Splitting groups with cubic Cayley graphs of connectivity two

Abstract

A group $G$ splits over a subgroup $C$ if $G$ is either a free product with amalgamation $A \underset{C}{\ast} B$ or an HNN-extension $G=A \underset{C}{\ast} (t)$. We invoke tree-decompositions and Bass-Serre theory, and classify all infinite groups which admit cubic Cayley graphs of connectivity two in terms of splittings over a subgroup.