{"title":"The pro-nilpotent Lawrence-Krammer-Bigelow representation","authors":"Martin Palmer , Arthur Soulié","doi":"10.1016/j.jpaa.2025.107952","DOIUrl":"10.1016/j.jpaa.2025.107952","url":null,"abstract":"<div><div>We construct a 3-variable enrichment of the Lawrence-Krammer-Bigelow (LKB) representation of the braid groups, which is the limit of a pro-nilpotent tower of representations having the original LKB representation as its bottom layer. We also construct analogous pro-nilpotent towers of representations of surface braid groups and loop braid groups.</div></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 6","pages":"Article 107952"},"PeriodicalIF":0.7,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143738976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The isomorphism problem for rational group algebras of finite metacyclic groups","authors":"Àngel García-Blázquez, Ángel del Río","doi":"10.1016/j.jpaa.2025.107951","DOIUrl":"10.1016/j.jpaa.2025.107951","url":null,"abstract":"<div><div>We prove that if two finite metacyclic groups have isomorphic rational group algebras, then they are isomorphic. This contributes to understand where the line separating positive and negative solutions to the Isomorphism Problem for group algebras lies.</div></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 6","pages":"Article 107951"},"PeriodicalIF":0.7,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143683882","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}
Dan Ciubotaru , Hendrik De Bie , Marcelo De Martino , Roy Oste
{"title":"Deformations of unitary Howe dual pairs","authors":"Dan Ciubotaru , Hendrik De Bie , Marcelo De Martino , Roy Oste","doi":"10.1016/j.jpaa.2025.107948","DOIUrl":"10.1016/j.jpaa.2025.107948","url":null,"abstract":"<div><div>We study deformations of the Howe pairs <span><math><mo>(</mo><mi>U</mi><mo>(</mo><mi>n</mi><mo>)</mo><mo>,</mo><mi>u</mi><mo>(</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>)</mo><mo>)</mo></math></span> and <span><math><mo>(</mo><mi>U</mi><mo>(</mo><mi>n</mi><mo>)</mo><mo>,</mo><mi>u</mi><mo>(</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>|</mo><mn>1</mn><mo>)</mo><mo>)</mo></math></span> to the context of a rational Cherednik algebra <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>1</mn><mo>,</mo><mi>c</mi></mrow></msub><mo>(</mo><mi>G</mi><mo>,</mo><mi>E</mi><mo>)</mo></math></span> associated with a real reflection group <em>G</em> acting on a real vector space <em>E</em> of even dimension. For each pair, we show that the Lie (super)algebra structure of one partner is preserved under the deformation, which leads to a joint decomposition of the standard module or its tensor product with a spinor space. For the case where <em>E</em> is two-dimensional and <em>G</em> is a dihedral group, we provide complete descriptions for the deformed pair and the relevant joint-decomposition.</div></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 7","pages":"Article 107948"},"PeriodicalIF":0.7,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143776895","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}
{"title":"Generalized (co)homology of symmetric quandles over homogeneous Beck modules","authors":"Biswadeep Karmakar, Deepanshi Saraf, Mahender Singh","doi":"10.1016/j.jpaa.2025.107956","DOIUrl":"10.1016/j.jpaa.2025.107956","url":null,"abstract":"<div><div>A quandle equipped with a good involution is referred to as symmetric. It is known that the cohomology of symmetric quandles gives rise to strong cocycle invariants for classical and surface links, even when they are not necessarily oriented. In this paper, we introduce the category of symmetric quandle modules and prove that these modules completely determine the Beck modules in the category of symmetric quandles. Consequently, this establishes suitable coefficient objects for constructing appropriate (co)homology theories. We develop an extension theory of modules over symmetric quandles, and propose a generalized (co)homology theory for symmetric quandles with coefficients in a homogeneous Beck module, which also recovers the symmetric quandle (co)homology developed by Kamada and Oshiro (2010) <span><span>[16]</span></span>. Our constructions also apply to symmetric racks. We conclude by establishing an explicit isomorphism between the second cohomology of a symmetric quandle and the first cohomology of its associated group.</div></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 6","pages":"Article 107956"},"PeriodicalIF":0.7,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143683880","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}
{"title":"Infinitely many new sequences of surfaces of general type with maximal Picard number converging to the Severi line","authors":"Nguyen Bin , Vicente Lorenzo","doi":"10.1016/j.jpaa.2025.107957","DOIUrl":"10.1016/j.jpaa.2025.107957","url":null,"abstract":"<div><div>Examples of algebraic surfaces of general type with maximal Picard number are not abundant in the literature. Moreover, most known examples either possess low invariants, lie near the Noether line <span><math><msup><mrow><mi>K</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>=</mo><mn>2</mn><mi>χ</mi><mo>−</mo><mn>6</mn></math></span> or are somewhat scattered. A notable exception is Persson's sequence of double covers of the projective plane with maximal Picard number, whose invariants converge to the Severi line <span><math><msup><mrow><mi>K</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>=</mo><mn>4</mn><mi>χ</mi></math></span>. This note is devoted to the construction of infinitely many new sequences of surfaces of general type with maximal Picard number whose invariants converge to the Severi line.</div></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 6","pages":"Article 107957"},"PeriodicalIF":0.7,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143696108","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}
{"title":"The based rings of two-sided cells in an affine Weyl group of type B˜3, III","authors":"Yannan Qiu","doi":"10.1016/j.jpaa.2025.107950","DOIUrl":"10.1016/j.jpaa.2025.107950","url":null,"abstract":"<div><div>We compute the based ring of the two-sided cell corresponding to the unipotent class in <span><math><mi>S</mi><msub><mrow><mi>p</mi></mrow><mrow><mn>6</mn></mrow></msub><mo>(</mo><mi>C</mi><mo>)</mo></math></span> with Jordan blocks (2211). The result also verifies Lusztig's conjecture on the structure of the based rings of the two-sided cells of an affine Weyl group.</div></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 6","pages":"Article 107950"},"PeriodicalIF":0.7,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143738975","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}
Phùng Hô Hai , Hop D. Nguyen , João Pedro dos Santos
{"title":"Fiber criteria for flatness and homomorphisms of flat affine group schemes","authors":"Phùng Hô Hai , Hop D. Nguyen , João Pedro dos Santos","doi":"10.1016/j.jpaa.2025.107949","DOIUrl":"10.1016/j.jpaa.2025.107949","url":null,"abstract":"<div><div>A very useful result concerning flatness in Algebraic Geometry is EGA's “fiber” criterion. We propose similar fiber criteria to verify flatness of a module while avoiding “finiteness” assumptions. Motivated by a Tannakian viewpoint (where the category of representations comes to the front), we derive applications to the theory of affine and flat group schemes.</div></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 6","pages":"Article 107949"},"PeriodicalIF":0.7,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143683881","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}
{"title":"The associated graded algebras of Brauer graph algebras II: Infinite representation type","authors":"Jing Guo , Yuming Liu , Yu Ye","doi":"10.1016/j.jpaa.2025.107954","DOIUrl":"10.1016/j.jpaa.2025.107954","url":null,"abstract":"<div><div>Let <em>G</em> be a Brauer graph and <em>A</em> the associated Brauer graph algebra. Denote by <span><math><mrow><mi>gr</mi></mrow><mo>(</mo><mi>A</mi><mo>)</mo></math></span> the graded algebra associated with the radical filtration of <em>A</em>. The question when <span><math><mrow><mi>gr</mi></mrow><mo>(</mo><mi>A</mi><mo>)</mo></math></span> is of finite representation type was answered in a previous paper. In the present paper, we characterize when <span><math><mrow><mi>gr</mi></mrow><mo>(</mo><mi>A</mi><mo>)</mo></math></span> is domestic in terms of the associated Brauer graph <em>G</em>.</div></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 6","pages":"Article 107954"},"PeriodicalIF":0.7,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143704492","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}
{"title":"On derivations of free algebras over operads and the generalized divergence","authors":"Geoffrey Powell","doi":"10.1016/j.jpaa.2025.107947","DOIUrl":"10.1016/j.jpaa.2025.107947","url":null,"abstract":"<div><div>For <span><math><mi>O</mi></math></span> a reduced operad, a generalized divergence from the derivations of a free <span><math><mi>O</mi></math></span>-algebra to a suitable trace space is constructed. In the case of the Lie operad, this corresponds to Satoh's trace map and, for the associative operad, to the double divergence of Alekseev, Kawazumi, Kuno and Naef. The generalized divergence is shown to be a 1-cocycle for the usual Lie algebra structure on derivations. These results place the previous constructions into a unified framework; moreover, they are natural with respect to the operad.</div><div>An important new ingredient is the use of naturality with respect to the category of finite-rank free modules and split monomorphisms over a commutative ring <em>R</em>. This allows the notion of torsion for such functors to be exploited.</div><div>Supposing that the ring <em>R</em> is a PID and that the operad <span><math><mi>O</mi></math></span> is binary, the main result relates the kernel of the generalized divergence to the sub Lie algebra of the Lie algebra of derivations that is generated by the elements of degree one with respect to the grading induced by arity.</div></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 6","pages":"Article 107947"},"PeriodicalIF":0.7,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143683879","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}
{"title":"A representation embedding for algebras of infinite type","authors":"R. Bautista , E. Pérez , L. Salmerón","doi":"10.1016/j.jpaa.2025.107955","DOIUrl":"10.1016/j.jpaa.2025.107955","url":null,"abstract":"<div><div>We show that for any finite-dimensional algebra Λ of infinite representation type, over a perfect field, there is a bounded principal ideal domain Γ and a representation embedding from <span><math><mi>Γ</mi><mtext>-</mtext><mrow><mi>mod</mi></mrow></math></span> into <span><math><mi>Λ</mi><mtext>-</mtext><mrow><mi>mod</mi></mrow></math></span>. As an application, we prove a variation of the second Brauer-Thrall conjecture: finite-dimensional algebras of infinite-representation type admit infinite families of non-isomorphic finite-dimensional indecomposables with fixed endolength, for infinitely many endolengths.</div></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 6","pages":"Article 107955"},"PeriodicalIF":0.7,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143759662","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}