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A new criterion for k-hyponormality via weak subnormality
Journal article   Open access   Peer reviewed

A new criterion for k-hyponormality via weak subnormality

Raúl E Curto, Sang Hoon Lee and Woo Young Lee
Proceedings of the American Mathematical Society, Vol.133(6), pp.1805-1816
2005
DOI: 10.1090/S0002-9939-04-07727-5
url
https://doi.org/10.1090/S0002-9939-04-07727-5View
Published (Version of record) Open Access

Abstract

In this article we obtain a criterion for k-hyponormality via weak subnormality. Using this criterion we recapture Spitkovskii's subnormality criterion and give a simple proof of the main result in Gu's preprint (2001), which describes a gap between k-hyponormality and (k+ 1)-hyponormality for Toeplitz operators. In addition, we notice that the minimal normal extension of a subnormal operator is exactly the inductive limit of its minimal partially normal extensions.

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