Pub Date : 2023-09-01DOI: 10.1016/j.exmath.2023.02.004
Peter Bruin
We give an explicit description of the category of central extensions of a group scheme by a sheaf of Abelian groups. Based on this, we describe a framework for computing with central extensions of finite locally free commutative group schemes, torsors under such group schemes and groups of isomorphism classes of these objects.
{"title":"Extensions and torsors for finite group schemes","authors":"Peter Bruin","doi":"10.1016/j.exmath.2023.02.004","DOIUrl":"10.1016/j.exmath.2023.02.004","url":null,"abstract":"<div><p>We give an explicit description of the category of central extensions of a group scheme by a sheaf of Abelian groups. Based on this, we describe a framework for computing with central extensions of finite locally free commutative group schemes, torsors under such group schemes and groups of isomorphism classes of these objects.</p></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"41 3","pages":"Pages 514-530"},"PeriodicalIF":0.7,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43076278","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}
Pub Date : 2023-09-01DOI: 10.1016/j.exmath.2023.02.006
Nicolas Mascot , Denis Simon
We present a simple and efficient algorithm to compute the sum of the algebraic conjugates of a point on an elliptic curve.
给出了一种计算椭圆曲线上一点的代数共轭和的简单有效的算法。
{"title":"Computing the trace of an algebraic point on an elliptic curve","authors":"Nicolas Mascot , Denis Simon","doi":"10.1016/j.exmath.2023.02.006","DOIUrl":"10.1016/j.exmath.2023.02.006","url":null,"abstract":"<div><p>We present a simple and efficient algorithm to compute the sum of the algebraic conjugates of a point on an elliptic curve.</p></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"41 3","pages":"Pages 463-474"},"PeriodicalIF":0.7,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43843514","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}
Pub Date : 2023-09-01DOI: 10.1016/j.exmath.2023.05.004
Rodolphe Richard
Nous proposons une “Conjecture d’André-Oort en pinceau arithmétique”.
C’est une extension de la conjecture d’André-Oort, disons “classique”, formulée à l’origine par Y. André et F. Oort. La conjecture fait intervenir les modèles entiers des variétés de Shimura.
{"title":"Problèmes de type André-Oort en pinceau arithmétique","authors":"Rodolphe Richard","doi":"10.1016/j.exmath.2023.05.004","DOIUrl":"10.1016/j.exmath.2023.05.004","url":null,"abstract":"<div><p>Nous proposons une “Conjecture d’André-Oort en pinceau arithmétique”.</p><p>C’est une extension de la conjecture d’André-Oort, disons “classique”, formulée à l’origine par Y. André et F. Oort. La conjecture fait intervenir les modèles entiers des variétés de Shimura.</p></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"41 3","pages":"Pages 618-630"},"PeriodicalIF":0.7,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43293945","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}
Pub Date : 2023-09-01DOI: 10.1016/j.exmath.2023.08.001
Jennifer Balakrishnan, Ziyang Gao, Pierre Parent, Andrei Yafaev
{"title":"Editorial for special issue in honor of B. Edixhoven (1962-2022)","authors":"Jennifer Balakrishnan, Ziyang Gao, Pierre Parent, Andrei Yafaev","doi":"10.1016/j.exmath.2023.08.001","DOIUrl":"10.1016/j.exmath.2023.08.001","url":null,"abstract":"","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"41 3","pages":"Pages 461-462"},"PeriodicalIF":0.7,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46333260","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}
Pub Date : 2023-09-01DOI: 10.1016/j.exmath.2023.05.001
Gregorio Baldi , Bruno Klingler , Emmanuel Ullmo
Using our recent results on the algebraicity of the Hodge locus for variations of Hodge structures of level at least 3, we improve the results of Lawrence–Venkatesh in direction of the refined Bombieri–Lang conjecture.
{"title":"On the Geometric Zilber–Pink theorem and the Lawrence–Venkatesh method","authors":"Gregorio Baldi , Bruno Klingler , Emmanuel Ullmo","doi":"10.1016/j.exmath.2023.05.001","DOIUrl":"10.1016/j.exmath.2023.05.001","url":null,"abstract":"<div><p>Using our recent results on the algebraicity of the Hodge locus for variations of Hodge structures of level at least 3, we improve the results of Lawrence–Venkatesh in direction of the refined Bombieri–Lang conjecture.</p></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"41 3","pages":"Pages 718-722"},"PeriodicalIF":0.7,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47373732","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}
Pub Date : 2023-09-01DOI: 10.1016/j.exmath.2023.02.008
Robin de Jong, Stefan van der Lugt
We define and study a natural system of tautological rings on the moduli spaces of marked curves at the level of differential forms. We show that certain 2-forms obtained from the natural normal functions on these moduli spaces are tautological. Also we show that rings of tautological forms are always finite dimensional. Finally we characterize the Kawazumi–Zhang invariant as essentially the only smooth function on the moduli space of curves whose Levi form is a tautological form.
{"title":"Rings of tautological forms on moduli spaces of curves","authors":"Robin de Jong, Stefan van der Lugt","doi":"10.1016/j.exmath.2023.02.008","DOIUrl":"https://doi.org/10.1016/j.exmath.2023.02.008","url":null,"abstract":"<div><p>We define and study a natural system of tautological rings on the moduli spaces of marked curves at the level of differential forms. We show that certain 2-forms obtained from the natural normal functions on these moduli spaces are tautological. Also we show that rings of tautological forms are always finite dimensional. Finally we characterize the Kawazumi–Zhang invariant as essentially the only smooth function on the moduli space of curves whose Levi form is a tautological form.</p></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"41 3","pages":"Pages 531-565"},"PeriodicalIF":0.7,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49865976","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}
Pub Date : 2023-09-01DOI: 10.1016/j.exmath.2023.02.005
Oana Padurariu , Ciaran Schembri
Guo and Yang give defining equations for all geometrically hyperelliptic Shimura curves . In this paper we compute the -rational points on the Atkin–Lehner quotients of these curves using a variety of techniques. We also determine which rational points are CM for many of these curves.
{"title":"Rational points on Atkin–Lehner quotients of geometrically hyperelliptic Shimura curves","authors":"Oana Padurariu , Ciaran Schembri","doi":"10.1016/j.exmath.2023.02.005","DOIUrl":"10.1016/j.exmath.2023.02.005","url":null,"abstract":"<div><p>Guo and Yang give defining equations for all geometrically hyperelliptic Shimura curves <span><math><mrow><msub><mrow><mi>X</mi></mrow><mrow><mn>0</mn></mrow></msub><mrow><mo>(</mo><mi>D</mi><mo>,</mo><mi>N</mi><mo>)</mo></mrow></mrow></math></span>. In this paper we compute the <span><math><mi>Q</mi></math></span>-rational points on the Atkin–Lehner quotients of these curves using a variety of techniques. We also determine which rational points are CM for many of these curves.</p></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"41 3","pages":"Pages 492-513"},"PeriodicalIF":0.7,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47086175","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}
Pub Date : 2023-09-01DOI: 10.1016/j.exmath.2023.02.009
Vishal Arul , J. Steffen Müller
We compute the rational points on the Atkin–Lehner quotient using the quadratic Chabauty method. Our work completes the study of exceptional rational points on the curves of genus between 2 and 6. Together with the work of several authors, this completes the proof of a conjecture of Galbraith.
{"title":"Rational points on X0+(125)","authors":"Vishal Arul , J. Steffen Müller","doi":"10.1016/j.exmath.2023.02.009","DOIUrl":"https://doi.org/10.1016/j.exmath.2023.02.009","url":null,"abstract":"<div><p>We compute the rational points on the Atkin–Lehner quotient <span><math><mrow><msubsup><mrow><mi>X</mi></mrow><mrow><mn>0</mn></mrow><mrow><mo>+</mo></mrow></msubsup><mrow><mo>(</mo><mn>125</mn><mo>)</mo></mrow></mrow></math></span> using the quadratic Chabauty method. Our work completes the study of exceptional rational points on the curves <span><math><mrow><msubsup><mrow><mi>X</mi></mrow><mrow><mn>0</mn></mrow><mrow><mo>+</mo></mrow></msubsup><mrow><mo>(</mo><mi>N</mi><mo>)</mo></mrow></mrow></math></span> of genus between 2 and 6. Together with the work of several authors, this completes the proof of a conjecture of Galbraith.</p></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"41 3","pages":"Pages 709-717"},"PeriodicalIF":0.7,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49865974","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}
Pub Date : 2023-08-21DOI: 10.1016/j.exmath.2023.08.003
Shraddha Rajkhowa, Nipen Saikia
Two continued fractions and of order twenty-four are obtained from a general continued fraction identity of Ramanujan. Some theta-function and modular identities for and are established to prove general theorems for the explicit evaluations of and . From the theta-function identities of and , three colour partition identities are derived as application to partition theory of integer. Further, -, - and -dissection formulas are established for the continued fractions and , and their reciprocals.
{"title":"On Ramanujan’s continued fractions of order twenty-four","authors":"Shraddha Rajkhowa, Nipen Saikia","doi":"10.1016/j.exmath.2023.08.003","DOIUrl":"10.1016/j.exmath.2023.08.003","url":null,"abstract":"<div><p>Two continued fractions <span><math><mrow><mi>U</mi><mrow><mo>(</mo><mi>q</mi><mo>)</mo></mrow></mrow></math></span> and <span><math><mrow><mi>V</mi><mrow><mo>(</mo><mi>q</mi><mo>)</mo></mrow></mrow></math></span><span> of order twenty-four are obtained from a general continued fraction identity of Ramanujan. Some theta-function and modular identities for </span><span><math><mrow><mi>U</mi><mrow><mo>(</mo><mi>q</mi><mo>)</mo></mrow></mrow></math></span> and <span><math><mrow><mi>V</mi><mrow><mo>(</mo><mi>q</mi><mo>)</mo></mrow></mrow></math></span> are established to prove general theorems for the explicit evaluations of <span><math><mrow><mi>U</mi><mrow><mo>(</mo><mo>±</mo><mi>q</mi><mo>)</mo></mrow></mrow></math></span> and <span><math><mrow><mi>V</mi><mrow><mo>(</mo><mo>±</mo><mi>q</mi><mo>)</mo></mrow></mrow></math></span>. From the theta-function identities of <span><math><mrow><mi>U</mi><mrow><mo>(</mo><mi>q</mi><mo>)</mo></mrow></mrow></math></span> and <span><math><mrow><mi>V</mi><mrow><mo>(</mo><mi>q</mi><mo>)</mo></mrow></mrow></math></span>, three colour partition identities are derived as application to partition theory of integer. Further, <span><math><mn>2</mn></math></span>-, <span><math><mn>4</mn></math></span>- and <span><math><mn>8</mn></math></span>-dissection formulas are established for the continued fractions <span><math><mrow><msup><mrow><mi>U</mi></mrow><mrow><mo>∗</mo></mrow></msup><mrow><mo>(</mo><mi>q</mi><mo>)</mo></mrow><mo>≔</mo><msup><mrow><mi>q</mi></mrow><mrow><mo>−</mo><mn>5</mn><mo>/</mo><mn>2</mn></mrow></msup><mi>U</mi><mrow><mo>(</mo><mi>q</mi><mo>)</mo></mrow></mrow></math></span> and <span><math><mrow><msup><mrow><mi>V</mi></mrow><mrow><mo>∗</mo></mrow></msup><mrow><mo>(</mo><mi>q</mi><mo>)</mo></mrow><mo>≔</mo><msup><mrow><mi>q</mi></mrow><mrow><mo>−</mo><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup><mi>V</mi><mrow><mo>(</mo><mi>q</mi><mo>)</mo></mrow></mrow></math></span>, and their reciprocals.</p></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"41 4","pages":"Article 125516"},"PeriodicalIF":0.7,"publicationDate":"2023-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42408513","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}
Pub Date : 2023-08-19DOI: 10.1016/j.exmath.2023.08.002
Kristýna Zemková
In this paper, the composition of Bhargava’s cubes is generalized to the ring of integers of a number field of narrow class number one, excluding the case of totally imaginary number fields. The exclusion of the latter case arises from the nonexistence of a bijection between (classes of) binary quadratic forms and an ideal class group. This problem, together with a related mistake in another paper of the author, is addressed in the appendix.
{"title":"Composition of Bhargava’s cubes over number fields","authors":"Kristýna Zemková","doi":"10.1016/j.exmath.2023.08.002","DOIUrl":"10.1016/j.exmath.2023.08.002","url":null,"abstract":"<div><p><span><span>In this paper, the composition of Bhargava’s cubes is generalized to the ring of integers of a number field of narrow class number one, excluding the case of totally imaginary number fields. The exclusion of the latter case arises from the nonexistence of a </span>bijection between (classes of) binary </span>quadratic forms and an ideal class group. This problem, together with a related mistake in another paper of the author, is addressed in the appendix.</p></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":"41 4","pages":"Article 125515"},"PeriodicalIF":0.7,"publicationDate":"2023-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44892435","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}