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Building on work of Hill, Hoyer and Mazur we propose an equivariant version of a Loday construction for $G$-Tambara functors where $G$ is an arbitrary finite group. For any finite simplicial $G$-set and any $G$-Tambara functor, our Loday…

Algebraic Topology · Mathematics 2025-07-08 Ayelet Lindenstrauss , Birgit Richter , Foling Zou

Let $G$ be a commutative affine algebraic group over a field $F$, and let $H \colon \mathrm{Fields}_{F} \to \mathrm{AbGrps}$ be a functor. A (homomorphic) $H$-invariant of $G$ is a natural transformation $\mathrm{Tors}(-, G) \to H$, where…

Algebraic Geometry · Mathematics 2020-06-23 Alexander Wertheim

For a "genuine" equivariant commutative ring spectrum $R$, $\pi_0(R)$ admits a rich algebraic structure known as a Tambara functor. This algebraic structure mirrors the structure on $R$ arising from the existence of multiplicative norm…

Algebraic Topology · Mathematics 2018-03-16 Andrew J. Blumberg , Michael A. Hill

By results of Rognerud, a source algebra equivalence between two $p$-blocks of finite groups induces an equivalence between the categories of cohomological Mackey functors associated with these blocks, and a splendid derived equivalence…

Group Theory · Mathematics 2015-10-07 Markus Linckelmann

The purpose of this paper is mainly to record how certain homotopy-theoretical constructions on ordinary G-equivariant cohomology spectra HM for a Mackey functor M, in particular products and duality, can be described on chain level. We…

Algebraic Topology · Mathematics 2022-05-25 Sophie Kriz

Let $G$ be a finite group. In this paper, we first introduce a new notion, so-called the Mackey double category of $G$. Then we prove that the category of Mackey double categories and the category of Mackey functors of $G$ are equivalent.

Group Theory · Mathematics 2026-03-18 Mawei Wu

Let $G$ be a finite group, and $k$ an integer. In this note, we show that for any $G$-Tambara functor $T$ and any subgroups $H_1, H_2 \leq G$, $k$ is a unit in $T(G/H_1)$ if and only if $k$ is a unit in $T(G/H_2)$. In other words, one may…

Group Theory · Mathematics 2026-01-27 Ben Spitz

The first word in the title is intended in a sense suggested by Lawvere and Schanuel whereby finite sets are objective natural numbers. At the objective level, the axioms defining abstract Mackey and Tambara functors are categorically…

Category Theory · Mathematics 2025-04-22 Ross Street

Spectral Mackey functors are homotopy-coherent versions of ordinary Mackey functors as defined by Dress. We show that they can be described as excisive functors on a suitable infinity-category, and we use this to show that universal…

Algebraic Topology · Mathematics 2014-06-03 C. Barwick

Equivariant Loday constructions are a means for providing geometric interpretations of equivariant homology theories. They are usually constructed for a simplicial $G$-set and a $G$-Tambara functor. We study situations where -- depending on…

Algebraic Topology · Mathematics 2026-03-16 Ayelet Lindenstrauss , Birgit Richter , Foling Zou

Tambara functors are equivariant analogues of rings arising in representation theory and equivariant homotopy theory. We introduce the notion of a clarified Tambara functor and show that under mild conditions every Tambara functor admits a…

Algebraic Topology · Mathematics 2025-08-14 Noah Wisdom

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. Given a finite G-set X and a modular tensor category C, we construct a weak G-equivariant fusion category, called the permutation equivariant tensor category. The construction is geometric and uses the formalism of…

Quantum Algebra · Mathematics 2015-03-14 Till Barmeier , Christoph Schweigert

We study the structure of the $RO(G)$-graded homotopy Mackey functors of any Eilenberg-MacLane spectrum $H\underline{M}$ for $G$ a cyclic $p$-group. When $\underline{R}$ is a Green functor, we define orientation classes $u_V$ for…

Algebraic Topology · Mathematics 2025-09-24 Igor Sikora , Guoqi Yan

We define a functor which gives the "global rank of a quiver representation" and prove that it has nice properties which make it a generalization of the rank of a linear map. We demonstrate how to construct other "rank functors" for a…

Representation Theory · Mathematics 2009-03-10 Ryan Kinser

Polynomial functors are a categorical generalization of the usual notion of polynomial, which has found many applications in higher categories and type theory: those are generated by polynomials consisting a set of monomials built from sets…

Logic in Computer Science · Computer Science 2021-12-30 Eric Finster , Samuel Mimram , Maxime Lucas , Thomas Seiller

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

This is the first of a pair of papers where we construct and investigate a closed monoidal structure on the category of generalized algebraic theories (in the sense of Cartmell). In the present text, as a starting point, we define the…

Category Theory · Mathematics 2025-11-18 Daniel Almeida

Mackey functors provide the coefficient systems for equivariant cohomology theories. More generally, enriched presheaf categories provide a classification and organization for many stable model categories of interest. Changing enrichments…

Algebraic Topology · Mathematics 2023-12-06 Niles Johnson , Donald Yau

A graded tensor category over a group $G$ will be called a crossed product tensor category if every homogeneous component has at least one multiplicatively invertible object. Our main result is a description of the crossed product tensor…

Quantum Algebra · Mathematics 2015-10-12 César Galindo