlib3.
noncomputable def discr (A : Type u) {B : Type v} [CommRing A] [CommRing B] [Algebra A B]
[Fintype ι] (b : ι → B) := (traceMatrix A b).det
#align algebra.discr Algebra.discr
theorem discr_def [Fintype ι] (b : ι → B) : discr A b = (traceMatrix A b).det := rfl
variable {A C} in
theorem discr_eq_discr_of_algEquiv [Fintype ι] (b : ι → B) (f : B ≃ₐ[A] C) :
Algebra.discr A b = Algebra.discr A (f ∘ b) := by
rw [discr_def]; congr; ext
simp_rw [traceMatrix_apply, traceForm_apply, Function.comp, ← map_mul f, trace_eq_of_algEquiv]
#align algebra.discr_def Algebra.discr_def
variable {ι' : Type*} [Fintype ι'] [Fintype ι] [DecidableEq ι']
section Basic
@[simp]
| Mathlib/RingTheory/Discriminant.lean | 88 | 89 | theorem discr_reindex (b : Basis ι A B) (f : ι ≃ ι') : discr A (b ∘ ⇑f.symm) = discr A b := by |
classical rw [← Basis.coe_reindex, discr_def, traceMatrix_reindex, det_reindex_self, ← discr_def]
| 2,047 |
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.RingTheory.Trace
import Mathlib.RingTheory.Norm
#align_import ring_theory.discriminant from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
open scoped Matrix
open Matrix FiniteDimensional Fintype Polynomial Finset IntermediateField
namespace Algebra
variable (A : Type u) {B : Type v} (C : Type z) {ι : Type w} [DecidableEq ι]
variable [CommRing A] [CommRing B] [Algebra A B] [CommRing C] [Algebra A C]
section Discr
-- Porting note: using `[DecidableEq ι]` instead of `by classical...` did not work in
-- mathlib3.
noncomputable def discr (A : Type u) {B : Type v} [CommRing A] [CommRing B] [Algebra A B]
[Fintype ι] (b : ι → B) := (traceMatrix A b).det
#align algebra.discr Algebra.discr
theorem discr_def [Fintype ι] (b : ι → B) : discr A b = (traceMatrix A b).det := rfl
variable {A C} in
theorem discr_eq_discr_of_algEquiv [Fintype ι] (b : ι → B) (f : B ≃ₐ[A] C) :
Algebra.discr A b = Algebra.discr A (f ∘ b) := by
rw [discr_def]; congr; ext
simp_rw [traceMatrix_apply, traceForm_apply, Function.comp, ← map_mul f, trace_eq_of_algEquiv]
#align algebra.discr_def Algebra.discr_def
variable {ι' : Type*} [Fintype ι'] [Fintype ι] [DecidableEq ι']
section Basic
@[simp]
theorem discr_reindex (b : Basis ι A B) (f : ι ≃ ι') : discr A (b ∘ ⇑f.symm) = discr A b := by
classical rw [← Basis.coe_reindex, discr_def, traceMatrix_reindex, det_reindex_self, ← discr_def]
#align algebra.discr_reindex Algebra.discr_reindex
| Mathlib/RingTheory/Discriminant.lean | 93 | 106 | theorem discr_zero_of_not_linearIndependent [IsDomain A] {b : ι → B}
(hli : ¬LinearIndependent A b) : discr A b = 0 := by |
classical
obtain ⟨g, hg, i, hi⟩ := Fintype.not_linearIndependent_iff.1 hli
have : (traceMatrix A b) *ᵥ g = 0 := by
ext i
have : ∀ j, (trace A B) (b i * b j) * g j = (trace A B) (g j • b j * b i) := by
intro j;
simp [mul_comm]
simp only [mulVec, dotProduct, traceMatrix_apply, Pi.zero_apply, traceForm_apply, fun j =>
this j, ← map_sum, ← sum_mul, hg, zero_mul, LinearMap.map_zero]
by_contra h
rw [discr_def] at h
simp [Matrix.eq_zero_of_mulVec_eq_zero h this] at hi
| 2,047 |
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.RingTheory.Trace
import Mathlib.RingTheory.Norm
#align_import ring_theory.discriminant from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
open scoped Matrix
open Matrix FiniteDimensional Fintype Polynomial Finset IntermediateField
namespace Algebra
variable (A : Type u) {B : Type v} (C : Type z) {ι : Type w} [DecidableEq ι]
variable [CommRing A] [CommRing B] [Algebra A B] [CommRing C] [Algebra A C]
section Discr
-- Porting note: using `[DecidableEq ι]` instead of `by classical...` did not work in
-- mathlib3.
noncomputable def discr (A : Type u) {B : Type v} [CommRing A] [CommRing B] [Algebra A B]
[Fintype ι] (b : ι → B) := (traceMatrix A b).det
#align algebra.discr Algebra.discr
theorem discr_def [Fintype ι] (b : ι → B) : discr A b = (traceMatrix A b).det := rfl
variable {A C} in
theorem discr_eq_discr_of_algEquiv [Fintype ι] (b : ι → B) (f : B ≃ₐ[A] C) :
Algebra.discr A b = Algebra.discr A (f ∘ b) := by
rw [discr_def]; congr; ext
simp_rw [traceMatrix_apply, traceForm_apply, Function.comp, ← map_mul f, trace_eq_of_algEquiv]
#align algebra.discr_def Algebra.discr_def
variable {ι' : Type*} [Fintype ι'] [Fintype ι] [DecidableEq ι']
section Basic
@[simp]
theorem discr_reindex (b : Basis ι A B) (f : ι ≃ ι') : discr A (b ∘ ⇑f.symm) = discr A b := by
classical rw [← Basis.coe_reindex, discr_def, traceMatrix_reindex, det_reindex_self, ← discr_def]
#align algebra.discr_reindex Algebra.discr_reindex
theorem discr_zero_of_not_linearIndependent [IsDomain A] {b : ι → B}
(hli : ¬LinearIndependent A b) : discr A b = 0 := by
classical
obtain ⟨g, hg, i, hi⟩ := Fintype.not_linearIndependent_iff.1 hli
have : (traceMatrix A b) *ᵥ g = 0 := by
ext i
have : ∀ j, (trace A B) (b i * b j) * g j = (trace A B) (g j • b j * b i) := by
intro j;
simp [mul_comm]
simp only [mulVec, dotProduct, traceMatrix_apply, Pi.zero_apply, traceForm_apply, fun j =>
this j, ← map_sum, ← sum_mul, hg, zero_mul, LinearMap.map_zero]
by_contra h
rw [discr_def] at h
simp [Matrix.eq_zero_of_mulVec_eq_zero h this] at hi
#align algebra.discr_zero_of_not_linear_independent Algebra.discr_zero_of_not_linearIndependent
variable {A}
| Mathlib/RingTheory/Discriminant.lean | 113 | 116 | theorem discr_of_matrix_vecMul (b : ι → B) (P : Matrix ι ι A) :
discr A (b ᵥ* P.map (algebraMap A B)) = P.det ^ 2 * discr A b := by |
rw [discr_def, traceMatrix_of_matrix_vecMul, det_mul, det_mul, det_transpose, mul_comm, ←
mul_assoc, discr_def, pow_two]
| 2,047 |
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.RingTheory.Trace
import Mathlib.RingTheory.Norm
#align_import ring_theory.discriminant from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
open scoped Matrix
open Matrix FiniteDimensional Fintype Polynomial Finset IntermediateField
namespace Algebra
variable (A : Type u) {B : Type v} (C : Type z) {ι : Type w} [DecidableEq ι]
variable [CommRing A] [CommRing B] [Algebra A B] [CommRing C] [Algebra A C]
section Discr
-- Porting note: using `[DecidableEq ι]` instead of `by classical...` did not work in
-- mathlib3.
noncomputable def discr (A : Type u) {B : Type v} [CommRing A] [CommRing B] [Algebra A B]
[Fintype ι] (b : ι → B) := (traceMatrix A b).det
#align algebra.discr Algebra.discr
theorem discr_def [Fintype ι] (b : ι → B) : discr A b = (traceMatrix A b).det := rfl
variable {A C} in
theorem discr_eq_discr_of_algEquiv [Fintype ι] (b : ι → B) (f : B ≃ₐ[A] C) :
Algebra.discr A b = Algebra.discr A (f ∘ b) := by
rw [discr_def]; congr; ext
simp_rw [traceMatrix_apply, traceForm_apply, Function.comp, ← map_mul f, trace_eq_of_algEquiv]
#align algebra.discr_def Algebra.discr_def
variable {ι' : Type*} [Fintype ι'] [Fintype ι] [DecidableEq ι']
section Basic
@[simp]
theorem discr_reindex (b : Basis ι A B) (f : ι ≃ ι') : discr A (b ∘ ⇑f.symm) = discr A b := by
classical rw [← Basis.coe_reindex, discr_def, traceMatrix_reindex, det_reindex_self, ← discr_def]
#align algebra.discr_reindex Algebra.discr_reindex
theorem discr_zero_of_not_linearIndependent [IsDomain A] {b : ι → B}
(hli : ¬LinearIndependent A b) : discr A b = 0 := by
classical
obtain ⟨g, hg, i, hi⟩ := Fintype.not_linearIndependent_iff.1 hli
have : (traceMatrix A b) *ᵥ g = 0 := by
ext i
have : ∀ j, (trace A B) (b i * b j) * g j = (trace A B) (g j • b j * b i) := by
intro j;
simp [mul_comm]
simp only [mulVec, dotProduct, traceMatrix_apply, Pi.zero_apply, traceForm_apply, fun j =>
this j, ← map_sum, ← sum_mul, hg, zero_mul, LinearMap.map_zero]
by_contra h
rw [discr_def] at h
simp [Matrix.eq_zero_of_mulVec_eq_zero h this] at hi
#align algebra.discr_zero_of_not_linear_independent Algebra.discr_zero_of_not_linearIndependent
variable {A}
theorem discr_of_matrix_vecMul (b : ι → B) (P : Matrix ι ι A) :
discr A (b ᵥ* P.map (algebraMap A B)) = P.det ^ 2 * discr A b := by
rw [discr_def, traceMatrix_of_matrix_vecMul, det_mul, det_mul, det_transpose, mul_comm, ←
mul_assoc, discr_def, pow_two]
#align algebra.discr_of_matrix_vec_mul Algebra.discr_of_matrix_vecMul
| Mathlib/RingTheory/Discriminant.lean | 121 | 124 | theorem discr_of_matrix_mulVec (b : ι → B) (P : Matrix ι ι A) :
discr A (P.map (algebraMap A B) *ᵥ b) = P.det ^ 2 * discr A b := by |
rw [discr_def, traceMatrix_of_matrix_mulVec, det_mul, det_mul, det_transpose, mul_comm, ←
mul_assoc, discr_def, pow_two]
| 2,047 |
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.RingTheory.Trace
import Mathlib.RingTheory.Norm
#align_import ring_theory.discriminant from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
open scoped Matrix
open Matrix FiniteDimensional Fintype Polynomial Finset IntermediateField
namespace Algebra
variable (A : Type u) {B : Type v} (C : Type z) {ι : Type w} [DecidableEq ι]
variable [CommRing A] [CommRing B] [Algebra A B] [CommRing C] [Algebra A C]
section Discr
-- Porting note: using `[DecidableEq ι]` instead of `by classical...` did not work in
-- mathlib3.
noncomputable def discr (A : Type u) {B : Type v} [CommRing A] [CommRing B] [Algebra A B]
[Fintype ι] (b : ι → B) := (traceMatrix A b).det
#align algebra.discr Algebra.discr
theorem discr_def [Fintype ι] (b : ι → B) : discr A b = (traceMatrix A b).det := rfl
variable {A C} in
theorem discr_eq_discr_of_algEquiv [Fintype ι] (b : ι → B) (f : B ≃ₐ[A] C) :
Algebra.discr A b = Algebra.discr A (f ∘ b) := by
rw [discr_def]; congr; ext
simp_rw [traceMatrix_apply, traceForm_apply, Function.comp, ← map_mul f, trace_eq_of_algEquiv]
#align algebra.discr_def Algebra.discr_def
variable {ι' : Type*} [Fintype ι'] [Fintype ι] [DecidableEq ι']
section Field
variable (K : Type u) {L : Type v} (E : Type z) [Field K] [Field L] [Field E]
variable [Algebra K L] [Algebra K E]
variable [Module.Finite K L] [IsAlgClosed E]
| Mathlib/RingTheory/Discriminant.lean | 136 | 139 | theorem discr_not_zero_of_basis [IsSeparable K L] (b : Basis ι K L) :
discr K b ≠ 0 := by |
rw [discr_def, traceMatrix_of_basis, ← LinearMap.BilinForm.nondegenerate_iff_det_ne_zero]
exact traceForm_nondegenerate _ _
| 2,047 |
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.RingTheory.Trace
import Mathlib.RingTheory.Norm
#align_import ring_theory.discriminant from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
open scoped Matrix
open Matrix FiniteDimensional Fintype Polynomial Finset IntermediateField
namespace Algebra
variable (A : Type u) {B : Type v} (C : Type z) {ι : Type w} [DecidableEq ι]
variable [CommRing A] [CommRing B] [Algebra A B] [CommRing C] [Algebra A C]
section Discr
-- Porting note: using `[DecidableEq ι]` instead of `by classical...` did not work in
-- mathlib3.
noncomputable def discr (A : Type u) {B : Type v} [CommRing A] [CommRing B] [Algebra A B]
[Fintype ι] (b : ι → B) := (traceMatrix A b).det
#align algebra.discr Algebra.discr
theorem discr_def [Fintype ι] (b : ι → B) : discr A b = (traceMatrix A b).det := rfl
variable {A C} in
theorem discr_eq_discr_of_algEquiv [Fintype ι] (b : ι → B) (f : B ≃ₐ[A] C) :
Algebra.discr A b = Algebra.discr A (f ∘ b) := by
rw [discr_def]; congr; ext
simp_rw [traceMatrix_apply, traceForm_apply, Function.comp, ← map_mul f, trace_eq_of_algEquiv]
#align algebra.discr_def Algebra.discr_def
variable {ι' : Type*} [Fintype ι'] [Fintype ι] [DecidableEq ι']
section Field
variable (K : Type u) {L : Type v} (E : Type z) [Field K] [Field L] [Field E]
variable [Algebra K L] [Algebra K E]
variable [Module.Finite K L] [IsAlgClosed E]
theorem discr_not_zero_of_basis [IsSeparable K L] (b : Basis ι K L) :
discr K b ≠ 0 := by
rw [discr_def, traceMatrix_of_basis, ← LinearMap.BilinForm.nondegenerate_iff_det_ne_zero]
exact traceForm_nondegenerate _ _
#align algebra.discr_not_zero_of_basis Algebra.discr_not_zero_of_basis
theorem discr_isUnit_of_basis [IsSeparable K L] (b : Basis ι K L) : IsUnit (discr K b) :=
IsUnit.mk0 _ (discr_not_zero_of_basis _ _)
#align algebra.discr_is_unit_of_basis Algebra.discr_isUnit_of_basis
variable (b : ι → L) (pb : PowerBasis K L)
| Mathlib/RingTheory/Discriminant.lean | 154 | 157 | theorem discr_eq_det_embeddingsMatrixReindex_pow_two [IsSeparable K L] (e : ι ≃ (L →ₐ[K] E)) :
algebraMap K E (discr K b) = (embeddingsMatrixReindex K E b e).det ^ 2 := by |
rw [discr_def, RingHom.map_det, RingHom.mapMatrix_apply,
traceMatrix_eq_embeddingsMatrixReindex_mul_trans, det_mul, det_transpose, pow_two]
| 2,047 |
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.RingTheory.Trace
import Mathlib.RingTheory.Norm
#align_import ring_theory.discriminant from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
open scoped Matrix
open Matrix FiniteDimensional Fintype Polynomial Finset IntermediateField
namespace Algebra
variable (A : Type u) {B : Type v} (C : Type z) {ι : Type w} [DecidableEq ι]
variable [CommRing A] [CommRing B] [Algebra A B] [CommRing C] [Algebra A C]
section Discr
-- Porting note: using `[DecidableEq ι]` instead of `by classical...` did not work in
-- mathlib3.
noncomputable def discr (A : Type u) {B : Type v} [CommRing A] [CommRing B] [Algebra A B]
[Fintype ι] (b : ι → B) := (traceMatrix A b).det
#align algebra.discr Algebra.discr
theorem discr_def [Fintype ι] (b : ι → B) : discr A b = (traceMatrix A b).det := rfl
variable {A C} in
theorem discr_eq_discr_of_algEquiv [Fintype ι] (b : ι → B) (f : B ≃ₐ[A] C) :
Algebra.discr A b = Algebra.discr A (f ∘ b) := by
rw [discr_def]; congr; ext
simp_rw [traceMatrix_apply, traceForm_apply, Function.comp, ← map_mul f, trace_eq_of_algEquiv]
#align algebra.discr_def Algebra.discr_def
variable {ι' : Type*} [Fintype ι'] [Fintype ι] [DecidableEq ι']
section Field
variable (K : Type u) {L : Type v} (E : Type z) [Field K] [Field L] [Field E]
variable [Algebra K L] [Algebra K E]
variable [Module.Finite K L] [IsAlgClosed E]
theorem discr_not_zero_of_basis [IsSeparable K L] (b : Basis ι K L) :
discr K b ≠ 0 := by
rw [discr_def, traceMatrix_of_basis, ← LinearMap.BilinForm.nondegenerate_iff_det_ne_zero]
exact traceForm_nondegenerate _ _
#align algebra.discr_not_zero_of_basis Algebra.discr_not_zero_of_basis
theorem discr_isUnit_of_basis [IsSeparable K L] (b : Basis ι K L) : IsUnit (discr K b) :=
IsUnit.mk0 _ (discr_not_zero_of_basis _ _)
#align algebra.discr_is_unit_of_basis Algebra.discr_isUnit_of_basis
variable (b : ι → L) (pb : PowerBasis K L)
theorem discr_eq_det_embeddingsMatrixReindex_pow_two [IsSeparable K L] (e : ι ≃ (L →ₐ[K] E)) :
algebraMap K E (discr K b) = (embeddingsMatrixReindex K E b e).det ^ 2 := by
rw [discr_def, RingHom.map_det, RingHom.mapMatrix_apply,
traceMatrix_eq_embeddingsMatrixReindex_mul_trans, det_mul, det_transpose, pow_two]
#align algebra.discr_eq_det_embeddings_matrix_reindex_pow_two Algebra.discr_eq_det_embeddingsMatrixReindex_pow_two
| Mathlib/RingTheory/Discriminant.lean | 161 | 167 | theorem discr_powerBasis_eq_prod (e : Fin pb.dim ≃ (L →ₐ[K] E)) [IsSeparable K L] :
algebraMap K E (discr K pb.basis) =
∏ i : Fin pb.dim, ∏ j ∈ Ioi i, (e j pb.gen - e i pb.gen) ^ 2 := by |
rw [discr_eq_det_embeddingsMatrixReindex_pow_two K E pb.basis e,
embeddingsMatrixReindex_eq_vandermonde, det_transpose, det_vandermonde, ← prod_pow]
congr; ext i
rw [← prod_pow]
| 2,047 |
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.RingTheory.Trace
import Mathlib.RingTheory.Norm
#align_import ring_theory.discriminant from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
open scoped Matrix
open Matrix FiniteDimensional Fintype Polynomial Finset IntermediateField
namespace Algebra
variable (A : Type u) {B : Type v} (C : Type z) {ι : Type w} [DecidableEq ι]
variable [CommRing A] [CommRing B] [Algebra A B] [CommRing C] [Algebra A C]
section Discr
-- Porting note: using `[DecidableEq ι]` instead of `by classical...` did not work in
-- mathlib3.
noncomputable def discr (A : Type u) {B : Type v} [CommRing A] [CommRing B] [Algebra A B]
[Fintype ι] (b : ι → B) := (traceMatrix A b).det
#align algebra.discr Algebra.discr
theorem discr_def [Fintype ι] (b : ι → B) : discr A b = (traceMatrix A b).det := rfl
variable {A C} in
theorem discr_eq_discr_of_algEquiv [Fintype ι] (b : ι → B) (f : B ≃ₐ[A] C) :
Algebra.discr A b = Algebra.discr A (f ∘ b) := by
rw [discr_def]; congr; ext
simp_rw [traceMatrix_apply, traceForm_apply, Function.comp, ← map_mul f, trace_eq_of_algEquiv]
#align algebra.discr_def Algebra.discr_def
variable {ι' : Type*} [Fintype ι'] [Fintype ι] [DecidableEq ι']
section Field
variable (K : Type u) {L : Type v} (E : Type z) [Field K] [Field L] [Field E]
variable [Algebra K L] [Algebra K E]
variable [Module.Finite K L] [IsAlgClosed E]
theorem discr_not_zero_of_basis [IsSeparable K L] (b : Basis ι K L) :
discr K b ≠ 0 := by
rw [discr_def, traceMatrix_of_basis, ← LinearMap.BilinForm.nondegenerate_iff_det_ne_zero]
exact traceForm_nondegenerate _ _
#align algebra.discr_not_zero_of_basis Algebra.discr_not_zero_of_basis
theorem discr_isUnit_of_basis [IsSeparable K L] (b : Basis ι K L) : IsUnit (discr K b) :=
IsUnit.mk0 _ (discr_not_zero_of_basis _ _)
#align algebra.discr_is_unit_of_basis Algebra.discr_isUnit_of_basis
variable (b : ι → L) (pb : PowerBasis K L)
theorem discr_eq_det_embeddingsMatrixReindex_pow_two [IsSeparable K L] (e : ι ≃ (L →ₐ[K] E)) :
algebraMap K E (discr K b) = (embeddingsMatrixReindex K E b e).det ^ 2 := by
rw [discr_def, RingHom.map_det, RingHom.mapMatrix_apply,
traceMatrix_eq_embeddingsMatrixReindex_mul_trans, det_mul, det_transpose, pow_two]
#align algebra.discr_eq_det_embeddings_matrix_reindex_pow_two Algebra.discr_eq_det_embeddingsMatrixReindex_pow_two
theorem discr_powerBasis_eq_prod (e : Fin pb.dim ≃ (L →ₐ[K] E)) [IsSeparable K L] :
algebraMap K E (discr K pb.basis) =
∏ i : Fin pb.dim, ∏ j ∈ Ioi i, (e j pb.gen - e i pb.gen) ^ 2 := by
rw [discr_eq_det_embeddingsMatrixReindex_pow_two K E pb.basis e,
embeddingsMatrixReindex_eq_vandermonde, det_transpose, det_vandermonde, ← prod_pow]
congr; ext i
rw [← prod_pow]
#align algebra.discr_power_basis_eq_prod Algebra.discr_powerBasis_eq_prod
| Mathlib/RingTheory/Discriminant.lean | 171 | 176 | theorem discr_powerBasis_eq_prod' [IsSeparable K L] (e : Fin pb.dim ≃ (L →ₐ[K] E)) :
algebraMap K E (discr K pb.basis) =
∏ i : Fin pb.dim, ∏ j ∈ Ioi i, -((e j pb.gen - e i pb.gen) * (e i pb.gen - e j pb.gen)) := by |
rw [discr_powerBasis_eq_prod _ _ _ e]
congr; ext i; congr; ext j
ring
| 2,047 |
import Mathlib.RingTheory.IntegrallyClosed
import Mathlib.RingTheory.Trace
import Mathlib.RingTheory.Norm
#align_import ring_theory.discriminant from "leanprover-community/mathlib"@"3e068ece210655b7b9a9477c3aff38a492400aa1"
universe u v w z
open scoped Matrix
open Matrix FiniteDimensional Fintype Polynomial Finset IntermediateField
namespace Algebra
variable (A : Type u) {B : Type v} (C : Type z) {ι : Type w} [DecidableEq ι]
variable [CommRing A] [CommRing B] [Algebra A B] [CommRing C] [Algebra A C]
section Discr
-- Porting note: using `[DecidableEq ι]` instead of `by classical...` did not work in
-- mathlib3.
noncomputable def discr (A : Type u) {B : Type v} [CommRing A] [CommRing B] [Algebra A B]
[Fintype ι] (b : ι → B) := (traceMatrix A b).det
#align algebra.discr Algebra.discr
theorem discr_def [Fintype ι] (b : ι → B) : discr A b = (traceMatrix A b).det := rfl
variable {A C} in
theorem discr_eq_discr_of_algEquiv [Fintype ι] (b : ι → B) (f : B ≃ₐ[A] C) :
Algebra.discr A b = Algebra.discr A (f ∘ b) := by
rw [discr_def]; congr; ext
simp_rw [traceMatrix_apply, traceForm_apply, Function.comp, ← map_mul f, trace_eq_of_algEquiv]
#align algebra.discr_def Algebra.discr_def
variable {ι' : Type*} [Fintype ι'] [Fintype ι] [DecidableEq ι']
section Field
variable (K : Type u) {L : Type v} (E : Type z) [Field K] [Field L] [Field E]
variable [Algebra K L] [Algebra K E]
variable [Module.Finite K L] [IsAlgClosed E]
theorem discr_not_zero_of_basis [IsSeparable K L] (b : Basis ι K L) :
discr K b ≠ 0 := by
rw [discr_def, traceMatrix_of_basis, ← LinearMap.BilinForm.nondegenerate_iff_det_ne_zero]
exact traceForm_nondegenerate _ _
#align algebra.discr_not_zero_of_basis Algebra.discr_not_zero_of_basis
theorem discr_isUnit_of_basis [IsSeparable K L] (b : Basis ι K L) : IsUnit (discr K b) :=
IsUnit.mk0 _ (discr_not_zero_of_basis _ _)
#align algebra.discr_is_unit_of_basis Algebra.discr_isUnit_of_basis
variable (b : ι → L) (pb : PowerBasis K L)
theorem discr_eq_det_embeddingsMatrixReindex_pow_two [IsSeparable K L] (e : ι ≃ (L →ₐ[K] E)) :
algebraMap K E (discr K b) = (embeddingsMatrixReindex K E b e).det ^ 2 := by
rw [discr_def, RingHom.map_det, RingHom.mapMatrix_apply,
traceMatrix_eq_embeddingsMatrixReindex_mul_trans, det_mul, det_transpose, pow_two]
#align algebra.discr_eq_det_embeddings_matrix_reindex_pow_two Algebra.discr_eq_det_embeddingsMatrixReindex_pow_two
theorem discr_powerBasis_eq_prod (e : Fin pb.dim ≃ (L →ₐ[K] E)) [IsSeparable K L] :
algebraMap K E (discr K pb.basis) =
∏ i : Fin pb.dim, ∏ j ∈ Ioi i, (e j pb.gen - e i pb.gen) ^ 2 := by
rw [discr_eq_det_embeddingsMatrixReindex_pow_two K E pb.basis e,
embeddingsMatrixReindex_eq_vandermonde, det_transpose, det_vandermonde, ← prod_pow]
congr; ext i
rw [← prod_pow]
#align algebra.discr_power_basis_eq_prod Algebra.discr_powerBasis_eq_prod
theorem discr_powerBasis_eq_prod' [IsSeparable K L] (e : Fin pb.dim ≃ (L →ₐ[K] E)) :
algebraMap K E (discr K pb.basis) =
∏ i : Fin pb.dim, ∏ j ∈ Ioi i, -((e j pb.gen - e i pb.gen) * (e i pb.gen - e j pb.gen)) := by
rw [discr_powerBasis_eq_prod _ _ _ e]
congr; ext i; congr; ext j
ring
#align algebra.discr_power_basis_eq_prod' Algebra.discr_powerBasis_eq_prod'
local notation "n" => finrank K L
| Mathlib/RingTheory/Discriminant.lean | 182 | 210 | theorem discr_powerBasis_eq_prod'' [IsSeparable K L] (e : Fin pb.dim ≃ (L →ₐ[K] E)) :
algebraMap K E (discr K pb.basis) =
(-1) ^ (n * (n - 1) / 2) *
∏ i : Fin pb.dim, ∏ j ∈ Ioi i, (e j pb.gen - e i pb.gen) * (e i pb.gen - e j pb.gen) := by |
rw [discr_powerBasis_eq_prod' _ _ _ e]
simp_rw [fun i j => neg_eq_neg_one_mul ((e j pb.gen - e i pb.gen) * (e i pb.gen - e j pb.gen)),
prod_mul_distrib]
congr
simp only [prod_pow_eq_pow_sum, prod_const]
congr
rw [← @Nat.cast_inj ℚ, Nat.cast_sum]
have : ∀ x : Fin pb.dim, ↑x + 1 ≤ pb.dim := by simp [Nat.succ_le_iff, Fin.is_lt]
simp_rw [Fin.card_Ioi, Nat.sub_sub, add_comm 1]
simp only [Nat.cast_sub, this, Finset.card_fin, nsmul_eq_mul, sum_const, sum_sub_distrib,
Nat.cast_add, Nat.cast_one, sum_add_distrib, mul_one]
rw [← Nat.cast_sum, ← @Finset.sum_range ℕ _ pb.dim fun i => i, sum_range_id]
have hn : n = pb.dim := by
rw [← AlgHom.card K L E, ← Fintype.card_fin pb.dim]
-- FIXME: Without the `Fintype` namespace, why does it complain about `Finset.card_congr` being
-- deprecated?
exact Fintype.card_congr e.symm
have h₂ : 2 ∣ pb.dim * (pb.dim - 1) := pb.dim.even_mul_pred_self.two_dvd
have hne : ((2 : ℕ) : ℚ) ≠ 0 := by simp
have hle : 1 ≤ pb.dim := by
rw [← hn, Nat.one_le_iff_ne_zero, ← zero_lt_iff, FiniteDimensional.finrank_pos_iff]
infer_instance
rw [hn, Nat.cast_div h₂ hne, Nat.cast_mul, Nat.cast_sub hle]
field_simp
ring
| 2,047 |
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