Localizing the two-open section pullback #
Fixed-base sections of a module sheaf on a union are a pullback of the sections on its two opens. Canonical module localization is exact, so the localized cone is still a pullback. This is only a statement about localized sections of the source sheaf on these two opens and their union: identifying them with sections on a geometric base change requires separate affine-chart comparisons. No objectwise-localized sheaf is constructed here.
noncomputable def
AlgebraicGeometry.localizedFixedBaseSectionsTwoOpenLimit
{R : CommRingCat}
(Y : Scheme)
(φ : R ⟶ Y.presheaf.obj (Opposite.op ⊤))
(M : Y.Modules)
(U V : Y.Opens)
(S : Submonoid ↑R)
:
The two-open pullback cone remains a limit after localizing its four
section modules at S.
Equations
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