{"title":"Examples and cofibrant generation of effective Kan fibrations","authors":"Benno van den Berg , Freek Geerligs","doi":"10.1016/j.jpaa.2024.107812","DOIUrl":"10.1016/j.jpaa.2024.107812","url":null,"abstract":"<div><div>We will make two contributions to the theory of effective Kan fibrations, which are a more explicit version of the notion of a Kan fibration, a notion which plays a fundamental role in simplicial homotopy theory. We will show that simplicial Malcev algebras are effective Kan complexes and that the effective Kan fibrations can be seen as the right class in an algebraic weak factorization system. In addition, we will introduce two strengthenings of the notion of an effective Kan fibration, the symmetric effective and degenerate-preferring Kan fibrations, and show that the previous results hold for these strengthenings as well.</div></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 1","pages":"Article 107812"},"PeriodicalIF":0.7,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142425560","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":"Jacobian varieties with group algebra decomposition not affordable by Prym varieties","authors":"Benjamín M. Moraga","doi":"10.1016/j.jpaa.2024.107803","DOIUrl":"10.1016/j.jpaa.2024.107803","url":null,"abstract":"<div><div>The action of a finite group <em>G</em> on a compact Riemann surface <em>X</em> naturally induces another action of <em>G</em> on its Jacobian variety <span><math><mi>J</mi><mo>(</mo><mi>X</mi><mo>)</mo></math></span>. In many cases, each component of the group algebra decomposition of <span><math><mi>J</mi><mo>(</mo><mi>X</mi><mo>)</mo></math></span> is isogenous to a Prym varieties of an intermediate covering of the Galois covering <span><math><msub><mrow><mi>π</mi></mrow><mrow><mi>G</mi></mrow></msub><mo>:</mo><mi>X</mi><mo>→</mo><mi>X</mi><mo>/</mo><mi>G</mi></math></span>; in such a case, we say that the group algebra decomposition is affordable by Prym varieties. In this article, we present an infinite family of groups that act on Riemann surfaces in a manner that the group algebra decomposition of <span><math><mi>J</mi><mo>(</mo><mi>X</mi><mo>)</mo></math></span> is not affordable by Prym varieties; namely, affine groups <span><math><mi>Aff</mi><mo>(</mo><msub><mrow><mi>F</mi></mrow><mrow><mi>q</mi></mrow></msub><mo>)</mo></math></span> with some exceptions: <span><math><mi>q</mi><mo>=</mo><mn>2</mn></math></span>, <span><math><mi>q</mi><mo>=</mo><mn>9</mn></math></span>, <em>q</em> a Fermat prime, <span><math><mi>q</mi><mo>=</mo><msup><mrow><mn>2</mn></mrow><mrow><mi>n</mi></mrow></msup></math></span> with <span><math><msup><mrow><mn>2</mn></mrow><mrow><mi>n</mi></mrow></msup><mo>−</mo><mn>1</mn></math></span> a Mersenne prime and some particular cases when <span><math><mi>X</mi><mo>/</mo><mi>G</mi></math></span> has genus 0 or 1. In each one of this exceptional cases, we give the group algebra decomposition of <span><math><mi>J</mi><mo>(</mo><mi>X</mi><mo>)</mo></math></span> by Prym varieties.</div></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 1","pages":"Article 107803"},"PeriodicalIF":0.7,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142315895","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 the transcendental lattices of Hyper-Kähler manifolds","authors":"Benedetta Piroddi , Ángel David Ríos Ortiz","doi":"10.1016/j.jpaa.2024.107805","DOIUrl":"10.1016/j.jpaa.2024.107805","url":null,"abstract":"<div><p>We introduce the notion of a Hyper-Kähler manifold <em>X</em> induced by a Hodge structure of K3-type. We explore this notion for the known deformation types of Hyper-Kähler manifolds studying those that are induced by a K3 or abelian surface (that is, induced by the Hodge structure of their transcendental lattice), giving lattice-theoretic criteria to decide whether or not they are birational to a moduli space of sheaves over said surface. We highlight the different behaviors we find for the particular class of Hyper-Kähler manifolds of O'Grady type.</p></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 1","pages":"Article 107805"},"PeriodicalIF":0.7,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0022404924002020/pdfft?md5=edd17e74a859b78f7d2ca46a3aecaa1f&pid=1-s2.0-S0022404924002020-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142237324","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":"Some remarks on spin-orbits of unit vectors","authors":"Tariq Syed","doi":"10.1016/j.jpaa.2024.107802","DOIUrl":"10.1016/j.jpaa.2024.107802","url":null,"abstract":"<div><p>For <span><math><mi>n</mi><mo>∈</mo><mi>N</mi></math></span> and a commutative ring <em>R</em> with <span><math><mn>2</mn><mo>∈</mo><msup><mrow><mi>R</mi></mrow><mrow><mo>×</mo></mrow></msup></math></span>, the group <span><math><mi>S</mi><msub><mrow><mi>L</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span> acts on the set <span><math><mi>U</mi><msub><mrow><mi>m</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span> of unimodular vectors of length <em>n</em> and <span><math><mi>S</mi><mi>p</mi><mi>i</mi><msub><mrow><mi>n</mi></mrow><mrow><mn>2</mn><mi>n</mi></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span> acts on the set of unit vectors <span><math><msub><mrow><mi>U</mi></mrow><mrow><mn>2</mn><mi>n</mi><mo>−</mo><mn>1</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span>. We give an example of a ring for which the comparison map <span><math><mi>U</mi><msub><mrow><mi>m</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo><mo>/</mo><mi>S</mi><msub><mrow><mi>L</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo><mo>→</mo><msub><mrow><mi>U</mi></mrow><mrow><mn>2</mn><mi>n</mi><mo>−</mo><mn>1</mn></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo><mo>/</mo><mi>S</mi><mi>p</mi><mi>i</mi><msub><mrow><mi>n</mi></mrow><mrow><mn>2</mn><mi>n</mi></mrow></msub><mo>(</mo><mi>R</mi><mo>)</mo></math></span> fails to be bijective.</p></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 1","pages":"Article 107802"},"PeriodicalIF":0.7,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0022404924001993/pdfft?md5=92a252c768ddb3132dc1cf4aa6995e84&pid=1-s2.0-S0022404924001993-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142173339","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":"On local divisor class groups of complete intersections","authors":"Daniel Windisch","doi":"10.1016/j.jpaa.2024.107804","DOIUrl":"10.1016/j.jpaa.2024.107804","url":null,"abstract":"<div><p>Samuel conjectured in 1961 that a (Noetherian) local complete intersection ring that is a UFD in codimension at most three is itself a UFD. It is said that Grothendieck invented local cohomology to prove this fact. Following the philosophy that a UFD is nothing else than a Krull domain (that is, a normal domain, in the Noetherian case) with trivial divisor class group, we take a closer look at the Samuel–Grothendieck Theorem and prove the following generalization: Let <em>A</em> be a local Cohen–Macaulay ring.</p><ul><li><span>(1)</span><span><p><em>A</em> is a normal domain if and only if <em>A</em> is a normal domain in codimension at most 1.</p></span></li><li><span>(2)</span><span><p>Suppose that <em>A</em> is a normal domain and a complete intersection. Then the divisor class group of <em>A</em> is a subgroup of the projective limit of the divisor class groups of the localizations <span><math><msub><mrow><mi>A</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span>, where <em>p</em> runs through all prime ideals of height at most 3 in <em>A</em>.</p></span></li></ul> We use this fact to describe for an integral Noetherian locally complete intersection scheme <em>X</em> the gap between the groups of Weil and Cartier divisors, generalizing in this case the classical result that these two concepts coincide if <em>X</em> is locally a UFD.</div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 1","pages":"Article 107804"},"PeriodicalIF":0.7,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0022404924002019/pdfft?md5=1e4c0d69cfcf0e52b73f98c66deb7d97&pid=1-s2.0-S0022404924002019-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142168841","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}
Nathan Geer, Bertrand Patureau-Mirand, Matthew Rupert
{"title":"Some remarks on relative modular categories","authors":"Nathan Geer, Bertrand Patureau-Mirand, Matthew Rupert","doi":"10.1016/j.jpaa.2024.107801","DOIUrl":"10.1016/j.jpaa.2024.107801","url":null,"abstract":"<div><div>We study properties of relative modular categories and derive sufficient conditions for their existence. In particular, we derive sufficient conditions for relative pre-modular categories to be non-degenerate and sufficient conditions for the construction of generically semisimple categories.</div></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 1","pages":"Article 107801"},"PeriodicalIF":0.7,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142311805","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":"Skew power series rings over a prime base ring","authors":"Adam Jones , William Woods","doi":"10.1016/j.jpaa.2024.107800","DOIUrl":"10.1016/j.jpaa.2024.107800","url":null,"abstract":"<div><p>In this paper, we investigate the structure of skew power series rings of the form <span><math><mi>S</mi><mo>=</mo><mi>R</mi><mo>[</mo><mo>[</mo><mi>x</mi><mo>;</mo><mi>σ</mi><mo>,</mo><mi>δ</mi><mo>]</mo><mo>]</mo></math></span>, where <em>R</em> is a complete, positively filtered ring and <span><math><mo>(</mo><mi>σ</mi><mo>,</mo><mi>δ</mi><mo>)</mo></math></span> is a skew derivation respecting the filtration. Our main focus is on the case in which <span><math><mi>σ</mi><mi>δ</mi><mo>=</mo><mi>δ</mi><mi>σ</mi></math></span>, and we aim to use techniques in non-commutative valuation theory to address the long-standing open question: if <em>P</em> is an invariant prime ideal of <em>R</em>, is <em>PS</em> a prime ideal of <em>S</em>? When <em>R</em> has characteristic <em>p</em>, our results reduce this to a finite-index problem. We also give preliminary results in the “Iwasawa algebra” case <span><math><mi>δ</mi><mo>=</mo><mi>σ</mi><mo>−</mo><msub><mrow><mi>id</mi></mrow><mrow><mi>R</mi></mrow></msub></math></span> in arbitrary characteristic. A key step in our argument will be to show that for a large class of Noetherian algebras, the nilradical is “almost” <span><math><mo>(</mo><mi>σ</mi><mo>,</mo><mi>δ</mi><mo>)</mo></math></span>-invariant in a certain sense.</p></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 1","pages":"Article 107800"},"PeriodicalIF":0.7,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S002240492400197X/pdfft?md5=13b400d1c28154510e7fe3158aa43840&pid=1-s2.0-S002240492400197X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142237327","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":"Characteristic p approaches to the Jacobian conjecture","authors":"Jeffrey Lang","doi":"10.1016/j.jpaa.2024.107797","DOIUrl":"10.1016/j.jpaa.2024.107797","url":null,"abstract":"<div><div>We present several versions of the Jacobian Conjecture in characteristic <span><math><mi>p</mi><mo>></mo><mn>0</mn></math></span> each of which if true would imply the Jacobian Conjecture in characteristic 0. We test these characteristic <em>p</em> versions of the conjecture against several families of Jacobian pairs in characteristic <em>p</em>. Based on the results we propose a characteristic <em>p</em> approach to solving the Jacobian Conjecture in characteristic 0.</div></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 1","pages":"Article 107797"},"PeriodicalIF":0.7,"publicationDate":"2024-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142259310","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":"Classifying torsionfree classes of the category of coherent sheaves and their Serre subcategories","authors":"Shunya Saito","doi":"10.1016/j.jpaa.2024.107799","DOIUrl":"10.1016/j.jpaa.2024.107799","url":null,"abstract":"<div><p>In this paper, we classify several subcategories of the category of coherent sheaves on a divisorial noetherian scheme (e.g. a quasi-projective scheme over a commutative noetherian ring). More precisely, we classify the torsionfree (resp. torsion) classes <em>closed under tensoring with line bundles</em> by the subsets (resp. specialization-closed subsets) of the scheme, which generalizes the classification of torsionfree (resp. torsion) classes of the category of finitely generated modules over a commutative noetherian ring by Takahashi (resp. Stanley–Wang).</p><p>Furthermore, we classify the Serre subcategories of a torsionfree class (in the sense of Quillen's exact categories) by using the above classifications, which gives a certain generalization of Gabriel's classification of Serre subcategories. As explicit applications, we classify the Serre subcategories of the category of maximal pure sheaves, which are a natural generalization of vector bundles for reducible schemes, on a reduced projective curve over a field, and the category of maximal Cohen-Macaulay modules over a one-dimensional Cohen-Macaulay ring.</p></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 1","pages":"Article 107799"},"PeriodicalIF":0.7,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142162369","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 the Drinfeld double of the restricted Jordan plane in characteristic 2","authors":"Nicolás Andruskiewitsch , Dirceu Bagio , Saradia Della Flora , Daiana Flôres","doi":"10.1016/j.jpaa.2024.107798","DOIUrl":"10.1016/j.jpaa.2024.107798","url":null,"abstract":"<div><p>We consider the restricted Jordan plane in characteristic 2, a finite-dimensional Nichols algebra quotient of the Jordan plane that was introduced by Cibils, Lauve and Witherspoon. We extend results from <span><span>arXiv:2002.02514</span><svg><path></path></svg></span> on the analogous object in odd characteristic. We show that the Drinfeld double of the restricted Jordan plane fits into an exact sequence of Hopf algebras whose kernel is a normal local commutative Hopf subalgebra and the cokernel is the restricted enveloping algebra of a restricted Lie algebra <span><math><mi>m</mi></math></span> of dimension 5. We show that <span><math><mi>u</mi><mo>(</mo><mi>m</mi><mo>)</mo></math></span> is tame and compute explicitly the indecomposable modules. An infinite-dimensional Hopf algebra covering the Drinfeld double of the restricted Jordan plane is introduced. Various quantum Frobenius maps are described.</p></div>","PeriodicalId":54770,"journal":{"name":"Journal of Pure and Applied Algebra","volume":"229 1","pages":"Article 107798"},"PeriodicalIF":0.7,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142162429","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}