Connective Constants on Cayley Graphs

TL;DR

This paper proves that the connective constant of certain Cayley graphs of finitely presented groups is continuous under local convergence, confirming a conjecture about the stability of this graph invariant.

Contribution

It establishes the continuity of the connective constant for a class of Cayley graphs under local convergence, partially confirming a conjecture by Benjamini.

Findings

Connective constant converges under local graph convergence.

Continuity holds for Cayley graphs of finitely presented groups.

Supports conjecture on invariance of connective constant.

Abstract

For a transitive infinite connected graph $G$, let $\mu(G)$ be its connective constant. Denote by $\mathbf{\cal G}$ the set of Cayley graphs for finitely generated infinite groups with an infinite-order generator which is independent of other generators. Assume $G\in\mathbf{\cal G}$ is a Cayley graph of a finitely presented group, and Cayley graph sequence $\{G_n\}_{n=1}^{\infty}\subset \mathbf{\cal G}$ converges locally to $G.$ Then $\mu(G_n)$ converges to $\mu(G)$ as $n\rightarrow\infty.$ This confirms partially a conjecture raised by Benjamini [2013. {\it Coarse geometry and randomness.} Lect. Notes Math. {\bf 2100}. Springer.] that connective constant is continuous with respect to local convergence of infinite transitive connected graphs.