Heguo Liu, Xingzhong Xu, Jiping Zhang
In this paper, we focus on a question of M. Newman on isomorphic subgroups of solvable groups. We get a reduction theorem of this question: for each prime q, assume that this question holds for every characteristic q-groups, then this question holds for every finite solvable groups. Using this reduction theorem, we get some partial answers about this question.
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M.Newman has asked if it is the case that whenever H and K are isomorphic subgroups of a finite solvable group G with H maximal, then K is also maximal. This question was considered in a paper of I.M. Isaacs and the second author, where (among other things) the answer was shown to be affirmative if H has an Abelian Sylow 2-subgroup. Here, we show that the answer is affirmative unless the index of H is a power of a prime less than 5 and we obtain further restrictions on the structure of a purported minimal counterexample.
Subrack lattices of finite solvable and metacyclic groups
本文研究有限群rack的子rack格，证明可解群的子rack格决定其可解性及导出长度，且拟循环群的子rack格决定其商群的拟循环性。
Assume that a finite almost simple group with simple socle isomorphic to an exceptional group of Lie type possesses a solvable Hall subgroup. Then there exist four conjugates of the subgroup such that their intersection is trivial.
It is shown that for a solvable subgroup $G$ of an almost simple group $S$ which socle is isomorphic to $A_n$ $ (n\ge5)$ there are $x,y,z,t \in S$ such that $G \cap G^x \cap G^y \cap G^z \cap G^t =1.$
We show that the abstract commensurator of an S-arithmetic subgroup of a solvable algebraic group over Q is isomorphic to the Q-points of an algebraic group, and compare this with examples of nonlinear abstract commensurators of S-arithmetic groups in positive characteristic. In particular, we include a description of the abstract commensurator of the lamplighter group.
We show that locally solvable subgroups of PLo(I) are countable. Then for each countable ordered set, we construct a locally solvable subgroup of Thompson's Group F. We develop machinery for understanding embeddings from solvable subgroups into solvable subgroups. Finally, we apply this machinery to show the ordered sets used in our construction are invariant under isomorphisms between the groups constructed. Therefore, we effectively distinguish the groups and provide uncountably many non-isomorphic locally solvable, hence elementary amenable, subgroups of Thompson's Group F.
We prove that for any natural n>1, the abstract commensurator group of the Baumslag - Solitar group BS(1,n) is isomorphic to the group of 2 by 2 upper triangular matrices A over rational numbers with A_{11}=1. We also prove that for any finitely generated group G with the unique root property the natural homomorphisms Aut(G)--> Comm(G)--> QI(G) are embeddings.
We compute the Bieri-Neumann-Strebel invariants $Σ^1$ for the generalized solvable Baumslag-Solitar groups $Γ_n$ and their finite index subgroups. Using $Σ^1$, we show that certain finite index subgroups of $Γ_n$ cannot be isomorphic to $Γ_{k}$ for any $k$. In addition, we use the BNS-invariants to give a new proof of property $R_\infty$ for the groups $Γ_n$ and their finite index subgroups.
Computing canonical labellings of finite solvable groups
提出一种有限可解群的标准标记函数，通过群表示实现同构判定，并利用群上同调与自同构群算法，在GAP中实现概念验证。
Let $G$ be a group and $Sol(G)=\{x \in G : \langle x,y \rangle \text{ is solvable for all } y \in G\}$. We associate a graph $\mathcal{NS}_G$ (called the non-solvable graph of $G$) with $G$ whose vertex set is $G \setminus Sol(G)$ and two distinct vertices are adjacent if they generate a non-solvable subgroup. In this paper we study many properties of $\mathcal{NS}_G$. In particular, we obtain results on vertex degree, cardinality of vertex degree set, graph realization, domination number, vertex connectivity, independence number and clique number of $\mathcal{NS}_G$. We also consider two grou…
We give a new proof that compact infra-solvmanifolds with isomorphic fundamental groups are smoothly diffeomorphic. More generally, we prove rigidity results for manifolds which are constructed using affine actions of virtually polycyclic groups on solvable Lie groups. Our results are derived from rigidity properties of subgroups in solvable linear algebraic groups.
Let π(G) denote the set of prime divisors of the order of a finite group G. The prime graph of G is the graph with vertex set π(G) with edges {p,q} if and only if there exists an element of order pq in G. In this paper, we prove that a graph is isomorphic to the prime graph of a solvable group if and only if its complement is 3-colorable and triangle free. We then introduce the idea of a minimal prime graph. We prove that there exists an infinite class of solvable groups whose prime graphs are minimal. We prove the 3k-conjecture on prime divisors in element orders for solvable groups with mini…
We consider the following problem stated by Vdovin (2010) in the "Kourovka notebook" (Problem 17.41): Let $H$ be a solvable subgroup of a finite group $G$ that has no nontrivial solvable normal subgroups. Do there always exist five conjugates of $H$ whose intersection is trivial? This problem is closely related to a conjecture by Babai, Goodman and Pyber (1997) about an upper bound for the index of a normal solvable subgroup in a finite group. In particular, a positive answer to Vdovin's problem yields that if $G$ has a solvable subgroup of index $n$, then it has a solvable normal subgroup of …
Cohomology of solvable saturable pro-$p$ groups and Lie algebras
本文研究可解饱和 pro-$p$ 群及其相伴 $\Z_p$-李代数的模 $p$ 上同调，证明二者在各阶作为 $\F_p$-向量空间同构，并建立李代数与其模 $p$ 约化间的相应同构。
Cameron, Manna and Mehatari investigated the question of which finite groups admit a power graph that is a cograph, also called power-cograph groups (Journal of Algebra 591 (2022)). They give a classification for nilpotent groups and partial results for general groups. However, the authors point out number theoretic obstacles towards a classification. These arise when the groups are assumed to be isomorphic to PSL 2 (q) or Sz(q) and are likely to be hard. In this paper, we prove that these number theoretic problems are in fact the only obstacles to the classification of non-solvable power-cogr…
Solvable Supplements to Normalizers of Cyclic 2-Subgroups
本文放宽了可解补充条件至仅对循环2-子群成立，刻画了满足该条件的有限群的非交换合成因子为特定PSL2(q)族，并给出可解性的充要条件。
Bouc proposed the following conjecture: a finite group $G$ is nilpotent if and only if its largest quotient $B$-group $β(G)$ is nilpotent. And he has prove that this conjecture holds when $G$ is solvable. In this paper, we consider the case when $G$ is not solvable. Let $S$ be a nonabelian simple group except the Chevalley groups $A_{n}(q)$, $D_{n}(q)$, $E_{6}(q)$, and $^2A_{n}(q)$, if there exists only one factor of $G$ which is isomorphic to $S$, then $β(G)$ is not solvable, of course, is not nilpotent. That means we prove the conjecture in these cases.
Some elementary amenable subgroups of interval exchange transformations
本文研究了区间交换变换中某些初等可容许子群的性质，探讨了其非虚拟可解性和可解性条件，并展示了无限多个非线性且非虚拟可解的群以及可解群的导出长度。
Realizing Gruenberg-Kegel graphs of $T$-solvable groups with structurally simplified extensions of $T$
本文研究了T-可解群的素数图补集，证明其可由可解群和准简单T-可解群作用于元素阿贝尔群的直积实现，并探讨了PSL(2,13)-可解群的素数图补集分类。
Let BS(1,n)= < a,b: aba^{-1}=b^n >. We prove that any finitely-generated group quasi-isometric to BS(1,n) is (up to finite groups) isomorphic to BS(1,n). We also show that any uniform group of quasisimilarities of the real line is bilipschitz conjugate to an affine group.
Parabolic subgroups and word problem in virtual Artin groups
本文研究了虚拟Artin群中标准抛物面子群的字问题，证明了在特定条件下虚拟Artin群具有可解的字问题，并探讨了强成员问题的可解性。
Base sizes for finite linear groups with solvable stabilisers
本文针对点稳定子可解、可解根基平凡的传递置换群的基大小猜想，证明了基柱同构于PSL_n(q)的殆单群情形下该猜想的强形式，其余典型群将在后续论文处理。
Let $G$ be a finite group and ${\rm cd}(G)$ denote the set of complex irreducible character degrees of $G$. In this paper, we prove that if $G$ is a finite group and $H$ is an almost simple group with socle $H_{0}= \, ^{2}{\rm G}_{2}(q)$, where $q=3^{f}$ with $f\geq 3$ odd such that ${\rm cd}(G)={\rm cd}(H)$, then $G$ is non-solvable and the chief factor $G'/M$ of $G$ is isomorphic to $H_{0}$. If, in particular, $f$ is coprime to $3$, then $G'$ is isomorphic to $H_{0}$ and $G/{\bf Z}(G)$ is isomorphic to $H$.
We prove that any finitely generated torsion free solvable subgroup of the group ${\rm IET}$ of all Interval Exchange Transformations is virtually abelian. In contrast, the lamplighter groups $A\wr \mathbb{Z}^k$ embed in ${\rm IET}$ for every finite abelian group $A$, and we construct uncountably many non pairwise isomorphic 3-step solvable subgroups of ${\rm IET}$ as semi-direct products of a lamplighter group with an abelian group. We also prove that for every non-abelian finite group $F$, the group $F\wr \mathbb{Z}^k$ does not embed in ${\rm IET}$.
Let $G$ be a finite group. Denoting by ${\rm{cd}}(G)$ the set of the degrees of the irreducible complex characters of $G$, we consider the {\it character degree graph} of $G$: this is the (simple, undirected) graph whose vertices are the prime divisors of the numbers in ${\rm{cd}}(G)$, and two distinct vertices $p$, $q$ are adjacent if and only if $pq$ divides some number in ${\rm{cd}}(G)$. This paper completes the classification, started in [5] and [6], of the finite non-solvable groups whose character degree graph has a {\it cut-vertex}, i.e. a vertex whose removal increases the number of co…
Let $G$ be a finite group, and let ${\rm{cd}}(G)$ denote the set of degrees of the irreducible complex characters of $G$. Define then the character degree graph $Δ(G)$ as the (simple undirected) graph whose vertices are the prime divisors of the numbers in ${\rm{cd}}(G)$, and two distinct vertices $p$, $q$ are adjacent if and only if $pq$ divides some number in ${\rm{cd}}(G)$. This paper continues the work, started in [7], toward the classification of the finite non-solvable groups whose degree graph possesses a cut-vertex, i.e., a vertex whose removal increases the number of connected compone…
Nilpotent groups, solvable groups and factorizable inverse monoids
本文引入逆半群中的次中心与中心幂等元序列，证明了可因子化逆幺半群中此类序列的同构性（类比Jordan-Hölder定理），并据此定义了G-幂零与G-可解逆幺半群，为研究幂零群和可解群提供了新途径。
New classes of IYB groups
该研究通过证明两类满足西罗子群幂零类约束的有限群为IYB群，推广了已有结论，还得到两类有限群同构于幂零型斜左brace乘法群的结果，推进了IYB群的公开问题研究。
It has been known since \cite{Pgroupchunk} that any group definable in an $o$-minimal expansion of the real field can be equipped with a Lie group structure. It is therefore natural to ask when is a Lie group Lie isomorphic to a group definable in such an expansion. Conversano, Starchenko and the first author answered this question in \cite{COSsolvable} in the case when the group is solvable. This paper answers similar questions in more general contexts. We first give a complete classification in the case when the group is linear. Specifically, a linear Lie group $G$ is Lie isomorphic to a gro…
Assume $G$ is a solvable group whose elementary abelian sections are all finite. Suppose, further, that $p$ is a prime such that $G$ fails to contain any subgroups isomorphic to $C_{p^\infty}$. We show that if $G$ is nilpotent, then the pro-$p$ completion map $G\to \hat{G}_p$ induces an isomorphism $H^\ast(\hat{G}_p,M)\to H^\ast(G,M)$ for any discrete $\hat{G}_p$-module $M$ of finite $p$-power order. For the general case, we prove that $G$ contains a normal subgroup $N$ of finite index such that the map $H^\ast(\hat{N}_p,M)\to H^\ast(N,M)$ is an isomorphism for any discrete $\hat{N}_p$-module …
Polynomial-time isomorphism test for solvable groups with abelian Sylow subgroups
本文针对具有阿贝尔Sylow子群的群（A-群）提出多项式时间同构测试算法，推广了Babai和Qiao关于可解群的结果，并利用了其计算方法和A-群的结构性质。
Prime Graphs of Locally Torsion Ultragroups, Metanilpotent Groups, and $T$-Solvable Groups
本文利用模型论工具，继续分类$T$-可解局部挠群和局部挠亚幂零群的素图，并分类具有特定一阶性质的超群的素图，同时证明实现给定素图的群类数量与类型的结果。
We investigate subgroups of the group PLo(I) of piecewise-linear, orientation-preserving homeomorphisms of the unit interval with finitely many breaks in slope, under the operation of composition, and also subgroups of the generalized Thompson groups F_n. We find geometric criteria determining the derived length of any such group, and use this criteria to produce a geometric classification of the solvable and non-solvable subgroups of PLo(I) and of the F_n. We also show that any standard restricted wreath product C wr T (of non-trivial groups) that embeds in PLo(I) or F_n must have T isomorphi…
Motivated by quotient algorithms, such as the well-known $p$-quotient or solvable quotient algorithms, we describe how to compute extensions $\tilde H$ of a finite group $H$ by a direct sum of isomorphic simple $\mathbb{Z}_p H$-modules such that $H$ and $\tilde H$ have the same number of generators. Similar to other quotient algorithms, our description will be via a suitable covering group of $H$. Defining this covering group requires a study of the representation module, as introduced by Gaschütz in 1954. Our investigation involves so-called Fox derivatives (coming from free differential calc…
Solvable Automorphism Groups of Varieties
研究证明，当变种X为准仿射时，由包含单位的不可约族生成的可解子群为代数子群，且连通可解子群导出长度不超过n+1，X同构于仿射空间且Borel子群与Jonquières子群共轭。
We investigate subgroups of the group PLo(I) of piecewise-linear, orientation preserving homeomorphisms of the unit interval with finitely many breaks in slope, and also subgroups of Thompson's group F. We find geometric criteria determining the derived length of any such group, and use this criteria to classify the solvable and non-solvable subgroups of PLo(I) and of F. Let H be a subgroup of PL_o(I) or F. We find that H is solvable if and only if H is isomorphic to a group in a well described class R of groups. We also find that H is non-solvable if and only if we can embed a copy of a speci…
Automorphisms and monomorphisms of direct products of virtually solvable minimax groups
本文研究了有限生成近可解极小极大群直积的自同构与单射映射性质，证明了在特定条件下，每个单射映射可唯一分解为θ·ζ形式，其中θ将每个因子映射到排列后的因子，并且ζ是中心且非对角的。
Prime Graphs of Infinite Groups
本文定义无限群的素图，并将有限可解及T-可解群的素图结果推广至相应无限群类别。
Supersolvable subgroups of order divisible by 3
本文确定了所有阶被3整除的极大子群均超可解的有限非可解群的结构，证明其要么是3'-群，要么商群同构于PSL_2(2^p)且满足特定幂零性条件。
We show that a finite group which admits a faithful, smooth, orientation-preserving action on a homology 4-sphere, and in particular on the 4-sphere, is isomorphic to a subgroup of the orthogonal group SO(5), by explicitly determining the various groups which can occur (up to an indetermination of index two in the case of solvable groups). As a consequence we obtain also a characterization of the finite groups which are isomorphic to subgroups of the orthogonal groups SO(5) and O(5).
Criteria for Classifying Prime Graphs of PSL(2, q)-Solvable Groups
本文为PSL(2,q)-可解群提供素图分类准则，并首次对T属于大（可能无限）群族PSL(2,2^f)的T-可解群证明一般分类结果。
Rigidity and flexibility results for groups with a common cocompact envelope
该文研究具有公共余紧包络的有限生成群的共有性质，在完全不连通包络、有限秩可解群等情形下建立了刚性与柔性结果，证明有限秩可解群类非QI刚性，还展示了$F_n$型群的柔性行为。
Cosets of normal subgroups and union of two conjugacy classes
研究有限群正规子群陪集包含于两个共轭类并集的条件，证明此时 $N$ 不必可解但结构受限，其非交换主因子同构于奇特征 Lie 型单群的直积。
Classifying prime graphs of finite groups -- a methodical approach
本文建立任意T-可解群素图边存在性的一般理论，并对阶含4个素因子的绝大多数T分类了T-可解群的素图，发现其补图几乎均为3-可着色且含少量三角形。
Classification of the Prime Graphs of $\operatorname{Sz}(8)$-, $\operatorname{Sz}(32)$-, and $\operatorname{PSL}(2, 2^5)$-Solvable Groups
本文针对非循环合成因子为$\operatorname{Sz}(8)$、$\operatorname{Sz}(32)$或$\operatorname{PSL}(2,2^5)$的群，利用 Brauer 特征标表完成其素图分类，填补了此前最困难的遗留情形。
Let $ G $ be a finite non-solvable group with a primitive irreducible character $ χ$ that vanishes on one conjugacy class. We show that $ G $ has a homomorphic image that is either almost simple or a Frobenius group. We also classify such groups $ G $ with a composition factor isomorphic to a sporadic group, an alternating group $ \rm{A}_{n} $, $ n\geq 5 $ or $ \rm{PSL}_{2}(q) $, where $ q\geq 4 $ is a prime power, when $ χ$ is faithful. Our results partially answer a question of Dixon and Rahnamai Barghi.
Finite groups with conjugacy classes of size $2p^n$
该研究推广了Burnside $p^a$定理，证明非阿贝尔有限单群无大小为$2p^n$的共轭类，并推广Kazarin结果，明确有限群中特定大小共轭类生成子群的可解性及非可解时的结构。
Giving a condition for the the amenability of groups, Rosenblatt and Willis, first introduced the concept of configuration. From the beginning of the theory, the question whether the concept of configuration equivalence coincides with the concept of group isomorphism was posed. We negatively answer this open question by introducing two non-isomorphic, solvable and hence amenable groups which are configuration equivalent. Also, we will study some types of subgroups in configuration equivalent groups. In particular, we will prove this conjecture, due to Rosenblatt and Willis, that configuration …
We study the Diophantine problem (decidability of finite systems of equations) in different classes of finitely generated solvable groups (nilpotent, polycyclic, metabelian, free solvable, etc), which satisfy some natural "non-commutativity" conditions. For each group $G$ in one of these classes, we prove that there exists a ring of algebraic integers $O$ that is interpretable in $G$ by finite systems of equations (e-interpretable), and hence that the Diophantine problem in $O$ is polynomial time reducible to the Diophantine problem in $G$. One of the major open conjectures in number theory st…
p-Nilpotent maximal subgroups in finite groups
该研究针对每个极大子群要么p-幂零要么有素指数的有限群，证明其仅可涉入PSL_n(q)族中一种阶被p整除的非交换单群，且p=2时该单群必为特定参数的PSL_2(r^a)。
Ideals and Solvability in Skew Braces
研究有限斜括号乘法群幂零性对其理想结构和可解性的影响，证明相关结论，探讨双边斜括号可解性，得出有限双边斜括号可解性与加或乘法群可解性的关系及无限情况下的相关结论。
Let $M\stackrel{ρ_0}{\curvearrowleft}S$ be a $C^\infty$ locally free action of a connected simply connected solvable Lie group $S$ on a closed manifold $M$. Roughly speaking, $ρ_0$ is parameter rigid if any $C^\infty$ locally free action of $S$ on $M$ having the same orbits as $ρ_0$ is $C^\infty$ conjugate to $ρ_0$. In this paper we prove two types of result on parameter rigidity. First let $G$ be a connected semisimple Lie group with finite center of real rank at least $2$ without compact factors nor simple factors locally isomorphic to $\mathrm{SO}_0(n,1)$ $(n\geq2)$ or $\mathrm{SU}(n,1)$ $(…
On finite groups whose power graph is claw-free
本文探讨了简化幂图无爪的有限群，证明了此类群要么是可解群要么是基座同构于 $PSL(2,q)$ 的几乎单群，且其阶最多被 5 个不同素数整除。
Finite groups in which some particular non-nilpotent maximal invariant subgroups have indices a prime-power
本文研究互素自同构群作用下有限群的结构，证明在特定极大不变子群为同构单群直积、且不含某正规子群的非幂零极大不变子群均具素数幂指数且排除PSL_2(7)作为合成因子的条件下，该群必可解。
A Cayley graph of a group $H$ is a finite simple graph $Γ$ such that ${\rm Aut}(Γ)$ contains a subgroup isomorphic to $H$ acting regularly on $V(Γ)$, while a Haar graph of $H$ is a finite simple bipartite graph $Σ$ such that ${\rm Aut}(Σ)$ contains a subgroup isomorphic to $H$ acting semiregularly on $V(Σ)$ and the $H$-orbits are equal to the bipartite sets of $Σ$. A Cayley graph is a Haar graph exactly when it is bipartite, but no simple condition is known for a Haar graph to be a Cayley graph. In this paper, we show that the groups $D_6, \, D_8, \, D_{10}$ and $Q_8$ are the only finite inner…
A fast algorithm for Stallings foldings over virtually free groups
本研究提出一种求解虚自由群子群成员问题的快速算法，时间复杂度接近线性，可用于矩阵群计算，还能判定有限生成子群是否同构于自由群。
Let $G$ be a simply connected solvable Lie group with a lattice $Γ$ and $N$ the nilradical of $G$. For a complex valued representation $ρ: G\to GL(V_ρ)$ such that the restriction $ρ_{|_{N}}$ is unipotent, as an advanced variation of cohomology computation of solvmanifolds by using Lie algebra cohomology, we construct a explicit finite dimensional cochain complex whose cohomology is isomorphic to the cohomology of $G/Γ$ with twisted by $ρ$.
The integral Burau representation provides a map from the braid group into a group of integral matrices. This allows for a definition of congruence subgroups of the braid group as the preimage of the usual principal congruence subgroups of integral matrices. We explore the structure these congruence subgroups by examining some of the quotients that may arise in the series induced by divisibility of levels. We build on the work of Stylianakis on symmetric quotients of congruence subgroups, which itself generalizes the quotient of the braid group by the pure braid group. We accomplish this by ut…
On weak commutativity between $n$ isomorphic groups, $n \geq 2$
本文针对 $n$ 个同构群之间的弱交换性，引入 $n$ 元弱交换群 $\chi_n(H)$，研究其与迭代算子 $\chi^n(H)$ 的混合商群，确定 $n=2$ 时的最大公共商，并证明相关群类保持有限性、幂零性和完全性。
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