Jacques Thévenaz
We determine all maximal subgroups of the direct product $\sc G^n$ of $\sc n$ copies of a group~$\sc G$. If $\sc G$ is finite, we show that the number of maximal subgroups of~$\sc G^n$ is a quadratic function of~$\sc n$ if $\sc G$ is perfect, but grows exponentially otherwise. We~deduce a theorem of Wiegold about the growth behaviour of the number of generators of~$\sc G^n$.
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We give a description of a finite group whose maximal subgroups possess only soluble proper subgroups, which implies the answer to the well-known question on composition factors of finite groups, whose second maximal subgroups are soluble.
Finite groups in which every cyclic subgroup is the intersection of maximal subgroups
本文刻画了每个循环子群均为极大子群交集的有限群的结构，并与所有真子群均为极大子群交集的性质进行对比。
On second maximal subgroups of finite groups
该研究定义了有限群的次极大子群，证明有限群素指数子群的每个极大子群均为次极大子群，丰富了有限群结构理论相关结论。
In this paper, we investigate the difference between weak second maximal subgroups and second maximal subgroups. A sufficient and necessary condition is also given to describe such class of groups whose weak second maximal subgroups coincide with its second maximal subgroups(called WSM-groups) under the solvable case. As an application, we show that every non-vanishing element of a solvable WSM-group lies in its Fitting subgroup.
In this paper, we study a group in which every 2-maximal subgroup is a Hall subgroup.
Finite groups with some particular maximal invariant subgroups being nilpotent or all non-nilpotent maximal invariant subgroups being normal
本文分类了在互素自同构群作用下、含某不变 Sylow 子群正规化子的极大不变子群均为幂零的有限群，并证明该条件等价于所有非幂零极大不变子群均正规。
On a finite group in which every non-supersolvable maximal subgroup is a TI-subgroup
该研究刻画了一类每个非超可解极大子群均为TI子群的有限群，其成果推广了部分相关已知结论。
We describe finite soluble groups in which every $n$-maximal subgroup is $\mathfrak F$-subnormal.
We prove the following results: (1) Every group is a maximal subgroup of some free idempotent generated semigroup. (2) Every finitely presented group is a maximal subgroup of some free idempotent generated semigroup arising from a finite semigroup. (3) Every group is a maximal subgroup of some free regular idempotent generated semigroup. (4) Every finite group is a maximal subgroup of some free regular idempotent generated semigroup arising from a finite regular semigroup.
We conclude from the results of Hanguang Meng and Xiuyun Guo some corollaries about the existence of strictly 2-maximal subgroups in groups. We give examples of groups that illustrate properties of strictly 2-maximal subgroups.
A classification of finite groups in which every 3-maximal subgroup is K-U-subnormal is given.
We establish the existence of maximal subgroups of various diferent natures in SL(n,Z). In particular, we prove that there are continuously many maximal subgroups, we provide a maximal subgroup whose action on the projective space has no dense orbits, and we produce a faithful primitive permutation representation of PSL(n,Z) which is not 2-transitive.
We determine the combinatorial and the ordinary depth of the maximal subgroups of the simple Ree groups, $R(q)$.
We classify closed abelian subgroups of the automorphism group of any compact classical simple Lie algebra whose centralizer has the same dimension as the dimension of the subgroup, and describe Weyl groups of maximal abelian subgroups.
The number of maximal abelian subgroups of a finite p-group is shown to be congruent to 1 modulo p.
A subgroup of a finite group G is said to be second maximal if it is maximal in every maximal subgroup of G that contains it. A question which has received considerable attention asks: can every positive integer occur as the number of the maximal subgroups that contain a given second maximal subgroup in some finite group G? Various reduction arguments are available except when G is almost simple. Following the classification of the finite simple groups, finite almost simple groups fall into three categories: alternating and symmetric groups, almost simple groups of Lie type, sporadic groups an…
Let $G$ be a finitely generated regular branch group acting by automorphisms on a regular rooted tree $T$. It is well-known that stabilizers of infinite rays in $T$ (aka parabolic subgroups) are weakly maximal subgroups in $G$, that is, maximal among subgroups of infinite index. We show that, given a finite subgroup $Q\leq G$, $G$ possesses uncountably many automorphism equivalence classes of weakly maximal subgroups containing $Q$. In particular, for Grigorchuk-Gupta-Sidki type groups this implies that they have uncountably many automorphism equivalence classes of weakly maximal subgroups tha…
Maximal subgroups of maximal rank in the classical algebraic groups
本文研究了经典代数群中最大秩最大子群的分类与实现条件，并探讨了其数量的渐进行为。
Branch groups with many maximal subgroups
本文通过嵌入技术构造了具有不可数多个极大子群的有限生成分支群，解决了Grigorchuk提出的问题。
We classify closed abelian subgroups of a compact simple Lie group of adjoint type and of type E having centralizer of the same dimension as the dimension of the subgroup and describe Weyl groups of maximal abelian subgroups.
The following result is received: Let $H$ be a non-normal maximal subgroup of a finite solvable group $G$ and let $q \in π(F(H/\mathrm{Core}_GH))$, then $G$ has a Sylow $q$-subgroup $Q$ such that $N_{G}(Q) \subseteq H$.
A note on maximal subgroups of countable groups
本文证明任意可数群的极大子群集合的基数只能是可数或 $2^{\aleph_0}$，解决了该集合基数的二分性问题。
We generalise a technical tool, originally developed by Pervova for the study of maximal subgroups in Grigorchuk and GGS groups, to all weakly branch groups satisfying a natural condition, and in particular to all branch groups. We then use this tool to prove that every maximal subgroup of infinite index of a branch group is also a branch group. As a further application of this result, we show that every maximal subgroup of the Basilica group is of finite index.
We classify abelian subgroups of the automorphism group of any compact simple Lie algebra whose centralizer has the same dimension as the dimension of the subgroup. This leads to a classification of the maximal abelian subgroups of compact simple groups of adjoint type and a classification of the fine group gradings of complex simple Lie algebras.
Maximal toroids and Cartan subgroups of algebraic groups
本文提出了一种适用于所有一次代数群的统一理论，探讨了极大环面与Cartan子群之间的关系，并推广了已知结果至更广泛的情况。
We determine all maximal subgroups of the almost simple groups with socle $T=\PSL(2,q)$, that is, of all groups $G$ such that $\PSL(2,q)\leqslant G\leqslant\PGammaL(2,q)$, with $q\geq 4$.
This paper is a survey on the works [MS77, MS79, MS81] on maximal subgroups in finitely generated linear groups, and the works that followed it [GG08, GG13b, GG13a, Kap03, Iva92, HO16, GM16, AGS14, Sf90, Sf98, Per05, AKT16, FG18, GS17] concerning maximal subgroups of infinite index in linear groups as well as in various other groups possessing a suitable geometry or dynamics.
Indices of non-supersolvable maximal subgroups in finite groups
基于Doerk和Hall关于有限群可解性的经典结果，本文刻画了极大子群为超可解或指数为素数/素数平方的非可解有限群的结构。
On SS-quasinormalities of the maximal subgroup series of finite groups
本文研究了有限群存在SS-准正则最大子群级数的条件，证明此类群可解，并探讨超可解性的等价条件。
In this note we give a classification of the Maximal order Abelian subgroups of finite irreducible Coxeter groups. We also prove a Weyl group analogue of Cartan's theorem that all maximal tori in a connected compact Lie group are conjugate.
Maximal subgroups in torsion branch groups
本研究针对分支群的极大子群展开，得到判定特定脊柱群属于有限指数极大子群类的准则，构造出该类内具新性质的分支群，还给出类外分支群实例及一个周期分支群。
Let $H$ be an open subgroup of a profinite group that can be expressed as intersection of maximal subgroups of $G.$ Given a positive real number $η,$ we say that $H$ is an $η$-intersection if there exists a family of maximal subgroups $M_1,\ldots,M_t$ such that $H=M_1\cap\ldots\cap M_t$ and $|G:M_1|\cdots|G:M_t|\le |G:H|^η$. We investigate the meaning of this property and its influence on the group structure.
Let $\mathfrak{X}$ be a class of finite groups closed under taking subgroups, homomorphic images and extensions. It is known that if $A$ is a normal subgroup of a finite group $G$ then the image of an $\mathfrak{X}$-maximal subgroup $H$ of $G$ in $G/A$ is not, in general, $\mathfrak{X}$-maximal in $G/A$. We say that the reduction $\mathfrak{X}$-theorem holds for a finite group $A$ if, for every finite group $G$ that is an extension of $A$ (i. e. contains $A$ as a normal subgroup), the number of conjugacy classes of $\mathfrak{X}$-maximal subgroups in $G$ and $G/A$ is the same. The reduction $\…
We classify closed abelian subgroups of the simple groups $G_2$, $F_4$, $Aut(so(8))$ having centralizer the same dimension as the dimension of the subgroup, as well as finite abelian subgroups of certain spin and half-spin groups having finite centralizer.
A subgroup $H$ of a group $G$ is called $\Bbb P$-{\sl subnormal} in $G$ if either $H=G$ or there is a chain of subgroups $H=H_0\subset H_1\subset...\subset H_n=G$ such that $|H_i:H_{i-1}|$ is prime for $1\le i\le n$. In this paper we study the groups all of whose 2-maximal subgroups are $\Bbb P$-subnormal.
We investigate the influence of the intersection of the $\cal F$-maximal subgroups on the structure of a finite group. In particular, answering a question of L.A Shemetkov we give conditions under which a hereditary saturated formation $\cal F$ has a property that for any finite group $G$, the ${\cal F}$-hypercentre of $G$ coincides with the intersection of all $\cal F$-maximal subgroups of $G$.
We prove the existence and uniqueness of a new maximal subgroup of the algebraic group of type $E_8$ in characteristic $3$. This has type $F_4$, and was missing from previous lists of maximal subgroups produced by Seitz and Liebeck--Seitz. We also prove a result about the finite group $H={}^3\!D_4(2)$, that if $H$ embeds in $E_8$ (in any characteristic $p$) and has two composition factors on the adjoint module then $p=3$ and $H$ lies in this new maximal $F_4$ subgroup.
A systematic study of maximal subgroups of the sporadic simple groups began in the 1960s. The work is now almost complete, only a few cases in the Monster remaining outstanding. We give a survey of results obtained, and methods used, over the past 50 years, for the classification of maximal subgroups of sporadic simple groups, and their automorphism groups.
A multi-edge spinal group is a subgroup of the automorphism group of a regular p-adic rooted tree, generated by one rooted automorphism and a finite number of directed automorphisms sharing a common directing path. We prove that torsion multi-edge spinal groups do not have maximal subgroups of infinite index. This generalizes a result of Pervova for GGS-groups.
Neumann property in the extended modular group and maximal nonparabolic subgroups of the modular group
本文引入扩展模群及其 Neumann 子群概念，并通过取其中正行列式元素给出模群的极大非抛物非 Neumann 子群的新构造。
On Maximal Subgroups of Thompson's Group $F$
本文利用自动机研究汤普森群$F$的子群，证明无限指标的极大子群是闭的，有限生成的极大子群无扭曲，且每个有限生成子群可嵌入有限生成的极大子群，并构造了无限多个不同构的极大子群。
Maximal and Frattini L-Subgroups of an L-Group
本文基于经典群论定义了L-群的极大L-子群并给出水平子集刻画，进而定义Frattini L-子群，发展非生成元概念并建立其与Frattini L-子群的关系，同时研究了相关性质并通过实例说明。
In 1933 B.~H.~Neumann constructed uncountably many subgroups of ${\rm SL}_2(\mathbb Z)$ which act regularly on the primitive elements of $\mathbb Z^2$. As pointed out by Magnus, their images in the modular group ${\rm PSL}_2(\mathbb Z)\cong C_3*C_2$ are maximal nonparabolic subgroups, that is, maximal with respect to containing no parabolic elements. We strengthen and extend this result by giving a simple construction using planar maps to show that for all integers $p\ge 3$, $q\ge 2$ the triangle group $Γ=Δ(p,q,\infty)\cong C_p*C_q$ has uncountably many conjugacy classes of nonparabolic maxima…
Let ${\mathfrak{X}}$ be a class of finite groups closed under taking subgroups, homomorphic images, and extensions. Denote by ${\mathrm{k}}_{\mathfrak{X}}(G)$ the number of conjugacy classes ${\mathfrak{X}}$-maximal subgroups of a finite group $G$. The natural problem to describe up to conjugacy ${\mathfrak{X}}$-maximal subgroups of a given finite group is complicated by the fact that it is not inductive. In particular, generally speaking, the image of an ${\mathfrak{X}}$-maximal subgroup is not ${\mathfrak{X}}$-maximal in the image of a homomorphism. Nevertheless, there are group homomorphism…
A Grigorchuk-Gupta-Sidki (GGS-)group is a subgroup of the automorphism group of the $p$-adic tree for an odd prime $p$, generated by one rooted automorphism and one directed automorphism. Pervova proved that all torsion GGS-groups do not have maximal subgroups of infinite index. Here we extend the result to non-torsion GGS-groups, which include the weakly regular branch, but not branch, GGS-group.
In this paper we obtain significant bounds for the number of maximal subgroups of a given index of a finite group. These results allow us to give new bounds for the number of random generators needed to generate a finite $d$-generated group with high probability.
In this paper, we set $η(G)$ to be the number of conjugacy classes of maximal cyclic subgroups of $G$. We prove that if $G$ is a $p$-group of order $p^n$ and nilpotence class $l$, then $η(G)$ is bounded below by a linear function in $n/l$.
We prove that all maximal subgroups of the free idempotent generated semigroup over a band B are free for all B belonging to a band variety V if and only if V consists either of left seminormal bands, or of right seminormal bands.
Finite simple groups with two maximal subgroups of coprime orders
本文基于Liebeck和Saxl关于奇阶极大子群的结果，分类了所有包含两个互素阶极大子群的有限非交换单群的三元组结构。
In [Li and Chen, A new characterization of the simple group A_1(p^n), Sib. Math. J., 2012], it is proved that the simple group A_1(p^n) is uniquely determined by the set of orders of its maximal abelian subgroups. Also in [Momen and Khosravi, Groups with the same orders of maximal abelian subgroups as A_2(q), Monatsh. Math., 2013], the authors proved that if L=A_2(q), where q is not a Mersenne prime, then every finite group with the same orders of maximal abelian subgroups as L, is isomorphic to L or an extension of L by a subgroup of the outer automorphism group of L. In this paper, we prove …
We investigate the class $\mathcal{MN}$ of groups with the property that all maximal subgroups are normal. The class $\mathcal{MN}$ appeared in the framework of the study of potential counter-examples to the Andrews-Curtis conjecture. In this note we give various structural properties of groups in $\mathcal{MN}$ and present examples of groups in $\mathcal{MN}$ and not in $\mathcal{MN}$.
Maximal subgroups of finitely presented special inverse monoids
本文研究了有限表示特殊逆幺半群的最大子群，证明其可能的最大子群恰好是递归表示群，并指出单位群恰好是有限生成递归表示群，首次揭示了超越单位群的子群结构复杂性。
Weakly maximal subgroups of branch groups
本文研究分支群的弱极大子群，描述了两个族（射线稳定化子的推广及块结构族），并证明对Grigorchuk群和挠性GGS群所有弱极大子群均属此二族，给出多种等价刻画。
Extensions of a theorem of P. Hall on indexes of maximal subgroups
本文推广 P. Hall 关于极大子群指数与有限群可解性的经典定理，证明在极大子群幂零或真非极大子群含于素数（平方）指数子群时，$G$ 仍可解。
We use the description of the Schutzenberger automata for amalgams of finite inverse semigroups given by Cherubini, Meakin, Piochi to obtain structural results for such amalgams. Schutzenberger automata, in the case of amalgams of finite inverse semigroups, are automata with special structure possessing finite subgraphs, that contain all essential information related to the whole automaton. Using this crucial fact, and the Bass-Serre theory, we show that the maximal subgroups of an amalgamated free-product are either isomorphic to certain subgroups of the original semigroups or can be describe…
For a finite group $G$ we investigate the difference between the maximum size MaxDim$(G)$ of an "independent" family of maximal subgroups of $G$ and maximum size $m(G)$ of an irredundant sequence of generators of $G$. We prove that MaxDim$(G)=m(G)$ if the derived subgroup of $G$ is nilpotent. However MaxDim$(G)-m(G)$ can be arbitrarily large: for any odd prime $p,$ we construct a finite soluble group with Fitting length 2 satisfying $m(G)=3$ and MaxDim$(G)=p.$
Let $G$ be a finite almost simple group. It is well known that $G$ can be generated by 3 elements, and in previous work we showed that 6 generators suffice for all maximal subgroups of $G$. In this paper we consider subgroups at the next level of the subgroup lattice - the so-called second maximal subgroups. We prove that with the possible exception of some families of rank 1 groups of Lie type, the number of generators of every second maximal subgroup of $G$ is bounded by an absolute constant. We also show that such a bound holds without any exceptions if and only if there are only finitely m…
Explicit construction of the maximal subgroups of the Monster
本文利用 mmgroup 软件包显式构造怪兽群所有极大子群共轭类的生成元并独立验证其分类，同时纠正 $\mathrm{PSL}_2({59})$ 为极大子群的说法，发现新的极大子群 $59{:}29$。
Products of nonconjugate maximal subgroups
该研究证明了满足任意一对非共轭极大子群乘积为群本身的有限群必可解，否定解决了库罗夫卡问题集的10.34号问题，并应用该结果解答了Guo提出的一个公开问题。
We give here the exact maximal subgroup growth of two classes of polycyclic groups. Let $G_k = \langle x_1, x_2, ..., x_k \mid x_ix_jx_i^{-1}x_j \text{ for all } i < j \rangle$. So $G_k = \mathbb{Z} \rtimes (\mathbb{Z} \rtimes (\mathbb{Z} \rtimes ... \rtimes \mathbb{Z})$. Then for all $k \geq 2$, we calculate $m_n(G_k)$, the number of maximal subgroups of $G_k$ of index $n$, exactly. Also, for infinitely many groups $H_k$ of the form $\mathbb{Z}^2 \rtimes G_2$, we calculate $m_n(H_k)$ exactly.
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