School of Mathematical & Statistical Sciences Faculty Publications

Propagation phenomena for hyponormal 2-variable weighted shifts

Document Type

Article

Publication Date

6-1-2007

Abstract

We study the class of hyponormal 2-variable weighted shifts with two consecutive equal weights in the weight sequence of one of the coordinate operators. We show that under natural assumptions on the coordinate operators, the presence of consecutive equal weights leads to horizontal or vertical flatness, in a way that resembles the situation for 1-variable weighted shifts. In 1-variable, it is well known that flat weighted shifts are necessarily subnormal (with finitely atomic Berger measures). By contrast, we exhibit a large collection of flat (i.e., horizontally and vertically flat) 2-variable weighted shifts which are hyponormal but not subnormal. Moreover, we completely characterize the hyponormality and subnormality of symmetrically flat contractive 2-variable weighted shifts. © Copyright by THETA, 2007.

Comments

Copyright by THETA, 2007

First Page

175

Last Page

203

Publication Title

Journal of Operator Theory

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