Algebraically hyperbolic groups

TL;DR

This paper introduces the concept of algebraically hyperbolic groups, explores their properties, and establishes their relation to Baumslag--Solitar subgroups and JSJ-decompositions, especially in groups of cohomological dimension 2.

Contribution

It defines algebraically hyperbolic groups, proves their equivalence to groups with no Baumslag--Solitar subgroups in dimension 2, and describes their JSJ-decompositions.

Findings

Algebraically hyperbolic groups are CSA.

In dimension 2, they contain no Baumslag--Solitar subgroups.

Two-generated algebraically hyperbolic groups have explicit JSJ-decomposition forms.

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 CSA, and so have canonical abelian JSJ-decompositions. In the two-generated case we give a precise description of the form of these decompositions.