English

On $\tau$-closed $n$-multiply $\sigma$-local formations of finite groups

Group Theory 2021-05-04 v1

Abstract

All groups under consideration are finite. Let σ={σiiI}\sigma =\{\sigma_i \mid i\in I \} be some partition of the set of P\mathbb{P}, GG be a group, and F\mathfrak F be a class of groups. Then σ(G)={σiσiπ(G)}\sigma (G)=\{\sigma_i\mid \sigma_i\cap \pi (G)\ne \emptyset\} and σ(F)=GFσ(G).\sigma (\mathfrak F)=\cup_{G\in \mathfrak F}\sigma (G). A function ff of the form f:σ{formations of groups}f:\sigma \to\{\text{formations of groups}\} is called a formation σ\sigma-function. For any formation σ\sigma-function ff the class LFσ(f)LF_\sigma(f) is defined as follows: LFσ(f)=(G is a group G=1 or G1  and  G/Oσi,σi(G)f(σi) for all σiσ(G)). LF_\sigma(f)=(G \text{ is a group } \mid G=1 \text{ or } G\ne 1\ \text{ and }\ G/O_{\sigma_i', \sigma_i}(G) \in f(\sigma_i) \text{ for all } \sigma_i \in \sigma(G)). If for some formation σ\sigma-function ff we have F=LFσ(f),\mathfrak F=LF_\sigma(f), then F\mathfrak F is called σ\sigma-local, ff is called a σ\sigma-local definition of F.\mathfrak F. Every formation is called 0-multiply σ\sigma-local. For n>0,n > 0, a formation F\mathfrak F is called nn-multiply σ\sigma-local provided either F=(1)\mathfrak F=(1) or F=LFσ(f),\mathfrak F=LF_\sigma(f), where f(σi)f(\sigma_i) is (n1)(n-1)-multiply σ\sigma-local for all σiσ(F).\sigma_i\in \sigma(\mathfrak F). Let τ(G)\tau(G) be a set of subgroups of GG such that Gτ(G)G\in \tau(G). Then τ\tau is called a subgroup functor if for every epimorphism φ\varphi : A BA \to~B and any groups Hτ(A)H\in\tau(A) and Tτ(B)T\in\tau(B) we have Hφτ(B)H^{\varphi}\in\tau(B) and Tφ1τ(A)T^{{\varphi}^{-1}}\in\tau(A). A class F\mathfrak F is called τ\tau-closed if τ(G)F\tau(G)\subseteq\mathfrak F for all GFG\in\mathfrak F. We describe some properties of τ\tau-closed nn-multiply σ\sigma-local formations, as well as we prove that the set lσnτl^{\tau}_{\sigma_n} of all τ\tau-closed nn-multiply σ\sigma-local formations forms a complete modular algebraic lattice. In addition, we proof that lσnτl^{\tau}_{\sigma_n} is σ\sigma-inductive and G\mathfrak G-separable.

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Cite

@article{arxiv.2105.00430,
  title  = {On $\tau$-closed $n$-multiply $\sigma$-local formations of finite groups},
  author = {Inna N. Safonova},
  journal= {arXiv preprint arXiv:2105.00430},
  year   = {2021}
}