An affine cover by twisted sections
OpenOAI.MaximalSeshadri.Geometry.LineBundle.twist_affine_covermaximal-seshadrioai-math
Let be integral and compact, line bundles, sections of with iso-opens covering , and assume has affine covers by sections over each iso-open of . Then there are and a finite family of sections of whose iso-opens cover , are affine and are nonempty.
Notation. The iso-open of (SectionOpens.isoOpen s) is the union of the opens on which the morphism restricts to an isomorphism.
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.Geometry
noncomputable section
open CategoryTheory CategoryTheory.Limits AlgebraicGeometry TopologicalSpace
open MaximalSeshadri.Frames MaximalSeshadri.SectionOpens MaximalSeshadri.Projective
variable {X : Scheme.{0}}
Formal statement
theorem LineBundle.twist_affine_cover [IsIntegral X] [CompactSpace X]
(P J : LineBundle X) {κ : Type} (t : κ → (O X ⟶ P.sheaf))
(ht : (⨆ i,isoOpen (t i)) = ⊤)
(hlocal : ∀ i, ∃ (α : Type)
(w : α → (O (isoOpen (t i)).toScheme ⟶ J.sheaf.restrict (isoOpen (t i)).ι)),
(⨆ a,isoOpen (w a)) = ⊤ ∧ ∀ a, IsAffineOpen (isoOpen (w a))) :
∃ n : ℕ, 0 < n ∧ ∃ (σ : Type) (_ : Fintype σ)
(s : σ → (O X ⟶ ((P.pow n).tensor J).sheaf)),
(⨆ a,isoOpen (s a)) = ⊤ ∧
(∀ a, IsAffineOpen (isoOpen (s a))) ∧
(∀ a, (isoOpen (s a) : Set X).Nonempty) := by
sorry
end
end MaximalSeshadri.Geometry
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.Geometry.LineBundle.twist_affine_cover`, https://github.com/openai/math/blob/adc7f1241b42e322a6451854ab7e4b4c146bf78a/lean/OAI/AlgebraicGeometry/Seshadri/Geometry/RelativeProjectivity.lean#L22