ABSTRACT. The class of generalized Chernikov groups is characterized, i.e., the class of periodic locally solvable groups with the primary ascending chain condition. The name of the class is related to the fact that the structure of such groups is close to that of Chernikov groups. Namely, a Chernikov group is defined as a finite extension of a direct product of finitely many quasi-cyclic groups, and a generalized Chernikov group is a layer-finite extension of a direct product A of quasi-cyclic p-groups with finitely many factors for each prime p such that each of its elements does not commute elementwise with only finitely many Sylow subgroups of A. A theorem that characterizes the generalized Chernikov groups in the class of groups with involution is proved.KEY WORDS: Chernikov group, generalized Chernikov group, quasi-cyclic group, layer-finite group, Sylow subgroup.
w IntroductionA promising direction in group theory, which has been developing since the sixties, is the characterization of certain known classes of groups in other classes of groups, i.e., the study of weakest possible sufficient conditions under which the groups of a broader class belong to narrower classes of groups. Earlier the author studied, from this point of view, the class of layer-6n~te groups, i.e., groups in which the set of elements of any given order is finite, and the class of finite extensions of layer-finite groups. The next natural step in this direction is the description of the generalized Chernikov groups, which are extensions of a layer-~n~te group by means of a layer-flnlte group. Just this class is treated in the present paper. In [1] generalized Chernikov groups were characterized in the class of periodic groups without second-order elements. Here we prove a result that enables us to generalize the theorem of [1] to the case of arbitrary periodic groups. In the proof we use the Shlmkov method from [2], and the main result of the present paper is the generalization of Theorem 3.1 in [2]. Condition 1) cannot be omitted in the theorem, because without this condition the theorem fails, in view of the ex~.mples of groups due to Novikov-Adyan [3] and 01'shanskii [4].For the main notions used in the paper, see the monograph by S. N. Chernikov [5].
w Known results, definitions, and auxiliary assertionsIn this section we present known results, prove auxiliary assertions, and also recall the necessary definitions.
Definition.A periodic almost locally solvable group with the primary ascending chain condition is called a generalized Chernikov group.The term "generalized Chernlkov group" first appeared in [6]. Its use can be justified by the fact that, by the Polovitskii theorem (see Proposition 1), a generalized Chernikov group G is the extension of a direct product A of quasi-cyclic p-groups with finitely many factors for each prime p by means of a locally normal group B, and each element of G does not commute elementwise with only finitely many Sylow primary subgroups of A. By comparison, a Chernikov group is a t~nlte extension of ...