Kurosh-Amitsur radical theory for groups.
A group in a variety is said to be absolutely-, and we write , if central extensions by are again in . Absolutely-abelian groups have been classified by F. R. Beyl. In this paper we concentrate upon the class of absolutely-nilpotent of class groups. We prove some closure properties of the class and we show that every nilpotent of class group can be embedded in an -gvoup. We describe all metacyclic -groups and we characterize -generator and infinite -generator -groups. Finally...
Using a lemma on subnormal subgroups, the problem of nilpotency of multiplication groups and inner permutation groups of centrally nilpotent loops is discussed.