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In this paper we prove two theorems which resemble the classical cohomological and homological Brown representability theorems. The main difference is that our results classify small contravariant functors from spaces to spaces up to weak…

Algebraic Topology · Mathematics 2013-12-05 Boris Chorny

We investigate 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 to a…

Rings and Algebras · Mathematics 2007-05-23 J. Gomez-Torrecillas , M. Zarouali Darkaoui

Let $J$ be a set of pairs consisting of good modules over an affine quantum algebra and invertible elements. The distribution of poles of the normalized R-matrices yields Khovanov-Lauda-Rouquier algebras $R^J$. We define a functor $F$ from…

Representation Theory · Mathematics 2021-03-29 Seok-Jin Kang , Masaki Kashiwara , Myungho Kim

Given a fixed tensor triangulated category S we consider triangulated categories T together with an S-enrichment which is compatible with the triangulated structure of T. It is shown that, in this setting, an enriched analogue of Brown…

Category Theory · Mathematics 2016-04-05 Johan Steen , Greg Stevenson

This is a survey paper, based on lectures given at the Workshop on "Structured ring spectra and their applications" which took place January 21-25, 2002, at the University of Glasgow. The term `Morita theory' is usually used for results…

Algebraic Topology · Mathematics 2020-01-13 Stefan Schwede

A relationship between coseparable corings and separable non-unital rings is established. In particular it is shown that an A-coring C has an associative A-balanced product. A Morita context is constructed for a coseparable coring with a…

Rings and Algebras · Mathematics 2007-05-23 Tomasz Brzezinski , Lars Kadison , Robert Wisbauer

Let $R$ be a commutative Noetherian ring and let $\G$ be the category of modules of G-dimension zero over $R$. We denote the associated stable category by $\pG$. We show that the functor category $\modpG$ is a Frobenius category and we…

Commutative Algebra · Mathematics 2007-05-23 Yuji Yoshino

Let $G$ be a finite group. In [HTW], Hambleton, Taylor and Williams have considered the question of comparing Mackey functors for $G$ and biset functors defined on subgroups of $G$ and bifree bisets as morphisms. This paper proposes a…

Group Theory · Mathematics 2013-03-28 Serge Bouc

We introduce the notion of a contramodule over a cocommutative coalgebra in a presentably symmetric monoidal $\infty$-category $\mathcal{C}$, and prove a symmetric monoidal $\infty$-categorical version of Positselski's comodule-contramodule…

Algebraic Topology · Mathematics 2025-11-11 Torgeir Aambø

We construct an exact tensor functor from the category $\mathcal{A}$ of finite-dimensional graded modules over the quiver Hecke algebra of type $A_\infty$ to the category $\mathscr C_{B^{(1)}_n}$ of finite-dimensional integrable modules…

Representation Theory · Mathematics 2017-10-19 Masaki Kashiwara , Myungho Kim , Se-jin Oh

For an endofunctor $F\colon\mathcal{C}\to\mathcal{C}$ on an ($\infty$-)category $\mathcal{C}$ we define the $\infty$-category $\operatorname{Cart}(\mathcal{C},F)$ of generalized Cartier modules as the lax equalizer of $F$ and the identity.…

Algebraic Geometry · Mathematics 2026-02-18 Klaus Mattis , Timo Weiß

We construct a fully faithful functor from the category of graphs to the category of fields. Using this functor, we resolve a longstanding open problem in computable model theory, by showing that for every nontrivial countable structure S,…

Logic · Mathematics 2015-10-27 Russell Miller , Bjorn Poonen , Hans Schoutens , Alexandra Shlapentokh

We introduce a theory of modules over a representation of a small category taking values in entwining structures over a semiperfect coalgebra. This takes forward the aim of developing categories of entwined modules to the same extent as…

Category Theory · Mathematics 2022-07-19 Abhishek Banerjee

We give a characterization, in terms of Galois infinite comatrix corings, of the corings that decompose as a direct sum of left comodules which are finitely generated as left modules. Then we show that the associated rational functor is…

Rings and Algebras · Mathematics 2009-02-16 L. El Kaoutit , J. Gómez-Torrecillas

A functor of sets $\mathbb X$ over the category of $K$-commutative algebras is said to be an affine functor if its functor of functions, $\mathbb A_{\mathbb X}$, is reflexive and $\mathbb X=\Spec \mathbb A_{\mathbb X}$. We prove that affine…

Algebraic Geometry · Mathematics 2012-05-08 J. Navarro , C. Sancho , P. Sancho

For coalgebras $C$ and $D$, Takeuchi proved that the category of linear functors from $\mathfrak{M}^C$ to $\mathfrak{M}^D$ preserving small coproducts is equivalent to the category of $C$-$D$-bicomodules, where $\mathfrak{M}^C$ for a…

Quantum Algebra · Mathematics 2025-10-10 Taiki Shibata , Kenichi Shimizu

In this paper we study a toy categorical version of Lusztig's induction and restriction functors for character sheaves, but in the abstract setting of multifusion categories. Let $\mathscr{C}$ be an indecomposable multifusion category and…

Quantum Algebra · Mathematics 2016-11-15 Tanmay Deshpande

We know that the model theory of modules leads to a way of obtaining definable categories of modules over a ring $R$ as the kernels of certain functors $(R\textbf{-Mod})^{\text{op}}\to\textbf{Ab}$ rather than of functors…

Representation Theory · Mathematics 2017-02-24 Samuel Dean

This paper addresses the problem of describing the structure of tensor C*-categories M with conjugates and irreducible tensor unit. No assumption on the existence of a braided symmetry or on amenability is made. Our assumptions are…

Operator Algebras · Mathematics 2010-11-10 Claudia Pinzari , John E. Roberts

In this paper we express certain multiplicities in modular representation-theoretic categories of type A in terms of affine p-Kazhdan-Lusztig polynomials. The representation-theoretic categories we deal with include the categories of…

Representation Theory · Mathematics 2017-01-04 Ben Elias , Ivan Losev