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Log-majorization related to R\'enyi divergences

Functional Analysis 2018-08-14 v1

Abstract

For α,z>0\alpha,z>0 with α1\alpha\ne1, motivated by comparison between different kinds of R\'enyi divergences in quantum information, we consider log-majorization between the matrix functions \begin{align*} P_\alpha(A,B)&:=B^{1/2}(B^{-1/2}AB^{-1/2})^\alpha B^{1/2}, \\ Q_{\alpha,z}(A,B)&:=(B^{1-\alpha\over2z}A^{\alpha\over z}B^{1-\alpha\over2z})^z \end{align*} of two positive (semi)definite matrices A,BA,B. We precisely determine the parameter α,z\alpha,z for which Pα(A,B)logQα,z(A,B)P_\alpha(A,B)\prec_{\log}Q_{\alpha,z}(A,B) and Qα,z(A,B)logPα(A,B)Q_{\alpha,z}(A,B)\prec_{\log}P_\alpha(A,B) holds, respectively.

Keywords

Cite

@article{arxiv.1808.03866,
  title  = {Log-majorization related to R\'enyi divergences},
  author = {Fumio Hiai},
  journal= {arXiv preprint arXiv:1808.03866},
  year   = {2018}
}

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21 pages