2017
Том 69
№ 9

# On estimate for numerical radius of some contractions

Karaev M. T.

Abstract

For the numerical radius of an arbitrary nilpotent operator T on a Hilbert space H, Haagerup and de la Harpe proved the inequality $w(T) \leqslant \left\| T \right\|cos\frac{\pi }{{n + 1}}$, where $n \geq 2$ is the nilpotency order of the operator T. In the present paper, we prove a Haagerup-de la Harpe-type inequality for the numerical radius of contractions from more general classes.

English version (Springer): Ukrainian Mathematical Journal 58 (2006), no. 10, pp 1512-1516.

Citation Example: Karaev M. T. On estimate for numerical radius of some contractions // Ukr. Mat. Zh. - 2006. - 58, № 10. - pp. 1335–1339.

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