Second main theorem for holomorphic curves into algebraic varieties intersecting moving hypersurfaces targets
Libing Xie
Department of Mathematics, Nanchang University, Jiangxi 330031, P. R. China
[email protected]
and
Tingbin Cao
Department of Mathematics, Nanchang University, Jiangxi 330031, P. R. China
[email protected] (the corresponding author)
Abstract.
Since the great work on holomorphic curves into algebraic varieties intersecting hypersurfaces in general position established by Ru in 2009, recently there has been some developments on the second main theorem into algebraic varieties intersecting moving hypersurfaces targets. The main purpose of this paper is to give some interesting improvements of Ru’s second main theorem for moving hypersurfaces targets located in subgeneral position with index.
Key words and phrases:
Algebraic varieties; Holomorphic curves; Nevanlinna theory; Moving hypersurfaces
2010 Mathematics Subject Classification:
30D35; 32H30
This paper was supported by the National Natural Science Foundation of China (#11871260, #11461042), the outstanding young talent assistance program of Jiangxi Province (#20171BCB23002) in China.
1. Introduction and main results
It is well-known that in 1933, H. Cartan established Nevanlinna theory for meromorphic functions to the case of linearly nondegenerate holomorphic curves into complex projective spaces intersecting hyperplanes in general position, and conjectured that it is still true for moving hyperplanes targets. From then on, higher dimensional Nevanlinna theory has been studied very hot (refer to [13, 16, 7]). In 2009, Ru [12] proposed a great work on second main theorem of algebraically nondegenerate holomorphic curves into smooth complex varieties intersecting hypersurfaces in general position, which is a generalization of the Cartan’s second main theorem and his own former result [10] completely solving the Shiffman’s conjecture[14] under the motivation of Corvaja-Zannier [15] in Diophantine approximation.
Thus, it is natural and interesting to investigate the Ru’s second main theorem into complex projective spaces and even into complex algebraic varieties for the moving hypersurfaces targets. Based on their affirmation of the Shiffman’s conjecture for moving hypersurfaces targets [3], recently, Dethloff and Tan [2] continue to prove successfully the following theorem. In the special case where the coefficients of the polynomials Qj’s are constant and the variety V is smooth, this is the Ru’s second main theorem [12].
Theorem 1.1**.**
[2]** Let V⊂Pn(C) be an irreducible (possibly singular) variety of dimension ℓ, and let f be a nonconstant holomorphic map of C into V. and let D={D1,…,Dq} be a family of slowly moving hypersurfaces (with respect to f) in general position, and let Q={Q1,…,Qq} be the set of the set of the defining homogeneous polynomials of D with degQj=dj,(j=1,...,q) and Qj(f)≡0 for j=1,…,q. Assume that f is algebraically nondegenerate over KQ. Then, for any ϵ>0,
[TABLE]
holds for all r outside a set with finite Lebesgue measure.
For the special case V=Pn(C), S. D. Quang [8] recently gave a second main theorem with truncated counting functions for meromorphic mappings into Pn(C) intersecting a family of moving hypersurfaces in subgeneral position , which can be possibly good at the uniqueness problems of meromorphic mappings.
Theorem 1.2**.**
[8]**
Let f be a nonconstant meromorphic map of Cm into Pn(C). Let {Qi}i=1q be a collection of slowly moving hypersurfaces in N-subgeneral position with degQj=dj(1≤j≤q). Assume that f is algebraically nondegenerate over KQ. Then, for any ϵ>0,
[TABLE]
holds for all r outside a set with finite Lebesgue measure, where
[TABLE]
with
[TABLE]
d:=lcm(d1,…,dq)* is the least common multiple of all {di},
and*
[TABLE]
In this paper, we mainly combine their methods [2, 8, 17] together and adopt the new concept of the index of subgeneral position due to Ji-Yan-Yu [5] to obtain some interesting developments of Ru’s second main theorem for moving hypersurfaces targets, which are improvements and extensions of Theorem 1.1 and Theorem 1.2.
According to [5], we can give a similar definition for moving hypersurfaces located in m-subgeneral position with index k.
Definition 1.3**.**
Let V be an algebraic subvariety of Pn(C). Let {D1,…,Dq} be a family of moving hypersurfaces of Pn(C). Let N and κ be two positive integers such that N≥dimV≥κ.
(a). The hypersurfaces {D1,…,Dq} are said to be in general position (or say in weakly general position) in V if there exists z∈Cm (if this condition is satisfied for one z∈Cm, it is also satisfied for all z except for a discrete set and the analytic set I(f)={f0=⋯=fn=0} of codimension ≥2) for any subset I⊂{1,…,q} with ♯I≤dimV+1,
[TABLE]
(b). The hypersurfaces {D1,…,Dq} are said to be in N-subgeneral position in V if there exists z∈Cm (if this condition is satisfied for one z∈Cm, it is also satisfied for all z except for a discrete set and the analytic set I(f)={f0=⋯=fn=0} of codimension ≥2) for any subset I⊂{1,…,q} with ♯I≤N+1,
[TABLE]
(c). The hypersurfaces {D1,…,Dq} are said to be in N-general position with index κ in V if D1,…,Dq are in N-subgeneral position and if there exists z∈Cm (if this condition is satisfied for one z∈Cm, it is also satisfied for all z except for a discrete set and the analytic set I(f)={f0=⋯=fn=0} of codimension ≥2) for any subset I⊂{1,…,q} with ♯I≤κ,
[TABLE]
(Here we set dim∅=−∞.)
Now, we state our main result which are an improvement and extension of the above two theorems concerning moving hypersurfaces targets located in subgeneral position with index. Theorem 1.1 is just the following result for the special case whenever N=dimV and κ=1.
Theorem 1.4**.**
Let f:Cm→V⊂Pn(C) be a nonconstant meromorphic map, where V is an irreducible algebraic subvariety of dimension ℓ. Let Q={Q1,…,Qq} be a collection of slowly moving hypersurfaces in N-subgeneral position with index κ in V, and degQj=dj(j=1,…,q,). Assume that f:Cm→V is algebraically nondegenerate over KQ. Then, for any ϵ>0,
[TABLE]
holds for all r outside a set with finite Lebesgue measure
When V=Pn(C), we can have the following second main theorem with truncation, and thus Theorem 1.2 is just the special case whenever κ=1.
Theorem 1.5**.**
Let f be a nonconstant meromorphic map of Cm into Pn(C). Let {Qi}i=1q be a collection of slowly moving hypersurfaces in N-subgeneral position with index κ, and degQj=dj(1≤j≤q). Assume that f is algebraically nondegenerate over KQ. Then, for any ϵ>0,
[TABLE]
holds for all r outside a set with finite Lebesgue measure, where
[TABLE]
with
[TABLE]
d:=lcm(d1,…,dq)* is the least common multiple of all {di}, and*
[TABLE]
Remark that very recently, Yan and Yu [17] considered the nonconstant holomorphic curve from C into Pn(C) instead of algebraically nondegenerate and improved Theorem 1.2 without truncation. Thus it is interesting to ask the following question
Question 1.6**.**
In Theorem 1.4 or Theorem 1.5, is it possible to obtain a second main theorem if the condition “f is algebraically nondegenerate over KQ” is omitted?
The remainder is the organization as follows. In the next section, we introduce some basic notions and auxiliary results from Nevanlinna theory. Section 3 and Section 4 are the proofs of Theorem 1.4 and Theorem 1.5, respecitively, in which the methods to dealing with moving targets by Dethloff-Tan [2], Yan-Yu [17], and the techniques to deal with hypersurfaces in subgeneral position instead of Nochka’s weights owing to Quang [8, 9] are used in this paper.
2. Basic notions and auxiliary results from Nevanlinna theory
2.1. The first main theorem in Nevanlinna theory
We set ∥z∥=(∥z1∥2+⋯+∥zm∥2)1/2 for z=(z1,…,zm)∈Cm and define
[TABLE]
Define
[TABLE]
[TABLE]
Let F be a nonzero meromorphic function on a domain Ω in Cm. For a set α=(α1,…,αm) of nonnegative integers, we set ∣α∣=α1+…+αm and
[TABLE]
We denote by νF0,νF∞ and νF the zero divisor, the pole divisor, and the divisor of the meromorphic function
F respectively.
For a divisor ν on Cm and for a positive integer M or M=∞, we set
[TABLE]
[TABLE]
The counting function of ν is defined by
[TABLE]
Similarly, we define N(r,ν[M]) and denote it by N[M](r,ν).
Let φ is a nonzero meromorphic function on Cm. Define
[TABLE]
For brevity we will omit the character [M] if M=∞.
Let f:Cm⟶Pn(C) be a meromorphic mapping. For arbitrarily fixed homogeneous coordinates
(w0:⋯:wn) on Pn(C), we take a reduced representation f~=(f0,…,fn), which means that each fi is a holomorphic function on Cm and f(z)=(f0(z):⋯;fn(z)) outside the analytic set I(f)={f0=⋯=fn=0} of codimension ≥2. Set ∥f~∥=(∥f0∥2+⋯+∥fn∥2)1/2. The characteristic function of f is defined by
[TABLE]
Let f and Q be as above. The proximity function of f with respect to Q, denoted by mf(r,Q), is defined by
[TABLE]
where Q(f~)=Q(f0,…,fn), and λQ(f~)=log∣Q(f~)∣∥f~∥d∥Q∥ is the Weil function and ∥Q∥=maxI∈Id{∣aI∣}, where Id:={I=(i0,…,in)∈Z≥0n+1;i0+…+in=d}. This definition is independent of the choice of the reduced representation of f.
We denote by f∗Q the pullback of the divisor Q by f. We may see that f∗Q identifies with the zero divisor νQ(f~)0 of the function Q(f~). By Jensen s fomular, we have
[TABLE]
For convenience, we will denote N(r,f∗Q)=NQ(f)(r).
Theorem 2.1**.**
(First Main Theorem).[9]
Let f:Cm⟶Pn(C) be a holomorphic map, and let Q be a hypersurface in Pn(C) of degree d. If f(Cm)⊂Q, then for every real number r with 0<r<+∞,
[TABLE]
where O(1) is a constant independent of r.
Let φ be a nonzero meromorphic function on Cm, which are occasionally regarded as a meromorphic map into P1(C). The proximity function of φ is defined by
[TABLE]
The Nevanlinna’s characteristic function of φ is defined as follows
[TABLE]
Then
[TABLE]
The function φ is said to be small (with respect to f) if ∥Tφ(r)=o(Tf(r)), where here the notion ∥ means that the property holds possibly outside a set with finite Lebesgue measure.
We denote by M (resp. Kf) the field of all meromorphic functions (resp. small meromorphic functions
with respect to f) on Cm.
2.2. Family of moving hypersurfaces
Denote by HCm the ring of all holomorphic functions on Cm. Let Q be a homogeneous polynomial
in HCm[x0,…,xn] of degree d≥1. Denote by Q(z) the homogeneous polynomial over C obtained by substituting a specific point z∈Cm into the coefficients of Q. We also call a moving hypersurface in Pn(C)
each homogeneous polynomial Q∈HCm[x0,…,xn] such that the common zero set of all coefficients of Q
has codimension at least two.
A moving hypersurface Let Q be a moving in Pn(C) of degree d(≥1) is defined by
[TABLE]
where Id={(i0,…,in)∈N0n+1;i0+⋯+in=d}, aI∈HCm, and ωI=ω0i0⋯ωnin. We consider the meromorphic mapping Q′:Cm→PN(C), where N=(nn+d), given by
[TABLE]
Here I0<⋯<IN in the lexicographic ordering. By changing the homogeneous coordinates of Pn(C)
if necessary, we may assume that for each given moving hypersurface as above, aI0=0 (note that I0=
(0,…,0,d) and aI0 is the coefficient of ωnd ). We set
[TABLE]
The moving hypersurfaces Q = {Q1,…,Qq} is said to be ”slow”, (with respect to f ) if ∥TQ′(r)=o(Tf(r)). This is equivalent to ∥TaI0aIj(r)=o(Tf(r))(∀1≤j≤N), i.e., aI0aIj∈Kf.
Let {Qi}i=1q be a family of moving hypersurfaces in Pn(C), degQi=di. Assume that
[TABLE]
We denote by KQ the smallest subfield of meromorphic function field M which contains C and all aiItaiIs, where aiIt≡0, i∈{1,...,q}, It,Is∈Idi. Assume that f is linearly nondegenerate over KQ if there is no nonzero linear form L∈KQ[x0,…,xn] such that L(f0,…,fn)≡0, and f is algebraically nondegenerate over KQ if there is no nonzero homogeneous polynomial Q∈KQ[x0,…,xn] such that Q(f0,…,fn)≡0.
2.3. Some theorems and lemmas
Let f be a nonconstant meromorphic map of Cm into Pn(C). Denote by Cf the set of all non-negative
functions h:Cm\A⟶[0,+∞]⊂R, which are of the form
[TABLE]
where k,l∈N,g1,…,gl+k∈Kf\{0} and A⊂Cm, which may depend on g1,…,gl+k, is an analytic subset of codimension at least two. Then, for h∈Cf we have
[TABLE]
Since Q={Q1,…,Qq} are in N-subgeneral position, we have the following lemma.
Lemma 2.2**.**
[3, 8, 17]**
For any Qj1,…,QjN+1∈Q, there exist functions h1,h2∈Cf such that
[TABLE]
Lemma 2.3**.**
(Lemma on logarithmic derivative, see [6]).
Let f be a nonzero meromorphic function on Cm.
[TABLE]
Proposition 2.4**.**
[4]** Let Φ1,…,Φk be meromorphic functions on Cm such that {Φ1, …,Φk}. are linearly independent over C. Then there exists an admissible set
[TABLE]
*with ∣αi∣=∑j=1m∣αij∣≤i−1(1≤i≤k) such that the following are satisfied:
(i) {DαiΦ1,…,DαiΦk}i=1k is linearly independent over M, i.e., det (DαiΦj)≡0,
(ii) det(Dαi(hΦj))=hk⋅det(DαiΦj) for any nonzero meromorphic function h on Cm.*
Theorem 2.5**.**
(See [11], Theorem 2.31) Let f be a linearly nondegenerate meromorphic mapping of Cm in
Pn(C) with a reduced representation f~=(f0,…,fn) and let H1,…,Hq be q arbitrary hyperplanes in Pn(C). Then we have
[TABLE]
where α is an admissible set with respect to f~ (as in Proposition 2.3) and the maximum is taken over all subsets K⊂{1,…,q} such that {Hj;j∈K} is linearly independent.
3. Proof of Theorem 1.4
Firstly, we may assume that Q1,…,Qq have the same degree degQj=dj=d. Set
[TABLE]
For each j, there exists ajIj(z), one of the coefficients in Qj(z), such that ajIj(z)≡0. We fix this ajIj, then set a~jI(z)=ajIj(z)ajI(z) and
[TABLE]
which is a homogeneous polynomial in KQ[x0,…,xn]. By definition of the proximity function and Weil function, we have
[TABLE]
for j=1,…,q.
For a fixed point z∈Cm∖∪i=1qQ~i(f~)−1({0,∞}). We may assume that there exists a renumbering {1,…,q} such that
[TABLE]
By Lemma 2.2, we have maxj∈{1,…,N+1}∣Q~j(z)(f~)(z)∣=∣Q~N+1(z)(f~)(z)∣≥h∥f~∥d for some h∈Cf, i. e. ,
[TABLE]
Hence,
[TABLE]
Let KQ be an arbitrary field over Cm generated by a set of meromorphic function on Cm. Let V be a sub-variety in Pn(C) of dimension ℓ defined by the homogenous ideal I(V)⊂C[x0,⋯,xn]. Denote by IKQ(V) the ideal in KQ[x0,⋯,xn] generated by I(V).
Since f:Cm→V⊂Pn(C) is algebraically nondegenerate over KQ, there is no homogeneous polynomial P∈KQ[x0,…,xn]/IKQ(V) such that P(f0,…,fn)≡0.
For a positive integer L, let KQ[x0,…,xn]L be the vector space of homogeneous polynomials of degree L, and let IKQ(V)L:=IKQ(V)∩KQ[x0,…,xn]L. Set VL:=KQ[x0,…,xn]L/IKQ(V)L, denote by [g] the projection of g in VL. We have the following basic fact from the theory of Hilbert polynomials (e.g. see [15]):
Lemma 3.1**.**
M:=dimKQVL=ℓ!ΔLℓ+ρ(L), where ρ(L) is an O(Lℓ−1) function depending on the variety V. Moreover, there exists an integer L0 such that ρ(L) is a polynomial function of L for L>L0.
Let a be an arbitrary point in Cm such that all coefficients of P1,…,Ps are holomorphic at
a, denote by I(V(a)) the homogeneous ideal in C[x0,…,xn] generated by P1(a),…,Ps(a), let V(a) be the variety in V(a)⊂Pn(C) defined by I(V(a)), then we have
Lemma 3.2**.**
[3, 8, 17]**
dimV(a)=ℓ, for all a∈C excluding a discrete subset.
Next, we prove the following lemma concerning on the hypersurfaces located in N-subgeneral position with index κ, which plays the role in this paper. The method of it is originally from Quang [8, 9].
Lemma 3.3**.**
Let Q~1,…,Q~N+1 be homogeneous polynomials in KQ[x0,…,xn] of the same degree d ≥ 1, in (weakly) N-subgeneral position with index κ in V. For each point a ∈ Cm satisfying the following conditions:
(i) the coefficients of Q~1,…,Q~N+1 are holomorphic at a,
(ii) Q~1(a),…,Q~N+1(a) have no non-trivial common zeros,
(iii) dimV(a)=ℓ,
then there exist homogeneous polynomials
P~1(a)=Q~1(a),…,P~κ(a)=Q~κ(a), P~κ+1(a),…,P~ℓ+1(a) ∈ C[x0,…,xn] with
[TABLE]
such that
[TABLE]
Proof.
We assume that Q~i (1≤i≤N+1) has the following form
[TABLE]
By the definition of the N-subgeneral position, there exists a point a∈C such that the following system of equations
[TABLE]
has only trivial solution (0,…,0). We may assume that Q~i(a)≡0 for all 1≤i≤N+1.
For each homogeneous polynomial Q~∈C[x0,…,xn], we denote by D the fixed hypersurface in Pn(C) defined by Q~, i.e.,
[TABLE]
Setting P~1(a)=Q~1(a),…,P~κ(a)=Q~κ(a), we see that
[TABLE]
where dim∅ = -∞.
And for any κ moving hypersurfaces, we have
[TABLE]
(On the one hand, it is obvious dim(⋂j=1κDj(a)∩V)≥ℓ−κ; on the other hand, according to the definition of N-subgeneral position with index κ, we have dim(⋂j=1κDj(a)∩V)≤ℓ−κ).
Step 1. We will construct P~κ+1 as follows. For each irreducible componet Γ of dimension ℓ−κ of (⋂i=1κP~i(a)∩V(a)), we put
[TABLE]
By definition, V1Γ is a subspace of CN−ℓ+1. Since
[TABLE]
there exists i∈{κ+1,…,N−ℓ+κ+1} such that Γ⊂Di(a). This implies that V1Γ is a proper subspace of CN−ℓ+1. Since the set of irreducible components of dimension ℓ−κ of (⋂i=1κP~i(a)∩V(a)) is at most countable, we have
[TABLE]
Hence, there exists (c1(κ+1),…,c1(N−ℓ+κ+1))∈CN−ℓ+1 such that
Γ⊂P~κ+1(a), where P~κ+1=∑j=κ+1N−ℓ+κ+1c1jQ~j, for all irreducible components of dimension ℓ−κ of (⋂i=1κP~i(a)∩V(a)). This clearly implies that
[TABLE]
Step 2. We will construct Pκ+2 as follows. For each irreducible componet Γ′ of dimension ℓ−κ−1 of (⋂i=1κ+1P~i(a)∩V(a)), we put
[TABLE]
Then V2Γ′ is a subspace of CN−ℓ+2. Since dim(⋂i=1N−ℓ+κ+2Di(a)∩V(a))≤ℓ−κ−2, there exists i∈{κ+1,…,N−ℓ+κ+2} such that Γ′⊂Di(a). This implies that V2Γ′ is a proper subspace of CN−ℓ+2. Since the set of irreducible components of dimension ℓ−κ−1 of (⋂i=1κ+1P~i(a)∩V(a)) is at most countable, we also have
[TABLE]
Hence, there exists (c2(κ+1),…,c2(N−ℓ+κ+2))∈CN−ℓ+2 such that Γ′⊂P~κ+2(a),
where P~κ+2=∑j=κ+1N−ℓ+κ+2c2jQ~j, for all irreducible components of dimension ℓ−κ−1 of (⋂i=1κ+1P~i(a)∩V(a)). This clearly implies that
[TABLE]
Repeat again the above steps, after (ℓ+1−κ)-th step we get the hypersurface P~κ+1(a),…,P~ℓ+1(a) satisfying that
[TABLE]
where t=κ+1,…,ℓ+1.
In particular, (⋂j=1ℓ+1P~j(a)∩V(a))=∅. This yields that P~1(a),…,P~ℓ+1(a) are in general position. We complete the proof of the lemma.∎
Since there are only finitely many choice of N+1 polynomials from Q~1,…,Q~q, the total number of such P~j′s is finite, so there exists a constant C>0, for t=κ+1,…,ℓ and all z∈Cm (excluding all zeros and poles of all Q~j(f)), by Lemma 3.3 we can construct P~1=Q~1, …, P~κ=Q~κ, P~κ+1, …, P~ℓ+1 from Q~1,…,Q~N+1 such that
[TABLE]
for κ+1≤t≤ℓ, and thus,
[TABLE]
Combing the above inequality with (5), we have
[TABLE]
This gives that
if N−ℓ≤κ, we have
[TABLE]
and if N−ℓ≥κ, we get
[TABLE]
where
h′′′∈Cf. Hence, by (3) and (3), we get
[TABLE]
where h∗=max{h′′,h′′′}∈Cf.
Fix a basis {[ϕ1],…,[ϕM]} of VL with [ϕ1],…,[ϕM]∈KQ[x0,…,xn], and let
[TABLE]
Since f~ satisfies P(f~)≡0 for all homogeneous polynomials P∈KQ[x0,…,xn]/ IKQ(V), F is linearly nondegenerate over KQ. We have
[TABLE]
For every positive integer L divided by d, we use the following filtration of the vector space VL with respect to P~1(z),…,P~ℓ(z). This is a generalization of Corvaja-Zannier s filtration [1], see in the two references [10, 2, 17].
Arrange, by the lexicographic order, the ℓ-tuples i=(i1,…,iℓ) of non-negative integers and set ∥i∥=∑jij.
Definition 3.4**.**
[10, 2, 17]**(i) For each i∈Z≥0ℓ and non-negative integer L with L≥d∥i∥, denote by ILi the subspace of KQ[x0,…,xn]L−d∥i∥ consisting of all γ∈KQ[x0,…,xn]L−d∥i∥ such that
[TABLE]
*(or[P~1(z)i1⋯P~ℓ(z)iℓγ]=[∑e=(e1,…,eℓ)>iP~1(z)e1⋯P~ℓ(z)eℓγe] on VL)
for some γe∈ KQ[x0,…,xn]L−d∥e∥.
(ii) Denote by Ii the homogeneous ideal in KQ[x0,…,xn] generated by ⋃L≥d∥i∥ILi.*
Remark 3.5**.**
[10, 2, 17]** From this definition, we have the following properties.
(i). (IKQ(V),P~1(z)⋯P~ℓ(z))L−d∥i∥⊂ILi⊂KQ[x0,…,xn]L−d∥i∥, where we denote by
(IKQ(V),P~1(z)⋯P~ℓ(z)) the ideal in KQ[x0,…,xn] generated by IKQ(V)∪{P~1(z)⋯P~ℓ(z)}.
(ii). Ii∩KQ[x0,…,xn]L−d∥i∥=ILi.
(iii). IiKQ[x0,…,xn] is a graded module over KQ[x0,…,xn].
(iv). If i1−i2:=(i1,1−i2,1,…,i1,ℓ−i2,ℓ)∈Z≥0ℓ, then ILi2⊂IL+d∥i1∥−d∥i2∥i1. Hence Ii2⊂Ii1.
Lemma 3.6**.**
[10, 2, 17]**
{Ii∣i∈Z≥0ℓ} is finite set.
Denote by
[TABLE]
Lemma 3.7**.**
[10, 2, 17]**
(i). There exists a positive integer L0 such that, for each i∈Z≥0ℓ, ΔLi is independent of L for all L satisfying L−d∥i∥>L0.
(ii). There is an integer Δˉ such that ΔLi≤Δˉ for all i∈Z≥0ℓ and L satisfying L−d∥i∥>0.
Set Δ0:=mini∈Z≥0ℓΔi=Δi0 for some i0∈Z≥0ℓ.
Remark 3.8**.**
[10, 2, 17]**
By (iv) of Remark 3.5, if i−i0∈Z≥0ℓ, then Δi≤Δi0.
Now, for an integer L big enough, divisible by d, we construct the following filtration of VL with respect to {P~1(z)⋯P~ℓ(z)}.
Denote by τL the set of i∈Z≥0ℓ, with L−d∥i∥>0. arranged by the lexicographic order.
Define the spaces Wi=WL,i by
[TABLE]
Plainly W(0,…,0)=KQ[x0,…,xn]L and Wi⊃Wi′ if i′>i, so {Wi} is a filtration of KQ[x0,…,xn]L. Set Wi∗={[g]∈VL∣g∈Wi}. Hence,{Wi∗} is a filtration of VL.
Lemma 3.9**.**
[10, 2, 17]**
Suppose that i′ follows i in the lexicographic order, then
[TABLE]
Combining with the notation (10), we have
[TABLE]
Set
[TABLE]
We have the following properties.
Lemma 3.10**.**
[10, 2, 17]**
(i). Δ0=Δi for all i∈τL0.
(ii). ♯τL0=dℓ1ℓ!Lℓ+O(Lℓ−1).
(iii). ΔLi=Δdℓ for all i∈τL0.
We can choose a basis B={[ψ1],…,[ψM]} of VL with respect to the above filtration. Let [ψs] be an element of the basis, which lies in Wi∗/Wi′∗, we may write ψs=P~1(z)e1⋯P~ℓ(z)eℓγ, where γ∈KQ[x0,…,xn]L−d∥i∥. For every 1≤j≤ℓ, we have
[TABLE]
(The proof of (11) can be seen in [10, the equality (3.6)]). Hence, by (11) and the definition of the Weil function, we obtain
[TABLE]
where h∗∗∈Cf. The basis [ψ1],…,[ψM] can be written as linear forms L1,…,LM (over KQ) in the basis [ϕ1],…,[ϕM] and ψs(f~)=Ls(f~). Since there are only finitely many choices of Q~1(z),…,Q~(N+1)(z), the collection of all possible linear forms Ls(1≤s≤M) is a finite set, and denote it by L:={Lμ}μ=1Λ (Λ<+∞). It is easy to see that KL⊂KQ.
Lemma 3.11**.**
(Product to the sum estimate, see [11]) Let H1,…,Hq be hyperplanes in Pn(C) located in general position. Denote by T the set of all injective maps μ:{0,1,…,n}→{1,…,q}. Then
[TABLE]
holds for all r outside a set with finite Lebesgue measure.
By (3), (12) and Lemma 3.11, take integration on the sphere of radius r, we have
[TABLE]
for all r outside a set with finite Lebesgue measure,
where the set K ranges over all subset of {1,…,Λ} such that the linear forms {Lj}j∈K are linearly independent.
By Theorem 2.5, we have, for any ϵ>0,
[TABLE]
holds for all r outside a set E with finite Lebesgue measure.
Taking ε=21 in (14) and (13), and (9), we obtain
[TABLE]
holds for all r∈E, where W is the Wronskian of F1,…,FM.
Take L large enough such that ϵ<(max{1,min{N−ℓ,κ}}N−ℓ+1)o(1), where ϵ>0 is any given in the theorem. Then we have
[TABLE]
holds for all r∈E.
And by the first main theorem, (15) can be writen
[TABLE]
Secondly, for the general case whenever all Qj may not have the same degree. Then consider Qjdjd instead of Qj. We have
Nf(r,Qj)=ddjNf(r,Qjdjd). Then the theorem is proved immediately.
4. Proof of Theorem 1.5
Replacing Qi by Qid/di if necessary with the note that
[TABLE]
we may assume that all hypersurfaces Qi(1≤i≤q) are of the same degree d. We may also assume that q>(max{1,min{N−n,κ}}N−n+1)(n+1).
Consider a reduced representation f~=(f0,…,fn):C→Cn+1 of f. We also note that
[TABLE]
Then without loss of generality we may assume that Qi∈Kf[x0,…,xn].
We set
[TABLE]
For each I=(i1,…,iN+1)∈I, we denote by PI1,…,PI(n+1) the moving hypersurfaces obtained in Lemma 3.3 with respect to the family of moving hypersurfaces {Qi1,…,QiN+1}. It is easy to see that there exists a positive function h∈Cf such that
[TABLE]
for all I∈I and ω=(ω0,…,ωn)∈Cn+1.
For a fixed point z∈Cm∖∪i=1qQi(f~)−1({0,∞}). We may assume that such that
[TABLE]
Let I=(i1,…,iN+1). Since PI1,…,PI(n+1) are in weakly general position, there exist functions g0,g∈Cf, which may be chosen independent of I and z, such that
[TABLE]
Therefore, we have
[TABLE]
where h1=gq−N(z)hn−κ(z), I=(i1,…,iN+1) and ζ is a function in Cf, which is chosen common for all I∈I, such that
[TABLE]
We will consider if N−n≤κ, we have by the inequality above,
[TABLE]
where h2=ζ(z)2n−Nh1∈Cf, however if N−n≥κ, we get
[TABLE]
where h3=h1ζκ(n−κ)(N−n)(z)∈Cf.
Thus by (4) and (4),we get
[TABLE]
where h∗=max{h2,h3}∈Cf.
Hence, by taking logarithms in the tow sides of (19),we can obtain
[TABLE]
Now, for each non-negative integer L, we denote by VL the vector space (over KQ) consisting of all homogeneous polynomials of degree L in KQ[x0,…,xn] and the zero polynomial. Denote by (PI1,…,PIn) the ideal in KQ[x0,…,xn] generated by PI1,…,PIn.
Lemma 4.1**.**
(See [3], Proposition 3.3).
Let {Pi}i=1q(q≥n+1) be a set of homogeneous polynomials of common degree d≥1 in Kf[x0,…,xn] in weakly general position. Then for any nonnegative integer L and for any J:={j1,…,jn}⊂{1,…,q}, the dimension of the vector space (Pj1,…,Pjn)∩VLVL is equal to the number of n-tuples (s1,…,sn)∈N0n such that s1+⋯+sn≤L and 0≤s1,…,sn≤d−1. In particular, for all L≥n(d−1), we have
[TABLE]
Now, for each positive integer L big enough, divided by d, and i=(i1,…,in)∈N0n with σ(i)=∑j=1nij≤dL, we set
[TABLE]
It is clear that WL,(0,…,0)=VL and WL,i⊃WL,i′ if i<i′, so {WL,i} is a filtration of VL. For the proof of the above lemma, refer to [8].
Lemma 4.2**.**
Let i=(i1,…,in),i′=(i1′,…,in′)∈N0n. Suppose that i′ follows i in the lexicographic ordering and dσ(i)<L. Then
[TABLE]
This lemma yields that
[TABLE]
Fix a number L large enough (chosen later). Set u=uL:=dimVL=(nL+n). We assume that
[TABLE]
where WL,is+1 follows WL,is in the ordering and iK=(dL,0,…,0). It is easy to see that K is the number of n -tuples (i1,…,in) with ij≥0 and i1+⋯+in≤dL. Then we have
[TABLE]
For each k∈{1,…,K−1} we set mkI=dimWL,ik+1WL,ik, and set mKI=1. Then by Lemma 4.1, mkI does not depends on {PI1,…,PIn} and k, but only on σ(ik). Hence, we set mk:=mkI. We also note that by Lemma 4.1
[TABLE]
for all k with L−dσ(ik)≥n(d−1) (it is equivalent to σ(ik)≤dL−n).
From the above filtration, we may choose a basis {ψ1I,⋯,ψuI} of
VL such that
[TABLE]
is a basis of WL,is. For each k∈{1,…,K} and l∈{u−(mk+⋯+mk)+1,…,u− (mk+1+⋯+mK)}, we may write
[TABLE]
We may choose hl to be a monomial.
We have the following estimates: Firstly, we see that
[TABLE]
Note that, by the symmetry (i1,…,in)→(iσ(1),…,iσ(n)) with σ∈S(n),∑k∣σ(ik)=lisk does not depend on s. We set
[TABLE]
Then we have
[TABLE]
where cl∈Cf, which does not depend on f and z. Taking the product on both sides of the above inequalities over all l and then taking logarithms, we obtain
[TABLE]
where cI=∏l=1ucl∈Cf. By (22), it gives
[TABLE]
i.e.,
[TABLE]
set c0=h∗∏I(1+cI(1+max{1,min{N−n,κ}}N−n)/a)∈Cf.
Combining (23) with (4), we obtain that
[TABLE]
We now write
[TABLE]
where IL is the set of all (n+1)-tuples J=(i0,…,in) with Σs=0njs=L,xJ=x0j0⋯xnjn and l∈{1,…,u}. For each l, we fix an index JlI∈J such that clJlII≡0. Define
[TABLE]
Set Φ={μlJI;I⊂{1,…,q},♯I=n,1≤l≤u,J∈IL}. Note that 1∈Φ. Let B=♯Φ. We see that B≤u(nq)((nL+n)−1)=(nq)((nL+n)−1)(nL+n). For each positive integer l, we denote by L(Φ(l)) the linear span over C of the set
[TABLE]
It is easy to see that
[TABLE]
We may choose a positive integer p such that
[TABLE]
and
[TABLE]
Indeed, if dimL(Φ(p))dimL(Φ(p+1))>1+3(n+1)(1+max{1,min{N−n,κ}}N−n)ϵ for all p≤p0, we have
[TABLE]
Therefore, we have
[TABLE]
This is a contradiction.
We fix a positive integer p satisfying the above condition. Put s=dimL(Φ(p)) and t=dimL(Φ(p+1)). Let b1,…,bt be an C-basis of L(Φ(p+1)) such that b1,…,bs be a C-basis of L(Φ(p)).
For each l∈1,…,u, we set
[TABLE]
For each J∈IL, we consider homogeneous polynomials ϕJ(x0,…,xn)=xJ. Let F be a meromorphic mapping of Cm into Ptu−1(C) with a reduced representation F~=(hbiϕJ(f~))1≤i≤t,J∈IL, where h is a nonzero meromorphic function on Cm. We see that
[TABLE]
Since f is assumed to be algebraically nondegenerate over KQ, F is linearly nondegenerate over C. We see that there exist nonzero functions c1,c2∈Cf such that
[TABLE]
For each l∈1,…,u,1≤i≤s, we consider the linear form LilI in xJ such that
[TABLE]
Since f is algebraically nondegenerate over KQ, it is easy to see that {biψ~lI(f~);1≤i≤s,1≤l≤M} is linearly independent over C, and so is {LilI(F~);1≤i≤s,1≤l≤u}. This yields that {LilI;1≤i≤s,1≤l≤u} is linearly independent over C.
For every point z which is not neither zero nor pole of any hbiψlI(f~), we also see that
[TABLE]
where c3,c4 are nonzero functions in Cf, not depend on f and I, but on {Qi}i=1q. Combining this inequality and (24), we obtain that
[TABLE]
for all z outside an analytic subset of Cm.
Since F~ is linearly nondegenerate over C, according to Proposition 2.4, there exists an admissible set α=(αiJ)1≤i≤t,J∈IL with αiJ∈Z+m,αiJ≤tu−1, such that
[TABLE]
By Theorem 2.5, we have
[TABLE]
Integrating both sides of (25)and using (4), we obtain that
[TABLE]
We can estimate the following quantity where by using the method of S.D.Quang (to see [8]),
[TABLE]
thus we can get
[TABLE]
From this inequality and (27) with a note that TF(r)=LTf(r)+o(Tf(r)), we have
[TABLE]
Now we give some estimates for A,tands. For each Ik=(i1k,…,ink) with σ(ik)≤dL−n, we set
[TABLE]
Since the number of nonnegative integer p-tuples with summation ≤Iis equal to the number of nonnegative integer (p+1)-tuples with summation exactly equal to I∈Z, which is (nI+n), and since the sum below is independent of s, we have
[TABLE]
Now, for every positive number x∈[0,(n+1)21], we have
[TABLE]
We chose L=(n+1)d+2(1+max{1,κN−n})(n+1)3I(ϵ−1)d. Then L is divisible by d and we have
[TABLE]
Therefore, using (4)and (30)we have
[TABLE]
Then we have
[TABLE]
Combining (4)and (4), we get
[TABLE]
Here we note that:
[TABLE]
[TABLE]
[TABLE]
By these estimates and by (32), we obtain
[TABLE]
The theorem is proved.
Acknowledgement. The authors are very grateful to Prof. Qiming Yan for pointing out a hard to find but serious gap in the original version (arXiv:1908.05844v1) and giving many valuable suggestions, and would also thank to Dr. Nguyen Van Thin for giving some comments to the first version (arXiv:1908.05844v1).