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.     

自同构群

设Ｇ是有限群，ＡｕｔＧ＝ＡＢ，Ｂ△ＡｕｔＧ，（｜Ａ｜，｜Ｂ｜）＝１，Ａ是交换群且每Ｓｙｏｗ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≤的交换群时，Ｇ循环。     

一类交换群的自同构群

本利用一种新方法,考虑交换群Cp2XCp的自同构群,得到了该自同构群的结构．我们的结论是;     

某些有限群的自同构群

令G是一个奇阶群。本文证明了:当G具有小阶时,G不能作为一个有限群的全自同构群。     

某些有限群的自同构群

证明了: 若n是大于1的奇数, 使得对任意素数p都有p⁴æn, 则不存在有限群G, 使得|Aut(G)| = n.     

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。     

一类交换群的自同构群

本文利用一种新方法,考虑交换群Cp2×Cp 的自同构群,得到了该自同构群的结构.我们的结论是:Aut(Cp2×Cp)[Cp- 1∝(Cp×Cp)]holCp.     

一类不能作为自同构群的奇阶群

本文考虑如下问题：怎样的有限群可以作为另一个有限群的全自同构群？我们首先证明，若有限群Ｋ有一个正规Ｓｙｌｏｗｐ－子群使得｜Ｋ：Ｚ（Ｋ）｜ｐ＝ｐ２，那么Ｋ有２阶自同构．利用这个结果，我们证明了，若奇阶群Ｇ具有阶Ｐｓｍ（１≤ｓ≤３），ｐ为｜Ｇ｜的最小素因子，ｐｍ，ｍ无立方因子，则Ｇ不可能作为全自同构群．     

有限ATI-群的类保持Coleman自同构

设G是一个有限群,对G的任意阿贝尔子群A及任意g∈G,若A∩A~g=1或A,则称G为一个ATI-群.本文证明了,对任意p∈τ(G),如果ATI-群G的一个p-方幂阶类保持自同构在G的任意Sylow子群上的限制等于G的某个内自同构的限制,则它必定是一个内自同构.作为该结果的一个直接推论,我们也证明了有限ATI-群G有正规化性质.     

2pq阶群的自同构群

继续「１～２」等的工作,给出了２ｐｑ阶群Ｇ的自同构群ＡｕｔＧ的准确构造。     

The Fixed Point Group of a Free Group Automorphism

It is proved that the fixed point group of an arbitrary automorphism of a free group of finite rank has an algorithmically computable basis.     

The Automorphism Tower of a Free Group

It is proved that the automorphism group of any non-abelianfree group F is complete. The key technical step in the proofis that the set of all conjugations by powers of primitive elementsis first-order parameter-free definable in the group Aut(F).     

The Automorphism Group of a Free-by-Cyclic Group in Rank 2

Let φ be an automorphism of a free group F_n of rank n, and let M_φ = F_n ?_φ ? be the corresponding mapping torus of φ. We study the group Out(M_φ) under certain technical conditions on φ. Moreover, in the case of rank 2, we classify the cases when this group is finite or virtually cyclic, depending on the conjugacy class of the image of φ in GL₂(?). As an application, we solve the isomorphism problem for the family of F₂-by-? groups, in terms of the two defining automorphisms.     

Structure of a Conjugating Automorphism Group

We examine the automorphism group Aut(F _n ) of a free group F _n of rank n 2 on free generators x ₁, x ₂,...,x _n . It is known that Aut(F ₂) can be built from cyclic subgroups using a free and semidirect product. A question remains open as to whether this result can be extended to the case n > 2. Every automorphism of Aut(F _n ) sending a generator x _i to an element f _i ^-1 x _(i) f _i , where f _i F _n and is some permutation on a symmetric group S _n , is called a conjugating automorphism. The conjugating automorphism group is denoted C _n . A set of automorphisms for which is the identity permutation form a basis-conjugating automorphism group, denoted Cb _n . It is proved that Cb _n can be factored into a semidirect product of some groups. As a consequence we obtain a normal form for words in C _n . For n 4, C _n and Cb _n have an undecidable occurrence problem in finitely generated subgroups. It is also shown that C _n , n 2, is generated by at most four elements, and we find its respective genetic code, and that Cb _n , n 2, has no proper verbal subgroups of finite width.     

广义超特殊p-群的自同构群Ⅲ

确定了广义超特殊p-群G的自同构群的结构.设|G|=p~(2n+m),|■G|=p~m,其中n≥1,m≥2,Aut_fG是AutG中平凡地作用在Frat G上的元素形成的正规子群,则(1)当G的幂指数是p~m时,(i)如果p是奇素数,那么AutG/AutfG≌Z_((p-1)p~(m-2)),并且AutfG/InnG≌Sp(2n,p)×Zp.(ii)如果p=2,那么AutG=Aut_fG(若m=2)或者AutG/AutfG≌Z_(2~(m-3))×Z_2(若m≥3),并且AutfG/InnG≌Sp(2n,2)×Z_2.(2)当G的幂指数是p~(m+1)时,(i)如果p是奇素数,那么AutG=〈θ〉■Aut_fG,其中θ的阶是(p-1)p~(m-1),且Aut_f G/Inn G≌K■Sp(2n-2,p),其中K是p~(2n-1)阶超特殊p-群.(ii)如果p=2,那么AutG=〈θ_1,θ_2〉■Aut_fG,其中〈θ_1,θ_2〉=〈θ_1〉×〈θ_2〉≌Z_(2~(m-2))×Z_2,并且Aut_fG/Inn G≌K×Sp(2n-2,2),其中K是2~(2n-1)阶初等Abel 2-群.特别地,当n=1时...     

The Structure of the (Outer) Automorphism Group of a Bieberbach Group

Referring to Tits alternative, we develop a necessary and sufficient condition to decide whether the normalizer of a finite group of integral matrices is polycyclic-by-finite or is containing a non-Abelian free group. This result is of fundamental importance to conclude whether the (outer) automorphism group of a Bieberbach group is polycyclic-by-finite or has a non-cyclic free subgroup.     

超特殊Z-群的自同构群

确定了超特殊Z-群的自同构群.设G是超特殊Z-群,即G={(1 α_1 α_2···α_n α_(n+1) 0 1 0···0 α_(n+2) ···0 0 0 ··· 0 α_2n 0 0 0··· 1 α_(2n+1) 0 0 0···1 α_(2n+1) 0 0 0···0 1)|α_j∈Z,j=1,2,3,...,2n+1}Aut_cG是AutG中平凡作用在ζG上的自同构形成的正规子群,则AutG=Aut_cG×Z_2,且1→Z···Z}2N→Aut_cG→Sp(2n,Z)→1是正合列.     

Linear Representations of the Automorphism Group of a Free Group

Let F _n be the free group on n ≥ 2 elements and Aut(F _n ) its group of automorphisms. In this paper we present a rich collection of linear representations of Aut(F _n ) arising through the action of finite-index subgroups of it on relation modules of finite quotient groups of F _n . We show (under certain conditions) that the images of our representations are arithmetic groups. Received: November 2006, Accepted: March 2007