Module

Comparison.lean

Nyll.ClassFieldTheory.AlgebraicNumberTheory.Completion.Comparison
17 declarations indexed from sourceView source ↗

Comparing finite-place completion models

For an exact extension w of the normalized absolute value at a finite place v of K, its centre W is a finite place of L. The absolute values w and the standard normalized absolute value at W differ by a positive real power. Consequently the identity on L extends to a ring equivalence between their completions and preserves the valuation ring.

Composing with the existing comparison between the standard absolute-value completion and mathlib's concrete adic completion gives the local factor comparison used in the adelic restricted-product bridge.

Declarations

The standard absolute value at the centre of an exact extension has the same valuation subring as that exact extension.

Source context 7 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
omit [FiniteDimensional K L] in
theorem finitePlaceExtension_adicAbv_valuationSubring
    (v : HeightOneSpectrum (𝓞 K))
    (w : AbsoluteValueExtension
      (HeightOneSpectrum.adicAbv K v) L) :
    absoluteValueValuationSubring
        (HeightOneSpectrum.adicAbv L
          (finitePlaceExtensionCentre
            (K := K) (L := L) v w))
        (finitePlaceExtension_nonarchimedean
          (K := L) (L := L)
          (finitePlaceExtensionCentre
            (K := K) (L := L) v w)
          ⟨HeightOneSpectrum.adicAbv L
              (finitePlaceExtensionCentre
                (K := K) (L := L) v w),
            fun _ => rfl⟩) =
      finitePlaceExtensionValuationSubring
        (K := K) (L := L) v w := by
  rw [finitePlaceExtensionValuationSubring_eq_localization,
    (finitePlaceExtensionCentre
      (K := K) (L := L) v w).valuationSubringAtPrime_eq_valuationSubring]
  ext x
  rw [mem_absoluteValueValuationSubring_iff]
  change
    HeightOneSpectrum.adicAbv L
        (finitePlaceExtensionCentre
          (K := K) (L := L) v w) x ≤ 1 ↔
      (finitePlaceExtensionCentre
        (K := K) (L := L) v w).valuation L x ≤ 1
  rw [HeightOneSpectrum.adicAbv_def]
  exact_mod_cast
    WithZeroMulInt.toNNReal_le_one_iff
      (HeightOneSpectrum.one_lt_absNorm_nnreal
        (finitePlaceExtensionCentre
          (K := K) (L := L) v w))

The exact extension and the standard absolute value at its centre are equivalent absolute values.

Source context 7 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
omit [FiniteDimensional K L] in
theorem finitePlaceExtension_isEquiv_adicAbv
    (v : HeightOneSpectrum (𝓞 K))
    (w : AbsoluteValueExtension
      (HeightOneSpectrum.adicAbv K v) L) :
    w.1.IsEquiv
      (HeightOneSpectrum.adicAbv L
        (finitePlaceExtensionCentre
          (K := K) (L := L) v w))

The positive exponent relating an exact extension to the standard absolute value at its centre.

Source context 6 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
def finitePlaceExtensionExponent
    (v : HeightOneSpectrum (𝓞 K))
    (w : AbsoluteValueExtension
      (HeightOneSpectrum.adicAbv K v) L) : ℝ
Source context 7 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
omit [FiniteDimensional K L] in
theorem finitePlaceExtensionExponent_pos
    (v : HeightOneSpectrum (𝓞 K))
    (w : AbsoluteValueExtension
      (HeightOneSpectrum.adicAbv K v) L) :
    0 < finitePlaceExtensionExponent
      (K := K) (L := L) v w
Source context 7 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
omit [FiniteDimensional K L] in
theorem finitePlaceExtension_adicAbv_eq_rpow
    (v : HeightOneSpectrum (𝓞 K))
    (w : AbsoluteValueExtension
      (HeightOneSpectrum.adicAbv K v) L)
    (x : L) :
    HeightOneSpectrum.adicAbv L
        (finitePlaceExtensionCentre
          (K := K) (L := L) v w) x =
      w.1 x ^ finitePlaceExtensionExponent
        (K := K) (L := L) v w

The identity on L, regarded as a ring equivalence between the two normed copies determined by the equivalent absolute values.

Source context 6 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
def finitePlaceExtensionWithAbsRingEquiv
    (v : HeightOneSpectrum (𝓞 K))
    (w : AbsoluteValueExtension
      (HeightOneSpectrum.adicAbv K v) L) :
    WithAbs w.1 ≃+*
      WithAbs
        (HeightOneSpectrum.adicAbv L
          (finitePlaceExtensionCentre
            (K := K) (L := L) v w))
Source context 7 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
omit [FiniteDimensional K L] in
theorem finitePlaceExtensionWithAbsRingEquiv_continuous
    (v : HeightOneSpectrum (𝓞 K))
    (w : AbsoluteValueExtension
      (HeightOneSpectrum.adicAbv K v) L) :
    Continuous
      (finitePlaceExtensionWithAbsRingEquiv
        (K := K) (L := L) v w)
Source context 7 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
omit [FiniteDimensional K L] in
theorem finitePlaceExtensionWithAbsRingEquiv_symm_continuous
    (v : HeightOneSpectrum (𝓞 K))
    (w : AbsoluteValueExtension
      (HeightOneSpectrum.adicAbv K v) L) :
    Continuous
      (finitePlaceExtensionWithAbsRingEquiv
        (K := K) (L := L) v w).symm

The completion comparison induced by the identity on L.

Source context 6 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
def finitePlaceExtensionCompletionRingEquiv
    (v : HeightOneSpectrum (𝓞 K))
    (w : AbsoluteValueExtension
      (HeightOneSpectrum.adicAbv K v) L) :
    w.1.Completion ≃+*
      (HeightOneSpectrum.adicAbv L
        (finitePlaceExtensionCentre
          (K := K) (L := L) v w)).Completion
Source context 7 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
omit [FiniteDimensional K L] in
theorem finitePlaceExtensionCompletionRingEquiv_toCompletion
    (v : HeightOneSpectrum (𝓞 K))
    (w : AbsoluteValueExtension
      (HeightOneSpectrum.adicAbv K v) L)
    (x : L) :
    finitePlaceExtensionCompletionRingEquiv
        (K := K) (L := L) v w
        (AbsoluteValue.toCompletion w.1 x) =
      AbsoluteValue.toCompletion
        (HeightOneSpectrum.adicAbv L
          (finitePlaceExtensionCentre
            (K := K) (L := L) v w)) x

The completion comparison is continuous.

Source context 7 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
omit [FiniteDimensional K L] in
theorem finitePlaceExtensionCompletionRingEquiv_continuous
    (v : HeightOneSpectrum (𝓞 K))
    (w : AbsoluteValueExtension
      (HeightOneSpectrum.adicAbv K v) L) :
    Continuous
      (finitePlaceExtensionCompletionRingEquiv
        (K := K) (L := L) v w)

The norm on the standard completion is the positive power of the norm on the exact-extension completion.

Source context 7 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
omit [FiniteDimensional K L] in
theorem finitePlaceExtensionCompletionRingEquiv_norm
    (v : HeightOneSpectrum (𝓞 K))
    (w : AbsoluteValueExtension
      (HeightOneSpectrum.adicAbv K v) L)
    (x : w.1.Completion) :
    ‖finitePlaceExtensionCompletionRingEquiv
        (K := K) (L := L) v w x‖ =
      ‖x‖ ^ finitePlaceExtensionExponent
        (K := K) (L := L) v w

The existing comparison from the standard absolute-value completion to the concrete adic completion is an isometry.

Source context 6 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
theorem relativeFinitePlaceCompletionRingEquiv_norm
    (W : HeightOneSpectrum (𝓞 L))
    (x : (HeightOneSpectrum.adicAbv L W).Completion) :
    ‖relativeFinitePlaceCompletionRingEquiv W x‖ = ‖x‖

The local factor comparison from an exact-extension completion to the concrete completion at its centre.

Source context 6 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
def finitePlaceExtensionAdicCompletionRingEquiv
    (v : HeightOneSpectrum (𝓞 K))
    (w : AbsoluteValueExtension
      (HeightOneSpectrum.adicAbv K v) L) :
    w.1.Completion ≃+*
      (finitePlaceExtensionCentre
        (K := K) (L := L) v w).adicCompletion L
Source context 7 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
omit [FiniteDimensional K L] in
theorem finitePlaceExtensionAdicCompletionRingEquiv_norm
    (v : HeightOneSpectrum (𝓞 K))
    (w : AbsoluteValueExtension
      (HeightOneSpectrum.adicAbv K v) L)
    (x : w.1.Completion) :
    ‖finitePlaceExtensionAdicCompletionRingEquiv
        (K := K) (L := L) v w x‖ =
      ‖x‖ ^ finitePlaceExtensionExponent
        (K := K) (L := L) v w
Source context 7 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
omit [FiniteDimensional K L] in
theorem finitePlaceExtensionAdicCompletionRingEquiv_toCompletion
    (v : HeightOneSpectrum (𝓞 K))
    (w : AbsoluteValueExtension
      (HeightOneSpectrum.adicAbv K v) L)
    (x : L) :
    finitePlaceExtensionAdicCompletionRingEquiv
        (K := K) (L := L) v w
        (AbsoluteValue.toCompletion w.1 x) =
      FinitePlace.embedding
        (finitePlaceExtensionCentre
          (K := K) (L := L) v w) x

The local factor comparison identifies the valuation ring in the exact-extension completion with the concrete adic integers.

Source context 7 commands

Surrounding namespaces, section variables, and local commands at this declaration.

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
open AlgebraicNumberTheory.Valuations
universe u v
variable
    {K : Type u} {L : Type v}
    [Field K] [NumberField K]
    [Field L] [NumberField L] [Algebra K L]
    [FiniteDimensional K L]
omit [FiniteDimensional K L] in
theorem finitePlaceExtensionAdicCompletionRingEquiv_mem_integers_iff
    (v : HeightOneSpectrum (𝓞 K))
    (w : AbsoluteValueExtension
      (HeightOneSpectrum.adicAbv K v) L)
    (x : w.1.Completion) :
    finitePlaceExtensionAdicCompletionRingEquiv
          (K := K) (L := L) v w x ∈
        (finitePlaceExtensionCentre
          (K := K) (L := L) v w).adicCompletionIntegers L ↔
      x ∈ absoluteValueCompletionIntegers w.1
        (absoluteValueExtension_isNonarchimedean
          (HeightOneSpectrum.adicAbv K v)
          (HeightOneSpectrum.isNonarchimedean_adicAbv K v) w)