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Huppert's ρ − σ conjecture for conjugacy class sizes 共轭类大小的于佩尔ρ − σ猜想
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-12-08 DOI: 10.1016/j.jalgebra.2025.12.007
Egle Bettio
Let ρ(G) be the number of distinct prime divisors occurring among the conjugacy class sizes of a finite group G, and let σ(G) be the maximum number of such divisors in any single class size. We prove that the inequality ρ(G)3σ(G)1 holds for all finite groups, with no assumption of solvability. The bound is sharp, and refines earlier partial results.
设ρ(G)为有限群G的共轭类大小中出现的不同素数因数的个数,设σ(G)为任何单一类大小中出现的最大素数因数的个数。证明了不等式ρ(G)≤3σ(G)−1对所有有限群都成立,且没有可解的假设。它的界很明显,并且改进了先前的部分结果。
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引用次数: 0
On zero-measured subsets of Thompson's group F 关于汤普森群F的零测量子集
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-12-08 DOI: 10.1016/j.jalgebra.2025.12.006
Victor Guba
A (discrete) group is called amenable if there exists a finitely additive right-invariant probability measure on it. The question of whether Thompson's group F is amenable is a long-standing open problem. We consider the presentation of F in terms of non-spherical semigroup diagrams. There is a natural partition of F into 7 parts in terms of these diagrams. We show that for any finitely additive right-invariant probability measure on F, all but one of these sets have zero measure. This helps to clarify the structure of Følner sets in F, provided the group is amenable.
如果在一个(离散)群上存在一个有限可加的右不变概率测度,则称为可调群。汤普森的F组是否可以接受的问题是一个长期存在的开放性问题。我们考虑用非球半群图表示F。在这些图中,F被自然划分为7个部分。我们证明了对于F上的任何有限可加的右不变概率测度,这些集合除了一个以外都是零测度。这有助于澄清F中Følner集合的结构,前提是群是可服从的。
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引用次数: 0
Isogenies and congruence subgroups 同基因和同余子群
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-12-08 DOI: 10.1016/j.jalgebra.2025.12.001
Shengkai Mao
Let π:GH be an isogeny between linear algebraic groups over a number field E, S be a finite set of places of E. In this note, we give some criteria for when a S-congruence subgroup of G(E) has S-congruence image in H(E) following [7].
设π:G→H是数域E上的线性代数群之间的等同子群,S是E的有限位集,本文给出了G(E)的S同余子群在H(E)上有S同余像的几个判据。
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引用次数: 0
Almost inner derivations of Lie superalgebras 李超代数的几乎内导
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-12-08 DOI: 10.1016/j.jalgebra.2025.11.030
Vera Serganova , Arkady Vaintrob
An almost inner derivation of a Lie algebra L is a derivation that coincides with an inner derivation on each one-dimensional subspace of L. The almost inner derivations form a subalgebra aDer(L) of the Lie algebra Der(L) of all derivations of L, containing the inner derivations iDer(L) as an ideal. If L is a simple finite-dimensional Lie algebra, then aDer(L)=iDer(L), since all derivations of L are inner.
In this paper, we introduce and study almost inner derivations of Lie superalgebras. Since simple Lie superalgebras may admit non-inner outer derivations, the existence of non-inner almost inner derivations becomes a nontrivial question. Nevertheless, we show that all almost inner derivations of finite-dimensional simple Lie superalgebras over C are inner. We also give examples of naturally occurring non-inner almost inner derivations of some quasireductive Lie superalgebras related to the Sato-Kimura classification of prehomogeneous vector spaces.
李代数L的几乎内导数是与L的每一一维子空间上的内导数相吻合的导数。几乎内导数构成了L的所有导数的李代数Der(L)的子代数aDer(L),其中包含了作为理想的内导数iDer(L)。如果L是一个简单的有限维李代数,则aDer(L)=iDer(L),因为L的所有导都是内导。本文引入并研究了李超代数的几乎内导。由于简单李超代数可以允许非内外导,因此非内几乎内导的存在性成为一个非平凡问题。然而,我们证明了C上有限维简单李超代数的所有几乎内导都是内导。我们还给出了与预齐次向量空间的Sato-Kimura分类有关的一些拟约李超代数的自然非内几乎内导数的例子。
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引用次数: 0
Efficient algorithms for maximal matroid degenerations and irreducible decompositions of circuit varieties 矩阵最大退化和电路不可约分解的有效算法
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-12-08 DOI: 10.1016/j.jalgebra.2025.12.003
Emiliano Liwski , Fatemeh Mohammadi , Rémi Prébet
Matroid theory provides a unifying framework for studying dependence across combinatorics, geometry, and applications ranging from rigidity to statistics. In this work, we study circuit varieties of matroids, defined by their minimal dependencies, which play a central role in modeling determinantal varieties, rigidity problems, and conditional independence relations. We introduce an efficient computational strategy for decomposing the circuit variety of a given matroid M, based on an algorithm that identifies its maximal degenerations. These degenerations correspond to the largest matroids lying below M in the weak order. Our framework yields explicit and computable decompositions of circuit varieties that were previously out of reach for symbolic or numerical algebra systems. We apply our strategy to several classical configurations, including the Vámos matroid, the unique Steiner quadruple system S(3,4,8), projective and affine planes, the dual of the Fano matroid, and the dual of the graphic matroid of K3,3. In each case, we successfully compute the minimal irreducible decomposition of their circuit varieties.
矩阵理论为研究组合学、几何以及从刚性到统计学的应用之间的依赖性提供了一个统一的框架。在这项工作中,我们研究了由它们的最小依赖关系定义的拟阵的电路变种,它们在决定变种、刚性问题和条件独立关系的建模中起着核心作用。我们介绍了一种有效的计算策略,用于分解给定矩阵M的电路变化,基于识别其最大退化的算法。这些退化对应于弱阶中M以下最大的类人猿。我们的框架产生了电路变量的显式和可计算的分解,这在以前是符号或数值代数系统无法实现的。我们将我们的策略应用于几种经典构型,包括Vámos矩阵,唯一的Steiner四重系统S(3,4,8),投影和仿射平面,Fano矩阵的对偶以及k3,3的图形矩阵的对偶。在每种情况下,我们都成功地计算了它们的电路变种的最小不可约分解。
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引用次数: 0
Brauer pairs for splendid Rickard equivalences Brauer对的绝妙里卡德等价
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-12-05 DOI: 10.1016/j.jalgebra.2025.11.029
Jadyn V. Breland, Sam K. Miller
We define the notion of a Brauer pair of a chain complex, extending the notion of a Brauer pair of a p-permutation module introduced by Boltje and Perepelitsky. In fact, the Brauer pairs of a splendid Rickard equivalence C coincide with the set of Brauer pairs of the corresponding p-permutation equivalence Λ(C) induced by C. As a result, we derive structural results for splendid Rickard equivalences that correspond to known structural properties for p-permutation equivalences. In particular, we show splendid Rickard equivalences induce local splendid Rickard equivalences between normalizer block algebras as well as centralizer block algebras.
在Boltje和Perepelitsky提出的p-置换模的Brauer对概念的基础上,定义了链复合体的Brauer对的概念。事实上,一个极好的Rickard等价C的Brauer对与C所导出的相应的p-置换等价Λ(C)的Brauer对集合是一致的。因此,我们得到了与已知的p-置换等价结构性质相对应的极好的Rickard等价的结构结果。特别地,我们证明了正规整块代数和正规整块代数之间的华丽里卡德等价可以推导出局部华丽里卡德等价。
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引用次数: 0
Modularity of vertex operator algebra correlators with zero modes 零模顶点算子代数相关器的模块化
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-12-05 DOI: 10.1016/j.jalgebra.2025.11.028
Darlayne Addabbo , Christoph A. Keller
It is known from Zhu's results that under modular transformations, correlators of rational C2-cofinite vertex operator algebras transform like Jacobi forms. We investigate the modular transformation properties of VOA correlators that have zero modes inserted. We derive recursion relations for such correlators and use them to establish modular transformation properties. For holomorphic VOAs we find that correlators with only zero modes transform like quasi-modular forms, and mixed correlators with both zero modes and vertex operators transform like quasi-Jacobi forms. As an application of our results, we introduce algebras of higher weight fields whose zero mode correlators mimic the properties of those of weight 1 fields. We also give a simplified proof of the weight 1 transformation properties originally proven by Miyamoto.
由Zhu的结果可知,在模变换下,有理c2有限顶点算子代数的相关子变换为Jacobi形式。我们研究了插入零模的VOA相关器的模变换特性。我们推导了这些相关器的递归关系,并用它们来建立模变换性质。对于全纯voa,我们发现只有零模的相关器变换为拟模形式,同时具有零模和顶点算子的混合相关器变换为拟雅可比形式。作为我们结果的一个应用,我们引入了高权重场的代数,它们的零模相关器模拟了权重1场的性质。我们也给出了最初由宫本证明的权值为1的变换性质的简化证明。
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引用次数: 0
Skew Calabi–Yau property of faithfully flat Hopf Galois extensions 忠实平Hopf Galois扩展的歪斜Calabi-Yau性质
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-12-05 DOI: 10.1016/j.jalgebra.2025.11.031
Ruipeng Zhu
This paper shows that if H is a Hopf algebra and AB is a faithfully flat H-Galois extension, then B is skew Calabi–Yau provided A and H are. Specifically, for cleft extensions AB, the Nakayama automorphism of B can be derived from those of A and H, along with the homological determinant of the H-action on A. This finding is based on the study of the Hopf bimodule structure on ExtAei(A,Be).
本文证明,如果H是一个Hopf代数,且a是一个忠实平坦的H-伽罗瓦扩展,则在a、H为的条件下,B是一个偏Calabi-Yau。具体而言,对于裂外延A (A, be),B的中山自同构可由A和H的中山自同构导出,且H对A的作用具有同构行列式。这一发现基于对ExtAei(A, be)上的Hopf双模结构的研究。
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引用次数: 0
Multiple rational normal forms in Lie theory 李论中的多重有理范式
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-12-05 DOI: 10.1016/j.jalgebra.2025.11.019
Dmitriy Voloshyn
We study the decomposition of a generic element gG of a connected reductive complex algebraic group G in the form g=N(g)B(g)u¯N(g)1 where N:GN and B:GB+ are rational maps onto a unipotent subgroup N and a Borel subgroup B+ opposite to N, and u¯ is a representative of a Weyl group element u. We introduce a class of rational Weyl group elements that give rise to such decompositions, and study their various properties.
研究了连通约化复代数群g的一般元素g∈g的分解,其形式为g=N(g)B(g)u¯N(g)−1,其中N: g讲解N−和B: g讲解B+是幂偶子群N−和与N−相对的Borel子群B+的有理映射,u¯是Weyl群元素u的代表。我们引入了一类引起这种分解的有理Weyl群元素,并研究了它们的各种性质。
{"title":"Multiple rational normal forms in Lie theory","authors":"Dmitriy Voloshyn","doi":"10.1016/j.jalgebra.2025.11.019","DOIUrl":"10.1016/j.jalgebra.2025.11.019","url":null,"abstract":"<div><div>We study the decomposition of a generic element <span><math><mi>g</mi><mo>∈</mo><mi>G</mi></math></span> of a connected reductive complex algebraic group <em>G</em> in the form <span><math><mi>g</mi><mo>=</mo><mi>N</mi><mo>(</mo><mi>g</mi><mo>)</mo><mi>B</mi><mo>(</mo><mi>g</mi><mo>)</mo><mover><mrow><mi>u</mi></mrow><mrow><mo>¯</mo></mrow></mover><mi>N</mi><msup><mrow><mo>(</mo><mi>g</mi><mo>)</mo></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span> where <span><math><mi>N</mi><mo>:</mo><mi>G</mi><mo>⇢</mo><msub><mrow><mi>N</mi></mrow><mrow><mo>−</mo></mrow></msub></math></span> and <span><math><mi>B</mi><mo>:</mo><mi>G</mi><mo>⇢</mo><msub><mrow><mi>B</mi></mrow><mrow><mo>+</mo></mrow></msub></math></span> are rational maps onto a unipotent subgroup <span><math><msub><mrow><mi>N</mi></mrow><mrow><mo>−</mo></mrow></msub></math></span> and a Borel subgroup <span><math><msub><mrow><mi>B</mi></mrow><mrow><mo>+</mo></mrow></msub></math></span> opposite to <span><math><msub><mrow><mi>N</mi></mrow><mrow><mo>−</mo></mrow></msub></math></span>, and <span><math><mover><mrow><mi>u</mi></mrow><mrow><mo>¯</mo></mrow></mover></math></span> is a representative of a Weyl group element <em>u</em>. We introduce a class of rational Weyl group elements that give rise to such decompositions, and study their various properties.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"691 ","pages":"Pages 453-487"},"PeriodicalIF":0.8,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
On subalgebras of the Griess algebra with alternating Miyamoto group 交替Miyamoto群的Griess代数的子代数
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-12-05 DOI: 10.1016/j.jalgebra.2025.11.032
Clara Franchi , Mario Mainardis
We use Majorana representations to study the subalgebras of the Griess algebra that have shape (2B,3A,5A) and whose associated Miyamoto groups are isomorphic to An. We prove that these subalgebras exist only if n{5,6,8}. The case n=5 was already treated by Ivanov, Seress, McInroy, and Shpectorov. In case n=6 we prove that these algebras are all isomorphic and provide their precise description. In case n=8 we prove that these algebras do not arise from standard Majorana representations.
我们用Majorana表示研究了形状为(2B,3A,5A)的Griess代数的子代数,其相关的Miyamoto群与An同构。证明这些子代数仅在n∈{5,6,8}时存在。病例n=5已经由Ivanov、Seress、McInroy和Shpectorov治疗过。在n=6的情况下,我们证明了这些代数都是同构的,并给出了它们的精确描述。在n=8的情况下,我们证明了这些代数不是由标准马约拉纳表示产生的。
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引用次数: 0
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Journal of Algebra
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