Some improvements of numerical radius inequalities via Specht’s ratio

نویسندگان

  • M. Hassani Department of Mathematics, Mashhad Branch, Islamic Azad University, Mashhad, Iran
  • Y. Khatib Department of Mathematics, Mashhad Branch, Islamic Azad University, Mashhad, Iran
چکیده مقاله:

We obtain some inequalities related to the powers of numerical radius inequalities of Hilbert space operators. Some results that employ the Hermite-Hadamard inequality for vectors in normed linear spaces are also obtained. We improve and generalize some inequalities with respect to Specht's ratio. Among them, we show that, if $A, Bin mathcal{B(mathcal{H})}$ satisfy in some conditions, it follows that begin{equation*} omega^2(A^*B)leq frac{1}{2S(sqrt{h})}Big||A|^{4}+|B|^{4}Big|-displaystyle{inf_{|x|=1}} frac{1}{4S(sqrt{h})}big(biglangle big(A^*A-B^*Bbig) x,xbigranglebig)^2 end{equation*} for some $h>0$, where $|cdot|,,,,omega(cdot)$ and $S(cdot)$ denote the usual operator norm, numerical radius and the Specht's ratio, respectively.

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عنوان ژورنال

دوره 09  شماره 03

صفحات  221- 230

تاریخ انتشار 2020-09-01

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