Maximal Cocliques in ${\mathrm{PSL}}_2(q)$

Abstract

The generating graph of a finite group is a structure which can be used to encode certain information about the group. It was introduced by Liebeck and Shalev and has been further investigated by Lucchini, Maróti, Roney-Dougal and others. We investigate maximal cocliques (totally disconnected induced subgraphs of the generating graph) in ${\mathrm{PSL}}_2(q)$ for $q$ a prime power and provide a classification of the `large' cocliques when $q$ is prime. We then provide an interesting geometric example which contradicts this result when $q$ is not prime and illustrate why the methods used for the prime case do not immediately extend to the prime-power case with the same result.

12 pages, typos corrected, minor reorganising. To appear in Communications in Algebra