Sections on the blow-up are bounded by curve bounds
OpenOAI.MaximalSeshadri.Geometry.PointBlowup.section_curve_boundLet be a surface with ample , a configuration of points, a point blow-up of at with projection , and presenting the pullback of the centre ideal. Let with for all integral curves on . If and is a nonzero section of on , then .
Notation. is selfIntersection, namely . is curveDegree, namely . is totalMultiplicity, the sum over the points of curveMultiplicity, the order of the kernel ideal of the local ring map of at the point. PresentsPullbackIdeal I f J ι says that is a monomorphism whose image on affine opens is the extension of along . IsAmple means that for each point and open , some positive power has a global section with nonvanishing open containing , inside , and affine. A Surface is an integral scheme smooth of relative dimension 2 over with a closed immersion into some complex projective space over . An IntegralCurve on a surface is an integral closed subscheme of topological Krull dimension one, given by a closed immersion. Configuration S r is the set of -tuples of complex points with distinct images, with the Zariski topology induced from the product.
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.
import Mathlib import Definitions.Def_MaximalSeshadriConstants import Definitions.Def_SeshadriPrelim6 namespace OAI section namespace MaximalSeshadri.Geometry noncomputable section open AlgebraicGeometry CategoryTheory CategoryTheory.Limits TopologicalSpace open MaximalSeshadri.Frames MaximalSeshadri.ProjectiveBertini
theorem PointBlowup.section_curve_bound (S : Surface) (L : LineBundle S.scheme)
(hL : L.IsAmple) {r : ℕ} {p : Configuration S r} (B : PointBlowup S r p)
(J : LineBundle B.surface.scheme) (ι : J.sheaf ⟶ O B.surface.scheme)
(hJ : PresentsPullbackIdeal (centreIdeal S r p) B.projection J ι)
(w : ℝ) (hw : 0 ≤ w)
(hC : ∀ C : IntegralCurve S,
w*(totalMultiplicity S r C p:ℝ) ≤ (curveDegree S L C:ℝ))
(k m : ℕ)
(q : O B.surface.scheme ⟶ ((J.pow m).tensor ((L.pow k).pullback B.projection)).sheaf)
(hq : q ≠ 0) : w*((r*m:ℕ):ℝ) ≤ (k:ℝ)*selfIntersection S L := by
sorry
end
end MaximalSeshadri.Geometry
end
end OAI