An example of a non-amenable dynamical system which is boundary amenable

Abstract

It is shown that the action of ${\rm SL}(3,\mathbb{Z})$ on the Stone-\u{C}ech boundary of ${\rm SL}(3,\mathbb{Z}) / {\rm SL}(2,\mathbb{Z}) $ is amenable. This confirms a prediction by Bekka and Kalantar.