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In the context of infinity categories, we rethink the notion of derived functor in terms of correspondences. This is especially convenient for the description of a passage from an adjoint pair (F,G) of functors to a derived adjoint pair…

Category Theory · Mathematics 2020-03-25 V. Hinich

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

We construct an explicit combinatorial model of the functor which adds right adjoints to the morphisms of an $\infty$-category, and we speculate on possible extensions to higher dimensions.

Category Theory · Mathematics 2025-10-08 Lorenzo Riva , Martina Rovelli

There are many contexts in algebraic geometry, algebraic topology, and homological algebra where one encounters a functor that has both a left and right adjoint, with the right adjoint being isomorphic to a shift of the left adjoint…

Algebraic Topology · Mathematics 2007-05-23 H. Fausk , P. Hu , J. P. May

Everyone knows that if you have a bivariant homology theory satisfying a base change formula, you get an representation of a category of correspondences. For theories in which the covariant and contravariant transfer maps are in mutual…

Category Theory · Mathematics 2022-12-21 Andrew W. Macpherson

We construct an abelian category C and exact functors in C which on the Grothendieck group descend to the action of a simply-laced quantum group in its adjoint representation. The braid group action in the adjoint representation lifts to an…

Quantum Algebra · Mathematics 2007-05-23 Ruth Stella Huerfano , Mikhail Khovanov

The study of complex systems through the lens of category theory consistently proves to be a powerful approach. We propose that cognition deserves the same category-theoretic treatment. We show that by considering a highly-compact cognitive…

Neurons and Cognition · Quantitative Biology 2021-08-04 Sophie Alyx Taylor , Son Cao Tran , Dan V. Nicolau

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

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 investigate adjoint and Frobenius pairs between categories of comodules over rather general corings. We particularize to the case of the adjoint pair of functors associated to a morphism of corings over different base rings, which leads…

Rings and Algebras · Mathematics 2007-05-23 M. Zarouali-Darkaoui

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

We study selfadjoint functors acting on categories of finite dimensional modules over finite dimensional algebras with an emphasis on functors satisfying some polynomial relations. Selfadjoint functors satisfying several easy relations, in…

Representation Theory · Mathematics 2011-09-08 Troels Agerholm , Volodymyr Mazorchuk

For our purposes, two functors {\Lambda} and {\Gamma} are said to be respectively left and right adjoints of each other if for any digraphs G and H, there exists a homomorphism of {\Lambda}(G) to H if and only if there exists a homomorphism…

Combinatorics · Mathematics 2015-06-04 Jan Foniok , Claude Tardif

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

Perhaps the most important contribution of gauge theory to general mathematics is to point out the importance of association functors. Emphasizing category theory we characterize association functors by two of their natural properties and…

Differential Geometry · Mathematics 2022-07-29 Gustavo Amilcar Saldaña Moncada , Gregor Weingart

We formalize the concept of a centralizer-respecting homomorphism, surjective homomorphisms which are equivariant with respect to taking the centralizer of a subgroup. There is a functor from the category of centralizer-respecting…

Group Theory · Mathematics 2026-05-15 William Cocke , Mark L. Lewis , Ryan McCulloch

This note aims to introduce a left adjoint functor to the functor which assigns a heap to a group. The adjunction is monadic. It is explained how one can decompose a free group functor through the previously introduced adjoint and employ it…

Group Theory · Mathematics 2021-01-19 Bernard Rybołowicz

Category theory offers a mathematical foundation for knowledge representation and database systems. Popular existing approaches model a database instance as a functor into the category of sets and functions, or as a 2-functor into the…

Category Theory · Mathematics 2025-09-26 Michael Lambert , Evan Patterson

This paper discusses some issues arising from the category $\mathfrak{H}$ of hypergraphs, the category $\mathfrak{M}$ of (undirected) multigraphs, and the topos $\mathfrak{Q}$ of quivers. First, the natural inclusion of $\mathfrak{M}$ into…

Combinatorics · Mathematics 2018-05-24 Will Grilliette

This second part comes to the construction of the spectrum associated to a situation of multi-adjunction. Exploiting a geometric understanding of its multi-versal property, the spectrum of an object is obtained as the spaces of local units…

Category Theory · Mathematics 2021-04-07 Axel Osmond