On the boundary of numerical ranges of operators (Q628247)
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scientific article; zbMATH DE number 5864266
| Language | Label | Description | Also known as |
|---|---|---|---|
| English | On the boundary of numerical ranges of operators |
scientific article; zbMATH DE number 5864266 |
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On the boundary of numerical ranges of operators (English)
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10 March 2011
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The boundary of numerical ranges of operators has attracted the attention of a number of mathematicians. A new characterization of an attained boundary point of the numerical range of an operator on a Hilbert space is established. As an application, the authors point out a gap in the proof of the main result in the paper [\textit{M.\,T. Chien} and \textit{L. Yeh}, ``On the boundary of the numerical range of a matrix'', Appl.\ Math.\ Lett.\ 23, No.\,6, 725--727 (2010; Zbl 1194.15023)].
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numerical range
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boundary
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inner product
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convex set
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