DOI

We investigate the possibility of approximating a function on a compact set K of the complex plane in such a way that the rate of approximation is almost optimal on K, and the rate inside the interior of K is faster than on the whole of K. We show that if K has an external angle smaller than π at some point zo∈δK, then geometric convergence inside K is possible only for functions that are analytic at zo. We also consider the possibility of approximation rates of the form exp(-cnβ), for approximation inside K, where β is related to the largest external angle of K. It is also shown that no matter how slowly the sequence {γn} tends to zero, there is a K and a Lip β, β<1, function f such that approximation inside K cannot have order {γn}.

Язык оригиналаанглийский
Страницы (с-по)145-152
Число страниц8
ЖурналConstructive Approximation
Том10
Номер выпуска2
DOI
СостояниеОпубликовано - июн 1994
Опубликовано для внешнего пользованияДа

    Предметные области Scopus

  • Анализ
  • Математика (все)
  • Вычислительная математика

ID: 86661982