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In this short note, we compute the rational $C_{2^n}$-equivariant stable stems and give minimal presentations for the $RO(C_{2^n})$-graded Bredon cohomology of the equivariant classifying spaces $B_{C_{2^n}}S^1$ and $B_{C_{2^n}}\Sigma_2$…

Algebraic Topology · Mathematics 2021-04-27 Nick Georgakopoulos

We use relative group cohomologies to compute the Kac cohomology of matched pairs of finite groups. This cohomology naturally appears in the theory of abelian extensions of finite dimensional Hopf algebras. We prove that Kac cohomology can…

Quantum Algebra · Mathematics 2019-07-17 César Galindo , Yiby Morales

For certain contractible G-CW-complexes and F a family of subgroups of G, we construct a spectral sequence converging to the F-Bredon cohomology of G with E1-terms given by the F-Bredon cohomology of the stabilizer subgroups. As…

Algebraic Topology · Mathematics 2011-04-14 Fotini Dembegioti , Nansen Petrosyan , Olympia Talelli

We compute the equivariant complex K-theory ring of a cohomogeneity-one action of a compact Lie group at the level of generators and relations and derive a characterization of K-theoretic equivariant formality for these actions. Less…

Algebraic Topology · Mathematics 2022-03-15 Jeffrey D. Carlson

We show that the twisted Bredon-Illman cohomology defined by Mukherjee-Mukherjee applied to compact Lie group action groupoids is Morita-invariant. This cohomology uses coefficient systems twisted over the discrete tom Dieck equivariant…

Algebraic Topology · Mathematics 2025-07-08 Carla Farsi , Laura Scull , Jordan Watts

We study Bredon homology approximations for spaces with an action of a compact Lie group G. We show that if M is a coMackey functor satisfying mild p-locality conditions, then Bredon homology of a G-space X with coefficients in M is…

Algebraic Topology · Mathematics 2020-02-28 Gregory Z. Arone , William G. Dwyer , Kathryn Lesh

Let G be a discrete group and let X be a G-finite, proper G-CW-complex. We prove that Kasparov's equivariant K-homology groups KK^G(C_0(X),\C) are isomorphic to the geometric equivariant K-homology groups of X that are obtained by making…

K-Theory and Homology · Mathematics 2012-10-12 Paul Baum , Nigel Higson , Thomas Schick

Let $M$ be a covariant coefficient system for a finite group $G$. In this paper we analyze several topological abelian groups, some of them new, whose homotopy groups are isomorphic to the Bredon-Illman $G$-equivariant homology theory with…

Algebraic Topology · Mathematics 2011-02-01 Marcelo A. Aguilar , Carlos Prieto

Quasiperiodic patterns described by polyhedral "atomic surfaces" and admitting matching rules are considered. It is shown that the cohomology ring of the continuous hull of such patterns is isomorphic to that of the complement of a torus…

Mathematical Physics · Physics 2007-05-23 Pavel Kalugin

Let G be a discrete group. We give methods to compute for a generalized (co-)homology theory its values on the Borel construction (EG x X)/G of a proper G-CW-complex X satisfying certain finiteness conditions. In particular we give formulas…

K-Theory and Homology · Mathematics 2012-01-24 Michael Joachim , Wolfgang Lueck

We give a construction for twisted equivariant K-theory in the case of a proper action of a discrete group using twisted bundles. Our construction uses results of Lueck and Oliver to extend a construction of Adem and Ruan. We also show the…

K-Theory and Homology · Mathematics 2007-10-12 Christopher Dwyer

In this paper, we prove an equivariant version of the classical Dold-Thom theorem. Associated to a finite group, a CW-complex on which this group acts and a covariant coefficient system in the sense of Bredon, we functorially construct a…

Algebraic Topology · Mathematics 2007-08-01 Zhaohu Nie

In this paper we show a Kunneth formula for Bredon cohomology for actions of a pullback of groups. We show how this formula can be used to compute orbifold twisted K-theory for some discrete twistings. Using that result we compute orbifold…

Algebraic Topology · Mathematics 2016-01-21 German Combariza , Mario Velasquez

Let $M$ be a symplectic manifold, equipped with a Hamiltonian action of a torus $T$. We give an explicit formula for the rational cohomology ring of the symplectic quotient $M//T$ in terms of the cohomology ring of $M$ and fixed point data.…

Differential Geometry · Mathematics 2007-05-23 Susan Tolman , Jonathan Weitsman

We sudy the behaviour of endomorphisms and automorphisms of groups involved in abelian group extensions. The main result can be stated as follows: Let $0\to N\to G\to Q \to 1$ be an abelian group extension. Then one has the following exact…

Group Theory · Mathematics 2015-12-11 Mariam Pirashvili

We prove equivariant versions of the Beilinson-Lichtenbaum conjecture for Bredon motivic cohomology of smooth complex and real varieties with an action of the group of order two. This identifies equivariant motivic and topological…

Algebraic Topology · Mathematics 2018-03-20 Jeremiah Heller , Mircea Voineagu , Paul Arne Ostvaer

The rational Borel equivariant cohomology for actions of a compact connected Lie group is determined by restriction of the action to a maximal torus. We show that a similar reduction holds for any compact Lie group $G$ when there is a…

Algebraic Topology · Mathematics 2024-02-14 Sergio Chaves

Under certain integrability and geometric conditions, we prove division theorems for the exact sequences of holomorphic vector bundles and improve the results in the case of Koszul complex. By introducing a singular Hermitian structure on…

Differential Geometry · Mathematics 2011-12-02 Qingchun Ji

In this paper we present the notion of de Rham cohomology with compact support for diffeological spaces. Moreover we shall discuss the existence of three long exact sequences. As a concrete example, we show that long exact sequences exist…

Algebraic Topology · Mathematics 2014-04-07 Tadayuki Haraguchi

In the mid 1980s, while working on establishing completion theorems for equivariant Algebraic K- Theory similar to the well-known Atiyah-Segal completion theorem for equivariant topological K-theory, the late Robert Thomason found the…

Algebraic Geometry · Mathematics 2019-10-29 Gunnar Carlsson , Roy Joshua