A generalization of the Brauer-Fowler theorem

Abstract

The famous Brauer-Fowler theorem states that the order of a finite simple group can be bounded in terms of the order of the centralizer of an involution. Using the classification of finite simple groups, we generalize this theorem and prove that if a simple locally finite group has an involution which commutes with at most $n$ involutions, then the group is finite and its order is bounded in terms of $n$ only. This answers a question of Strunkov from the Kourovka notebook.