A Note on the Universal Factorization Property of Groups

We give criteria when a full subcategory [Formula: see text] of the category of groups has [Formula: see text]-universal factorization property ([Formula: see text]-UFP) or [Formula: see text]-strong universal factorization property ([Formula: see text]-SUFP) for a certain category of groups [Formula: see text]. As a byproduct, we give affirmative answers to three unsettled questions in [S.W. Kim, J.B. Lee, Universal factorization property of certain polycyclic groups, J. Pure Appl. Algebra 204 (2006) 555–567].

On the residual and profinite closures of commensurated subgroups

The residual closure of a subgroup H of a group G is the intersection of all virtually normal subgroups of G containing H. We show that if G is generated by finitely many cosets of H and if H is commensurated, then the residual closure of H in G is virtually normal. This implies that separable commensurated subgroups of finitely generated groups are virtually normal. A stream of applications to separable subgroups, polycyclic groups, residually finite groups, groups acting on trees, lattices in products of trees and just-infinite groups then flows from this main result.

On some polycyclic groups with small Hirsch length II

A polycyclic group [Formula: see text] is called a [Formula: see text]-group ([Formula: see text]-group) if every normal abelian subgroup (abelian subgroup) of any finite quotient of [Formula: see text] is generated by [Formula: see text], or fewer, elements and [Formula: see text] is the least integer with this property. In this paper, we describe the structures of [Formula: see text]-groups and [Formula: see text]-groups, and bound the number of generators of [Formula: see text]-groups and the derived lengths of [Formula: see text]-groups, which is a continuation of [H. G. Liu, F. Zhou and T. Xu, On some polycyclic groups with small Hirsch length, J. Algebra Appl. 16(11) (2017) 17502371–175023710].

On some polycyclic groups with small Hirsch length

A polycyclic group [Formula: see text] is called an [Formula: see text]-group if every normal abelian subgroup of any finite quotient of [Formula: see text] is generated by [Formula: see text], or fewer, elements and [Formula: see text] is the least integer with this property. In this paper, the structure of [Formula: see text]-groups and [Formula: see text]-groups is determined.