On estimate for numerical radius of some contractions

• Published in: Український математичний журнал
• Date: 2006
• Main Author: Karaev, M.T.
• Format: Article
• Language: English
• Published: Інститут математики НАН України 2006
• Subjects: Статті
• Online Access: https://nasplib.isofts.kiev.ua/handle/123456789/165421
• Journal Title: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Cite this: On estimate for numerical radius of some contractions / M.T. Karaev // Український математичний журнал. — 2006. — Т. 58, № 10. — С. 1335–1339. — Бібліогр.: 14 назв. — англ.

For the numerical radius of an arbitrary nilpotent operator T on a Hilbert space H, Haagerup and de la Harpe proved the inequality w(T)≤||T||cos(π/(n+1)), where n≥2 is the nilpotency order of the operator T. In the present paper, we prove a Haagerup-de la Harpe-type inequality for the numerical radi...