Quadratic differentials and circle patterns on complex projective tori

Abstract: Given a triangulation of a closed surface, we consider a cross ratio system that assigns a complex number to every edge satisfying certain polynomial equations per vertex. Every cross ratio system induces a complex projective structure together with a circle pattern on the closed surface. In particular, there is an associated conformal structure. We show that for any triangulated torus, the projection from the space of cross ratio systems with prescribed Delaunay angles to the Teichm\"{u}ller space is a covering map with at most one branch point. Our approach is based on a notion of discrete holomorphic quadratic differentials.