Probabilistic generation of finite simple groups, II

• DOI: 10.1016/j.jalgebra.2007.10.028
• Publication Date: 2008-02-22T11:25:11Z
• Authors: Thomas Breuer; Robert M. Guralnick; William M. Kantor
• Keywords: Finite set

AbstractIn earlier work it was shown that each nonabelian finite simple group G has a conjugacy class C such that, whenever 1≠x∈G, the probability is greater than 1/10 that G=〈x,y〉 for a random y∈C. Much stronger asymptotic results were also proved. Here we show that, allowing equality, the bound 1/10 can be replaced by 13/42; and, excluding an explicitly listed set of simple groups, the bound 2/3 holds.We use these results to show that any nonabelian finite simple group G has a conjugacy class C such that, if x1, x2 are nontrivial elements of G, then there exists y∈C such that G=〈x1,y〉=〈x2,y〉. Similarly, aside from one infinite family and a small, explicit finite set of simple groups, G has a conjugacy class C such that, if x1, x2, x3 are nontrivial elements of G, then there exists y∈C such that G=〈x1,y〉=〈x2,y〉=〈x3,y〉.We also prove analogous but weaker results for almost simple groups.