Motivic invariants of moduli spaces of rank 2 Bradlow-Higgs triples

Abstract

In the present thesis we study the geometry of the moduli spaces of Bradlow-Higgs triples on a smooth projective curve C. There is a family of stability conditions for triples that depends on a positive real parameter Iƒ. The moduli spaces of Iƒ-semistable triples of rank r and degree d vary with Iƒ. The phenomenon arising Iƒ from this is known as wall-crossing. In the first half of the thesis we will examine how the moduli spaces and their universal additive invariants change as Iƒ varies, for the case r = 2. In particular we will study the case of Iƒ very close to 0, for which the moduli space relates to the moduli space of stable Higgs bundles, and Iƒ very large, for which the moduli space is a relative Hilbert scheme of points for the family of spectral curves. Some of these results will be generalized to Bradlow-Higgs triples with poles. In the second half we will prove a formula relating the cohomology of the moduli spaces for small and odd degree and the perverse filtration on the cohomology of the moduli space of stable Higgs bundles. We will also partially generalize this result to the case of rank greater than 2.