Abstract

The following variations of the theorems of Higman, Kreknin, and Kostrikin are proved: let L be a (/n)-graded Lie ring with trivial zero-component L0 = 0; if for some m each grading component commutes with all but at most m components, then L is soluble of derived length bounded above in terms of m; if, in addition, n is a prime, then L is nilpotent of class bounded above in terms of m. As an application to 2-Frobenius groups, it is proved that if a finite Frobenius group BC with complement C of order t acts on a finite group A so that AB is also a Frobenius group, (t, A) = 1, and CA(C) is abelian, then A is nilpotent of class bounded above in terms of t. © 2008 London Mathematical Society.