Coarse equivalence and topological couplings of locally compact groups

Abstract

A result due to M. Gromov states that any two finitely generated groups Γ and Λ are quasi-isometric if and only if they admit a topological coupling, i.e., a commuting pair of proper continuous cocompact actions $Γ\curvearrowright X\curvearrowleft Λ$ on a locally compact Hausdorff space. This result is extended here to all (compactly generated) locally compact second countable groups.