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The study of differentiable manifolds and differentiable maps. One fundamental problem is that of classifying manifolds up to diffeomorphism. Differential topology is what Poincaré understood as topology or “analysis situs”.

2 votes
2 answers
389 views

Contractible noncompact 3-manifold without boundary not homeomorphic to $\Bbb R^3$

I heard this example was given in Whitehead's paper A CERTAIN OPEN MANIFOLD WHOSE GROUP IS UNITY.( http://qjmath.oxfordjournals.org/content/os-6/1/268.full.pdf ) But I was confused by his term. Thus I …
Honglu's user avatar
  • 1,079
8 votes
4 answers
924 views

How does all of the bundles over a certain manifold characterize the homotopy class of the b...

It is known that if $f:M\rightarrow N$ is a homotopy equivalent, then the the process of pullback gives a one-one correspondence between bundles over $N$ and $M$ up to isomorphism. Is the converse( th …
Honglu's user avatar
  • 1,079
8 votes
2 answers
602 views

Can a smooth, immersed loop in R^2 become not nullhomotopic by removing a point?

ATT More precisely, let $\gamma :S^1\rightarrow R^2$ be a smooth immersed loop, the question is whether it is true that there is a point $p\in R^2-\gamma(S^1)$ such that $\gamma$ is not homotopic to …
Honglu's user avatar
  • 1,079