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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
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Relative de rham cohomology with compact support

Not necessarily. For simplicity, let's assume a closed manifold $M$ and a closed submanifold $P$. Then all forms automatically have closed support and the de Rham cohomology is isomorphic to singular …
Greg Friedman's user avatar
4 votes
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Whitney stratifications of hypersurfaces

In order for transversality to make sense, I assume that X is contained in an ambient manifold? Assuming so, the following statement is on page 37 of Goresky and MacPherson's Stratified Morse Theory: …
Greg Friedman's user avatar
6 votes
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references / general idea of kervaire invariant problem

Here's a recent survey article by Victor Snaith: http://chucha.math.cinvestav.mx/morfismos/v13n2/arfsurveyMFMS.pdf (I think there's also a copy on the arxiv)
Greg Friedman's user avatar
5 votes

Books in advanced differential topology

Avoiding suggestions already made: Guillemin and Pollack, Differential Topology, is a classic. You can also find pieces of a lot of these things in books that are a bit broader, for example: Topology …
Greg Friedman's user avatar
2 votes
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Relation between cohomological dimensions of manifolds

By Bredon's Sheaf Theory, Proposition II.16.15, if $X$ is locally paracompact then $\dim_L X\leq \dim_{\mathbb Z}X$ for any ring $L$ with unit. So that should answer the question about the relation be …
Greg Friedman's user avatar
10 votes

Exotic smooth structures on Lie groups?

According to the introduction to the following paper of Farrell and Jones, if $n>4$ and $\Sigma^n$ is any exotic homotopy sphere, then $T^n\#\Sigma^n$ is not diffeomorphic to $T^n$. So lots of higher- …
Greg Friedman's user avatar
9 votes
Accepted

Bott & Tu differential forms Example 10.1

In my version of Bott and Tu, the example reads (emphasis mine): "Moreover, if $V \subset U$ is an inclusion of CONTRACTIBLE open sets, then $\rho^U_V: H^q(\pi^{-1} U) \to H^q( \pi^{-1} V)$ is an isom …
Greg Friedman's user avatar
3 votes

A question on relation of different triangulations of a triangulable space

I'm not completely sure what you're asking, since there are a few things in your question that are unclear. For example, when one talks about chains being homologous, usually the interest is in cycles …
Greg Friedman's user avatar
15 votes
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Any shortcuts to understanding the properties of the Riemannian manifolds which are used in ...

The proof of the existence of good covers is contained in Bott & Tu on pages 42-43, though that proof does refer out to Spivak (see below). In general, if your main goal is to study (algebraic) topolo …
Greg Friedman's user avatar
10 votes

Integral homology classes that can be represented by immersed submanifolds but not embedded ...

I don't know if you'll find this a satisfying example, but what about $2\in \mathbb{Z} \cong H_1(S^1)$? This can be represented by the immersion that wraps the circle twice around itself, but it can't …
Greg Friedman's user avatar