A Lower Bound for the Number of Group Actions on a Compact Riemann Surface

Abstract

We prove that the number of distinct group actions on compact Riemann surfaces of a fixed genus $\sigma \geq 2$ is at least quadratic in $\sigma$. We do this through the introduction of a coarse signature space, the space $\mathcal{K}_\sigma$ of {\em skeletal signatures} of group actions on compact Riemann surfaces of genus $\sigma$. We discuss the basic properties of $\mathcal{K}_\sigma$ and present a full conjectural description.