Betterment for estimates of the numerical radii of Hilbert space operators

Document Type : Original Article

Authors

1 Department of Mathematics, Ferdows Branch, Islamic Azad University, Ferdows, Iran

2 Department of Mathematics, Payame Noor University (PNU), P.O. Box, 19395-4697, Tehran, Iran

Abstract

We give several inequalities involving numerical radii $\omega \left( \cdot \right)$ and the usual operator norm $\left\| \cdot \right\|$ of Hilbert space operators. These inequalities lead to a considerable improvement in the well-known inequalities
½||T||≤ω(T)≤||T||

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Main Subjects