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LeanPool.BrillNoetherGraphs.Utilities.Subdivision.CoreVertexCutRankOne

Rank one across a checked genus-three/genus-one core cut #

A two-regular genus-one side of a valid core articulation is a pointed rigid cycle after every positive subdivision. The public genus-three rigid-wedge theorem then supplies a degree-three rank-one divisor on the ambient graph.

theorem Utilities.Certificate.CoreVertexCut.Data.bnExists_one_three_of_left_three_right_rigid {n p : ℕ} {spec : SubdivisionGraph.Spec n p} (cutData : Data spec.core) (hLeftGenus : cutData.leftGenus = 3) (hRightRigid : cutData.RightRigidConditions) :
BNExists spec.graph 1 3

A genus-three named side and rigid complementary genus-one side give a degree-three pencil on every positive subdivision.