Pub Date : 2025-01-23DOI: 10.1016/j.jalgebra.2025.01.008
Matthew Ondrus
We study the representation theory of the Lie algebra of differential operators of degree at most one on the algebra of complex Laurent polynomials. We define a natural family of subalgebras of , which we call polynomial subalgebras. After classifying the one-dimensional modules for polynomial subalgebras, we use these one-dimensional modules to construct corresponding induced modules for the full Lie algebra . These induced modules are frequently simple and generalize a family of recently discovered simple modules. In order to understand these induced modules in certain complicated cases, we take advantage of some general results on tensor products of modules.
{"title":"Modules induced from large subalgebras of the Lie algebra of differential operators of degree at most one","authors":"Matthew Ondrus","doi":"10.1016/j.jalgebra.2025.01.008","DOIUrl":"10.1016/j.jalgebra.2025.01.008","url":null,"abstract":"<div><div>We study the representation theory of the Lie algebra <span><math><mi>D</mi></math></span> of differential operators of degree at most one on the algebra of complex Laurent polynomials. We define a natural family of subalgebras of <span><math><mi>D</mi></math></span>, which we call polynomial subalgebras. After classifying the one-dimensional modules for polynomial subalgebras, we use these one-dimensional modules to construct corresponding induced modules for the full Lie algebra <span><math><mi>D</mi></math></span>. These induced modules are frequently simple and generalize a family of recently discovered simple modules. In order to understand these induced modules in certain complicated cases, we take advantage of some general results on tensor products of modules.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"668 ","pages":"Pages 533-571"},"PeriodicalIF":0.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164536","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 : 2025-01-23DOI: 10.1016/j.jalgebra.2024.12.032
Igor Haladjian
Complex reflection groups of rank two are precisely the finite groups in the family of groups that we call J-reflection groups. These groups are particular cases of J-groups as defined by Achar & Aubert in 2008. The family of J-reflection groups generalise both complex reflection groups of rank two and toric reflection groups, a family of groups defined and studied by Gobet. We give uniform presentations by generators and relations of J-reflection groups, which coincide with the presentations given by Broué, Malle and Rouquier when the groups are finite. In particular, these presentations provide uniform presentations for complex reflection groups of rank two where the generators are reflections (however the proof uses the classification of irreducible complex reflection groups). Moreover, we show that the center of J-reflection groups is cyclic, generalising what happens for irreducible complex reflection groups of rank two and toric reflection groups. Finally, we classify J-reflection groups up to reflection isomorphisms.
{"title":"A combinatorial generalisation of rank two complex reflection groups via generators and relations","authors":"Igor Haladjian","doi":"10.1016/j.jalgebra.2024.12.032","DOIUrl":"10.1016/j.jalgebra.2024.12.032","url":null,"abstract":"<div><div>Complex reflection groups of rank two are precisely the finite groups in the family of groups that we call <em>J</em>-reflection groups. These groups are particular cases of <em>J</em>-groups as defined by Achar & Aubert in 2008. The family of <em>J</em>-reflection groups generalise both complex reflection groups of rank two and toric reflection groups, a family of groups defined and studied by Gobet. We give uniform presentations by generators and relations of <em>J</em>-reflection groups, which coincide with the presentations given by Broué, Malle and Rouquier when the groups are finite. In particular, these presentations provide uniform presentations for complex reflection groups of rank two where the generators are reflections (however the proof uses the classification of irreducible complex reflection groups). Moreover, we show that the center of <em>J</em>-reflection groups is cyclic, generalising what happens for irreducible complex reflection groups of rank two and toric reflection groups. Finally, we classify <em>J</em>-reflection groups up to reflection isomorphisms.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"668 ","pages":"Pages 308-347"},"PeriodicalIF":0.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164539","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}
We give an algorithm for computing an inseparable endomorphism of a supersingular elliptic curve E defined over , which, conditional on GRH, runs in expected bit operations and requires storage. This matches the time and storage complexity of the best conditional algorithms for computing a nontrivial supersingular endomorphism, such as those of Eisenträger–Hallgren–Leonardi–Morrison–Park and Delfs–Galbraith. Unlike these prior algorithms, which require two paths from E to a curve defined over , the algorithm we introduce only requires one; thus when combined with the algorithm of Corte-Real Santos–Costello–Shi, our algorithm will be faster in practice. Moreover, our algorithm produces endomorphisms with predictable discriminants, enabling us to prove properties about the orders they generate. With two calls to our algorithm, we can provably compute a Bass suborder of . This result is then used in an algorithm for computing a basis for with the same time complexity, assuming GRH. We also argue that can be computed using calls to our algorithm along with polynomial overhead, conditional on a heuristic assumption about the distribution of the discriminants of these endomorphisms. Conditional on GRH and this additional heuristic, this yields a algorithm for computing requiring storage.
{"title":"Computing supersingular endomorphism rings using inseparable endomorphisms","authors":"Jenny Fuselier , Annamaria Iezzi , Mark Kozek , Travis Morrison , Changningphaabi Namoijam","doi":"10.1016/j.jalgebra.2025.01.012","DOIUrl":"10.1016/j.jalgebra.2025.01.012","url":null,"abstract":"<div><div>We give an algorithm for computing an inseparable endomorphism of a supersingular elliptic curve <em>E</em> defined over <span><math><msub><mrow><mi>F</mi></mrow><mrow><msup><mrow><mi>p</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></msub></math></span>, which, conditional on GRH, runs in expected <span><math><mi>O</mi><mo>(</mo><msup><mrow><mi>p</mi></mrow><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup><msup><mrow><mo>(</mo><mi>log</mi><mo></mo><mi>p</mi><mo>)</mo></mrow><mrow><mn>2</mn></mrow></msup><msup><mrow><mo>(</mo><mi>log</mi><mo></mo><mi>log</mi><mo></mo><mi>p</mi><mo>)</mo></mrow><mrow><mn>3</mn></mrow></msup><mo>)</mo></math></span> bit operations and requires <span><math><mi>O</mi><mo>(</mo><msup><mrow><mo>(</mo><mi>log</mi><mo></mo><mi>p</mi><mo>)</mo></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></math></span> storage. This matches the time and storage complexity of the best conditional algorithms for computing a nontrivial supersingular endomorphism, such as those of Eisenträger–Hallgren–Leonardi–Morrison–Park and Delfs–Galbraith. Unlike these prior algorithms, which require two paths from <em>E</em> to a curve defined over <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span>, the algorithm we introduce only requires one; thus when combined with the algorithm of Corte-Real Santos–Costello–Shi, our algorithm will be faster in practice. Moreover, our algorithm produces endomorphisms with predictable discriminants, enabling us to prove properties about the orders they generate. With two calls to our algorithm, we can provably compute a Bass suborder of <span><math><mi>End</mi><mo>(</mo><mi>E</mi><mo>)</mo></math></span>. This result is then used in an algorithm for computing a basis for <span><math><mi>End</mi><mo>(</mo><mi>E</mi><mo>)</mo></math></span> with the same time complexity, assuming GRH. We also argue that <span><math><mi>End</mi><mo>(</mo><mi>E</mi><mo>)</mo></math></span> can be computed using <span><math><mi>O</mi><mo>(</mo><mn>1</mn><mo>)</mo></math></span> calls to our algorithm along with polynomial overhead, conditional on a heuristic assumption about the distribution of the discriminants of these endomorphisms. Conditional on GRH and this additional heuristic, this yields a <span><math><mi>O</mi><mo>(</mo><msup><mrow><mi>p</mi></mrow><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup><msup><mrow><mo>(</mo><mi>log</mi><mo></mo><mi>p</mi><mo>)</mo></mrow><mrow><mn>2</mn></mrow></msup><msup><mrow><mo>(</mo><mi>log</mi><mo></mo><mi>log</mi><mo></mo><mi>p</mi><mo>)</mo></mrow><mrow><mn>3</mn></mrow></msup><mo>)</mo></math></span> algorithm for computing <span><math><mi>End</mi><mo>(</mo><mi>E</mi><mo>)</mo></math></span> requiring <span><math><mi>O</mi><mo>(</mo><msup><mrow><mo>(</mo><mi>log</mi><mo></mo><mi>p</mi><mo>)</mo></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></math></span> storage.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"668 ","pages":"Pages 145-189"},"PeriodicalIF":0.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143163260","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 : 2025-01-23DOI: 10.1016/j.jalgebra.2025.01.007
Ekaterina Kompantseva , Askar Tuganbaev
We consider the class of reduced abelian block-rigid CRQ-groups of ring type. An absolute ideal of an abelian group G is a subgroup of G which is an ideal in any ring on G. A ring R is called an AI-ring if any ideal of R is an absolute ideal of its additive group. An abelian group G is called an RAI-group if there exists at least one AI-ring on G. It is proved that any group in is an RAI-group. Thus, in the class , we solve Problem 93 in the monograph Fuchs (1973) [9]. We classify AI-rings on groups in the class .
{"title":"AI-rings on almost completely decomposable Abelian groups","authors":"Ekaterina Kompantseva , Askar Tuganbaev","doi":"10.1016/j.jalgebra.2025.01.007","DOIUrl":"10.1016/j.jalgebra.2025.01.007","url":null,"abstract":"<div><div>We consider the class <span><math><msub><mrow><mi>A</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> of reduced abelian block-rigid <em>CRQ</em>-groups of ring type. An <span>absolute ideal</span> of an abelian group <em>G</em> is a subgroup of <em>G</em> which is an ideal in any ring on <em>G</em>. A ring <em>R</em> is called an <em>AI</em><strong>-ring</strong> if any ideal of <em>R</em> is an absolute ideal of its additive group. An abelian group <em>G</em> is called an <em>RAI</em><strong>-group</strong> if there exists at least one <em>AI</em>-ring on <em>G</em>. It is proved that any group in <span><math><msub><mrow><mi>A</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> is an <em>RAI</em>-group. Thus, in the class <span><math><msub><mrow><mi>A</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>, we solve Problem 93 in the monograph Fuchs (1973) <span><span>[9]</span></span>. We classify <em>AI</em>-rings on groups in the class <span><math><msub><mrow><mi>A</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"668 ","pages":"Pages 1-19"},"PeriodicalIF":0.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164154","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 : 2025-01-23DOI: 10.1016/j.jalgebra.2024.12.035
Limeng Xia
Let be a simple complex finite dimensional Lie algebra. For generic , let be the quantum group with standard generators . Fixing an index , let be the subalgebra generated by all and , which has sub-quotient algebras isomorphic to . With each generalized Verma -module induced from a simple -module V, we associate a Verma module . In this paper, for infinite dimensional V we prove that is simple if and only if is simple.
{"title":"Generalized Verma modules induced from infinite dimensional simple Uq(sl2)-modules","authors":"Limeng Xia","doi":"10.1016/j.jalgebra.2024.12.035","DOIUrl":"10.1016/j.jalgebra.2024.12.035","url":null,"abstract":"<div><div>Let <span><math><mi>g</mi></math></span> be a simple complex finite dimensional Lie algebra. For generic <span><math><mi>q</mi><mo>∈</mo><msup><mrow><mi>C</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span>, let <span><math><msub><mrow><mi>U</mi></mrow><mrow><mi>q</mi></mrow></msub><mo>(</mo><mi>g</mi><mo>)</mo></math></span> be the quantum group with standard generators <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>,</mo><msub><mrow><mi>F</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>,</mo><msup><mrow><mi>q</mi></mrow><mrow><mo>±</mo><msub><mrow><mi>λ</mi></mrow><mrow><mi>i</mi></mrow></msub></mrow></msup></math></span>. Fixing an index <span><math><msub><mrow><mi>i</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>, let <span><math><mi>P</mi></math></span> be the subalgebra generated by all <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>,</mo><msup><mrow><mi>q</mi></mrow><mrow><mo>±</mo><msub><mrow><mi>λ</mi></mrow><mrow><mi>i</mi></mrow></msub></mrow></msup></math></span> and <span><math><msub><mrow><mi>F</mi></mrow><mrow><msub><mrow><mi>i</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msub></math></span>, which has sub-quotient algebras isomorphic to <span><math><msub><mrow><mi>U</mi></mrow><mrow><msub><mrow><mi>q</mi></mrow><mrow><msub><mrow><mi>i</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msub></mrow></msub><mo>(</mo><msub><mrow><mi>sl</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>)</mo></math></span>. With each generalized Verma <span><math><msub><mrow><mi>U</mi></mrow><mrow><mi>q</mi></mrow></msub><mo>(</mo><mi>g</mi><mo>)</mo></math></span>-module <span><math><msub><mrow><mi>M</mi></mrow><mrow><mi>P</mi></mrow></msub><mo>(</mo><mi>V</mi><mo>)</mo></math></span> induced from a simple <span><math><msub><mrow><mi>U</mi></mrow><mrow><msub><mrow><mi>q</mi></mrow><mrow><msub><mrow><mi>i</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></msub></mrow></msub><mo>(</mo><msub><mrow><mi>sl</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>)</mo></math></span>-module <em>V</em>, we associate a Verma module <span><math><mi>M</mi><mo>(</mo><mi>V</mi><mo>)</mo></math></span>. In this paper, for infinite dimensional <em>V</em> we prove that <span><math><msub><mrow><mi>M</mi></mrow><mrow><mi>P</mi></mrow></msub><mo>(</mo><mi>V</mi><mo>)</mo></math></span> is simple if and only if <span><math><mi>M</mi><mo>(</mo><mi>V</mi><mo>)</mo></math></span> is simple.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"668 ","pages":"Pages 20-45"},"PeriodicalIF":0.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164153","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 : 2025-01-23DOI: 10.1016/j.jalgebra.2025.01.015
Elena Campedel, Ginevra Giordani, Antonio Ioppolo
Let F be a fixed field of characteristic zero containing an element i such that . In this paper we consider finite dimensional superalgebras over F endowed with a pseudoautomorphism p and we investigate the asymptotic behavior of the corresponding sequence of p-codimensions , . First we give a positive answer to a conjecture of Amitsur in this setting: the p-exponent always exists and it is an integer. In the final part we characterize the algebras whose exponential growth is bounded by 2.
{"title":"Codimensions of algebras with pseudoautomorphism and their exponential growth","authors":"Elena Campedel, Ginevra Giordani, Antonio Ioppolo","doi":"10.1016/j.jalgebra.2025.01.015","DOIUrl":"10.1016/j.jalgebra.2025.01.015","url":null,"abstract":"<div><div>Let <em>F</em> be a fixed field of characteristic zero containing an element <em>i</em> such that <span><math><msup><mrow><mi>i</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>=</mo><mo>−</mo><mn>1</mn></math></span>. In this paper we consider finite dimensional superalgebras over <em>F</em> endowed with a pseudoautomorphism <em>p</em> and we investigate the asymptotic behavior of the corresponding sequence of <em>p</em>-codimensions <span><math><msubsup><mrow><mi>c</mi></mrow><mrow><mi>n</mi></mrow><mrow><mi>p</mi></mrow></msubsup><mo>(</mo><mi>A</mi><mo>)</mo></math></span>, <span><math><mi>n</mi><mo>=</mo><mn>1</mn><mo>,</mo><mn>2</mn><mo>,</mo><mo>…</mo></math></span>. First we give a positive answer to a conjecture of Amitsur in this setting: the <em>p</em>-exponent <span><math><msup><mrow><mi>exp</mi></mrow><mrow><mi>p</mi></mrow></msup><mo></mo><mo>(</mo><mi>A</mi><mo>)</mo><mo>=</mo><msub><mrow><mi>lim</mi></mrow><mrow><mi>n</mi><mo>→</mo><mo>∞</mo></mrow></msub><mo></mo><mroot><mrow><msubsup><mrow><mi>c</mi></mrow><mrow><mi>n</mi></mrow><mrow><mi>p</mi></mrow></msubsup><mo>(</mo><mi>A</mi><mo>)</mo></mrow><mrow><mi>n</mi></mrow></mroot></math></span> always exists and it is an integer. In the final part we characterize the algebras whose exponential growth is bounded by 2.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"668 ","pages":"Pages 75-91"},"PeriodicalIF":0.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164156","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}
We characterize when a finite group G possesses a Sylow 3-subgroup P with abelianization of order 9 in terms of the number of height zero characters lying in the principal 3-block of G, settling a conjecture put forward by Navarro, Sambale, and Tiep in 2018. Along the way, we show that a recent result by Laradji on the number of character of height zero in a block that lie above a given character of some normal subgroup holds, without any hypothesis on the group for blocks of maximal defect.
{"title":"Characters and Sylow subgroup abelianization","authors":"Eugenio Giannelli , Noelia Rizo , A.A. Schaeffer Fry , Carolina Vallejo","doi":"10.1016/j.jalgebra.2024.12.031","DOIUrl":"10.1016/j.jalgebra.2024.12.031","url":null,"abstract":"<div><div>We characterize when a finite group <em>G</em> possesses a Sylow 3-subgroup <em>P</em> with abelianization of order 9 in terms of the number of height zero characters lying in the principal 3-block of <em>G</em>, settling a conjecture put forward by Navarro, Sambale, and Tiep in 2018. Along the way, we show that a recent result by Laradji on the number of character of height zero in a block that lie above a given character of some normal subgroup holds, without any hypothesis on the group for blocks of maximal defect.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"667 ","pages":"Pages 824-864"},"PeriodicalIF":0.8,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143104168","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}
Pub Date : 2025-01-22DOI: 10.1016/j.jalgebra.2024.12.030
Thiago Holleben
The theory of Rees algebras of monomial ideals has been extensively studied, and as a consequence, many (sometimes partial) equivalences between algebraic properties of monomial ideals, and combinatorial properties of simplicial complexes and hypergraphs are known. In this paper we show how this theory can be used to find interesting examples in the theory of Lefschetz properties. We explore the consequences of known results from Lefschetz properties for the Rees algebras of squarefree monomial ideals, for example in the calculation of analytic spread. In particular, we show a connection between symbolic powers and f-vectors of simplicial complexes. This perspective leads us to a generalization of Postnikov's “mixed Eulerian numbers”. We prove the positivity of such numbers in our setting.
{"title":"Lefschetz properties of squarefree monomial ideals via Rees algebras","authors":"Thiago Holleben","doi":"10.1016/j.jalgebra.2024.12.030","DOIUrl":"10.1016/j.jalgebra.2024.12.030","url":null,"abstract":"<div><div>The theory of Rees algebras of monomial ideals has been extensively studied, and as a consequence, many (sometimes partial) equivalences between algebraic properties of monomial ideals, and combinatorial properties of simplicial complexes and hypergraphs are known. In this paper we show how this theory can be used to find interesting examples in the theory of Lefschetz properties. We explore the consequences of known results from Lefschetz properties for the Rees algebras of squarefree monomial ideals, for example in the calculation of analytic spread. In particular, we show a connection between symbolic powers and <em>f</em>-vectors of simplicial complexes. This perspective leads us to a generalization of Postnikov's “mixed Eulerian numbers”. We prove the positivity of such numbers in our setting.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"668 ","pages":"Pages 572-599"},"PeriodicalIF":0.8,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164538","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}
Pub Date : 2025-01-22DOI: 10.1016/j.jalgebra.2024.12.034
Joel Brewster Lewis , Jiayuan Wang
In a finite real reflection group, the reflection length of each element is equal to the codimension of its fixed space, and the two coincident functions determine a partial order structure called the absolute order. In complex reflection groups, the reflection length is no longer always equal to the codimension of fixed space, and the two functions give rise to two different partial orders on the group. We characterize the elements w in the combinatorial family of complex reflection groups for which the intervals below w in these two posets coincide. We also explore the relationship between this property and other natural properties of elements in complex reflection groups; some general theory of posets arising from subadditive functions on groups; and the particular case of subadditive functions on the symmetric group.
{"title":"Coincidences between intervals in two partial orders on complex reflection groups","authors":"Joel Brewster Lewis , Jiayuan Wang","doi":"10.1016/j.jalgebra.2024.12.034","DOIUrl":"10.1016/j.jalgebra.2024.12.034","url":null,"abstract":"<div><div>In a finite real reflection group, the reflection length of each element is equal to the codimension of its fixed space, and the two coincident functions determine a partial order structure called the absolute order. In complex reflection groups, the reflection length is no longer always equal to the codimension of fixed space, and the two functions give rise to two different partial orders on the group. We characterize the elements <em>w</em> in the combinatorial family <span><math><mi>G</mi><mo>(</mo><mi>m</mi><mo>,</mo><mi>p</mi><mo>,</mo><mi>n</mi><mo>)</mo></math></span> of complex reflection groups for which the intervals below <em>w</em> in these two posets coincide. We also explore the relationship between this property and other natural properties of elements in complex reflection groups; some general theory of posets arising from subadditive functions on groups; and the particular case of subadditive functions on the symmetric group.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"668 ","pages":"Pages 278-307"},"PeriodicalIF":0.8,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164107","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 : 2025-01-21DOI: 10.1016/j.jalgebra.2024.12.029
Hung P. Tong-Viet
Thompson's theorem states that a finite group G is solvable if and only if every 2-generated subgroup of G is solvable. In this paper, we prove some new criteria for both solvability and nilpotency of a finite group using certain conditions on 2-generated subgroups. We show that a finite group G is solvable if and only if for every pair of two elements x and y in G of coprime prime power order, if is solvable, then is solvable for all . Similarly, a finite group G is nilpotent if and only if for every pair of elements x and y in G of coprime prime power order, if is solvable, then x and commute for some . Some applications to graphs defined on groups are given.
{"title":"Variations on the Thompson theorem","authors":"Hung P. Tong-Viet","doi":"10.1016/j.jalgebra.2024.12.029","DOIUrl":"10.1016/j.jalgebra.2024.12.029","url":null,"abstract":"<div><div>Thompson's theorem states that a finite group <em>G</em> is solvable if and only if every 2-generated subgroup of <em>G</em> is solvable. In this paper, we prove some new criteria for both solvability and nilpotency of a finite group using certain conditions on 2-generated subgroups. We show that a finite group <em>G</em> is solvable if and only if for every pair of two elements <em>x</em> and <em>y</em> in <em>G</em> of coprime prime power order, if <span><math><mo>〈</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>〉</mo></math></span> is solvable, then <span><math><mo>〈</mo><mi>x</mi><mo>,</mo><msup><mrow><mi>y</mi></mrow><mrow><mi>g</mi></mrow></msup><mo>〉</mo></math></span> is solvable for all <span><math><mi>g</mi><mo>∈</mo><mi>G</mi></math></span>. Similarly, a finite group <em>G</em> is nilpotent if and only if for every pair of elements <em>x</em> and <em>y</em> in <em>G</em> of coprime prime power order, if <span><math><mo>〈</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>〉</mo></math></span> is solvable, then <em>x</em> and <span><math><msup><mrow><mi>y</mi></mrow><mrow><mi>g</mi></mrow></msup></math></span> commute for some <span><math><mi>g</mi><mo>∈</mo><mi>G</mi></math></span>. Some applications to graphs defined on groups are given.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"668 ","pages":"Pages 46-74"},"PeriodicalIF":0.8,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143164150","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}