MathematikaPub Date : 2025-02-18DOI: 10.1112/mtk.70015
Florian Frick, Andrew Newman, Wesley Pegden
{"title":"Youden's demon is Sylvester's problem","authors":"Florian Frick, Andrew Newman, Wesley Pegden","doi":"10.1112/mtk.70015","DOIUrl":"https://doi.org/10.1112/mtk.70015","url":null,"abstract":"<p>If four people with Gaussian-distributed heights stand at Gaussian positions on the plane, the probability that there are exactly two people whose height is above the average of the four is exactly the same as the probability that they stand in convex position; both probabilities are <span></span><math></math>. We show that this is a special case of a more general phenomenon: The problem of determining the position of the mean among the order statistics of Gaussian random points on the real line (Youden's demon problem) is the same as a natural generalization of Sylvester's four point problem to Gaussian points in <span></span><math></math>. Our main tool is the observation that the Gale dual of independent samples in <span></span><math></math> itself can be taken to be a set of independent points (translated to have barycenter at the origin) when the distribution of the points is Gaussian.</p>","PeriodicalId":18463,"journal":{"name":"Mathematika","volume":"71 2","pages":""},"PeriodicalIF":0.8,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143431696","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}
MathematikaPub Date : 2025-02-13DOI: 10.1112/mtk.70014
Isaac Arelio, Luis Montejano, Deborah Oliveros
{"title":"A four-dimensional peabody of constant width","authors":"Isaac Arelio, Luis Montejano, Deborah Oliveros","doi":"10.1112/mtk.70014","DOIUrl":"https://doi.org/10.1112/mtk.70014","url":null,"abstract":"<p>In this paper, we present a unique four-dimensional body of constant width based on the classical notion of focal conics.</p>","PeriodicalId":18463,"journal":{"name":"Mathematika","volume":"71 2","pages":""},"PeriodicalIF":0.8,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1112/mtk.70014","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143404474","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
MathematikaPub Date : 2025-02-07DOI: 10.1112/mtk.70013
Kirill Kashkan
{"title":"A new construction of forests with low visibility","authors":"Kirill Kashkan","doi":"10.1112/mtk.70013","DOIUrl":"https://doi.org/10.1112/mtk.70013","url":null,"abstract":"<p>A set of points with finite density is constructed in <span></span><math></math>, with <span></span><math></math>, by adding points to a Poisson process such that any line segment of length <span></span><math></math> in <span></span><math></math> will contain one of the points of the set within distance <span></span><math></math> of it. The constant implied by the big-<span></span><math></math> notation depends on the dimension only.</p>","PeriodicalId":18463,"journal":{"name":"Mathematika","volume":"71 2","pages":""},"PeriodicalIF":0.8,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1112/mtk.70013","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143362696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
MathematikaPub Date : 2025-02-06DOI: 10.1112/mtk.70011
Reema A. Sbeih
{"title":"On convex bodies in , , with directly congruent projections","authors":"Reema A. Sbeih","doi":"10.1112/mtk.70011","DOIUrl":"https://doi.org/10.1112/mtk.70011","url":null,"abstract":"<p>Let <span></span><math></math> and let <span></span><math></math> and <span></span><math></math> be two convex bodies in <span></span><math></math> such that their orthogonal projections <span></span><math></math> and <span></span><math></math> onto any <span></span><math></math>-dimensional subspace <span></span><math></math> are directly congruent, that is, there exists a rotation <span></span><math></math> and a vector <span></span><math></math> such that <span></span><math></math>. Assume also that the 2-dimensional projections of <span></span><math></math> and <span></span><math></math> are pairwise different and they do not have <span></span><math></math>-symmetries. Then <span></span><math></math> and <span></span><math></math> are congruent. We also prove an analogous more general result about twice differentiable functions on the unit sphere in <span></span><math></math>.</p>","PeriodicalId":18463,"journal":{"name":"Mathematika","volume":"71 2","pages":""},"PeriodicalIF":0.8,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143362806","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}
MathematikaPub Date : 2025-01-31DOI: 10.1112/mtk.70010
Christian Bagshaw, Bryce Kerr
{"title":"Lattices in function fields and applications","authors":"Christian Bagshaw, Bryce Kerr","doi":"10.1112/mtk.70010","DOIUrl":"https://doi.org/10.1112/mtk.70010","url":null,"abstract":"<p>In recent decades, the use of ideas from Minkowski's Geometry of Numbers has gained recognition as a helpful tool in bounding the number of solutions to modular congruences with variables from short intervals. In 1941, Mahler introduced an analogue to the Geometry of Numbers in function fields over finite fields. Here, we build on Mahler's ideas and develop results useful for bounding the sizes of intersections of lattices and convex bodies in <span></span><math></math>, which are more precise than what is known over <span></span><math></math>. These results are then applied to various problems regarding bounding the number of solutions to congruences in <span></span><math></math>, such as the number of points on polynomial curves in low-dimensional subspaces of finite fields. Our results improve on a number of previous bounds due to Bagshaw, Cilleruelo, Shparlinski and Zumalacárregui. We also present previous techniques developed by various authors for estimating certain energy/point counts in a unified manner.</p>","PeriodicalId":18463,"journal":{"name":"Mathematika","volume":"71 2","pages":""},"PeriodicalIF":0.8,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1112/mtk.70010","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143121401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
MathematikaPub Date : 2025-01-27DOI: 10.1112/mtk.70009
Jeck Lim, Stefan Steinerberger
{"title":"On differences of two harmonic numbers","authors":"Jeck Lim, Stefan Steinerberger","doi":"10.1112/mtk.70009","DOIUrl":"https://doi.org/10.1112/mtk.70009","url":null,"abstract":"<p>We prove the existence of infinitely many <span></span><math></math> such that the difference of harmonic numbers <span></span><math></math> approximates 1 well\u0000\u0000 </p>","PeriodicalId":18463,"journal":{"name":"Mathematika","volume":"71 2","pages":""},"PeriodicalIF":0.8,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143119712","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}
MathematikaPub Date : 2025-01-08DOI: 10.1112/mtk.70005
Matthew Brookes, Victoria Gould, Nik Ruškuc
{"title":"Coherency properties for monoids of transformations and partitions","authors":"Matthew Brookes, Victoria Gould, Nik Ruškuc","doi":"10.1112/mtk.70005","DOIUrl":"https://doi.org/10.1112/mtk.70005","url":null,"abstract":"<p>A monoid <span></span><math></math> is <i>right coherent</i> if every finitely generated subact of every finitely presented right <span></span><math></math>-act itself has a finite presentation; it is <i>weakly right coherent</i> if every finitely generated right ideal of <span></span><math></math> has a finite presentation. We show that full and partial transformation monoids, symmetric inverse monoids and partition monoids over an infinite set are all weakly right coherent, but that none of them is right coherent. Left coherency and weak left coherency are defined dually, and the corresponding results hold for these properties. In order to prove the non-coherency results, we give a presentation of an inverse semigroup which does not embed into any left or right coherent monoid.</p>","PeriodicalId":18463,"journal":{"name":"Mathematika","volume":"71 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143113277","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}
MathematikaPub Date : 2025-01-08DOI: 10.1112/mtk.70006
Gustavo Araújo, Anderson Barbosa, Anselmo Baganha Raposo Jr., Geivison Ribeiro
{"title":"Complements of unions: Insights on spaceability and applications","authors":"Gustavo Araújo, Anderson Barbosa, Anselmo Baganha Raposo Jr., Geivison Ribeiro","doi":"10.1112/mtk.70006","DOIUrl":"https://doi.org/10.1112/mtk.70006","url":null,"abstract":"<p>This paper presents two general criteria to determine spaceability results in the complements of unions of subspaces. The first criterion applies to countable unions of subspaces under specific conditions and is closely related to the results of Kitson and Timoney [J. Math. Anal. Appl. <b>378</b> (2011), 680–686]. This criterion extends and recovers some classical results in this theory. The second criterion establishes sufficient conditions for the complement of a union of Lebesgue spaces to be <span></span><math></math>-spaceable, or not, even when they are not locally convex. We use this result to characterize measurable subsets having positive measure. Armed with these results, we have improved existing results in environments such as Lebesgue measurable function sets, spaces of continuous functions, sequence spaces, nowhere Hölder function sets, Sobolev spaces, non-absolutely summing operator spaces and even sets of functions of bounded variation.</p>","PeriodicalId":18463,"journal":{"name":"Mathematika","volume":"71 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143113276","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}
MathematikaPub Date : 2025-01-02DOI: 10.1112/mtk.70008
Victor Y. Wang
{"title":"Diagonal cubic forms and the large sieve","authors":"Victor Y. Wang","doi":"10.1112/mtk.70008","DOIUrl":"https://doi.org/10.1112/mtk.70008","url":null,"abstract":"<p>Let <span></span><math></math> be the number of integral zeros <span></span><math></math> of <span></span><math></math>. Works of Hooley and Heath-Brown imply <span></span><math></math>, if one assumes automorphy and grand Riemann hypothesis for certain Hasse–Weil <span></span><math></math>-functions. Assuming instead a natural large sieve inequality, we recover the same bound on <span></span><math></math>. This is part of a more general statement, for diagonal cubic forms in <span></span><math></math> variables, where we allow approximations to Hasse–Weil <span></span><math></math>-functions.</p>","PeriodicalId":18463,"journal":{"name":"Mathematika","volume":"71 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2025-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1112/mtk.70008","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143110845","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
MathematikaPub Date : 2024-12-28DOI: 10.1112/mtk.70007
David Kalaj
{"title":"The radial symmetry of minimizers to the weighted Dirichlet energy in","authors":"David Kalaj","doi":"10.1112/mtk.70007","DOIUrl":"https://doi.org/10.1112/mtk.70007","url":null,"abstract":"<p>Let <span></span><math></math> and <span></span><math></math> be annuli in <span></span><math></math>. Let <span></span><math></math>, and assume that <span></span><math></math> is the class of Sobolev <span></span><math></math> homeomorphisms of <span></span><math></math> onto <span></span><math></math>. Then, we consider the following Dirichlet-type energy of <span></span><math></math>:\u0000\u0000 </p><p>For general <span></span><math></math>, we minimize the Dirichlet-type integral <span></span><math></math> throughout the class of radial mappings between given annuli, and this minimum always exists for <span></span><math></math>. For <span></span><math></math>, the image annulus cannot be too thick, which is opposite to the Nitsche-type phenomenon known for the standard Dirichlet energy, where the image annulus cannot be too thin.</p>","PeriodicalId":18463,"journal":{"name":"Mathematika","volume":"71 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2024-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143120151","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}
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