András Kroó

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×ØÖÖغ Let P d n denote the set of real algebraic polynomials of d variables and of total degree at most n. For a compact set K ⊂ Ê d set P K = sup x∈K |P (x)|. d−1 Ó. (Here, as usual, S d−1 stands for the Eucledean unit sphere in Ê d .) Furthermore, given a smooth curve Γ ⊂ Ê d , we denote by D T P the tangential derivative of P along Γ (T is the unit(More)
Let M be a closed linear subspace of a normed linear space X. For a given f ∈ X denote by P M f the set of best approximations to f from M. The operator P M is termed the metric projection onto M. In this paper we are interested in the stability of the metric projection P M relative to perturbations of the subspace M. We mainly consider the case where X = L(More)