On $\Sigma_t^{σ}$ -closed classes of finite groups

All analyzed groups are finite. Let $\sigma = \{ \sigma_i| i \in I\}$ be a partition of the set of all primes $\mathbb{P}$. If $n$ is an integer, then the symbol $\sigma (n)$ denotes a set $\{\sigma_i| \sigma_i \cap \pi (n) \not = \emptyset\}$. Integers $n$ and $m$ are called $\sigma$ -coprime i...

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Bibliographic Details
Date:2018
Main Authors: Skiba, A. N., Zhang, Chi, Скиба, А. Н., Чжан, Чи
Format: Article
Language:Russian
Published: Institute of Mathematics, NAS of Ukraine 2018
Online Access:https://umj.imath.kiev.ua/index.php/umj/article/view/1669
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Journal Title:Ukrains’kyi Matematychnyi Zhurnal
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Ukrains’kyi Matematychnyi Zhurnal
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Summary:All analyzed groups are finite. Let $\sigma = \{ \sigma_i| i \in I\}$ be a partition of the set of all primes $\mathbb{P}$. If $n$ is an integer, then the symbol $\sigma (n)$ denotes a set $\{\sigma_i| \sigma_i \cap \pi (n) \not = \emptyset\}$. Integers $n$ and $m$ are called $\sigma$ -coprime if $\sigma (n) \cap \sigma (m) = \emptyset$. Let $t > 1$ be a natural number and let $\mathfrak{F}$ be a class of groups. Then we say that $\mathfrak{F}$ is $\Sigma^{\sigma}_ t$ -closed provided $\mathfrak{F}$ contains each group $G$ with subgroups $A_1, ... ,A_t \in \mathfrak{F}$ whose indices $| G : A_1| ,..., | G : A_t|$ are pairwise $\sigma$ -coprime. We study $\Sigma_t^{σ}$ -closed classes of finite groups.