Convergence of spherical averages for actions of Fuchsian Groups

Abstract

Pointwise convergence of spherical averages is proved for a measure-preserving action of a Fuchsian group. The proof is based on a new variant of the Bowen-Series symbolic coding for Fuchsian groups that, developing a method introduced by Wroten, simultaneously encodes all possible shortest paths representing a given group element. The resulting coding is self-inverse, giving a reversible Markov chain to which methods previously introduced by the first author for the case of free groups may be applied.

arXiv comment71 pages, 14 figures; a new proof for the result on the structure of thickened paths (see Sections 3 and 4), many minor improvements and clarifications