Algebraically hyperbolic groups

Abstract

We initiate the study of torsion-free algebraically hyperbolic groups; these groups generalise torsion-free hyperbolic groups and are intricately related to groups with no Baumslag–Solitar subgroups. Indeed, for groups of cohomological dimension $2$, we prove that algebraic hyperbolicity is equivalent to containing no Baumslag–Solitar subgroups. This links algebraically hyperbolic groups to two famous questions of Gromov; recent work has shown these questions to have negative answers in general, but they remain open for groups of cohomological dimension $2$. We also prove that algebraically hyperbolic groups are conjugacy separated abelian (CSA), and so have canonical abelian JSJ-decompositions. In the two-generated case, we give a precise description of the form of these decompositions.