純粋・応用数学・数学隣接分野（含むガロア理論）13

[過去ﾛｸﾞ] 純粋・応用数学・数学隣接分野（含むガロア理論）13 (1002ﾚｽ)
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967: 2023/07/31(月)09:59 ID:jznoxopE(17/50) AAS
Our intension here is to draw similar conclusions by assuming the
curvature conditions only on the complement of a compact subset of
the manifold in quetion

968: 2023/07/31(月)10:01 ID:jznoxopE(18/50) AAS
Theorem 0.2 will be generalized as follows.
Theorem 1.4. Let (M, φ) be a connected and noncompact C^2
pseudoconvex manifold which admits a holomorphic Hermitian line bundle
whose curvature form is positive on M - Mc.
Then there exists a holomorphic embedding of M - Mc into CP^N which
extends to M meromorphically.

969: 2023/07/31(月)10:02 ID:jznoxopE(19/50) AAS
Theorem 0.3 will be extended to
Theorem 1.5. A C^2 pseudoconvex manifold (M, φ) is holomorphically
convex if the canonical bundle is negative outside a compact set.

This extends Grauert’s theorem asserting that strongly 1-convex
manifold are holomorphically convex.

970: 2023/07/31(月)10:05 ID:jznoxopE(20/50) AAS
The proofs will be done by combining the method of Takayama with
an L^2 variant of the Andreotti-Grauert theory [A-G] on complete Hermitian manifolds whose special form needed here will be recalled in§3.
In §4 we shall extend Theorem 0.4 for the domains Ω as in Theorem
0.1. Whether or not Ω in Theorem 0.1 is holomorphically convex is
still open.

971: 2023/07/31(月)10:05 ID:jznoxopE(21/50) AAS
The proof of the desired improvement of Theorem 0.1 will rely on
the following.

972: 2023/07/31(月)10:10 ID:jznoxopE(22/50) AAS
Theorem 2.1. (cf. [Oh-4, Theorem 0.3 and Theorem 4.1]) Let M be
a complex manifold, let Ω ⊊ M be a relatively compact pseudoconvex
domain with a C^2-smooth boundary and let B be a holomorphic line
bundle over M with a fiber metric h whose curvature form is positive
on a neighborhood of ∂Ω. Then there exists a positive integer m0 such
that for all m ≥ m0
dimH^{0,0}(Ω, B^m) = ∞ and that, for any compact
省4

973: 2023/07/31(月)10:12 ID:jznoxopE(23/50) AAS
We shall give the proof of Theorem 1.1 in this section for the convenience of the reader, after recalling the basic L^2
estimates in a general setting.

974: 2023/07/31(月)10:13 ID:jznoxopE(24/50) AAS
Let (M, g) be a complete Hermitian manifold of dimension n and let
(E, h) be a holomorphic Hermitian vector bundle over M.
Let C^{p,q}(M, E) denote the space of E-valued C^∞ (p, q)-forms on M
and letC^{p,q}_0(M, E) = {u ∈ C^{p,q}(M, E); suppu is compact}.

975: 2023/07/31(月)10:15 ID:jznoxopE(25/50) AAS
Given a C^2
function φ : M → R, let L^{p,q}_{(2),φ}(M, E) (= L^{p,q}_{(2),g,φ}(M, E))
be the space of E-valued square integrable measurable (p, q)-forms on
M with respect to g and he^{−φ}
.

976: 2023/07/31(月)10:17 ID:jznoxopE(26/50) AAS
The definition of L^{p,q}_{(2),φ}(M, E) will be
naturally extended for continuous metrics and continuous weights.

977: 2023/07/31(月)10:27 ID:jznoxopE(27/50) AAS
Recall that L^{p,q}_{(2),φ}(M, E) is identified with the completion of
C^{p,q}_0(M, E)
with respect to the L^2 norm
||u||φ := (∫_Me^{−φ}|u|^2_{g,h}dVg)1/2.
Here dVg := 1/n!ω^n
for the fundamental form ω = ω_g of g.

978: 2023/07/31(月)10:29 ID:jznoxopE(28/50) AAS
More explicitly, when E is given by a system of transition functions eαβ with
respect to a trivializing covering {Uα} of M and h is given as a system
of C∞ positive definite Hermitian matrix valued functions hα on Uα satisfying hα =t
eβαhβeβα on Uα ∩ Uβ, |u|2
g,hdVg is defined by tuαhα ∧ ∗uα,
where u = {uα} with uα = eαβuβ on Uα ∩ Uβ and ∗ stands for the
Hodge’s star operator with respect to g. We put ∗¯u = ∗u so that
省1

979: 2023/07/31(月)10:30 ID:jznoxopE(29/50) AAS
Let us denote by ¯∂ (resp. ∂) the complex exterior derivative of
type (0, 1) (resp. (1, 0)). Then the correspondence uα 7→ ¯∂uα defines
a linear differential operator ¯∂ : C
p,q(M, E) → C
p,q+1(M, E). The
Chern connection Dh is defined to be ¯∂ + ∂h, where ∂h is defined by
uα 7→ h
省31

980: 2023/07/31(月)10:32 ID:jznoxopE(30/50) AAS
Θ > 0 (resp. ≥0) for an E^∗ ⊗ E-valued (1,1)-form Θ will mean the positivity (resp.
semipositivity) in this sense.

981: 2023/07/31(月)10:32 ID:jznoxopE(31/50) AAS
Whenever there is no fear of confusion, as well as the Levi form ∂¯∂φ
of φ, Θ_h will be identified with a Hermitian form along the fibers of
E ⊗ TM, where TM stands for the holomorphic tangent bundle of M.

982: 2023/07/31(月)10:33 ID:jznoxopE(32/50) AAS
By an abuse of notation, ¯∂ (resp. ∂he−φ ) will also stand for the maximal closed extension of ¯∂|C
p,q
0
(M,E)
(resp. ∂he−φ |C
p,q
0
省32

983: 2023/07/31(月)10:34 ID:jznoxopE(33/50) AAS
We put
H
p,q
(2),φ
(M, E)(= H
p,q
(2),g,φ
省27

984: 2023/07/31(月)10:34 ID:jznoxopE(34/50) AAS
Let Λ = Λg denote the adjoint of the exterior multiplication by ω.
Then Nakano’s formula
(2.2) ¯∂
¯∂
∗ + ¯∂
∗ ¯∂ − ∂h∂
∗ − ∂
省24

985: 2023/07/31(月)10:35 ID:jznoxopE(35/50) AAS
Here (u, w)φ stands for the inner product of u and v with respect to
(g, he−φ
). The following direct consequence of (1.3) is important for
our purpose.

986: 2023/07/31(月)10:36 ID:jznoxopE(36/50) AAS
Proposition 2.1. Let M, E, g, h and φ be as above. Assume that there
exists a compact set K ⊂ M such that dωg = 0 holds on M \ K. Then
there exist a compact set K′
containing K and a constant C such that
K′ and C do not depend on the choice of φ and
(
√
省23

987: 2023/07/31(月)10:37 ID:jznoxopE(37/50) AAS
From Proposition 1.1 one infers

988: 2023/07/31(月)10:37 ID:jznoxopE(38/50) AAS
Proposition 2.2. Let (M, E, g, h, φ, K) and (K′
, C) be as above. Assume moreover that one can find a constant C0 > 0 such that C0(Θh +
IdE ⊗∂
¯∂φ)−IdE ⊗g ≥ 0 holds on M \K. Then there exists a constant
C
′ depending only on C, K′ and C0 such that
kuk
省24

989: 2023/07/31(月)10:38 ID:jznoxopE(39/50) AAS
By a theorem of Gaffney, the estimate in Proposition 1.2 implies the
following.
Proposition 2.3. In the situation of Proposition 1.2,
kuk
2
φ ≤ C
′
省23

990: 2023/07/31(月)10:38 ID:jznoxopE(40/50) AAS
Recall that the following was proved in [H] by a basic argument of
functional analysis.

991: 2023/07/31(月)10:39 ID:jznoxopE(41/50) AAS
Theorem 2.2. (Theorem 1.1.2 and Theorem 1.1.3 in [H]) Let H1 and
H2 be Hilbert spaces and let T : H1 → H2 be a densely defined closed
operator. Let H3 be another Hilbert space and let S : H2 → H3 be a
densely defined closed operator such that ST = 0. Then a necessary
and sufficient condition for the ranges RT , RS of T, S both to be closed
is that there exists a constant C such that
(2.4) kgkH2 ≤ C(kT
省13

992: 2023/07/31(月)10:40 ID:jznoxopE(42/50) AAS
Hence we obtain

993: 2023/07/31(月)10:40 ID:jznoxopE(43/50) AAS
Theorem 2.3. In the situation of Proposition 1.2, dimH
n,q
(2),φ
(M, E) <
∞ and H n,q
φ
(M, E) ∼= H
省3

994: 2023/07/31(月)10:41 ID:jznoxopE(44/50) AAS
It is an easy exercise to deduce from Theorem 1.3 that every strongly
pseudoconvex manifold is holomorphically convex (cf. [G] or [H]). We
are going to extend this application to the domains with weaker pseudoconvexity.

995: 2023/07/31(月)10:41 ID:jznoxopE(45/50) AAS
For any Hermitian metric g on M, a C
2
function ψ : M → R is called
g-psh (g-plurisubharmonic) if g + ∂
¯∂ψ ≥ 0 holds everywhere.
Then Theorem 1.3 can be restated as follows.

996: 2023/07/31(月)10:42 ID:jznoxopE(46/50) AAS
Theorem 2.4. Let (M, g) be an n-dimensional complete Hermitian
manifold and let (E, h) be a Hermitian holomorphic vector bundle over
M. Assume that there exists a compact set K ⊂ M such that
Θh − IdE ⊗ g ≥ 0 and dωg = 0 hold on M \ K. Then, for any g-psh
function φ on M and for any ε ∈ (0, 1),
dim H
n,q
省7

997: 2023/07/31(月)10:43 ID:jznoxopE(47/50) AAS
§2 Infinite dimensionality and bundle convexity theorems
By applying Theorem 1.4, we shall show at first the following.
Theorem 2.5. Let (M, E, g, h) be as in Theorem 1.4 and let xµ (µ =
1, 2, . . .) be a sequence of points in M without accumulation points.
Assume that there exists a (1 − ε)g-psh function φ on M \ {xµ}
∞
µ=1 for
省7

998: 2023/07/31(月)10:43 ID:jznoxopE(48/50) AAS
Proof. We put M′ = M \{xµ}
∞
µ=1 and let ψ be a bounded C
∞ ε
2
g-psh
function on M′
省51

999: 2023/07/31(月)10:44 ID:jznoxopE(49/50) AAS
Then take u ∈ L
n,0
(2),φ
(M′
, E)
satisfying ¯∂u = v and put s =
?cµsµ − u. Clearly s extends to a
省6

1000: 2023/07/31(月)10:45 ID:jznoxopE(50/50) AAS
This observation will be basic for the proofs of Theorems 0.4 and
0.5.

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