20 DEFINITIONS AND EXAMPLES OF COMPLEX MANIFOLDS
First we construct a Coo vector field 0 on a neighborhood of M,o in ..it
such that 1t induces 7t*(0) = a/as, where s is a member of a coordinate system
(s, x
2
, ••• ,xm) in a neighborhood of the point 10 e B chosen as follows:
Figure 8
We connect 10 and t by an embedded arcy: (-e,1 + e) -+ {yes) I s e( -e,1 + e)}.
A compactness argument shows that we can assume that I and 10 lie in the
same coordinate patch
and since
y is an embedding we can find a chart with
coordinate
(s,
12 , ••. ,1m) around lo(to = (0, ... , 0), I = (s, 0, ... , 0». Because
of the rank condition, 1t-
1(y) = 7t-
I{(s, 0, ···,0) I -e < s < 1 + e}, is a
submanifold
of
..it, and we can assume that (s, xf, ... , xj) are coordinates
of ..it for a given point of 7t -I (y) in some neighborhood qJ J of the point. Then
the vector field (a/as)j on qJj satisfies 1t.(a/as)j = a/as. Then if {Pj} is a parti
tion
of unity subordinate to
{OIl j} (uOU j is a neighborhood of M,o)' the vector
field 0 = LJ pj(a/as)j satisfies our requirements.
For the second part of the proof we seek a solution of the differential
equation
d
ds
xj(r) = 0j[x(r)], (1)
where 0j is the a-component of 0 in the coordinate patch qJ j' with initial
conditions xj(O) = y", where (0, y2, ... , y") is some point close to (0, ···,0).
If s is small enough and Iyl is small enough, Equation (1) has a unique solution
xj(r, y) on some small interval. By compactness, we can assume that M,o c:
U jqJj' a finite union of such patches, and that in each qJj' (1) is satisfied for
Irl < jJ. where jJ. is independent ofj. If xj(r, y) is such a solution, let Xj = jjk(Xk)
and define ef[r,hiO, y)] uniquely on qJj ( qJk by
(2)
Then dxj(r, y) = L axj aef[r,jkj(O, y)]
dr /I axf or '