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arXiv · 1409.5535

Further refinements of the Cauchy-Schwarz inequality for matrices

Mojtaba Bakherad
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Abstract

Let $A, B$ and $X$ be $n\times n$ matrices such that $A, B$ are positive semidefinite. We present some refinements of the matrix Cauchy-Schwarz inequality by using some integration techniques and various refinements of the Hermite--Hadamard inequality. In particular, we establish the inequality \begin{align*} |||\,|A^{1\over2}XB^{1\over2}|^r|||^2&\leq|||\,|A^{t}XB^{1-s}|^r||| \,\,\,|||\,|A^{1-t}XB^{s}|^r|||\\& \leq\max \{|||\,|AX|^r||| \,\,\,|||\,|XB|^r|||,|||\,|AXB|^r||| \,\,\,|||\,|X|^r|||\}, \end{align*} where $s,t\in[0,1]$ and $r\geq0$.

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Mojtaba Bakherad. 2014-09-19. Further refinements of the Cauchy-Schwarz inequality for matrices. https://arxiv.org/abs/1409.5535

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