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We develop the theory of exact completions of regular $\infty$-categories, and show that the $\infty$-categorical exact completion (resp. hypercompletion) of an abelian category recovers the connective half of its bounded (resp. unbounded)…

Category Theory · Mathematics 2023-10-20 Germán Stefanich

The purpose of this short and elementary note is to identify some classes of exact categories introduced in L. Previdi's thesis. Among other things we show: (1) An exact category is partially abelian exact if and only if it is abelian. (2)…

Category Theory · Mathematics 2021-10-05 Theo Buehler

An algebraic category $\mathcal{C}$ is called balanced if the cotriple cohomology of any object of $\mathcal{C}$ vanishes in positive dimensions on injective coefficient modules. Important examples of balanced and of non-balanced categories…

Algebraic Topology · Mathematics 2016-09-07 Simona Paoli

We study when the stable category of an abelian category modulo a full additive subcategory is balanced and, in case the subcategory is functorially finite, we study a weak version of balance. Precise necessary and sufficient conditions are…

Category Theory · Mathematics 2010-10-05 Pedro Nicolas , Manuel Saorin

We introduce the concept of a pseudo-cluster tilting subcategory from the viewpoint of the fact that the quotient of an exact category by a cluster tilting subcategory is an abelian category. We prove that the quotients in the case of…

Representation Theory · Mathematics 2023-03-14 Jie Xu , Yuefei Zheng

We introduce $n$-abelian and $n$-exact categories, these are analogs of abelian and exact categories from the point of view of higher homological algebra. We show that $n$-cluster-tilting subcategories of abelian (resp. exact) categories…

Category Theory · Mathematics 2017-06-15 Gustavo Jasso

We construct examples of (effective) closed orbifolds which are covered by manifolds, but not finitely so.

Geometric Topology · Mathematics 2024-04-23 Christian Lange

We construct a finitely generated group that does not satisfy the generalized Burghelea conjecture.

K-Theory and Homology · Mathematics 2019-05-03 A. Dranishnikov , M. Hull

We construct a finitely generated 2-dimensional group that acts properly on a locally finite CAT(0) cube complex but does not act properly on a finite dimensional CAT(0) cube complex.

Group Theory · Mathematics 2021-09-21 Kasia Jankiewicz , Daniel T. Wise

We introduce the notions of proto-complete, complete, complete* and strong-complete objects in pointed categories. We show under mild conditions on a pointed exact protomodular category that every proto-complete (respectively complete)…

Category Theory · Mathematics 2021-02-22 James Richard Andrew Gray

We call a finitely complete category algebraically coherent when the change-of-base functors of its fibration of points are coherent, which means that they preserve finite limits and jointly strongly epimorphic pairs of arrows. We give…

Category Theory · Mathematics 2015-12-10 Alan S. Cigoli , James R. A. Gray , Tim Van der Linden

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

We describe a perfect group whose localization is not perfect.

Group Theory · Mathematics 2007-05-23 Bernard Badzioch , Mark Feshbach

In this paper, we discuss certain circumstances in which the category of tame functors inherits an abelian category structure with minimal resolutions and a model category structure with minimal cofibrant replacements. We also present a…

Algebraic Topology · Mathematics 2024-03-26 Wojciech Chachólski , Barbara Giunti , Claudia Landi , Francesca Tombari

To a big n-tilting object in a complete, cocomplete abelian category A with an injective cogenerator we assign a big n-cotilting object in a complete, cocomplete abelian category B with a projective generator, and vice versa. Then we…

Category Theory · Mathematics 2021-01-13 Leonid Positselski , Jan Stovicek

For a triangulated category T, if C is a cluster-tilting subcategory of T, then the quotient category T\C is an abelian category. Under certain conditions, the converse also holds. This is an very important result of cluster-tilting theory,…

Representation Theory · Mathematics 2020-03-16 Yu Liu , Panyue Zhou

This is the second paper in a series on representations over diagrams of abelian categories. We show that, under certain conditions, a compatible family of abelian model categories indexed by a skeletal small category can be amalgamated…

Category Theory · Mathematics 2025-06-23 Zhenxing Di , Liping Li , Li Liang , Nina Yu

We prove that some subquotient categories of exact categories are abelian. This generalizes a result by Koenig-Zhu in the case of (algebraic) triangulated categories. As a particular case, if an exact category B with enough projectives and…

Representation Theory · Mathematics 2015-09-04 Laurent Demonet , Yu Liu

We prove a constructive existence theorem for abelian envelopes of non-abelian monoidal categories. This establishes a new tool for the construction of tensor categories. As an example we obtain new proofs for the existence of several…

Category Theory · Mathematics 2023-06-22 Kevin Coulembier

We address a problem posed in [1] by demonstrating through an example that, in the absence of separability, the property of sequential cone compactness does not generally imply cone compactness.

Functional Analysis · Mathematics 2025-01-10 Marius Durea , Elena-Andreea Florea