{"title":"Arithmetic degree and its application to Zariski dense orbit conjecture","authors":"Yohsuke Matsuzawa, Junyi Xie","doi":"10.1112/jlms.70282","DOIUrl":"10.1112/jlms.70282","url":null,"abstract":"<p>We prove that for a dominant rational self-map <span></span><math>\u0000 <semantics>\u0000 <mi>f</mi>\u0000 <annotation>$f$</annotation>\u0000 </semantics></math> on a quasi-projective variety defined over <span></span><math>\u0000 <semantics>\u0000 <mover>\u0000 <mi>Q</mi>\u0000 <mo>¯</mo>\u0000 </mover>\u0000 <annotation>$overline{mathbb {Q}}$</annotation>\u0000 </semantics></math>, there is a point whose <span></span><math>\u0000 <semantics>\u0000 <mi>f</mi>\u0000 <annotation>$f$</annotation>\u0000 </semantics></math>-orbit is well-defined and its arithmetic degree is arbitrarily close to the first dynamical degree of <span></span><math>\u0000 <semantics>\u0000 <mi>f</mi>\u0000 <annotation>$f$</annotation>\u0000 </semantics></math>. As an application, we prove that Zariski dense orbit conjecture holds for a birational map defined over <span></span><math>\u0000 <semantics>\u0000 <mover>\u0000 <mi>Q</mi>\u0000 <mo>¯</mo>\u0000 </mover>\u0000 <annotation>$overline{mathbb {Q}}$</annotation>\u0000 </semantics></math> whose first dynamical degree is strictly larger than its third dynamical degree. In particular, the conjecture holds for birational maps on threefolds whose first dynamical is degree greater than 1.</p>","PeriodicalId":49989,"journal":{"name":"Journal of the London Mathematical Society-Second Series","volume":"112 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2025-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145012730","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":"Affine and cyclotomic webs","authors":"Linliang Song, Weiqiang Wang","doi":"10.1112/jlms.70278","DOIUrl":"10.1112/jlms.70278","url":null,"abstract":"<p>Generalizing the polynomial web category, we introduce a diagrammatic <span></span><math>\u0000 <semantics>\u0000 <mi>k</mi>\u0000 <annotation>$mathbb {k}$</annotation>\u0000 </semantics></math>-linear monoidal category, <i>the affine web category</i>, for any commutative ring <span></span><math>\u0000 <semantics>\u0000 <mi>k</mi>\u0000 <annotation>$mathbb {k}$</annotation>\u0000 </semantics></math>. Integral bases consisting of elementary diagrams are obtained for the affine web category and its cyclotomic quotient categories. Connections between cyclotomic web categories and finite <span></span><math>\u0000 <semantics>\u0000 <mi>W</mi>\u0000 <annotation>$W$</annotation>\u0000 </semantics></math>-algebras are established, leading to a diagrammatic presentation of idempotent subalgebras of <span></span><math>\u0000 <semantics>\u0000 <mi>W</mi>\u0000 <annotation>$W$</annotation>\u0000 </semantics></math>-Schur algebras introduced by Brundan–Kleshchev. The affine web category will be used as a basic building block of another <span></span><math>\u0000 <semantics>\u0000 <mi>k</mi>\u0000 <annotation>$mathbb {k}$</annotation>\u0000 </semantics></math>-linear monoidal category, <i>the affine Schur category</i>, formulated in a sequel.</p>","PeriodicalId":49989,"journal":{"name":"Journal of the London Mathematical Society-Second Series","volume":"112 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2025-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145012131","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 fixed-point-free involutions in actions of finite exceptional groups of Lie type","authors":"Timothy C. Burness, Mikko Korhonen","doi":"10.1112/jlms.70263","DOIUrl":"10.1112/jlms.70263","url":null,"abstract":"<p>Let <span></span><math>\u0000 <semantics>\u0000 <mi>G</mi>\u0000 <annotation>$G$</annotation>\u0000 </semantics></math> be a nontrivial transitive permutation group on a finite set <span></span><math>\u0000 <semantics>\u0000 <mi>Ω</mi>\u0000 <annotation>$Omega$</annotation>\u0000 </semantics></math>. By a classical theorem of Jordan, <span></span><math>\u0000 <semantics>\u0000 <mi>G</mi>\u0000 <annotation>$G$</annotation>\u0000 </semantics></math> contains a derangement, which is an element with no fixed points on <span></span><math>\u0000 <semantics>\u0000 <mi>Ω</mi>\u0000 <annotation>$Omega$</annotation>\u0000 </semantics></math>. Given a prime divisor <span></span><math>\u0000 <semantics>\u0000 <mi>r</mi>\u0000 <annotation>$r$</annotation>\u0000 </semantics></math> of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>|</mo>\u0000 <mi>Ω</mi>\u0000 <mo>|</mo>\u0000 </mrow>\u0000 <annotation>$|Omega |$</annotation>\u0000 </semantics></math>, we say that <span></span><math>\u0000 <semantics>\u0000 <mi>G</mi>\u0000 <annotation>$G$</annotation>\u0000 </semantics></math> is <span></span><math>\u0000 <semantics>\u0000 <mi>r</mi>\u0000 <annotation>$r$</annotation>\u0000 </semantics></math>-elusive if it does not contain a derangement of order <span></span><math>\u0000 <semantics>\u0000 <mi>r</mi>\u0000 <annotation>$r$</annotation>\u0000 </semantics></math>. In a paper from 2011, Burness, Giudici, and Wilson essentially reduce the classification of the <span></span><math>\u0000 <semantics>\u0000 <mi>r</mi>\u0000 <annotation>$r$</annotation>\u0000 </semantics></math>-elusive primitive groups to the case where <span></span><math>\u0000 <semantics>\u0000 <mi>G</mi>\u0000 <annotation>$G$</annotation>\u0000 </semantics></math> is an almost simple group of Lie type. The classical groups with an <span></span><math>\u0000 <semantics>\u0000 <mi>r</mi>\u0000 <annotation>$r$</annotation>\u0000 </semantics></math>-elusive socle have been determined by Burness and Giudici, and in this paper, we consider the analogous problem for the exceptional groups of Lie type, focussing on the special case <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>r</mi>\u0000 <mo>=</mo>\u0000 <mn>2</mn>\u0000 </mrow>\u0000 <annotation>$r=2$</annotation>\u0000 </semantics></math>. Our main theorem describes all the ","PeriodicalId":49989,"journal":{"name":"Journal of the London Mathematical Society-Second Series","volume":"112 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2025-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://londmathsoc.onlinelibrary.wiley.com/doi/epdf/10.1112/jlms.70263","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145012206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Taking limits in topological recursion","authors":"Gaëtan Borot, Vincent Bouchard, Nitin Kumar Chidambaram, Reinier Kramer, Sergey Shadrin","doi":"10.1112/jlms.70286","DOIUrl":"10.1112/jlms.70286","url":null,"abstract":"<p>When does topological recursion applied to a family of spectral curves commute with taking limits? This problem is subtle, especially when the ramification structure of the spectral curve changes at the limit point. We provide sufficient (straightforward-to-use) conditions for checking when the commutation with limits holds, thereby closing a gap in the literature where this compatibility has been used several times without justification. This takes the form of a stronger result of analyticity of the topological recursion along suitable families. To tackle this question, we formalise the notion of global topological recursion and provide sufficient conditions for its equivalence with local topological recursion. The global version facilitates the study of analyticity and limits. For non-degenerate algebraic curves, we reformulate these conditions purely in terms of the structure of its underlying singularities. Finally, we apply this to study deformations of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>(</mo>\u0000 <mi>r</mi>\u0000 <mo>,</mo>\u0000 <mi>s</mi>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 <annotation>$ (r,s)$</annotation>\u0000 </semantics></math>-spectral curves, spectral curves for weighted Hurwitz numbers and provide several other examples and non-examples (where the commutation with limits fails).</p>","PeriodicalId":49989,"journal":{"name":"Journal of the London Mathematical Society-Second Series","volume":"112 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://londmathsoc.onlinelibrary.wiley.com/doi/epdf/10.1112/jlms.70286","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144934887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Entire functions with Cantor bouquet Julia sets","authors":"Leticia Pardo-Simón, Lasse Rempe","doi":"10.1112/jlms.70142","DOIUrl":"10.1112/jlms.70142","url":null,"abstract":"<p>A hyperbolic transcendental entire function with connected Fatou set is said to be of <i>disjoint type</i>. It is known that the Julia set of a disjoint-type function of finite order is a <i>Cantor bouquet</i>; in particular, it is a collection of arcs (‘hairs'), each connecting a finite endpoint to infinity. We show that the latter property is equivalent to the function being <i>criniferous</i> in the sense of Benini and Rempe (a necessary condition for having a Cantor bouquet Julia set). On the other hand, we show that there is a criniferous disjoint-type entire function whose Julia set is <i>not</i> a Cantor bouquet. We also provide a new characterisation of Cantor bouquet Julia sets in terms of the existence of certain absorbing sets for the set of escaping points, and use this to give a new intrinsic description of a class of entire functions previously introduced by the first author. Finally, the main known sufficient condition for Cantor bouquet Julia sets is the so-called <i>head-start condition</i> of Rottenfußer et al. Under a mild geometric assumption, we prove that this condition is also necessary.</p>","PeriodicalId":49989,"journal":{"name":"Journal of the London Mathematical Society-Second Series","volume":"112 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2025-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://londmathsoc.onlinelibrary.wiley.com/doi/epdf/10.1112/jlms.70142","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144934814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Dichotomy laws for the Hausdorff measure of shrinking target sets in \u0000 \u0000 β\u0000 $beta$\u0000 -dynamical systems","authors":"Yubin He","doi":"10.1112/jlms.70284","DOIUrl":"10.1112/jlms.70284","url":null,"abstract":"<p>In this paper, we investigate the Hausdorff measure of shrinking target sets in <span></span><math>\u0000 <semantics>\u0000 <mi>β</mi>\u0000 <annotation>$beta$</annotation>\u0000 </semantics></math>-dynamical systems. These sets are dynamically defined in analogy to the classical theory of weighted and multiplicative Diophantine approximation. While the Lebesgue measure and Hausdorff dimension theories for these sets are well-understood, much remains unknown about the Hausdorff measure theory. We show that the Hausdorff measure of these sets is either zero or full depending upon the convergence or divergence of a certain series, thus providing a rather complete measure theoretic description of these sets.</p>","PeriodicalId":49989,"journal":{"name":"Journal of the London Mathematical Society-Second Series","volume":"112 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2025-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144934813","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}