Pub Date : 2025-11-11DOI: 10.1016/j.jalgebra.2025.10.050
Gopal Sharma, Sampat Sharma
<div><div>In this article, we prove the following results:<ul><li><span>(1).</span><span><div>Let <em>R</em> be a smooth affine algebra of dimension 3 over an algebraically closed field <em>K</em> with <span><math><mn>3</mn><mo>!</mo><mo>∈</mo><mi>K</mi></math></span>, then we show that <span><math><msub><mrow><mtext>Um</mtext></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo><mo>=</mo><msub><mrow><mi>e</mi></mrow><mrow><mn>1</mn></mrow></msub><msub><mrow><mtext>Sp</mtext></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span> and <span><math><msub><mrow><mtext>Um</mtext></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>[</mo><mi>X</mi><mo>]</mo><mo>)</mo><mo>=</mo><msub><mrow><mi>e</mi></mrow><mrow><mn>1</mn></mrow></msub><msub><mrow><mtext>Sp</mtext></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>[</mo><mi>X</mi><mo>]</mo><mo>)</mo></math></span>.</div></span></li><li><span>(2).</span><span><div>We also show that if <em>R</em> is a smooth affine algebra of dimension 4 over an algebraically closed field <em>K</em> with <span><math><mn>4</mn><mo>!</mo><mo>∈</mo><mi>K</mi></math></span>, and assume that <span><math><msub><mrow><mtext>W</mtext></mrow><mrow><mi>E</mi></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span> is divisible, then <span><math><msub><mrow><mtext>Um</mtext></mrow><mrow><mn>3</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo><mo>=</mo><msub><mrow><mi>e</mi></mrow><mrow><mn>1</mn></mrow></msub><msub><mrow><mtext>SL</mtext></mrow><mrow><mn>3</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span>. As a consequence it is shown that if <em>R</em> is a smooth affine algebra of dimension 4 over an algebraically closed field <em>K</em> with <span><math><mn>4</mn><mo>!</mo><mo>∈</mo><mi>K</mi></math></span>, and assume that <span><math><msub><mrow><mtext>W</mtext></mrow><mrow><mi>E</mi></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span> is divisible, then <span><math><msub><mrow><mtext>Um</mtext></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo><mo>=</mo><msub><mrow><mi>e</mi></mrow><mrow><mn>1</mn></mrow></msub><msub><mrow><mtext>Sp</mtext></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span>.</div></span></li><li><span>(3).</span><span><div>We show that if <em>R</em> is a local ring of dimension 3 with <span><math><mfrac><mrow><mn>1</mn></mrow><mrow><mn>3</mn><mo>!</mo></mrow></mfrac><mo>∈</mo><mi>R</mi></math></span>. Then <span><math><msub><mrow><mtext>Um</mtext></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>[</mo><mi>X</mi><mo>]</mo><mo>)</mo><mo>=</mo><msub><mrow><mi>e</mi></mrow><mrow><mn>1</mn></mrow></msub><msub><mrow><mtext>Sp</mtext></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>[</mo><mi>X</mi><mo>]</mo><mo>)</mo></math></span>.</div></span></li><li><span>(4).</span><span><div>We also show that if <span><math><mi>R</mi><mo>=</mo><msub><mrow><mo>⊕</mo></mrow><mrow><mi>i<
{"title":"Symplectic completion over smooth affine algebras","authors":"Gopal Sharma, Sampat Sharma","doi":"10.1016/j.jalgebra.2025.10.050","DOIUrl":"10.1016/j.jalgebra.2025.10.050","url":null,"abstract":"<div><div>In this article, we prove the following results:<ul><li><span>(1).</span><span><div>Let <em>R</em> be a smooth affine algebra of dimension 3 over an algebraically closed field <em>K</em> with <span><math><mn>3</mn><mo>!</mo><mo>∈</mo><mi>K</mi></math></span>, then we show that <span><math><msub><mrow><mtext>Um</mtext></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo><mo>=</mo><msub><mrow><mi>e</mi></mrow><mrow><mn>1</mn></mrow></msub><msub><mrow><mtext>Sp</mtext></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span> and <span><math><msub><mrow><mtext>Um</mtext></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>[</mo><mi>X</mi><mo>]</mo><mo>)</mo><mo>=</mo><msub><mrow><mi>e</mi></mrow><mrow><mn>1</mn></mrow></msub><msub><mrow><mtext>Sp</mtext></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>[</mo><mi>X</mi><mo>]</mo><mo>)</mo></math></span>.</div></span></li><li><span>(2).</span><span><div>We also show that if <em>R</em> is a smooth affine algebra of dimension 4 over an algebraically closed field <em>K</em> with <span><math><mn>4</mn><mo>!</mo><mo>∈</mo><mi>K</mi></math></span>, and assume that <span><math><msub><mrow><mtext>W</mtext></mrow><mrow><mi>E</mi></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span> is divisible, then <span><math><msub><mrow><mtext>Um</mtext></mrow><mrow><mn>3</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo><mo>=</mo><msub><mrow><mi>e</mi></mrow><mrow><mn>1</mn></mrow></msub><msub><mrow><mtext>SL</mtext></mrow><mrow><mn>3</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span>. As a consequence it is shown that if <em>R</em> is a smooth affine algebra of dimension 4 over an algebraically closed field <em>K</em> with <span><math><mn>4</mn><mo>!</mo><mo>∈</mo><mi>K</mi></math></span>, and assume that <span><math><msub><mrow><mtext>W</mtext></mrow><mrow><mi>E</mi></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span> is divisible, then <span><math><msub><mrow><mtext>Um</mtext></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo><mo>=</mo><msub><mrow><mi>e</mi></mrow><mrow><mn>1</mn></mrow></msub><msub><mrow><mtext>Sp</mtext></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span>.</div></span></li><li><span>(3).</span><span><div>We show that if <em>R</em> is a local ring of dimension 3 with <span><math><mfrac><mrow><mn>1</mn></mrow><mrow><mn>3</mn><mo>!</mo></mrow></mfrac><mo>∈</mo><mi>R</mi></math></span>. Then <span><math><msub><mrow><mtext>Um</mtext></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>[</mo><mi>X</mi><mo>]</mo><mo>)</mo><mo>=</mo><msub><mrow><mi>e</mi></mrow><mrow><mn>1</mn></mrow></msub><msub><mrow><mtext>Sp</mtext></mrow><mrow><mn>4</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>[</mo><mi>X</mi><mo>]</mo><mo>)</mo></math></span>.</div></span></li><li><span>(4).</span><span><div>We also show that if <span><math><mi>R</mi><mo>=</mo><msub><mrow><mo>⊕</mo></mrow><mrow><mi>i<","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"690 ","pages":"Pages 20-36"},"PeriodicalIF":0.8,"publicationDate":"2025-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145519339","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}
Pub Date : 2025-11-10DOI: 10.1016/j.jalgebra.2025.10.035
James P. Cossey
Let G be a finite group, let p be a fixed prime, and let B be a p-block of G. The (ordinary) Brauer graph is defined to be the graph whose vertices are labeled by , and χ and ψ are adjacent if χ and ψ have a Brauer character in common. Recent results suggest that, unlike for instance symmetric groups, the Brauer graphs of blocks of solvable groups should be ‘‘very connected” in some sense. In this paper, we continue that theme, and show that a certain ‘‘local condition” on the graph guarantees global information. In particular, we show that if has a vertex of degree one, then the defect group D of B is elementary abelian, the graph has diameter at most three, each Brauer character has a unique lift, and the vertices corresponding to the non-lifts in form a complete subgraph.
{"title":"Brauer graphs of solvable groups with a vertex of degree one","authors":"James P. Cossey","doi":"10.1016/j.jalgebra.2025.10.035","DOIUrl":"10.1016/j.jalgebra.2025.10.035","url":null,"abstract":"<div><div>Let <em>G</em> be a finite group, let <em>p</em> be a fixed prime, and let <em>B</em> be a <em>p</em>-block of <em>G</em>. The (ordinary) Brauer graph <span><math><mi>Γ</mi><mo>(</mo><mi>B</mi><mo>)</mo></math></span> is defined to be the graph whose vertices are labeled by <span><math><mtext>Irr</mtext><mo>(</mo><mi>B</mi><mo>)</mo></math></span>, and <em>χ</em> and <em>ψ</em> are adjacent if <em>χ</em> and <em>ψ</em> have a Brauer character <span><math><mi>φ</mi><mo>∈</mo><msub><mrow><mtext>IBr</mtext></mrow><mrow><mi>p</mi></mrow></msub><mo>(</mo><mi>B</mi><mo>)</mo></math></span> in common. Recent results suggest that, unlike for instance symmetric groups, the Brauer graphs of blocks of solvable groups should be ‘‘very connected” in some sense. In this paper, we continue that theme, and show that a certain ‘‘local condition” on the graph guarantees global information. In particular, we show that if <span><math><mi>Γ</mi><mo>(</mo><mi>B</mi><mo>)</mo></math></span> has a vertex of degree one, then the defect group <em>D</em> of <em>B</em> is elementary abelian, the graph has diameter at most three, each Brauer character has a unique lift, and the vertices corresponding to the non-lifts in <span><math><mtext>Irr</mtext><mo>(</mo><mi>B</mi><mo>)</mo></math></span> form a complete subgraph.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"690 ","pages":"Pages 1-19"},"PeriodicalIF":0.8,"publicationDate":"2025-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145493114","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}
Pub Date : 2025-10-31DOI: 10.1016/j.jalgebra.2025.10.033
Riccardo Aragona, Norberto Gavioli, Giuseppe Nozzi
In this work, we give a description of the structure of the normal subgroups of a Sylow p-subgroup of , showing that they contain a term from the lower central series with bounded index. To this end, we explicitly determine the terms of the upper and the lower central series of . We provide a similar description of these series in the Lie algebra associated to , giving a new proof of the equality of their terms in both the group and algebra contexts. Finally, we calculate the growth of the normalizer chain starting from an elementary abelian regular subgroup of .
{"title":"Normality conditions in the Sylow p-subgroup of Sym(pn) and its associated Lie algebra","authors":"Riccardo Aragona, Norberto Gavioli, Giuseppe Nozzi","doi":"10.1016/j.jalgebra.2025.10.033","DOIUrl":"10.1016/j.jalgebra.2025.10.033","url":null,"abstract":"<div><div>In this work, we give a description of the structure of the normal subgroups of a Sylow <em>p</em>-subgroup <span><math><msub><mrow><mi>W</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> of <span><math><mi>Sym</mi><mo>(</mo><msup><mrow><mi>p</mi></mrow><mrow><mi>n</mi></mrow></msup><mo>)</mo></math></span>, showing that they contain a term from the lower central series with bounded index. To this end, we explicitly determine the terms of the upper and the lower central series of <span><math><msub><mrow><mi>W</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span>. We provide a similar description of these series in the Lie algebra associated to <span><math><msub><mrow><mi>W</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span>, giving a new proof of the equality of their terms in both the group and algebra contexts. Finally, we calculate the growth of the normalizer chain starting from an elementary abelian regular subgroup of <span><math><msub><mrow><mi>W</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span>.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"689 ","pages":"Pages 747-763"},"PeriodicalIF":0.8,"publicationDate":"2025-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145464233","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}
Pub Date : 2025-10-31DOI: 10.1016/j.jalgebra.2025.10.034
Bachuki Mesablishvili
Morita theory for quantales is developed. The main result of the paper is a characterization of those quantaloids (categories enriched in the symmetric monoidal closed category of sup-lattices) that are equivalent to module categories over quantales. Based on this characterization, necessary and sufficient conditions are derived for two quantales to be Morita-equivalent, i.e. have equivalent module categories. As an application, it is shown that the category of internal sup-lattices in a Grothendieck topos is equivalent to the module category over a suitable chosen ordinary quantale.
{"title":"Morita theory for quantales","authors":"Bachuki Mesablishvili","doi":"10.1016/j.jalgebra.2025.10.034","DOIUrl":"10.1016/j.jalgebra.2025.10.034","url":null,"abstract":"<div><div>Morita theory for quantales is developed. The main result of the paper is a characterization of those quantaloids (categories enriched in the symmetric monoidal closed category of sup-lattices) that are equivalent to module categories over quantales. Based on this characterization, necessary and sufficient conditions are derived for two quantales to be Morita-equivalent, i.e. have equivalent module categories. As an application, it is shown that the category of internal sup-lattices in a Grothendieck topos is equivalent to the module category over a suitable chosen ordinary quantale.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"689 ","pages":"Pages 764-784"},"PeriodicalIF":0.8,"publicationDate":"2025-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145462984","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}
Pub Date : 2025-10-30DOI: 10.1016/j.jalgebra.2025.10.016
Heiko Dietrich, Melissa Lee, Anthony Pisani, Tomasz Popiel
Seysen's Python package mmgroup provides functionality for fast computations within the sporadic simple group , the Monster. The aim of this work is to present an mmgroup database of maximal subgroups of : for each conjugacy class of maximal subgroups in , we construct explicit group elements in mmgroup and prove that these elements generate a group in . Our generators and the computations verifying correctness are available in accompanying code. The maximal subgroups of have been classified in a number of papers spanning several decades; our work constitutes an independent verification of the constructions in these papers. We also correct the claim that has a maximal subgroup , and hence identify a new maximal subgroup .
{"title":"Explicit construction of the maximal subgroups of the Monster","authors":"Heiko Dietrich, Melissa Lee, Anthony Pisani, Tomasz Popiel","doi":"10.1016/j.jalgebra.2025.10.016","DOIUrl":"10.1016/j.jalgebra.2025.10.016","url":null,"abstract":"<div><div>Seysen's Python package <span>mmgroup</span> provides functionality for fast computations within the sporadic simple group <span><math><mi>M</mi></math></span>, the Monster. The aim of this work is to present an <span>mmgroup</span> database of maximal subgroups of <span><math><mi>M</mi></math></span>: for each conjugacy class <span><math><mi>C</mi></math></span> of maximal subgroups in <span><math><mi>M</mi></math></span>, we construct explicit group elements in <span>mmgroup</span> and prove that these elements generate a group in <span><math><mi>C</mi></math></span>. Our generators and the computations verifying correctness are available in accompanying code. The maximal subgroups of <span><math><mi>M</mi></math></span> have been classified in a number of papers spanning several decades; our work constitutes an independent verification of the constructions in these papers. We also correct the claim that <span><math><mi>M</mi></math></span> has a maximal subgroup <span><math><msub><mrow><mi>PSL</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><mn>59</mn><mo>)</mo></math></span>, and hence identify a new maximal subgroup <span><math><mn>59</mn><mo>:</mo><mn>29</mn></math></span>.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"689 ","pages":"Pages 862-895"},"PeriodicalIF":0.8,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145464238","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}
Pub Date : 2025-10-30DOI: 10.1016/j.jalgebra.2025.10.018
Jürgen Müller
We determine the ordinary character of the projective cover of the trivial module in characteristic 11 for the sporadic simple Janko group , and answer the question posed in the title.
我们确定了散乱的简单Janko群J4的特征11平凡模的投影盖的一般性质,并回答了题目中的问题。
{"title":"Is the projective cover of the trivial module in characteristic 11 for the sporadic simple Janko group J4 a permutation module?","authors":"Jürgen Müller","doi":"10.1016/j.jalgebra.2025.10.018","DOIUrl":"10.1016/j.jalgebra.2025.10.018","url":null,"abstract":"<div><div>We determine the ordinary character of the projective cover of the trivial module in characteristic 11 for the sporadic simple Janko group <span><math><msub><mrow><mi>J</mi></mrow><mrow><mn>4</mn></mrow></msub></math></span>, and answer the question posed in the title.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"689 ","pages":"Pages 896-911"},"PeriodicalIF":0.8,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145464236","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}
Pub Date : 2025-10-30DOI: 10.1016/j.jalgebra.2025.10.027
Ramla Abdellatif , Mabud Ali Sarkar
In this paper, we construct a class of 2-dimensional formal groups over that provide a higher-dimensional analogue of the usual 1-dimensional Lubin-Tate formal groups, then we initiate the study of the extensions generated by their -torsion points. For instance, we prove that the coordinates of the -torsion points of such a formal group generate an abelian extension over a certain unramified extension of , and we study some ramification properties of these abelian extensions. In particular, we prove that the extension generated by the coordinates of the p-torsion points is in general totally ramified.
{"title":"Constructing 2-dimensional Lubin-Tate formal groups over Zp (I)","authors":"Ramla Abdellatif , Mabud Ali Sarkar","doi":"10.1016/j.jalgebra.2025.10.027","DOIUrl":"10.1016/j.jalgebra.2025.10.027","url":null,"abstract":"<div><div>In this paper, we construct a class of 2-dimensional formal groups over <span><math><msub><mrow><mi>Z</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span> that provide a higher-dimensional analogue of the usual 1-dimensional Lubin-Tate formal groups, then we initiate the study of the extensions generated by their <span><math><msup><mrow><mi>p</mi></mrow><mrow><mi>n</mi></mrow></msup></math></span>-torsion points. For instance, we prove that the coordinates of the <span><math><msup><mrow><mi>p</mi></mrow><mrow><mo>∞</mo></mrow></msup></math></span>-torsion points of such a formal group generate an abelian extension over a certain unramified extension of <span><math><msub><mrow><mi>Q</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span>, and we study some ramification properties of these abelian extensions. In particular, we prove that the extension generated by the coordinates of the <em>p</em>-torsion points is in general totally ramified.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"692 ","pages":"Pages 205-237"},"PeriodicalIF":0.8,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145798709","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}
Pub Date : 2025-10-30DOI: 10.1016/j.jalgebra.2025.10.032
Gabriel Navarro
We determine the fields of values of the Isaacs' head characters of a finite solvable group.
我们确定了有限可解群的艾萨克头字符值的域。
{"title":"The fields of values of the Isaacs' head characters","authors":"Gabriel Navarro","doi":"10.1016/j.jalgebra.2025.10.032","DOIUrl":"10.1016/j.jalgebra.2025.10.032","url":null,"abstract":"<div><div>We determine the fields of values of the Isaacs' head characters of a finite solvable group.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"689 ","pages":"Pages 739-746"},"PeriodicalIF":0.8,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145464239","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}
Pub Date : 2025-10-30DOI: 10.1016/j.jalgebra.2025.10.026
Shoumin Liu, Yuxiang Wang
Let W be a finite Coxeter group with Coxeter generating set , and ρ be a complex finite dimensional representation of W. The characteristic polynomial of ρ is defined as where I is the identity operator. In this paper, we show the existence of a combinatorics structure within W, and thereby prove that for any two complex finite dimensional representations and of W, if and only if .
{"title":"Characteristic polynomials and some combinatorics for finite Coxeter groups","authors":"Shoumin Liu, Yuxiang Wang","doi":"10.1016/j.jalgebra.2025.10.026","DOIUrl":"10.1016/j.jalgebra.2025.10.026","url":null,"abstract":"<div><div>Let <em>W</em> be a finite Coxeter group with Coxeter generating set <span><math><mi>S</mi><mo>=</mo><mo>{</mo><msub><mrow><mi>s</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><mo>…</mo><mo>,</mo><msub><mrow><mi>s</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>}</mo></math></span>, and <em>ρ</em> be a complex finite dimensional representation of <em>W</em>. The characteristic polynomial of <em>ρ</em> is defined as<span><span><span><math><mi>d</mi><mo>(</mo><mi>S</mi><mo>,</mo><mi>ρ</mi><mo>)</mo><mo>=</mo><mi>det</mi><mo></mo><mo>[</mo><msub><mrow><mi>x</mi></mrow><mrow><mn>0</mn></mrow></msub><mi>I</mi><mo>+</mo><msub><mrow><mi>x</mi></mrow><mrow><mn>1</mn></mrow></msub><mi>ρ</mi><mo>(</mo><msub><mrow><mi>s</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>)</mo><mo>+</mo><mo>⋯</mo><mo>+</mo><msub><mrow><mi>x</mi></mrow><mrow><mi>n</mi></mrow></msub><mi>ρ</mi><mo>(</mo><msub><mrow><mi>s</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>)</mo><mo>]</mo><mo>,</mo></math></span></span></span> where <em>I</em> is the identity operator. In this paper, we show the existence of a combinatorics structure within <em>W</em>, and thereby prove that for any two complex finite dimensional representations <span><math><msub><mrow><mi>ρ</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>ρ</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> of <em>W</em>, <span><math><mi>d</mi><mo>(</mo><mi>S</mi><mo>,</mo><msub><mrow><mi>ρ</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>)</mo><mo>=</mo><mi>d</mi><mo>(</mo><mi>S</mi><mo>,</mo><msub><mrow><mi>ρ</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>)</mo></math></span> if and only if <span><math><msub><mrow><mi>ρ</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>≅</mo><msub><mrow><mi>ρ</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"689 ","pages":"Pages 629-655"},"PeriodicalIF":0.8,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145464237","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}
Pub Date : 2025-10-29DOI: 10.1016/j.jalgebra.2025.10.023
Gert-Martin Greuel, Gerhard Pfister
We give a simple proof of the splitting lemma in singularity theory, also known as generalized Morse lemma, for formal power series over arbitrary fields. Our proof for the uniqueness of the residual part in any characteristic is new and was previously unknown in characteristic two. Beyond the formal case, we give proofs for algebraic power series and for convergent real and complex analytic power series, which are new for non-isolated singularities.
{"title":"The splitting lemma in any characteristic","authors":"Gert-Martin Greuel, Gerhard Pfister","doi":"10.1016/j.jalgebra.2025.10.023","DOIUrl":"10.1016/j.jalgebra.2025.10.023","url":null,"abstract":"<div><div>We give a simple proof of the splitting lemma in singularity theory, also known as generalized Morse lemma, for formal power series over arbitrary fields. Our proof for the uniqueness of the residual part in any characteristic is new and was previously unknown in characteristic two. Beyond the formal case, we give proofs for algebraic power series and for convergent real and complex analytic power series, which are new for non-isolated singularities.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"689 ","pages":"Pages 610-628"},"PeriodicalIF":0.8,"publicationDate":"2025-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145412606","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}