On recognizing cayley graphs

Given a class C of Cayley graphs, and given an edge-colored graph G of n vertices and m edges, we are interested in the problem of checking whether there exists an isomorphism 0 preserving the colors such that G is isomorphic by 0 toagraph in C colored by the elements of its generating set. In this paper, we give an 0(m log n)-time algorithm to check whether G is color-isomorphic to a Cayley graph, improving a previous 0(n4'752 log n) algorithm. In the case where C is the class of the Cayley graphs defined on Abelian groups, we give an optimal 0(m)-time algorithm. This algorithm can be extended to check color-isomorphism with Cayley graphs on Abelian groups of given rank. Finally, we propose an optimal 0(m)-time algorithm that tests color-isomorphism between two Cayley graphs on Z„, i.e., between two circulant graphs. This latter algorithm is extended to an optimal 0(n)-time algorithm that tests color-isomorphism between two Abelian Cayley graphs of bounded degree. © Springer-Verlag Berlin Heidelberg 2000.