OPTIMAL AND NONOPTIMAL RATES OF APPROXIMATION FOR INTEGRATED SEMIGROUPS AND COSINE FUNCTIONS

Authors
CHANG JC SHAW SY
Citation
Jc. Chang et Sy. Shaw, OPTIMAL AND NONOPTIMAL RATES OF APPROXIMATION FOR INTEGRATED SEMIGROUPS AND COSINE FUNCTIONS, Journal of approximation theory, 90(2), 1997, pp. 200-223
Citations number
19
Categorie Soggetti
Mathematics, Pure",Mathematics
Journal title
Journal of approximation theory → ACNP
ISSN journal
00219045
Volume
90
Issue
2
Year of publication
1997
Pages
200 - 223
Database
ISI
SICI code
0021-9045(1997)90:2<200:OANROA>2.0.ZU;2-B
Abstract
For a general approximation process we formulate theorems concerning r ates of convergence, including theorems about saturation class, non-op timal rates. and sharpness of non-optimal convergence. The general res ults are then applied to n-times integrated semigroups and cosine func tions, yielding some new results about their approximation. as well as the convergence of their Cesaro and Abel means to the identity. (C) 1 997 Academic Press.