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For a large class of geometric objects, the passage to categories of quasi-coherent sheaves provides an embedding in the 2-category of abelian tensor categories. The notion of weakly Tannakian categories introduced by the author gives a…

Algebraic Geometry · Mathematics 2018-05-10 Daniel Schäppi

As a formulation of 'codimension-two arguments' in invariant theory, we define a (rational) almost principal bundle. It is a principal bundle off closed subsets of codimension two or more. We discuss the behavior of the category of…

Algebraic Geometry · Mathematics 2015-03-10 Mitsuyasu Hashimoto

We investigate some basic descriptive set theory for countably based completely quasi-metrizable topological spaces, which we refer to as quasi-Polish spaces. These spaces naturally generalize much of the classical descriptive set theory of…

Logic · Mathematics 2012-11-07 Matthew de Brecht

In this paper we establish Koszul duality between dg categories and a class of curved coalgebras, generalizing the corresponding result for dg algebras and conilpotent curved coalgebras. We show that the normalized chain complex functor…

Category Theory · Mathematics 2024-01-29 Julian Holstein , Andrey Lazarev

We obtain necessary and sufficient conditions to determine the existence of presymplectic forms of a given rank on all almost abelian Lie algebras. We also study the moduli space of presymplectic forms (this is the set of all closed 2-forms…

Differential Geometry · Mathematics 2026-02-17 Luis Pedro Castellanos Moscoso

Let k be a commutative ring with unit. We endow the categories of filtered complexes and of bicomplexes of k-modules, with cofibrantly generated model structures, where the class of weak equivalences is given by those morphisms inducing a…

Algebraic Topology · Mathematics 2020-12-09 Joana Cirici , Daniela Egas Santander , Muriel Livernet , Sarah Whitehouse

It is shown that the category of presheaves of simplicial groupoids and the category of presheaves of 2-groupoids have Quillen closed model structures. Furthermore, their homotopy categories are equivalent to the homotopy categories of…

Algebraic Topology · Mathematics 2009-02-06 Zhi-Ming Luo , Peter Bubenik , Peter T. Kim

Nearly Frobenius structures and 2-dimensional Almost TQFTs were introduced and shown to be in categorical equivalence in arXiv:1907.05470 in the attempt to extend the Atiyah-Segal's definition to the category of infinite dimensional vector…

Algebraic Geometry · Mathematics 2025-11-14 William Davis , Olivia Dumitrescu

Evenly convex sets in a topological vector space are defined as the intersection of a family of open half spaces. We introduce a generalization of this concept in the conditional framework and provide a generalized version of the bipolar…

Probability · Mathematics 2012-09-06 Marco Frittelli , Marco Maggis

This paper concerns the self-similarity of topological spaces, in the sense defined in math.DS/0411344. I show how to recognize self-similar spaces, or more precisely, universal solutions of self-similarity systems. Examples include the…

Dynamical Systems · Mathematics 2007-05-23 Tom Leinster

In this paper, as a common generalization of $SI_{2}$-continuous spaces and $s_{2}$-quasicontinuous posets, we introduce the concepts of $SI_{2}$-quasicontinuous spaces and $\mathcal{GD}$-convergence of nets for arbitrary topological spaces…

General Topology · Mathematics 2023-06-22 Xiaojun Ruan , Xiaoquan Xu

We present a comonadic approach to pretorsion theories on semiexact categories, i.e. categories equipped with a closed ideal of null morphisms that admits all kernels and all cokernels. We first prove that bihereditary pretorsion theories…

Category Theory · Mathematics 2026-01-19 Elena Caviglia , Zurab Janelidze , Luca Mesiti

The category of unital (unbounded) dg cocommutative coalgebras over a field of characteristic zero is provided with a structure of simplicial closed model category. This generalizes the model structure defined by Quillen in 1969 for…

Algebraic Geometry · Mathematics 2007-05-23 V. Hinich

We present a family of model structures on the category of multicomplexes. There is a cofibrantly generated model structure in which the weak equivalences are the morphisms inducing an isomorphism at a fixed stage of an associated spectral…

Algebraic Topology · Mathematics 2021-01-13 Xin Fu , Ai Guan , Muriel Livernet , Sarah Whitehouse

We consider the dual space of linear groups over Dynkinian and Euclidean algebras, i.e. finite dimensional algebras derived equivalent to the path algebra of Dynkin or Euclidean quiver. We prove that this space contains an open dense subset…

Representation Theory · Mathematics 2015-01-27 Viktor Bekkert , Yuriy Drozd , Vyacheslav Futorny

We establish necessary and sufficient conditions guaranteeing compactness of embeddings of fractional Sobolev spaces, Besov spaces, and Triebel-Lizorkin spaces, in the general context of quasi-metric-measure spaces. Although stated in the…

Functional Analysis · Mathematics 2024-06-27 Ryan Alvarado , Przemysław Górka , Artur Słabuszewski

We consider commutative Frobenius pseudomonoids in the bicategory of spans, and we show that they are in correspondence with 2-Segal cosymmetric sets. Such a structure can be interpreted as a coherent 2-dimensional topological quantum field…

Algebraic Topology · Mathematics 2026-01-01 Sophia E Marx , Rajan Amit Mehta

A semisimplicial set has face maps but not degeneracies. A basic fact, due to Rourke and Sanderson, is that a semisimplicial set satisfying the Kan condition can be given a simplicial structure. The present paper gives a combinatorial proof…

Algebraic Topology · Mathematics 2012-10-23 James E. McClure

Abundant second-order maximally conformally superintegrable Hamiltonian systems are re-examined, revealing their underlying natural Weyl structure and offering a clearer geometric context for the study of St\"ackel transformations (also…

Differential Geometry · Mathematics 2025-07-24 Andreas Vollmer

We first develop theories of differential rings of quasi-Siegel modular and quasi-Siegel Jacobi forms for genus two. Then we apply them to the Eynard-Orantin topological recursion of certain local Calabi-Yau threefolds equipped with branes,…

Algebraic Geometry · Mathematics 2023-04-12 Yongbin Ruan , Yingchun Zhang , Jie Zhou