Large Cayley graphs of small diameter

TL;DR

This paper advances the degree-diameter problem for Cayley graphs by constructing large graphs with small diameters 3, 4, and 5, introducing novel methods including matrix groups over finite fields for diameter 3.

Contribution

It provides new asymptotic constructions for Cayley graphs with diameters 3, 4, and 5, and improves bounds for all odd diameters, using innovative techniques like matrix groups.

Findings

Constructed large Cayley graphs for diameters 3, 4, and 5.

Developed the first diameter 3 construction using matrix groups over finite fields.

Improved bounds for the degree-diameter problem for all odd diameters.

Abstract

The degree-diameter problem seeks to find the largest possible number of vertices in a graph having given diameter and given maximum degree. Very often the problem is studied for restricted families of graph such as vertex-transitive or Cayley graphs, with the goal being to find a family of graphs with good asymptotic properties. In this paper we restrict attention to Cayley graphs, and study the asymptotics by fixing a small diameter and constructing families of graphs of large order for all values of the maximum degree. Much of the literature in this direction is focused on the diameter two case. In this paper we consider larger diameters, and use a variety of techniques to derive new best asymptotic constructions for diameters 3, 4 and 5 as well as an improvement to the general bound for all odd diameters. Our diameter 3 construction is, as far as we know, the first to employ matrix groups over finite fields in the degree-diameter problem.