Theorem: FractionalIdeal.abs_det_basis_change
File: Mathlib/RingTheory/FractionalIdeal/Norm.lean

Proof steps:
state_before: R : Type u_1
inst✝¹¹ : CommRing R
inst✝¹⁰ : IsDedekindDomain R
inst✝⁹ : Module.Free ℤ R
inst✝⁸ : Module.Finite ℤ R
K : Type u_2
inst✝⁷ : CommRing K
inst✝⁶ : Algebra R K
inst✝⁵ : IsFractionRing R K
inst✝⁴ : IsLocalization (Algebra.algebraMapSubmonoid R ℤ⁰) K
inst✝³ : Algebra ℚ K
inst✝² : NoZeroDivisors K
ι : Type u_3
inst✝¹ : Fintype ι
inst✝ : DecidableEq ι
b : Basis ι ℤ R
I : FractionalIdeal R⁰ K
bI : Basis ι ℤ ↥↑I
⊢ |(Basis.localizationLocalization ℚ ℤ⁰ K b).det (Subtype.val ∘ ⇑bI)| = absNorm I
state_after: R : Type u_1
inst✝¹¹ : CommRing R
inst✝¹⁰ : IsDedekindDomain R
inst✝⁹ : Module.Free ℤ R
inst✝⁸ : Module.Finite ℤ R
K : Type u_2
inst✝⁷ : CommRing K
inst✝⁶ : Algebra R K
inst✝⁵ : IsFractionRing R K
inst✝⁴ : IsLocalization (Algebra.algebraMapSubmonoid R ℤ⁰) K
inst✝³ : Algebra ℚ K
inst✝² : NoZeroDivisors K
ι : Type u_3
inst✝¹ : Fintype ι
inst✝ : DecidableEq ι
b : Basis ι ℤ R
I : FractionalIdeal R⁰ K
bI : Basis ι ℤ ↥↑I
this : Nontrivial K
⊢ |(Basis.localizationLocalization ℚ ℤ⁰ K b).det (Subtype.val ∘ ⇑bI)| = absNorm I
tactic: have := IsFractionRing.nontrivial R K
state_before: R : Type u_1
inst✝¹¹ : CommRing R
inst✝¹⁰ : IsDedekindDomain R
inst✝⁹ : Module.Free ℤ R
inst✝⁸ : Module.Finite ℤ R
K : Type u_2
inst✝⁷ : CommRing K
inst✝⁶ : Algebra R K
inst✝⁵ : IsFractionRing R K
inst✝⁴ : IsLocalization (Algebra.algebraMapSubmonoid R ℤ⁰) K
inst✝³ : Algebra ℚ K
inst✝² : NoZeroDivisors K
ι : Type u_3
inst✝¹ : Fintype ι
inst✝ : DecidableEq ι
b : Basis ι ℤ R
I : FractionalIdeal R⁰ K
bI : Basis ι ℤ ↥↑I
this : Nontrivial K
⊢ |(Basis.localizationLocalization ℚ ℤ⁰ K b).det (Subtype.val ∘ ⇑bI)| = absNorm I
state_after: R : Type u_1
inst✝¹¹ : CommRing R
inst✝¹⁰ : IsDedekindDomain R
inst✝⁹ : Module.Free ℤ R
inst✝⁸ : Module.Finite ℤ R
K : Type u_2
inst✝⁷ : CommRing K
inst✝⁶ : Algebra R K
inst✝⁵ : IsFractionRing R K
inst✝⁴ : IsLocalization (Algebra.algebraMapSubmonoid R ℤ⁰) K
inst✝³ : Algebra ℚ K
inst✝² : NoZeroDivisors K
ι : Type u_3
inst✝¹ : Fintype ι
inst✝ : DecidableEq ι
b : Basis ι ℤ R
I : FractionalIdeal R⁰ K
bI : Basis ι ℤ ↥↑I
this : Nontrivial K
b₀ : Basis ι ℚ K := Basis.localizationLocalization ℚ ℤ⁰ K b
⊢ |(Basis.localizationLocalization ℚ ℤ⁰ K b).det (Subtype.val ∘ ⇑bI)| = absNorm I
tactic: let b₀ : Basis ι ℚ K := b.localizationLocalization ℚ ℤ⁰ K
state_before: R : Type u_1
inst✝¹¹ : CommRing R
inst✝¹⁰ : IsDedekindDomain R
inst✝⁹ : Module.Free ℤ R
inst✝⁸ : Module.Finite ℤ R
K : Type u_2
inst✝⁷ : CommRing K
inst✝⁶ : Algebra R K
inst✝⁵ : IsFractionRing R K
inst✝⁴ : IsLocalization (Algebra.algebraMapSubmonoid R ℤ⁰) K
inst✝³ : Algebra ℚ K
inst✝² : NoZeroDivisors K
ι : Type u_3
inst✝¹ : Fintype ι
inst✝ : DecidableEq ι
b : Basis ι ℤ R
I : FractionalIdeal R⁰ K
bI : Basis ι ℤ ↥↑I
this : Nontrivial K
b₀ : Basis ι ℚ K := Basis.localizationLocalization ℚ ℤ⁰ K b
⊢ |(Basis.localizationLocalization ℚ ℤ⁰ K b).det (Subtype.val ∘ ⇑bI)| = absNorm I
state_after: R : Type u_1
inst✝¹¹ : CommRing R
inst✝¹⁰ : IsDedekindDomain R
inst✝⁹ : Module.Free ℤ R
inst✝⁸ : Module.Finite ℤ R
K : Type u_2
inst✝⁷ : CommRing K
inst✝⁶ : Algebra R K
inst✝⁵ : IsFractionRing R K
inst✝⁴ : IsLocalization (Algebra.algebraMapSubmonoid R ℤ⁰) K
inst✝³ : Algebra ℚ K
inst✝² : NoZeroDivisors K
ι : Type u_3
inst✝¹ : Fintype ι
inst✝ : DecidableEq ι
b : Basis ι ℤ R
I : FractionalIdeal R⁰ K
bI : Basis ι ℤ ↥↑I
this : Nontrivial K
b₀ : Basis ι ℚ K := Basis.localizationLocalization ℚ ℤ⁰ K b
bI.num : Basis ι ℤ ↥I.num := bI.map (LinearEquiv.restrictScalars ℤ (equivNum ⋯))
⊢ |(Basis.localizationLocalization ℚ ℤ⁰ K b).det (Subtype.val ∘ ⇑bI)| = absNorm I
tactic: let bI.num : Basis ι ℤ I.num := bI.map
      ((equivNum (nonZeroDivisors.coe_ne_zero _)).restrictScalars ℤ)
state_before: R : Type u_1
inst✝¹¹ : CommRing R
inst✝¹⁰ : IsDedekindDomain R
inst✝⁹ : Module.Free ℤ R
inst✝⁸ : Module.Finite ℤ R
K : Type u_2
inst✝⁷ : CommRing K
inst✝⁶ : Algebra R K
inst✝⁵ : IsFractionRing R K
inst✝⁴ : IsLocalization (Algebra.algebraMapSubmonoid R ℤ⁰) K
inst✝³ : Algebra ℚ K
inst✝² : NoZeroDivisors K
ι : Type u_3
inst✝¹ : Fintype ι
inst✝ : DecidableEq ι
b : Basis ι ℤ R
I : FractionalIdeal R⁰ K
bI : Basis ι ℤ ↥↑I
this : Nontrivial K
b₀ : Basis ι ℚ K := Basis.localizationLocalization ℚ ℤ⁰ K b
bI.num : Basis ι ℤ ↥I.num := bI.map (LinearEquiv.restrictScalars ℤ (equivNum ⋯))
⊢ |(Basis.localizationLocalization ℚ ℤ⁰ K b).det (Subtype.val ∘ ⇑bI)| = absNorm I
state_after: R : Type u_1
inst✝¹¹ : CommRing R
inst✝¹⁰ : IsDedekindDomain R
inst✝⁹ : Module.Free ℤ R
inst✝⁸ : Module.Finite ℤ R
K : Type u_2
inst✝⁷ : CommRing K
inst✝⁶ : Algebra R K
inst✝⁵ : IsFractionRing R K
inst✝⁴ : IsLocalization (Algebra.algebraMapSubmonoid R ℤ⁰) K
inst✝³ : Algebra ℚ K
inst✝² : NoZeroDivisors K
ι : Type u_3
inst✝¹ : Fintype ι
inst✝ : DecidableEq ι
b : Basis ι ℤ R
I : FractionalIdeal R⁰ K
bI : Basis ι ℤ ↥↑I
this : Nontrivial K
b₀ : Basis ι ℚ K := Basis.localizationLocalization ℚ ℤ⁰ K b
bI.num : Basis ι ℤ ↥I.num := bI.map (LinearEquiv.restrictScalars ℤ (equivNum ⋯))
⊢ |((Basis.localizationLocalization ℚ ℤ⁰ K b).toMatrix (Subtype.val ∘ ⇑bI)).det| =
    |↑(b.toMatrix (Subtype.val ∘ ⇑bI.num)).det| / |↑((Algebra.norm ℤ) ↑I.den)|
tactic: rw [absNorm_eq, ← Ideal.natAbs_det_basis_change b I.num bI.num, Int.cast_natAbs, Int.cast_abs,
    Int.cast_abs, Basis.det_apply, Basis.det_apply]
state_before: R : Type u_1
inst✝¹¹ : CommRing R
inst✝¹⁰ : IsDedekindDomain R
inst✝⁹ : Module.Free ℤ R
inst✝⁸ : Module.Finite ℤ R
K : Type u_2
inst✝⁷ : CommRing K
inst✝⁶ : Algebra R K
inst✝⁵ : IsFractionRing R K
inst✝⁴ : IsLocalization (Algebra.algebraMapSubmonoid R ℤ⁰) K
inst✝³ : Algebra ℚ K
inst✝² : NoZeroDivisors K
ι : Type u_3
inst✝¹ : Fintype ι
inst✝ : DecidableEq ι
b : Basis ι ℤ R
I : FractionalIdeal R⁰ K
bI : Basis ι ℤ ↥↑I
this : Nontrivial K
b₀ : Basis ι ℚ K := Basis.localizationLocalization ℚ ℤ⁰ K b
bI.num : Basis ι ℤ ↥I.num := bI.map (LinearEquiv.restrictScalars ℤ (equivNum ⋯))
⊢ |((Basis.localizationLocalization ℚ ℤ⁰ K b).toMatrix (Subtype.val ∘ ⇑bI)).det| =
    |↑(b.toMatrix (Subtype.val ∘ ⇑bI.num)).det| / |↑((Algebra.norm ℤ) ↑I.den)|
state_after: R : Type u_1
inst✝¹¹ : CommRing R
inst✝¹⁰ : IsDedekindDomain R
inst✝⁹ : Module.Free ℤ R
inst✝⁸ : Module.Finite ℤ R
K : Type u_2
inst✝⁷ : CommRing K
inst✝⁶ : Algebra R K
inst✝⁵ : IsFractionRing R K
inst✝⁴ : IsLocalization (Algebra.algebraMapSubmonoid R ℤ⁰) K
inst✝³ : Algebra ℚ K
inst✝² : NoZeroDivisors K
ι : Type u_3
inst✝¹ : Fintype ι
inst✝ : DecidableEq ι
b : Basis ι ℤ R
I : FractionalIdeal R⁰ K
bI : Basis ι ℤ ↥↑I
this : Nontrivial K
b₀ : Basis ι ℚ K := Basis.localizationLocalization ℚ ℤ⁰ K b
bI.num : Basis ι ℤ ↥I.num := bI.map (LinearEquiv.restrictScalars ℤ (equivNum ⋯))
⊢ |((Basis.localizationLocalization ℚ ℤ⁰ K b).toMatrix (Subtype.val ∘ ⇑bI)).det| =
    |(algebraMap ℤ ℚ) (b.toMatrix (Subtype.val ∘ ⇑bI.num)).det| / |↑((Algebra.norm ℤ) ↑I.den)|
tactic: change _ = |algebraMap ℤ ℚ _| / _
state_before: R : Type u_1
inst✝¹¹ : CommRing R
inst✝¹⁰ : IsDedekindDomain R
inst✝⁹ : Module.Free ℤ R
inst✝⁸ : Module.Finite ℤ R
K : Type u_2
inst✝⁷ : CommRing K
inst✝⁶ : Algebra R K
inst✝⁵ : IsFractionRing R K
inst✝⁴ : IsLocalization (Algebra.algebraMapSubmonoid R ℤ⁰) K
inst✝³ : Algebra ℚ K
inst✝² : NoZeroDivisors K
ι : Type u_3
inst✝¹ : Fintype ι
inst✝ : DecidableEq ι
b : Basis ι ℤ R
I : FractionalIdeal R⁰ K
bI : Basis ι ℤ ↥↑I
this : Nontrivial K
b₀ : Basis ι ℚ K := Basis.localizationLocalization ℚ ℤ⁰ K b
bI.num : Basis ι ℤ ↥I.num := bI.map (LinearEquiv.restrictScalars ℤ (equivNum ⋯))
⊢ |((Basis.localizationLocalization ℚ ℤ⁰ K b).toMatrix (Subtype.val ∘ ⇑bI)).det| =
    |(algebraMap ℤ ℚ) (b.toMatrix (Subtype.val ∘ ⇑bI.num)).det| / |↑((Algebra.norm ℤ) ↑I.den)|
state_after: R : Type u_1
inst✝¹¹ : CommRing R
inst✝¹⁰ : IsDedekindDomain R
inst✝⁹ : Module.Free ℤ R
inst✝⁸ : Module.Finite ℤ R
K : Type u_2
inst✝⁷ : CommRing K
inst✝⁶ : Algebra R K
inst✝⁵ : IsFractionRing R K
inst✝⁴ : IsLocalization (Algebra.algebraMapSubmonoid R ℤ⁰) K
inst✝³ : Algebra ℚ K
inst✝² : NoZeroDivisors K
ι : Type u_3
inst✝¹ : Fintype ι
inst✝ : DecidableEq ι
b : Basis ι ℤ R
I : FractionalIdeal R⁰ K
bI : Basis ι ℤ ↥↑I
this : Nontrivial K
b₀ : Basis ι ℚ K := Basis.localizationLocalization ℚ ℤ⁰ K b
bI.num : Basis ι ℤ ↥I.num := bI.map (LinearEquiv.restrictScalars ℤ (equivNum ⋯))
⊢ |((Basis.localizationLocalization ℚ ℤ⁰ K b).toMatrix (Subtype.val ∘ ⇑bI)).det| =
    |(b₀.toMatrix ((algebraMap R K) ↑I.den • Subtype.val ∘ ⇑bI)).det| / |↑((Algebra.norm ℤ) ↑I.den)|
tactic: rw [RingHom.map_det, show RingHom.mapMatrix (algebraMap ℤ ℚ) (b.toMatrix ((↑) ∘ bI.num)) =
      b₀.toMatrix ((algebraMap R K (den I : R)) • ((↑) ∘ bI)) by
    ext : 2
    simp_rw [bI.num, RingHom.mapMatrix_apply, Matrix.map_apply, Basis.toMatrix_apply,
      ← Basis.localizationLocalization_repr_algebraMap ℚ ℤ⁰ K, Function.comp_apply,
      Basis.map_apply, LinearEquiv.restrictScalars_apply, equivNum_apply, Submonoid.smul_def,
      Algebra.smul_def]
    rfl]
state_before: R : Type u_1
inst✝¹¹ : CommRing R
inst✝¹⁰ : IsDedekindDomain R
inst✝⁹ : Module.Free ℤ R
inst✝⁸ : Module.Finite ℤ R
K : Type u_2
inst✝⁷ : CommRing K
inst✝⁶ : Algebra R K
inst✝⁵ : IsFractionRing R K
inst✝⁴ : IsLocalization (Algebra.algebraMapSubmonoid R ℤ⁰) K
inst✝³ : Algebra ℚ K
inst✝² : NoZeroDivisors K
ι : Type u_3
inst✝¹ : Fintype ι
inst✝ : DecidableEq ι
b : Basis ι ℤ R
I : FractionalIdeal R⁰ K
bI : Basis ι ℤ ↥↑I
this : Nontrivial K
b₀ : Basis ι ℚ K := Basis.localizationLocalization ℚ ℤ⁰ K b
bI.num : Basis ι ℤ ↥I.num := bI.map (LinearEquiv.restrictScalars ℤ (equivNum ⋯))
⊢ |((Basis.localizationLocalization ℚ ℤ⁰ K b).toMatrix (Subtype.val ∘ ⇑bI)).det| =
    |(b₀.toMatrix ((algebraMap R K) ↑I.den • Subtype.val ∘ ⇑bI)).det| / |↑((Algebra.norm ℤ) ↑I.den)|
state_after: no goals
tactic: rw [Basis.toMatrix_smul, Matrix.det_mul, abs_mul, ← Algebra.norm_eq_matrix_det,
    Algebra.norm_localization ℤ ℤ⁰, show (Algebra.norm ℤ (den I : R) : ℚ) =
    algebraMap ℤ ℚ (Algebra.norm ℤ (den I : R)) by rfl, mul_div_assoc, mul_div_cancel₀ _ (by
    rw [ne_eq, abs_eq_zero, IsFractionRing.to_map_eq_zero_iff, Algebra.norm_eq_zero_iff_of_basis b]
    exact nonZeroDivisors.coe_ne_zero _)]