Abstract

In this paper we introduce a general class of integral operators that fix exponential functions, containing several recent modified operators of Gauss–Weierstrass, or Picard or moment type operators. Pointwise convergence theorems are studied, using a Korovkin-type theorem and a Voronovskaja-type formula is obtained.

Highlights

  • The classical Bohman–Korovkin theorem is one of the pivotal results of approximation theory and several convergence theorems known in literature employ this basic tool

  • It states that a sequence of positive linear operators Tnf acting on the set of the continuous functions over a compact interval of the real line converges to the identity operator only if it converges on a finite number of test functions which form a so-called Chebyshev system

  • If a sequence of operators Tnf is such that Tnφ = φ for some continuous function φ, to obtain the convergence appears very simple, if the functions φ belong to a Chebyshev system

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Summary

Introduction

The classical Bohman–Korovkin theorem (see [10,22,23]) is one of the pivotal results of approximation theory and several convergence theorems known in literature employ this basic tool It states that a sequence of positive linear operators Tnf acting on the set of the continuous functions over a compact interval of the real line converges to the identity operator only if it converges on a finite number of test functions which form a so-called Chebyshev system. A complete treatment of the Korovkin theorem can be found in the monographies [2,3] In this respect, if a sequence of operators Tnf is such that Tnφ = φ for some continuous function φ, to obtain the convergence appears very simple, if the functions φ belong to a Chebyshev system. That general approaches to convergence of integral operators was recently given in [9], and more recently in [20] and [25] in the frame of nonlinear operators

Basic Notations
The Class of Integral Operators
Pointwise and Uniform Convergence
Quantitative Estimates
An Asymptotic Formula
Examples
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