一类多重循环群的同构刻画

设A是秩为n(n≥2)的自由Abel群,α是利用A直和分量上的循环置换与数乘构造的一个A的自同构.作A与α的半直积G=A×〈α〉,本文给出了这类多重循环群G的同构分类,以及它构成超可解群和幂零群的充要条件.     

一类无限的多重循环群

设Ｇ是无限的多重循环群，如果对Ｇ的每个有限商群Ｇ，Ｇ的所有Ａｂｅｌ子群都是３元生成的，那么Ｇ￣（７）＝１且Ｇ是４元生成的．     

关于多重循环群的两个结果

设Ｇ是个有限生成的超Ａｂｅｌ群,若Ｇ满足下列的条件之一： （ｉ） Ｇ的 ２一生成的子群都是多重循环群; （ｉｉ）Ｇ／Ｚ*（Ｇ）是多重循环群,Ｚ*（Ｇ）表示Ｇ的超中心（Ｈｙｐｅｒｃｅｎｔｒｅ）; （ｉｉｉ） Ｇ／△十（Ｇ）是多重循环群, △＋（Ｇ）表示 Ｇ的所有有限正规子群生成的子群,则Ｇ是个多重循环群．     

关于多重循环群的两个结果

设G是个有限生成的超Abel群,若G满足下列的条件之一(i)G的2一生成的子群都是多重循环群;(ii)G/Z     

多重循环群的一个注记

设A是秩为n的自由Abel群.熟知A的自同构群Aut(A)=GL(n,Z).设f(λ)=λⁿ+a_n-1λ^n-1+…+a₁λ+a₀∈Z[λ]是不可约多项式,其中a₀=±1.设T=<α>是无限循环群,α通过多项式f(λ)的Frobenius相伴矩阵诱导的自同构作用在A上.设G=A ■ T.我们证明G是剩余有限p-群当且仅当p整除f(1).     

一类亚循环群的自同构群

本文决定了每 Sylow子群循环的有限群 G的自同构群 ,所得结论包含了徐尚进和 Walls的主要结果 .     

剩余有限minimax可解群的自同构

设G是剩余有限minimax可解群,α是G的自同构且φ:G→G(g→[g,α])是满射,则有以下结果:(1)当α~p=1时,G是幂零类不超过h(p)的幂零群的有限扩张,其中h(p)是只与p有关的函数;(2)当α~4=1时,G存在一个指数有限的特征子群H,使得H″≤Z(H)和C_H(α~2)是Abel群.并且C_G(α~2)和G/[G,α~2]都是Abel群的有限扩张.     

剩余有限minimax 可解群的几乎正则自同构

设G 是一个剩余有限的minimax 可解群, α 是G 的几乎正则自同构, 则G/[G, α] 是有限群, 并且(1) 当α^p = 1 时, G 有一个指数有限的幂零群其幂零类不超过h(p), 其中h(p) 是只与素数p 有关的函数.(2) 当α² = 1 时, G 有一个指数有限的Abel 特征子群且[G, α]′ 是有限群.关键词剩余有限minimax 可解群几乎正则自同构     

自同构群是循环群被交换群扩张的有限群

设Ｃ是有限群，ＡｕｔＧ＝ＡＢ，，Ａ是交换群且每Ｓｙｌｏｗ子群的秩≤２，Ｂ是循环群，本文得出了Ｇ的结构，特别地，证明了ＡｕｔＧ是秩≤２的交换群时，Ｇ循环。     

On the Residual Finiteness of Outer Automorphisms of Hyperbolic Groups

We show that every virtually torsion-free subgroup of the outer automorphism group of a conjugacy separable hyperbolic group is residually finite. As a result, we are able to prove that the group of outer automorphisms of every finitely generated Fuchsian group and of every free-by-finite group is residually finite.     

不充当自同构群的有限群

设ｐ为奇素数，本文将用一些新的技巧来证明，当Ｐ是阶小于Ｐ＾１１的交换Ｐ－群时，自同构群方程Ａｕｔ（Ｘ）＝Ｐ无解。这个结果使ＭａｃｈＨａｌｅ在１９８３年的工作得到了突破，并且我们所给的方法具有广泛性。     

带有限性条件Abel群的自同态环和自同构群

给出了带极大或极小条件的Abel群A的自同构群以及自同态环的相伴Lie环是可解或幂零的充要条件.同时也给出了群A=Q_(π1)⊕Q_(π2)⊕…⊕Q_(πr)的自同构群是可解或幂零的充要条件,以及群A的自同态环的相伴Lie环是可解或幂零的充要条件.     

多重循环群的Fitting子群

本文给出了多重循环群的Ｆｉｔｉｎｇ子群的几条性质，所得结果深化了Ｍａｌｃｅｖ关于多重循环群的经典工作．     

On Residually Finite Groups with Engel-like Conditions

Let m, n be positive integers. Suppose that G is a residually finite group in which for every element x ∈ G there exists a positive integer q = q(x) ≤ m such that x^q is left n-Engel. We show that G is locally virtually nilpotent. Further, let w be a multilinear commutator and G a residually finite group in which for every product of at most 896 w-values x there exists a positive integer q = q(x) dividing m such that x^q is left n-Engel. Then w(G) is locally virtually nilpotent.     

On the Hopficity of HNN-Extensions of Polycyclic Groups

For a group G, an HNN-extension of polycyclic groups, we give two necessary and sufficient conditions for G to be hopfian. One is based on the nature of the endomorphism of G and the other on the nature of the associated subgroups of G. At the end, we give an application for HNN-extensions of nilpotent groups.     

On a Method of J. H. C. Whitehead

In this article which is partly a continuation of Goldstein (1999 Goldstein , R. Z. ( 1999 ). The length and thickness of words in a free group . Proc. Amer. Math. Soc. 127 ( 10 ): 2857 – 2863 . [CSA] [CROSSREF]  [Google Scholar]), we give some necessary and sufficient conditions for an element of a free group to be primitive. For certain words x, we also give a lower bound on the length of words obtained from x by an automorphism. In the last section we give another proof of the Primitivity Theorem recently proven by Lee, using ideas from the first part of the article.     

Polycyclic groups admitting a regular automorphism of order four

Let G be a polycyclic group and α a regular automorphism of order four of G. If the map φ: G→ G defined by g~φ= [g, α] is surjective, then the second derived group of G is contained in the centre of G. Abandoning the condition on surjectivity, we prove that C_G(α~2) and G/[G, α~2] are both abelian-by-finite.