Uniform Approximation of Nonperiodic Functions Defined on the Entire Axis

Using the following notation: C is the space of continuous bounded functions f equipped with the norm , V is the set of functions f such that , the set E consists of fCV and possesses the following property:

The Properties of Functions and Approximation by Summation Rational Operators on the Real Axis

In the space $C(\mathbb{R})$ , we construct special summation operators of Jackson type with rational kernels and under a suitable choice of poles we obtain order estimates for deviations of these operators from functions belonging to certain classes.     

Estimate of the Order of Growth of a Class of Entire Functions on the Real Axis

For a class of entire functions we study the problem of estimation of the order of growth of functions on the real axis. This problem is important for the justification of the integral representation of bounded solutions to certain partial differential equations considered in other papers of the authors. In order to obtain an estimate of the order of growth of a function on the real axis, we use the method of differential equations. The method is based, on one hand, on the construction of a system of first-order ordinary differential equations whose solution is a vector function of traces of function and its derivatives on the real axis. On the other hand, under the respective change of variables in the system of equations, we obtain an estimate of the solution to the system of equations for a large positive values of the argument. The obtained estimate is non-trivial and shows the way a complex parameter of a power series affects the order of growth of a function.     

Approximation of Multivariate Functions with a Certain Mixed Smoothness by Entire Functions

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Approximation of Smooth Functions on the Semiaxis by Entire Functions of Bounded Half-Degree

In this paper, we study the pointwise approximation of functions defined on the real semiaxis and having an rth derivative bounded almost everywhere. The approximation is performed by means of entire functions of bounded half-degree, which were introduced by S. N. Bernstein. An asymptotically sharp estimate for pointwise approximation of this class of functions is obtained.     

用指数型整函数的最佳限制逼近

我们研究了由仅有实零点的代数多项式导出的微分算子确定的广义Sobolev类利用指数型整函数作为逼近工具的最佳限制逼近问题.利用Fourier变换和周期化等方法,得到在L_2(R)范数下的广义Sobolev光滑函数类的相对平均宽度和最佳限制逼近的精确常数,以及当0是这个代数多项式的一个至多2重的零点时,得到最佳限制逼近在L_1(R)范数和一致范数下的广义Sobolev类的精确到阶的结果.     

On the Approximation of Functions by Polynomials and Entire Functions of Exponential Type

Ukrainian Mathematical Journal - We present a brief survey of works in the approximation theory of functions known to the author and connected with V. K. Dzyadyk’s research works.     

Inverse Approximation Theorem on an Infinite Union of Segments

Let , where the and satisfy the following relations: and . Denote by B the class of all entire functions of exponential type bounded on the real axis. Under certain assumptions on the rate of approximation on E of a bounded function f by functions in B ( varies), we get some information about the smoothness of f. Bibliography: 4 titles.     

Uniform Approximation by Entire Functions That Are All Bounded on a Given Set

For two closed sets F and G in the complex plane C, G C , we solve the following problem Under what conditions on F and G can every function f , continuous on F and analytic in its interior, be uniformly approximated by entire functions, each of which is bounded on G ? February 7, 1995. Date revised: October 31, 1995.     

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.     

On Boundary Value Problems of Polyanalytic Functions on the Real Axis

In this article, we discuss the Riemann boundary value problems and the Hilbert boundary value problems of polyanalytic functions on the real axis, and both the explicit expressions of solutions and the conditions of solvability are obtained.     

整函数分担多项式的增长性的进一步估计

运用正规族理论将整函数分担多项式增长级的结果进一步精确化估计.同时举例说明的结果是有意义的.     

Correction to: Approximation by Interpolation Trigonometric Polynomials in Metrics of the Space Lp on the Classes of Periodic Entire Functions

Ukrainian Mathematical Journal - The title of the article should read: Approximation by Interpolation Trigonometric Polynomials in Metrics of the Space Lp on the Classes of Periodic Entire...     

On the Distribution of Alternation Points in Uniform Polynomial Approximation of Entire Functions

We consider the distribution of alternation points in best real polynomial approximation of a functionf∈C[−1, 1]. For entire functionsfwe look for structural properties of f that will imply asymptotic equidistribution of the corresponding alternation points.     

Approximation by Interpolation Trigonometric Polynomials in Metrics of the Space Lp on the Classes of Periodic Entire Functions*

Ukrainian Mathematical Journal - We establish asymptotic equalities for the least upper bounds of approximations by interpolation trigonometric polynomials with equidistant distribution of...