Right Engel elements of stability groups of general series in vector spaces

Let V be an arbitrary vector space over some division ring D, L a general series of subspaces of V covering all of V \ {0} and S the full stability subgroup of L in GL(V). We prove that always the set of bounded right Engel elements of S is equal to the w-th term of the upper central series of S and that the set of right Engel elements of S is frequently equal to the hypercentre of S

On the fixed-point set of an automorphism of a group

Let Ø be an automorphism of a group G. Under variousfiniteness or solubility hypotheses, for example under polycyclicity, the commutator subgroup [G; Ø] has finite index in G if thefixed-point set CG(Ø) of Ø in G isfinite, but not conversely, even for polycyclic groups G. Here we consider a stronger, yet natural, notion of what it means for [G;Ø] to have finite index' in G and show that in many situations, including G polycyclic, it is equivalent to CG(Ø) being finite

On groups of finite rank

We study the structure of groups of finite (Prufer) rank in a very wide class of groups and also of central extensions of such groups. As a result we are able to improve, often substantially, on a number of known numerical bounds, in particular on bounds for the rank (resp. Hirsch number) of the derived subgroup of a group in terms of the rank (resp. Hirsch number) of its central quotient and on bounds for the rank of a group in terms of its Hirsch numbe

A note on the Mittag–Leffler condition for Bredon-modules

In this note we show the Bredon-analogue of a result by Emmanouil and Talelli, which gives a criterion when the homological and cohomological dimensions of a countable group $G$ agree. We also present some applications to groups of Bredon-homological dimension $1$.Comment: 10 page

Groups with no proper contranormal subgroups

We consider which groups G are nilpotent if they have a nilpotent normal subgroup N with G/N a restricted soluble group and if G is the only contranormal subgroup of G. This supplements Kurdachenko, Otal, and Subbotin work of 2009, where they consider the corresponding question but with G/N nilpotent and N a restricted soluble normal subgroup