Über die Charakterisierung von ...(X) durch eien optimalen Satz vom Korovkintyp.
Über die Korovkinhülle von Teilmengen in lokalkonvexen Vektorverbänden.
Über Korovkin-Sätze in lokalkonvexen Vektorverbänden.
Ultrasymmetric sequence spaces in approximation theory.
Let φ(t) be a positive increasing function and let Ê be an arbitrary sequence space, rearrangement-invariant with respect to the atomic measure µ(n) = 1/n. Let {an*} mean the decreasing rearrangement of a sequence {|an|}. A sequence space lφ,E with symmetric (quasi)norm || {φ(n)an*} ||Ê is called ultrasymmetric, because it is not only intermediate but also interpolation between the corresponding Lorentz and Marcinkiewicz spaces Λφ and Mφ. We study properties of the spaces lφ,E for all admissible...
Un procédé itératif avec l'opérateur modifie et les problèmes d'approximation
Unicity of Best One-Sided L1-Approximations
Uniform approximation by minimum norm interpolation.
Uniform approximation by real functions
Uniform extension of linear functionals
Uniqueness of minimal projections onto two-dimensional subspaces
We prove that minimal projections from (1 < p < ∞) onto any two-dimensional subspace are unique. This result complements the theorems of W. Odyniec ([OL, Theorem I.1.3], [O3]). We also investigate the minimal number of norming points for such projections.
Universal approximations of certain functionals in Banach spaces
Universal simultaneous approximations of the coefficient functionals
Upper and lower estimates for Schauder frames and atomic decompositions
We prove that a Schauder frame for any separable Banach space is shrinking if and only if it has an associated space with a shrinking basis, and that a Schauder frame for any separable Banach space is shrinking and boundedly complete if and only if it has a reflexive associated space. To obtain these results, we prove that the upper and lower estimate theorems for finite-dimensional decompositions of Banach spaces can be extended and modified to Schauder frames. We show as well that if a separable...