Bergman kernel on Riemann surfaces and Kaehler metric on symmetric products

Abstract

Let $X$ be a compact hyperbolic Riemann surface equipped with the Poincar\'e metric. For any integer $k\geq 2$, we investigate the Bergman kernel associated to the holomorphic Hermitian line bundle $\Omega^{\otimes k}_X$, where $\O$ is the holomorphic cotangent bundle of $X$. Our first main result estimates the corresponding Bergman metric on $X$ in terms of the Poincar\'e metric. We then consider a certain natural embedding of the symmetric product of $X$ into a Grassmannian parametrizing subspaces of fixed dimension of the space of all global holomorphic sections of $\Omega^{\otimes k}_X$. The Fubini-Study metric on the Grassmannian restricts to a K\"ahler metric on the symmetric product of $X$. The volume form for this restricted metric on the symmetric product is estimated in terms of the Bergman kernel of $\Omega^{\otimes k}_X$ and the volume form for the orbifold K\"ahler form on the symmetric product given by the Poincar\'e metric on $X$.