Folk conjecture on triple points of theta divisors

Let Ag{\mathcal A}_g be the moduli space of principally polarized abelian varieties. Let T3(g)T_3^{(g)} denote the locus of triples (A,Θ,x)(A,\Theta,x) where the theta divisor has multiplicity at least three at xx, let F3,0(g)=π(T3(g))F_{3,0}^{(g)}=\pi(T_3^{(g)}), and let Xgdec{\mathcal X}_g^{\rm dec} denote the decomposable locus in the universal principally polarized abelian variety. Write g+32\lfloor\frac{g+3}{2}\rfloor for the floor of (g+3)/2(g+3)/2.

Folk conjecture on triple points.

Tg+32(g)Xgdec.T^{(g)}_{\left\lfloor\frac{g+3}{2}\right\rfloor}\subset{\mathcal X}_g^{dec}.

The conjecture asserts that theta divisors with multiplicity at least (g+3)/2\left\lfloor(g+3)/2\right\rfloor occur only over decomposable ppav. It is motivated by the observation that indecomposable ppav have maximal possible theta-divisor multiplicity at most (g+1)/2(g+1)/2. The source gives no resolution status.

Sources & referencesView supporting material

Primary source

Samuel Grushevsky and Klaus Hulek, “Geometry of theta divisors — a survey”, arXiv:1204.2734 (2013).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.