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We study the question when a category of ind-objects is abelian. Our answer allows a further generalization of the notion of weakly Tannakian categories introduced by the author. As an application we show that, under suitable conditions,…

Algebraic Geometry · Mathematics 2019-02-20 Daniel Schäppi

In this article, we construct a cofibrantly generated model structure on the category of spaces stratified over a fixed poset, and show that it is Quillen-equivalent to a category of diagrams of simplicial sets. Then, considering all those…

Algebraic Topology · Mathematics 2021-03-10 Sylvain Douteau

Let $G$ be a discrete group. We prove that the category of $G$-posets admits a model structure that is Quillen equivalent to the standard model structure on $G$-spaces. As is already true nonequivariantly, the three classes of maps defining…

Algebraic Topology · Mathematics 2018-05-18 J. P. May , Marc Stephan , Inna Zakharevich

We present an efficient and user-friendly method for constructing any cofibrantly generated model structure on the category of double categories whose trivial fibrations are the "canonical" ones: the double functors which are surjective on…

Algebraic Topology · Mathematics 2025-09-30 Lyne Moser , Maru Sarazola , Paula Verdugo

In this paper a notion of {\it generalized 2-vector space} is introduced which includes Kapranov and Voevodsky 2-vector spaces. Various kinds of generalized 2-vector spaces are considered and examples are given. The existence of non free…

Category Theory · Mathematics 2013-08-13 Josep Elgueta

Dimitri Ara's 2-quasi-categories, which are certain presheaves over Andr\'{e} Joyal's 2-cell category $\Theta_2$, are an example of a concrete model that realises the abstract notion of $(\infty,2)$-category. In this paper, we prove that…

Category Theory · Mathematics 2020-03-26 Yuki Maehara

Several situations are known when a holomorphic 2-form on a moduli space of sheaves over some base S is induced by a holomorphic 2-form on S. Moreover, the closedness of the 2-form on the base implies the closedness on the moduli space,…

Algebraic Geometry · Mathematics 2011-11-09 A. Kuznetsov , D. Markushevich

We show that the Rezk classification diagram of a relative category admitting a homotopical version of the two-sided calculus of fractions is a Segal space up to Reedy-fibrant replacement. This generalizes the result of Rezk and Bergner on…

Category Theory · Mathematics 2015-05-19 Zhen Lin Low , Aaron Mazel-Gee

We show that in the category of analytic sheaves on a complex analytic space, the full subcategory of quasi-coherent sheaves is an abelian subcategory.

Complex Variables · Mathematics 2024-07-17 Haohao Liu

A 2-Hilbert space is a category with structures and properties analogous to those of a Hilbert space. More precisely, we define a 2-Hilbert space to be an abelian category enriched over Hilb with a *-structure, conjugate-linear on the…

q-alg · Mathematics 2008-02-03 John C. Baez

The regular representation of an essentially finite 2-group $\mathbb{G}$ in the 2-category $\mathbf{2Vect}_k$ of (Kapranov and Voevodsky) 2-vector spaces is defined and cohomology invariants classifying it computed. It is next shown that…

Category Theory · Mathematics 2013-08-13 Josep Elgueta

In this paper, we study weakly unital dg categories as they were defined by Kontsevich and Soibelman [KS, Sect.4]. We construct a cofibrantly generated Quillen model structure on the category $\mathrm{Cat}_{\mathrm{dgwu}}(\Bbbk)$ of small…

K-Theory and Homology · Mathematics 2019-07-19 Piergiorgio Panero , Boris Shoikhet

Skeleton is a new notion designed for constructing space-filling curves of self-similar sets. It is shown in [Dai, Rao and Zhang, Space-filling curves of self-similar sets (II): Edge-to-trail substitution…

Dynamical Systems · Mathematics 2019-10-17 Hui Rao , Shu-Qin Zhang

Consider $(\mathbb{C}^*)^k$ acting on $\mathbb{C}^N$ satisfying certain 'quasi-symmetric' condition which produces a class of toric Calabi-Yau GIT quotient stacks. Using subcategories of $Coh([\mathbb{C}^N / (\mathbb{C}^*)^k])$ generated by…

Symplectic Geometry · Mathematics 2024-09-10 Jesse Huang , Peng Zhou

We construct a derived generalization of the pure spinor superfield formalism and prove that it exhibits an equivalence of dg-categories between multiplets for a supertranslation algebra and equivariant modules over its Chevalley-Eilenberg…

Mathematical Physics · Physics 2023-04-19 Chris Elliott , Fabian Hahner , Ingmar Saberi

We present a new notion of non-positively curved groups: the collection of discrete countable groups acting (AU-)acylindrically on finite products of $\delta$-hyperbolic spaces with general type factors. Inspired by the classical theory of…

Group Theory · Mathematics 2025-12-30 Sahana Balasubramanya , Talia Fernos

For a quasi-compact quasi-separated scheme X and an arbitrary scheme Y we show that the pullback construction implements an equivalence between the discrete category of morphisms Y --> X and the category of cocontinuous tensor functors…

Algebraic Geometry · Mathematics 2014-10-07 Martin Brandenburg , Alexandru Chirvasitu

In this paper, we give two elementary constructions of homogeneous quasi-morphisms defined on the group of Hamiltonian diffeomorphisms of certain closed connected symplectic manifolds (or on its universal cover). The first quasi-morphism,…

Symplectic Geometry · Mathematics 2007-06-13 Pierre Py

We define the quasi-compact Higgs $G^{\mathbb C}$-bundles over singular curves introduced in our previous paper for the Lie group SL($N$). The quasi-compact structure means that the automorphism groups of the bundles are reduced to the…

Mathematical Physics · Physics 2018-10-26 S. Kharchev , A. Levin , M. Olshanetsky , A. Zotov

We characterize the structure of 2-quasi-cyclic codes over a finite field F by the so-called Goursat Lemma. With the characterization, we exhibit a necessary and sufficient condition for a 2-quasi-cyclic code being a dihedral code. And we…

Information Theory · Computer Science 2022-01-06 Yun Fan , Yuchang Zhang