Department of Mathematics, University of Tennessee, Knoxville, Tennessee 37996-1300
Nathan S. Feldman ; Department of Mathematics, University of Tennessee, Knoxville, Tennessee 37996-1300
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.