Generalizzazioni di subnormalità e nilpotenza per gruppi infiniti
Groups which are isomorphic to their nonabelian subgroups
Groups whose proper subgroups are Baer-by-Chernikov or Baer-by-(finite rank)
Our main result is that a locally graded group whose proper subgroups are Baer-by-Chernikov is itself Baer-by-Chernikov. We prove also that a locally (soluble-by-finite) group whose proper subgroups are Baer-by-(finite rank) is itself Baer-by-(finite rank) if either it is locally of finite rank but not locally finite or it has no infinite simple images.
Groups whose proper subgroups are locally finite-by-nilpotent
If is a class of groups, then a group is said to be minimal non -group if all its proper subgroups are in the class , but itself is not an -group. The main result of this note is that if is an integer and if is a minimal non (respectively, )-group, then is a finitely generated perfect group which has no non-trivial finite factor and such that is an infinite simple group; where (respectively, , ) denotes the class of nilpotent (respectively, nilpotent of class at most , locally...
Groups with all subgroups permutable or of finite rank
In this paper we investigate the structure of X-groups in which every subgroup is permutable or of finite rank. We show that every subgroup of such a group is permutable.
Groups with all subgroups subnormal or nilpotent-by-Chernikov
Groups with every subgroup ascendant-by-finite
A subgroup H of a group G is called ascendant-by-finite in G if there exists a subgroup K of H such that K is ascendant in G and the index of K in H is finite. It is proved that a locally finite group with every subgroup ascendant-by-finite is locally nilpotent-by-finite. As a consequence, it is shown that the Gruenberg radical has finite index in the whole group.
Groups with finitely many conjugacy classes of non-normal subgroups of infinite rank
It is proved that if a locally soluble group of infinite rank has only finitely many non-trivial conjugacy classes of subgroups of infinite rank, then all its subgroups are normal.
Groups with many nilpotent subgroups
Groups with Restricted Non-Normal Subgroups.
Groups with small deviation for non-subnormal subgroups
We introduce the notion of the non-subnormal deviation of a group G. If the deviation is 0 then G satisfies the minimal condition for nonsubnormal subgroups, while if the deviation is at most 1 then G satisfies the so-called weak minimal condition for such subgroups (though the converse does not hold). Here we present some results on groups G that are either soluble or locally nilpotent and that have deviation at most 1. For example, a torsion-free locally nilpotent with deviation at most 1 is nilpotent,...
Groups with the weak minimal condition for non-subnormal subgroups II
Let be a group with the property that there are no infinite descending chains of non-subnormal subgroups of for which all successive indices are infinite. The main result is that if is a locally (soluble-by-finite) group with this property then either has all subgroups subnormal or is a soluble-by-finite minimax group. This result fills a gap left in an earlier paper by the same authors on groups with the stated property.
Gruppi che sono unione di un numero finito di laterali doppi
Gruppi con identità semigruppali: su una congettura di M. V. Sapir
M. V. Sapir ha formulato la seguente congettura: non esiste un semigruppo infinito, finitamente generabile, soddisfacente l'identità e immagine omomorfa di un sottosemigruppo di un gruppo nilpotente. Se ciò vale, ogni gruppo risolubile con una base finita per le sue identità semigruppali è abeliano o di esponente finito. In questo lavoro si prova la congettura di Sapir quando l'interderivato è periodico o se è -generato e è periodico.
Gruppi con pochi sottogruppi non quasinormali