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For a small category A, we prove that the homotopy colimit functor from the category of simplicial diagrams on A to the category of simplicial sets over the nerve of A establishes a left Quillen equivalence between the projective (or Reedy)…

Algebraic Topology · Mathematics 2016-02-04 Gijs Heuts , Ieke Moerdijk

The contributions of this paper are twofold. Within the framework of Grothendieck's fibrational category theory, we present a web of fundamental 2-adjunctions surrounding the formation of the category of all small diagrams in a given…

Category Theory · Mathematics 2021-03-09 George Peschke , Walter Tholen

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 show that any functor between $\infty$-categories can be straightened. More precisely, we show that for any $\infty$-category $\mathcal{C}$, there is an equivalence between the $\infty$-category $(\mathrm{Cat}_{\infty})_{/\mathcal{C}}$…

Category Theory · Mathematics 2025-10-14 Thomas Blom

For a diagram of simplicial combinatorial model categories, we show that the associated lax limit, endowed with the projective model structure, is a presentation of the lax limit of the underlying $\infty$-categories. Our approach can also…

Algebraic Topology · Mathematics 2019-02-14 Yonatan Harpaz

In this paper, we justify and make precise an elementary approach that establishes the existence of (co)limits in $\mathbf{Cat}$. This approach, while conceptually evident, has not been made fully explicit or systematically described in the…

Category Theory · Mathematics 2026-04-16 Varinderjit Mann

In this work, we conclude our study of fibred $\infty$-bicategories by providing a Grothendieck construction in this setting. Given a scaled simplicial set $S$ (which need not be fibrant) we construct a 2-categorical version of Lurie's…

Algebraic Topology · Mathematics 2023-04-14 Fernando Abellán , Walker H. Stern

We prove a refinement of Quillen's Theorem A, providing necessary and sufficient conditions for a functor to be cofinal with respect to diagrams valued in a fixed $\infty$-category. We deduce this from a general duality phenomenon for…

Category Theory · Mathematics 2025-12-17 Shai Keidar , Lior Yanovski

We provide a short and reasonably self-contained proof of Lurie's straightening equivalence, relating cartesian fibrations over a given $\infty$-category $S$ with contravariant functors from $S$ to the $\infty$-category of small…

Category Theory · Mathematics 2024-12-23 Fabian Hebestreit , Gijs Heuts , Jaco Ruit

In this technical note, we proffer a very explicit construction of the "dual cocartesian fibration" $p^{\vee}$ of a cartesian fibration $p$, and we show they are classified by the same functor to $\mathbf{Cat}_{\infty}$.

Category Theory · Mathematics 2014-09-09 Clark Barwick , Saul Glasman , Denis Nardin

For a small simplicial category A, we prove that the homotopy colimit functor from the category of simplicial diagrams on A to the category of simplicial sets over the homotopy-coherent nerve of A provides a left Quillen equivalence between…

Algebraic Topology · Mathematics 2016-02-04 Gijs Heuts , Ieke Moerdijk

Given a symplectic manifold M, we consider a category with objects finite ordered families of Lagrangian submanifolds of M (subject to certain additional constraints) and with morphisms Lagrangian cobordisms relating them. We construct a…

Symplectic Geometry · Mathematics 2018-08-28 Paul Biran , Octav Cornea

In this article we introduce four variance flavours of cartesian 2-fibrations of $\infty$-bicategories with $\infty$-bicategorical fibres, in the framework of scaled simplicial sets. Given a map $p\colon \mathcal{E} \rightarrow\mathcal{B}$…

Category Theory · Mathematics 2025-01-01 Andrea Gagna , Yonatan Harpaz , Edoardo Lanari

The notion of geometric nerve of a 2-category (Street, \cite{refstreet}) provides a full and faithful functor if regarded as defined on the category of 2-categories and lax 2-functors. Furthermore, lax 2-natural transformations between lax…

Category Theory · Mathematics 2007-05-23 M. Bullejos , E. Faro , V. Blanco

Latent fibrations are an adaptation, appropriate for categories of partial maps (as presented by restriction categories), of the usual notion of fibration. The paper initiates the development of the basic theory of latent fibrations and…

Category Theory · Mathematics 2020-10-30 Robin Cockett , Geoff Cruttwell , Jonathan Gallagher , Dorette Pronk

We study fppf descent for enhanced derived categories. We revisit the work of [HS] and [TV08] in a lax context. More precisely, we construct a Cartesian and coCartesian fibration ${}^{\mathrm{op}}\mathscr D^+_S\rightarrow…

Algebraic Geometry · Mathematics 2018-02-21 Ajneet Dhillon , Pál Zsámboki

Riehl and Verity have established that for a quasi-category $A$ that admits limits, and a homotopy coherent monad on $A$ which does not preserve limits, the Eilenberg-Moore object still admits limits; this can be interpreted as a…

Category Theory · Mathematics 2025-05-22 Joanna Ko

We introduce notions of lax semiadditive and lax additive $(\infty,2)$-categories, categorifying the classical notions of semiadditive and additive 1-categories. To establish a well-behaved axiomatic framework, we develop a calculus of lax…

Category Theory · Mathematics 2025-11-18 Merlin Christ , Tobias Dyckerhoff , Tashi Walde

We show that the category of $n$-excisive functors from the $\infty$-category of spectra to a target stable $\infty$-category $\mathbf{E}$ is equivalent to the category of $\mathbf{E}$-valued Mackey functors on an indexing category built…

Algebraic Topology · Mathematics 2018-10-05 Saul Glasman

Cartesian fibrations were originally defined by Lurie in the context of quasi-categories and are commonly used in $(\infty,1)$-category theory to study presheaves valued in $(\infty,1)$-categories. In this work we define and study…

Category Theory · Mathematics 2021-02-12 Nima Rasekh