Symmetries of Riemann surfaces on which PSL(2,q) acts as a Hurwitz automorphism group

Abstract

Let X be a compact Riemann surface and Aut(X) be its automorphism group. An automorphism of order 2 reversing the orientation is called a symmetry. The authors together with D. Singerman have been working on symmetries of Riemann surfaces in the last decade. In this paper, the symmetry type St(X) of X is defined as an unordered list of species of conjugacy classes of symmetries of X, and for a class of particular surfaces, St(X) is found. This class consists of Riemann surfaces on which PSL(2, q) acts as a Hurwitz group. An algorithm to calculate the symmetry type of this class is provided.