The numerical range of functions and best approximation
Published online by Cambridge University Press: 24 October 2008
Extract
In this note, we state general conditions which imply that the numerical range of a function mapping a set S into a normed linear space Y is the closed convex hull of the spatial numerical range of the function. This conclusion is of interest since, for example, it is equivalent to an extension to non-compact spaces of Kolmogoroff's characterization of functions of best approximation.
- Type
- Research Article
- Information
- Mathematical Proceedings of the Cambridge Philosophical Society , Volume 76 , Issue 1 , July 1974 , pp. 133 - 141
- Copyright
- Copyright © Cambridge Philosophical Society 1974
References
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