Conjecture on smooth and oversized Hodge loci for cubic hypersurfaces

Let X0X_0 be a cubic hypersurface in the full family of cubic hypersurfaces, and let Pn2\mathbb{P}^{\frac{n}{2}} and Pˇn2\check{\mathbb{P}}^{\frac{n}{2}} be linear cycles in X0X_0. For a Hodge locus VγV_\gamma, write V[Pn2][Pˇn2]V_{[\mathbb{P}^{\frac{n}{2}}]-[\check{\mathbb{P}}^{\frac{n}{2}}]} and Vr[Pn2]rˇ[Pˇn2]V_{r[\mathbb{P}^{\frac{n}{2}}]-\check r[\check{\mathbb{P}}^{\frac{n}{2}}]} for the loci associated with the indicated cohomology classes. Smooth and oversized Hodge-locus conjecture. For the full family of cubic hypersurfaces, the following hold: (1) if Pn2Pˇn2=Pn22\mathbb{P}^{\frac{n}{2}}\cap\check{\mathbb{P}}^{\frac{n}{2}}=\mathbb{P}^{\frac{n}{2}-2}, then V[Pn2][Pˇn2]V_{[\mathbb{P}^{\frac{n}{2}}]-[\check{\mathbb{P}}^{\frac{n}{2}}]} is smooth and larger than the deformation space of the triple (X0,Pn2,Pˇn2)(X_0,\mathbb{P}^{\frac{n}{2}},\check{\mathbb{P}}^{\frac{n}{2}}); (2) if Pn2Pˇn2=Pn23\mathbb{P}^{\frac{n}{2}}\cap\check{\mathbb{P}}^{\frac{n}{2}}=\mathbb{P}^{\frac{n}{2}-3} and r,rˇN|r|,|\check r|\in\mathbb{N}, then Vr[Pn2]rˇ[Pˇn2]V_{r[\mathbb{P}^{\frac{n}{2}}]-\check r[\check{\mathbb{P}}^{\frac{n}{2}}]} is smooth and larger than the deformation space of the same triple, with dimension difference 11. The conjecture concerns excess-dimensional Hodge loci in the full cubic family; the supplied status evidence says that the integral and rational Hodge conjecture are proved in this case, so this candidate is recorded as solved.

Sources & referencesView supporting material

Primary source

Hossein Movasati, “Hodge cycles for cubic hypersurfaces”, arXiv:1902.00831 (2019).

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.