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We give an elementary exposition of some fundamental facts about fibered (or rather opfibered) categories, in terms of monads and 2-categories. The account avoids any mention of category-valued functors and pseudofunctors.

Category Theory · Mathematics 2013-12-06 Anders Kock

We generalise to a group homomorphism $\tau$ the $\chi$-graded categories of S\"{o}zer and Virelizier. These are categories in which both morphisms and objects have compatible degrees. We give a 'half-enriched' Yoneda lemma, a structure…

Category Theory · Mathematics 2026-02-06 Jonathan Davies

We study limits in 2-categories whose objects are categories with extra structure and whose morphisms are functors preserving the structure only up to a coherent comparison map, which may or may not be required to be invertible. This is…

Category Theory · Mathematics 2012-02-20 Stephen Lack , Michael Shulman

We reconcile the two different category-theoretic semantics of regular theories in predicate logic. A 2-category of `regular fibrations' is constructed, as well as a 2-category of `regular proarrow equipments', and it is shown that the two…

Category Theory · Mathematics 2015-03-02 Finn Lawler

In this work, we introduce a 2-categorical variant of Lurie's relative nerve functor. We prove that it defines a right Quillen equivalence which, upon passage to $\infty$-categorical localizations, corresponds to Lurie's scaled…

Algebraic Topology · Mathematics 2020-12-16 Fernando Abellán García , Tobias Dyckerhoff , Walker H. Stern

We establish and advocate for a novel branch of category theory, centered around strong dinatural transformations (herein known as "paranatural transformations"). Paranatural transformations generalize natural transformations to…

Category Theory · Mathematics 2023-07-19 Jacob Neumann

In this article, we develop a general technique for gluing subcategories of $\infty$-categories. We obtain categorical equivalences between simplicial sets associated to certain multisimplicial sets. Such equivalences can be used to…

Category Theory · Mathematics 2015-06-09 Yifeng Liu , Weizhe Zheng

Premonoidal categories and Freyd categories provide an encompassing framework for the semantics of call-by-value programming languages. Premonoidal categories are a weakening of monoidal categories in which the interchange law for the…

Logic in Computer Science · Computer Science 2023-12-27 Hugo Paquet , Philip Saville

A group-category is an additively semisimple category with a monoidal product structure in which the simple objects are invertible. For example in the category of representations of a group, 1-dimensional representations are the invertible…

Geometric Topology · Mathematics 2007-05-23 Frank Quinn

We study the notion of a "differential 2-rig", a category R with coproducts and a monoidal structure distributing over them, also equipped with an endofunctor D : R -> R that satisfies a categorified analogue of the Leibniz rule. This is…

Category Theory · Mathematics 2023-08-01 Fosco Loregian , Todd Trimble

The Grothendieck construction establishes an equivalence between fibrations, a.k.a. fibred categories, and indexed categories, and is one of the fundamental results of category theory. Cockett and Cruttwell introduced the notion of…

Category Theory · Mathematics 2025-07-30 Marcello Lanfranchi

Although it has been a well-known fact, for more than two decades, that category theory is needed for the study of topological orders, it is still a non-trivial challenge for students and working physicists to master the abstract language…

Strongly Correlated Electrons · Physics 2022-06-01 Liang Kong , Zhi-Hao Zhang

For a given category B we are interested in studying internal categorical structures in B. This work is the starting point, where we consider reflexive graphs and precategories (i.e., for the purpose of this note, a simplicial object…

Category Theory · Mathematics 2009-03-03 N. Martins-Ferreira

We present the notion of "cyclic double multicategory", as a structure in which to organise multivariable adjunctions and mates. The classic example of a 2-variable adjunction is the hom/tensor/cotensor trio of functors; we generalise this…

Category Theory · Mathematics 2012-08-24 Eugenia Cheng , Nick Gurski , Emily Riehl

We introduce a weakening of the notion of fusion 2-category given in arXiv:1812.11933. Then, we establish a number of properties of (multi)fusion 2-categories. Finally, we describe the fusion rule of the fusion 2-categories associated to…

Quantum Algebra · Mathematics 2022-11-09 Thibault D. Décoppet

This paper defines double fibrations (fibrations of double categories) and describes their key examples and properties. In particular, it shows how double fibrations relate to existing fibrational notions such as monoidal fibrations and…

Category Theory · Mathematics 2022-05-31 Geoffrey Cruttwell , Michael Lambert , Dorette Pronk , Martin Szyld

We introduce the basic elements of the theory of parametrized $\infty$-categories and functors between them. These notions are defined as suitable fibrations of $\infty$-categories and functors between them. We give as many examples as we…

Algebraic Topology · Mathematics 2016-08-15 Clark Barwick , Emanuele Dotto , Saul Glasman , Denis Nardin , Jay Shah

Categories, n-categories, double categories, and multicategories (among others) all have similar definitions as collections of cells with composition operations. We give an explicit description of the information required to define any…

Category Theory · Mathematics 2025-06-03 Brandon Shapiro

We develop a 2-dimensional version of accessibility and presentability compatible with the formalism of flat pseudofunctors. First we give prerequisites on the different notions of 2-dimensional colimits, filteredness and cofinality; in…

Category Theory · Mathematics 2025-08-05 Ivan Di Liberti , Axel Osmond

When a category is equipped with a 2-cell structure it becomes a sesquicategory but not necessarily a 2-category. It is widely accepted that the latter property is equivalent to the middle interchange law. However, little attention has been…

Category Theory · Mathematics 2024-06-13 Nelson Martins-Ferreira