Pub Date : 2026-01-22DOI: 10.1016/j.aim.2026.110788
Ulrich Bunke , Daniel Kasprowski , Christoph Winges
We prove the Farrell–Jones conjecture for finitary localising invariants with coefficients in left-exact ∞-categories for finitely -amenable groups and, more generally, Dress-Farrell-Hsiang-Jones groups. Our result subsumes and unifies arguments for the K-theory of additive categories and spherical group rings and extends it for example to categories of perfect modules over -ring spectra.
{"title":"On the Farrell–Jones conjecture for localising invariants","authors":"Ulrich Bunke , Daniel Kasprowski , Christoph Winges","doi":"10.1016/j.aim.2026.110788","DOIUrl":"10.1016/j.aim.2026.110788","url":null,"abstract":"<div><div>We prove the Farrell–Jones conjecture for finitary localising invariants with coefficients in left-exact ∞-categories for finitely <span><math><mi>F</mi></math></span>-amenable groups and, more generally, Dress-Farrell-Hsiang-Jones groups. Our result subsumes and unifies arguments for the K-theory of additive categories and spherical group rings and extends it for example to categories of perfect modules over <span><math><msub><mrow><mi>E</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span>-ring spectra.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"489 ","pages":"Article 110788"},"PeriodicalIF":1.5,"publicationDate":"2026-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006653","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}
Pub Date : 2026-01-22DOI: 10.1016/j.aim.2026.110797
Jin Gao , Meng Yang
We introduce a Hölder regularity condition for harmonic functions on metric measure spaces and prove that, under a slow 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 carpet cable system, resolving an open problem left by Devyver et al. (2023) [26]. Second, we prove that two-sided heat kernel estimates alone 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 strongly recurrent metric measure spaces, extending the classical Li-Yau gradient estimate for the heat kernel on Riemannian manifolds.
{"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":"2026-01-22","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}
Pub Date : 2026-01-22DOI: 10.1016/j.aim.2026.110804
Naichung Conan Leung , Qin Li , Ziming Nikolas Ma
In this paper, we explore the quantization of Kähler manifolds, focusing on the relationship between deformation quantization and geometric quantization. We provide a classification of degree 1 formal quantizable functions in the Berezin-Toeplitz deformation quantization, establishing that these formal functions are of the form for a certain smooth (non-formal) function . If is real-valued then corresponds to a Hamiltonian Killing vector field. In the presence of Hamiltonian G-symmetry, we address the compatibility between the infinitesimal symmetry for deformation quantization via quantum moment map and infinitesimal symmetry on geometric quantization acting on Hilbert spaces of holomorphic sections via Berezin-Toeplitz quantization.
{"title":"Symmetry in deformation quantization and geometric quantization","authors":"Naichung Conan Leung , Qin Li , Ziming Nikolas Ma","doi":"10.1016/j.aim.2026.110804","DOIUrl":"10.1016/j.aim.2026.110804","url":null,"abstract":"<div><div>In this paper, we explore the quantization of Kähler manifolds, focusing on the relationship between deformation quantization and geometric quantization. We provide a classification of degree 1 formal quantizable functions in the Berezin-Toeplitz deformation quantization, establishing that these formal functions are of the form <span><math><mi>f</mi><mo>=</mo><msub><mrow><mi>f</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>−</mo><mfrac><mrow><mi>ħ</mi></mrow><mrow><mn>4</mn><mi>π</mi></mrow></mfrac><mo>(</mo><mi>Δ</mi><msub><mrow><mi>f</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>+</mo><mi>c</mi><mo>)</mo></math></span> for a certain smooth (non-formal) function <span><math><msub><mrow><mi>f</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>. If <span><math><msub><mrow><mi>f</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> is real-valued then <span><math><msub><mrow><mi>f</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> corresponds to a Hamiltonian Killing vector field. In the presence of Hamiltonian <em>G</em>-symmetry, we address the compatibility between the infinitesimal symmetry for deformation quantization via quantum moment map and infinitesimal symmetry on geometric quantization acting on Hilbert spaces of holomorphic sections via Berezin-Toeplitz quantization.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"489 ","pages":"Article 110804"},"PeriodicalIF":1.5,"publicationDate":"2026-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146025724","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}
Pub Date : 2026-01-21DOI: 10.1016/j.aim.2026.110801
Garret Sobczyk
{"title":"Corrigendum to “Notes on Plücker's relations in geometric algebra” [Advances in Mathematics 363 (2020) 106959]","authors":"Garret Sobczyk","doi":"10.1016/j.aim.2026.110801","DOIUrl":"10.1016/j.aim.2026.110801","url":null,"abstract":"","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110801"},"PeriodicalIF":1.5,"publicationDate":"2026-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146039195","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}
Pub Date : 2026-01-20DOI: 10.1016/j.aim.2026.110792
Alessandro De Stefani , Luis Núñez-Betancourt , Ilya Smirnov
Introduced by Takagi and Watanabe, F-pure thresholds are invariants defined in terms of the Frobenius homomorphism. While they find applications in various settings, they are primarily used as a local invariant. The purpose of this note is to start filling this gap by opening the study of its behavior on a scheme. To this end, we define the defect of the F-pure threshold of a local ring by setting . It turns out that this invariant defines an upper semi-continuous function on a scheme and satisfies Bertini-type theorems. We also study the behavior of the defect of the F-pure threshold under flat extensions and after blowing up the maximal ideal of a local ring.
{"title":"The defect of the F-pure threshold","authors":"Alessandro De Stefani , Luis Núñez-Betancourt , Ilya Smirnov","doi":"10.1016/j.aim.2026.110792","DOIUrl":"10.1016/j.aim.2026.110792","url":null,"abstract":"<div><div>Introduced by Takagi and Watanabe, F-pure thresholds are invariants defined in terms of the Frobenius homomorphism. While they find applications in various settings, they are primarily used as a <em>local</em> invariant. The purpose of this note is to start filling this gap by opening the study of its behavior on a scheme. To this end, we define the <em>defect of the F-pure threshold</em> of a local ring <span><math><mo>(</mo><mi>R</mi><mo>,</mo><mi>m</mi><mo>)</mo></math></span> by setting <span><math><mi>dfpt</mi><mo>(</mo><mi>R</mi><mo>)</mo><mo>=</mo><mi>dim</mi><mo></mo><mo>(</mo><mi>R</mi><mo>)</mo><mo>−</mo><mi>fpt</mi><mo>(</mo><mi>m</mi><mo>)</mo></math></span>. It turns out that this invariant defines an upper semi-continuous function on a scheme and satisfies Bertini-type theorems. We also study the behavior of the defect of the F-pure threshold under flat extensions and after blowing up the maximal ideal of a local ring.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110792"},"PeriodicalIF":1.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146039203","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}
Pub Date : 2026-01-20DOI: 10.1016/j.aim.2026.110793
Tobias Fritz , Antonio Lorenzin
Gelfand duality is a fundamental result that justifies thinking of general unital -algebras as noncommutative versions of compact Hausdorff spaces. Inspired by this perspective, we investigate what noncommutative measurable spaces should be. This leads us to consider categories of monotone σ-complete -algebras as well as categories of Boolean σ-algebras, which can be thought of as abstract measurable spaces.
Motivated by the search for a good notion of noncommutative measurable space, we provide a unified overview of these categories, alongside those of measurable spaces, and formalize their relationships through functors, adjunctions and equivalences. This includes an equivalence between Boolean σ-algebras and commutative monotone σ-complete -algebras, as well as a Gelfand-type duality adjunction between the latter category and the category of measurable spaces. This duality restricts to two equivalences: one involving standard Borel spaces, which are widely used in probability theory, and another involving the more general Baire measurable spaces. Moreover, this result admits a probabilistic version, where the morphisms are σ-normal cpu maps and Markov kernels, respectively.
We hope that these developments can also contribute to the ongoing search for a well-behaved Markov category for measure-theoretic probability beyond the standard Borel setting — an open problem in the current state of the art.
{"title":"Categories of abstract and noncommutative measurable spaces","authors":"Tobias Fritz , Antonio Lorenzin","doi":"10.1016/j.aim.2026.110793","DOIUrl":"10.1016/j.aim.2026.110793","url":null,"abstract":"<div><div>Gelfand duality is a fundamental result that justifies thinking of general unital <span><math><msup><mrow><mi>C</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span>-algebras as noncommutative versions of compact Hausdorff spaces. Inspired by this perspective, we investigate what noncommutative measurable spaces should be. This leads us to consider categories of monotone <em>σ</em>-complete <span><math><msup><mrow><mi>C</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span>-algebras as well as categories of Boolean <em>σ</em>-algebras, which can be thought of as abstract measurable spaces.</div><div>Motivated by the search for a good notion of noncommutative measurable space, we provide a unified overview of these categories, alongside those of measurable spaces, and formalize their relationships through functors, adjunctions and equivalences. This includes an equivalence between Boolean <em>σ</em>-algebras and commutative monotone <em>σ</em>-complete <span><math><msup><mrow><mi>C</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span>-algebras, as well as a Gelfand-type duality adjunction between the latter category and the category of measurable spaces. This duality restricts to two equivalences: one involving standard Borel spaces, which are widely used in probability theory, and another involving the more general Baire measurable spaces. Moreover, this result admits a probabilistic version, where the morphisms are <em>σ</em>-normal cpu maps and Markov kernels, respectively.</div><div>We hope that these developments can also contribute to the ongoing search for a well-behaved Markov category for measure-theoretic probability beyond the standard Borel setting — an open problem in the current state of the art.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110793"},"PeriodicalIF":1.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146039201","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}
Pub Date : 2026-01-20DOI: 10.1016/j.aim.2026.110795
Yuan Gao
For a stopped Liouville manifold arising from a Liouville sector, we construct a symplectic analogue of the formal neighborhood of the stop on the level of Fukaya categories. This geometric construction is performed via Floer-theoretic methods by allowing wrappings in the negative direction. On the other hand, inspired by homological mirror symmetry for pairs, where the mirror is the formal neighborhood of a divisor in an ambient projective variety, there is a different approach by taking a ‘categorical formal completion’ introduced by Efimov. Our main result establishes equivalence of these two approaches, confirms computability of this new type of Floer theory by categorical and algebraic means, and indicates contributions from and to computations in homological mirror symmetry.
{"title":"Fukaya A∞-structure near infinity and the categorical formal completion","authors":"Yuan Gao","doi":"10.1016/j.aim.2026.110795","DOIUrl":"10.1016/j.aim.2026.110795","url":null,"abstract":"<div><div>For a stopped Liouville manifold arising from a Liouville sector, we construct a symplectic analogue of the formal neighborhood of the stop on the level of Fukaya categories. This geometric construction is performed via Floer-theoretic methods by allowing wrappings in the negative direction. On the other hand, inspired by homological mirror symmetry for pairs, where the mirror is the formal neighborhood of a divisor in an ambient projective variety, there is a different approach by taking a ‘categorical formal completion’ introduced by Efimov. Our main result establishes equivalence of these two approaches, confirms computability of this new type of Floer theory by categorical and algebraic means, and indicates contributions from and to computations in homological mirror symmetry.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110795"},"PeriodicalIF":1.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146039194","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}
Pub Date : 2026-01-20DOI: 10.1016/j.aim.2026.110796
Victor Falgas–Ravry , Eero Räty , István Tomon
<div><div>Consider the partially ordered set on <span><math><msup><mrow><mo>[</mo><mi>t</mi><mo>]</mo></mrow><mrow><mi>n</mi></mrow></msup><mo>:</mo><mo>=</mo><msup><mrow><mo>{</mo><mn>0</mn><mo>,</mo><mo>…</mo><mo>,</mo><mi>t</mi><mo>−</mo><mn>1</mn><mo>}</mo></mrow><mrow><mi>n</mi></mrow></msup></math></span> equipped with the natural coordinate-wise ordering, and let <span><math><mi>A</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo></math></span> denote the number of antichains of this poset. Determining <span><math><mi>A</mi><mo>(</mo><mn>2</mn><mo>,</mo><mi>n</mi><mo>)</mo></math></span> is the celebrated problem of Dedekind from 1897, and the general quantity <span><math><mi>A</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo></math></span> has a number of combinatorial interpretations: it is precisely the number of <span><math><mo>(</mo><mi>n</mi><mo>−</mo><mn>1</mn><mo>)</mo></math></span>-dimensional partitions with entries from <span><math><mo>{</mo><mn>0</mn><mo>,</mo><mo>…</mo><mo>,</mo><mi>t</mi><mo>}</mo></math></span>, and by a result of Moshkovitz and Shapira, <span><math><mi>A</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo><mo>+</mo><mn>1</mn></math></span> is equal to the <em>n</em>-color Ramsey number of monotone paths of length <em>t</em> in 3-uniform hypergraphs. This has led to significant interest in the growth rate of <span><math><mi>A</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo></math></span>.</div><div>Trivially, <span><math><msub><mrow><mi>log</mi></mrow><mrow><mn>2</mn></mrow></msub><mo></mo><mi>A</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo><mo>≥</mo><mi>α</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo></math></span>, where <span><math><mi>α</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo></math></span> is the size of a maximal antichain in <span><math><msup><mrow><mo>[</mo><mi>t</mi><mo>]</mo></mrow><mrow><mi>n</mi></mrow></msup></math></span>. In the present paper, we prove that this simple lower bound is close to optimal, in particular for every <span><math><mi>t</mi><mo>,</mo><mi>n</mi><mo>≥</mo><mn>2</mn></math></span>,<span><span><span><math><msub><mrow><mi>log</mi></mrow><mrow><mn>2</mn></mrow></msub><mo></mo><mi>A</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo><mo>≤</mo><mrow><mo>(</mo><mn>1</mn><mo>+</mo><mi>O</mi><mrow><mo>(</mo><mfrac><mrow><msup><mrow><mo>(</mo><mi>log</mi><mo></mo><mi>n</mi><mo>)</mo></mrow><mrow><mn>3</mn></mrow></msup></mrow><mrow><mi>n</mi></mrow></mfrac><mo>)</mo></mrow><mo>)</mo></mrow><mo>⋅</mo><mi>α</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo><mo>.</mo></math></span></span></span> This resolves a conjecture of Moshkovitz and Shapira, and gives the first bound that is close to optimal for growing <em>t</em>. Our proof is based on the graph container method, partly inspired by previous work of Pohoata and Zakharov.</div><div>One of our main contributions is a novel supersaturation result in <span><math><msup><mrow><
{"title":"Dedekind's problem in the hypergrid","authors":"Victor Falgas–Ravry , Eero Räty , István Tomon","doi":"10.1016/j.aim.2026.110796","DOIUrl":"10.1016/j.aim.2026.110796","url":null,"abstract":"<div><div>Consider the partially ordered set on <span><math><msup><mrow><mo>[</mo><mi>t</mi><mo>]</mo></mrow><mrow><mi>n</mi></mrow></msup><mo>:</mo><mo>=</mo><msup><mrow><mo>{</mo><mn>0</mn><mo>,</mo><mo>…</mo><mo>,</mo><mi>t</mi><mo>−</mo><mn>1</mn><mo>}</mo></mrow><mrow><mi>n</mi></mrow></msup></math></span> equipped with the natural coordinate-wise ordering, and let <span><math><mi>A</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo></math></span> denote the number of antichains of this poset. Determining <span><math><mi>A</mi><mo>(</mo><mn>2</mn><mo>,</mo><mi>n</mi><mo>)</mo></math></span> is the celebrated problem of Dedekind from 1897, and the general quantity <span><math><mi>A</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo></math></span> has a number of combinatorial interpretations: it is precisely the number of <span><math><mo>(</mo><mi>n</mi><mo>−</mo><mn>1</mn><mo>)</mo></math></span>-dimensional partitions with entries from <span><math><mo>{</mo><mn>0</mn><mo>,</mo><mo>…</mo><mo>,</mo><mi>t</mi><mo>}</mo></math></span>, and by a result of Moshkovitz and Shapira, <span><math><mi>A</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo><mo>+</mo><mn>1</mn></math></span> is equal to the <em>n</em>-color Ramsey number of monotone paths of length <em>t</em> in 3-uniform hypergraphs. This has led to significant interest in the growth rate of <span><math><mi>A</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo></math></span>.</div><div>Trivially, <span><math><msub><mrow><mi>log</mi></mrow><mrow><mn>2</mn></mrow></msub><mo></mo><mi>A</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo><mo>≥</mo><mi>α</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo></math></span>, where <span><math><mi>α</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo></math></span> is the size of a maximal antichain in <span><math><msup><mrow><mo>[</mo><mi>t</mi><mo>]</mo></mrow><mrow><mi>n</mi></mrow></msup></math></span>. In the present paper, we prove that this simple lower bound is close to optimal, in particular for every <span><math><mi>t</mi><mo>,</mo><mi>n</mi><mo>≥</mo><mn>2</mn></math></span>,<span><span><span><math><msub><mrow><mi>log</mi></mrow><mrow><mn>2</mn></mrow></msub><mo></mo><mi>A</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo><mo>≤</mo><mrow><mo>(</mo><mn>1</mn><mo>+</mo><mi>O</mi><mrow><mo>(</mo><mfrac><mrow><msup><mrow><mo>(</mo><mi>log</mi><mo></mo><mi>n</mi><mo>)</mo></mrow><mrow><mn>3</mn></mrow></msup></mrow><mrow><mi>n</mi></mrow></mfrac><mo>)</mo></mrow><mo>)</mo></mrow><mo>⋅</mo><mi>α</mi><mo>(</mo><mi>t</mi><mo>,</mo><mi>n</mi><mo>)</mo><mo>.</mo></math></span></span></span> This resolves a conjecture of Moshkovitz and Shapira, and gives the first bound that is close to optimal for growing <em>t</em>. Our proof is based on the graph container method, partly inspired by previous work of Pohoata and Zakharov.</div><div>One of our main contributions is a novel supersaturation result in <span><math><msup><mrow><","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110796"},"PeriodicalIF":1.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146039197","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}
Pub Date : 2026-01-19DOI: 10.1016/j.aim.2026.110790
Pak Tung Ho
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 on the Rossi sphere when . Also, by computing the second variation formula, we show that the Clifford torus is not a minimizer for on the Rossi sphere when .
{"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":"2026-01-19","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}
Pub Date : 2026-01-19DOI: 10.1016/j.aim.2025.110773
Pedro Abdalla , Afonso S. Bandeira , Martin Kassabov , Victor Souza , Steven H. Strogatz , Alex Townsend
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 and , the homogeneous Kuramoto model on the Erdős–Rényi random graph is globally synchronizing with probability tending to one as n 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 d-regular Ramanujan graph, and on typical d-regular graphs, for .
{"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":"2026-01-19","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}