Module

CompletedFrobeniusFixedFieldGeneration.lean

Nyll.ClassFieldTheory.LubinTate.EqualCharacteristic.CompletedLevel.CompletedFrobeniusFixedFieldGeneration
4 declarations indexed from sourceView source ↗

The completed theta-intertwining theorem: generation of the completed Frobenius fixed field

The coefficient-descent inclusion and the already proved fixedness of the direct theta value identify the fixed field with its simple Laurent-base extension.

Declarations

LubinTate.EqualCharacteristic.equalCharacteristicCompletedFrobeniusFixedFieldGenerationBaseAlgebra
Source context 7 commands

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

noncomputable section
open scoped LaurentSeries Polynomial PowerSeries
universe u v
namespace LubinTate
namespace EqualCharacteristic
open LocalFieldTheory.DiscreteValuationField
variable {K : Type u} [Field K]
instance
    equalCharacteristicCompletedFrobeniusFixedFieldGenerationBaseAlgebra
    (F : LocalField.{u, v} K) :
    Algebra F.residueField⸨X⸩
      (equalCharacteristicCompletedUnramifiedField F.residueField)
LubinTate.EqualCharacteristic.equalCharacteristicCompletedFrobeniusFixedFieldGenerationLevelAlgebra
Source context 8 commands

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

noncomputable section
open scoped LaurentSeries Polynomial PowerSeries
universe u v
namespace LubinTate
namespace EqualCharacteristic
open LocalFieldTheory.DiscreteValuationField
variable {K : Type u} [Field K]
noncomputable local instance
    equalCharacteristicCompletedFrobeniusFixedFieldGenerationBaseAlgebra
    (F : LocalField.{u, v} K) :
    Algebra F.residueField⸨X⸩
      (equalCharacteristicCompletedUnramifiedField F.residueField) :=
  laurentSeriesCoefficientAlgebra
instance
    equalCharacteristicCompletedFrobeniusFixedFieldGenerationLevelAlgebra
    (F : LocalField.{u, v} K) (n : ℕ) :
    Algebra F.residueField⸨X⸩
      (equalCharacteristicCompletedLevelField F n)
LubinTate.EqualCharacteristic.equalCharacteristicCompletedFrobeniusFixedFieldGenerationScalarTower
Source context 9 commands

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

noncomputable section
open scoped LaurentSeries Polynomial PowerSeries
universe u v
namespace LubinTate
namespace EqualCharacteristic
open LocalFieldTheory.DiscreteValuationField
variable {K : Type u} [Field K]
noncomputable local instance
    equalCharacteristicCompletedFrobeniusFixedFieldGenerationBaseAlgebra
    (F : LocalField.{u, v} K) :
    Algebra F.residueField⸨X⸩
      (equalCharacteristicCompletedUnramifiedField F.residueField) :=
  laurentSeriesCoefficientAlgebra
noncomputable local instance
    equalCharacteristicCompletedFrobeniusFixedFieldGenerationLevelAlgebra
    (F : LocalField.{u, v} K) (n : ℕ) :
    Algebra F.residueField⸨X⸩
      (equalCharacteristicCompletedLevelField F n) :=
  RingHom.toAlgebra
    ((algebraMap (equalCharacteristicCompletedUnramifiedField F.residueField)
        (equalCharacteristicCompletedLevelField F n)).comp
      (algebraMap F.residueField⸨X⸩
        (equalCharacteristicCompletedUnramifiedField F.residueField)))
instance
    equalCharacteristicCompletedFrobeniusFixedFieldGenerationScalarTower
    (F : LocalField.{u, v} K) (n : ℕ) :
    IsScalarTower F.residueField⸨X⸩
      (equalCharacteristicCompletedUnramifiedField F.residueField)
      (equalCharacteristicCompletedLevelField F n)
LubinTate.EqualCharacteristic.equalCharacteristicCompletedFrobeniusFixedField_eq_adjoin_directTheta

The Frobenius fixed field is exactly the finite target Lubin--Tate level generated by theta(lambda) inside the completed field.

Source context 10 commands

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

noncomputable section
open scoped LaurentSeries Polynomial PowerSeries
universe u v
namespace LubinTate
namespace EqualCharacteristic
open LocalFieldTheory.DiscreteValuationField
variable {K : Type u} [Field K]
noncomputable local instance
    equalCharacteristicCompletedFrobeniusFixedFieldGenerationBaseAlgebra
    (F : LocalField.{u, v} K) :
    Algebra F.residueField⸨X⸩
      (equalCharacteristicCompletedUnramifiedField F.residueField) :=
  laurentSeriesCoefficientAlgebra
noncomputable local instance
    equalCharacteristicCompletedFrobeniusFixedFieldGenerationLevelAlgebra
    (F : LocalField.{u, v} K) (n : ℕ) :
    Algebra F.residueField⸨X⸩
      (equalCharacteristicCompletedLevelField F n) :=
  RingHom.toAlgebra
    ((algebraMap (equalCharacteristicCompletedUnramifiedField F.residueField)
        (equalCharacteristicCompletedLevelField F n)).comp
      (algebraMap F.residueField⸨X⸩
        (equalCharacteristicCompletedUnramifiedField F.residueField)))
local instance
    equalCharacteristicCompletedFrobeniusFixedFieldGenerationScalarTower
    (F : LocalField.{u, v} K) (n : ℕ) :
    IsScalarTower F.residueField⸨X⸩
      (equalCharacteristicCompletedUnramifiedField F.residueField)
      (equalCharacteristicCompletedLevelField F n) :=
  IsScalarTower.of_algebraMap_eq' rfl
theorem equalCharacteristicCompletedFrobeniusFixedField_eq_adjoin_directTheta
    (F : LocalField.{u, v} K)
    [CharP K F.residueCharacteristic]
    (a : F.residueField⟦X⟧ˣ) (n : ℕ) :
    equalCharacteristicCompletedFrobeniusFixedField F a n =
      IntermediateField.adjoin F.residueField⸨X⸩
        ({(equalCharacteristicDirectThetaAtCompletedPrimitiveRoot F a n :
          equalCharacteristicCompletedLevelField F n)} :
          Set (equalCharacteristicCompletedLevelField F n))