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Diminishing of the spectrum of an operator under extension

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A negative answer is given to the second question posed on page 210 of the book Complex Analysis — 199 Research Problems, Lecture Notes in Math., No. 1043, Springer, Berlin (1984).

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Translated from Teoriya Funktsii, Funktsional'nyi Analiz i Ikh Prilozheniya, No. 45, pp. 96–97, 1986.

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Ostrovskii, M.I. Diminishing of the spectrum of an operator under extension. J Math Sci 48, 450–451 (1990). https://doi.org/10.1007/BF01097575

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  • Lecture Note
  • Complex Analysis
  • Research Problem
  • Negative Answer
  • Book Complex