Equivariant functions for the M\"{o}bius subgroups and applications

The aim of this paper is to give a generalization of the theory equivariant functions, initiated in [17, 4], to arbitrary subgroups of PSL2®. We show that there is a deep relation between the geometry of these groups and some analytic and algebraic properties of these functions. As an application, we give a new proof of the classification of automorphic forms for non discrete groups. Also, we prove the following automorphy condition: If $f$ is an automorphic form for a Fuchsian group of the first kind $\mathrm{\Gamma }$, then $f$ has infinitely many non $\mathrm{\Gamma }$-equivalent critical points.