Separating classes of composition operators via subnormal condition

Jung, Il; Lee, Mi; Park, Sang

doi:10.1090/S0002-9939-07-09003-X

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ISSN 1088-6826(online) ISSN 0002-9939(print)

Separating classes of composition operators via subnormal condition

Authors: Il Bong Jung, Mi Ryeong Lee and Sang Soo Park
Journal: Proc. Amer. Math. Soc. 135 (2007), 3955-3965
MSC (2000): Primary 47B20, 47B33; Secondary 47A63
Posted: June 19, 2007
MathSciNet review: 2341946
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Abstract: Several classes have been considered to study the weak subnormalities of Hilbert space operators. One of them is -hypnormality, which comes from the Bram-Halmos criterion for subnormal operators. In this note we consider -hyponormality, which is the parallel version corresponding to the Embry characterization for subnormal operators. We characterize -hyponormality of composition operators via -th Radon-Nikodym derivatives and present some examples to distinguish the classes.

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