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Two conditions for subnormality of unbounded operators

Published online by Cambridge University Press:  04 June 2001

Jan Niechwiej
Affiliation:
Instytut Matematyki, Uniwersytet Jagielloński, UL. Reymonta 4, 30-059 Kraków, Poland e-mail:[email protected]
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We give two new sufficient conditions for unbounded Hilbert space operators to be subnormal. The first assumes that the sequence //Tnf//2 on a suitable subset of the domain is completely monotonic, the second is similar to the one given by Lambert in [3] for bounded operators and involves the sequence of binomial expansion of the real part of the operator.

Type
Research Article
Copyright
2001 Glasgow Mathematical Journal Trust