Equivalent norms in spaces of functions of fractional smoothness on an arbitrary domain.
The paper deals with spaces of type \(B^s_{pq} (G)\) and \(F^s_{pq}(G)\) for arbitrary domains \(G \subset \mathbb{R}^n\) where \(s>0\), \(1\leq p,q \leq \infty\). The author proves that these spaces can be equivalently normed either in terms of means of differences or in terms of best polynomial approximations.
scientific article; zbMATH DE number 2121043