关于4p阶3度Cayley图的正规性的一点注记

群G的Cayley图Cay(G,S)称为是正规的,如果G的右正则表示R(G)在Cay(G,S)的全自同构群中正规.设p为奇素数,相关文献决定了4p阶连通3度Cayley图的正规性.本文给出了上述文献的主要结果的一个新的简短的证明.     

2pq阶Cayley图是Hamilton图

一、引言对Cayley图的Hamilton性的研究近几年有所突破[1]现最好的结果是[2]的主要定理:若群G上的换位子群C′是p~n(p是素数,n是正整数)阶循环群时,G上的每个Cayley图皆为Hamilton图。1987年D.Marusic还证明了2p~2(p是素数)阶Cayley图为Hamilton图[4]。本文用群的构造理论证明:2pq(p,q是素数)阶Cayley图是Hamilton图。本文中所提到的群G皆指有限群;群的有关术语和记号同于文献[3];图的有关术     

4p阶二面体群的弱3-CI性

决定了4p(p是奇素数)阶二面体群的连通3度Cayley图的完全分类,并证明4p阶二面体群不是弱3-CI群,从而否定了C.H.Li关于"所有有限群都是弱3-CI群"的猜想     

一类16p阶群的三度Cayley图的正规性

有限群G的一个Cayley图X=Cay(G,S)称为正规的,如果右乘变换群R(G)在AutX中正规.研究了一类16p阶群G=〈a,b|a^(8p)=b(8p)=b²=1,a2=1,a^b=ab=a^(4p-1)〉的3度无向连通Cayley图的正规性,其中p为奇素数,并得到该群的正规与非正规的Cayley图     

4p阶二面体群连通3度Cayley有向图的正规性

设G是一个有限群,S是G的不包含单位元1的非空子集,定义群G关于S的Cayley(有向)图X:=Cay(G,S)如下:V(X)=G,E(X)={(g,sg)|g∈G,s∈S}.Cayley(有向)图X:=Cay(G,S)称为正规的,如果G的右正则表示R(G)在X的自同构群Aut(X)中是正规的.设G是4p阶二面体群(p为素数).考察了Cay(G,S)连通3度的正规性,并给出了这些图的全自同构群.     

2p2阶3度点传递图

一个图称为点传递图,如果它的全自同构群在它的顶点集合上作用传递.本文证明了一个2p～2（p为素数）阶连通3度点传递图或者是Calyley图,或者同构于广义Petersen图P（p～2,t）,这里t～2≡-1（modp～2）.     

六点图中的根式不可解图

本文对六点图进行了研究,文献[2]中已经证明了具有根式不可解的特征多项式的最小图是六点图.本文将确定六点图中所有根式不可解图.为了证明这一结果,我们只需要[2]中简单而为大家熟知的工具.定理1 设G是有限群,且|G|=p~3q~t,其中p,q为素数(p,q)=1,则G是可解群.证明见[1]第Ⅱ章§7定理2(p.236).引理1 群PGL_2(5)及PSL_2(5)不可解.     

4p阶3度点传递图

一个图称为点传递图,如果它的全自同构群在它的顶点集合上作用传递.证明了一个4p(p为素数)阶连通3度点传递图或者是Cayley图,或者同构于下列之一;广义Petersen图P(10,2),正十二面体,Coxeter图,或广义Petersen图P(2p,k),这里k2≡-1(mod 2p).     

4p阶三度点传递图

一个图称为点传递图或对称图如果它的自同构群分别在点集或点集有序对上传递.设P为素数,给出了4p阶连通三度点传递图分类(徐明曜等在[Chin.Ann.Math.,2004,25B(4):545-554]中分类了4p阶连通三度对称图).确定了4p阶互不同构的连通三度点传递图的个数f(4p);当P=2,3,5,7时,f(4p)分别为2,4,8,6;当P≥11且4|(p-1)时,f(4p)=5+p-3/2,当P≥11且4|(p-1)时,f(4p)=3+p-3/2.     

L7（3）与GL7（3）的OD-刻画

对于任意一个有限群G,令π（G）表示由它的阶的所有素因子构成的集合.构建一种与之相关的简单图,称之为素图,记作Γ（G）.该图的顶点集合是π（G）,图中两顶点p,g相连（记作p～q）的充要条件是群G恰有pq阶元.设π（G）={P₁,p2,…,p_x}.对于任意给定的p∈π（G）,令deg（p）:=|{q∈π（G）|在素图Γ（G）中,p～q}|,并称之为顶点p的度数.同时,定义D（G）:=（deg（p₁）,deg（p₂）,…,deg（p_s））,其中p₁2<…相似文献   

The unique trace property of <Emphasis Type="Italic">n</Emphasis>-periodic product of groups

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The Loop Shortening Property and Almost Convexity

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On the WGSC Property in Some Classes of Groups

The property of quasi-simple filtration (or qsf) for groups has been introduced in literature more than 10 years ago by S. Brick. This is equivalent, for groups, to the weak geometric simple connectivity (or wgsc). The main interest of these notions is that there is still not known whether all finitely presented groups are wgsc (qsf) or not. The present note deals with the wgsc property for solvable groups and generalized FC-groups. Moreover, a relation between the almost-convexity condition and the Tucker property, which is related to the wgsc property, has been considered for 3-manifold groups.     

Unions of dihedral groups

By the following simple formula (1) $$\forall x \exists y (x = xyy, y = xyx)$$ We characterize semigroups from the title. Considering a local property of their ?-classes we get bands and Boolean groups as extreme cases of semigroups with that property. We also provide a construction showing that ?-classes can be sufficiently complicated (at least as Abelian groups are). Then we permute right-hand sides of identities in (1) getting Boolean semigroups (x³=x) and so-called anti-inverse semigroups. Finally we show that Boolean semigroups are a proper subclass of the intersection of anti-inverse semigroups and unions of dihedral groups.     

Congruence Veech groups

We study Veech groups of covering surfaces of primitive translation surfaces. Therefore we define congruence subgroups in Veech groups of primitive translation surfaces using their action on the homology with entries in Z/aZ. We introduce a congruence level definition and a property of a primitive translation surface which we call property (★). It guarantees that partition stabilising congruence subgroups of this level occur as Veech groups of a translation covering.     

Idempotent reducts of abelian groups

In this paper we construct two maps between the polynomials of abelian groups and the polynomials of idempotent reducts of abelian groups and show that these can be used to “lift” the finite basis property from abelian groups to their idenpotent reducts. It follows that this equational class of all idempotent reducts of abelian groups has the finite basis property. The research of this author was supported by a grant from the National Research Council of Canada. Presented by J. Mycielski     

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The property of Dunford-Pettis for a locally convex space was introduced by Grothendieck in 1953. Since then it has been intensively studied, with especial emphasis in the framework of Banach space theory.

In this paper we define the Bohr sequential continuity property (BSCP) for a topological Abelian group. This notion could be the analogue to the Dunford-Pettis property in the context of groups. We have picked this name because the Bohr topology of the group and of the dual group plays an important role in the definition. We relate the BSCP with the Schur property, which also admits a natural formulation for Abelian topological groups, and we prove that they are equivalent within the class of separable metrizable locally quasi-convex groups.

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