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 $\|\cdot\|$ of Hilbert space operators. These inequalities lead to a considerable improvement in the well-known inequalities
\begin{equation*}
\frac{1}{2}\left\| T \right\|\le \omega \left( T \right)\le \left\| T \right\|.
\end{equation*}

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References

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AUT Journal of Mathematics and Computing
Volume 4, Issue 2
March 2023
Pages 161-167

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