Derived Torelli for Kuznetsov components of cubic fourfolds

Abstract

We prove that every orientation-preserving Hodge isometry between the integral Mukai lattices of the Kuznetsov components of two smooth cubic fourfolds is induced by an exact equivalence. The proof uses Markman--Mehrotra's comonad reconstruction method to recover both Kuznetsov components from a common Fourier--Mukai comonad on a moduli space of stable objects. As an application, we prove that the Kuznetsov components of two smooth cubic fourfolds are equivalent whenever their Fano varieties of lines are derived equivalent.