Module

ActualFiniteNormalizationRestriction.lean

Nyll.EtaleFundamentalGroups.Inertia.ActualFiniteNormalizationRestriction
2 declarations indexed from sourceView source ↗

Galois restriction on finite normalizations

Constructs the finite Galois action on its normalization and the homomorphism restricting ambient Galois automorphisms to those coefficient automorphisms.

Declarations

EtaleFundamentalGroups.Inertia.finiteNormalizationGaloisGroupMap

The actual finite Galois action on its literal native normalization.

Source context 5 commands

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

noncomputable section
namespace EtaleFundamentalGroups.Inertia
open SchemeTheory
universe u v w
variable (A : Type u) (K : Type v) (L : Type w)
  [CommRing A] [Field K] [Field L]
  [Algebra A K] [IsFractionRing A K]
  [Algebra K L] [Algebra A L] [IsScalarTower A K L] [IsGalois K L]
def finiteNormalizationGaloisGroupMap (E : FiniteGaloisIntermediateField K L) :
    GrpCat.Hom (finiteGaloisGroupObject K L E)
      (commAlgAutomorphismGroup A (finiteAbsoluteNormalizationAlgebra A K L E)) where
  hom' := (normalizationAutomorphismGroupMap A (finiteLevelFieldAlgebra A K L E)).hom'.comp
    (scalarRestrictionGroupMap A K (finiteLevelFieldAlgebra A K L E)).hom'
EtaleFundamentalGroups.Inertia.actualFiniteNormalizationRestriction

Actual ambient Galois restriction to the intrinsic automorphism group of the native finite normalization. Every map is constructed canonically.

Source context 5 commands

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

noncomputable section
namespace EtaleFundamentalGroups.Inertia
open SchemeTheory
universe u v w
variable (A : Type u) (K : Type v) (L : Type w)
  [CommRing A] [Field K] [Field L]
  [Algebra A K] [IsFractionRing A K]
  [Algebra K L] [Algebra A L] [IsScalarTower A K L] [IsGalois K L]
def actualFiniteNormalizationRestriction (E : FiniteGaloisIntermediateField K L) :
    GrpCat.Hom (galoisGroupObject K L)
      (commAlgAutomorphismGroup A (finiteAbsoluteNormalizationAlgebra A K L E)) where
  hom' := (finiteNormalizationGaloisGroupMap A K L E).hom'.comp
    (finiteGaloisRestrictionGroupMap K L E).hom'