Franchetta conjecture for families with motivic multiplicativity

Let XX and BB be smooth connected varieties, and let f:XBf:X\to B be a smooth projective morphism such that a very general fiber of ff admits motivic 00-multiplicativity. Assume that, for a very general point bBb\in B, the monodromy-invariant sub-Hodge structure H(Xb,Q)π1(B,b)H^*(X_b,\mathbb{Q})^{\pi_1(B,b)} consists of Hodge classes. Franchetta conjecture for motivically multiplicative families. For every integer N1N\geq 1 and every cycle class ΓCH(X/BN)\Gamma\in\operatorname{CH}^*(X_{/B}^N), the restriction ΓXbN\Gamma|_{X_b^N} vanishes for every closed point bBb\in B whenever it is homologically trivial for a very general point bBb\in B. This generalizes the Franchetta property known in the source for certain universal families and is proposed as a generalization of the hyper-Kähler case; its status is not resolved there.

Sources & referencesView supporting material

Primary source

Ze Xu, “Motivic multiplicativity of complete intersections”, arXiv:2511.01362 (2026).

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.