Intersection-lattice conjecture for the defect of line arrangements

For a reduced plane curve C={f=0}C=\{f=0\} in PC2\mathbb{P}^{2}_{\mathbb{C}}, let ν(C)\nu(C) denote its defect. A line arrangement is a union of finitely many lines in PC2\mathbb{P}^{2}_{\mathbb{C}}, and its intersection lattice records the intersections among its lines and the corresponding incidence relations. Intersection-lattice conjecture. For a line arrangement LPC2\mathcal{L} \subset \mathbb{P}^{2}_{\mathbb{C}}, the defect ν(L)\nu(\mathcal{L}) is determined by the intersection lattice of L\mathcal{L}; more precisely, if L1\mathcal{L}_{1} and L2\mathcal{L}_{2} are two line arrangements with isomorphic intersection lattices, then

ν(L1)=ν(L2).\nu(\mathcal{L}_{1})=\nu(\mathcal{L}_{2}).

This is presented as a difficult open problem and as a broad generalization of Terao's freeness conjecture for line arrangements.

Sources & referencesView supporting material

Primary source

Piotr Pokora, “Defect of irreducible plane curves with simple singularities”, arXiv:2404.03341 (2024).

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