Products of parametric extensions: Refined estimates (Q2754511)

The main purpose of the paper is to obtain a unified theory for dealing with pointwise estimates for approximation processes in the space \(C(\times_{\delta=1}^dI_\delta)\), where \(I_\delta\) are compact intervals of the real line. There have been results of this type for norm estimates with the uniform norm. These have been obtained by Hausmann and Pottinger in a series of articles in the 1970's. For instance, the results allow extension of estimates on the degree of approximation of positive approximation operators on a finite interval to operators on \(C(\times_{\delta=1}^dI_\delta)\).NEWLINENEWLINEFor the entire collection see [Zbl 0956.00027].