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Search Results: 1 - 10 of 87830 matches for " Evgenii I. Khukhro "
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Frobenius groups of automorphisms and their fixed points
Evgenii I. Khukhro,Natalia Yu. Makarenko,Pavel Shumyatsky
Mathematics , 2010, DOI: 10.1515/form.2011.152
Abstract: Suppose that a finite group $G$ admits a Frobenius group of automorphisms $FH$ with kernel $F$ and complement $H$ such that the fixed-point subgroup of $F$ is trivial: $C_G(F)=1$. In this situation various properties of $G$ are shown to be close to the corresponding properties of $C_G(H)$. By using Clifford's theorem it is proved that the order $|G|$ is bounded in terms of $|H|$ and $|C_G(H)|$, the rank of $G$ is bounded in terms of $|H|$ and the rank of $C_G(H)$, and that $G$ is nilpotent if $C_G(H)$ is nilpotent. Lie ring methods are used for bounding the exponent and the nilpotency class of $G$ in the case of metacyclic $FH$. The exponent of $G$ is bounded in terms of $|FH|$ and the exponent of $C_G(H)$ by using Lazard's Lie algebra associated with the Jennings--Zassenhaus filtration and its connection with powerful subgroups. The nilpotency class of $G$ is bounded in terms of $|H|$ and the nilpotency class of $C_G(H)$ by considering Lie rings with a finite cyclic grading satisfying a certain `selective nilpotency' condition. The latter technique also yields similar results bounding the nilpotency class of Lie rings and algebras with a metacyclic Frobenius group of automorphisms, with corollaries for connected Lie groups and torsion-free locally nilpotent groups with such groups of automorphisms. Examples show that such nilpotency results are no longer true for non-metacyclic Frobenius groups of automorphisms.
The Andrews-Curtis Conjecture and Black Box Groups
Alexandre V. Borovik,Evgenii I. Khukhro,Alexei G. Myasnikov
Mathematics , 2001,
Abstract: The paper discusses the Andrews-Curtis graph of a normal subgroup N in a group G. The vertices of the graph are k-tuples of elements in N which generate N as a normal subgroup; two vertices are connected if one them can be obtained from another by certain elementary transformations. This object appears naturally in the theory of black box finite groups and in the Andrews-Curtis conjecture in algebraic topology. We suggest an approach to the Andrews-Curtis conjecture based on the study of Andrews-Curtis graphs of finite groups, discuss properties of Andrews-Curtis graphs of some classes of finite groups and results of computer experiments with generation of random elements of finite groups by random walks on their Andrews-Curtis graphs.
Automorphism invariance and identities
Evgenii I. Khukhro,Anton A. Klyachko,Natalia Yu. Makarenko,Yulia B. Melnikova
Mathematics , 2008, DOI: 10.1112/blms/bdp056
Abstract: If an outer (multilinear) commutator identity holds in a large subgroup of a group, then it holds also in a large characteristic subgroup. Similar assertions are valid for algebras and their ideals or subspaces. Varying the meaning of the word "large", we obtain many interesting facts. These results cannot be extended to arbitrary (non-multilinear) identities. As an application, we give a sharp estimate for the `virtual derived length' of (virtually solvable)-by-(virtually solvable) groups.
On finite soluble groups with almost fixed-point-free automorphisms of non-coprime order
E. I. Khukhro
Mathematics , 2015,
Abstract: It is proved that if a finite $p$-soluble group $G$ admits an automorphism $\varphi$ of order $p^n$ having at most $m$ fixed points on every $\varphi$-invariant elementary abelian $p'$-section of $G$, then the $p$-length of $G$ is bounded above in terms of $p^n$ and $m$; if in addition the group $G$ is soluble, then the Fitting height of $G$ is bounded above in terms of $p^n$ and $m$. It is also proved that if a finite soluble group $G$ admits an automorphism $\psi$ of order $p^aq^b$ for some primes $p,q$, then the Fitting height of $G$ is bounded above in terms of $|\psi |$ and $|C_G(\psi )|$.
Words and pronilpotent subgroups in profinite groups
E. I. Khukhro,P. Shumyatsky
Mathematics , 2013,
Abstract: Let $w$ be a multilinear commutator word, that is, a commutator of weight $n$ in $n$ different group variables. It is proved that if $G$ is a profinite group in which all pronilpotent subgroups generated by $w$-values are periodic, then the verbal subgroup $w(G)$ is locally finite.
Almost Engel finite and profinite groups
E. I. Khukhro,P. Shumyatsky
Mathematics , 2015,
Abstract: Let $g$ be an element of a group $G$. For a positive integer $n$, let $E_n(g)$ be the subgroup generated by all commutators $[...[[x,g],g],\dots ,g]$ over $x\in G$, where $g$ is repeated $n$ times. We prove that if $G$ is a profinite group such that for every $g\in G$ there is $n=n(g)$ such that $E_n(g)$ is finite, then $G$ has a finite normal subgroup $N$ such that $G/N$ is locally nilpotent. The proof uses the Wilson--Zelmanov theorem saying that Engel profinite groups are locally nilpotent. In the case of a finite group $G$, we prove that if, for some $n$, $|E_n(g)|\leq m$ for all $g\in G$, then the order of the nilpotent residual $\gamma _{\infty}(G)$ is bounded in terms of $m$.
Nonsoluble and non-p-soluble length of finite groups
E. I. Khukhro,P. Shumyatsky
Mathematics , 2013,
Abstract: Every finite group $G$ has a normal series each of whose factors either is soluble or is a direct product of nonabelian simple groups. We define the nonsoluble length $\lambda (G)$ as the minimum number of nonsoluble factors in a series of this kind. Upper bounds for $\lambda (G)$ appear in the study of various problems on finite, residually finite, and profinite groups. We prove that $\lambda (G)$ is bounded in terms of the maximum $2$-length of soluble subgroups of $G$, and that $\lambda (G)$ is bounded by the maximum Fitting height of soluble subgroups. For an odd prime $p$, the non-$p$-soluble length $\lambda _p(G)$ is introduced, and it is proved that $\lambda _p(G)$ does not exceed the maximum $p$-length of $p$-soluble subgroups. We conjecture that for a given prime $p$ and a given proper group variety ${\frak V}$ the non-$p$-soluble length $\lambda _p(G)$ of finite groups $G$ whose Sylow $p$-subgroups belong to ${\frak V}$ is bounded. In this paper we prove this conjecture for any variety that is a product of several soluble varieties and varieties of finite exponent.
On the length of finite groups and of fixed points
E. I. Khukhro,P. Shumyatsky
Mathematics , 2014,
Abstract: The generalized Fitting height of a finite group $G$ is the least number $h=h^*(G)$ such that $F^*_h(G)=G$, where the $F^*_i(G)$ is the generalized Fitting series: $F^*_1(G)=F^*(G)$ and $F^*_{i+1}(G)$ is the inverse image of $F^*(G/F^*_{i}(G))$. It is proved that if $G$ admits a soluble group of automorphisms $A$ of coprime order, then $h^*(G)$ is bounded in terms of $h^* (C_G(A))$, where $C_G(A)$ is the fixed-point subgroup, and the number of prime factors of $|A|$ counting multiplicities. The result follows from the special case when $A=\langle\varphi\rangle$ is of prime order, where it is proved that $F^*(C_G(\varphi ))\leqslant F^*_{9}(G)$. The nonsoluble length $\lambda (G)$ of a finite group $G$ is defined as the minimum number of nonsoluble factors in a normal series each of whose factors either is soluble or is a direct product of nonabelian simple groups. It is proved that if $A$ is a group of automorphisms of $G$ of coprime order, then $\lambda (G)$ is bounded in terms of $\lambda (C_G(A))$ and the number of prime factors of $|A|$ counting multiplicities.
On the length of finite factorized groups
E. I. Khukhro,P. Shumyatsky
Mathematics , 2014,
Abstract: The nonsoluble length $\lambda (G)$ of a finite group $G$ is defined as the number of nonsoluble factors in a shortest normal series each of whose factors either is soluble or is a direct product of nonabelian simple groups. The generalized Fitting height of a finite group $G$ is the least number $h=h^*(G)$ such that $F^*_h(G)=G$, where $F^*_1(G)=F^*(G)$ is the generalized Fitting subgroup, and $F^*_{i+1}(G)$ is the inverse image of $F^*(G/F^*_{i}(G))$. It is proved that if a finite group $G=AB$ is factorized by two subgroups of coprime orders, then the nonsoluble length of $G$ is bounded in terms of the generalized Fitting heights of $A$ and $B$. It is also proved that if, say, $B$ is soluble of derived length $d$, then the generalized Fitting height of $G$ is bounded in terms of $d$ and the generalized Fitting height of $A$.
Admissible Differential Bases in Banach Spaces
Evgenii I. Berezhnoj
International Journal of Mathematics and Mathematical Sciences , 2013, DOI: 10.1155/2013/748645
Abstract: In the present work, a new method for constructing differential bases is presented. The bases constructed by this method allow us to distinguish symmetric spaces with different behaviour of fundamental functions at zero, as in the case of Hayes and Stokolos, and even allow us to distinguish Lorentz and Marzinkiewicz spaces or Lebesgue and Marzinkiewicz spaces whose fundamental functions are the same. 1. Introduction We recall certain definitions connected with differential bases [1]. By a differential basis at a point is meant a family of bounded measurable sets with positive measure which contain and are such that there is at least one sequence satisfying the condition . A union of such families is called a differential basis in . We note that the bulk of the problems and assertions in the theory of differentiation of integrals in consists of testing the validity almost everywhere of some fact. Therefore, it is natural to consider differential bases which are defined, not for all points in , but only almost everywhere. In what follows, we will make use of these observations. The classical examples of differential bases are the bases in , usually denoted by ?? and consisting of all rectangular parallelepipeds of the form which satisfy the condition for and , . A basis made up of open sets is called a Busemann-Feller basis (BF-basis) if it follows from the conditions and such that . The significance of the introduction of -bases lies in the fact that questions arising in the theory of differentiation with respect to bases can be easily resolved for bases. We now define the upper and lower derivatives of the integral of a locally integrable function at a point with respect to a basis by means of the identities We note that the upper and lower derivatives are variants of the functionals and which are the subject of investigation in several sections of the chapter 1 in [2]. Following [1], we say that a basis ??differentiates the integral of if the identities hold almost everywhere. If differentiates the integral of any function in the space , then we say that the basis ??differentiates the space . If the basis differentiates , then it is said to be a density basis [1]. One of the fundamental problems of the theory of differentiation of integrals has the following form: given two function spaces , which are different in some sense, is it possible to distinguish these two spaces with the help of differential bases? In other words, does there exist a differential basis, which differentiates all integrals obtained from functions in , but a function can be found
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