Module

ContinuousHomComparison.lean

Nyll.EtaleFundamentalGroups.GaloisCategories.ContinuousHomComparison
2 declarations indexed from sourceView source ↗

Recovering continuous homomorphisms from induced functors

The chosen inverse to the finite continuous-action equivalence supplies a canonical comparison isomorphism for the functor induced by a continuous homomorphism. The equivariance of the chosen counit shows that the resulting homomorphism on automorphism groups is the original one.

Declarations

CategoryTheory.PreGaloisCategory.comparisonIsoOfContinuousHom

The canonical comparison between the composite fiber functor of the functor induced by h and the original fiber functor.

Source context 10 commands

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

@[expose] public section
universe u₁ u₂ v₁ v₂ w
noncomputable section
open CategoryTheory
open scoped FintypeCatDiscrete
namespace CategoryTheory.PreGaloisCategory
variable {C : Type u₁} [Category.{u₂} C] [GaloisCategory C]
variable {C' : Type v₁} [Category.{v₂} C'] [GaloisCategory C']
variable (F : C ⥤ FintypeCat.{w}) [FiberFunctor F]
variable (F' : C' ⥤ FintypeCat.{w}) [FiberFunctor F']
def comparisonIsoOfContinuousHom
    (h : Aut F' →ₜ* Aut F) :
    functorOfContinuousHom F F' h ⋙ F' ≅ F
CategoryTheory.PreGaloisCategory.autHomOfCompIso_comparisonIsoOfContinuousHom

The canonical comparison isomorphism recovers the continuous homomorphism from which the functor was constructed.

Source context 11 commands

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

@[expose] public section
universe u₁ u₂ v₁ v₂ w
noncomputable section
open CategoryTheory
open scoped FintypeCatDiscrete
namespace CategoryTheory.PreGaloisCategory
variable {C : Type u₁} [Category.{u₂} C] [GaloisCategory C]
variable {C' : Type v₁} [Category.{v₂} C'] [GaloisCategory C']
variable (F : C ⥤ FintypeCat.{w}) [FiberFunctor F]
variable (F' : C' ⥤ FintypeCat.{w}) [FiberFunctor F']
omit [GaloisCategory C] [FiberFunctor F] in
theorem autHomOfCompIso_comparisonIsoOfContinuousHom
    (h : Aut F' →ₜ* Aut F) :
    autHomOfCompIso (functorOfContinuousHom F F' h)
        (comparisonIsoOfContinuousHom F F' h) =
      h