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Building on work of Marta Bunge in the one-categorical case, we characterize when a given model category is Quillen equivalent to a presheaf category with the projective model structure. This involves introducing a notion of homotopy atoms,…

Algebraic Topology · Mathematics 2024-12-31 Boris Chorny , David White

Neocategories, semicategories, precategories are well-known generalizations of categories. But they all suppose that sources and targets of morphisms fulfilled identity conditions. Here we intend to suppress those conditions. In doing this…

Category Theory · Mathematics 2007-05-23 Freddy Bonnin

We show that non-pointed versions of the classical homological lemmas hold in regular protomodular categories equipped with a suitable posetal monocoreflective subcategory. Examples of such categories are all protomodular varieties of…

Category Theory · Mathematics 2025-07-03 Andrea Cappelletti , Andrea Montoli

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

Building on a specific formalization of analogical relationships of the form "A relates to B as C relates to D", we establish a connection between two important subfields of artificial intelligence, namely analogical reasoning and…

Machine Learning · Computer Science 2019-01-09 Mohsen Ahmadi Fahandar , Eyke Hüllermeier

Categorification is the process of finding category-theoretic analogs of set-theoretic concepts by replacing sets with categories, functions with functors, and equations between functions by natural isomorphisms between functors, which in…

Quantum Algebra · Mathematics 2014-11-18 John C. Baez , James Dolan

The primary goal of this paper is to abstract notions, results and constructions from the theory of categories to the broader setting of plots. Loosely speaking, a plot can be thought of as a non-associative non-unital category with a…

Category Theory · Mathematics 2016-04-06 Salvatore Tringali

The regular objects in various categories, such as maps, hypermaps or covering spaces, can be identified with the normal subgroups N of a given group \Gamma, with quotient group isomorphic to \Gamma/N. It is shown how to enumerate such…

Combinatorics · Mathematics 2013-09-25 Gareth A. Jones

Precategories generalize both the notions of strict $n$-category and sesquicategory: their definition is essentially the same as the one of strict $n$-categories, excepting that we do not require the various interchange laws to hold. Those…

Category Theory · Mathematics 2022-11-30 Simon Forest , Samuel Mimram

We axiomatically define (pre-)Hilbert categories. The axioms resemble those for monoidal Abelian categories with the addition of an involutive functor. We then prove embedding theorems: any locally small pre-Hilbert category whose monoidal…

Category Theory · Mathematics 2010-08-05 Chris Heunen

The notion of normal category was introduced by KSS Nambooripad in connection with the study of the structure of regular semigroups using cross connections\cite{nambooripad1994theory}. It is an abstraction of the category of principal left…

Category Theory · Mathematics 2021-05-05 C S Preenu , A R Rajan , K S Zeenath

We define the concept of a regular object with respect to another object in an arbitrary category. We present basic properties of regular objects and we study this concept in the special cases of abelian categories and locally finitely…

Category Theory · Mathematics 2007-05-23 S. S. Dăscălescu , C. Năstăsescu , A. Tudorache , L. Dăuş

This paper systematically develops a notion of regular sequences in the context of $R$-linear triangulated categories for a graded-commutative ring $R$. The notion has equivalent characterizations involving Koszul objects and local…

Commutative Algebra · Mathematics 2025-09-15 Antonia Kekkou , Janina C. Letz , Marc Stephan

We prove that a pointed category has kernels if and only if it is a lax algebra for the arrow 2-monad, and that this holds if and only if it is the d\'ecalage of a supercoherent structure. We will then interpret categories with kernels as…

Category Theory · Mathematics 2026-02-05 Martin Markl , Dominik Trnka

We study properties of a category after quotienting out a suitable chosen group of isomorphisms on each object. Coproducts in the original category are described in its quotient by our new weaker notion of a 'phased coproduct'. We examine…

Category Theory · Mathematics 2019-01-08 Sean Tull

We introduce a very general extension of the monomorphism category as studied by Ringel and Schmidmeier which in particular covers generalised species over locally bounded quivers. We prove that analogues of the kernel and cokernel functor…

Representation Theory · Mathematics 2021-09-09 Nan Gao , Julian Külshammer , Sondre Kvamme , Chrysostomos Psaroudakis

In this note, we propose a generalisation of G. Janelidze's notion of an ideally exact category beyond the Barr exact setting. We define an ideally regular category as a regular, Bourn protomodular category with finite coproducts in which…

Category Theory · Mathematics 2026-03-03 Sandra Mantovani , Mariano Messora

We define generalized bialgebras and Hopf algebras and on this basis we introduce quantum categories and quantum groupoids. The quantization of the category of linear (super)spaces is constructed. We establish a criterion for the classical…

q-alg · Mathematics 2008-02-03 Theodore Voronov

The attempt is to give a formal concpet of system, and with this provide a definition of category, that will also satisfy the definition of a system. An axiomatic base is given, for constructing the group of integers. In the process, we…

Category Theory · Mathematics 2015-11-26 Juan Pablo Ramirez

In this paper, we introduce the notion of a von Neumann category, as a generalization and categorification of von Neumann algebra. A von Neumann category is a premonoidal category with compatible dagger structure which embeds as a double…

Category Theory · Mathematics 2012-09-04 Richard Blute , Marc Comeau