Commuting graphs of odd prime order elements in simple groups

特征为2的有限域上辛李代数中的交换对

Commuting pairs in symplectic Lie algebras over finite fields of characteristic two

参照奇特征下的相关研究，给出特征为2的有限域上辛李代数中有序交换对个数的生成函数。

On the intersection density of primitive groups of degree a product of two odd primes

A subset $\mathcal{F}$ of a finite transitive group $G\leq \operatorname{Sym}(Ω)$ is intersecting if for any $g,h\in \mathcal{F}$ there exists $ω\in Ω$ such that $ω^g = ω^h$. The \emph{intersection density} $ρ(G)$ of $G$ is the maximum of $\left\{ \frac{|\mathcal{F}|}{|G_ω|} \mid \mathcal{F}\subset G \mbox{ is intersecting} \right\}$, where $G_ω$ is the stabilizer of $ω$ in $G$. In this paper, it is proved that if $G$ is an imprimitive group of degree $pq$, where $p$ and $q$ are distinct odd primes, with at least two systems of imprimitivity then $ρ(G) = 1$. Moreover, if $G$ is primitive of de…

Characterization of SL(2,q) by its non-commuting graph

Let $G$ be a non-abelian group and $Z(G)$ be its center. The non-commuting graph $\mathcal{A}_G$ of $G$ is the graph whose vertex set is $G\backslash Z(G)$ and two vertices are joined by an edge if they do not commute. Let $\mathrm{SL}(2,q)$ be the special linear group of degree 2 over the finite field of order $q$. In this paper we prove that if $G$ is a group such that $\mathcal{A}_G\cong \mathcal{A}_{\mathrm{SL}(2,q)}$ for some prime power $q\geq 2$, then $G\cong \mathrm{SL}(2,q)$.

The commuting complex of the symmetric group with bounded number of $p$-cycles

For a fixed prime $p$, we consider a filtration of the commuting complex of elements of order $p$ in the symmetric group $\mathfrak{S}_n$. The filtration is obtained by imposing successively relaxed bounds on the number of disjoint $p$-cycles in the cycle decomposition of the elements. We show that each term in the filtration becomes highly acyclic as $n$ increases. We use $\mathbf{FI}$-modules in the proof.

单位上三角群UT(4; p)的交换图

Commuting Graph of Unitriangular Group UT(4; p)

本文研究有限域Fp上的4阶单位上三角群UT(4; p)的交换图，明确其交换关系，证明约化交换图连通且直径为3，还确定了其最大团大小、色数等图论性质。

Connected Quandles with Order Equal to Twice an Odd Prime

We show that there is an unique connected quandle of order twice an odd prime number greater than 3. It has order 10 and is isomorphic to the conjugacy class of transpositions in the symmetric group of degree 5. This establishes a conjecture of L. Vendramin.

$p$ 为奇素数时 $p^6$ 阶群的忠实置换表示的最小次数

Minimal degrees for faithful permutation representations of groups of order $p^6$ where $p$ is an odd prime

本文确定了奇素数 $p$ 下所有 $p^6$ 阶群的忠实置换表示的最小次数，并给出了构造方法。

Hopf Galois structures on extensions of degree twice an odd prime square and their associated left braces

We determine the Hopf Galois structures on a Galois field extension of degree twice an odd prime square and classify the corresponding left braces. Besides we determine the separable field extensions of degree twice an odd prime square allowing a cyclic Hopf Galois structure and the number of these structures.

Common neighbourhood spectrum and energy of commuting conjugacy class graph

In this paper we compute common neighbourhood (abbreviated as CN) spectrum and energy of commuting conjugacy class graph of several families of finite non-abelian groups. As a consequence of our results we show that the commuting conjugacy class graphs of the groups $D_{2n}$, $T_{4n}$, $SD_{8n}$, $U_{(n,m)}$, $U_{6n}$, $V_{8n}$, $G(p, m, n)$ and some families of groups whose central quotient is isomorphic to $D_{2n}$ or $Z_p \times Z_p$, for some prime $p$, are CN-integral but not CN-hyperenergetic.

交换图的若干方面

Aspects of the commuting graph

本文研究有限群交换图的识别问题，给出一般拟多项式算法及超特殊 $p$-群情形的多项式算法，并探讨交换图为 cograph 或弦图的条件。

有限群中 $\pi$-元素的交换概率

On the commuting probability of $π$-elements in finite groups

本文研究有限群中 $\pi$-元素的交换概率，证明了存在正规阿贝尔 Hall $\pi$-子群的充要条件是交换概率大于 $\frac{p^2+p-1}{p^3}$，并给出非 $O_\pi(G)$ 元素的交换比例上界。

Spectrum and energies of commuting conjugacy class graph of a finite group

In this paper we compute spectrum, Laplacian spectrum, signless Laplacian spectrum and their corresponding energies of commuting conjugacy class graph of the group $G(p, m, n) = \langle x, y : x^{p^m} = y^{p^n} = [x, y]^p = 1, [x, [x, y]] = [y, [x, y]] = 1\rangle$, where $p$ is any prime, $m \geq 1$ and $n \geq 1$. We derive some consequences along with the fact that commuting conjugacy class graph of $G(p, m, n)$ is super integral. We also compare various energies and determine whether commuting conjugacy class graph of $G(p, m, n)$ is hyperenergetic, L-hyperenergetic or Q-hyperenergetic.

评论：Rodney James 的论文《阶为 $p^6$ 的群（$p$ 为奇素数）》，Math. Comput. 34 (1980), 613-637

Comment on: The groups of order $p^6$ ($p$ an odd prime) By Rodney James, Math. Comput. 34 (1980), 613-637

本文总结并评述了 James 1980 年关于奇素数 $p$ 的 $p^6$ 阶群分类论文中多年来被发现的多处错误。

Permutation-like Matrix Groups with a Maximal Cycle of Power of Odd Prime Length

If every element of a matrix group is similar to a permutation matrix, then it is called a permutation-like matrix group. References [4] and [5] showed that, if a permutation-like matrix group contains a maximal cycle of length equal to a prime or a square of a prime and the maximal cycle generates a normal subgroup, then it is similar to a permutation matrix group. In this paper, we prove that if a permutation-like matrix group contains a maximal cycle of length equal to any power of any odd prime and the maximal cycle generates a normal subgroup, then it is similar to a permutation matrix gr…

A new infinite family of non-abelian strongly real Beauville $p$-groups for every odd prime $p$

We prove that there exist infinitely many a non-abelian strongly real Beauville $p$-group for every prime $p$. Previously only finitely many in the case $p=2$ have been constructed.

A note on commuting automorphisms of some finite $p$-groups

An automorphism $α$ of a group $G$ is called a commuting automorphism if each element $x$ in $G$ commutes with its image $α(x)$ under $α$. Let $A(G)$ denote the set of all commuting automorphisms of $G$. Rai [Proc. Japan Acad., Ser. A {\bf 91} (2015), no. 5, 57-60] has given some sufficient conditions on a finite $p$-group $G$ such that $A(G)$ is a subgroup of Aut$(G)$ and, as a consequence, has proved that in a finite $p$-group $G$ of co-class 2, where $p$ is an odd prime, $A(G)$ is a subgroup of Aut$(G)$. We give here very elementary and short proofs of main results of Rai.

Inductive blockwise Alperin weight condition for type B and odd primes

By the reduction theorems of Navarro--Tiep and Späth, a way to prove the Alperin weight conjecture and its blockwise version is to verify the co-called inductive Alperin weight condition and inductive blockwise Alperin weight condition for all finie simple groups respectively. In this paper, we establish the inductive blockwise Alperin weight condition for simple groups of type $\mathsf B$ and odd primes, using a criterion given by Brough and Späth recently.

有限群的博弈导体：来自结构化收益探测的行列式挠率

Game Conductors of Finite Groups: Determinantal Torsion from Structured Payoff Probes

研究有限群\(G\)与结构化收益探测\(\phi\)相关的收益差格及导体，通过精确计算得出CA - 群交换导体公式，利用伽罗瓦轨道迹特征探测补充结果，经详尽计算和分析支持对压缩中心化子型关联矩阵\(\BG\)的史密斯挠率进行分类。

Absolutely simple polarized abelian varieties of odd Sophie Germain prime dimension over finite fields with maximal automorphism groups

For each Sophie Germain prime $g \geq 5,$ we construct an absolutely simple polarized abelian variety of dimension $g$ over a finite field, whose automorphism group is a cyclic group of order $4g+2$. We also provide a description on the asymptotic behavior of prime numbers that are related to our construction.

三角矩阵与单位三角矩阵的分支规则与交换概率

Branching rules and commuting probabilities for Triangular and Unitriangular matrices

本文通过计算分支规则，枚举了奇特征有限域上三角群与单位三角群中小规模情形的同时共轭类，并利用分支矩阵显式求出了相应的交换概率。

Commuting elements in central products of special unitary groups

In this paper the space of commuting elements in the central product $G_{m,p}$ of $m$ copies of the special unitary group $SU(p)$ is studied, where $p$ is a prime number. In particular, a computation for the number of path connected components of these spaces is given and the geometry of the moduli space $\Rep(\mathbb Z^n, G_{m,p})$ of flat principal $G_{m,p}$--bundles over the $n$--torus is completely described for all values of $n$, $m$ and $p$.

On the multiple holomorph of groups of squarefree or odd prime power order

Let $G$ be a group and write $\mbox{Perm}(G)$ for its symmetric group. Define $\mbox{Hol}(G)$ to be the holomorph of $G$, regarded as a subgroup of $\mbox{Perm}(G)$, and let $\mbox{NHol}(G)$ denote its normalizer. The quotient $T(G) = \mbox{NHol}(G)/\mbox{Hol}(G)$ has been computed for various families of groups $G$, and in most of the known cases, it turns out to be elementary $2$-abelian, except for two groups of order $16$ and some groups of odd prime power order and nilpotency class two. In this paper, we shall show that $T(G)$ is elementary $2$-abelian for all finite groups $G$ of squaref…

All p-local finite groups of rank two for odd prime p

In this paper we give a classification of the rank two p-local finite groups for odd p. This study requires the analisis of the possible saturated fusion systems in terms of the outer automorphism group ant the proper F-radical subgroups. Also, for each case in the classification, either we give a finite group with the corresponding fusion system or we check that it corresponds to an exotic p-local finite group, getting some new examples of these for p = 3.

Enumeration of involutory latin quandles, Bruck loops and commutative automorphic loops of odd prime power order

There is a one-to-one correspondence between involutory latin quandles and uniquely $2$-divisible Bruck loops. Bruck loops of odd prime power order are centrally nilpotent. Using linear-algebraic approach to central extensions, we enumerate Bruck loops (and hence involutory latin quandles) of order $3^k$ for $k\le 5$, except for those loops that are central extensions of the cyclic group of order $3$ by the elementary abelian group of order $3^4$. Among the constructed loops there is a Bruck loop of order $3^5$ whose associated $Γ$-loop is not a commutative automorphic loop. We independently e…

Upper bound on the number of ramified primes for odd order solvable groups

Let $G$ be a finite group and let $ram^{t}(G)$ denote the minimal positive integer $n$ such that $G$ can be realized as the Galois group of a tamely ramified extension of $\mathbb{Q}$ ramified only at $n$ finite primes. Let $d(G)$ denote the minimal non negative integer for which there exists a subset $X$ of $G$ with $d(G)$ elements such that the normal subgroup of $G$ generated by $X$ is all of $G$. It is known that $d(G)\leq ram^{t}(G)$. However, it is unknown whether or not every finite group $G$ can be realized as a Galois group of a tamely ramified extension of $\mathbb{Q}$ with exactly $…

奇素数阶元素的Brauer-Fowler界

Brauer-Fowler Bounds for Elements of Odd Prime Order

本文研究奇素数阶元素的Brauer-Fowler界，证明Skresanov的对合相关结果的直接类似物对奇素数阶元素不成立，给出了有限单群阶数由中心化子内p阶元素数量及指数界定的结论。

Hopf Galois structures on separable field extensions of odd prime power degree

A Hopf Galois structure on a finite field extension $L/K$ is a pair $(\mathcal{H},μ)$, where $\mathcal{H}$ is a finite cocommutative $K$-Hopf algebra and $μ$ a Hopf action. In this paper, we present several results on Hopf Galois structures on odd prime power degree separable field extensions. We prove that if a separable field extension of odd prime power degree has a Hopf Galois structure of cyclic type, then it has no structure of noncyclic type. We determine the number of Hopf Galois structures of cyclic type on a separable field extension of degree $p^n$, $p$ an odd prime, such that the G…

有限群的交换共轭类图与Hansen-Vukičević猜想

Commuting Conjugacy Class Graphs of Finite Groups and the Hansen-Vukičević Conjecture

本文计算了有限群交换共轭类图的Zagreb指数，并证明了多种有限群及其商群的交换共轭类图满足Hansen-Vukičević猜想。

Computation of Hopf Galois structures on separable extensions and classification of those for degree twice an odd prime power

A Hopf Galois structure on a finite field extension $L/K$ is a pair $(H,μ)$, where $H$ is a finite cocommutative $K$-Hopf algebra and $μ$ a Hopf action. In this paper we present a program written in the computational algebra system Magma which gives all Hopf Galois structures on separable field extensions of a given degree and several properties of those. We show a table which summarizes the program results. Besides, for separable field extensions of degree $2p^n$, with $p$ an odd prime number, we prove that the occurrence of some type of Hopf Galois structure may either imply or exclude the o…

有限群中 p-元素的交换概率

On the commuting probability of p-elements in a finite group

本文研究有限群中两个随机 p-元素可交换的概率，证明其大于 (p^2+p-1)/p^3 当且仅当群具有正规交换的 Sylow p-子群，并分类了达到该最优下界的所有群。

奇素数下Demushkin群的$A_3$-形式性

$A_3$-formality for Demushkin groups at odd primes

该研究针对奇素数下的Demushkin群，探讨微分分次代数的$A_3$-形式性，通过计算Hochschild上同调中的Benson-Krause-Schwede典范类，证明q不变量是否为3决定了其连续上链代数是否满足$A_3$-形式性。

Characters of odd degree

We prove the McKay conjecture on characters of odd degree. A major step in the proof is the verification of the inductive McKay condition for groups of Lie type and primes $\ell$ such that a Sylow $\ell$-subgroup or its maximal normal abelian subgroup is contained in a maximally split torus by means of a new equivariant version of Harish-Chandra induction. Specifics of characters of odd degree, namely that they only lie in very particular Harish-Chandra series then allow us to deduce from it the McKay conjecture for the prime~$2$, hence for characters of odd degree.