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Homotopy theory, homological algebra, algebraic treatments of manifolds.

11 votes
1 answer
609 views

homotopy and (co)filtered limits

Suppose we have a (co)filtered digaram $\dots \rightarrow X_{2}\rightarrow X_{1}$ of topological space. Is is true that the natural map $\pi_{0}[\lim X_{i}]\rightarrow \lim \pi_{0}(X_{i})$ is an isomo …
Ofra's user avatar
  • 1,613
5 votes
0 answers
203 views

homotopy type of box topology.

Suppose that $X$ is weakly equivalent to a point. Let $I$ be a set. Does $\prod_{i\in I}X$ weakly equivalent to a point, where $\prod_{i\in I}X$ is equipped with box topology ?
Ofra's user avatar
  • 1,613
8 votes
1 answer
1k views

higher algebraic homotopy groups for schemes?

I think I understand how to define the algebraic fundamental group $\pi^{alg}_{1}(X)$ of a scheme and I think I understand the relation between $\pi^{alg}_{1}(X)$ and $\pi_{1}(X(\mathbb{C}))$, where …
Ofra's user avatar
  • 1,613
3 votes
1 answer
327 views

Bisimplicial sets and homology

I'm not sure about the following result: Theorem (?): Let $f_{\bullet,\bullet}: X_{\bullet,\bullet}\rightarrow Y_{\bullet,\bullet}$ a map of bisimplicial sets such that for any natural number $n$, …
Ofra's user avatar
  • 1,613
0 votes

rational cohomology of symmetric groups

If you want to prove that group cohomology $H^{\ast}(\Sigma_{n},\mathbb{Q})=0$ you use the fact that $\mathbb{Q}$ is a projective $\mathbb{Q}[\Sigma_{n}]$-module (Maschke’s theorem) therefore by defin …
Ofra's user avatar
  • 1,613