Lattices in Baumslag-Solitar complexes

Baumslag-Solitar complexes are combinatorial models for the Baumslag-Solitar groups BS(m,n). This talk is about groups that act freely and cocompactly on these complexes. In some cases there exist incommensurable groups of this kind acting on the same complex, and in other cases an analogue of Leighton's graph covering theorem holds. I will discuss results by myself and by Maya Verma in this area.