Andrea Lesavourey , Thomas Plantard , Willy Susilo
{"title":"Improved computation of polynomial roots over number fields when using complex embeddings","authors":"Andrea Lesavourey , Thomas Plantard , Willy Susilo","doi":"10.1016/j.jaca.2024.100026","DOIUrl":"10.1016/j.jaca.2024.100026","url":null,"abstract":"<div><div>We explore a fairly generic method to compute roots of polynomials over number fields through complex embeddings. Our main contribution is to show how to use a structure of a relative extension to decode in a subfield. Additionally we describe several heuristic options to improve practical efficiency. We provide experimental data from our implementation and compare our methods to the state of the art algorithm implemented in <span>Pari/Gp</span>.</div></div>","PeriodicalId":100767,"journal":{"name":"Journal of Computational Algebra","volume":"12 ","pages":"Article 100026"},"PeriodicalIF":0.0,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142538675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Signature-based algorithm under non-compatible term orders and its application to change of ordering","authors":"Masayuki Noro","doi":"10.1016/j.jaca.2024.100027","DOIUrl":"10.1016/j.jaca.2024.100027","url":null,"abstract":"<div><div>The notion of the compatibility between a term order in a polynomial ring <em>R</em> and a module term order in <span><math><msup><mrow><mi>R</mi></mrow><mrow><mi>l</mi></mrow></msup></math></span> is crucial to ensure the termination of a signature-based algorithm for general input ideals. However, it is shown experimentally that the compatibility does not necessarily imply efficient computation. Our experiments show that combining non-compatible term orders can improve performance for computing Gröbner bases with respect to some term orders. In such cases, we can use the Hilbert function to guarantee the termination. The Hilbert function can be computed by using a Gröbner basis with respect to some term order and thus the resulting algorithm is considered a change of ordering algorithm. In this paper, we give the details of the new change of ordering algorithm and we compare its performance with that of the usual Hilbert-driven Buchberger algorithm and the Gröbner walk algorithm.</div></div>","PeriodicalId":100767,"journal":{"name":"Journal of Computational Algebra","volume":"12 ","pages":"Article 100027"},"PeriodicalIF":0.0,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142530145","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Rational Askey–Wilson Bernstein bases and a multirational Askey–Wilson blossom","authors":"Plamen Simeonov , Ron Goldman","doi":"10.1016/j.jaca.2024.100025","DOIUrl":"10.1016/j.jaca.2024.100025","url":null,"abstract":"<div><div>We introduce and study the properties of new negative degree rational Bernstein bases associated with the Askey–Wilson operator and we use these bases to define new types of rational Bernstein-Bézier curves. We also introduce a new type of blossom, the <em>multirational Askey–Wilson blossom</em>. We prove that four axioms uniquely characterize this blossom and we provide an explicit formula for this multirational blossom involving a right inverse of the Askey–Wilson operator. A formula for the coefficients of a function expanded in a rational Askey–Wilson Bernstein basis in terms of certain values of the Askey–Wilson operator is derived. We also establish a dual functional property that expresses the coefficients of these new types of rational Bernstein–Bézier curves in terms of values of their multirational Askey–Wilson blossom.</div></div>","PeriodicalId":100767,"journal":{"name":"Journal of Computational Algebra","volume":"12 ","pages":"Article 100025"},"PeriodicalIF":0.0,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142560843","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Factoring perfect reconstruction filter banks into causal lifting matrices: A Diophantine approach","authors":"Christopher M. Brislawn","doi":"10.1016/j.jaca.2024.100024","DOIUrl":"10.1016/j.jaca.2024.100024","url":null,"abstract":"<div><div>The elementary theory of bivariate linear Diophantine equations over polynomial rings is used to construct causal lifting factorizations (elementary matrix decompositions) for causal two-channel FIR perfect reconstruction transfer matrices and wavelet transforms. The Diophantine approach generates causal factorizations satisfying certain polynomial degree-reducing inequalities, enabling a new factorization strategy called the <em>Causal Complementation Algorithm</em>. This provides a causal (i.e., polynomial, hence <em>realizable</em>) alternative to the noncausal lifting scheme developed by Daubechies and Sweldens using the Extended Euclidean Algorithm for Laurent polynomials. The new approach replaces the Euclidean Algorithm with Gaussian elimination employing a slight generalization of polynomial division that ensures existence and uniqueness of quotients whose remainders satisfy user-specified divisibility constraints. The Causal Complementation Algorithm is shown to be more general than the causal version of the Euclidean Algorithm approach by generating additional causal lifting factorizations beyond those obtainable using the polynomial Euclidean Algorithm.</div></div>","PeriodicalId":100767,"journal":{"name":"Journal of Computational Algebra","volume":"12 ","pages":"Article 100024"},"PeriodicalIF":0.0,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142530144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"New condensation methods with applications to the computation of Brauer character tables","authors":"Klaus Lux , A.J.E. Ryba","doi":"10.1016/j.jaca.2024.100023","DOIUrl":"10.1016/j.jaca.2024.100023","url":null,"abstract":"<div><div>Condensation is a technique that can often predict a Brauer character table of a finite group with a very high degree of confidence, but without a proof of correctness. In this paper we describe a strategy that can give such a proof. We introduce and apply two novel condensation methods: virtual tensor condensation and the condensation of bilinear forms. We illustrate our strategy and new techniques with examples taken from our computation of the 5-modular Brauer character table of the sporadic simple Lyons group.</div></div>","PeriodicalId":100767,"journal":{"name":"Journal of Computational Algebra","volume":"12 ","pages":"Article 100023"},"PeriodicalIF":0.0,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Monomial-agnostic computation of vanishing ideals","authors":"Hiroshi Kera , Yoshihiko Hasegawa","doi":"10.1016/j.jaca.2024.100022","DOIUrl":"10.1016/j.jaca.2024.100022","url":null,"abstract":"<div><p>Approximate basis computation of vanishing ideals has recently been studied extensively in computational algebra and data-driven applications such as machine learning. However, symbolic computation and the dependency on term order remain essential gaps between the two fields. In this study, we present the first <em>monomial-agnostic</em> basis computation, which works fully numerically with proper normalization and without term order. This is realized by gradient normalization, a newly proposed data-dependent normalization that normalizes a polynomial with the magnitude of gradients at given points. Its data-dependent nature brings various advantages: i) efficient resolution of the spurious vanishing problem, the scale-variance issue of approximately vanishing polynomials, without accessing coefficients of terms, ii) scaling-consistent basis computation, ensuring that input scaling does not lead to an essential change in the output, and iii) robustness against input perturbations, where the upper bound of error is determined only by the magnitude of the perturbations. Existing studies did not achieve any of these. As further applications of gradient information, we propose a monomial-agnostic basis reduction method and a regularization method to manage positive-dimensional ideals.</p></div>","PeriodicalId":100767,"journal":{"name":"Journal of Computational Algebra","volume":"11 ","pages":"Article 100022"},"PeriodicalIF":0.0,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2772827724000123/pdfft?md5=06e4502098d7758928fc1fb98de7de21&pid=1-s2.0-S2772827724000123-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142137138","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Conjugacy class fusion from four maximal subgroups of the Monster","authors":"Anthony Pisani, Tomasz Popiel","doi":"10.1016/j.jaca.2024.100021","DOIUrl":"10.1016/j.jaca.2024.100021","url":null,"abstract":"<div><p>We determine the conjugacy class fusion from certain maximal subgroups of the Monster to the Monster, to justify the addition of these data to the Character Table Library in the computational algebra system <span>GAP</span>. The maximal subgroups in question are <span><math><mo>(</mo><msub><mrow><mi>PSL</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><mn>11</mn><mo>)</mo><mo>×</mo><msub><mrow><mi>PSL</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><mn>11</mn><mo>)</mo><mo>)</mo><mo>:</mo><mn>4</mn></math></span>, <span><math><msup><mrow><mn>11</mn></mrow><mrow><mn>2</mn></mrow></msup><mo>:</mo><mo>(</mo><mn>5</mn><mo>×</mo><mn>2</mn><msub><mrow><mtext>A</mtext></mrow><mrow><mn>5</mn></mrow></msub><mo>)</mo></math></span>, <span><math><msup><mrow><mn>7</mn></mrow><mrow><mn>2</mn></mrow></msup><mo>:</mo><msub><mrow><mtext>SL</mtext></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><mn>7</mn><mo>)</mo></math></span>, and <span><math><msub><mrow><mi>PSL</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><mn>19</mn><mo>)</mo><mo>:</mo><mn>2</mn></math></span>. Our proofs are supported by reproducible calculations carried out using the Python package <span>mmgroup</span>, a computational construction of the Monster recently developed by Seysen.</p></div>","PeriodicalId":100767,"journal":{"name":"Journal of Computational Algebra","volume":"11 ","pages":"Article 100021"},"PeriodicalIF":0.0,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2772827724000111/pdfft?md5=fd5301cf7429637c74f4589c0775b2d1&pid=1-s2.0-S2772827724000111-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141962951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Explicit construction of a plane sextic model for genus-five Howe curves, II","authors":"Momonari Kudo","doi":"10.1016/j.jaca.2024.100019","DOIUrl":"10.1016/j.jaca.2024.100019","url":null,"abstract":"<div><p>A <em>Howe curve</em> is defined as the normalization of the fiber product over a projective line of two hyperelliptic curves. Howe curves are very useful to produce important classes of curves over fields of positive characteristic, e.g., maximal, superspecial, or supersingular ones. Determining their feasible equations explicitly is a basic problem, and it has been solved in the hyperelliptic case and in the non-hyperelliptic case with genus not greater than 4. In this paper, we construct an explicit plane sextic model for non-hyperelliptic Howe curves of genus 5. We also determine the number and type of singularities on our sextic model, and prove that the singularities are generically 4 double points. Our results together with Moriya-Kudo's recent ones imply that for each <span><math><mi>s</mi><mo>∈</mo><mo>{</mo><mn>2</mn><mo>,</mo><mn>3</mn><mo>,</mo><mn>4</mn><mo>,</mo><mn>5</mn><mo>}</mo></math></span>, there exists a non-hyperelliptic curve <em>H</em> of genus 5 with <span><math><mrow><mi>Aut</mi></mrow><mo>(</mo><mi>H</mi><mo>)</mo><mo>⊃</mo><msub><mrow><mi>V</mi></mrow><mrow><mn>4</mn></mrow></msub></math></span> such that its associated plane sextic has <em>s</em> double points.</p></div>","PeriodicalId":100767,"journal":{"name":"Journal of Computational Algebra","volume":"11 ","pages":"Article 100019"},"PeriodicalIF":0.0,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2772827724000093/pdfft?md5=3625c91a9b897ff1d916dbfe0aef7474&pid=1-s2.0-S2772827724000093-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141962691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Computing superspecial hyperelliptic curves of genus 4 with automorphism group properly containing the Klein 4-group","authors":"Ryo Ohashi , Momonari Kudo","doi":"10.1016/j.jaca.2024.100020","DOIUrl":"10.1016/j.jaca.2024.100020","url":null,"abstract":"<div><p>In algebraic geometry or number theory, enumerating or finding superspecial curves in positive characteristic <em>p</em> is important both in theory and in computation. In this paper, we propose feasible algorithms to enumerate or find superspecial hyperelliptic curves of genus 4 with automorphism group properly containing the Klein 4-group. By executing the algorithms on Magma, we succeeded in enumerating such superspecial curves for all primes <em>p</em> with <span><math><mn>19</mn><mo>≤</mo><mi>p</mi><mo><</mo><mn>500</mn></math></span>, and in finding a single one for all primes <em>p</em> with <span><math><mn>19</mn><mo>≤</mo><mi>p</mi><mo><</mo><mn>7000</mn></math></span>.</p></div>","PeriodicalId":100767,"journal":{"name":"Journal of Computational Algebra","volume":"11 ","pages":"Article 100020"},"PeriodicalIF":0.0,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S277282772400010X/pdfft?md5=6a6ccd7910eddd0166ae65a5fd559961&pid=1-s2.0-S277282772400010X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141959415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}