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On a conjecture of Hubner |
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| Authors: | F O Farid |
| Institution: | (1) Canada VIT 4L9, Veraon, B.C., Canada |
| Abstract: | In this paper we show that for a bounded linear operatorA on a complex Hilbert spaceH, the points on the boundary of the numerical range ofA with infinite curvature and unique tangent are in the essential spectrum ofA, thus positively answering a conjecture raised by Hubner in 3]. |
| Keywords: | Spectrum numerical range Hilbert space |
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