Betterment for estimates of the numerical radii of Hilbert space operators

Document Type : Original Article


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


We give several inequalities involving numerical radii $\omega \left( \cdot \right)$ and the usual operator norm $\|\cdot\|$ of Hilbert space operators. These inequalities lead to a considerable improvement in the well-known inequalities
\frac{1}{2}\left\| T \right\|\le \omega \left( T \right)\le \left\| T \right\|.


Main Subjects

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