Module

InverseLimitFaithfulness.lean

Nyll.EtaleFundamentalGroups.FiniteEtale.InverseLimitFaithfulness
2 declarations indexed from sourceView source ↗

Faithfulness of the finite etale model localization

Geometric equality descent for the original inverse limit supplies eventual equality at an actual stage. The categorical fraction argument then makes the comparison from the cartesian model localization faithful.

Declarations

AlgebraicGeometry.FiniteEtale.InverseLimitModel.exists_refinement_map_eq

Two actual model arrows which agree at the limit agree after a cartesian refinement of their original source.

Source context 9 commands

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

noncomputable section
open CategoryTheory CategoryTheory.Limits Opposite
namespace AlgebraicGeometry.FiniteEtale.InverseLimitModel
universe u
variable {I : Type u} [Preorder I] [IsDirectedOrder I] [Nonempty I]
variable (F : Iᵒᵖ ⥤ Scheme.{u}) (s : Cone F) (hs : IsLimit s)
variable [∀ {i j : Iᵒᵖ} (h : i ⟶ j), IsAffineHom (F.map h)]
variable [∀ i : Iᵒᵖ, CompactSpace (F.obj i)]
include hs
theorem exists_refinement_map_eq
    {A B : InverseLimitModel F} (f g : A ⟶ B)
    (hfg : (baseChange F s).map f = (baseChange F s).map g) :
    ∃ (j : Iᵒᵖ) (h : j ⟶ A.right),
      refinementHom F A h ≫ f = refinementHom F A h ≫ g
AlgebraicGeometry.FiniteEtale.InverseLimitModel.localizedBaseChange_faithful

The actual comparison from the model localization is faithful, by geometric eventual equality and the concrete fraction criterion.

Source context 9 commands

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

noncomputable section
open CategoryTheory CategoryTheory.Limits Opposite
namespace AlgebraicGeometry.FiniteEtale.InverseLimitModel
universe u
variable {I : Type u} [Preorder I] [IsDirectedOrder I] [Nonempty I]
variable (F : Iᵒᵖ ⥤ Scheme.{u}) (s : Cone F) (hs : IsLimit s)
variable [∀ {i j : Iᵒᵖ} (h : i ⟶ j), IsAffineHom (F.map h)]
variable [∀ i : Iᵒᵖ, CompactSpace (F.obj i)]
include hs
theorem localizedBaseChange_faithful : (localizedBaseChange F s).Faithful