Debarre's codimension conjecture for Andreotti–Mayer loci

For g1g\geq 1, let Nk,gN_{k,g} be the Andreotti–Mayer locus of principally polarized abelian varieties whose theta divisor has singular locus of dimension at least kk, let Agind{\mathcal A}_g^{\mathrm{ind}} denote the indecomposable locus, and let HypgHyp_g be the locus of hyperelliptic Jacobians. For an irreducible component XNk,gX\subset N_{k,g}, assume that for general (A,Θ)X(A,\Theta)\in X one has End(A,Θ)=Z\operatorname{End}(A,\Theta)={\mathbb Z}.

Debarre's codimension conjecture. For any 1kg31\leq k\leq g-3,

codimAgX(k+1)(k+2)2,\operatorname{codim}_{{\mathcal A}_g}X\geq\frac{(k+1)(k+2)}{2},

with equality only for components JgNg4,g{\mathcal J}_g\subset N_{g-4,g} and HypgNg3,gHyp_g\subset N_{g-3,g}. This conjecture concerns the expected size of Andreotti–Mayer loci and their role in solving the Schottky problem. The source gives no resolution status.

Sources & referencesView supporting material

Primary source

Samuel Grushevsky, “The Schottky Problem”, arXiv:1009.0369 (2010).

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