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12 votes
1 answer
369 views

Approximate classifying space by boundaryless manifolds?

As pointed out by Achim Krause, any finite CW complex is homotopy equivalent to a manifold with boundary (by embedding into $\mathbb R^n$ and thickening), and so every finite type CW complex can be ...
0207's user avatar
  • 123
5 votes
0 answers
133 views

Specify the embedding of Lie groups (via the representation map) precisely as the embedding of two differentiable manifolds

How do we specify the embedding of a Lie group $G_1$ as a subgroup into a larger Lie group $G_2$, with $G_1 \subset G_2$ that agree with a constraint on the mapping between their representations? By ...
wonderich's user avatar
  • 10.4k
6 votes
0 answers
611 views

Quotient space, a fundamental group, and higher homotopy groups 2

Previously, I ask for comments/suggestions on setting up the calculation in Quotient space, homogeneous space, and higher homotopy groups. There, however, I was looking for whatever methods and tools ...
wonderich's user avatar
  • 10.4k
3 votes
0 answers
851 views

Non-Abelian fundamental group? --- a bizarre example

For the quotient space $G=G_0/G_1$, knowing the homotopy groups of $G_0$ and $G_1$, one can determine homotopy groups from the long exact sequence $$ ... \to \pi_n(G_1) \to \pi_n(G_0) \to \...
wonderich's user avatar
  • 10.4k
9 votes
1 answer
711 views

Sullivan conjecture for compact Lie groups

Let $G$ be a topological group, and $M$ a connected compact smooth manifold. I'm studying $$ \pi_0 (map (BG,M)). $$ For $G$ a finite group, we know that this is just a point by the Sullivan ...
Alexander Körschgen's user avatar
3 votes
0 answers
92 views

Cohomology of boundary of locally symmetric space

Let $S$ be a locally symmetric space, not necessarily compact, and $\overline{S}$ be its Borel-Serre compactification. Let $\partial S$ be the boundary of $S$. Let $\widetilde{\mathbb{C}}$ be the ...
Vanya's user avatar
  • 581
12 votes
3 answers
841 views

$A_{\infty}$-structure on closed manifold

Is there an exmaple of a closed smooth connected manifold $M$ having a structure of $A_{\infty}$-space (with unit) but $M$ is not homeomorphic to a compact connectd Lie group as space ? Edit: First, ...
Ilias A.'s user avatar
  • 1,974
41 votes
3 answers
3k views

What is the classifying space of "G-bundles with connections"

Let $G$ be a (maybe Lie) group, and $M$ a space (perhaps a manifold). Then a principal $G$-bundle over $M$ is a bundle $P \to M$ on which $G$ acts (by fiber-preserving maps), so that each fiber is a $...
Theo Johnson-Freyd's user avatar