The Prime Graph of a Sporadic Simple Group

Abstract

Let Gbe a finite group and Sa sporadic simple group. We denote by π(G) the set of all primes dividing the order of G. The prime graph Γ(G) of Gis defined in the usual way connecting pand qin π(G) when there is an element of order pqin G. The main purpose of this paper is to determine finite group Gsatisfying Γ(G) = Γ(S) (See Theorem 3) and to give applications which generalize Abe (Abe, S. Two ways to characterize 26 sporadic finite simple groups. Preprint) and Chen (Chen, G. (1996). A new characterization of sporadic simple groups. Algebra Colloq.3:49–58). The results are elementary but quite useful.

Key Words:

• Sporadic simple groups
• Prime graphs of finite groups

Acknowledgment

The author would like to thank Professors Naoki Chigira, Nobuo Iiyori and Hiroyoshi Yamaki for their helpful suggestions and discussions.