{"title":"拉马努金的10阶连分数作为模函数","authors":"Victor Manuel Aricheta, Russelle Guadalupe","doi":"10.1016/j.jnt.2025.04.001","DOIUrl":null,"url":null,"abstract":"<div><div>We explore the modularity of the continued fractions <span><math><mi>I</mi><mo>(</mo><mi>τ</mi><mo>)</mo><mo>,</mo><mi>J</mi><mo>(</mo><mi>τ</mi><mo>)</mo><mo>,</mo><msub><mrow><mi>T</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>(</mo><mi>τ</mi><mo>)</mo><mo>,</mo><msub><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><mi>τ</mi><mo>)</mo></math></span>, and <span><math><mi>U</mi><mo>(</mo><mi>τ</mi><mo>)</mo><mo>=</mo><mi>I</mi><mo>(</mo><mi>τ</mi><mo>)</mo><mo>/</mo><mi>J</mi><mo>(</mo><mi>τ</mi><mo>)</mo></math></span> of order 10, which are special cases of certain identities of Ramanujan. The continued fractions <span><math><mi>I</mi><mo>(</mo><mi>τ</mi><mo>)</mo></math></span> and <span><math><mi>J</mi><mo>(</mo><mi>τ</mi><mo>)</mo></math></span> were recently introduced by Rajkhowa and Saikia. We show that these continued fractions can be expressed in terms of an <em>η</em>-quotient <span><math><mi>g</mi><mo>(</mo><mi>τ</mi><mo>)</mo></math></span> that generates the field of all modular functions on the congruence subgroup <span><math><msub><mrow><mi>Γ</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>(</mo><mn>10</mn><mo>)</mo></math></span>. Consequently, we deduce that the modular equations for <span><math><mi>g</mi><mo>(</mo><mi>τ</mi><mo>)</mo></math></span> and <span><math><mi>U</mi><mo>(</mo><mi>τ</mi><mo>)</mo></math></span> exist at any level and derive these equations of prime levels <span><math><mi>p</mi><mo>≤</mo><mn>11</mn></math></span>. We also show that the continued fractions of order 10 can be explicitly evaluated using a singular value of <span><math><mi>g</mi><mo>(</mo><mi>τ</mi><mo>)</mo></math></span>, which under certain conditions generates the Hilbert class field of an imaginary quadratic field. We employ the methods of Lee and Park to establish our results.</div></div>","PeriodicalId":50110,"journal":{"name":"Journal of Number Theory","volume":"278 ","pages":"Pages 214-244"},"PeriodicalIF":0.6000,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Ramanujan's continued fractions of order 10 as modular functions\",\"authors\":\"Victor Manuel Aricheta, Russelle Guadalupe\",\"doi\":\"10.1016/j.jnt.2025.04.001\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>We explore the modularity of the continued fractions <span><math><mi>I</mi><mo>(</mo><mi>τ</mi><mo>)</mo><mo>,</mo><mi>J</mi><mo>(</mo><mi>τ</mi><mo>)</mo><mo>,</mo><msub><mrow><mi>T</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>(</mo><mi>τ</mi><mo>)</mo><mo>,</mo><msub><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><mi>τ</mi><mo>)</mo></math></span>, and <span><math><mi>U</mi><mo>(</mo><mi>τ</mi><mo>)</mo><mo>=</mo><mi>I</mi><mo>(</mo><mi>τ</mi><mo>)</mo><mo>/</mo><mi>J</mi><mo>(</mo><mi>τ</mi><mo>)</mo></math></span> of order 10, which are special cases of certain identities of Ramanujan. The continued fractions <span><math><mi>I</mi><mo>(</mo><mi>τ</mi><mo>)</mo></math></span> and <span><math><mi>J</mi><mo>(</mo><mi>τ</mi><mo>)</mo></math></span> were recently introduced by Rajkhowa and Saikia. We show that these continued fractions can be expressed in terms of an <em>η</em>-quotient <span><math><mi>g</mi><mo>(</mo><mi>τ</mi><mo>)</mo></math></span> that generates the field of all modular functions on the congruence subgroup <span><math><msub><mrow><mi>Γ</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>(</mo><mn>10</mn><mo>)</mo></math></span>. Consequently, we deduce that the modular equations for <span><math><mi>g</mi><mo>(</mo><mi>τ</mi><mo>)</mo></math></span> and <span><math><mi>U</mi><mo>(</mo><mi>τ</mi><mo>)</mo></math></span> exist at any level and derive these equations of prime levels <span><math><mi>p</mi><mo>≤</mo><mn>11</mn></math></span>. We also show that the continued fractions of order 10 can be explicitly evaluated using a singular value of <span><math><mi>g</mi><mo>(</mo><mi>τ</mi><mo>)</mo></math></span>, which under certain conditions generates the Hilbert class field of an imaginary quadratic field. We employ the methods of Lee and Park to establish our results.</div></div>\",\"PeriodicalId\":50110,\"journal\":{\"name\":\"Journal of Number Theory\",\"volume\":\"278 \",\"pages\":\"Pages 214-244\"},\"PeriodicalIF\":0.6000,\"publicationDate\":\"2025-06-04\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Number Theory\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0022314X25001428\",\"RegionNum\":3,\"RegionCategory\":\"数学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"MATHEMATICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Number Theory","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0022314X25001428","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"MATHEMATICS","Score":null,"Total":0}
Ramanujan's continued fractions of order 10 as modular functions
We explore the modularity of the continued fractions , and of order 10, which are special cases of certain identities of Ramanujan. The continued fractions and were recently introduced by Rajkhowa and Saikia. We show that these continued fractions can be expressed in terms of an η-quotient that generates the field of all modular functions on the congruence subgroup . Consequently, we deduce that the modular equations for and exist at any level and derive these equations of prime levels . We also show that the continued fractions of order 10 can be explicitly evaluated using a singular value of , which under certain conditions generates the Hilbert class field of an imaginary quadratic field. We employ the methods of Lee and Park to establish our results.
期刊介绍:
The Journal of Number Theory (JNT) features selected research articles that represent the broad spectrum of interest in contemporary number theory and allied areas. A valuable resource for mathematicians, the journal provides an international forum for the publication of original research in this field.
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