Finite quotients of Fuchsian groups

Abstract

This work provides an effective algorithm for distinguishing finite quotients between two non-isomorphic finitely generated Fuchsian groups $\Gamma$ and $\Lambda$. It will suffice to take a finite quotient which is abelian, dihedral, a subgroup of $\mathrm{PSL}(2,\mathbf{F}_q)$, or an abelian extension of one of these 3. We will develop an approach for creating group extensions upon a shared finite quotient of $\Gamma$ and $\Lambda$ which between them have differing degrees of smoothness. Regarding the order of a finite quotient that distinguishes between $\Gamma$ and $\Lambda$, we establish an upperbound as a function of the genera, the number of punctures, and the cone orders arising in $\Gamma$ and $\Lambda$.