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Finiteness of the toric H^1 quotient for a plane cover

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OAI.MaximalSeshadri.Projective.finite_plane_H1

by wurtle · Nov 4, 2026 · Mathlib 0df444a (Lean v4.33.1)

maximal-seshadrioai-math

Let KKK be a field, k:K→Γ(X,⊤)k:K\to\Gamma(X,\top)k:K→Γ(X,⊤), and s=(s0,s1,s2)s=(s_0,s_1,s_2)s=(s0​,s1​,s2​) sections of a module MMM with iso-opens covering XXX such that sectionsMorphism k s hs to the plane is finite. For a line bundle LLL, the quotient of cycles by vertexBoundaries of the edge submodules planePair and vertex submodules planeVertex inside the sections over the triple overlap is finite-dimensional over KKK.

Notation. The iso-open of sss (SectionOpens.isoOpen s) is the union of the opens on which the morphism sss restricts to an isomorphism. sectionsMorphism k s hs is the morphism from XXX to Proj⁡\operatorname{Proj}Proj of the graded polynomial ring in variables indexed by the sections, defined by sections whose iso-opens cover XXX, with kkk the ring map from the base into Γ(X,⊤)\Gamma(X,\top)Γ(X,⊤). cycles A B C is the submodule of A×B×CA\times B\times CA×B×C of triples with zero sum. planeVertex and planePair are the images in the sections over the triple overlap (planeTriple) of sections over the chart of sis_isi​, and over the overlap of the charts of si,sjs_i,s_jsi​,sj​, respectively.

Formalization Note The statement is verbatim from OpenAI's Lean development, with Definitions files of this development imported in place of the upstream modules; these are supporting code for the statement.

Preamble
import Mathlib
import Definitions.Def_MaximalSeshadriConstants
import Definitions.Def_SeshadriPrelim6

namespace OAI

section

namespace MaximalSeshadri.Projective
noncomputable section
open AlgebraicGeometry CategoryTheory TopologicalSpace
open MaximalSeshadri.Geometry MaximalSeshadri.Geometry.BaseSections MaximalSeshadri.Frames
open MaximalSeshadri.LaurentPlane MaximalSeshadri.PlaneCech

variable {K : Type} [Field K] {X : Scheme.{0}} {M : X.Modules}

Formal statement
theorem finite_plane_H1 (k : K →+* Γ(X,⊤))
    (s : Fin 3 → (O X ⟶ M)) (hs : (⨆ i, SectionOpens.isoOpen (s i)) = ⊤)
    [IsFinite (sectionsMorphism k s hs)] (L : LineBundle X) :
    Module.Finite K ((cycles (planePair k s L 0 1) (planePair k s L 0 2) (planePair k s L 1 2)) ⧸
      vertexBoundaries (planePair k s L 0 1) (planePair k s L 0 2) (planePair k s L 1 2)
        (planeVertex k s L)) := by
  sorry

end
end MaximalSeshadri.Projective
end
end OAI
Source
OpenAI, Maximal Seshadri constants on arbitrary polarized surfaces, September 23, 2026, https://github.com/openai/math (paper: preprints/Maximal-Seshadri-Constants-on-Arbitrary-Polarized-Surfaces-September-23-2026/main.pdf; Lean: lean/OAI/AlgebraicGeometry/Seshadri, Apache License 2.0); Lean declaration `OAI.MaximalSeshadri.Projective.finite_plane_H1`, https://github.com/openai/math/blob/adc7f1241b42e322a6451854ab7e4b4c146bf78a/lean/OAI/AlgebraicGeometry/Seshadri/Cohomology/PlaneH1Finite.lean#L21

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