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arXiv · math/0411442

Jensen's Inequality and majorization

Jorge Antezana·Pedro Massey·Demetrio Stojanoff
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Abstract

Let $\mathcal{A}$ be a $C^*$-algebra and $ϕ:\cA\to L(H)$ be a positive unital map. Then, for a convex function $f:I\to \mathbb{R}$ defined on some open interval and a self-adjoint element $a\in \mathcal{A}$ whose spectrum lies in $I$, we obtain a Jensen's-type inequality $f(ϕ(a)) \leq ϕ(f(a))$ where $\le$ denotes an operator preorder (usual order, spectral preorder, majorization) and depends on the class of convex functions considered i.e., operator convex, monotone convex and arbitrary convex functions. Some extensions of Jensen's-type inequalities to the multi-variable case are considered.

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Jorge Antezana, Pedro Massey, Demetrio Stojanoff. 2004-11-19. Jensen's Inequality and majorization. https://arxiv.org/abs/math/0411442

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