Automorphism groups of Cayley graphs generated by block transpositions and regular Cayley maps

TL;DR

This paper characterizes the automorphism group of Cayley graphs generated by block transpositions, revealing a structure involving dihedral groups and exploring implications for regular Cayley maps with bioinformatics relevance.

Contribution

It proves that the automorphism group of these Cayley graphs is a product of left translations and a dihedral group, and analyzes related subgraphs and Cayley maps.

Findings

Automorphism group is the product of left translation group and dihedral group D_{n+1}.

Subgraph induced by block transpositions has a dihedral automorphism group.

Identifies a connection between cyclic subgroups and regular Cayley maps on Sym_n.

Abstract

This paper deals with the Cayley graph $\mathrm{Cay}(\mathrm{Sym}_n,T_n),$ where the generating set consists of all block transpositions. A motivation for the study of these particular Cayley graphs comes from current research in Bioinformatics. As the main result, we prove that Aut$(\mathrm{Cay}(\mathrm{Sym}_n,T_n))$ is the product of the left translation group by a dihedral group $\mathsf{D}_{n+1}$ of order $2(n+1)$. The proof uses several properties of the subgraph $\Gamma$ of $\mathrm{Cay}(\mathrm{Sym}_n,T_n)$ induced by the set $T_n$. In particular, $\Gamma$ is a $2(n-2)$-regular graph whose automorphism group is $\mathsf{D}_{n+1},$ $\Gamma$ has as many as $n+1$ maximal cliques of size $2,$ and its subgraph $\Gamma(V)$ whose vertices are those in these cliques is a $3$-regular, Hamiltonian, and vertex-transitive graph. A relation of the unique cyclic subgroup of $\mathsf{D}_{n+1}$ of order $n+1$ with regular Cayley maps on $\mathrm{Sym}_n$ is also discussed. It is shown that the product of the left translation group by the latter group can be obtained as the automorphism group of a non-$t$-balanced regular Cayley map on $\mathrm{Sym}_n$.