Advances in MathematicsPub Date : 2026-03-01Epub Date: 2026-01-07DOI: 10.1016/j.aim.2025.110767
Tariq Syed
{"title":"Motivic cohomology of cyclic coverings","authors":"Tariq Syed","doi":"10.1016/j.aim.2025.110767","DOIUrl":"10.1016/j.aim.2025.110767","url":null,"abstract":"<div><div>Cyclic coverings produce many examples of topologically contractible smooth affine complex varieties. In this paper, we study the motivic cohomology groups of cyclic coverings over algebraically closed fields of characteristic 0. In particular, we prove that in many situations Chow groups of cyclic coverings become trivial after tensoring with <span><math><mi>Q</mi></math></span>. Furthermore, we can prove that the Chow groups of certain bicyclic coverings are trivial even without tensoring with <span><math><mi>Q</mi></math></span>.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"487 ","pages":"Article 110767"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928072","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Advances in MathematicsPub Date : 2026-03-01Epub Date: 2025-12-30DOI: 10.1016/j.aim.2025.110751
Yuhi Kamio, Ryuya Hora
{"title":"Solution to Lawvere's first problem: A Grothendieck topos that has proper class many quotient topoi","authors":"Yuhi Kamio, Ryuya Hora","doi":"10.1016/j.aim.2025.110751","DOIUrl":"10.1016/j.aim.2025.110751","url":null,"abstract":"<div><div>This paper solves the first of the open problems in topos theory posted by William Lawvere, concerning the existence of a Grothendieck topos that has proper class many quotient topoi. This paper concretely constructs such Grothendieck topoi, including the presheaf topos on the free monoid generated by countably infinitely many elements <span><math><mrow><mi>PSh</mi></mrow><mo>(</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>ω</mi></mrow></msub><mo>)</mo></math></span>. Utilizing the combinatorics of the classifying topos of the theory of inhabited objects and with the help of a system of pairing functions, the problem is reduced to a theorem of Vopěnka, Pultr, and Hedrlín, which states that any set admits a rigid relational structure.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"487 ","pages":"Article 110751"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Advances in MathematicsPub Date : 2026-03-01Epub Date: 2025-12-29DOI: 10.1016/j.aim.2025.110739
Henrik Bachmann , Jan-Willem van Ittersum
{"title":"Formal multiple Eisenstein series and their derivations","authors":"Henrik Bachmann , Jan-Willem van Ittersum","doi":"10.1016/j.aim.2025.110739","DOIUrl":"10.1016/j.aim.2025.110739","url":null,"abstract":"<div><div>We introduce the algebra of formal multiple Eisenstein series and study its derivations. This algebra is motivated by the classical multiple Eisenstein series, introduced by Gangl–Kaneko–Zagier as a hybrid of classical Eisenstein series and multiple zeta values. In depth one, we obtain formal versions of the Eisenstein series satisfying the same algebraic relations as the classical Eisenstein series. In particular, they generate an algebra whose elements we call formal quasimodular forms. We show that the algebra of formal multiple Eisenstein series is an <span><math><msub><mrow><mi>sl</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>-algebra by formalizing the usual derivations for quasimodular forms and extending them naturally to the whole algebra. Additionally, we introduce some families of derivations for general quasi-shuffle algebras, providing a broader context for these derivations. Further, we prove that a quotient of this algebra is isomorphic to the algebra of formal multiple zeta values. This gives a novel and purely formal approach to classical (quasi)modular forms and builds a new link between (formal) multiple zeta values and modular forms.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"487 ","pages":"Article 110739"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145847578","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Advances in MathematicsPub Date : 2026-03-01Epub Date: 2026-01-13DOI: 10.1016/j.aim.2025.110768
Caleb Eckhardt , Jianchao Wu
{"title":"Nuclear dimension and virtually polycyclic groups","authors":"Caleb Eckhardt , Jianchao Wu","doi":"10.1016/j.aim.2025.110768","DOIUrl":"10.1016/j.aim.2025.110768","url":null,"abstract":"<div><div>We show that the nuclear dimension of a (twisted) group C*-algebra of a virtually polycyclic group is finite. This prompts us to make a conjecture relating finite nuclear dimension of group C*-algebras and finite Hirsch length, which we then verify for a class of elementary amenable groups beyond the virtually polycyclic case. In particular, we give the first examples of finitely generated, non-residually finite groups with finite nuclear dimension. A parallel conjecture on finite decomposition rank is also formulated and an analogous result is obtained. Our method relies heavily on recent work of Hirshberg and the second named author on actions of virtually nilpotent groups on <span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>(</mo><mi>X</mi><mo>)</mo></math></span>-algebras.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110768"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145981119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Advances in MathematicsPub Date : 2026-03-01Epub Date: 2026-01-22DOI: 10.1016/j.aim.2026.110797
Jin Gao , Meng Yang
{"title":"Hölder regularity of harmonic functions on metric measure spaces","authors":"Jin Gao , Meng Yang","doi":"10.1016/j.aim.2026.110797","DOIUrl":"10.1016/j.aim.2026.110797","url":null,"abstract":"<div><div>We introduce a Hölder regularity condition for harmonic functions on metric measure spaces and prove that, under a <em>slow</em> volume regular condition and an upper heat kernel estimate, the Hölder regularity condition, the weak Bakry-Émery non-negative curvature condition, Hölder continuity of the heat kernel (with or without exponential terms), and the near-diagonal lower bound for the heat kernel are equivalent. As applications, first, we establish the validity of the so-called generalized reverse Hölder inequality on the Sierpiński <em>carpet</em> cable system, resolving an open problem left by Devyver et al. (2023) <span><span>[26]</span></span>. Second, we prove that two-sided heat kernel estimates <em>alone</em> imply gradient estimates for the heat kernel on strongly recurrent fractal-like cable systems, improving the main results of the aforementioned paper. Third, we obtain Hölder (Lipschitz) estimates for the heat kernel on <em>strongly recurrent</em> metric measure spaces, extending the classical Li-Yau gradient estimate for the heat kernel on Riemannian manifolds.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110797"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146039202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Advances in MathematicsPub Date : 2026-03-01Epub Date: 2026-01-19DOI: 10.1016/j.aim.2026.110787
Ayush Khaitan
{"title":"The weighted ambient metric for manifolds with density","authors":"Ayush Khaitan","doi":"10.1016/j.aim.2026.110787","DOIUrl":"10.1016/j.aim.2026.110787","url":null,"abstract":"<div><div>We prove the existence and uniqueness of a weighted analogue of the Fefferman-Graham ambient metric for manifolds with density. We then show that this ambient metric forms the natural geometric framework for the Ricci flow by constructing infinite families of fully non-linear analogues of Perelman's <span><math><mi>F</mi></math></span> and <span><math><mi>W</mi></math></span> functionals. We extend Perelman's monotonicity result to these two families of functionals under several conditions, including for shrinking solitons and Einstein manifolds. We do so by constructing a “Ricci flow vector field” in the ambient space, which may be of independent research interest. We also prove that the weighted GJMS operators associated with the weighted ambient metric are formally self-adjoint, and that the associated weighted renormalized volume coefficients are variational.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110787"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146039257","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Advances in MathematicsPub Date : 2026-03-01Epub Date: 2026-01-19DOI: 10.1016/j.aim.2026.110790
Pak Tung Ho
{"title":"On the invariant surface area functionals in 3-dimensional CR geometry","authors":"Pak Tung Ho","doi":"10.1016/j.aim.2026.110790","DOIUrl":"10.1016/j.aim.2026.110790","url":null,"abstract":"<div><div>Cheng, Yang, and Zhang have studied two invariant surface area functionals in 3-dimensional CR manifolds. They deduced the Euler–Lagrange equations of the associated energy functionals when the 3-dimensional CR manifold has constant Webster curvature and vanishing torsion. In this paper, we deduce the Euler–Lagrange equations of the energy functionals in a more general 3-dimensional CR manifold. Moreover, we study the invariant area functionals on the disk bundle, on the Rossi sphere, and on 3-dimensional tori. In particular, we show that the Clifford torus is a minimizer for <span><math><msub><mrow><mi>E</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> on the Rossi sphere <span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mi>t</mi></mrow><mrow><mn>3</mn></mrow></msubsup></math></span> when <span><math><mi>t</mi><mo>=</mo><mo>−</mo><mn>4</mn><mo>+</mo><msqrt><mrow><mn>15</mn></mrow></msqrt></math></span>. Also, by computing the second variation formula, we show that the Clifford torus is not a minimizer for <span><math><msub><mrow><mi>E</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> on the Rossi sphere <span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mi>t</mi></mrow><mrow><mn>3</mn></mrow></msubsup></math></span> when <span><math><mi>t</mi><mo>></mo><mo>−</mo><mn>4</mn><mo>+</mo><msqrt><mrow><mn>15</mn></mrow></msqrt></math></span>.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110790"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146039198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Advances in MathematicsPub Date : 2026-03-01Epub Date: 2026-01-19DOI: 10.1016/j.aim.2025.110773
Pedro Abdalla , Afonso S. Bandeira , Martin Kassabov , Victor Souza , Steven H. Strogatz , Alex Townsend
{"title":"Expander graphs are globally synchronizing","authors":"Pedro Abdalla , Afonso S. Bandeira , Martin Kassabov , Victor Souza , Steven H. Strogatz , Alex Townsend","doi":"10.1016/j.aim.2025.110773","DOIUrl":"10.1016/j.aim.2025.110773","url":null,"abstract":"<div><div>The Kuramoto model is fundamental to the study of synchronization. It consists of a collection of oscillators with interactions given by a network, which we identify respectively with vertices and edges of a graph. In this paper, we show that a graph with sufficient expansion must be globally synchronizing, meaning that a homogeneous Kuramoto model of identical oscillators on such a graph will converge to the fully synchronized state with all the oscillators having the same phase, for every initial state up to a set of measure zero. In particular, we show that for any <span><math><mi>ε</mi><mo>></mo><mn>0</mn></math></span> and <span><math><mi>p</mi><mo>⩾</mo><mo>(</mo><mn>1</mn><mo>+</mo><mi>ε</mi><mo>)</mo><mo>(</mo><mi>log</mi><mo></mo><mi>n</mi><mo>)</mo><mo>/</mo><mi>n</mi></math></span>, the homogeneous Kuramoto model on the Erdős–Rényi random graph <span><math><mi>G</mi><mo>(</mo><mi>n</mi><mo>,</mo><mi>p</mi><mo>)</mo></math></span> is globally synchronizing with probability tending to one as <em>n</em> goes to infinity. This improves on a previous result of Kassabov, Strogatz, and Townsend and solves a conjecture of Ling, Xu, and Bandeira. We also show that the Kuramoto model is globally synchronizing on any <em>d</em>-regular Ramanujan graph, and on typical <em>d</em>-regular graphs, for <span><math><mi>d</mi><mo>⩾</mo><mn>600</mn></math></span>.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110773"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146039200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Advances in MathematicsPub Date : 2026-03-01Epub Date: 2025-12-31DOI: 10.1016/j.aim.2025.110758
Gefei Cai , Wen-Bo Li, Tim Mesikepp
{"title":"Quasisymmetric geometry of low-dimensional random spaces","authors":"Gefei Cai , Wen-Bo Li, Tim Mesikepp","doi":"10.1016/j.aim.2025.110758","DOIUrl":"10.1016/j.aim.2025.110758","url":null,"abstract":"<div><div>We investigate several naturally-arising random fractals from the perspective of quasisymmetric geometry, and show that they fall outside the realm of quasisymmetric uniformization to simple canonical spaces. We begin with Brownian motion and various forms of the Schramm-Loewner evolution <span><math><msub><mrow><mi>SLE</mi></mrow><mrow><mi>κ</mi></mrow></msub></math></span> for <span><math><mi>κ</mi><mo>></mo><mn>0</mn></math></span>, showing that a.s. neither is a quasisymmetric to a straight line. We also study the conformal loop ensemble <span><math><msub><mrow><mi>CLE</mi></mrow><mrow><mi>κ</mi></mrow></msub></math></span> for <span><math><mi>κ</mi><mo>∈</mo><mo>(</mo><mfrac><mrow><mn>8</mn></mrow><mrow><mn>3</mn></mrow></mfrac><mo>,</mo><mn>4</mn><mo>]</mo></math></span>, and show that the collection of all points outside the loops is a.s. homeomorphic to the standard Sierpiński carpet, but not quasisymmetrically equivalent to a round carpet.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"487 ","pages":"Article 110758"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Advances in MathematicsPub Date : 2026-03-01Epub Date: 2025-12-30DOI: 10.1016/j.aim.2025.110746
Evangelia Gazaki , Jonathan Love
{"title":"Hyperelliptic curves mapping to abelian varieties and applications to Beilinson's conjecture for zero-cycles","authors":"Evangelia Gazaki , Jonathan Love","doi":"10.1016/j.aim.2025.110746","DOIUrl":"10.1016/j.aim.2025.110746","url":null,"abstract":"<div><div>Let <em>A</em> be an abelian surface over an algebraically closed field <span><math><mover><mrow><mi>k</mi></mrow><mo>‾</mo></mover></math></span> with an embedding <span><math><mover><mrow><mi>k</mi></mrow><mo>‾</mo></mover><mo>↪</mo><mi>C</mi></math></span>. When <em>A</em> is isogenous to a product of elliptic curves, we describe a large collection of pairwise non-isomorphic hyperelliptic curves mapping birationally into <em>A</em>. For infinitely many integers <span><math><mi>g</mi><mo>≥</mo><mn>2</mn></math></span>, this collection has infinitely many curves of genus <em>g</em>, and no two curves in the collection have the same image under any isogeny from <em>A</em>. Using these hyperelliptic curves, we find many rational equivalences in the Chow group of zero-cycles <span><math><msub><mrow><mi>CH</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>(</mo><mi>A</mi><mo>)</mo></math></span>. We use these results to give some progress towards Beilinson's conjecture for zero-cycles, which predicts that for a smooth projective variety <em>X</em> over <span><math><mover><mrow><mi>Q</mi></mrow><mo>‾</mo></mover></math></span> the kernel of the Albanese map of <em>X</em> is zero.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"487 ","pages":"Article 110746"},"PeriodicalIF":1.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}