Factorizations of Almost Simple Groups with Applications

Abstract

The classification of factorizations $G=HK$ of finite almost simple groups, proposed by Wielandt in 1979 and pursued through several partial classifications, has remained open in one major case. We settle that case: for every finite almost simple classical group $G$, we determine all factorizations $G=HK$ in which both $H$ and $K$ have a unique nonsolvable composition factor, completing the classification of factorizations of finite almost simple groups. Among other consequences of this classification, we prove that the smallest dimension of a biperfect bicrossproduct Hopf algebra is $41287680$.