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Orbits on a product of two flags and a line and the Bruhat order, I 轨道是由两面旗帜和一条线以及布鲁哈特命令组成的
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-09-29 DOI: 10.1016/j.jpaa.2025.108100
Mark Colarusso , Sam Evens
<div><div>Let <span><math><mi>G</mi><mo>=</mo><mi>G</mi><mi>L</mi><mo>(</mo><mi>n</mi><mo>)</mo></math></span> be the <span><math><mi>n</mi><mo>×</mo><mi>n</mi></math></span> complex general linear group and let <span><math><msub><mrow><mi>B</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> be its flag variety. The standard Borel subgroup <em>B</em> of upper triangular matrices acts on the product <span><math><msub><mrow><mi>B</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>×</mo><msup><mrow><mi>P</mi></mrow><mrow><mi>n</mi><mo>−</mo><mn>1</mn></mrow></msup></math></span> diagonally with finitely many orbits. In this paper, we study the <em>B</em>-orbits on the subvarieties <span><math><msub><mrow><mi>B</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>×</mo><msub><mrow><mi>O</mi></mrow><mrow><mi>i</mi></mrow></msub></math></span>, where <span><math><msub><mrow><mi>O</mi></mrow><mrow><mi>i</mi></mrow></msub></math></span> is the <em>B</em>-orbit on <span><math><msup><mrow><mi>P</mi></mrow><mrow><mi>n</mi><mo>−</mo><mn>1</mn></mrow></msup></math></span> containing the line through the origin in the direction of the <em>i</em>-th standard basis vector of <span><math><msup><mrow><mi>C</mi></mrow><mrow><mi>n</mi></mrow></msup></math></span>. For each <span><math><mi>i</mi><mo>=</mo><mn>1</mn><mo>,</mo><mo>…</mo><mo>,</mo><mi>n</mi></math></span>, we construct a bijection between <em>B</em>-orbits on <span><math><msub><mrow><mi>B</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>×</mo><msub><mrow><mi>O</mi></mrow><mrow><mi>i</mi></mrow></msub></math></span> and certain pairs of Schubert cells in <span><math><msub><mrow><mi>B</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>×</mo><msub><mrow><mi>B</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span>. We also show that this bijection can be used to understand the Richardson-Springer monoid action on such <em>B</em>-orbits in terms of the classical monoid action of the symmetric group on itself. We also develop combinatorial models of these orbits and use these models to compute exponential generating functions for the sequences <span><math><msub><mrow><mo>{</mo><mo>|</mo><mi>B</mi><mo>﹨</mo><mo>(</mo><msub><mrow><mi>B</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>×</mo><msub><mrow><mi>O</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>)</mo><mo>|</mo><mo>}</mo></mrow><mrow><mi>n</mi><mo>≥</mo><mn>1</mn></mrow></msub></math></span> and <span><math><msub><mrow><mo>{</mo><mo>|</mo><mi>B</mi><mo>﹨</mo><mo>(</mo><msub><mrow><mi>B</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>×</mo><msup><mrow><mi>P</mi></mrow><mrow><mi>n</mi><mo>−</mo><mn>1</mn></mrow></msup><mo>)</mo><mo>|</mo><mo>}</mo></mrow><mrow><mi>n</mi><mo>≥</mo><mn>1</mn></mrow></msub></math></span>. In the sequel to this paper, we use the results of this paper to construct a correspondence between <em>B</em>-orbits on <span><math><msub><mrow><mi>B</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>×</mo><msup><mrow><mi>P</mi></mrow><mrow><mi>n</mi><mo>−</mo><mn>1</mn>
设G=GL(n)为n×n复一般线性群,设Bn为其标志簇。上三角矩阵的标准Borel子群B作用于乘积Bn×Pn−1与有限多轨道对角线。本文研究了子集Bn×Oi上的b轨道,其中Oi是Pn−1上的b轨道,其中包含了沿Cn的第i个标准基向量方向穿过原点的直线。对于每个i=1,…,n,我们在Bn×Oi上的b轨道和Bn×Bn上的某些Schubert细胞对之间构造一个双射。我们还证明了这种双射可以用对称群对自身的经典单群作用来理解b轨道上的Richardson-Springer单群作用。我们还建立了这些轨道的组合模型,并使用这些模型计算了序列{|B(Bn×Oi)|}n≥1和{|B(Bn×Pn−1)|}n≥1的指数生成函数。在本文的续文中,我们利用本文的结果构造了Bn×Pn−1上的b轨道与GL(n+1)的标志簇Bn+1上的b轨道集合之间的对应关系,并证明了这种对应关系尊重闭包关系并保留了单群作用。因此,利用我们在[1]中的结果,可以通过Bruhat阶来理解Bn×Pn−1上所有b轨道集合上的闭包关系和幺正作用。
{"title":"Orbits on a product of two flags and a line and the Bruhat order, I","authors":"Mark Colarusso ,&nbsp;Sam Evens","doi":"10.1016/j.jpaa.2025.108100","DOIUrl":"10.1016/j.jpaa.2025.108100","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Let &lt;span&gt;&lt;math&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; be the &lt;span&gt;&lt;math&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; complex general linear group and let &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; be its flag variety. The standard Borel subgroup &lt;em&gt;B&lt;/em&gt; of upper triangular matrices acts on the product &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;P&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt; diagonally with finitely many orbits. In this paper, we study the &lt;em&gt;B&lt;/em&gt;-orbits on the subvarieties &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, where &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; is the &lt;em&gt;B&lt;/em&gt;-orbit on &lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;P&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt; containing the line through the origin in the direction of the &lt;em&gt;i&lt;/em&gt;-th standard basis vector of &lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt;. For each &lt;span&gt;&lt;math&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mo&gt;…&lt;/mo&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, we construct a bijection between &lt;em&gt;B&lt;/em&gt;-orbits on &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and certain pairs of Schubert cells in &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;. We also show that this bijection can be used to understand the Richardson-Springer monoid action on such &lt;em&gt;B&lt;/em&gt;-orbits in terms of the classical monoid action of the symmetric group on itself. We also develop combinatorial models of these orbits and use these models to compute exponential generating functions for the sequences &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mo&gt;{&lt;/mo&gt;&lt;mo&gt;|&lt;/mo&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;mo&gt;﹨&lt;/mo&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;mo&gt;|&lt;/mo&gt;&lt;mo&gt;}&lt;/mo&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;mo&gt;≥&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mo&gt;{&lt;/mo&gt;&lt;mo&gt;|&lt;/mo&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;mo&gt;﹨&lt;/mo&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;P&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;mo&gt;|&lt;/mo&gt;&lt;mo&gt;}&lt;/mo&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;mo&gt;≥&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;. In the sequel to this paper, we use the results of this paper to construct a correspondence between &lt;em&gt;B&lt;/em&gt;-orbits on &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;P&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 11","pages":"Article 108100"},"PeriodicalIF":0.8,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222120","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 the spectrum of residual finiteness growth functions 残差有限生长函数的谱
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-09-25 DOI: 10.1016/j.jpaa.2025.108099
Henry Bradford
In [4] Bou-Rabee and Seward constructed examples of finitely generated residually finite groups G whose residual finiteness growth function FG can be at least as fast as any prescribed function. In this note we describe a modified version of their construction, which allows us to give a complementary upper bound on FG. As such, every nondecreasing function at least exp(nlog(n)2loglog(n)1+ϵ) is close to the residual finiteness growth function of some finitely generated group. We also have similar result for the full residual finiteness growth function and for the divisibility function.
在1996年,boub - rabee和Seward构造了有限生成的剩余有限群G的例子,其剩余有限生长函数FG至少可以与任何规定函数一样快。在本文中,我们描述了它们构造的一个改进版本,它允许我们给出FG上的一个互补上界。因此,每一个至少为exp (nlog (n)2log (log)1+ λ)的非递减函数都接近于某个有限生成群的残差有限生长函数。对于完全剩余有限生长函数和可整除函数,我们也有类似的结果。
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引用次数: 0
Linear subspaces of the intersection of two quadrics via Kuznetsov component 通过库兹涅佐夫分量的两个二次曲面交点的线性子空间
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-09-19 DOI: 10.1016/j.jpaa.2025.108096
Yanjie Li , Shizhuo Zhang
Let Qi(i=1,2) be 2g dimensional quadrics in P2g+1 and let Y be the smooth intersection Q1Q2. We associate the linear subspaces in Y with vector bundles on the hyperelliptic curve C of genus g via categorical methods. As an application, we give a different proof of the classification of line bundles and stable bundles of rank 2 on hyperelliptic curves given by Desale and Ramanan. When g=3, we show that the projection functor induces a closed embedding α:YSUCs(4,h) into the moduli space of stable bundles on C of rank 4 of fixed determinant.
设Qi(i=1,2)为P2g+1中的2g次元,设Y为光滑交集Q1∩Q2。通过分类方法将Y中的线性子空间与g属的超椭圆曲线C上的向量束联系起来。作为应用,我们给出了Desale和Ramanan给出的超椭圆曲线上2阶线束和稳定束分类的另一种证明。当g=3时,我们证明了投影函子在固定行列式的4阶C上的稳定束的模空间中诱导出一个闭合嵌入α:Y→SUCs(4,h)。
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引用次数: 0
On the average degree of characters with odd or even degrees 奇数度或偶数度字符的平均度
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-09-19 DOI: 10.1016/j.jpaa.2025.108098
Kamal Aziziheris , Necat Gorentas , Zinah Naser Sulaiman
Let acd2(G) be the average degree of irreducible characters of G with odd degree. It has been proved that if acd2(G)<acd2(A5)=3, then G is a solvable group. On the other hand, let acd2(G) be the average degree of linear characters and irreducible characters of G with even degree. It has been shown that if acd2(G)<acd2(A5)=5/2, then G is a solvable group. In this paper, we improve these bounds and we show that if G is a finite group with acd2(G)<acd2(PSL(2,7))=7/2, then either G is a solvable group or G has a chief factor isomorphic to A5. Also, we prove that if G is a finite group with acd2(G)<acd2(PSL(2,8))=9/2, then either G is a solvable group or all minimal normal subgroups of G are abelian or isomorphic to A5. Clearly, these bounds are the best.
设add ' (G)为G的奇次不可约字符的平均次。证明了如果acd2 ' (G)<acd2 ' (A5)=3,则G是一个可解群。另一方面,设acd2(G)为G的偶数次线性字符和不可约字符的平均次数。证明了如果acd2(G)<acd2(A5)=5/2,则G是一个可解群。本文改进了这些边界,证明了如果G是一个有限群,且acd2 ' (G)<acd2 ' (PSL(2,7))=7/2,则G是一个可解群或G有一个主因子同态于A5。同时证明了如果G是一个有限群,且acd2(G)<acd2(PSL(2,8))=9/2,则G是一个可解群,或者G的所有最小正规子群都与A5是阿贝的或同构的。显然,这些边界是最好的。
{"title":"On the average degree of characters with odd or even degrees","authors":"Kamal Aziziheris ,&nbsp;Necat Gorentas ,&nbsp;Zinah Naser Sulaiman","doi":"10.1016/j.jpaa.2025.108098","DOIUrl":"10.1016/j.jpaa.2025.108098","url":null,"abstract":"<div><div>Let <span><math><msub><mrow><mi>acd</mi></mrow><mrow><msup><mrow><mn>2</mn></mrow><mrow><mo>′</mo></mrow></msup></mrow></msub><mo>(</mo><mi>G</mi><mo>)</mo></math></span> be the average degree of irreducible characters of <em>G</em> with odd degree. It has been proved that if <span><math><msub><mrow><mi>acd</mi></mrow><mrow><msup><mrow><mn>2</mn></mrow><mrow><mo>′</mo></mrow></msup></mrow></msub><mo>(</mo><mi>G</mi><mo>)</mo><mo>&lt;</mo><msub><mrow><mi>acd</mi></mrow><mrow><msup><mrow><mn>2</mn></mrow><mrow><mo>′</mo></mrow></msup></mrow></msub><mo>(</mo><msub><mrow><mtext>A</mtext></mrow><mrow><mn>5</mn></mrow></msub><mo>)</mo><mo>=</mo><mn>3</mn></math></span>, then <em>G</em> is a solvable group. On the other hand, let <span><math><msub><mrow><mi>acd</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><mi>G</mi><mo>)</mo></math></span> be the average degree of linear characters and irreducible characters of <em>G</em> with even degree. It has been shown that if <span><math><msub><mrow><mi>acd</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><mi>G</mi><mo>)</mo><mo>&lt;</mo><msub><mrow><mi>acd</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><msub><mrow><mtext>A</mtext></mrow><mrow><mn>5</mn></mrow></msub><mo>)</mo><mo>=</mo><mn>5</mn><mo>/</mo><mn>2</mn></math></span>, then <em>G</em> is a solvable group. In this paper, we improve these bounds and we show that if <em>G</em> is a finite group with <span><math><msub><mrow><mi>acd</mi></mrow><mrow><msup><mrow><mn>2</mn></mrow><mrow><mo>′</mo></mrow></msup></mrow></msub><mo>(</mo><mi>G</mi><mo>)</mo><mo>&lt;</mo><msub><mrow><mi>acd</mi></mrow><mrow><msup><mrow><mn>2</mn></mrow><mrow><mo>′</mo></mrow></msup></mrow></msub><mo>(</mo><mrow><mi>PSL</mi></mrow><mo>(</mo><mn>2</mn><mo>,</mo><mn>7</mn><mo>)</mo><mo>)</mo><mo>=</mo><mn>7</mn><mo>/</mo><mn>2</mn></math></span>, then either <em>G</em> is a solvable group or <em>G</em> has a chief factor isomorphic to <span><math><msub><mrow><mtext>A</mtext></mrow><mrow><mn>5</mn></mrow></msub></math></span>. Also, we prove that if <em>G</em> is a finite group with <span><math><msub><mrow><mi>acd</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><mi>G</mi><mo>)</mo><mo>&lt;</mo><msub><mrow><mi>acd</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><mrow><mi>PSL</mi></mrow><mo>(</mo><mn>2</mn><mo>,</mo><mn>8</mn><mo>)</mo><mo>)</mo><mo>=</mo><mn>9</mn><mo>/</mo><mn>2</mn></math></span>, then either <em>G</em> is a solvable group or all minimal normal subgroups of <em>G</em> are abelian or isomorphic to <span><math><msub><mrow><mtext>A</mtext></mrow><mrow><mn>5</mn></mrow></msub></math></span>. Clearly, these bounds are the best.</div></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 11","pages":"Article 108098"},"PeriodicalIF":0.8,"publicationDate":"2025-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145121044","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 the Picard number and the extension degree of period matrices of complex tori 复环面周期矩阵的皮卡德数及其可拓度
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-09-19 DOI: 10.1016/j.jpaa.2025.108097
Robert Auffarth , Jorge Duque Franco
The rank ρ of the Néron-Severi group of a complex torus X of dimension g satisfies 0ρg2=h1,1. The degree d of the extension field generated over Q by the entries of a period matrix of X imposes constraints on its Picard number ρ and, consequently, on the structure of X. In this paper, we show that when d is 2, 3, or 4, the Picard number ρ is necessarily large. Moreover, for an abelian variety X of dimension g with d=3, we establish a structure-type result: X must be isogenous to Eg, where E is an elliptic curve without complex multiplication. In this case, the Picard number satisfies ρ(X)=g(g+1)2. As a byproduct, we obtain that if d is odd, then ρ(X)g(g+1)2.
g维的复环体X的nsamron - severi群的秩ρ满足0≤ρ≤g2=h1,1。由周期矩阵X的元素在Q上生成的扩展域的阶d对它的皮卡德数ρ施加了约束,从而对X的结构施加了约束。在本文中,我们证明了当d为2、3或4时,皮卡德数ρ必然很大。此外,对于d=3的维数为g的阿贝尔变量X,我们建立了一个结构型结果:X必须同Eg同构,其中E是一条没有复乘法的椭圆曲线。在这种情况下,皮卡德数满足ρ(X)=g(g+1)2。作为副产品,我们得到如果d是奇数,那么ρ(X)≤g(g+1)2。
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引用次数: 0
On isotropy groups of quantum plane 关于量子平面的各向同性群
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-09-17 DOI: 10.1016/j.jpaa.2025.108095
Adriano De Santana , Rene Baltazar , Robson Vinciguerra , Wilian De Araujo
This paper investigates the isotropy groups of derivations on the Quantum Plane kq[x,y], defined by the relation yx=qxy, where qk, with q21. The main goal is to determine the automorphisms of the Quantum Plane that commutes with a fixed derivation δ. We describe conditions under which the isotropy group Autδ(A) is trivial, finite, or infinite, depending on the structure of δ and whether q is a root of unity: additionally, we present the structure of the group in the finite case. A key tool is the analysis of polynomial equations of the form μ1aμ2b=1, arising from monomials in the inner part of δ. We also make explicit which finite subgroups of Aut(kq[x,y]) are isotropy groups of some derivation: either q root of unity or not. Techniques from algebraic geometry, such as intersection multiplicity, are also employed in the classification of the finite case.
研究了量子平面kq[x,y]上的导数的各向同性群,由关系yx=qxy定义,其中q∈k _,且q2≠1。主要目标是确定量子平面的自同构,该量子平面具有固定的导数δ。我们描述了各向同性群Autδ(A)是平凡的、有限的或无限的条件,这取决于δ的结构和q是否为单位的根;另外,我们给出了有限情况下群的结构。一个关键的工具是分析μ1aμ2b=1形式的多项式方程,这些方程是由δ内部的单项式引起的。我们还明确了Aut(kq[x,y])的有限子群是具有某种导数的各向同性群:q是否是单位根。从代数几何的技术,如交集多重性,也被用于有限情况的分类。
{"title":"On isotropy groups of quantum plane","authors":"Adriano De Santana ,&nbsp;Rene Baltazar ,&nbsp;Robson Vinciguerra ,&nbsp;Wilian De Araujo","doi":"10.1016/j.jpaa.2025.108095","DOIUrl":"10.1016/j.jpaa.2025.108095","url":null,"abstract":"<div><div>This paper investigates the isotropy groups of derivations on the Quantum Plane <span><math><msub><mrow><mi>k</mi></mrow><mrow><mi>q</mi></mrow></msub><mo>[</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>]</mo></math></span>, defined by the relation <span><math><mi>y</mi><mi>x</mi><mo>=</mo><mi>q</mi><mi>x</mi><mi>y</mi></math></span>, where <span><math><mi>q</mi><mo>∈</mo><msup><mrow><mi>k</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span>, with <span><math><msup><mrow><mi>q</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>≠</mo><mn>1</mn></math></span>. The main goal is to determine the automorphisms of the Quantum Plane that commutes with a fixed derivation <em>δ</em>. We describe conditions under which the isotropy group <span><math><msub><mrow><mtext>Aut</mtext></mrow><mrow><mi>δ</mi></mrow></msub><mo>(</mo><mi>A</mi><mo>)</mo></math></span> is trivial, finite, or infinite, depending on the structure of <em>δ</em> and whether <em>q</em> is a root of unity: additionally, we present the structure of the group in the finite case. A key tool is the analysis of polynomial equations of the form <span><math><msubsup><mrow><mi>μ</mi></mrow><mrow><mn>1</mn></mrow><mrow><mi>a</mi></mrow></msubsup><msubsup><mrow><mi>μ</mi></mrow><mrow><mn>2</mn></mrow><mrow><mi>b</mi></mrow></msubsup><mo>=</mo><mn>1</mn></math></span>, arising from monomials in the inner part of <em>δ</em>. We also make explicit which finite subgroups of <span><math><mi>Aut</mi><mo>(</mo><msub><mrow><mi>k</mi></mrow><mrow><mi>q</mi></mrow></msub><mo>[</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>]</mo><mo>)</mo></math></span> are isotropy groups of some derivation: either <em>q</em> root of unity or not. Techniques from algebraic geometry, such as intersection multiplicity, are also employed in the classification of the finite case.</div></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 11","pages":"Article 108095"},"PeriodicalIF":0.8,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145109500","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
Normalizer of twisted Chevalley groups over commutative rings 交换环上扭曲Chevalley群的归一化器
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-09-15 DOI: 10.1016/j.jpaa.2025.108094
Shripad M. Garge , Deep H. Makadiya
Let R be a commutative ring with unity. Consider the twisted Chevalley group Gπ,σ(Φ,R) of type Φ over R and its elementary subgroup Eπ,σ(Φ,R). This paper investigates the normalizers of Eπ,σ(Φ,R) and Gπ,σ(Φ,R) in the larger group Gπ,σ(Φ,S), where S is an extension ring of R. We establish that under certain conditions on R these normalizers coincide. Moreover, in the case of adjoint type groups, we show that they are precisely equal to Gπ,σ(Φ,R).
设R是一个有单位的交换环。考虑R上Φ型的扭曲Chevalley群Gπ,σ(Φ,R)及其初等子群Eπ,σ ' (Φ,R)。本文研究了大群Gπ,σ(Φ,S)中ε,σ′(Φ,R)和Gπ,σ(Φ,R)的归一化器,其中S是R的一个扩展环。在一定条件下,我们证明了这些归一化器在R上是一致的。此外,对于伴随型群,我们证明了它们精确地等于Gπ,σ(Φ,R)。
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引用次数: 0
Noncommutative fibre bundles via bimodules 通过双模的非交换纤维束
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-09-12 DOI: 10.1016/j.jpaa.2025.108088
Edwin J. Beggs, James E. Blake
We construct a Leray-Serre spectral sequence for fibre bundles for de Rham sheaf cohomology on noncommutative algebras. The morphisms are bimodules with zero-curvature extendable bimodule connections. This generalises definitions involving differentiable algebra maps to differentiable completely positive maps by using the KSGNS construction and Hilbert C-bimodules with bimodule connections. We give examples of noncommutative fibre bundles, involving group algebras, matrix algebras, and the quantum torus.
在非交换代数上构造了de Rham轴上同调的纤维束的Leray-Serre谱序列。态射是具有零曲率可扩展双模连接的双模。利用KSGNS构造和具有双模连接的Hilbert C - C -双模,将涉及可微代数映射的定义推广到可微的完全正映射。我们给出了非交换纤维束的例子,涉及群代数、矩阵代数和量子环面。
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引用次数: 0
Classifying prime graphs of finite groups – a methodical approach 有限群素数图的分类-一种系统的方法
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-09-11 DOI: 10.1016/j.jpaa.2025.108089
Thomas Michael Keller , Gavin Pettigrew , Saskia Solotko , Lixin Zheng
For a finite group G, the vertices of the prime graph Γ(G) are the primes that divide |G|, and two vertices p and q are adjacent if and only if there is an element of order pq in G. Prime graphs of solvable groups as well as groups whose noncyclic composition factors have order divisible by exactly three distinct primes have been classified in graph-theoretic terms. In this paper, we begin to develop a general theory on the existence of edges in the prime graph of an arbitrary T-solvable group, that is, a group whose composition factors are cyclic or isomorphic to a fixed nonabelian simple group T. We then apply these results to classify the prime graphs of T-solvable groups for, in a suitable sense, most T such that |T| has exactly four prime divisors. We find that these groups almost always have a 3-colorable prime graph complement containing few possible triangles.
对于有限群G,素数图Γ(G)的顶点是能整除|G|的素数,且两个顶点p和q相邻当且仅当G中存在pq阶元素时。可解群的素数图以及其非循环组成因子的阶可整除恰好三个不同素数的群的素数图已经用图论的方式进行了分类。在本文中,我们开始发展关于任意T可解群的素数图中边的存在性的一般理论,即组成因子是循环或同构于一个固定的非阿贝单群T的群。然后应用这些结果对T可解群的素数图进行分类,在适当的意义上,大多数T使得|T|有四个素数因数。我们发现这些群几乎总是有一个包含少量可能三角形的3色素数图补。
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引用次数: 0
New formulae for the Schur elements of the cyclotomic Hecke algebra of type G(ℓ,1,n) G(r,1,n)型切环Hecke代数的Schur元的新公式
IF 0.8 2区 数学 Q2 MATHEMATICS Pub Date : 2025-09-10 DOI: 10.1016/j.jpaa.2025.108090
Jun Hu , Huansheng Li , Shuo Li
In this paper, we use the cyclotomic Mackey decomposition and branching rules of the seminormal bases of the semisimple cyclotomic Hecke algebras of type G(,1,n) to give a new approach to computing the Schur element sλ of H,n for each -partition λP,n. Our formulae give a simple recursive relation between the Schur element sλ and the Schur element sλ(n1) of H,n1, where λ(n1):=Shape((tλ)(n1)). We give our main results for both the non-degenerate and the degenerate cyclotomic Hecke algebras of type G(,1,n). The formulae of the Schur element that we derived are different superficially from all the known formulae in the literature.
本文利用G(r, 1,n)型半简单切环Hecke代数的半正规基的切环Mackey分解和分支规则,给出了计算H (r, n)的每一个划分λ∈P (r, n)的Schur元λ的一种新方法。我们的公式给出了舒尔元sλ与H,n - 1的舒尔元sλ↓≤(n−1)之间的简单递归关系,其中λ↓≤(n−1):=Shape((tλ)↓≤(n−1))。我们给出了G(r,1,n)型的非简并和简并切环Hecke代数的主要结果。从表面上看,我们推导出的舒尔元公式与文献中所有已知的舒尔元公式不同。
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Journal of Pure and Applied Algebra
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