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We compute Mackey functor-valued Tor over certain free incomplete Tambara functors, generalizing the computation of Tor over a polynomial ring on one generator. In contrast with the classical situation where the resulting Tor groups vanish…

Algebraic Topology · Mathematics 2025-07-15 David Mehrle , J. D. Quigley , Michael Stahlhauer

In the previous article 'A Mackey-functor theoretic interpretation of biset functors', we have constructed the 2-category $\mathbb{S}$ of finite sets with variable finite group actions, in which bicoproducts and bipullbacks exist. As shown…

Category Theory · Mathematics 2015-12-08 Hiroyuki Nakaoka

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

For a finite group $G$, a Tambara functor on $G$ is regarded as a $G$-bivariant analog of a commutative ring. In this article, we consider a $G$-bivariant analog of the ideal theory for Tambara functors.

Category Theory · Mathematics 2011-03-22 Hiroyuki Nakaoka

The category of strict polynomial functors inherits an internal tensor product from the category of divided powers. To investigate this monoidal structure, we consider the category of representations of the symmetric group which admits a…

Representation Theory · Mathematics 2015-03-18 Cosima Aquilino , Rebecca Reischuk

A functor on compact Hausdorf spaces is constructed as the sum of certain equivariant K-theory groups. It is shown that the functor takes values in lambda-rings and satisfies a Thom isomorphism. In the case that the space is a CW-complex…

Algebraic Topology · Mathematics 2013-09-18 Joseph C. Johnson

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

For a countable group $G$ we construct a small, idempotent complete, symmetric monoidal, stable $\infty$-category $\mathrm{KK}^{G}_{\mathrm{sep}}$ whose homotopy category recovers the triangulated equivariant Kasparov category of separable…

Operator Algebras · Mathematics 2025-12-03 Ulrich Bunke , Alexander Engel , Markus Land

We give a functorial construction of equivariant spectra from a generalized version of Mackey functors in categories. This construction relies on the recent description of the category of equivariant spectra due to Guillou and May. The key…

Algebraic Topology · Mathematics 2015-05-27 Anna Marie Bohmann , Angélica M. Osorno

For any finite group G with a finite G-set X and a modular tensor category C we construct a part of the algebraic structure of an associated G-equivariant monoidal category: For any group element g in G we exhibit the module category…

Quantum Algebra · Mathematics 2010-06-22 Till Barmeier

We generalize the construction of tensor categories of endomorphisms of a type III factor $M$ associated with a $G$-kernel, from the case of a discrete group $G$ to that of a compact second countable group. Our approach is based on the…

Operator Algebras · Mathematics 2026-05-19 Marcel Bischoff , Pradyut Karmakar

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 construct a modular functor which takes its values in the monoidal bicategory of finite categories, left exact functors and natural transformations. The modular functor is defined on bordisms that are 2-framed. Accordingly we do not need…

Quantum Algebra · Mathematics 2022-03-24 Jürgen Fuchs , Gregor Schaumann , Christoph Schweigert

We show that the spectral Mackey functors associated to the equivariant algebraic $K$-theory spectra of Guillou-May and Merling (originally constructed using pointset models) can be described purely $\infty$-categorically in terms of the…

Algebraic Topology · Mathematics 2025-08-18 Tobias Lenz

In this paper we introduce the notion of a categorical Mackey functor. This categorical notion allows us to obtain new Mackey functors by passing to Quillen's $K$-theory of the corresponding abelian categories. In the case of an action by…

Category Theory · Mathematics 2014-07-16 Sebastian Burciu

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 provide a unifying approach to different constructions of the algebraic $K$-theory of equivariant symmetric monoidal categories. A consequence of our work is that every connective genuine $G$-spectrum is equivalent to the equivariant…

Algebraic Topology · Mathematics 2025-05-13 Maxine Calle , David Chan , Maximilien Péroux

Let $G$ be a finite group and $\mathbb{K}$ a field of characteristic zero. the ring $R_\mathbb{K}(G)$ of virtual characters of $G$ over $\mathbb{K}$ is naturally endowed with a so-called Grothendieck filtration, with associated graded ring…

Representation Theory · Mathematics 2019-05-03 Beatrice I. Chetard

We study collections of additive categories $\mathcal{M}(G)$, indexed by finite groups $G$ and related by induction and restriction in a way that categorifies usual Mackey functors. We call them `Mackey 2-functors'. We provide a large…

Representation Theory · Mathematics 2020-09-16 Paul Balmer , Ivo Dell'Ambrogio

Tambara functors are an equivariant generalization of rings that appear as the homotopy groups of genuine equivariant commutative ring spectra. In recent work, Blumberg and Hill have studied the corresponding algebraic structures, called…

Algebraic Topology · Mathematics 2024-01-31 David Chan