Examples of rank 3 product action transitive decompositions

Abstract

A transitive decomposition is a pair \((\Gamma, {\mathcal{P}})\) where Γ is a graph and \({\mathcal{P}}\) is a partition of the arc set of Γ such that there is a subgroup of automorphisms of Γ which leaves \({\mathcal{P}}\) invariant and transitively permutes the parts in \({\mathcal{P}}\) . In an earlier paper we gave a characterisation of G-transitive decompositions where Γ is the graph product K m × K m and G is a rank 3 group of product action type. This characterisation showed that every such decomposition arose from a 2-transitive decomposition of K m via one of two general constructions. Here we use results of Sibley to give an explicit classification of those which arise from 2-transitive edge-decompositions of K m .