The essential selfcommutator of a subnormal operator

Conway, John; Feldman, Nathan

doi:10.1090/S0002-9939-97-03698-8

The essential selfcommutator of a subnormal operator
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by John B. Conway and Nathan S. Feldman PDF

Proc. Amer. Math. Soc. 125 (1997), 243-244 Request permission

Abstract:

In this paper an easier proof is obtained of Alexandru Aleman’s extension of an inequality of Axler and Shapiro for subnormal operators to the essential norm. The method is applied to show that a hyponormal operator whose essential spectrum has area zero must be essentially normal.

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