The Beauville-Voisin-Franchetta conjecture and LLSS eightfolds

Abstract

The Chow rings of hyper-K\"ahler varieties are conjectured to have a particularly rich structure. In this paper, we formulate a conjecture that combines the Beauville-Voisin conjecture regarding the subring generated by divisors and the Franchetta conjecture regarding generically defined cycles. As motivation, we show that this Beauville-Voisin-Franchetta conjecture for a hyper-K\"ahler variety $X$ follows from a combination of Grothendieck's standard conjectures for a very general deformation of $X$, Murre's conjecture (D) for $X$ and the Franchetta conjecture for $X^3$. As evidence, beyond the case of Fano varieties of lines on smooth cubic fourfolds, we show that this conjecture holds for codimension-2 and codimension-8 cycles on Lehn-Lehn-Sorger-van Straten eightfolds. Moreover, we establish that the subring of the Chow ring generated by primitive divisors injects into cohomology.