Pub Date : 2026-01-15DOI: 10.1016/j.aim.2025.110762
Dimitri Ara , Léonard Guetta
Motivated by the Grothendieck construction, we study the functorialities of the comma construction for strict ω-categories. To state the most general functorialities, we use the language of Gray ω-categories, that is, categories enriched in the category of strict ω-categories endowed with the oplax Gray tensor product. Our main result is that the comma construction of strict ω-categories defines a Gray ω-functor, that is, a morphism of Gray ω-categories. To makes sense of this statement, we prove that slices of Gray ω-categories exist. Coming back to the Grothendieck construction, we propose a definition in terms of the comma construction and, as a consequence, we get that the Grothendieck construction of strict ω-categories defines a Gray ω-functor. Finally, as a by-product, we get a notion of Grothendieck construction for Gray ω-functors, which we plan to investigate in future work.
{"title":"Lax functorialities of the comma construction for ω-categories","authors":"Dimitri Ara , Léonard Guetta","doi":"10.1016/j.aim.2025.110762","DOIUrl":"10.1016/j.aim.2025.110762","url":null,"abstract":"<div><div>Motivated by the Grothendieck construction, we study the functorialities of the comma construction for strict <em>ω</em>-categories. To state the most general functorialities, we use the language of Gray <em>ω</em>-categories, that is, categories enriched in the category of strict <em>ω</em>-categories endowed with the oplax Gray tensor product. Our main result is that the comma construction of strict <em>ω</em>-categories defines a Gray <em>ω</em>-functor, that is, a morphism of Gray <em>ω</em>-categories. To makes sense of this statement, we prove that slices of Gray <em>ω</em>-categories exist. Coming back to the Grothendieck construction, we propose a definition in terms of the comma construction and, as a consequence, we get that the Grothendieck construction of strict <em>ω</em>-categories defines a Gray <em>ω</em>-functor. Finally, as a by-product, we get a notion of Grothendieck construction for Gray <em>ω</em>-functors, which we plan to investigate in future work.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110762"},"PeriodicalIF":1.5,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145981068","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 : 2026-01-15DOI: 10.1016/j.aim.2026.110785
Tal Gottesman
We prove that the bounded derived category of the lattice of order ideals of the product of two ordered chains is fractionally Calabi–Yau. We also show that these lattices are derived equivalent to higher Auslander algebras of type A. The proofs involve the study of intervals of the poset that have resolutions described with antichains having rigid properties. These two results combined corroborate a conjecture by Chapoton linking posets to Fukaya–Seidel Categories.
{"title":"Fractionally Calabi–Yau lattices that tilt to higher Auslander algebras of type A","authors":"Tal Gottesman","doi":"10.1016/j.aim.2026.110785","DOIUrl":"10.1016/j.aim.2026.110785","url":null,"abstract":"<div><div>We prove that the bounded derived category of the lattice of order ideals of the product of two ordered chains is fractionally Calabi–Yau. We also show that these lattices are derived equivalent to higher Auslander algebras of type A. The proofs involve the study of intervals of the poset that have resolutions described with antichains having rigid properties. These two results combined corroborate a conjecture by Chapoton linking posets to Fukaya–Seidel Categories.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110785"},"PeriodicalIF":1.5,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145981070","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 : 2026-01-15DOI: 10.1016/j.aim.2026.110786
Zhu Ye
Let M be an open (i.e. complete and noncompact) manifold with nonnegative Ricci curvature. In this paper, we study whether the volume growth order of M is always greater than or equal to the dimension of some (or every) asymptotic cone of M.
Our first main result asserts that, under the conic at infinity condition, if the infimum of the volume growth order of M equals k, then there exists an asymptotic cone of M whose upper box dimension is at most k. In particular, this yields a complete affirmative answer to our problem in the setting of nonnegative sectional curvature.
In the subsequent part of the paper, we extend or partially extend Sormani's results concerning M with linear volume growth to more relaxed volume growth conditions. Our approach also allows us to present a new proof of Sormani's sublinear diameter growth theorem for open manifolds with and linear volume growth.
Finally, we construct an example of an open n-manifold M with whose volume growth order oscillates between 1 and n.
{"title":"Volume growth and asymptotic cones of manifolds with nonnegative Ricci curvature","authors":"Zhu Ye","doi":"10.1016/j.aim.2026.110786","DOIUrl":"10.1016/j.aim.2026.110786","url":null,"abstract":"<div><div>Let <em>M</em> be an open (i.e. complete and noncompact) manifold with nonnegative Ricci curvature. In this paper, we study whether the volume growth order of <em>M</em> is always greater than or equal to the dimension of some (or every) asymptotic cone of <em>M</em>.</div><div>Our first main result asserts that, under the conic at infinity condition, if the infimum of the volume growth order of <em>M</em> equals <em>k</em>, then there exists an asymptotic cone of <em>M</em> whose upper box dimension is at most <em>k</em>. In particular, this yields a complete affirmative answer to our problem in the setting of nonnegative sectional curvature.</div><div>In the subsequent part of the paper, we extend or partially extend Sormani's results concerning <em>M</em> with linear volume growth to more relaxed volume growth conditions. Our approach also allows us to present a new proof of Sormani's sublinear diameter growth theorem for open manifolds with <span><math><mrow><mi>Ric</mi></mrow><mo>≥</mo><mn>0</mn></math></span> and linear volume growth.</div><div>Finally, we construct an example of an open <em>n</em>-manifold <em>M</em> with <span><math><msub><mrow><mi>sec</mi></mrow><mrow><mi>M</mi></mrow></msub><mo>≥</mo><mn>0</mn></math></span> whose volume growth order oscillates between 1 and <em>n</em>.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110786"},"PeriodicalIF":1.5,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145981226","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 : 2026-01-14DOI: 10.1016/j.aim.2025.110774
Avy Soffer , Xiaoxu Wu
For the Schrödinger equation with a general interaction term, which may be linear or nonlinear, time dependent and including charge transfer potentials, we prove the global solutions are asymptotically given by the sum of a free wave and a weakly localized part. The proof is based on constructing in an adapted way the Free Channel Wave Operator, and further tools from the recent works [21], [22], [35]. This work generalizes the results of the first part of [21], [22] to arbitrary dimension, and non-radial data.
{"title":"On the large time asymptotics of Schrödinger type equations with general data","authors":"Avy Soffer , Xiaoxu Wu","doi":"10.1016/j.aim.2025.110774","DOIUrl":"10.1016/j.aim.2025.110774","url":null,"abstract":"<div><div>For the Schrödinger equation with a general interaction term, which may be linear or nonlinear, time dependent and including charge transfer potentials, we prove the global solutions are asymptotically given by the sum of a free wave and a weakly localized part. The proof is based on constructing in an adapted way the Free Channel Wave Operator, and further tools from the recent works <span><span>[21]</span></span>, <span><span>[22]</span></span>, <span><span>[35]</span></span>. This work generalizes the results of the first part of <span><span>[21]</span></span>, <span><span>[22]</span></span> to arbitrary dimension, and non-radial data.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110774"},"PeriodicalIF":1.5,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145981067","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 : 2026-01-14DOI: 10.1016/j.aim.2025.110770
Lukas Müller , Christoph Schweigert , Lukas Woike , Yang Yang
The Levin-Wen string-nets of a spherical fusion category describe, by results of Kirillov and Bartlett, the representations of mapping class groups of closed surfaces obtained from the Turaev-Viro construction applied to . We provide a far-reaching generalization of this statement to arbitrary pivotal finite tensor categories, including non-semisimple or non-spherical ones: We show that the finitely cocompleted string-net modular functor built from the projective objects of a pivotal finite tensor category is equivalent to Lyubashenko's modular functor built from the Drinfeld center .
{"title":"The Lyubashenko modular functor for Drinfeld centers via non-semisimple string-nets","authors":"Lukas Müller , Christoph Schweigert , Lukas Woike , Yang Yang","doi":"10.1016/j.aim.2025.110770","DOIUrl":"10.1016/j.aim.2025.110770","url":null,"abstract":"<div><div>The Levin-Wen string-nets of a spherical fusion category <span><math><mi>C</mi></math></span> describe, by results of Kirillov and Bartlett, the representations of mapping class groups of closed surfaces obtained from the Turaev-Viro construction applied to <span><math><mi>C</mi></math></span>. We provide a far-reaching generalization of this statement to arbitrary pivotal finite tensor categories, including non-semisimple or non-spherical ones: We show that the finitely cocompleted string-net modular functor built from the projective objects of a pivotal finite tensor category is equivalent to Lyubashenko's modular functor built from the Drinfeld center <span><math><mi>Z</mi><mo>(</mo><mi>C</mi><mo>)</mo></math></span>.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110770"},"PeriodicalIF":1.5,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145981069","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 : 2026-01-13DOI: 10.1016/j.aim.2025.110768
Caleb Eckhardt , Jianchao Wu
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 -algebras.
{"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":"2026-01-13","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}
Pub Date : 2026-01-13DOI: 10.1016/j.aim.2025.110771
Laurenţiu Maxim , Jörg Schürmann
<div><div>We give a <em>K</em>-theoretic and geometric interpretation for a generalized weighted Ehrhart theory of a full-dimensional lattice polytope <em>P</em>, depending on a given homogeneous polynomial function <em>φ</em> on <em>P</em>, and with Laurent polynomial weights <span><math><msub><mrow><mi>f</mi></mrow><mrow><mi>Q</mi></mrow></msub><mo>(</mo><mi>y</mi><mo>)</mo><mo>∈</mo><mi>Z</mi><mo>[</mo><msup><mrow><mi>y</mi></mrow><mrow><mo>±</mo><mn>1</mn></mrow></msup><mo>]</mo></math></span> associated to the faces <span><math><mi>Q</mi><mo>⪯</mo><mi>P</mi></math></span> of the polytope. For this purpose, we calculate equivariant <em>K</em>-theoretic Hodge–Chern classes of a torus-equivariant mixed Hodge module <span><math><mi>M</mi></math></span> on the toric variety <span><math><msub><mrow><mi>X</mi></mrow><mrow><mi>P</mi></mrow></msub></math></span> associated to <em>P</em> (defined via an equivariant embedding of <span><math><msub><mrow><mi>X</mi></mrow><mrow><mi>P</mi></mrow></msub></math></span> into an ambient smooth variety). For any integer <em>ℓ</em>, we introduce a corresponding equivariant Hodge <span><math><msub><mrow><mi>χ</mi></mrow><mrow><mi>y</mi></mrow></msub></math></span>-polynomial <span><math><msub><mrow><mi>χ</mi></mrow><mrow><mi>y</mi></mrow></msub><mo>(</mo><msub><mrow><mi>X</mi></mrow><mrow><mi>P</mi></mrow></msub><mo>,</mo><mi>ℓ</mi><msub><mrow><mi>D</mi></mrow><mrow><mi>P</mi></mrow></msub><mo>;</mo><mo>[</mo><mi>M</mi><mo>]</mo><mo>)</mo></math></span>, with <span><math><msub><mrow><mi>D</mi></mrow><mrow><mi>P</mi></mrow></msub></math></span> the corresponding ample Cartier divisor on <span><math><msub><mrow><mi>X</mi></mrow><mrow><mi>P</mi></mrow></msub></math></span> (defined by the facet presentation of <em>P</em>). Motivic properties of the Hodge–Chern classes are used to express this equivariant Hodge polynomial in terms of weighted character sums fitting with a generalized weighted Ehrhart theory. The equivariant Hodge polynomials are shown to satisfy a reciprocity and purity formula fitting with the duality for equivariant mixed Hodge modules, and implying the corresponding properties for the generalized weighted Ehrhart polynomials. In the special case of the equivariant intersection cohomology mixed Hodge module, with the weight function corresponding to Stanley's <em>g</em>-function of the polar polytope of <em>P</em>, we recover in geometric terms a recent combinatorial formula of Beck–Gunnells–Materov. More generally, motivated by the analogy to the Kazhdan–Lusztig theory, we introduce a duality involution on the free <span><math><mi>Z</mi><mo>[</mo><msup><mrow><mi>y</mi></mrow><mrow><mo>±</mo><mn>1</mn></mrow></msup><mo>]</mo></math></span>-module of weight functions corresponding to the duality of equivariant mixed Hodge modules, and prove a new reciprocity formula in terms of this duality. This unifies and generalizes the classical reciprocity formula of Brion–Vergne in Ehrhart theory as well as t
{"title":"Weighted Ehrhart theory via equivariant toric geometry","authors":"Laurenţiu Maxim , Jörg Schürmann","doi":"10.1016/j.aim.2025.110771","DOIUrl":"10.1016/j.aim.2025.110771","url":null,"abstract":"<div><div>We give a <em>K</em>-theoretic and geometric interpretation for a generalized weighted Ehrhart theory of a full-dimensional lattice polytope <em>P</em>, depending on a given homogeneous polynomial function <em>φ</em> on <em>P</em>, and with Laurent polynomial weights <span><math><msub><mrow><mi>f</mi></mrow><mrow><mi>Q</mi></mrow></msub><mo>(</mo><mi>y</mi><mo>)</mo><mo>∈</mo><mi>Z</mi><mo>[</mo><msup><mrow><mi>y</mi></mrow><mrow><mo>±</mo><mn>1</mn></mrow></msup><mo>]</mo></math></span> associated to the faces <span><math><mi>Q</mi><mo>⪯</mo><mi>P</mi></math></span> of the polytope. For this purpose, we calculate equivariant <em>K</em>-theoretic Hodge–Chern classes of a torus-equivariant mixed Hodge module <span><math><mi>M</mi></math></span> on the toric variety <span><math><msub><mrow><mi>X</mi></mrow><mrow><mi>P</mi></mrow></msub></math></span> associated to <em>P</em> (defined via an equivariant embedding of <span><math><msub><mrow><mi>X</mi></mrow><mrow><mi>P</mi></mrow></msub></math></span> into an ambient smooth variety). For any integer <em>ℓ</em>, we introduce a corresponding equivariant Hodge <span><math><msub><mrow><mi>χ</mi></mrow><mrow><mi>y</mi></mrow></msub></math></span>-polynomial <span><math><msub><mrow><mi>χ</mi></mrow><mrow><mi>y</mi></mrow></msub><mo>(</mo><msub><mrow><mi>X</mi></mrow><mrow><mi>P</mi></mrow></msub><mo>,</mo><mi>ℓ</mi><msub><mrow><mi>D</mi></mrow><mrow><mi>P</mi></mrow></msub><mo>;</mo><mo>[</mo><mi>M</mi><mo>]</mo><mo>)</mo></math></span>, with <span><math><msub><mrow><mi>D</mi></mrow><mrow><mi>P</mi></mrow></msub></math></span> the corresponding ample Cartier divisor on <span><math><msub><mrow><mi>X</mi></mrow><mrow><mi>P</mi></mrow></msub></math></span> (defined by the facet presentation of <em>P</em>). Motivic properties of the Hodge–Chern classes are used to express this equivariant Hodge polynomial in terms of weighted character sums fitting with a generalized weighted Ehrhart theory. The equivariant Hodge polynomials are shown to satisfy a reciprocity and purity formula fitting with the duality for equivariant mixed Hodge modules, and implying the corresponding properties for the generalized weighted Ehrhart polynomials. In the special case of the equivariant intersection cohomology mixed Hodge module, with the weight function corresponding to Stanley's <em>g</em>-function of the polar polytope of <em>P</em>, we recover in geometric terms a recent combinatorial formula of Beck–Gunnells–Materov. More generally, motivated by the analogy to the Kazhdan–Lusztig theory, we introduce a duality involution on the free <span><math><mi>Z</mi><mo>[</mo><msup><mrow><mi>y</mi></mrow><mrow><mo>±</mo><mn>1</mn></mrow></msup><mo>]</mo></math></span>-module of weight functions corresponding to the duality of equivariant mixed Hodge modules, and prove a new reciprocity formula in terms of this duality. This unifies and generalizes the classical reciprocity formula of Brion–Vergne in Ehrhart theory as well as t","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110771"},"PeriodicalIF":1.5,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145981072","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 : 2026-01-12DOI: 10.1016/j.aim.2025.110765
Tyler Arant , Alexander S. Kechris , Patrick Lutz
This paper is devoted to the study of analytic equivalence relations which are Borel graphable, i.e. which can be realized as the connectedness relation of a Borel graph. Our main focus is the question of which analytic equivalence relations are Borel graphable. First, we study an equivalence relation arising from the theory of countable admissible ordinals and show that it is Borel graphable if and only if there is a non-constructible real. As a corollary of the proof, we construct an analytic equivalence relation which is (provably in ) not Borel graphable and an effectively analytic equivalence relation which is Borel graphable but not effectively Borel graphable. Next, we study analytic equivalence relations given by the isomorphism relation for some class of countable structures. We show that all such equivalence relations are Borel graphable, which implies that for every Borel action of , the associated orbit equivalence relation is Borel graphable. This leads us to study the class of Polish groups whose Borel actions always give rise to Borel graphable orbit equivalence relations; we refer to such groups as graphic groups. We show that besides , the class of graphic groups includes all connected Polish groups and is closed under countable products. We finish by studying structural properties of the class of Borel graphable analytic equivalence relations and by considering two variations on Borel graphability: a generalization with hypergraphs instead of graphs and an analogue of Borel graphability in the setting of computably enumerable equivalence relations.
{"title":"Borel graphable equivalence relations","authors":"Tyler Arant , Alexander S. Kechris , Patrick Lutz","doi":"10.1016/j.aim.2025.110765","DOIUrl":"10.1016/j.aim.2025.110765","url":null,"abstract":"<div><div>This paper is devoted to the study of analytic equivalence relations which are <em>Borel graphable</em>, i.e. which can be realized as the connectedness relation of a Borel graph. Our main focus is the question of which analytic equivalence relations are Borel graphable. First, we study an equivalence relation arising from the theory of countable admissible ordinals and show that it is Borel graphable if and only if there is a non-constructible real. As a corollary of the proof, we construct an analytic equivalence relation which is (provably in <span><math><mi>ZFC</mi></math></span>) not Borel graphable and an effectively analytic equivalence relation which is Borel graphable but not effectively Borel graphable. Next, we study analytic equivalence relations given by the isomorphism relation for some class of countable structures. We show that all such equivalence relations are Borel graphable, which implies that for every Borel action of <span><math><msub><mrow><mi>S</mi></mrow><mrow><mo>∞</mo></mrow></msub></math></span>, the associated orbit equivalence relation is Borel graphable. This leads us to study the class of Polish groups whose Borel actions always give rise to Borel graphable orbit equivalence relations; we refer to such groups as <em>graphic groups.</em> We show that besides <span><math><msub><mrow><mi>S</mi></mrow><mrow><mo>∞</mo></mrow></msub></math></span>, the class of graphic groups includes all connected Polish groups and is closed under countable products. We finish by studying structural properties of the class of Borel graphable analytic equivalence relations and by considering two variations on Borel graphability: a generalization with hypergraphs instead of graphs and an analogue of Borel graphability in the setting of computably enumerable equivalence relations.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"487 ","pages":"Article 110765"},"PeriodicalIF":1.5,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978919","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 : 2026-01-12DOI: 10.1016/j.aim.2025.110777
S. Estrada , X.H. Fu , I. Herzog , S. Odabaşı
A cocomplete additive category may be equipped with the transfinite filtration of inductive ordinal powers of an ideal . If is a subcategory of an exact category, the -ghost morphisms, i.e., the morphisms right Ext-orthogonal to , form such an ideal and the corresponding transfinite filtration is bounded below by the ideal of morphisms that factor through an object in the subcategory of right Ext-perpendicular objects. The question of convergence for this filtration yields a transfinite formulation of the Generating Hypothesis. For an ordinal λ, the Generalized λ-Generating Hypothesis is the proposition that the λ-th power of the ideal of -ghost morphisms is the (object) ideal of morphisms that factor through an object in . It is shown to hold when the category is a locally λ-presentable Grothendieck category and is a set of λ-presentable objects.
Two cases of interest are treated: when the exact category is the category of chain complexes of left R-modules, then the ideal of morphisms that are trivial on homology are the ghosts with respect to the subcategory of Cartan-Eilenberg projectives and the Generalized ω-Generating Hypothesis is shown to hold; when the exact category is the module category R-Mod for a ring whose left pure projective modules are closed under extension, then an analysis of the transfinite filtration induced by the FP-ghost ideal shows that every left FP-projective module is pure projective.
{"title":"Powers of ghost ideals","authors":"S. Estrada , X.H. Fu , I. Herzog , S. Odabaşı","doi":"10.1016/j.aim.2025.110777","DOIUrl":"10.1016/j.aim.2025.110777","url":null,"abstract":"<div><div>A cocomplete additive category <span><math><mi>A</mi></math></span> may be equipped with the transfinite filtration of inductive ordinal powers of an ideal <span><math><mi>I</mi><mspace></mspace><mo>◃</mo><mspace></mspace><mi>A</mi></math></span>. If <span><math><mi>S</mi><mo>⊆</mo><mi>A</mi></math></span> is a subcategory of an exact category, the <span><math><mi>S</mi></math></span>-ghost morphisms, i.e., the morphisms right Ext-orthogonal to <span><math><mi>S</mi></math></span>, form such an ideal and the corresponding transfinite filtration is bounded below by the ideal of morphisms that factor through an object in the subcategory <span><math><msup><mrow><mi>S</mi></mrow><mrow><mo>⊥</mo></mrow></msup></math></span> of right Ext-perpendicular objects. The question of convergence for this filtration yields a transfinite formulation of the Generating Hypothesis. For an ordinal <em>λ</em>, the Generalized <em>λ</em>-Generating Hypothesis is the proposition that the <em>λ</em>-th power of the ideal of <span><math><mi>S</mi></math></span>-ghost morphisms is the (object) ideal of morphisms that factor through an object in <span><math><msup><mrow><mi>S</mi></mrow><mrow><mo>⊥</mo></mrow></msup></math></span>. It is shown to hold when the category <span><math><mi>A</mi></math></span> is a locally <em>λ</em>-presentable Grothendieck category and <span><math><mi>S</mi></math></span> is a set of <em>λ</em>-presentable objects.</div><div>Two cases of interest are treated: when the exact category is the category <span><math><mi>C</mi><mo>(</mo><mi>R</mi><mo>)</mo></math></span> of chain complexes of left <em>R</em>-modules, then the ideal of morphisms that are trivial on homology are the ghosts with respect to the subcategory of Cartan-Eilenberg projectives and the Generalized <em>ω</em>-Generating Hypothesis is shown to hold; when the exact category is the module category <em>R</em>-Mod for a ring whose left pure projective modules are closed under extension, then an analysis of the transfinite filtration induced by the FP-ghost ideal shows that every left FP-projective module is pure projective.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"488 ","pages":"Article 110777"},"PeriodicalIF":1.5,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145950181","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}
Inspired by work of the first and second authors, this paper studies the Gromov width of the disk cotangent bundle of spheroids and Zoll spheres of revolution. This is achieved with the use of techniques from integrable systems and embedded contact homology capacities.
{"title":"Gromov width of the disk cotangent bundle of spheres of revolution","authors":"Brayan Ferreira , Vinicius G.B. Ramos , Alejandro Vicente","doi":"10.1016/j.aim.2025.110761","DOIUrl":"10.1016/j.aim.2025.110761","url":null,"abstract":"<div><div>Inspired by work of the first and second authors, this paper studies the Gromov width of the disk cotangent bundle of spheroids and Zoll spheres of revolution. This is achieved with the use of techniques from integrable systems and embedded contact homology capacities.</div></div>","PeriodicalId":50860,"journal":{"name":"Advances in Mathematics","volume":"487 ","pages":"Article 110761"},"PeriodicalIF":1.5,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928076","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}