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Some Engel conditions on infinite subsets of certain groups

Published online by Cambridge University Press:  17 April 2009

Alireza Abdollahi
Affiliation:
Department of Mathematics, University of IsfahanIsfahan 81744, Iran e-mail: abdolahi@math.ui.ac.ir
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Abstract

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Let k be a positive integer. We denote by ɛk(∞) the class of all groups in which every infinite subset contains two distinct elements x, y such that [x,k y] = 1. We say that a group G is an -group provided that whenever X, Y are infinite subsets of G, there exists xX, yY such that [x,k y] = 1. Here we prove that:

(1) If G is a finitely generated soluble group, then G ∈ ɛ3(∞) if and only if G is finite by a nilpotent group in which every two generator subgroup is nilpotent of class at most 3.

(2) If G is a finitely generated metabelian group, then G ∈ ɛk(∞) if and only if G/Zk (G) is finite, where Zk (G) is the (k + 1)-th term of the upper central series of G.

(3) If G is a finitely generated soluble ɛk(∞)-group, then there exists a positive integer t depending only on k such that G/Zt (G) is finite.

(4) If G is an infinite -group in which every non-trivial finitely generated subgroup has a non-trivial finite quotient, then G is k-Engel. In particular, G is locally nilpotent.

Type
Research Article
Copyright
Copyright © Australian Mathematical Society 2000

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