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BRIEF MESSAGE
Abelian groups with finite primary quotients
A. A. Fomin,
A. V. Tsarev Moscow State Pedagogical University (Moscow)
Abstract:
An abelian group
$A$ is called
$\pi$-bounded for a set of prime numbers
$\pi$, if all
$p$-primary components
$t_{p}(A/B)$ are finite for every subgroup
$B\subset A$ and for every
$p\in\pi$. E. V. Sokolov has introduced the class of
$\pi$-bounded groups investigating
$\mathcal{F}_{\pi}$-separable and
$\pi^\prime$-isolated subgroups in the general group theory. The description of torsion
$\pi$-bounded groups is trivial. E. V. Sokolov has proved that the description of mixed
$\pi$-bounded groups can be reduced to the case of torsion free groups.
We consider the class of
$\pi$-bounded torsion free groups in the present paper and we prove that this class of groups coincides with the class of
$\pi$-local torsion free abelian groups of finite rank. We consider also abelian groups satisfying the condition
$(\ast)$, that is such groups that their quotient groups don't contain subgroups of the form
$\mathbb{Z}_{p^{\infty}}$ for all prime numbers
$p\in\pi$, where
$\pi$ is a fixed set of prime numbers. It is clear that all
$\pi$-bounded groups satisfy the condition
$(\ast)$. We prove that an abelian group
$A$ satisfies the condition
$(\ast)$ if and only if both groups
$t(A)$ and
$A/t(A)$ satisfy the condition
$(\ast)$. We construct also an example of a non-splitting mixed group of rank
$1$, satisfying the condition
$(\ast)$, for every infinite set
$\pi$ of prime numbers.
Keywords:
abelian group, separability of subgroups, $\pi$-bounded abelian group, $\pi$-local torsion free abelian group.
UDC:
512.541 Received: 12.08.2021
Accepted: 21.12.2021
DOI:
10.22405/2226-8383-2021-22-5-400-406