Good approximation in metrizable locally convex spaces involving a set of nonlinear functionals
Greediness of the Haar system in rearrangement invariant spaces
Greedy Algorithms and Best m-Term Approximation with Respect to Biorthogonal Systems.
Greedy approximation and the multivariate Haar system
We study nonlinear m-term approximation in a Banach space with regard to a basis. It is known that in the case of a greedy basis (like the Haar basis in , 1 < p < ∞) a greedy type algorithm realizes nearly best m-term approximation for any individual function. In this paper we generalize this result in two directions. First, instead of a greedy algorithm we consider a weak greedy algorithm. Second, we study in detail unconditional nongreedy bases (like the multivariate Haar basis in ,...
Greedy Approximation with Regard to Bases and General Minimal Systems
*This research was supported by the National Science Foundation Grant DMS 0200187 and by ONR Grant N00014-96-1-1003This paper is a survey which also contains some new results on the nonlinear approximation with regard to a basis or, more generally, with regard to a minimal system. Approximation takes place in a Banach or in a quasi-Banach space. The last decade was very successful in studying nonlinear approximation. This was motivated by numerous applications. Nonlinear approximation is important...
-widths for singularly perturbed problems
-widths for singularly perturbed problems
Kolmogorov -widths are an approximation theory concept that, for a given problem, yields information about the optimal rate of convergence attainable by any numerical method applied to that problem. We survey sharp bounds recently obtained for the -widths of certain singularly perturbed convection-diffusion and reaction-diffusion boundary value problems.
Nonlinear Approximation by Trigonometric Sums.
Optimal nonlinear approximation.
Recent developments in the theory of function spaces with dominating mixed smoothness
The aim of these lectures is to present a survey of some results on spaces of functions with dominating mixed smoothness. These results concern joint work with Winfried Sickel and Miroslav Krbec as well as the work which has been done by Jan Vybíral within his thesis. The first goal is to discuss the Fourier-analytical approach, equivalent characterizations with the help of derivatives and differences, local means, atomic and wavelet decompositions. Secondly, on this basis we study approximation...
Replicant compression coding in Besov spaces
We present here a new proof of the theorem of Birman and Solomyak on the metric entropy of the unit ball of a Besov space on a regular domain of The result is: if s - d(1/π - 1/p)+> 0, then the Kolmogorov metric entropy satisfies H(ε) ~ ε-d/s. This proof takes advantage of the representation of such spaces on wavelet type bases and extends the result to more general spaces. The lower bound is a consequence of very simple probabilistic exponential inequalities. To prove the upper bound,...
Replicant compression coding in Besov spaces
We present here a new proof of the theorem of Birman and Solomyak on the metric entropy of the unit ball of a Besov space on a regular domain of The result is: if then the Kolmogorov metric entropy satisfies . This...
Simplexe mit streng monotoner Entropiezahlenfolge
Some logarithmic function spaces, entropy numbers, applications to spectral theory [Book]
Some remarks on relative diameters
Some type of rotational scheme.
Spaces of Lipschitz type, embeddings and entropy numbers [Book]
Zur metrischen Entropie der Lipschitzfunktionen mit vorgegebenen Nullstellen
-энтропия компактов в и табулирование непрерывных функций.
ε-Entropy and moduli of smoothness in -spaces
The asymptotic behaviour of ε-entropy of classes of Lipschitz functions in is obtained. Moreover, the asymptotics of ε-entropy of classes of Lipschitz functions in whose tail function decreases as is obtained. In case p = 1 the relation between the ε-entropy of a given class of probability densities on and the minimax risk for that class is discussed.