Invariant Radon measures for Unipotent flows and products of Kleinian groups

Abstract

Let G=PSL(2, F) where F= R or C, and consider the space Z=(Γ_1 x Γ_2)\ (G x G) where Γ_1<G is a co-compact lattice and Γ_2<G is a finitely generated discrete Zariski dense subgroup. The work of Benoist-Quint gives a classification of all ergodic invariant Radon measures on Z for the diagonal G-action. In this paper, for a horospherical subgroup N of G, we classify all ergodic, conservative, invariant Radon measures on Z for the diagonal N-action, under the additional assumption that Γ_2 is geometrically finite.

12 pages