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In this article, we will show that the category of biset functors can be regarded as a reflective monoidal subcategory of the category of Mackey functors on the 2-category of finite groupoids. This reflective subcategory is equivalent to…

Category Theory · Mathematics 2016-01-26 Hiroyuki Nakaoka

In this article, we consider a formulation of biset functors using the 2-category of finite sets with variable finite group actions. We introduce a 2-category $\mathbb{S}$, on which a biset functor can be regarded as a special kind of…

Category Theory · Mathematics 2015-12-08 Hiroyuki Nakaoka

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

For any finite group G, we define a bivariant functor from the Dress category of finite G-sets to the conjugation biset category, whose objects are subgroups of G, and whose morphisms are generated by certain bifree bisets. Any additive…

Group Theory · Mathematics 2013-01-31 I. Hambleton , L. R. Taylor , E. B. Williams

The theory of bisets has been very useful in progress towards settling the longstanding question of determining units for the Burnside ring. In 2006 Bouc used bisets to settle the question for $p$-groups. In this paper, we provide a…

Representation Theory · Mathematics 2018-07-30 Jamison Barsotti

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 compare the bicategory of spans with that of bisets (a.k.a. bimodules, distributors, profunctors) in the context of finite groupoids. We construct in particular a well-behaved pseudo-functor from spans to bisets. This yields an…

Category Theory · Mathematics 2020-09-10 Ivo Dell'Ambrogio , James Huglo

We introduce and study the category of $p$-bifree biset functors for a fixed prime $p$, defined via bisets whose left and right stabilizers are $p'$-groups. This category naturally lies between the classical biset functors and the diagonal…

Representation Theory · Mathematics 2025-05-23 Olcay Coşkun , Deniz Yılmaz

We define the Grothendieck-Witt category over a fixed ground ring. In order to study the structure of this category, we introduce the general theory of Gysin functors and their associated categories of correspondences. The latter…

Algebraic Topology · Mathematics 2016-02-03 Daniel Dugger

We classify simple modules over the Green biset functor of section Burnside rings.

Representation Theory · Mathematics 2021-04-19 Olcay Coşkun , Ruslan Muslumov

Let $p$ be a prime number, let $H$ be a finite $p$-group, and let $\mathbb{F}$ be a field of characteristic 0, considered as a trivial $\mathbb{F} \mathrm{Out}(H)$-module. The main result of this paper gives the dimension of the evaluation…

Group Theory · Mathematics 2021-05-18 Serge Bouc

We generalize Bouc's construction of orthogonal idempotents in the double Burnside algebra to the setting of the double $\mathbb{C}^\times$-fibered Burnside algebra. This yields a structural decomposition of the evaluations of…

Representation Theory · Mathematics 2026-05-04 Olcay Coşkun , Ruslan Muslumov

We investigate the structure of the monomial Burnside biset functor over a field of characteristic zero, with particular focus on its restriction kernels. For each finite \( p \)-group \( G \), we give an explicit description of the…

Representation Theory · Mathematics 2026-05-22 İbrahim Kaan Aslan , Olcay Coşkun

Fibered Burnside rings appear as Grothendieck rings of fibered permutation representations of a finite group, generalizing Burnside rings and monomial representation rings. Their species, primitive idempotents and their conductors are of…

Representation Theory · Mathematics 2025-03-04 Benjamín García , Alberto G. Raggi-Cárdenas

In this paper, we describe the induction functor from the category of native Mackey functors to the category of biset functors for a finite group $G$ over an algebraically closed field $k$ of characteristic zero. We prove two applications…

Group Theory · Mathematics 2014-08-13 Olcay Coşkun

Let $A$ be an abelian group such that $\mathrm{Hom}(G,A)$ is finite for all finite groups $G$, and let $\mathbb{K}$ be a field of characteristic zero containing roots of unity of all orders equal to finite element orders in $A$. In this…

Representation Theory · Mathematics 2020-09-30 Robert Boltje , Deniz Yılmaz

This note has two purposes: First, to present a counterexample to a conjecture parametrizing the simple modules over Green biset functors, appearing in an author's previous article. This parametrization fails for the monomial Burnside ring…

Group Theory · Mathematics 2013-10-21 Nadia Romero

Let $R$ be a commutative unital ring. We construct a category $\mathcal{C}_R$ of fractions $X/G$, where $G$ is a finite group and $X$ is a finite $G$-set, and with morphisms given by $R$-linear combinations of spans of bisets. This category…

Category Theory · Mathematics 2019-10-02 Jesús Ibarra , Alberto G. Raggi-Cárdenas , Nadia Romero

We survey several notions of Mackey functors and biset functors found in the literature and prove some old and new theorems comparing them. While little here will surprise the experts, we draw a conceptual and unified picture by making…

Representation Theory · Mathematics 2021-07-21 Ivo Dell'Ambrogio

We develop and extend the theory of Mackey functors as an application of enriched category theory. We define Mackey functors on a lextensive category $\E$ and investigate the properties of the category of Mackey functors on $\E$. We show…

Category Theory · Mathematics 2007-06-21 Ross Street , Elango Panchadcharam
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