New inequalities for operator concave functions involving positive linear maps

Abstract

The purpose of this paper is to present some general inequalities for operator concave functions which include some known inequalities as a particular case. Among other things, we prove that if $A\in \mathcal{B}\left(\mathcal{H}\right)$ is a positive operator such that $mI\le A\le MI$ for some scalars $0<m<M$ and $\Phi$ is a normalized positive linear map on $\mathcal{B}\left(\mathcal{H}\right)$, then \[\begin{aligned} {{\left( \frac{M+m}{2\sqrt{Mm}} \right)}^{r}}&\ge {{\left( \frac{\frac{1}{\sqrt{Mm}}Φ\left( A \right)+\sqrt{Mm}Φ\left( {{A}^{-1}} \right)}{2} \right)}^{r}} & \ge \frac{\frac{1}{{{\left( Mm \right)}^{\frac{r}{2}}}}Φ{{\left( A \right)}^{r}}+{{\left( Mm \right)}^{\frac{r}{2}}}Φ{{\left( {{A}^{-1}} \right)}^{r}}}{2} & \ge Φ{{\left( A \right)}^{r}}\sharpΦ{{\left( {{A}^{-1}} \right)}^{r}}, \end{aligned}\] where $0\le r\le 1$, which nicely extend the operator Kantorovich inequality.

to appear in Math. Inequal. Appl