{"title":"On uncommon systems of equations","authors":"Nina Kamčev, Anita Liebenau, Natasha Morrison","doi":"10.1007/s11856-024-2649-2","DOIUrl":"https://doi.org/10.1007/s11856-024-2649-2","url":null,"abstract":"<p>A linear system <i>L</i> over <span>(mathbb{F}_{q})</span> is common if the number of monochromatic solutions to <i>L</i> = 0 in any two-colouring of <span>(mathbb{F}_{q}^{n})</span> is asymptotically at least the expected number of monochromatic solutions in a random two-colouring of <span>(mathbb{F}_{q}^{n})</span>. Motivated by existing results for specific systems (such as Schur triples and arithmetic progressions), as well as extensive research on common and Sidorenko graphs, Saad and Wolf recently initiated the systematic study of common systems of linear equations.</p><p>Building upon earlier work of Cameron, Cilleruelo and Serra, as well as Saad and Wolf, common linear equations have recently been fully characterised by Fox, Pham and Zhao, who asked about common <i>systems</i> of equations. In this paper we move towards a classification of common systems of two or more linear equations. In particular we prove that any system containing an arithmetic progression of length four is uncommon, resolving a question of Saad and Wolf. This follows from a more general result which allows us to deduce the uncommonness of a general system from certain properties of one- or two-equation subsystems.</p>","PeriodicalId":14661,"journal":{"name":"Israel Journal of Mathematics","volume":"60 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Entropy for actions of free groups under bounded orbit-equivalence","authors":"Lewis Bowen, Yuqing Frank Lin","doi":"10.1007/s11856-024-2642-9","DOIUrl":"https://doi.org/10.1007/s11856-024-2642-9","url":null,"abstract":"<p>The <i>f</i>-invariant is a notion of entropy for probability-measure-preserving actions of free groups. We show it is invariant under bounded orbit-equivalence.</p>","PeriodicalId":14661,"journal":{"name":"Israel Journal of Mathematics","volume":"12 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141938648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On minimal generating sets for the mapping class group of a punctured surface","authors":"Naoyuki Monden","doi":"10.1007/s11856-024-2636-7","DOIUrl":"https://doi.org/10.1007/s11856-024-2636-7","url":null,"abstract":"<p>Let Σ<sub><i>g,p</i></sub> be an oriented surface of genus <i>g</i> with <i>p</i> punctures. We denote by <span>(cal{M}_{g,p})</span> and <span>(cal{M}_{g,p}^{pm})</span> the mapping class group and the extended mapping class group of Σ<sub><i>g,p</i></sub>, respectively. In this paper, we show that <span>(cal{M}_{g,p})</span> and <span>(cal{M}_{g,p}^{pm})</span> are generated by two elements for <i>g</i> ≥ 3 and <i>p</i> ≥ 0.</p>","PeriodicalId":14661,"journal":{"name":"Israel Journal of Mathematics","volume":"47 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141938651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Karim Johannes Becher, Nicolas Grenier-Boley, Jean-Pierre Tignol
{"title":"The discriminant Pfister form of an algebra with involution of capacity four","authors":"Karim Johannes Becher, Nicolas Grenier-Boley, Jean-Pierre Tignol","doi":"10.1007/s11856-024-2647-4","DOIUrl":"https://doi.org/10.1007/s11856-024-2647-4","url":null,"abstract":"<p>To an orthogonal or unitary involution on a central simple algebra of degree 4, or to a symplectic involution on a central simple algebra of degree 8, we associate a Pfister form that characterises the decomposability of the algebra with involution. In this way we obtain a unified approach to known decomposability criteria for several cases, and a new result for symplectic involutions on degree-8 algebras in characteristic 2.</p>","PeriodicalId":14661,"journal":{"name":"Israel Journal of Mathematics","volume":"299 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Group-theoretical property of some integral non-degenerate fusion categories","authors":"Zhiqiang Yu","doi":"10.1007/s11856-024-2631-z","DOIUrl":"https://doi.org/10.1007/s11856-024-2631-z","url":null,"abstract":"<p>We show that an integral non-degenerate fusion category <span>({cal C})</span> is group-theoretical if the Frobenius–Perron dimensions of its simple objects are either 1 or powers of a prime <i>p</i>.</p>","PeriodicalId":14661,"journal":{"name":"Israel Journal of Mathematics","volume":"19 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141938645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"An analogue of the Blaschke–Santaló inequality for billiard dynamics","authors":"Daniel Tsodikovich","doi":"10.1007/s11856-024-2634-9","DOIUrl":"https://doi.org/10.1007/s11856-024-2634-9","url":null,"abstract":"<p>The Blaschke–Santaló inequality is a classical inequality in convex geometry concerning the volume of a convex body and that of its dual. In this work we investigate an analogue of this inequality in the context of a billiard dynamical system: we replace the volume with the length of the shortest closed billiard trajectory. We define a quantity called the “billiard product” of a convex body <i>K</i>, which is analogous to the volume product studied in the Blaschke–Santaló inequality. In the planar case, we derive an explicit expression for the billiard product in terms of the diameter of the body. We also investigate upper bounds for this quantity in the class of polygons with a fixed number of vertices.</p>","PeriodicalId":14661,"journal":{"name":"Israel Journal of Mathematics","volume":"79 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141938649","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Flag Hilbert–Poincaré series and Igusa zeta functions of hyperplane arrangements","authors":"Joshua Maglione, Christopher Voll","doi":"10.1007/s11856-024-2646-5","DOIUrl":"https://doi.org/10.1007/s11856-024-2646-5","url":null,"abstract":"<p>We introduce and study a class of multivariate rational functions associated with hyperplane arrangements, called flag Hilbert–Poincaré series. These series are intimately connected with Igusa local zeta functions of products of linear polynomials, and their motivic and topological relatives. Our main results include a self-reciprocity result for central arrangements defined over fields of characteristic zero. We also prove combinatorial formulae for a specialization of the flag Hilbert–Poincaré series for irreducible Coxeter arrangements of types A, B, and D in terms of total partitions of the respective types. We show that a different specialization of the flag Hilbert–Poincaré series, which we call the coarse flag Hilbert–Poincaré series, exhibits intriguing nonnegativity features and—in the case of Coxeter arrangements—connections with Eulerian polynomials. For numerous classes and examples of hyperplane arrangements, we determine their (coarse) flag Hilbert–Poincaré series. Some computations were aided by a SageMath package we developed.</p>","PeriodicalId":14661,"journal":{"name":"Israel Journal of Mathematics","volume":"68 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Maximum principles and direct methods for tempered fractional operators","authors":"Yuxia Guo, Shaolong Peng","doi":"10.1007/s11856-024-2639-4","DOIUrl":"https://doi.org/10.1007/s11856-024-2639-4","url":null,"abstract":"<p>In this paper, we are concerned with the tempered fractional operator <span>(-(Delta+lambda)^{alphaover{2}})</span> with <i>α</i> ∈ (0, 2) and λ is a sufficiently small positive constant. We first establish various maximum principle principles and develop the direct moving planes and sliding methods for anti-symmetric functions involving tempered fractional operators. And then we consider tempered fractional problems. As applications, we extend the direct method of moving planes and sliding methods for the tempered fractional problem, and discuss how they can be used to establish symmetry, monotonicity, Liouville-type results and uniqueness results for solutions in various domains. We believe that our theory and methods can be conveniently applied to study other problems involving tempered fractional operators.</p>","PeriodicalId":14661,"journal":{"name":"Israel Journal of Mathematics","volume":"51 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141938641","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Small deviation estimates and small ball probabilities for geodesics in last passage percolation","authors":"Riddhipratim Basu, Manan Bhatia","doi":"10.1007/s11856-024-2635-8","DOIUrl":"https://doi.org/10.1007/s11856-024-2635-8","url":null,"abstract":"<p>For the exactly solvable model of exponential last passage percolation on ℤ<sup>2</sup>, consider the geodesic Γ<sub><i>n</i></sub> joining (0, 0) and (<i>n, n</i>) for large <i>n</i>. It is well known that the transversal fluctuation of Γ<sub><i>n</i></sub> around the line <i>x</i> = <i>y</i> is <i>n</i><sup>2/3+<i>o</i>(1)</sup> with high probability. We obtain the exponent governing the decay of the small ball probability for Γ<sub><i>n</i></sub> and establish that for small <i>δ</i>, the probability that Γ<sub><i>n</i></sub> is contained in a strip of width <i>δn</i><sup>2/3</sup> around the diagonal is exp(−Θ(<i>δ</i><sup>−3/2</sup>)) uniformly in high <i>n</i>. We also obtain optimal small deviation estimates for the one point distribution of the geodesic showing that for <span>({t}over{2n})</span> bounded away from 0 and 1, we have ℙ(∣<i>x</i>(<i>t</i>) − <i>y</i>(<i>t</i>)∣ ≤ <i>δn</i><sup>2/3</sup>) = Θ(<i>δ</i>) uniformly in high <i>n</i>, where (<i>x</i>(<i>t</i>), <i>y</i>(<i>t</i>)) is the unique point where Γ<sub><i>n</i></sub> intersects the line <i>x</i> + <i>y</i> = <i>t</i>. Our methods are expected to go through for other exactly solvable models of planar last passage percolation and also, upon taking the <i>n</i> → ∞ limit, expected to provide analogous estimates for geodesics in the directed landscape.</p>","PeriodicalId":14661,"journal":{"name":"Israel Journal of Mathematics","volume":"47 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141938646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Stability and deformation of F-singularities","authors":"Alessandro De Stefani, Ilya Smirnov","doi":"10.1007/s11856-024-2638-5","DOIUrl":"https://doi.org/10.1007/s11856-024-2638-5","url":null,"abstract":"<p>We study the problem of m-adic stability of <i>F</i>-singularities, that is, whether the property that a quotient of a local ring (<span>(R,mathfrak{m})</span>) by a non-zero divisor <span>(xinmathfrak{m})</span> has good <i>F</i>-singularities is preserved in a sufficiently small <span>(mathfrak{m})</span>-adic neighborhood of <i>x</i>. We show that <span>(mathfrak{m})</span>-adic stability holds for <i>F</i>-rationality in full generality, and for <i>F</i>-injectivity, <i>F</i>-purity and strong <i>F</i>-regularity under certain assumptions. We show that strong <i>F</i>-regularity and <i>F</i>-purity are not stable in general. Moreover, we exhibit strong connections between stability and deformation phenomena, which hold in great generality.</p>","PeriodicalId":14661,"journal":{"name":"Israel Journal of Mathematics","volume":"2 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141938642","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}