Coupled vortex equations and moduli: deformation theoretic approach and Kahler geometry

We investigate differential geometric aspects of moduli spaces parametrizing solutions of coupled vortex equations over a compact Kahler manifold X. These solutions are known to be related to polystable triples via a Kobayashi-Hitchin type correspondence. Using a characterization of infinitesimal deformations in terms of the cohomology of a certain elliptic double complex, we construct a Hermitian structure on these moduli spaces. This Hermitian structure is proved to be Kahler. The proof involves establishing a fiber integral formula for the Hermitian form. We compute the curvature tensor of this Kahler form. When X is a Riemann surface, the holomorphic bisectional curvature turns out to be semi-positive. It is shown that in the case where X is a smooth complex projective variety, the Kahler form is the Chern form of a Quillen metric on a certain determinant line bundle.