Symmetry properties of subdivision graphs

TL;DR

This paper investigates the symmetry properties of subdivision graphs, establishing conditions under which they exhibit local s-arc and s-distance transitivity, and classifies certain cases while leaving some open problems.

Contribution

It provides a characterization of symmetry properties of subdivision graphs in relation to the original graph's transitivity, including new classifications for specific parameter ranges.

Findings

S(Σ) is locally s-arc transitive iff Σ is ⌈(s+1)/2⌉-arc transitive for connected Σ.

Diameter of S(Σ) is 2d+δ, with 0≤δ≤2, where d is the diameter of Σ.

Classification of graphs with local s-distance transitivity for s≤5 and s≥15+δ.

Abstract

The subdivision graph $S(\Sigma)$ of a graph $\Sigma$ is obtained from $\Sigma$ by `adding a vertex' in the middle of every edge of $\Si$. Various symmetry properties of $\S(\Sigma)$ are studied. We prove that, for a connected graph $\Sigma$, $S(\Sigma)$ is locally $s$-arc transitive if and only if $\Sigma$ is $\lceil\frac{s+1}{2}\rceil$-arc transitive. The diameter of $S(\Sigma)$ is $2d+\delta$, where $\Sigma$ has diameter $d$ and $0\leqslant \delta\leqslant 2$, and local $s$-distance transitivity of $\S(\Sigma)$ is defined for $1\leqslant s\leqslant 2d+\delta$. In the general case where $s\leqslant 2d-1$ we prove that $S(\Sigma)$ is locally $s$-distance transitive if and only if $\Sigma$ is $\lceil\frac{s+1}{2}\rceil$-arc transitive. For the remaining values of $s$, namely $2d\leqslant s\leqslant 2d+\delta$, we classify the graphs $\Sigma$ for which $S(\Sigma)$ is locally $s$-distance transitive in the cases, $s\leqslant 5$ and $s\geqslant 15+\delta$. The cases $\max\{2d, 6\}\leqslant s\leqslant \min\{2d+\delta, 14+\delta\}$ remain open.