LOCAL AND GLOBAL APPROXIMATION THEOREMS FOR POSITIVE LINEAR-OPERATORS

Authors
FELTEN M
Citation
M. Felten, LOCAL AND GLOBAL APPROXIMATION THEOREMS FOR POSITIVE LINEAR-OPERATORS, Journal of approximation theory (Print), 94(3), 1998, pp. 396-419
Citations number
16
Categorie Soggetti
Mathematics,Mathematics
Journal title
Journal of approximation theory (Print) → ACNP
ISSN journal
00219045
Volume
94
Issue
3
Year of publication
1998
Pages
396 - 419
Database
ISI
SICI code
0021-9045(1998)94:3<396:LAGATF>2.0.ZU;2-A
Abstract
In this paper we bridge local and global approximation theorems for po sitive linear operators via Ditzian-Totik moduli omega(phi)(2)(f, delt a) of second order whereby the step-weights phi are functions whose sq uares are concave. Both direct and converse theorems are derived. In p articular we investigate the situation for exponential-type and Bernst ein-type operators. (C) 1998 Academic Press.