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SOME INEQUALITIES FOR THE NUMERICAL RADIUS FOR HILBERT SPACE OPERATORS

Published online by Cambridge University Press:  26 September 2016

MOHSEN SHAH HOSSEINI
Affiliation:
Department of Mathematics, Mashhad Branch, Islamic Azad University, Mashhad, Iran email [email protected]
MOHSEN ERFANIAN OMIDVAR*
Affiliation:
Department of Mathematics, Mashhad Branch, Islamic Azad University, Mashhad, Iran email [email protected]
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Abstract

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We introduce some new refinements of numerical radius inequalities for Hilbert space invertible operators. More precisely, we prove that if $T\in {\mathcal{B}}({\mathcal{H}})$ is an invertible operator, then $\Vert T\Vert \leq \sqrt{2}\unicode[STIX]{x1D714}(T)$.

Type
Research Article
Copyright
© 2016 Australian Mathematical Publishing Association Inc. 

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