A –structure on a group was introduced by Bestvina in order to extend the notion of a group boundary beyond the realm of CAT(0) and hyperbolic groups. A refinement of this notion, introduced by Farrell and Lafont, includes a –equivariance requirement, and is known as an –structure. The general questions of which groups admit – or –structures remain open. Here we show that all Baumslag–Solitar groups admit –structures and all generalized Baumslag–Solitar groups admit –structures.
"Boundaries of Baumslag–Solitar groups." Algebr. Geom. Topol. 19 (4) 2077 - 2097, 2019. https://doi.org/10.2140/agt.2019.19.2077