Cebysev subspaces of C*-algebras.
Characterizations of elements of best approximation in non-Archimedean normed spaces
Characterizations of -predual spaces by centerable subsets
In this note, we prove that a real or complex Banach space is an -predual space if and only if every four-point subset of is centerable. The real case sharpens Rao’s result in [Chebyshev centers and centerable sets, Proc. Amer. Math. Soc. 130 (2002), no. 9, 2593–2598] and the complex case is closely related to the characterizations of -predual spaces by Lima [Complex Banach spaces whose duals are -spaces, Israel J. Math. 24 (1976), no. 1, 59–72].
Characterizations of periodic function spaces of Besov-Sobolev type via approximation processes and relations to the strong summability of Fourier series
Characterizations of random approximations
Some characterizations of random approximations are obtained in a locally convex space through duality theory.
Chebyshev centers, E-Chebyshev centers and the Hausdorff metric.
Chebyshev centers in hyperplanes of
We give a full characterization of the closed one-codimensional subspaces of , in which every bounded set has a Chebyshev center. It turns out that one can consider equivalently only finite sets (even only three-point sets) in our case, but not in general. Such hyperplanes are exactly those which are either proximinal or norm-one complemented.
Chebyshev Centres in Normed Spaces
Chebyshev optimal starting approximation by families with the weak betweenness property
Closure of Similarity Orbits of Hubert Space Operators. III.
Common fixed point and approximation results for noncommuting maps on locally convex spaces.
Common fixed point and invariant approximation results in certain metrizable topological vector spaces.
Common fixed point results and its applications to best approximation in ordered semi-convex structure.
Compact operators and approximation spaces
We investigate compact operators between approximation spaces, paying special attention to the limit case. Applications are given to embeddings between Besov spaces.
Compactness in approximation spaces
In this paper we give a characterization of the relatively compact subsets of the so-called approximation spaces. We treat some applications: (1) we obtain some convergence results in such spaces, and (2) we establish a condition for relative compactness of a set lying in a Besov space.
Comparative approximation in two topologies
Completeness and approximation
Complex Unconditional Metric Approximation Property for spaces
We study the Complex Unconditional Metric Approximation Property for translation invariant spaces of continuous functions on the circle group. We show that although some “tiny” (Sidon) sets do not have this property, there are “big” sets Λ for which has (ℂ-UMAP); though these sets are such that contains functions which are not continuous, we show that there is a linear invariant lifting from these spaces into the Baire class 1 functions.
Comportamiento asintótico de las diferenciales de una función.
Concertina-Loke Movements of the Error Curve in the Alternation Theorem.