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Search options not deleted user 23571
79 votes
Accepted

Maps which induce the same homomorphism on homotopy and homology groups are homotopic

Take the composition of a degree one map $f:T^3\to S^3$ with the Hopf map $g:S^3\to S^2$, where $T^3$ is the 3-torus. This composition is trivial on homotopy groups since $T^3$ is aspherical and $\pi_ …
Allen Hatcher's user avatar
28 votes
Accepted

Is the space of diffeomorphisms homotopy equivalent to a CW-complex?

Here is an example where ${\rm Diff}(M)$ with the compact-open topology is not homotopy equivalent to a CW complex. Take $M$ to be a surface of infinite genus, say the simplest one with just one nonco …
Allen Hatcher's user avatar
13 votes
Accepted

How can I endow a "locally product" CW structure on a vector bundle over a CW complex?

The authors of this book are attempting to use CW structures to justify certain cohomology isomorphisms, but this seems to be the wrong approach since some of their claims about CW structures are just …
Allen Hatcher's user avatar
4 votes
Accepted

Relationship between quotient CW-complexes after attaching cells

If I understand the question correctly, you have a CW complex $Y'$ which is the union of two subcomplexes $Y$ and $X'$ whose intersection is the subcomplex $X$. We can first collapse $X$ to a point t …
Allen Hatcher's user avatar