Approximation on simplices with respect to weighted Sobolev norms
Direct and inverse estimates for triangles and more generally for simplices were obtained by polynomial approximation with respect to Sobolev norms. For this polynomial approximation inequalities of Jackson and Bernstein type were derived. Sharp estimates were obtained from a decomposition into orthogonal subspaces of different operators. These operators already served for the treatment of Bernstein-Durrmeyer operators [\textit{Th. Sauer}, Result. Math. 26, No. 1-2, 99-130 (1994; Zbl 0817.41014)].
scientific article; zbMATH DE number 1443209