The rationality of certain moduli spaces of curves of genus 3

Abstract

We show, for each algebraically closed field, the rationality of the following two moduli spaces: M(3,3) parametrizing pairs (C, \eta) where C has genus 3 and \eta is a 3-torsion divisor class, respectively of M(3,<3>) parametrizing pairs (C, <\eta>) as above and where <\eta> is the cyclic subgroup of order 3 in Pic_0(C) generated by \eta.