Some inequalities for operator (p,h)-convex functions

Abstract

Let $p$ be a positive number and $h$ a function on ${\mathbb{R}}^{+}$ satisfying $h(xy)\ge h(x)h(y)$ for any $x,y\in {\mathbb{R}}^{+}$. A non-negative continuous function $f$ on $K(\subset {\mathbb{R}}^{+})$ is said to be {\it operator $(p,h)$-convex} if \begin{equation*}\label{def} f ([αA^p + (1-α)B^p]^{1/p}) \leq h(α)f(A) +h(1-α)f(B) \end{equation*} holds for all positive semidefinite matrices $A,B$ of order $n$ with spectra in $K$, and for any $\alpha \in (0,1)$. In this paper, we study properties of operator $(p,h)$-convex functions and prove the Jensen, Hansen-Pedersen type inequalities for them. We also give some equivalent conditions for a function to become an operator $(p,h)$-convex. In applications, we obtain Choi-Davis-Jensen type inequality for operator $(p,h)$-convex functions and a relation between operator $(p,h)$-convex functions with operator monotone functions.