Let G be a finite group and H a subgroup of G. We say that H is an ℌ-subgroup of G if NG (H) ∩ Hg ≤ H for all g ∈G; H is called weakly ℌ-embedded in G if G has a normal subgroup K such that HG = HK and H ∩ K is an ℌ-subgroup of G, where HG is the normal clousre of H in G, i. e., HG = 〈Hg|g ∈ G〉. In this paper, we study the p-nilpotence of a group G under the assumption that every subgroup of order d of a Sylow p-subgroup P of G with 1 < d < |P| is weakly ℌ-embedded in G. Many known results related to p-nilpotence of a group G are generalized.
A number of authors have studied the structure of a finite group G under the assumption that some subgroups of G are well located in G. We will generalize the notion of s-permutable and s-permutably embedded subgroups and we will obtain new criterions of p-nilpotency and supersolvability of groups. We also generalize some known results.
Let be a class of groups and G a finite group. We call a set Σ of subgroups of G a G-covering subgroup system for
if whenever . Let p be any prime dividing |G| and P a Sylow p-subgroup of G. Then we write Σp to denote the set of subgroups of G which contains at least one supplement to G of each maximal subgroup of P. We prove that the sets Σp and Σp∪Σq, where q≠p, are G-covering subgroup systems for many classes of finite groups.