Correspondences on Riemann surfaces and non-uniform hyperbolicity

Laurent Bartholdi, Dzmitry Dudko, Kevin M. Pilgrim

Published 2024-07-22Version 1

We consider certain analytic correspondences on a Riemann surface, and show that they admit a weak form of expansion. In terms of their algebraic encoding by bisets, this translates to contraction of group elements along sequences arising from iterated lifting. As an application, we show that for every non-exceptional rational map on $\mathbb{P}^1$ with $4$ post-critical points, there is a finite collection of isotopy classes of curves into which every curve eventually lands under iterated lifting.