Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5774578 | Journal of Mathematical Analysis and Applications | 2017 | 8 Pages |
Abstract
Let A and B be positive contractions on a Hilbert space. It was known before that the numerical range W(AB) of their product is contained in the rectangular region [â1/8,1]Ã[â1/4,1/4]. In this paper, we determine exactly when W(AB) touches on its four sides. This follows from the more general information on a containing region of W(AB) and on when they share a common tangent line. We also give an example of A and B on three-dimensional space for which W(AB) is not symmetric with respect to the x-axis.
Keywords
Related Topics
Physical Sciences and Engineering
Mathematics
Analysis
Authors
Hwa-Long Gau, Pei Yuan Wu,