{"title":"Sequences of ICE-closed Subcategories via Preordered (tau ^{-1})-rigid Modules","authors":"Eric J. Hanson","doi":"10.1007/s10468-025-10347-4","DOIUrl":"10.1007/s10468-025-10347-4","url":null,"abstract":"<div><p>Let <span>(Lambda )</span> be a finite-dimensional basic algebra. Sakai recently used certain sequences of image-cokernel-extension-closed (ICE-closed) subcategories of finitely generated <span>(Lambda )</span>-modules to classify certain (generalized) intermediate <i>t</i>-structures in the bounded derived category. We classify these “contravariantly finite ICE-sequences” using concepts from <span>(tau )</span>-tilting theory. More precisely, we introduce “cogen-preordered <span>(tau ^{-1})</span>-rigid modules” as a generalization of (the dual of) the “TF-ordered <span>(tau )</span>-rigid modules” of Mendoza and Treffinger. We then establish a bijection between the set of cogen-preordered <span>(tau ^{-1})</span>-rigid modules and certain sequences of intervals of torsion-free classes. Combined with the results of Sakai, this yields a bijection with the set of contravariantly finite ICE-sequences (of finite length), and thus also with the set of <span>((m+1))</span>-intermediate <i>t</i>-structures whose aisles are homology-determined.</p></div>","PeriodicalId":50825,"journal":{"name":"Algebras and Representation Theory","volume":"28 4","pages":"997 - 1014"},"PeriodicalIF":0.6,"publicationDate":"2025-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10468-025-10347-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144929284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Invariants that are Covering Spaces and their Hopf Algebras","authors":"Ehud Meir","doi":"10.1007/s10468-025-10343-8","DOIUrl":"10.1007/s10468-025-10343-8","url":null,"abstract":"<div><p>In a previous paper by the author a universal ring of invariants for algebraic structures of a given type was constructed. This ring is a polynomial algebra that is generated by certain trace diagrams. It was shown that this ring admits the structure of a rational positive self adjoint Hopf algebra (abbreviated rational PSH-algebra), and was conjectured that it always admits a lattice that is a PSH-algebra, a structure that was introduced by Zelevinsky. In this paper we solve this conjecture, showing that the universal ring of invariants splits as the tensor product of rational PSH-algebras that are either polynomial algebras in a single variable, or admit a lattice that is a PSH-algebra. We do so by considering diagrams as topological spaces, and using tools from the theory of covering spaces. As an application we derive a formula that connects Kronecker coefficients with finite index subgroups of free groups and representations of their Weyl groups, and a formula for the number of conjugacy classes of finite index subgroup in a finitely generated group that admits a surjective homomorphism onto the group of integers.</p></div>","PeriodicalId":50825,"journal":{"name":"Algebras and Representation Theory","volume":"28 4","pages":"883 - 920"},"PeriodicalIF":0.6,"publicationDate":"2025-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10468-025-10343-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144929288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Demazure Filtration of Tensor Product Modules of Current Lie Algebra of Type (A_1)","authors":"Divya Setia, Tanusree Khandai","doi":"10.1007/s10468-025-10334-9","DOIUrl":"10.1007/s10468-025-10334-9","url":null,"abstract":"<div><p>In this paper we study the structure of finite-dimensional representations of the current Lie algebra of type <span>(A_1)</span>, <span>(mathfrak {sl}_2[t])</span>, which are obtained by taking tensor products of local Weyl modules with Demazure modules. We show that such a representation admits a Demazure flag and obtain a closed formula for the graded multiplicities of the level 2 Demazure modules in the filtration of the tensor product of two local Weyl modules for <span>(mathfrak {sl}_2[t])</span>. Furthermore, we show that the tensor product of a local Weyl module with an irreducible <span>(mathfrak {sl}_2[t])</span> module admits a Demazure filtration and derive the graded character of such tensor product modules. In conjunction with the results of Chari et al. (SIGMA Symmetry Integrability Geom. Methods Appl. <b>10</b>(032), 2014), our findings provide evidence for the conjecture in Blanton (2017) that the tensor product of Demazure modules of levels m and n respectively has a filtration by Demazure modules of level m + n.</p></div>","PeriodicalId":50825,"journal":{"name":"Algebras and Representation Theory","volume":"28 2","pages":"679 - 707"},"PeriodicalIF":0.5,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144100238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The Defining Characteristic Case of the Representations of (textrm{GL}_{n}) and (textrm{SL}_{n}) Over Principal Ideal Local Rings","authors":"Nariel Monteiro","doi":"10.1007/s10468-025-10333-w","DOIUrl":"10.1007/s10468-025-10333-w","url":null,"abstract":"<div><p>Let <span>(W_{r}(mathbb {F}_{q}))</span> be the ring of Witt vectors of length <i>r</i> with residue field <span>(mathbb {F}_{q})</span> of characteristic <i>p</i>. In this paper, we study the defining characteristic case of the representations of <span>(textrm{GL}_{n})</span> and <span>(textrm{SL}_{n})</span> over the principal ideal local rings <span>(W_{r}(mathbb {F}_{q}))</span> and <span>(mathbb {F}_{q}[t]/t^{r})</span>. Let <span>({textbf{G}})</span> be either <span>(textrm{GL}_{n})</span> or <span>(textrm{SL}_{n})</span> and <i>F</i> a perfect field of characteristic <i>p</i>, we prove that for most <i>p</i> the group algebras <span>(F[{textbf{G}}(W_{r}(mathbb {F}_{q}))])</span> and <span>(F[{textbf{G}}(mathbb {F}_{q}[t]/t^{r})])</span> are not stably equivalent of Morita type. Thus, the group algebras <span>(F[{textbf{G}}(W_{r}(mathbb {F}_{q}))])</span> and <span>(F[{textbf{G}}(mathbb {F}_{q}[t]/t^{r})])</span> are not isomorphic in the defining characteristic case.</p></div>","PeriodicalId":50825,"journal":{"name":"Algebras and Representation Theory","volume":"28 2","pages":"669 - 677"},"PeriodicalIF":0.5,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144100146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anna Reimann, Yuri Santos Rego, Petra Schwer, Olga Varghese
{"title":"Involutions in Coxeter groups","authors":"Anna Reimann, Yuri Santos Rego, Petra Schwer, Olga Varghese","doi":"10.1007/s10468-025-10332-x","DOIUrl":"10.1007/s10468-025-10332-x","url":null,"abstract":"<div><p>We combinatorially characterize the number <span>(textrm{cc}_2)</span> of conjugacy classes of involutions in any Coxeter group in terms of higher rank odd graphs. This notion naturally generalizes the concept of odd graphs, used previously to count the number of conjugacy classes of reflections. Moreover, we provide formulae for finite and affine types, besides computing <span>(textrm{cc}_2)</span> for all triangle groups and RACGs.</p></div>","PeriodicalId":50825,"journal":{"name":"Algebras and Representation Theory","volume":"28 2","pages":"647 - 667"},"PeriodicalIF":0.5,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10468-025-10332-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144100240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On Interpolation Categories for the Hyperoctahedral Group","authors":"Th. Heidersdorf, G. Tyriard","doi":"10.1007/s10468-025-10331-y","DOIUrl":"10.1007/s10468-025-10331-y","url":null,"abstract":"<div><p>Two different types of Deligne categories have been defined to interpolate the finite dimensional complex representations of the hyperoctahedral group. The first one, initially defined by Knop and then further studied by Likeng and Savage, uses a categorical analogue of the permutation representation as a tensor generator. The second one, due to Flake and Maassen, is tensor generated by a categorical analogue of the reflection representation. We construct a symmetric monoidal functor between the two and show that it is an equivalence of symmetric monoidal categories.</p></div>","PeriodicalId":50825,"journal":{"name":"Algebras and Representation Theory","volume":"28 2","pages":"613 - 646"},"PeriodicalIF":0.5,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10468-025-10331-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144100167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hernán Giraldo, David Reynoso-Mercado, Pedro Rizzo
{"title":"A Partial Classification of Simple Regular Representations of Bimodules Type ((2,,2)) Over the Field of Laurent Series","authors":"Hernán Giraldo, David Reynoso-Mercado, Pedro Rizzo","doi":"10.1007/s10468-025-10327-8","DOIUrl":"10.1007/s10468-025-10327-8","url":null,"abstract":"<div><p>In this paper, we use Galois descent techniques to find suitable representatives of the regular simple representations of the species of type (2, 2) over <span>(k_n:= k[varepsilon ^{1/n}])</span>, where <i>n</i> is a positive integer and <span>(k:=mathbb {C}(!(varepsilon )!))</span> is the field of Laurent series over the complexes. These regular representations are essential for the definition of canonical algebras. Our work is inspired by the work done for species of type (1, 4) on <i>k</i> in Geiss and Reynoso-Mercado (Bol. Soc. Mat. Mex. <b>30</b>(3):87, 2024). We presents all the regular simple representations on the <i>n</i>-crown quiver, and from these, we establish a partial classification of regular simple representations of bimodules type (2, 2).</p></div>","PeriodicalId":50825,"journal":{"name":"Algebras and Representation Theory","volume":"28 2","pages":"549 - 577"},"PeriodicalIF":0.5,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10468-025-10327-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144100236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"PBW-deformations of Graded Algebras with Braiding Relations","authors":"Yujie Gao, Shilin Yang","doi":"10.1007/s10468-025-10328-7","DOIUrl":"10.1007/s10468-025-10328-7","url":null,"abstract":"<div><p>The aim of this paper is to describe all PBW-deformations of the connected graded <span>({mathbb {K}})</span>-algebra <span>(mathcal {A})</span> generated by <span>(x_i, 1le ile n,)</span> with the braiding relations: </p><div><div><span>$$begin{aligned} left{ begin{array}{ll} x_i^2=0, 1le ile n, x_ix_j=x_jx_i, {|j-i|} >1, x_ix_{i+1}x_i=x_{i+1}x_ix_{i+1}, 1le ile n-1. end{array}right. end{aligned}$$</span></div></div><p>Firstly, the complexity <span>(mathcal {C}({mathcal {A}}))</span> of the algebra <span>({mathcal {A}})</span> is computed. Then all PBW-deformations of <span>(mathcal {A})</span> when <span>(nge 2)</span> are given explicitly with the help of the general PBW-deformation theory introduced by Cassidy and Shelton. Finally, it is shown that each non-trivial PBW-deformation of <span>(mathcal {A})</span> is isomorphic to a Iwahori-Hecke algebra <span>(H_q(n+1))</span> (of type <i>A</i>) with <i>n</i> generators and an appropriate parameter <i>q</i>. Here, trivial PBW-deformations of <span>({mathcal {A}})</span> mean that those PBW-deformations that are isomorphic to <span>({mathcal {A}}.)</span></p></div>","PeriodicalId":50825,"journal":{"name":"Algebras and Representation Theory","volume":"28 2","pages":"579 - 611"},"PeriodicalIF":0.5,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144100229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kailash C. Misra, Toshiki Nakashima, Suchada Pongprasert
{"title":"(D_7^{(1)})- Geometric Crystal at the Spin Node","authors":"Kailash C. Misra, Toshiki Nakashima, Suchada Pongprasert","doi":"10.1007/s10468-025-10325-w","DOIUrl":"10.1007/s10468-025-10325-w","url":null,"abstract":"<div><p>Let <span>(mathfrak {g})</span> be an affine Lie algebra with index set <span>(varvec{I})</span> = {<b>0, 1, 2,</b> <span>(ldots , varvec{n}})</span>. It is conjectured that for each Dynkin node <span>(varvec{k} in varvec{I} setminus {{textbf {0}}})</span> the affine Lie algebra <span>(mathfrak {g})</span> has a positive geometric crystal. In this paper, we construct a positive geometric crystal for the affine Lie algebra <span>(varvec{D}_{textbf {7}}^{{textbf {(1)}}})</span> corresponding to the Dynkin spin node <span>(varvec{k}= {textbf {7}})</span>.</p></div>","PeriodicalId":50825,"journal":{"name":"Algebras and Representation Theory","volume":"28 2","pages":"509 - 530"},"PeriodicalIF":0.5,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144100225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Primed Decomposition Tableaux and Extended Queer Crystals","authors":"Eric Marberg, Kam Hung Tong","doi":"10.1007/s10468-025-10323-y","DOIUrl":"10.1007/s10468-025-10323-y","url":null,"abstract":"<div><p>Our previous work introduced a category of extended queer crystals, whose connected normal objects have unique highest weight elements and characters that are Schur <i>Q</i>-polynomials. The initial models for such crystals were based on semistandard shifted tableaux. Here, we introduce a simpler construction using certain “primed” decomposition tableaux, which slightly generalize the decomposition tableaux used in work of Grantcharov et al. This leads to a new, shorter proof of the highest weight properties of the normal subcategory of extended queer crystals. Along the way, we analyze a primed extension of Grantcharov et al.’s insertion scheme for decomposition tableaux.</p></div>","PeriodicalId":50825,"journal":{"name":"Algebras and Representation Theory","volume":"28 2","pages":"445 - 482"},"PeriodicalIF":0.5,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10468-025-10323-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144100278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}