On Finite Extension and Conditions on Infinite Subsets of Finitely Generated FC and FN<sub>k</sub>-groups
Let k>0 an integer. F, τ,
N, Nk, and A denote, respectively, the classes of
finite, torsion, nilpotent, nilpotent of class at most k, group in which every
two generator subgroup is in Nk and abelian groups. The main results
of this paper is, firstly, to prove that in the class of finitely generated
FN-group, the property FC is closed under finite extension. Secondly, we prove
that a finitely generated τN-group in the class ((τNk)τ,∞) ( respectively
((τNk)τ,∞)∗)
is a τ-group (respectively τNc
for certain integer c=c(k) ) and deduce that a finitely generated FN-group in
the class ((FNk)F,∞) (respectively ((FNk)F,∞)∗)
is -group (respectively FNc
for certain integer c=c(k)). Thirdly we prove that a finitely generated
NF-group in the class ((FNk)F,∞) ( respectively ((FNk)F,∞)∗)
is F-group (respectively NcF
for certain integer c=c(k)). Finally and particularly, we deduce that a
finitely generated FN-group in the class ((FA)F,∞) (respectively ((FC)F,∞)∗,
((FN₂)F,∞)∗)
is in the class FA (respectively FN₂,
FN₃(2)).
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