The degenerate singular-locus conjecture for Verra threefolds

Let (J(T),Ξ)(J(T),\Xi) be the intermediate Jacobian of a general Verra threefold TT, let Ξ\Xi be its theta divisor, and let ee be the canonical extension class; write Ξe\Xi_e for the corresponding translate. Degenerate singular-locus conjecture. The singular locus of the intersection ΞΞe\Xi\cdot\Xi_e has dimension 44 and has a unique component of that dimension. This component is a translate of

S1odd+S2odd.S_1^{\rm odd}+S_2^{\rm odd}.

This is the nodal degeneration of the preceding conjecture: the two period-map fiber components degenerate to the special surfaces S1oddS_1^{\rm odd} and S2oddS_2^{\rm odd}. The source gives no resolution of this degenerate version.

Sources & referencesView supporting material

Primary source

Olivier Debarre, Atanas Iliev and Laurent Manivel, “On nodal prime Fano threefolds of degree 10”, arXiv:1004.4724 (2010).

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