z***e
发帖数: 1757 | 1 a set A is dense in universal set X means every point in X is either
a point in A or a limit point of A. | y**t
发帖数: 50 | 2 for every open subset U of X,we have U intersects A!=empty
or the closure of A is X,A is dense in X
diffeomorphism means there exists a bijective C^{infinity}
map f from top. space X to Y such that f^{-1} is also
C^{infinity}
I wonder if you dunno these 2 concepts,how could you
understand the material you are reading?
【在 z***e 的大作中提到】
: a set A is dense in universal set X means every point in X is either
: a point in A or a limit point of A.
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