On dense free subgroups of Lie groups

Abstract

We give a method for constructing dense and free subgroups in real Lie groups. In particular we show that any dense subgroup of a connected semisimple real Lie group G contains a free group on two generators which is still dense in G , and that any finitely generated dense subgroup in a connected non-solvable Lie group H contains a dense free subgroup of rank ⩽2·dim H . This answers a question of Carriere and Ghys, and it gives an elementary proof to a conjecture of Connes and Sullivan on amenable actions, which was first proved by Zimmer.