{"title":"Geometric characterization of Ahlfors regular spaces in terms of dyadic cubes related to wavelets with its applications to equivalences of Lipschitz spaces","authors":"Fan Wang , Dachun Yang , Wen Yuan","doi":"10.1016/j.exmath.2024.125574","DOIUrl":"10.1016/j.exmath.2024.125574","url":null,"abstract":"<div><p>Assume that <span><math><mrow><mo>(</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>,</mo><mi>μ</mi><mo>)</mo></mrow></math></span> is a space of homogeneous type introduced by R. R. Coifman and G. Weiss. In this article, the authors establish a geometric characterization of Ahlfors regular spaces via the dyadic cubes constructed by T. Hytönen and A. Kairema. As applications, the authors show that Lipschitz spaces defined via the quasi-metric under consideration and Lipschitz spaces defined via the measure under consideration coincide with equivalent norms if and only if <span><math><mi>X</mi></math></span> is an Ahlfors regular space. Moreover, the authors also prove that Lipschitz spaces defined via the quasi-metric under consideration and Campanato spaces defined via balls coincide with equivalent norms if and only if <span><math><mi>X</mi></math></span> is an Ahlfors regular space.</p></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141040800","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}
{"title":"Kernel-algorithms in frame-approximations","authors":"P. Jorgensen, Myung-Sin Song, James Tian","doi":"10.1016/j.exmath.2024.125583","DOIUrl":"https://doi.org/10.1016/j.exmath.2024.125583","url":null,"abstract":"","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141134319","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}
{"title":"A short review of finite approximations and unconventional physics","authors":"Trond Digernes","doi":"10.1016/j.exmath.2024.125573","DOIUrl":"https://doi.org/10.1016/j.exmath.2024.125573","url":null,"abstract":"","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141052781","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}
{"title":"Periodicity of general multidimensional continued fractions using repetend matrix form","authors":"Hanka Řada , Štěpán Starosta , Vítězslav Kala","doi":"10.1016/j.exmath.2024.125571","DOIUrl":"https://doi.org/10.1016/j.exmath.2024.125571","url":null,"abstract":"<div><p>We consider expansions of vectors by a general class of multidimensional continued fraction algorithms. If the expansion is eventually periodic, then we describe the possible structure of a matrix corresponding to the repetend and use it to prove that a number of vectors have an eventually periodic expansion in the Algebraic Jacobi–Perron algorithm. Further, we give criteria for vectors to have purely periodic expansions; in particular, the vector cannot be totally positive.</p></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140554317","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}
{"title":"A variation on von Neumann Entropy and a result of Varadarajan","authors":"Glenn D. Appleby","doi":"10.1016/j.exmath.2024.125572","DOIUrl":"https://doi.org/10.1016/j.exmath.2024.125572","url":null,"abstract":"","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140796018","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}
{"title":"A note on the base-p expansions of putative counterexamples to the p-adic Littlewood conjecture","authors":"J. Blackman , S. Kristensen , M.J. Northey","doi":"10.1016/j.exmath.2024.125548","DOIUrl":"10.1016/j.exmath.2024.125548","url":null,"abstract":"<div><p>In this paper, we investigate the base-<span><math><mi>p</mi></math></span> expansions of putative counterexamples to the <span><math><mi>p</mi></math></span>-adic Littlewood conjecture of de Mathan and Teulié. We show that if a counterexample exists, then so does a counterexample whose base-<span><math><mi>p</mi></math></span> expansion is uniformly recurrent. Furthermore, we show that if the base-<span><math><mi>p</mi></math></span> expansion of <span><math><mi>x</mi></math></span> is a morphic word <span><math><mrow><mi>τ</mi><mrow><mo>(</mo><msup><mrow><mi>φ</mi></mrow><mrow><mi>ω</mi></mrow></msup><mrow><mo>(</mo><mi>a</mi><mo>)</mo></mrow><mo>)</mo></mrow></mrow></math></span> where <span><math><mrow><msup><mrow><mi>φ</mi></mrow><mrow><mi>ω</mi></mrow></msup><mrow><mo>(</mo><mi>a</mi><mo>)</mo></mrow></mrow></math></span> contains a subword of the form <span><math><mrow><mi>u</mi><mi>X</mi><mi>u</mi><mi>X</mi><mi>u</mi></mrow></math></span> with <span><math><mrow><msub><mrow><mo>lim</mo></mrow><mrow><mi>n</mi><mo>→</mo><mi>∞</mi></mrow></msub><mrow><mo>|</mo><msup><mrow><mi>φ</mi></mrow><mrow><mi>n</mi></mrow></msup><mrow><mo>(</mo><mi>u</mi><mo>)</mo></mrow><mo>|</mo></mrow><mo>=</mo><mi>∞</mi></mrow></math></span>, then <span><math><mi>x</mi></math></span> satisfies the <span><math><mi>p</mi></math></span>-adic Littlewood conjecture. In the special case when <span><math><mrow><mi>p</mi><mo>=</mo><mn>2</mn></mrow></math></span>, we show that the conjecture holds for all pure morphic words.</p></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S072308692400015X/pdfft?md5=9882f79608644e821115bc0ed83923d6&pid=1-s2.0-S072308692400015X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140281675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Abstract embeddability ranks","authors":"Florent P. Baudier , Christian Rosendal","doi":"10.1016/j.exmath.2024.125563","DOIUrl":"10.1016/j.exmath.2024.125563","url":null,"abstract":"<div><p>We describe several ordinal indices that are capable of detecting, according to various metric notions of faithfulness, the embeddability between pairs of Polish spaces. These embeddability ranks are of theoretical interest but seem difficult to estimate in practice. Embeddability ranks, which are easier to estimate in practice, are embeddability ranks generated by Schauder bases. These embeddability ranks are inspired by the nonlinear indices à la Bourgain. In particular, we resolve a problem raised by F. Baudier, G. Lancien, P. Motakis, and Th. Schlumprecht in Coarse and Lipschitz universality, Fund. Math. 254 (2021), no. 2, 181–214, regarding the necessity of additional set-theoretic axioms regarding the main coarse universality result there.</p></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140182011","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}
{"title":"A simple proof of the Wiener–Ikehara Tauberian Theorem","authors":"M. Ram Murty , Jagannath Sahoo , Akshaa Vatwani","doi":"10.1016/j.exmath.2024.125570","DOIUrl":"10.1016/j.exmath.2024.125570","url":null,"abstract":"<div><p>The Wiener–Ikehara Tauberian theorem is an important theorem giving an asymptotic formula for the sum of coefficients of a Dirichlet series <span><math><mrow><msubsup><mrow><mo>∑</mo></mrow><mrow><mi>n</mi><mo>=</mo><mn>1</mn></mrow><mrow><mi>∞</mi></mrow></msubsup><mfrac><mrow><mi>a</mi><mrow><mo>(</mo><mi>n</mi><mo>)</mo></mrow></mrow><mrow><msup><mrow><mi>n</mi></mrow><mrow><mi>s</mi></mrow></msup></mrow></mfrac></mrow></math></span>. We provide a simple and elegant proof of the Wiener–Ikehara Tauberian theorem which relies only on basic Fourier analysis and known estimates for the given Dirichlet series. This method also allows us to derive a version of the Wiener–Ikehara theorem with an error term.</p></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140181844","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}
{"title":"Obituary: Bent Fuglede (1925–2023)","authors":"Liming Ge (Managing Editor)","doi":"10.1016/j.exmath.2023.125531","DOIUrl":"10.1016/j.exmath.2023.125531","url":null,"abstract":"","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S072308692300107X/pdfft?md5=aa8f8838bfe5d66a791a9333d3459373&pid=1-s2.0-S072308692300107X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139409818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Geometric criteria for the existence of capillary surfaces in tubes","authors":"Giorgio Saracco","doi":"10.1016/j.exmath.2024.125547","DOIUrl":"https://doi.org/10.1016/j.exmath.2024.125547","url":null,"abstract":"<div><p>We review some geometric criteria and prove a refined version, that yield existence of capillary surfaces in tubes <span><math><mrow><mi>Ω</mi><mo>×</mo><mi>R</mi></mrow></math></span> in a gravity free environment, in the case of physical interest, that is, for bounded, open, and simply connected <span><math><mrow><mi>Ω</mi><mo>⊂</mo><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math></span>. These criteria rely on suitable weak one-sided bounds on the curvature of the boundary of the cross-section <span><math><mi>Ω</mi></math></span>.</p></div>","PeriodicalId":50458,"journal":{"name":"Expositiones Mathematicae","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0723086924000148/pdfft?md5=8d050c0fb8ec6bbd1f9d3483b6085e70&pid=1-s2.0-S0723086924000148-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140031119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}