Bigraded Poincaré polynomials and the equivariant cohomology of Rep($C_2$)-complexes

Fuente: arXiv
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Main Author: Hogle, Eric
Format: Preprint
Published: 2024
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author Hogle, Eric
author_facet Hogle, Eric
contents 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 $\\text{Gr}_k(V)$ where $V$ is some real representation of $C_2$. It is possible to create multiple distinct $\text{Rep}(C_2)$ constructions of (and hence multiple filtration spectral sequences for) a given Grassmannian. For sufficiently small examples one may exhaustively compute all possible outcomes of each spectral sequence and determine if there exists a unique common answer. However, the complexity of such a computation quickly balloons in time and memory requirements. We introduce a statistic on $\mathbb{M}_2$-modules valued in the polynomial ring $\mathbb{Z}[x,y]$ which makes cohomology computation of Rep($C_2$)-complexes more tractable, and we present some new results for Grassmannians.
format Preprint
id arxiv_https___arxiv_org_abs_2410_01117
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Bigraded Poincaré polynomials and the equivariant cohomology of Rep($C_2$)-complexes
Hogle, Eric
Algebraic Topology
55P91, 14F43, 55N25, 55N91, 14M15
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 $\\text{Gr}_k(V)$ where $V$ is some real representation of $C_2$. It is possible to create multiple distinct $\text{Rep}(C_2)$ constructions of (and hence multiple filtration spectral sequences for) a given Grassmannian. For sufficiently small examples one may exhaustively compute all possible outcomes of each spectral sequence and determine if there exists a unique common answer. However, the complexity of such a computation quickly balloons in time and memory requirements. We introduce a statistic on $\mathbb{M}_2$-modules valued in the polynomial ring $\mathbb{Z}[x,y]$ which makes cohomology computation of Rep($C_2$)-complexes more tractable, and we present some new results for Grassmannians.
title Bigraded Poincaré polynomials and the equivariant cohomology of Rep($C_2$)-complexes
topic Algebraic Topology
55P91, 14F43, 55N25, 55N91, 14M15
url https://arxiv.org/abs/2410.01117