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View Full Version : John Lee,Smooth mfds exercise 2.16


seydunas
Oct9-11, 02:54 PM
Hi,

i have tried to solve exercise2.16 in Lee' s book, smooth manifolds: Let X be a top. mfd with the propert that for every open cover O there exist partition of unity subordinate to O. Show X is paracompact.

I think there is a trick to construct locally refinement open cover by using the conditions of partition of unity. But i can not find it. Can you help me?

mathwonk
Oct9-11, 08:08 PM
I don't even remember the definitions, but isn't this trivial? re-read the definition of partition of unity and see if it doesn't involve a locally finite condition. remember the set where a continuous function does not vanish is open. i believe this is a tautology, i.e. like proving A+B implies B. see if you agree.

seydunas
Oct24-11, 01:53 PM
If we can take the interior of support coming from partition of unity, we are done.