Generalized twisted cubics on a cubic fourfold as a moduli space of stable objects

Abstract

We revisit the work of Lehn–Lehn–Sorger–van Straten on twisted cubic curves in a cubic fourfold not containing a plane in terms of moduli spaces. We show that the blow-up Z′ along the cubic of the irreducible holomorphic symplectic eightfold Z, described by the four authors, is isomorphic to an irreducible component of a moduli space of Gieseker stable torsion sheaves or rank three torsion free sheaves.For a very general such cubic fourfold, we show that Z is isomorphic to a connected component of a moduli space of tilt-stable objects in the derived category and to a moduli space of Bridgeland stable objects in the Kuznetsov component. Moreover, the contraction between Z′ and Z is realized as a wall-crossing in tilt-stability.Finally, Z is birational to an irreducible component of a moduli space of Gieseker stable aCM bundles of rank six.