Module

ArithmeticFrobeniusRestrictTower.lean

Nyll.ClassFieldTheory.Theorems.FrobeniusAndHilbertClassFields.ArithmeticFrobeniusRestrictTower
2 declarations indexed from sourceView source ↗

Arithmetic Frobenius in a finite abelian tower

At a prime unramified in the top field, restriction of arithmetic Frobenius to an intermediate field is arithmetic Frobenius at the prime below it.

Declarations

ClassFieldTheory.arithmeticFinitePlacePrimeArtin_restrict_tower_of_globalArtin
Source context 5 commands

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

open scoped NumberField
noncomputable section
namespace ClassFieldTheory
open NumberField IsDedekindDomain IdeleGroup
open GlobalClassFieldTheory.GlobalClassFields
theorem arithmeticFinitePlacePrimeArtin_restrict_tower_of_globalArtin
    (K E L : Type) [Field K] [Field E] [Field L]
    [NumberField K] [NumberField E] [NumberField L]
    [Algebra K E] [Algebra E L] [Algebra K L] [IsScalarTower K E L]
    [IsAbelianGalois K E] [IsAbelianGalois K L]
    (v : HeightOneSpectrum (𝓞 K)) :
    AlgEquiv.restrictNormalHom E
        (arithmeticFinitePlacePrimeArtin (K := K) (L := L) v) =
      arithmeticFinitePlacePrimeArtin (K := K) (L := E) v
ClassFieldTheory.arithmeticFrobeniusAt_restrict_tower

In a finite abelian tower K ⊆ E ⊆ L, arithmetic Frobenius at an unramified prime of L restricts to arithmetic Frobenius at the specified prime of E below it.

Source context 5 commands

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

open scoped NumberField
noncomputable section
namespace ClassFieldTheory
open NumberField IsDedekindDomain IdeleGroup
open GlobalClassFieldTheory.GlobalClassFields
theorem arithmeticFrobeniusAt_restrict_tower
    {K E L : Type}
    [Field K] [NumberField K]
    [Field E] [NumberField E]
    [Field L] [NumberField L]
    [Algebra K E] [Algebra E L] [Algebra K L] [IsScalarTower K E L]
    [IsAbelianGalois K E] [IsAbelianGalois K L]
    (v : HeightOneSpectrum (𝓞 K))
    (wE : HeightOneSpectrum (𝓞 E))
    (wL : HeightOneSpectrum (𝓞 L))
    (hwE : wE.asIdeal.LiesOver v.asIdeal)
    (hwL : wL.asIdeal.LiesOver wE.asIdeal)
    (hunram : Algebra.IsUnramifiedAt (𝓞 K) wL.asIdeal) :
    AlgEquiv.restrictNormalHom E (arithmeticFrobeniusAt (K := K) wL) =
      arithmeticFrobeniusAt (K := K) wE