Debarre's codimension conjecture for Andreotti–Mayer loci

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For g≥1g\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 X⊂Nk,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 1≤k≤g−31\leq k\leq g-3,

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

with equality only for components Jg⊂Ng−4,g{\mathcal J}_g\subset N_{g-4,g} and Hypg⊂Ng−3,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.

References

Primary source

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

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