Conjecture on divisors parameterized by stable objects on singular cubic surfaces

Let YY be a smooth cubic threefold, let SS be a singular hyperplane section, and let DD be a Weil divisor on SS such that OS(D)\mathcal{O}_S(D) is a stable object parameterized by Mσ(w)\mathcal{M}_{\sigma}(w). Suppose the off-diagonal part of H(Y)~\widetilde{H(Y)} parameterizes type (I) and (III) schemes with an order, whose supports are intended to determine DD. Divisor-support conjecture. The divisor DD has the form L1L2L_1-L_2, where L1,L2L_1,L_2 are two lines on SS, possibly singular, and one of the following holds: (i) L1L_1 and L2L_2 are disjoint, though the lines may pass through singularities; or (ii) L1L_1 and L2L_2 intersect at one point pp, which is a singularity of SS. The explicit expression of DD on singular hyperplane sections is not otherwise known, so this conjecture would identify the divisors arising from the stable moduli space.

Sources & referencesView supporting material

Primary source

Yilong Zhang, “Hilbert Scheme of a Pair of Skew Lines on Cubic Threefolds”, arXiv:2010.11622 (2025).

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