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We initiate the study of the cohomology of (strict polynomial) bifunctors by introducing the foundational formalism, establishing numerous properties in analogy with the cohomology of functors, and providing computational techniques. Since…

K-Theory and Homology · Mathematics 2008-05-19 Vincent Franjou , Eric M. Friedlander

For a Whitney stratification S of a space X (or more generally a topological stratification in the sense of Goresky and MacPherson) we introduce the notion of an S-constructible stack of categories on X. The motivating example is the stack…

Algebraic Topology · Mathematics 2014-01-14 David Treumann

We introduce a new categorical framework for studying derived functors, and in particular for comparing composites of left and right derived functors. Our central observation is that model categories are the objects of a double category…

Category Theory · Mathematics 2011-03-01 Michael Shulman

We associate to a 2-vector bundle over an essentially finite groupoid a 2-vector space of parallel sections, or, in representation theoretic terms, of higher invariants, which can be described as homotopy fixed points. Our main result is…

Category Theory · Mathematics 2023-07-03 Christoph Schweigert , Lukas Woike

The aim of this paper is to extend the definition of motivic homotopy theory from schemes to a large class of algebraic stacks and establish a six functor formalism. The class of algebraic stacks that we consider includes many interesting…

Algebraic Geometry · Mathematics 2024-05-29 Chirantan Chowdhury

We develop new techniques for constructing model structures from a given class of cofibrations, together with a class of fibrant objects and a choice of weak equivalences between them. As a special case, we obtain a more flexible version of…

Algebraic Topology · Mathematics 2026-01-23 Léonard Guetta , Lyne Moser , Maru Sarazola , Paula Verdugo

For a weak 2-group, we construct a bicategory of flat 2-group bundles over differentiable stacks as a localization of a functor bicategory. This description is amenable to explicit geometric constructions. For example, we show that flat…

Algebraic Topology · Mathematics 2025-10-16 Daniel Berwick-Evans , Emily Cliff , Laura Murray , Apurva Nakade , Emma Phillips

We treat the problem of lifting bicategories into double categories through categories of vertical morphisms. We consider structures on decorated 2-categories allowing us to formally implement arguments of sliding certain squares along…

Category Theory · Mathematics 2024-06-24 Juan Orendain , Ruben Maldonado

There is a lot of redundancy in the usual definition of adjoint functors. We define and prove the core of what is required. First we do this in the hom-enriched context. Then we do it in the cocompletion of a bicategory with respect to…

Category Theory · Mathematics 2012-01-04 Ross Street

This paper is part of a series of articles in which we reproduce the statements regarding the abstract six-functor formalism developed by Liu-Zheng. In this paper, we prove a theorem, which is an $\infty$-categorical version for defining…

Algebraic Geometry · Mathematics 2025-01-30 Chirantan Chowdhury

The postulates of comprehension and extensionality in set theory are based on an inversion principle connecting set-theoretic abstraction and the property of having a member. An exactly analogous inversion principle connects functional…

Category Theory · Mathematics 2007-05-23 K. Dosen

The purpose of this article is threefold: Firstly, we propose some enhancements to the existing definition of 6-functor formalisms. Secondly, we systematically study the category of kernels, which is a certain 2-category attached to every…

Category Theory · Mathematics 2024-10-18 Claudius Heyer , Lucas Mann

Fixpoint operators are tools to reason on recursive programs and data types obtained by induction (e.g. lists, trees) or coinduction (e.g. streams). They were given a categorical treatment with the notion of categories with fixpoints. A…

Logic in Computer Science · Computer Science 2023-06-07 Zeinab Galal

Given a quotient vector bundle $\mathcal A$ over $X$ with kernel map $\kappa: X\to\mathrm{Max}\,A$ we study the codual bundle with fiber at each point $x\in X$ isomorphic to the dual of $\kappa(x)$. Applying the adjunction between quotient…

Category Theory · Mathematics 2018-08-06 João Paulo Santos

To a Lie groupoid over a compact base, the associated group of bisection is an (infinite-dimensional) Lie group. Moreover, under certain circumstances one can reconstruct the Lie groupoid from its Lie group of bisections. In the present…

Category Theory · Mathematics 2019-02-20 Alexander Schmeding , Christoph Wockel

We develop a full 6-functor formalism for $p$-torsion \'etale sheaves in rigid-analytic geometry. More concretely, we use the recently developed condensed mathematics by Clausen--Scholze to associate to every small v-stack (e.g.…

Algebraic Geometry · Mathematics 2022-06-07 Lucas Mann

We create a framework for odd Khovanov homology in the spirit of Bar-Natan's construction for the ordinary Khovanov homology. Namely, we express the cube of resolutions of a link diagram as a diagram in a certain 2-category of chronological…

Geometric Topology · Mathematics 2015-02-11 Krzysztof K. Putyra

We introduce and study the Scott adjunction, relating accessible categories with directed colimits to topoi. Our focus is twofold, we study both its applications to formal model theory and its geometric interpretation. From the geometric…

Category Theory · Mathematics 2020-09-17 Ivan Di Liberti

It is shown that a strong system of vector fields on a fiber bundle in the sense of [Modugno, M. Systems of connections and invariant lagrangians. In: Differential geometric methods in theoretical physics, Proc. 15th Int. Conf., DGM,…

Differential Geometry · Mathematics 2016-09-06 Peter W. Michor

We arrange morphisms and comorphisms of sites as the horizontal and vertical cells of a double category of sites; using the formalism of extensions and restrictions of presheaves, we explains how one can define a sheafification double…

Category Theory · Mathematics 2025-05-14 Olivia Caramello , Axel Osmond