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Let n = [x1, : : :, xn] be the nth lower central word. Suppose that G is a pro, nite group where the conjugacy classes x n(G) contains less than 2@ 0 elements for any x 2 G. We prove that then n+1(G) has , nite order. This generalizes the much celebrated theorem of B. H. Neumann that says that the commutator subgroup of a BFC-group is , nite. Moreover, it implies that a pro, nite group G is , nite-by-nilpotent if and only if there is a positive integer n such that x n(G) contains less than 2@ 0 elements, for any x 2 G.

We prove that the class of pro finite groups G that have a factorization G=AB with A and Babelian closed subgroups, is closed under taking inverse limits of surjective inverse systems. This is a generalization of a recent result by K.H. Hofmann and F.G. Russo. As an application we reprove their generalization of Iwasawa’s structure theorem for quasihamiltonian pro-p groups.

We define monoidal structures on several categories of linear topological modules over the valuation ring of a local field, and study module theory with respect to the monoidal structures. We extend the notion of the Iwasawa algebra to a locally profinite group as a monoid with respect to one of the monoidal structure, which does not necessarily form a topological algebra. This is one of the main reasons why we need monoidal structures. We extend Schneider–, Teitelbaum duality to duality applicable to a locally profinite group through the module theory over the generalised Iwasawa algebra, and give a criterion of the irreducibility of a unitary Banach representation.

Let $\gamma_{n}=[x_{1},\ldots,x_{n}]$ be the $n$th lower central word and $X_{n}(G)$ the set of $\gamma_{n}$-values in a group $G$. Suppose that $G$ is a profinite group where, for each $g\in G$, there exists a positive integer $n=n(g)$ such that the set $g^{X_{n}(G)}=\{g^{y}\,|\,y\in X_{n}(G)\}$ contains less than $2^{\aleph_{0}}$ elements. We prove that $G$ is a finite-by-nilpotent group.

We provide some characterization theorems about just infinite profinite residually solvable Lie algebras, similarly to what C. Reid has done for just infinite profinite groups. In particular, we prove that a profinite residually solvable Lie algebra is just infinite if and only if its obliquity subalgebra has finite codimension in the Lie algebra, and we establish a criterion for a profinite residually solvable Lie algebra to be just infinite, looking at the finite Lie algebras occurring in the inverse system.

In this paper, in addition to some elementary facts about the ultra-groups, which their structure based on the properties of the transversal of a subgroup of a group, we focus on the relation between a group and an ultra-group. It is verified that every group is an ultra-group, but the converse is not true generally. We present the conditions under which, for every normal subultra-group of an ultra-group over a group, there exists a normal subgroup of that certain group. Moreover, by proving this feature that a monomorphism in groups preserve the ultra-groups over groups, we show that, corresponding to any monomorphism in groups, there is an ultragroup homomorphism on the subgroups of those groups. Finally, we prove isomorphism theorems for ultra-groups. These theorems connect three notions subultra-group, normal subultra-group, quotient ultra-group, and directly, similar to the isomorphism theorems in group theory and module theory are proved.

In their paper "Finite groups whose noncentral commuting elements have centralizers of equal size", S. Dolfi, M. Herzog and E. Jabara classify the groups in question- which they call CH-groups- up to finite p-groups. Our goal is to investigate the finite p-groups in the class. The chief result is that a finite p-group that is a CH -group either has an abelian maximal subgroup or is of class at most p+1. Detailed descriptions, in some cases characterisations up to isoclinism, are given.

This article discusses the focus groups as a useful method in qualitative research. Focus groups are less discussed in research sources, while they have many applications in qualitative researches. In this article, the origin, history, definition, and application of the focus groups are studied. Also, the method of participant selection, the size and count of groups, method of questioning, survey size, survey type, moderator specifications, collecting and analyzing data in focus groups are discussed.