Talk:Normal maps - (non)-examples (Ex)

Revision as of 02:02, 10 January 2019

1) Suggestion: in any manifold, you can find an open ball $<wikitex>; 1) Suggestion: in any manifold, you can find an open ball $D^n$. $S^n$ is the one-point compactification of $D^n$. The rest of the manifold may be very complicated, but we can send all of it to the remaining point. 2) Suggestion: If you can find one open ball, you can find a few. Use enough open balls until you have the right degree. 3) Suggestion: Looking at the CW-complex structure that looks like a n$-polygon, send the 2D cell in one complex to the other. The borders then need to match up (in a sense). Key words: 1-skeleton, cellular map </wikitex>D^n$. $S^n$ is the one-point compactification of $D^n$. The rest of the manifold may be very complicated, but we can send all of it to the remaining point.

2) Suggestion: If you can find one open ball, you can find a few. Use enough open balls until you have the right degree.

3) Suggestion: Looking at the CW-complex structure that looks like a $4n$-polygon, send the 2D cell in one complex to the other. The borders then need to match up (in a sense). Key words: 1-skeleton, cellular map