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In this article, we develop a notion of Quillen bifibration which combines the two notions of Grothendieck bifibration and of Quillen model structure. In particular, given a bifibration $p:\mathcal E\to\mathcal B$, we describe when a family…

Category Theory · Mathematics 2017-10-02 Pierre Cagne , Paul-André Melliès

We construct a category $\OrdFor$ as an arboreal extension of $\Delta_{\mathrm{epi}}\subseteq\Delta$, whose morphisms are ordered forests composed by grafting. We define a full functor $\pi\colon \OrdFor\to\Delta_{\mathrm{epi}}^{op}$…

Algebraic Topology · Mathematics 2026-04-03 Atabey Kaygun

Given an $\infty$-bicategory $\mathbb{D}$ with underlying $\infty$-category $\mathcal{D}$, we construct a Cartesian fibration $\operatorname{Tw}(\mathbb{D})\to \mathcal{D} \times \mathcal{D}^{\operatorname{op}}$, which we call the enhanced…

Category Theory · Mathematics 2020-09-28 Fernando Abellán García , Walker H. Stern

In this thesis, we introduce Cartesian double categories, motivated by the work of Carboni, Kelly, Walters, and Wood on Cartesian bicategories. Moving from bicategories to the slightly more generalized notion of double categories allows us…

Category Theory · Mathematics 2018-09-20 Evangelia Aleiferi

We develop a categorical framework for reasoning about abstract properties of differentiation, based on the theory of fibrations. Our work encompasses the first-order fragments of several existing categorical structures for differentiation,…

Category Theory · Mathematics 2024-09-10 Matteo Capucci , Geoffrey S. H. Cruttwell , Neil Ghani , Fabio Zanasi

Let $\mathcal{C}$ be a finitely bicomplete category and $\mathcal{W}$ a subcategory. We prove that the existence of a model structure on $\mathcal{C}$ with $\mathcal{W}$ as subcategory of weak equivalence is not first order expressible.…

Category Theory · Mathematics 2021-02-25 Jean-Marie Droz , Inna Zakharevich

Categories of W*-bimodules are shown in an explicit and algebraic way to constitute an involutive W*-bicategory.

Operator Algebras · Mathematics 2017-06-14 Yusuke Sawada , Shigeru Yamagami

Given any category $\mathcal{C}$ with pullbacks and a terminal object, we show that the data consisting of the objects of $\mathcal{C}$, the spans of $\mathcal{C}$, and the isomorphism classes of spans of spans of $\mathcal{C}$, forms a…

Category Theory · Mathematics 2015-01-06 Franciscus Rebro

We construct combinatorial model category structures on the categories of (marked) categories and (marked) pre-additive categories, and we characterize (marked) additive categories as fibrant objects in a Bousfield localization of…

Algebraic Topology · Mathematics 2021-05-28 Ulrich Bunke , Alexander Engel , Daniel Kasprowski , Christoph Winges

Polynomial functors are a categorical generalization of the usual notion of polynomial, which has found many applications in higher categories and type theory: those are generated by polynomials consisting a set of monomials built from sets…

Logic in Computer Science · Computer Science 2021-12-30 Eric Finster , Samuel Mimram , Maxime Lucas , Thomas Seiller

We define biprops as a generalization of coloured props and of symmetric weak multicategories. These are bicategories whose objects form a free monoid. They are equipped with some structure resembling a symmetric strict tensor product. We…

Category Theory · Mathematics 2026-04-21 Volodymyr Lyubashenko

We give an elementary construction of the dual fibration of a fibration. It does not use the non-elementary notion of (pseudo-) functor into the category of categories.

Category Theory · Mathematics 2015-01-09 Anders Kock

A convenient bicategory of topological stacks is constructed which is both complete and Cartesian closed. This bicategory, called the bicategory of compactly generated stacks, is the analogue of classical topological stacks, but for a…

Algebraic Topology · Mathematics 2016-10-18 David Carchedi

The goal of this paper is to prove an equivalence between the $(\infty,2)$-category of cartesian factorization systems of $\infty$-categories and that of pointed cartesian fibrations of $\infty$-categories. This generalizes a similar result…

Algebraic Topology · Mathematics 2019-11-27 Edoardo Lanari

We develop bicategory theory in univalent foundations. Guided by the notion of univalence for (1-)categories studied by Ahrens, Kapulkin, and Shulman, we define and study univalent bicategories. To construct examples of univalent…

Category Theory · Mathematics 2022-08-16 Benedikt Ahrens , Dan Frumin , Marco Maggesi , Niccolò Veltri , Niels van der Weide

Algebra objects in $\infty$-categories of spans admit a description in terms of $2$-Segal objects. We introduce a notion of span between $2$-Segal objects and extend this correspondence to an equivalence of $\infty$-categories.…

Algebraic Topology · Mathematics 2025-10-30 Jonte Gödicke

We provide bicategorical analogs of several aspects of the notion of geometry in the sense of the theory of spectrum. We first introduce a notion of local right biadjoint, and prove it to be equivalent to a notion of bistable pseudofunctor,…

Category Theory · Mathematics 2021-11-19 Axel Osmond

Constructing and manipulating homotopy types from categorical input data has been an important theme in algebraic topology for decades. Every category gives rise to a `classifying space', the geometric realization of the nerve. Up to weak…

Algebraic Topology · Mathematics 2019-10-30 Stefan Schwede

Recent work in set theory indicates that there are many different notions of 'set', each captured by a different collection of axioms, as proposed by J. Hamkins in [Ham11]. In this paper we strive to give one class theory that allows for a…

Logic · Mathematics 2022-06-10 Alec Rhea

In this paper we start by pointing out that Yoneda's notion of a regular span $S \colon \mathcal{X} \to \mathcal{A} \times \mathcal{B}$ can be interpreted as a special kind of morphism, that we call fiberwise opfibration, in the 2-category…

Category Theory · Mathematics 2018-06-08 Alan S. Cigoli , Sandra Mantovani , Giuseppe Metere , Enrico M. Vitale