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Abstract
Let be a set of primes. We show that -separable groups have a conjugacy class of subgroups which specialize to Carter subgroups, i.e. self-normalizing nilpotent subgroups, or equivalently, nilpotent projectors, when specializing to soluble groups.
In this paper, we complete the classification of Hall subgroups in finite almost simple groups. We also prove that a finite group satisfies D π if and only if all its composition factors satisfy D π .
LetGbe a finite group and π a set of primes. In this paper, some new criteria for π-separable groups and π-solvable groups in terms of Hall subgroups are proved. The main results are the following:Theorem.G is aπ-separable group if and only if(1)G satisfies Eπand Eπ′;(2)G satisfies Eπ∪{q}and Eπ′∪{p}for all p∈π,q∈π′.Theorem.G is aπ-separable group if and only if(1)G satisfies Eπand Eπ′;(2)G satisfies Ep,qfor all p∈πand q∈π′.
Summary Dp-property (p=set of primes) in finite groups is not in general inherited by subgroups. In this paper, as evidence in favor of the following conjecture (F. Gross): (o) If a finite group G satisfies Dp then its normal subgroups satisfy Dp-property as well. the Author shows that if the Dp and the Dp-properties (p'=set of the primes not in p) hold together in a finite group G, then both are inherited by the normal subgroups of G. As a corollary, the characterization of the groups satisfying both the properties Dp and Dp' is given in terms of the composition factors.
A lattice formation is a class of groups whose elements are the direct product of Hall subgroups corresponding to pairwise disjoint sets of primes. In this paper Fitting classes with stronger closure properties involving F-subnormal subgroups, for a lattice formation F of full characteristic, are studied. For a subgroup-closed saturated formation G, a characterisation of the G-projectors of finite soluble groups is also obtained. It is inspired by the characterisation of the Carter subgroups as the N-projectors, N being the class of nilpotent groups.