Context-free graphs and their transition groups (2408.13070v2)

Abstract: We define a new class of groups arising from context-free inverse graphs. We provide closure properties, prove that their co-word problems are context-free, study the torsion elements, and realize them as subgroups of the asynchronous rational group. Furthermore, we use a generalized version of the free product of graphs and prove that such a product is context-free inverse closed. We also exhibit an example of a group in our class that is not residually finite and one that is not poly-context-free. These properties make them interesting candidates to disprove both the Lehnert conjecture (which characterizes co-context-free groups as all subgroups of Thompson's group V) and the Brough conjecture (which characterizes finitely generated poly-context-free groups as virtual finitely generated subgroups of direct products of free groups).