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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

Let $R$ be an associative ring with unit. Given an $R$-module $M$, we can associate the following covariant functor from the category of $R$-algebras to the category of abelian groups: $S\mapsto M\otimes_R S$. With the corresponding notion…

Category Theory · Mathematics 2018-11-29 Adrián Gordillo-Merino , José Navarro , Pedro Sancho

In this paper, I give several characterizations of {\em rational biset functors over $p$-groups}, which are independent of the knowledge of genetic bases for $p$-groups. I also introduce a construction of new biset functors from known ones,…

Group Theory · Mathematics 2007-05-23 Serge Bouc

Let G be a finite group and let k be a field. Our purpose is to investigate the simple modules for the double Burnside ring kB(G,G). It turns out that they are evaluations at G of simple biset functors. For a fixed finite group H, we…

Group Theory · Mathematics 2012-03-02 Serge Bouc , Radu Stancu , Jacques Thévenaz

Given a not necessarily semisimple modular tensor category C, we use the corresponding 3d TFT defined in [arXiv:1912.02063] to explicitly describe a modular functor as a symmetric monoidal 2-functor from a 2-category of oriented bordisms to…

Quantum Algebra · Mathematics 2024-05-29 Aaron Hofer , Ingo Runkel

For a Green biset functor $A$, we define the commutant and the center of $A$ and we study some of their properties and their relationship. This leads in particular to the main application of these constructions: the possibility of splitting…

Group Theory · Mathematics 2022-01-06 Serge Bouc , Nadia Romero

We classify various types of graded extensions of a finite braided tensor category $\cal B$ in terms of its $2$-categorical Picard groups. In particular, we prove that braided extensions of $\cal B$ by a finite group $A$ correspond to…

Quantum Algebra · Mathematics 2021-05-28 Alexei Davydov , Dmitri Nikshych

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

We establish a correspondence between modules and spans of algebras within a general monoidal 2-category $\mathfrak{C}$. Specifically, for an algebra $A$ in $\mathfrak{C}$, we construct a normalized lax 3-functor from the 2-category of…

Category Theory · Mathematics 2025-12-03 Hao Xu

We consider the 3-category $2\mathfrak{C}at$ whose objects are 2-categories, 1-morphisms are lax functors, 2-morphisms are lax transformations and 3-morphisms are modifications. The aim is to show that it carries interesting…

Representation Theory · Mathematics 2025-08-11 Fei Xu , Maoyin Zhang

We prove that, for any fields $k$ and $\mathbb{F}$ of characteristic $0$ and any finite group $T$, the category of modules over the shifted Green biset functor $(kR_{\mathbb{F}})_T$ is semisimple.

Group Theory · Mathematics 2022-01-07 Serge Bouc , Nadia Romero

For a category B with finite products, we first characterize pseudofunctors from B to Cat whose corresponding opfibration is cartesian monoidal. Among those, we then characterize the ones which extend to pseudofunctors from internal groups…

Category Theory · Mathematics 2022-06-03 Alan S. Cigoli , Sandra Mantovani , Giuseppe Metere

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

We study finitary 2-categories associated to dual projection functors for finite dimensional associative algebras. In the case of path algebras of admissible tree quivers (which includes all Dynkin quivers of type A) we show that the monoid…

Representation Theory · Mathematics 2017-05-10 Anna-Louise Grensing , Volodymyr Mazorchuk

We outline the theory of reflections for prederivators, derivators and stable derivators. In order to parallel the classical theory valid for categories, we outline how reflections can be equivalently described as categories of fractions,…

Category Theory · Mathematics 2018-02-23 Fosco Loregian

We classify the module categories over the double (possibly twisted) of a finite group.

Quantum Algebra · Mathematics 2007-05-23 Victor Ostrik

In this article we extend evaluations of the Kauffman bracket on regular isotopy classes of knots and links to a variety of functors defined on the category of framed tangles. We show that many such functors exist, and that they correspond…

Geometric Topology · Mathematics 2007-05-23 John Armstrong

For a finite dimensional algebra $A$, we prove that the bounded homotopy category of projective $A$-modules and the bounded derived category of $A$-modules are dual to each other via certain categories of locally-finite cohomological…

Rings and Algebras · Mathematics 2018-10-09 Xiao-Wu Chen

We provide a multiplicative classification of polynomial endofunctors on spectra in terms of their Mackey functors of cross--effects. More precisely, we prove that various categories of multivariable excisive functors from spectra to…

Algebraic Topology · Mathematics 2026-04-03 Tobias Barthel , Kaif Hilman , Nikolay Konovalov

The analogy between Yetter's deformation theory form (lax) monoidal functors and Gerstenahaber's deformation theory for associative algebras is solidified by shown that under reasonable conditions the category of functors with an action of…

Category Theory · Mathematics 2007-05-23 David N. Yetter