An observation about pseudospectra
| Autor: | Youling Feng, Boting Jia |
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| Rok vydání: | 2021 |
| Předmět: | |
| Zdroj: | Filomat. 35:995-1000 |
| ISSN: | 2406-0933 0354-5180 |
| DOI: | 10.2298/fil2103995j |
| Popis: | For ? > 0 and a bounded linear operator T acting on some Hilbert space, the ?-pseudospectrum of T is ??(T) = {z ? C : ||(zI-T)-1|| > ?-1}. This note provides a characterization of those operators T satisfying ??(T) = ?(T) + B(0,?) for all ? > 0. Here B(0,?) = {z ? C : |z| < ?}. In particular, such operators on finite dimensional spaces must be normal. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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