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20 votes
1 answer
1k views

Torsion in the Atiyah–Hirzebruch spectral sequence of a classifying space

Let $G$ be a compact, connected Lie group. There is an Atiyah–Hirzebruch spectral sequence $$H^*(BG;K^*) \implies K^*(BG)$$ connecting $H^*BG$, which generally contains torsion, with $K^*BG \cong \...
jdc's user avatar
  • 2,995
8 votes
1 answer
525 views

fibrations of classifying spaces - Leray Hirsch Theorem converse

Let $G$ be a topological group and let $H$ be a closed subgroup. Assume that $G \rightarrow G/H$ is a principal $H$-bundle. We have a fibration of classyifing spaces $$G/H \rightarrow BH \rightarrow ...
C. Zhihao's user avatar
  • 283
6 votes
1 answer
411 views

Cohomology of BG, G non-connected Lie group, and spectral sequence relating to classifying space of connected component of the identity

Suppose $G$ is a Lie group, with $\pi_0(G)$ not necessarily finite, but might as well assume $G_0$, the connected component of the identity, is compact. In the case that $\pi_0(G)$ is finite, then we ...
David Roberts's user avatar
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6 votes
1 answer
284 views

Calculating topological index

Consider the space $X=BSL(8,\mathbb{C})/(\mathbb{Z}/2)$. The topological Brauer group of $X$ is given by $Br_{top}(X)=Tor(H^{3}(X;\mathbb{Z}))=\mathbb{Z}/2$. I'm studying concepts of topological ...
Faye3's user avatar
  • 317
4 votes
2 answers
409 views

Classifying space of a non-discrete group and relationship between group homology and topological homology of Lie groups

I have a very soft question which might be very standard in textbooks or literature but I haven't seen it. To a fixed group $G$ we may attach different topologies to make it different topological ...
XYC's user avatar
  • 441
3 votes
1 answer
260 views

non-simple local coefficient system on a fibration of classifying spaces

Long story short; I posted in MSE https://math.stackexchange.com/questions/2500745/local-system-of-coefficients-on-a-fibration-of-classyfing-spaces It is well known that if $G$ is a lie group ...
C. Zhihao's user avatar
  • 283
3 votes
0 answers
90 views

Topological groups satisfying the Borel transgression theorem

I am using the Borel transgression theorem as given in Mimura and Toda's "Topology of Lie groups I and II", page 378, Theorem 2.7. I know that it applies when the fiber has the homotopy type ...
Andrew Davis's user avatar
3 votes
0 answers
224 views

Cohomology ring $H^*(BG,\mathbb{Z}_2)$ for $G=\mathbb{Z}_2\ltimes B^2\mathbb{Z}^2$

$$ \newcommand{\Z}{\mathbb{Z}} $$ Consider the group $G=\Z_2\ltimes B^2\Z^2$ where $\Z_2$ acts on $\Z^2$ by interchanging the two factors of $\Z^2$, hence $\Z_2$ also acts on the Eilenberg-MacLane ...
wonderich's user avatar
  • 10.5k
2 votes
1 answer
712 views

Oriented Bordism Group and Un-Oriented Bordism Group of points $pt$

Do we know, or are there any References that list down complete oriented and unoriented Bordism Group $Ω_{n,O}(pt)$ and $Ω_{n,SO}(pt)$ of points $pt$ for dimensions $n=1,2,...,10$? Here are some ...
wonderich's user avatar
  • 10.5k