Relative Jacobians of Linear Systems

Abstract

Let X be a smooth projective variety. Given any basepoint-free linear system, |D|, there is a dense open subset parametrizing smooth divisors, and over that subset, we can consider the relative Picard variety of the universal divisor, which parametrizes pairs of a smooth divisor in the linear system and a line bundle on that divisor. In the case where X is a surface, there is a natural compactification of the relative Picard variety, given by taking the moduli space of pure one-dimensional Gieseker-semistable sheaves with respect to some polarization. In the case of the projective plane, this is an irreducible projective variety of Picard number 2. We study the nef and effective cones of these moduli spaces, and talk about the relation with variation of Bridgeland stability conditions.