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huyichen Oct10-10 01:04 AM

smooth manifold and constant map
Suppose M and N are smooth manifold with M connected, and F:M->N is a smooth map and its pushforward is zero map for each p in M. Show that F is a constant map.

I just remember from topology, the only continuous functions from connected space to {0,1} are constant functions. With this be useful in solving the problem?

quasar987 Oct10-10 08:11 AM

Re: smooth manifold and constant map
Show that if M is connected, then a locally constant map F:M-->N is (every pt has an open nbhd where F is constant) is constant.

Then show that a vanishing pushfoward implies that F is locally constant.

Tinyboss Oct10-10 10:29 PM

Re: smooth manifold and constant map
If you define a path between arbitrary points of M, your domain becomes [0,1] which is easier to work with. If you're using Lee (I think I remember this exercise) you have as a theorem that connected manifolds are path connected.

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