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Compactness properties of operator cosine functions. (English) Zbl 0448.47021


MSC:

47D99 Groups and semigroups of linear operators, their generalizations and applications
39B52 Functional equations for functions with more general domains and/or ranges
47B06 Riesz operators; eigenvalue distributions; approximation numbers, \(s\)-numbers, Kolmogorov numbers, entropy numbers, etc. of operators
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