A note on the automorphism group of the Hamming graph

Let $\Omega$ be a $m$-set, where $m>1$, is an integer. The Hamming graph $H(n,m)$, has $\Omega ^{n}$ as its vertex-set, with two vertices are adjacent if and only if they differ in exactly one coordinate. In this paper, we provide a proof on the automorphism group of the Hamming graph $H(n,m)$, by using elementary facts of group theory and graph theory.Comment: 8 pages, 1 figure

Cayley properties of the line graphs induced by consecutive layers of the hypercube

Let $n >3$ and $0< k < \frac{n}{2}$ be integers. In this paper, we investigate some algebraic properties of the line graph of the graph ${Q_n}(k,k+1)$ where ${Q_n}(k,k+1)$ is the subgraph of the hypercube $Q_n$ which is induced by the set of vertices of weights $k$ and $k+1$. In the first step, we determine the automorphism groups of these graphs for all values of $n,k$. In the second step, we study Cayley properties of the line graphs of these graphs. In particular, we show that if $k\geq 3$ and $n \neq 2k+1$, then except for the cases $k=3, n=9$ and $k=3, n=33$, the line graph of the graph ${Q_n}(k,k+1)$ is a vertex-transitive non-Cayley graph. Also, we show that the line graph of the graph ${Q_n}(1,2)$ is a Cayley graph if and only if $n$ is a power of a prime $p$. Moreover, we show that for \lq{}almost all\rq{} even values of $k$, the line graph of the graph ${Q_{2k+1}}(k,k+1)$ is a vertex-transitive non-Cayley graph