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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 give a new criterion guaranteeing existence of model structures left-induced along a functor admitting both adjoints. This works under the hypothesis that the functor induces idempotent adjunctions at the homotopy category level. As an…

Category Theory · Mathematics 2022-10-25 Philip Hackney , Martina Rovelli

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

We demonstrate that companionships and conjunctions in double $\infty$-categories -- and more generally, in double Segal spaces -- extend to functors out of the free-living companionship and conjunction respectively. Specifically, we prove…

Category Theory · Mathematics 2025-04-09 Jaco Ruit

For every adjunction of stable $\infty$-categories -- or more generally, in any locally stable $(\infty,2)$-category -- we give a simple procedure for inverting the twist and cotwist functors associated to this adjunction. As a consequence,…

Category Theory · Mathematics 2026-05-15 Fernando Abellán , Jonte Gödicke

To a Legendrian knot, one can associate an $\mathcal{A}_{\infty}$ category, the augmentation category. An exact Lagrangian cobordism between two Legendrian knots gives a functor of the augmentation categories of the two knots. We study the…

Symplectic Geometry · Mathematics 2018-03-16 Yu Pan

We present a logical and algebraic description of right adjoint functors between generalized quasi-varieties, inspired by the work of McKenzie on category equivalence. This result is achieved by developing a correspondence between the…

Logic · Mathematics 2019-08-02 T. Moraschini

A Datalog program can be viewed as a syntactic specification of a functor from database instances over some schema to database instances over another schema. The same holds more generally for $\exists$Datalog. We establish large classes of…

Logic in Computer Science · Computer Science 2023-02-14 Balder ten Cate , Víctor Dalmau , Jakub Opršal

We study the bicategory of Landau-Ginzburg models, which has potentials as objects and matrix factorisations as 1-morphisms. Our main result is the existence of adjoints in this bicategory and a description of evaluation and coevaluation…

Algebraic Geometry · Mathematics 2015-12-10 Nils Carqueville , Daniel Murfet

We observe that an enriched right adjoint functor between model categories which preserves acyclic fibrations and fibrant objects is quite generically a right Quillen functor.

Algebraic Topology · Mathematics 2024-06-05 Victor Carmona

We describe a procedure for constructing morphisms in additive categories, combining Auslander's concept of a morphism determined by an object with the existence of flat covers. Also, we show how flat covers are turned into projective…

Category Theory · Mathematics 2014-06-26 Henning Krause

The structure of the category of matroids and strong maps is investigated: it has coproducts and equalizers, but not products or coequalizers; there are functors from the categories of graphs and vector spaces, the latter being faithful;…

Category Theory · Mathematics 2020-12-03 Chris Heunen , Vaia Patta

We define the notion of an indexed profunctor over a 2-category, and use it to develop an abstract theory of limits. The theory subsumes (conical) limits, weighted limits, ends and Kan extensions. Results include an abstract version of the…

Category Theory · Mathematics 2023-02-14 Sori Lee

We show that the restriction functor from oriented factor planar algebras to subfactor planar algebras admits a left adjoint, which we call the free oriented extension functor. We show that for any subfactor planar algebra realized as the…

Quantum Algebra · Mathematics 2018-10-09 Shamindra Kumar Ghosh , Corey Jones , B Madhav Reddy

We prove an adjoint functor theorem in the setting of categories enriched in a monoidal model category $\mathcal V$ admitting certain limits. When $\mathcal V$ is equipped with the trivial model structure this recaptures the enriched…

Category Theory · Mathematics 2022-12-13 John Bourke , Stephen Lack , Lukáš Vokřínek

For topological spaces $X$ and $Y$, a (not necessarily continuous) function $f:X \rightarrow Y$ naturally induces a functor from the category of closed subsets of $X$ (with morphisms given by inclusions) to the category of closed subsets of…

Category Theory · Mathematics 2014-08-13 Edward S. Letzter

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

This article is the last of the series of articles where we reprove the foundational ideas of abstract six-functor formalisms developed by Liu-Zheng. We prove the theorem of partial adjoints, which is a simplicial technique of encoding…

Algebraic Geometry · Mathematics 2025-02-03 Chirantan Chowdhury

We construct a compact closed category out of any symmetric monoidal category by freely adding adjoints to its objects. The morphisms of the completion are defined as string diagrams annotated by objects and morphisms from the original…

Category Theory · Mathematics 2022-01-24 Antonin Delpeuch

Two adjoint functors can be seen as generalisations of the two functions within a Galois connection. If instead the adjoints are not generalised from functions, but from relations, then analogously the object of study becomes a more general…

Category Theory · Mathematics 2025-02-10 Phillip-Jan van Zyl
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