Module

subsingleton_H1_fibre_of_subsingleton_H1_fibre_extension.lean

Nyll.JacobianVarieties.Picard.subsingleton_H1_fibre_of_subsingleton_H1_fibre_extension
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Descent of vanishing first fibre cohomology

Vanishing of first cohomology after a field extension implies vanishing over the original field, using the comparison of two-affine-cover cohomology.

Declarations

AlgebraicGeometry.RelPicard.subsingleton_H1_fibre_of_subsingleton_H1_fibre_extension
Source context 5 commands

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

section ProofImplementation
namespace AlgebraicGeometry.RelPicard
attribute [-simp] AlgebraicGeometry.tilde.functorCompPullbackSpecIso_app
universe u
open CategoryTheory CategoryTheory.Limits AlgebraicGeometry NeronModelInfra
theorem subsingleton_H1_fibre_of_subsingleton_H1_fibre_extension
    {R : Type u} [CommRing R] {C : Scheme.{u}} (c : C ⟶ Spec (CommRingCat.of R)) [IsSeparated c]
    {T : Scheme.{u}} (t : T ⟶ Spec (CommRingCat.of R)) (M : (pullback c t).Modules)
    (hM : Scheme.Modules.IsInvertible M)
    {k : Type u} [Field k] (s : Spec (CommRingCat.of k) ⟶ T)
    (K : Type u) [Field K] [Algebra k K]
    (hK : ∀ 𝒲' :
      (pullback (pullback.snd c t) (Scheme.TwoAffineOpenCover.specMap k K ≫ s)).TwoAffineOpenCover,
      Subsingleton (𝒲'.sectionsOf (fibreAt c t (Scheme.TwoAffineOpenCover.specMap k K ≫ s))
        (fibreModule c t (Scheme.TwoAffineOpenCover.specMap k K ≫ s) M)).H1) :
    ∀ 𝒲 : (pullback (pullback.snd c t) s).TwoAffineOpenCover,
      Subsingleton (𝒲.sectionsOf (fibreAt c t s) (fibreModule c t s M)).H1