Un sottogruppo $H$ di un gruppo $G$ si dice «almost normal» se ha soltanto un numero finito di coniugati in $G$, e ovviamente l'insieme $an\left(G\right)$ costituito dai sottogruppi almost normal di $G$ è un sottoreticolo del reticolo $\mathcal{L}\left(G\right)$ di tutti i sottogruppi di $G$. In questo articolo vengono studiati gli isomorfismi tra reticoli di sottogruppi almost normal, provando in particolare che se $G$ è un gruppo supersolubile e $\overline{G}$ è un gruppo FC-risolubile tale che i reticoli $an\left(G\right)$ e $an\left(\overline{G}\right)$ sono isomorfi, allora anche $\overline{G}$ è supersolubile, e...

In this work it is shown that a locally graded minimal non CC-group G has an epimorphic image which is a minimal non FC-group and there is no element in G whose centralizer is nilpotent-by-Chernikov. Furthermore Theorem 3 shows that in a locally nilpotent p-group which is a minimal non FC-group, the hypercentral and hypocentral lengths of proper subgroups are bounded.

A group $G$ is said to be a PC-group, if $G/C_G\left(x^G\right)$ is a polycyclic-by-finite group for all $x\in G$. A minimal non-PC-group is a group which is not a PC-group but all of whose proper subgroups are PC-groups. Our main result is that a minimal non-PC-group having a non-trivial finite factor group is a finite cyclic extension of a divisible abelian group of finite rank.

We show that a finite nonabelian characteristically simple group $G$ satisfies $n=\left|\pi \right(G\left)\right|+2$ if and only if $G\cong A_5$, where $n$ is the number of isomorphism classes of derived subgroups of $G$ and $\pi \left(G\right)$ is the set of prime divisors of the group $G$. Also, we give a negative answer to a question raised in M. Zarrin (2014).

A subgroup H of a group G is inert if |H: H ∩ H g| is finite for all g ∈ G and a group G is totally inert if every subgroup H of G is inert. We investigate the structure of minimal normal subgroups of totally inert groups and show that infinite locally graded simple groups cannot be totally inert.