Proof.
Let be a countable dense subset of , and
be a compact subset with the interior non-empty. Let
be a finite covering of with small Euclidean balls
such that each the concentric balls of half radius still cover .
Let be
sections on , i.e., holomorphic maps with .
Now, we
define a map from to
. Suppose that the point lies inside the ball , and
consider the points inside . Under the Gromov-Hausdorff convergence
of to , a subsequence of these points converges to a point in , because the diameter of is uniformly bounded.
If also lies inside another ball , then
(1.3) (or also [38, (2.10)]) shows that
when . Thus, by passing to subsequences,
both and converge to
the same point under the Gromov-Hausdorff convergence of
to
. We then define
.
For ,
by repeating the above procedure, we obtain
that a subsequence , ,
converges to , , respectively. Define . By
repeating this procedure and with a diagonal argument, we can find a
subsequence of , denoted by also, such
that
converges to along the Gromov-Hausdorff convergence. For any
, define .
Now, we prove that is injective. If it is not true, there are ,
such that , and
, which implies
. If is a minimal
geodesic in connecting
and , then
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by (4.1) for a constant independent
of . Thus, if for ,
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or, if are not empty
by passing
to a subsequence,
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In both cases, we obtain contradictions. Thus is injective.
Note that there is a such that, for any ,
the metric ball is a geodesically convex set, i.e. for any and , there is a minimal geodesic connecting and , which implies
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We take such that there is a with . If , by Proposition 4.6,
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If is a minimal
geodesic in connecting
and , then (4.19) implies that
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for some function as .
If for
by passing to a subsequence,
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since is a minimal geodesic
in . If is not empty for , then there is a . Since , and connects and ,
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In both cases,
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Thus
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i.e. is a
local isometric embedding. If and
are two sequences in such that for , then and for .
Hence and for and any , which implies that
and
are two Cauchy sequences, and converge to a unique point .
By defining , extends
to a unique map, denoted still by , from to which is also a local isometric embedding.
Now we prove that is an open subset of . Let
, i.e. there is a
such that , and let with
for a constant . From the
above construction, for a , and under Gromov-Hausdorff
convergence.
There is a
sequence of points such
that under the Gromov-Hausdorff
convergence. If is a minimal geodesic connecting
and in , then
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Equation (4.19) implies that, for ,
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Thus where is a compact
subset of . By passing to a subsequence,
in . By Proposition 4.6,
when ,
and, thus, under the Gromov-Hausdorff
convergence. The above construction shows that ,
which implies that . Hence is open, and is a
homeomorphism.
Let be a family of compact subsets with . Given each , the above
argument constructs a
local isometric embedding , which is a homeomorphism onto the image .
By the same argument as above,
extends to a local isometric embedding , i.e. , which is a homeomorphism onto the image .
By a diagonal argument, we obtain a local isometry .
∎
Let and such that
under the Gromov-Hausdorff convergence of to , and let
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for any and . By Theorem 1.6 in
[5], there is a continuous function
such that, if under the convergence of to , then
| (5.1) |
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By Theorem 1.10 in
[5], induces a unique Radon
measure on such that
| (5.2) |
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for any , , where is a function of and . For any
compact subset ,
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where
. By scaling and
by one positive number, we assume that
and is a geodesically
convex set.
Proof.
If under
the convergence of to , we claim that a subsequence of converges to a point
under the metric on .
By Lemma 5.1, there is a compact neighborhood of and a
section such
that under the Gromov-Hausdorff
convergence of to .
Thus when . By Lemma
4.1, there
are curves connecting and such
that ,
and
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For a , if there is a , then
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where such that , which is a contradiction.
Thus for ,
and converges to under the metric .
By passing to a subsequence, converges to a point
under the metric .
Since for a constant ,
Hence and .
Let satisfy , and
is a geodesically convex subset of .
If , there is a
curve
connecting and such that
is the unique minimal geodesic connecting and . Thanks to (4.18) we have
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where
when , on
. We obtain that
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If is a minimal geodesic of
connecting and , then (4.19) gives
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If , then
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and, otherwise,
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by the same argument as in the proof of Lemma 5.1. Thus
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where is a constant independent of
, and . Of course if is large we will have that
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Thanks to (4.1), there is constant
independent of such that on . Let
be minimal geodesics of connecting
and , which satisfy for .
Thus
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The
triangle inequality shows that
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Hence there is a function of such that
when , and
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We obtain that
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Note that
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Hence
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when . By (5.1),
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Recall the diameter bound (1.4)
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for a constant .
Using (5.1), we have
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∎