Girth-regular graphs

Abstract

We introduce a notion of a girth-regular graph as a k-regular graph for which there exists a non-descending sequence (a₁, a₂, …, a_k) (called the signature) giving, for every vertex u of the graph, the number of girth cycles the edges with end-vertex u lie on. Girth-regularity generalises two very different aspects of symmetry in graph theory: that of vertex transitivity and that of distance-regularity. For general girth-regular graphs, we give some results on the extremal cases of signatures. We then focus on the cubic case and provide a characterisation of cubic girth-regular graphs of girth up to 5.