On a problem of Dickmeis and Nessel concerning the approximation by Bernstein polynomials

Authors
Citation
L. Imhof, On a problem of Dickmeis and Nessel concerning the approximation by Bernstein polynomials, ST SCI M H, 35(1-2), 1999, pp. 151-154
Citations number
10
Categorie Soggetti
Mathematics
Journal title
STUDIA SCIENTIARUM MATHEMATICARUM HUNGARICA
ISSN journal
00816906 → ACNP
Volume
35
Issue
1-2
Year of publication
1999
Pages
151 - 154
Database
ISI
SICI code
0081-6906(1999)35:1-2<151:OAPODA>2.0.ZU;2-S
Abstract
For f is an element of C[0, 1] let B-n(f;x) denote the nth Bernstein polyno mial and omega*(f;t) the second modulus of smoothness. Continuing: the inve stigations by W. Dickmeis and R.J. Nessel it is shown that for each abstrac t modulus of continuity omega there exists a counterexample f(omega) is an element of C[0, 1] such that on the one hand omega*(f(omega); t) = O(omega( t)) and on the other hand lim sup(n-->infinity) \B-n(f(omega);x) - f(omega) (x)\/omega(x(1 - x)/n) greater than or equal to c > 0 simultaneously for al l x is an element of (0, 1). Furthermore, a pointwise lethargy assertion is established.