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Tambara functors arise in equivariant homotopy theory as the structure adherent to the homotopy groups of a coherently commutative equivariant ring spectrum. We show that if $k$ is a field-like $C_{p^n}$-Tambara functor, then $k$ is the…

Algebraic Topology · Mathematics 2025-03-07 Noah Wisdom

We give, for every finite group G, a combinatorial description of the ring of G-Witt vectors on a polynomial algebra over the integers. Using this description we show that the functor, which takes a ring with trivial action of G to its ring…

Commutative Algebra · Mathematics 2007-05-23 Morten Brun

We derive a family of prime ideals of the Burnside Tambara functor for a finite group $G$. In the case of cyclic groups, this family comprises the entire prime spectrum. We include some partial results towards the same result for a larger…

Group Theory · Mathematics 2024-02-26 Maxine Calle , Sam Ginnett

We give a natural notion of (non-exact) integral functor in the context of k-linear and graded categories. In this broader sense, we prove that every k-linear and graded functor is integral.

Algebraic Geometry · Mathematics 2014-02-26 Fernando Sancho de Salas

Functor coalgebras capture a wide range of transition systems that must however evolve in discrete steps. We introduce graded coalgebras of graded monads and propose them to model continuous-time transition systems. We develop the theory of…

Logic in Computer Science · Computer Science 2026-05-08 Elena Di Lavore , Jonas Forster , Mario Román

Let k be a field and denote by SH(k) the motivic stable homotopy category. Recall its full subcategory HI_0(k) of effective homotopy modules. Write NAlg(HI_0(k)) for the category of normed motivic spectra with underlying spectrum an…

K-Theory and Homology · Mathematics 2022-01-12 Tom Bachmann

We investigate scalar restriction, scalar extension, and scalar coextension functors for graded modules, including their interplay with coarsening functors, graded tensor products, and graded Hom functors. This leads to several…

Commutative Algebra · Mathematics 2020-09-15 Fred Rohrer

We provide new examples of \'etale extensions of Green functors by transferring classical examples of \'etale extensions to the equivariant setting. Our examples are Tambara functors, and we prove Green \'etaleness for them, which implies…

Algebraic Topology · Mathematics 2024-06-25 Ayelet Lindenstrauss , Birgit Richter , Foling Zou

An action of the $\mathfrak{sl}_2$-crystal category on graded/mixed (integral) category $\mathcal{O}$ `lifting' the usual tensor product is defined.

Representation Theory · Mathematics 2013-12-31 R. Virk

We introduce the good Hilbert functor and prove that it is algebraic. This functor generalizes various versions of the Hilbert moduli problem, such as the multigraded Hilbert scheme and the invariant Hilbert scheme. Moreover, we generalize…

Algebraic Geometry · Mathematics 2016-11-04 Gustav Sædén Ståhl

For $G$ a finite group and $T$ a $G$-Tambara functor, we construct the frame $\mathop{RadId}_G(T)$ of radical Tambara ideals and show that its points are the Nakaoka primes. We show that this frame is spatial and coherent, and deduce that…

Algebraic Topology · Mathematics 2026-04-22 Drew Heard

In this paper we give necessary and sufficient conditions for a functor to be representable in a strongly generated triangulated category which has a linear action by a graded ring, and we discuss some applications and examples.

Category Theory · Mathematics 2022-12-16 Janina C. Letz

We lift to equivariant algebra three closely related classical algebraic concepts: abelian group objects in augmented commutative algebras, derivations, and K\"ahler differentials. We define Mackey functor objects in the category of Tambara…

Algebraic Topology · Mathematics 2017-01-24 Michael A. Hill

For an arbitrary group $G$, a (semi-)Mackey functor is a pair of covariant and contravariant functors from the category of $G$-sets, and is regarded as a $G$-bivariant analog of a commutative (semi-)group. In this view, a $G$-bivariant…

Category Theory · Mathematics 2010-10-06 Hiroyuki Nakaoka

The aim of this paper is to introduce and study graded and filtered gamma rings and gamma modules. We prove that the filtered $\Gamma$-ring (module) is a generalization of the notion of graded ring (module). Also, we construct a graded…

Rings and Algebras · Mathematics 2022-11-02 Shadi Shaqaqha , Afnan Dagher

We give an introduction to the $\mathbb{Z}$-graded representation theory of the BGG category $\mathcal{O}$ of a complex semisimple Lie algebras, with an emphasis on Soergel's combinatorial $\mathbb{V}$ functor, definitions of…

Representation Theory · Mathematics 2021-10-19 Jun Hu

Tambara modules are strong profunctors between monoidal categories. They've been defined by Tambara in the context of representation theory, but quickly found their way in applications when it was understood Tambara modules provide a useful…

Category Theory · Mathematics 2022-04-25 Matteo Capucci

In this paper we develop computational tools to study the higher algebraic $K$-theory of Green functors. We construct a spectral sequence converging to the algebraic $\mathbb{G}$-theory of any $G$-Green functor, for $G$ a cyclic $p$-group.…

K-Theory and Homology · Mathematics 2025-08-21 David Chan , Noah Wisdom

Tambara functors are the analogue of commutative rings in equivariant algebra. Nakaoka defined ideals in Tambara functors, leading to the definition of the Nakaoka spectrum of prime ideals in a Tambara functor. In this work, we continue the…

Algebraic Topology · Mathematics 2026-03-13 David Chan , David Mehrle , J. D. Quigley , Ben Spitz , Danika Van Niel

We introduce the notion of a random matrix-valued multiplicative function, generalizing Rademacher random multiplicative functions to matrices. We provide an asymptotic for the second moment based on a linear recurrence property for…

Number Theory · Mathematics 2018-12-12 Maxim Gerspach