Entropy numbers of r-nuclear operators between spaces
Entropy and n-widths of operators in Banach spaces
Inequalities of Bernstein-Jackson-type and the degree of compactness of operators in Banach spaces
The paper deals with covering problems and the degree of compactness of operators. The main part is devoted to relationships between entropy moduli and Kolmogorov (resp. Gelfand and approximation) numbers for operators which may be interpreted as counterparts to the classical Bernstein-Jackson inequalities for functions. Certain quantifications of results in the Riesz-Schauder-Theory are given. Finally, the largest distance between “the degree of approximation” and the “degree of compactness” of...
Inequalities Between Eigenvalues, Entropy Numbers, and Related Quantities of Compact Operators in Banach Spaces.
Estimating compactness properties of operators by the aid of generalized entropy numbers.
Gelfand numbers of operators with values in a Hilbert space.
Entropy and Eigenvalues of Certain Integral Operators.
Local entropy moduli and eigenvalues of operators in Banach spaces.
In the paper local entropy moduli of operators between Banach spaces are introduced. They constitue a generalization of entropy numbers and moduli, and localize these notions in an appropriate way. Many results regarding entropy numbers and moduli can be carried over to local entropy moduli. We investigate relations between local entropy moduli and s-numbers, spectral properties, eigenvalues, absolutely summing operators. As applications, local entropy moduli of identical and diagonal operators...
Gelfand numbers and metric entropy of convex hulls in Hilbert spaces
For a precompact subset K of a Hilbert space we prove the following inequalities: , n ∈ ℕ, and , k,n ∈ ℕ, where cₙ(cov(K)) is the nth Gelfand number of the absolutely convex hull of K and and denote the kth entropy and kth dyadic entropy number of K, respectively. The inequalities are, essentially, a reformulation of the corresponding inequalities given in [CKP] which yield asymptotically optimal estimates of the Gelfand numbers cₙ(cov(K)) provided that the entropy numbers εₙ(K) are slowly...
Weyl numbers versus Z-Weyl numbers
Given an infinite-dimensional Banach space Z (substituting the Hilbert space ℓ₂), the s-number sequence of Z-Weyl numbers is generated by the approximation numbers according to the pattern of the classical Weyl numbers. We compare Weyl numbers with Z-Weyl numbers-a problem originally posed by A. Pietsch. We recover a result of Hinrichs and the first author showing that the Weyl numbers are in a sense minimal. This emphasizes the outstanding role of Weyl numbers within the theory of eigenvalue distribution...
Entropy of -valued operators and diverse applications.
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