THE SHARP JACKSON INEQUALITY FOR L~2-APPROXIMATION ON THE PERIODIC CYLINDER

We consider Jackson inequality in L~2(B~d × T,W_(κ,μ)~B(x)),where the weight function W_(κ,μ)~B(x) is defined on the ball B~d and related to reflection group,and obtain the sharp Jackson inequality E_(n- 1,m-1)(f)2 ≤k_(n,m)(r,r)ω_r(f,t)_2,T ≥ 2τ_(n,λ),where τ_(n,λ) is the first positive zero of the Gegenbauer cosine polynomial C_n~λ(cosθ)(n ∈ N).     

A CLASS OF COMPACTLY SUPPORTED ORTHOGONAL SYMMETRIC COMPLEX WAVELETS WITH DILATION FACTOR 3

When approximation order is an odd positive integer, a simple method is given to construct compactly supported orthogonal symmetric complex scaling function with dilation factor 3. Two corresponding orthogonal wavelets, one is symmetric and the other is antisymmetric about origin, are constructed explicitly. Additionally, when approximation order is an even integer 2, we also give a method to construct compactly supported orthogonal symmetric complex wavelets. In the end, there are several examples that illustrate the corresponding results.     

On the Approximation of an Analytic Function Represented by Laplace-Stieltjes Transformation

In the present paper,we have considered the approximation of analytic functions represented by Laplace-Stieltjes transformations using sequence of definite integrals. We have characterized their order and type in terms of the rate of decrease of E_n(F,β) where E_n(F,β) is the error in approximating of the function F(s) by definite integral polynomials in the half plane Res≤βα.     

BEST APPROXIMATION FOR WEIERSTRASS TRANSFORM CONNECTED WITH SPHERICAL MEAN OPERATOR

Using reproducing kernels for Hilbert spaces,we give best approximation for Weierstrass transform associated with spherical mean operator.Also,estimates of extremal functions are checked.     

UNIFORM APPROXIMATION OF ENTIRE FUNCTIONS OF SLOW GROWTH ON COMPACT SETS

In the present paper,we study the polynomial approximation of entire functions of several complex variables.The characterizations of generalized order and generalized type of entire functions of slow growth are obtained in terms of approximation and interpolation errors.     

非对角二元二次函数逼近的存在性和局部性质

§ 1　IntroductionThis paper is concerned with the properties of the simple off-diagonal bivariatequadratic Hermite-Padé approximation.Thisapproximation may be defined asfollows(see,for example,[1 ] ) .Let f(x,y) be a bivariate function,analytic in some neighbourhood of the origin(0 ,0 ) ,whose series expansion about the origin is known.Let a0 (x,y) ,a1 (x,y) ,a2 (x,y) bebivariate polynomials,a0 (x,y) = ki,j=0 a(0 )ij xiyj,a1 (x,y) = ni,j=0 a(1 )ij xiyj,a2 (x,y) = mi,j=0 a(2 )ij xiyj,such th…     

On the order of approximation for the rational interpolation to |x|

The order of approximation for Newman-type rational interpolation to |x| is studied in this paper.For general set of nodes, the extremum of approximation error and the order of the best uniform approximation are estimated. The result illustrates the general quality of approximation in a different way. For the special case where the interpolation nodes are xi=(i/n)r(i=1,2, … ,n;r＞0), it is proved that the exact order of approximation is O(1/n), O(1/nlogn) and O(1/nr), respectively, corresponding to 0＜r＜1, r=1 and r＞1.     

MNTZ RATIONAL APPROXIMATION FOR SPECIAL FUNCTION CLASSES IN Ba[0,1] SPACES

In this paper,we research the Mntz rational approximation of two kinds of special function classes,and give the corresponding estimates of approximation rates of these classes.     

广义Besov函数类$B_{p,\theta}^\Omega$上的三角宽度及最佳$N$-项逼近

In this paper, we determine the estimates exact in order for the trigonometric widths and the best n-term trigonometric approximations of the generalized classes of periodic functions B^Ωpθ in the space Lq for some values of parameters p, q.     

角域内代数体函数的唯一性定理

Let W (z) and M(z) be v-valued and k-valued algebroidal functions respectively,(θ) be a b-cluster line of order ∞ (or ρ(r)) of W (z) (or M(z)).It is shown that W (z) ≡ M(z) provided E(a j ,W (z)) = E(a j ,M(z)) (j = 1,...,2v + 2k + 1) holds in the angular domain Ω(θ- δ,θ + δ),where b,a j (j = 1,...,2v + 2k + 1) are complex constants.The same results are obtained for the case that (θ) is a Borel direction of order ∞ (or ρ(r)) of W (z) (or M(z)).     

GENERALIZED HILBERT OPERATOR AND FEJR-RIESZ TYPE INEQUALITIES ON THE POLYDISC

Let f be a holomorphic function on the unit polydisc Dn,with Taylor expansion f(z) = ∞ |k|=0 akzk ≡∞ (k1+···+kn=0) (ak1,···,kn zk1 1znkn)where k = (k1, , kn) ∈ Z+n. The authors define generalized Hilbert operator on Dn by Hγ,n(f)(z) = ∞ |k|=0 i1,···,in≥0 ai1,···,in n j=1 Γ(γj + kj + 1)Γ(kj + ij + 1) Γ(kj + 1)Γ(kj + ij + γj + 2) zk,where γ∈ Cn, such that R γj > -1, j = 1, 2, , n. An upper bound for the norm of the operator on Hardy spaces Hp(Dn) is found. The authors also present a Fejér-Riesz type inequalit...     

关于等角写像的边界性质

<正> 一个函数f(x)在[a,b]上定义,我们记 f(x)∈H_x~a(0<α≤1),表示f(x)是满足α级 Lipschitz-H(?)lder 条件的函数,下标表示所涉及的自变量,而f(x)∈H_x~(1-0表示f(x)之连续模满足条件ω(δ,f)≤kδ|log δ|,(k为常数).我们记(?)是其连续模满足条件     

Cn中单位球上$mu$-Bloch函数的等价刻画

设$\mu$是$[0,1)$上的正规函数, 给出了${\bf C}^{\it n}$中单位球$B$上$\mu$-Bloch空间$\beta_{\mu}$中函数的几种刻画. 证明了下列条件是等价的: (1) $f\in \beta_{\mu}$; \ (2) $f\in H(B)$且函数$\mu(|z|)(1-|z|^{2})^{\gamma-1}R^{\alpha,\gamma}f(z)$ 在$B$上有界; (3) $f\in H(B)$ 且函数${\mu(|z|)(1-|z|^{2})^{M_{1}-1}\frac{\partial^{M_{1}} f}{\partial z^{m}}(z)}$ 在$B$上有界, 其中$|m|=M_{1}$; (4) $f\in H(B)$ 且函数${\mu(|z|)(1-|z|^{2})^{M_{2}-1}R^{(M_{2})}f(z)}$ 在$B$上有界.     

Some Sharpening and Generalizations of a Result of T. J. Rivlin

Let p(z)=a_0+a_1z+a_2z~2+a_3z~3+···+a_nz~n be a polynomial of degree n.Rivlin[12]proved that if p(z)≠0 in the unit disk,then for 0r≤1,max|z|=r|p(z)|≥((r+1)/2)~nmax|p(z)||z|=1.In this paper,we prove a sharpening and generalization of this result and show by means of examples that for some polynomials our result can significantly improve the bound obtained by the Rivlin’s Theorem.     

积分算子作用下的亚纯多叶函数

令∑_p表示形如f(z)=z~(-p)+∑m=1∞(p∈N={1,2,3…})且在去心单位开圆盘D=U\{0}={z∶z∈C且0|z|1}上解析的亚纯多叶函数类.利用一个作用在∑_p上的乘积算子定义了几个新的亚纯函数的子类,并考虑这些函数类在积分算子作用下的性质.     

关于Neumann-Bessel级数的线性组合算子

In this paper we construct a new operator Hn,r（N,B） （f; z） by means of the partial sums S（N,S） （f; z） of Neumann-Bessel series. The operator converges uniformly to any fixed continuous function f（z） on the unit circle ｜ z ｜= 1 and has the best approximation order for f（z） on ｜ z ｜= 1.     

一类算子值解析函数族的极值点

设 H 是一个Hilbert空间. B(H) 表示所有H 到 H 的有界线性算子构成的Banach空间. 设 T= {f(z): f(z)=zI-∑^∞_n=2 zⁿA_n 在单位圆盘|z|<1上解析, 其中系数A_n是 H 到 H 的紧正Hermitian算子, I 表示 H 上的恒等算子, ∑^∞_n=2 n(A_n x, x) ≤1 对所有x ∈H, ∣|x∣∣=1 成立. 该文研究了函数族 T 的极值点.     

面积平均p叶函数的最小模估计及其应用

假设,在单位圆盘△={z:|z|<1}内是面积平均p叶函数.关于|f'/f|2的平均增长,Hayman和Duren等对其进行了详细的研究.注意到,这种增长涉及到f(z)的最小模m(r)=min|z|=r|f(z)|.本文首先估计m(r),然后给出一些相关的应用,其中包括|f'/f|2的平均增长估计,|f(eiθ)|-λ的可积性以及一个新的Bazilevic定理,这个新的定理涉及到f的最大增长方向和最小增长方向.我们得到的某些结果是不可改进的.     

Two Kinds of Boundary Value Problems for the First Order Systems of Nonlinear Elliptic Partial Differential Equations

In this paper we establish the esxistence and uniqueness theorems of a solution of the problem P(|z|=1,Re[z^-nw_z]=0) and H(|z|=1,Re[z^-nw]=0) for the nonlinear system (A):w_{\bar z}=g(z,w,w_z),|g(z,w,w_z^1)-g(z,w,w_z^2)| \leq q_0|w_z^1-w_z^2|,q_0=const.<1,z \in G={|z|<1}.for the problem P,where w(z) \in C_\alpha^1(\bar G),let C_\alpha(g(z,w,t)-g(z,w_1,t_1),\bar G) \leq H_3C_\alpha(w-w_1,\bar G)+H_4C_\alpha(t-t_1,\bar G),H_3,H_4 and C_\alpha(g(z,0,0),\bar G)be the suitable small constants.For the problem H,where w(z) \inW_p^(1)(\bar G),p>2,let |g(z,w,0)| \leq A(z,w)|w|^m+B(z,w),m>1,A(z,w) \in L_p(\bar G) and ||B(z,w)||_{L_p(\bar G)} be the suitable small.     

Inequalities for the Polar Derivatives of a Polynomial

Let P(z) be a polynomial of degree n, having all its zeros in|z| ≤1In this paper, we estimate kth polar derivative of P(z) on|z|= 1 and thereby obtain compact generalizations of some known results which among other things yields a refinement of a result due to Paul Tura'n.