On upper and lower bounds of the numerical radius and an equality condition

• Autorzy: Takeaki Yamazaki
• Języki publikacji: EN

Abstrakty

EN

We give an inequality relating the operator norm of T and the numerical radii of T and its Aluthge transform. It is a more precise estimate of the numerical radius than Kittaneh's result [Studia Math. 158 (2003)]. Then we obtain an equivalent condition for the numerical radius to be equal to half the operator norm.

Kategorie tematyczne

• 47A30: Norms (inequalities, more than one norm, etc.)
• 47A12: Numerical range, numerical radius
• 47A20: Dilations, extensions, compressions

• Wydawca: Institute of Mathematics Polish Academy of Sciences
• Czasopismo: Studia Mathematica
• Rocznik: 2007
• Tom: 178
• Numer: 1
• Strony: 83-89

Daty

wydano

2007

Twórcy

autor

Takeaki Yamazaki

• Department of Mathematics, Kanagawa University, Yokohama 221-8686, Japan

Identyfikatory

DOI

10.4064/sm178-1-5