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In this paper, we give a description of polynomial functors from (finitely generated free) groups to abelian groups in terms of non-linear Mackey functors generalizing those given in a paper of Baues-Dreckmann-Franjou-Pirashvili published…

Algebraic Topology · Mathematics 2012-09-12 Manfred Hartl , Teimuraz Pirashvili , Christine Vespa

Let $C_n$ denote a cyclic group of order $n$. In this paper we investigate modules and chain complexes over the constant integral Mackey functor $\underline{\mathbb{Z}}$ and perform some related homological calculations. Along the way we…

Algebraic Topology · Mathematics 2026-02-24 Daniel Dugger , Christy Hazel

Let $G$ be a groupoid acting on a set $X$ and let $R$ be a $G$-graded ring with graded local units. We study the main properties of the category $gr-(R,G,X)$ of $X$-graded $R$-modules and adjoint functors between categories of this kind. We…

Rings and Algebras · Mathematics 2025-12-09 Caio Antony , Ángel del Río

For a finite cyclic p-group G and a discrete valuation domain R of characteristic 0 with maximal ideal pR the R[G]-permutation modules are characterized in terms of the vanishing of first degree cohomology on all sub- groups (cf. Thm. A).…

Category Theory · Mathematics 2012-09-11 Blas Torrecillas , Thomas Weigel

Let $k$ be a commutative $\mathbb{Q}$-algebra. We study families of functors between categories of finitely generated $R$-modules which are defined for all commutative $k$-algebras $R$ simultaneously and are compatible with base changes.…

Category Theory · Mathematics 2020-01-29 Martin Brandenburg

We develop an obstruction theory for the existence and uniqueness of a solution to the gluing problem for a destriction functor and apply it to some well-known biset functors. The obstruction groups for this theory are reduced cohomology…

Representation Theory · Mathematics 2020-06-25 Olcay Coskun , Ergun Yalcin

We describe the multiplicative structures that arise on categories of equivariant modules over certain equivariant commutative ring spectra. Building on our previous work on N-infinity ring spectra, we construct categories of equivariant…

Algebraic Topology · Mathematics 2019-08-07 Andrew J. Blumberg , Michael A. Hill

The classification of simple biset functors is known, but the evaluation of a simple biset functor at a finite group G may be zero. We investigate various situations where this happens, as well as cases where this does not occur. We also…

Group Theory · Mathematics 2012-10-10 Serge Bouc , Radu Stancu , Jacques Thévenaz

We study several structure aspects of functor categories from a small additive category to a module category, in particular the category F(A,K) of functors from finitely generated free modules over a commutative ring A to vector spaces over…

Category Theory · Mathematics 2024-12-23 Aurélien Djament , Antoine Touzé

In [arXiv:1509.02937], the notion of a module tensor category was introduced as a braided monoidal central functor $F\colon \mathcal{V}\longrightarrow \mathcal{T}$ from a braided monoidal category $\mathcal{V}$ to a monoidal category…

Category Theory · Mathematics 2023-11-22 Sebastian Heinrich

In equivariant topology, Greenlees and May used Mackey functors to show that, rationally, the stable homotopy category of $G$-spectra over a finite group $G$ splits as a product of simpler module categories. We extend the algebraic part…

K-Theory and Homology · Mathematics 2024-05-30 Serge Bouc , Ivo Dell'Ambrogio , Rubén Martos

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

Let $G$ be a finite group. A $G$-Tambara functor can be defined as a product-preserving functor $\mathcal{P}_G \to \mathsf{Set}$ (satisfying one additional condition), where $\mathcal{P}_G$ is a category that is constructed in a…

Algebraic Topology · Mathematics 2024-09-23 Ben Spitz

In this paper we develop a theory of stability for $G$-categories (presheaf of categories on the orbit category of $G$), where $G$ is a finite group. We give a description of Mackey functors as $G$-commutative monoids exploit it to…

Algebraic Topology · Mathematics 2016-11-01 Denis Nardin

Modular functors are traditionally defined as systems of projective representations of mapping class groups of surfaces that are compatible with gluing. They can formally be described as modular algebras over central extensions of the…

Quantum Algebra · Mathematics 2025-10-27 Adrien Brochier , Lukas Woike

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 construct a map from the suspension $G$-spectrum $\Sigma_G^\infty M$ of a smooth compact $G$-manifold to the equivariant $A$-theory spectrum $A_G(M)$, and we show that its fiber is, on fixed points, a wedge of stable $h$-cobordism…

Algebraic Topology · Mathematics 2021-04-23 Cary Malkiewich , Mona Merling

Let G be a finite group. We systematically exploit general homological methods in order to reduce the computation of G-equivariant KK-theory to topological equivariant K-theory. The key observation is that the functor assigning to a…

Operator Algebras · Mathematics 2016-05-11 Ivo Dell'Ambrogio

We determine the structure of the fibered biset functor sending a finite group $G$ to the complex vector space of complex valued class functions of $G$. Previously, it is studied as a biset functor by Bouc and as a $\mathbb…

Representation Theory · Mathematics 2018-12-24 Mehmet Arslan , Olcay Coşkun

Let $G$ be a finite group acting on a small category $I$. We study functors $X \colon I \to \mathscr{C}$ equipped with families of compatible natural transformations that give a kind of generalized $G$-action on $X$. Such objects are called…

Algebraic Topology · Mathematics 2016-03-09 Emanuele Dotto , Kristian Moi