Module

RealProPFrobeniusFixedField.lean

Nyll.SawinTotallyRealTowers.RealProPFrobeniusFixedField
6 declarations indexed from sourceView source ↗

The actual fixed field of a Frobenius cut

Take the fixed field of the constructed closed normal subgroup inside the maximal real extension, then lift it into the same algebraic closure of ℚ. Its Galois group is the actual quotient from S3.

Imports9
Imported by2

Declarations

ClassFieldTower.Sawin.fixedFieldMaximalIsGalois
Source context 7 commands

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

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
namespace ClassFieldTower.Sawin
open ProCGroups.Presentations
variable (p : ℕ) (T : Set (HeightOneSpectrum (𝓞 ℚ)))
variable (v : ℕ → HeightOneSpectrum (𝓞 ℚ))
instance fixedFieldMaximalIsGalois :
    IsGalois ℚ (maximalRealProPOutside p T)
ClassFieldTower.Sawin.realProPFrobeniusFixedField

The Frobenius-cut fixed field in the original algebraic closure.

Source context 8 commands

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

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
namespace ClassFieldTower.Sawin
open ProCGroups.Presentations
variable (p : ℕ) (T : Set (HeightOneSpectrum (𝓞 ℚ)))
variable (v : ℕ → HeightOneSpectrum (𝓞 ℚ))
private local instance fixedFieldMaximalIsGalois :
    IsGalois ℚ (maximalRealProPOutside p T) :=
  maximalRealProPOutside_isGalois p T
def realProPFrobeniusFixedField : IntermediateField ℚ (AlgebraicClosure ℚ)
ClassFieldTower.Sawin.realProPFrobeniusFixedField_le

The constructed cut field is contained in its actual maximal parent.

Source context 8 commands

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

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
namespace ClassFieldTower.Sawin
open ProCGroups.Presentations
variable (p : ℕ) (T : Set (HeightOneSpectrum (𝓞 ℚ)))
variable (v : ℕ → HeightOneSpectrum (𝓞 ℚ))
private local instance fixedFieldMaximalIsGalois :
    IsGalois ℚ (maximalRealProPOutside p T) :=
  maximalRealProPOutside_isGalois p T
theorem realProPFrobeniusFixedField_le :
    realProPFrobeniusFixedField p T v ≤ maximalRealProPOutside p T
ClassFieldTower.Sawin.realProPFrobeniusFixedField_isGalois

Normality of the actual cut kernel makes its fixed field Galois over ℚ.

Source context 8 commands

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

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
namespace ClassFieldTower.Sawin
open ProCGroups.Presentations
variable (p : ℕ) (T : Set (HeightOneSpectrum (𝓞 ℚ)))
variable (v : ℕ → HeightOneSpectrum (𝓞 ℚ))
private local instance fixedFieldMaximalIsGalois :
    IsGalois ℚ (maximalRealProPOutside p T) :=
  maximalRealProPOutside_isGalois p T
theorem realProPFrobeniusFixedField_isGalois :
    IsGalois ℚ (realProPFrobeniusFixedField p T v)
ClassFieldTower.Sawin.realProPFrobeniusFixedField_isTotallyReal

Total reality descends to the internal fixed field and is preserved by its lift.

Source context 8 commands

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

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
namespace ClassFieldTower.Sawin
open ProCGroups.Presentations
variable (p : ℕ) (T : Set (HeightOneSpectrum (𝓞 ℚ)))
variable (v : ℕ → HeightOneSpectrum (𝓞 ℚ))
private local instance fixedFieldMaximalIsGalois :
    IsGalois ℚ (maximalRealProPOutside p T) :=
  maximalRealProPOutside_isGalois p T
theorem realProPFrobeniusFixedField_isTotallyReal :
    IsTotallyReal (realProPFrobeniusFixedField p T v)
ClassFieldTower.Sawin.realProPFrobeniusCutEquivFixedField

The actual S3 quotient is the full Galois group of the constructed cut field.

Source context 8 commands

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

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
namespace ClassFieldTower.Sawin
open ProCGroups.Presentations
variable (p : ℕ) (T : Set (HeightOneSpectrum (𝓞 ℚ)))
variable (v : ℕ → HeightOneSpectrum (𝓞 ℚ))
private local instance fixedFieldMaximalIsGalois :
    IsGalois ℚ (maximalRealProPOutside p T) :=
  maximalRealProPOutside_isGalois p T
def realProPFrobeniusCutEquivFixedField :
    RealProPFrobeniusCut p T v ≃*
      (realProPFrobeniusFixedField p T v ≃ₐ[ℚ] realProPFrobeniusFixedField p T v)