The generalized Franchetta conjecture for some hyper-Kähler varieties

Lie Fu (1) , Robert Laterveer (2) , Charles Vial (3) , Mingmin Shen

1 ICJ - Institut Camille Jordan
2 IRMA - Institut de Recherche Mathématique Avancée
3 SFB 705 - Fakultät für Mathematik [Bielefeld]

We study the generalized Franchetta conjecture for holomorphic symplectic varieties. The conjecture predicts that the restriction of an algebraic cycle on the universal family of certain polarized hyper-Kähler varieties to a fiber is rationally equivalent to zero if and only if its cohomology class vanishes. We provide the following evidences : (1) The Beauville–Donagi family of Fano varieties of lines on cubic fourfolds ; (2) The relative square, relative cube, relative Hilbert square and relative Hilbert cube of the universal families of K3 surfaces which are complete intersections in (weighted) projective spaces ; (3) The relative product of the relative r 1 , · · · , r m-th Hilbert powers of the universal family of quartic K3 surfaces, where r 1 +.. .+r m ≤ 5 ; (4) The relative square and relative Hilbert square of the universal families of K3 surfaces of genera 6, 7, 8, 9, 10 and 12 ; (5) Relative square of the universal Fano variety of lines of the universal family of cubic fourfolds ; (6) Zero-cycles and codimension 2 cycles for the Lehn–Lehn–Sorger–van Straten family of hyper-Kähler eightfolds. We also draw many consequences in the direction of the Beauville–Voisin conjecture as well as Voisin's refinement for coisotropic subvarieties. In the appendix, we establish a new relation among tautological cycles on the square of the Fano variety of lines of a smooth cubic fourfold and provide some applications.

Domaines: Géométrie algébrique [math.AG]

Lie Fu, Robert Laterveer, Charles Vial, Mingmin Shen. The generalized Franchetta conjecture for some hyper-Kähler varieties. Journal de Mathématiques Pures et Appliquées, 2019, ⟨10.1016/j.matpur.2019.01.018⟩. ⟨hal-01653196v2⟩