{"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":"10.1016/j.jnt.2025.04.001","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":0.6,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144254315","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Weil-Barsotti formula for T-modules","authors":"Dawid E. Kędzierski, Piotr Krasoń","doi":"10.1016/j.jnt.2025.04.013","DOIUrl":"10.1016/j.jnt.2025.04.013","url":null,"abstract":"<div><div>In the work of M. A. Papanikolas and N. Ramachandran (2003) <span><span>[26]</span></span> the Weil-Barsotti formula for the function field case concerning <span><math><msubsup><mrow><mi>Ext</mi></mrow><mrow><mi>τ</mi></mrow><mrow><mn>1</mn></mrow></msubsup><mo>(</mo><mi>E</mi><mo>,</mo><mi>C</mi><mo>)</mo></math></span> where <em>E</em> is a Drinfeld module and <em>C</em> is the Carlitz module was proved. We generalize this formula to the case where <em>E</em> is a strictly pure <strong>t</strong>-module Φ with the zero nilpotent matrix <span><math><msub><mrow><mi>N</mi></mrow><mrow><mi>Φ</mi></mrow></msub></math></span>. For such a <strong>t</strong>-module Φ we explicitly compute its dual <strong>t</strong>-module <span><math><msup><mrow><mi>Φ</mi></mrow><mrow><mo>∨</mo></mrow></msup></math></span> as well as its double dual <span><math><msup><mrow><mi>Φ</mi></mrow><mrow><mo>∨</mo><mo>∨</mo></mrow></msup></math></span>. This computation is done in a subtle way by combination of the <strong>t</strong>-reduction algorithm developed by F. Głoch, D.E. Kędzierski, P. Krasoń, [<span><span>arXiv:2408.08207</span><svg><path></path></svg></span>] <span><span>[13]</span></span> and the methods of the work of D.E. Kędzierski and P. Krasoń (2024) <span><span>[20]</span></span>. We also give a counterexample to the Weil-Barsotti formula if the nilpotent matrix <span><math><msub><mrow><mi>N</mi></mrow><mrow><mi>Φ</mi></mrow></msub></math></span> is non-zero.</div></div>","PeriodicalId":50110,"journal":{"name":"Journal of Number Theory","volume":"278 ","pages":"Pages 1-25"},"PeriodicalIF":0.6,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144243011","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Class numbers of binary quadratic polynomials","authors":"Zichen Yang","doi":"10.1016/j.jnt.2025.04.012","DOIUrl":"10.1016/j.jnt.2025.04.012","url":null,"abstract":"<div><div>In this paper, we give a formula for the proper class number of a binary quadratic polynomial assuming that the conductor ideal is sufficiently divisible at dyadic places. This allows us to study the growth of the proper class numbers of totally positive binary quadratic polynomials. As an application, we prove finiteness results on totally positive binary quadratic polynomials with a fixed quadratic part and a fixed proper class number.</div></div>","PeriodicalId":50110,"journal":{"name":"Journal of Number Theory","volume":"278 ","pages":"Pages 26-46"},"PeriodicalIF":0.6,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144243012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A note on zero-density approaches for the difference between consecutive primes","authors":"Valeriia Starichkova","doi":"10.1016/j.jnt.2025.04.007","DOIUrl":"10.1016/j.jnt.2025.04.007","url":null,"abstract":"<div><div>In this note, we generalise two results on prime numbers in short intervals. The first result is Ingham's theorem <span><span>[12]</span></span> which connects the zero-density estimates with short intervals where the prime number theorem holds, and the second result is due to Heath-Brown and Iwaniec <span><span>[9]</span></span>, which derives the weighted zero-density estimates used for obtaining the lower bound for the number of primes in short intervals. The generalised versions of these results make the connections between the zero-free regions, zero-density estimates, and the primes in short intervals more transparent. As an example, the generalisation of Ingham's theorem implies that, under the Density Hypothesis, the prime number theorem holds in <span><math><mo>[</mo><mi>x</mi><mo>−</mo><msqrt><mrow><mi>x</mi></mrow></msqrt><mi>exp</mi><mo></mo><mo>(</mo><msup><mrow><mi>log</mi></mrow><mrow><mn>2</mn><mo>/</mo><mn>3</mn><mo>+</mo><mi>ε</mi></mrow></msup><mo></mo><mi>x</mi><mo>)</mo><mo>,</mo><mi>x</mi><mo>]</mo></math></span>, which refines upon the classic interval <span><math><mo>[</mo><mi>x</mi><mo>−</mo><msup><mrow><mi>x</mi></mrow><mrow><mn>1</mn><mo>/</mo><mn>2</mn><mo>+</mo><mi>ε</mi></mrow></msup><mo>,</mo><mi>x</mi><mo>]</mo></math></span>.</div></div>","PeriodicalId":50110,"journal":{"name":"Journal of Number Theory","volume":"278 ","pages":"Pages 245-266"},"PeriodicalIF":0.6,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144254317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Quadratic forms in prime variables with small off–diagonal ranks","authors":"Jakub Dobrowolski","doi":"10.1016/j.jnt.2025.04.006","DOIUrl":"10.1016/j.jnt.2025.04.006","url":null,"abstract":"<div><div>The goal of this note is to establish the limits of Zhao's <span><span>[5]</span></span> techniques for counting solutions to quadratic forms in prime variables. Zhao considered forms with rank at least 9 and showed that these equations have solutions in primes provided there are no local obstructions. We consider in detail the degenerate cases of the off–diagonal ranks 1 and 2, and improve the lower bounds of the ranks to at least 6 and 8, respectively. These results complement a recent breakthrough of Green <span><span>[1]</span></span> on the non-degenerate case of rank 8.</div></div>","PeriodicalId":50110,"journal":{"name":"Journal of Number Theory","volume":"278 ","pages":"Pages 527-546"},"PeriodicalIF":0.6,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144272597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Proofs of four conjectures of Ballantine, Feigon and Merca on linear inequalities of partitions with odd parts","authors":"Olivia X.M. Yao","doi":"10.1016/j.jnt.2025.03.014","DOIUrl":"10.1016/j.jnt.2025.03.014","url":null,"abstract":"<div><div>In their seminal work, Andrews and Merca studied the truncated version of Euler's pentagonal number theorem and deduced an infinite family of linear inequalities for ordinary partition function. The work of Andrews and Merca opened up the study of truncated theta series and linear inequalities for certain restricted partition functions and many articles followed. Recently, Ballantine and Feigon, and Merca posed four conjectures on linear inequalities for partitions with odd parts. In this paper, we confirm those conjectures based on a classical result contributed to Pólya and Szegő.</div></div>","PeriodicalId":50110,"journal":{"name":"Journal of Number Theory","volume":"277 ","pages":"Pages 344-368"},"PeriodicalIF":0.6,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144134733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Hecke relations for eta multipliers and congruences for higher-order smallest parts functions","authors":"Clayton Williams","doi":"10.1016/j.jnt.2025.03.006","DOIUrl":"10.1016/j.jnt.2025.03.006","url":null,"abstract":"<div><div>We derive identities from Hecke operators acting on a family of Eisenstein-eta quotients, giving explicit equalities relating the coefficients of these quotients. From these equalities we derive congruences for the coefficients of these Eisenstein-eta quotients modulo powers of primes. As an application we derive systematic congruences for several higher-order smallest parts functions modulo prime powers, resolving a question of Garvan for these cases. We also relate moments of cranks and ranks to the partition function modulo prime powers. Some of our results strengthen and generalize those of a 2023 paper by Wang and Yang.</div></div>","PeriodicalId":50110,"journal":{"name":"Journal of Number Theory","volume":"277 ","pages":"Pages 325-343"},"PeriodicalIF":0.6,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144116414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On the number of zeros of L−functions attached to cusp forms of half-integral weight","authors":"Pedro Ribeiro","doi":"10.1016/j.jnt.2025.02.014","DOIUrl":"10.1016/j.jnt.2025.02.014","url":null,"abstract":"<div><div>Meher et al. (2019) <span><span>[21]</span></span> have recently established that <em>L</em>−functions attached to certain cusp forms of half-integral weight have infinitely many zeros on the critical line. Kim (2023) <span><span>[18]</span></span> obtained analogous results for <em>L</em>−functions attached to cusp forms twisted by an additive character <span><math><mi>e</mi><mrow><mo>(</mo><mfrac><mrow><mi>p</mi></mrow><mrow><mi>q</mi></mrow></mfrac><mi>n</mi><mo>)</mo></mrow></math></span>, <span><math><mfrac><mrow><mi>p</mi></mrow><mrow><mi>q</mi></mrow></mfrac><mo>∈</mo><mi>Q</mi></math></span>. We extend the results of these authors by giving a lower bound for the number of such zeros.</div><div>We start by developing a variant of a method of de la Vallée Poussin which seems to have interest as it avoids the evaluation of exponential sums. We finish the paper with an improvement of our first estimate by using Lekkerkerker's variant of the Hardy-Littlewood method.</div></div>","PeriodicalId":50110,"journal":{"name":"Journal of Number Theory","volume":"278 ","pages":"Pages 622-668"},"PeriodicalIF":0.6,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144321680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Palak Arora , Glenn Bruda , Bruce Fang , Raul Marquez , Steven J. Miller , Beni Prapashtica , Vismay Sharan , Daeyoung Son , Xueyiming Tang , Saad Waheed
{"title":"Upper bounds for the lowest first zero in families of cuspidal newforms","authors":"Palak Arora , Glenn Bruda , Bruce Fang , Raul Marquez , Steven J. Miller , Beni Prapashtica , Vismay Sharan , Daeyoung Son , Xueyiming Tang , Saad Waheed","doi":"10.1016/j.jnt.2025.02.012","DOIUrl":"10.1016/j.jnt.2025.02.012","url":null,"abstract":"<div><div>Assuming the Generalized Riemann Hypothesis, the non-trivial zeros of <em>L</em>-functions lie on the critical line with the real part 1/2. We find an upper bound of the lowest first zero in families of even cuspidal newforms of prime level tending to infinity. We obtain explicit bounds using the <em>n</em>-level densities and results towards the Katz-Sarnak density conjecture. We prove that as the level tends to infinity, there is at least one form with a normalized zero within 0.218503 of the average spacing. We also obtain the first-ever bounds on the percentage of forms in these families with a fixed number of zeros within a small distance near the central point.</div></div>","PeriodicalId":50110,"journal":{"name":"Journal of Number Theory","volume":"277 ","pages":"Pages 262-289"},"PeriodicalIF":0.6,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144069562","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Distribution of cycles in supersingular ℓ-isogeny graphs","authors":"Eli Orvis","doi":"10.1016/j.jnt.2025.03.013","DOIUrl":"10.1016/j.jnt.2025.03.013","url":null,"abstract":"<div><div>Recent work by Arpin et al. (2024) <span><span>[2]</span></span> counted the number of cycles of length <em>r</em> in supersingular <em>ℓ</em>-isogeny graphs. In this paper, we extend this work to count the number of cycles that occur along the spine. We provide formulas for both the number of such cycles, and the average number as <span><math><mi>p</mi><mo>→</mo><mo>∞</mo></math></span>, with <em>ℓ</em> and <em>r</em> fixed. In particular, we show that when <em>r</em> is not a power of 2, cycles of length <em>r</em> are disproportionately likely to occur along the spine. We provide experimental evidence that this result holds in the case that <em>r</em> is a power of 2 as well.</div></div>","PeriodicalId":50110,"journal":{"name":"Journal of Number Theory","volume":"277 ","pages":"Pages 236-261"},"PeriodicalIF":0.6,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144069561","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}