Module

RecoveredPullbackOverlaps.lean

Nyll.SchemeTheory.Gluing.RecoveredPullbackOverlaps
1 declaration indexed from sourceView source ↗

Actual overlaps of the recovered pullback charts

The canonical recovered transition identifies the two chart overlaps inside the original recovered scheme. The cartesian assertion follows from the already proved chart squares and transition projection equations.

Declarations

AlgebraicGeometry.Scheme.Cover.recoveredPullbackTransition_isPullback

The actual recovered raw overlap is the pullback of the two recovered chart maps into the original scheme, for an arbitrary base change.

Source context 4 commands

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

noncomputable section
universe u
open CategoryTheory Limits
namespace AlgebraicGeometry.Scheme.Cover
theorem recoveredPullbackTransition_isPullback
    {S L : Scheme.{u}} (ψ : L ⟶ S) (𝒰 : S.OpenCover.{u})
    (M : ∀ i : 𝒰.I₀, Over (𝒰.X i)) (Z : Over L)
    (e : ∀ i : 𝒰.I₀,
      (Over.pullback (pullback.fst (𝒰.f i) ψ)).obj (M i) ≅
        (Over.pullback (pullback.snd (𝒰.f i) ψ)).obj Z)
    (i j : 𝒰.I₀) :
    IsPullback ((Over.pullback ψ).map (gluingOverlapFirst 𝒰 M i j)).left
      (recoveredPullbackTransition ψ 𝒰 M Z e i j ≫
        (Over.pullback ψ).map (gluingOverlapFirst 𝒰 M j i)).left
      (recoveredPullbackChartMap ψ 𝒰 M Z e i)
      (recoveredPullbackChartMap ψ 𝒰 M Z e j)