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Over the real numbers with $\Z/2-$coefficients, we compute the $C_2$-equivariant Borel motivic cohomology ring, the Bredon motivic cohomology groups and prove that the Bredon motivic cohomology ring of the real numbers is a proper subring…

Algebraic Geometry · Mathematics 2025-05-28 Bill Deng , Mircea Voineagu

The additive structure of the $RO(C_{pq})$-graded Bredon cohomology $S^0$ with coefficients in the constant Mackey functor was computed in \cite{BG19}. Using that computation, the ring structure in the positive degrees has been computed…

Algebraic Topology · Mathematics 2024-04-25 Surojit Ghosh

We are interested in computing the Bredon cohomology with coefficients in the constant Mackey functor $\underline{ \mathbb{F}_2}$ for equivariant $\text{Rep}(C_2)$ spaces, in particular for Grassmannian manifolds of the form…

Algebraic Topology · Mathematics 2025-03-14 Eric Hogle

We describe the equivariant cohomology ring of rationally smooth projective embeddings of reductive groups. These embeddings are the projectivizations of reductive monoids. Our main result describes their equivariant cohomology in terms of…

Algebraic Geometry · Mathematics 2015-07-21 Richard Gonzales

In equivariant algebra, Mackey functors replace abelian groups and incomplete Tambara functors replace commutative rings. In this context, we prove that equivariant Hochschild homology can sometimes be computed using Mackey functor-valued…

Algebraic Topology · Mathematics 2024-07-29 David Mehrle , J. D. Quigley , Michael Stahlhauer

We give an algorithm to compute the following cohomology groups on $U = \C^n \setminus V(f)$ for any non-zero polynomial $f \in \Q[x_1, ..., x_n]$; 1. $H^k(U, \C_U)$, $\C_U$ is the constant sheaf on $U$ with stalk $\C$. 2. $H^k(U, \Vsc)$,…

Algebraic Geometry · Mathematics 2007-05-23 Toshinori Oaku , Nobuki Takayama

We study the $S_n$-equivariant log-concavity of the cohomology of flag varieties, also known as the coinvariant ring of $S_n$. Using the theory of representation stability, we give computer-assisted proofs of the equivariant log-concavity…

Representation Theory · Mathematics 2022-05-13 Tao Gui

We introduce the $C_{p^n}$-Mahowald invariant: a relation $\pi_\star S_{C_{p^{n-1}}} \rightharpoonup \pi_\ast S$ between the equivariant and classical stable stems which reduces to the classical Mahowald invariant when $n=1$. We compute the…

Algebraic Topology · Mathematics 2025-03-20 William Balderrama , Yueshi Hou , Shangjie Zhang

This note contains a generalization to $p>2$ of the authors' previous calculations of the coefficients of $(\mathbb{Z}/2)^n$-equivariant ordinary cohomology with coefficients in the constant $\mathbb{Z}/2$-Mackey functor. The algberaic…

Algebraic Topology · Mathematics 2020-02-14 John Holler , Igor Kriz

We introduce equivariant Chow-Witt groups in order to define Chow-Witt groups of quotient stacks. We compute the Chow-Witt ring of the moduli stack of stable (resp. smooth) elliptic curves, providing a geometric interpretation of the new…

Algebraic Geometry · Mathematics 2023-05-11 Andrea Di Lorenzo , Lorenzo Mantovani

We compute the complete RO(G)-graded coefficients of "ordinary" cohomology with coefficients in Z/2 for G=(Z/2)^n.

Algebraic Topology · Mathematics 2017-03-22 John Holler , Igor Kriz

We introduce the theory of biset functors defined on finite categories. Previously, biset functors have been defined on groups, and in that context they are closely related to Mackey functors. Standard examples on groups include…

Representation Theory · Mathematics 2023-07-18 Peter Webb

We consider quotients of complete flag manifolds in Cn and Rn by an action of the symmetric group on n objects. We compute their cohomology with field coefficients of any characteristic. Specifically, we show that these topological spaces…

Algebraic Topology · Mathematics 2023-12-20 Lorenzo Guerra , Santanil Jana

A driving question in (quantum) cohomology of flag varieties is to find non-recursive, positive combinatorial formulas for expressing the product of two classes in a particularly nice basis, called the Schubert basis. Bertram,…

Algebraic Geometry · Mathematics 2020-08-11 Anna Bertiger , Elizabeth Milićević , Kaisa Taipale

We study analogues of Kronecker coefficients for symmetric inverse semigroups, for dual symmetric inverse semigroups and for the inverse semigroups of bijections between subquotients of finite sets. In all cases we reduce the problem of…

Representation Theory · Mathematics 2025-01-29 Volodymyr Mazorchuk , Shraddha Srivastava

We compute the equivariant homology and cohomology of projective spaces with integer coefficients. More precisely, in the case of cyclic groups, we show that the cellular filtration of the projective space $P(k\rho )$, of lines inside…

Algebraic Topology · Mathematics 2025-09-24 Samik Basu , Pinka Dey , Aparajita Karmakar

We establish a novel approach to computing $G$-equivariant cohomology for a finite group $G$, and demonstrate it in the case that $G = C_{p^n}$. For any commutative ring spectrum $R$, we prove a symmetric monoidal reconstruction theorem for…

Algebraic Topology · Mathematics 2023-04-03 David Ayala , Aaron Mazel-Gee , Nick Rozenblyum

Let $C_2$ denote the cyclic group of order 2. We compute the $RO(C_2)$-graded cohomology of all $C_2$-surfaces with constant integral coefficients. We show when the action is nonfree, the answer depends only on the genus, the orientability…

Algebraic Topology · Mathematics 2021-12-10 Christy Hazel

For the cyclic group $C_2$ we give a complete description of the derived category of perfect complexes of modules over the constant Mackey ring $\underline{\mathbb{Z}/\ell}$, for $\ell$ a prime. This is fairly simple for $\ell$ odd, but for…

Algebraic Topology · Mathematics 2023-07-03 Daniel Dugger , Christy Hazel , Clover May

We restructure and advance the classification theory of finite racks and quandles by employing powerful methods from transformation groups and representation theory, especially Burnside rings. These rings serve as universal receptacles for…

Representation Theory · Mathematics 2025-07-03 Nadia Mazza , Markus Szymik