Generators of large subgroups of the unit group of integral group rings.
Geometric subgroups of surface braid groups
Let be a surface, let be a subsurface, and let be two positive integers. The inclusion of in gives rise to a homomorphism from the braid group with strings on to the braid group with strings on . We first determine necessary and sufficient conditions that this homomorphism is injective, and we characterize the commensurator, the normalizer and the centralizer of in . Then we calculate the commensurator, the normalizer and the centralizer of in for large surface braid...
Geometry of Free Products.
Gleichungen in freien Produkten mit Amalgam.
Groupes à croissance polynomiale
Groupes dont le centralisateur d'un sous-groupe est d'ordre borné.
Groupes with free 2-generator subsemigroups.
Groups all whose nonnormal subgroups generate a nontrivial proper subgroup.
Groups in which the derived groups of all 2-generator subgroups are cyclic
Groups of periods for arbitrary maps on groups.
Groups of polynomial growth and expanding maps (with an appendix by Jacques Tits)
Groups saturated by a finite set of groups.
Groups which are isomorphic to their nonabelian subgroups
Groups whose all subgroups are ascendant or self-normalizing
This paper studies groups G whose all subgroups are either ascendant or self-normalizing. We characterize the structure of such G in case they are locally finite. If G is a hyperabelian group and has the property, we show that every subgroup of G is in fact ascendant provided G is locally nilpotent or non-periodic. We also restrict our study replacing ascendant subgroups by permutable subgroups, which of course are ascendant [Stonehewer S.E., Permutable subgroups of infinite groups, Math. Z., 1972,...
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 with all subgroups subnormal or nilpotent-by-Chernikov
Groups with dense subnormal subgroups
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 finite conjugacy classes of subnormal subgroups
Groups with many nearly normal subgroups
Un sottogruppo di un gruppo si dice nearly normal se ha indice finito nella sua chiusura normale . In questa nota si caratterizzano i gruppi in cui ogni sottogruppo che non sia nearly normal soddisfa una fissata condizione finitaria per diverse scelte naturali della proprietà .