Some ergodic properties of metrics on hyperbolic groups

Abstract

Let $\Gamma$ be a non-elementary Gromov-hyperbolic group, and $\partial \Gamma$ denote its Gromov boundary. We consider $\Gamma$-invariant proper $\delta$-hyperbolic, quasi-convex metric $d$ on $\Gamma$, and the associated Patterson-Sullivan measure class $[\nu]$ on $\partial^{(2)}\Gamma$, and its square $[\nu\times\nu]$ on $\partial^{(2)}\Gamma$ -- the space of distinct pairs of points on the boundary. We construct an analogue of a geodesic flow to study ergodicity properties of the $\Gamma$-actions on $(\partial\Gamma,\nu)$ and on $(\partial^{(2)}\Gamma,[\nu\times\nu])$. We also prove some ergodic theorems for $\Gamma$-actions guided by the geometry of $(\Gamma,d)$.