含指数为素数幂的超可解子群的有限群

本文讨论含指数为素数幂的超可解子群的有限群的结构．首先得到具有这种性质的非Abel有限单群的完全分类定理．其次给出了这类群是可解群和超可解群的若干充分条件．     

有限群为超可解群的充要条件

用置换条件刻画有限可解群的超可解性已有大量结果,本文的目的是给出另外一些有限可解群为超可解的充要条件。其主要结果是: 1.设G是满足置换条件的有限可解群,则G是超可解群当且仅当如下条件之一成立。 1)G的2-Sylow子群G_2的换位子群G_2′G. 2)G有正规2-补。 2.设G是有限可解群,则G超可解当且仅当G和G′均满足置换条件.     

两个正规p-超可解子群的积

本文研究了两个正规的p-超可解子群的积构成的极小非P-超可解群的结构的问题.利用有限群论和群类论的一些基本方法,获得了两个正规的p-超可解子群的积仍为P-超可解群的一些充分条件,并推广了文[1]中关于超可解群的情况.     

一类2~3p~n(p=3,7)阶群的构造

本文利用超可解群的性质,通过群的扩张理论,利用一种新的证明方法解决了２~３ｐ~ｎ（ｐ＝３,７）阶群当ｓｙｌｏｗ－ｐ子群为循环群时的构造．     

子群次正规性对有限群可解性的影响

考查了次正规子群对有限群结构的影响,得到有限群可解的若干充分条件和超可解的一个充分条件.     

一类2^3p^n（p=3,7）阶群的构造

本文利用超可解群的性质,通过群的扩张理论,利用一种新的证明方法解决了２＾３ｐ＾ｎ（ｐ＝３,７）阶群当ｓｙｌｏｗ－ｐ子群来循环时的构造。     

某些子群是半正规的有限群

本文旨在考查极大子群对有限群结构的影响．首先给出了商群超可解的群是超可解群的若干充分条件；其次考查了ｎ－极大子群对有限群的可解性及超可解性的影响     

有限群极大子群的强θ*-完备

首次给出有限群极大子群的强θ^＊-完备的定义，利用这一概念得到关于群可解性、超可解性的新的充要条件．     

超可解群的若干充分条件

本文研究了有限群的超可解性问题，利用子群的共轭可换性概念及极小反例法，获得了一个群为超可解的若干充分条件．举例说明了主要结果中的假设条件是不可少的．     

Baer超可解性定理的两点应用

本文通过Baer的超可解性定理、证明了有限生成的超Abel群的两个超可解性条件,包含了Hup－pert和Baer关于有限超可解群的结果[3]．     

幂零Hall π-子群的存在性

本文首先将Ｈａｌ定理推广为：设Ｎ为Ｇ的正规子群，若Ｎ为Ｅｎπ群，Ｇ／Ｎ为Ｄπ群，则Ｇ为Ｄπ群．在此基础上得到了群Ｇ为Ｅｎπ群的充要条件为：（１）Ｇ存在正规子群Ｎ，满足Ｎ及Ｇ／Ｎ为Ｅｎπ群；（２）对任意ｐ∈π，任意ｑ∈π ｛ｐ｝及任意ｐ 元素ｘ，ＣＧ（ｘ）含Ｇ的Ｓｙｌｏｗｑ 子群．另外，我们对非Ａｂｌｅ单群的情形也进行了一些讨论．     

On Pairs of Commuting Involutions in Sym(n) and Alt(n)

The number of pairs of commuting involutions in Sym(n) and Alt(n) is determined up to isomorphism. It is also proven that, up to isomorphism and duality, there are exactly two abstract regular polyhedra on which the group Sym(6) acts as a regular automorphism group.     

Bestvina's Normal Form Complex and the Homology of Garside Groups

A Garside group is a group admitting a finite lattice generating set . Using techniques developed by Bestvina for Artin groups of finite type, we construct K(π, 1)s for Garside groups. This construction shows that the (co)homology of any Garside group G is easily computed given the lattice , and there is a simple sufficient condition that implies G is a duality group. The universal covers of these K(π, 1)s enjoy Bestvina's weak nonpositive curvature condition. Under a certain tameness condition, this implies that every solvable subgroup of G is virtually Abelian.     

Homological approximations for profinite and pro-p limit groups

Abstract

We study homological approximations of the profinite completion of a limit group (see Thm. A) and obtain the analogous of Bridson and Howie’s Theorem for the profinite completion of a non-abelian limit group (see Thm. B).     

3-Rewritable Nilpotent 2-Groups of Class 2#

ABSTRACT

Let n be an integer greater than 1. A group G is said to be n-rewritable (or a Q_n-group) if for every n elements x₁, x₂,…,x_n in G there exist distinct permutations σ and τ in S_n such that x_σ(1)x_{σ (2)} ??? x_σ(n) = x_τ(1)x_τ(2) ??? x_τ(n). In this paper, we characterize all 3-rewritable nilpotent 2-groups of class 2. Also we have found a bound for the nilpotency class of certain nilpotent 3-rewritable groups, and have shown that 3-rewritable groups satisfy a certain law.     

具有弱$s$-置换嵌入子群的有限群

Let P be a Sylow p-subgroup of a group G with the smallest generator number d,where p is a prime.Denote by M_d(P) = {P_1,P_(2,...,)P_d} a set of maximal subgroups of P such that φ(P) = ∩_(n=1)~dP_n.In this paper,we investigate the structure of a finite group G under the assumption that the maximal subgroups in M_d(P) are weakly s-permutably embedded in G,some interesting results are obtained which generalize some recent results.Finally,we give some further results in terms of weakly s-permutably embedded subgroups.     

On Finite Groups with Few Automorphism Orbits

Denote by ω(G) the number of orbits of the action of Aut(G) on the finite group G. We prove that if G is a finite nonsolvable group in which ω(G) ≤5, then G is isomorphic to one of the groups A₅, A₆, PSL(2, 7), or PSL(2, 8). We also consider the case when ω(G) = 6 and show that, if G is a nonsolvable finite group with ω(G) = 6, then either G ≈ PSL(3, 4) or there exists a characteristic elementary abelian 2-subgroup N of G such that G/N ≈ A₅.     

置换性很好的一类群

主要研究子群置换性质对有限群结构的影响.通过子群的置换性得到一类群,即B 群.B群是全可置换群的扩展,利用全可置换群的p次中心扩张和子群的阶得到B群的一些性质并对B 群的结构进行一些刻画.应用B 群的结构得到有限p （p〉2）群为二元生成的B 群的充要条件.     

Automorphisms of Hyperbolic Groups and Graphs of Groups

Using the canonical JSJ splitting, we describe the outer automorphism group Out(G) of a one-ended word hyperbolic group G. In particular, we discuss to what extent Out(G) is virtually a direct product of mapping class groups and a free abelian group, and we determine for which groups Out(G) is infinite. We also show that there are only finitely many conjugacy classes of torsion elements in Out(G), for G any torsion-free hyperbolic group. More generally, let Γ be a finite graph of groups decomposition of an arbitrary group G such that edge groups G_e are rigid (i.e. Out(G_e) is finite). We describe the group of automorphisms of G preserving Γ, by comparing it to direct products of suitably defined mapping class groups of vertex groups.