Conjecture on divisors parameterized by stable objects on singular cubic surfaces

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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 L1−L2L_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.

References

Primary source

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

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