On transitive permutation groups with exponential graph growth

Abstract

Let $\Gamma$ be a finite connected graph and $G$ a vertex-transitive group of its automorphisms. The pair $(\Gamma, G)$ is said to be locally-$L$ if the permutation group induced by the action of the vertex-stabiliser $G_v$ on the set of neighbours of a vertex $v$ in $\Gamma$ is permutation isomorphic to $L$. The maximum growth of $|G_v|$ as a function of $|V\Gamma|$ for locally-$L$ pairs $(\Gamma,G)$ is called the graph growth of $L$. We prove that if $L$ is a transitive permutation group on a set $\Omega$ admitting a nontrivial block $B$ such that the pointwise stabiliser of $\Omega\setminus B$ in $L$ is nontrivial, then the graph growth of $L$ is exponential. This generalises several results in the literature on transitive permutation groups with exponential graph growth.