Module

InverseLimitModel.lean

Nyll.SchemeTheory.FiniteEtale.InverseLimitModel
1 declaration indexed from sourceView source ↗

Finite-etale objects descend along general qcqs inverse limits

Starting with the original finite-etale object over an actual inverse limit, construct a finite affine stage cover and recovered local models. Actual morphism descent and eventual gluing equations then give a global finite-etale model over an original stage, with literal native recovery.

Declarations

AlgebraicGeometry.FiniteEtale.exists_inverse_limit_model

Every finite-etale object over the actual inverse limit of qcqs schemes with affine transition maps descends to an original stage. The recovery isomorphism is along the literal native finite-etale pullback functor.

Source context 4 commands

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

noncomputable section
universe u
open CategoryTheory Limits
namespace AlgebraicGeometry.FiniteEtale
theorem exists_inverse_limit_model
    {I : Type u} [Category.{u} I] [IsCofiltered I]
    (D : I ⥤ Scheme.{u}) (c : Cone D) (hc : IsLimit c)
    [∀ {i j : I} (h : i ⟶ j), IsAffineHom (D.map h)]
    [∀ i : I, CompactSpace (D.obj i)] [∀ i : I, QuasiSeparatedSpace (D.obj i)]
    (X : FiniteEtale c.pt) :
    ∃ (i : I) (N : FiniteEtale (D.obj i)),
      Nonempty ((FiniteEtale.pullback (c.π.app i)).obj N ≅ X)