Back to Search Start Over

Matrix Inequalities between $f(A)\sigma f(B)$ and $A\sigma B$

Authors :
Devi, Manisha
Aujla, Jaspal Singh
Kian, Mohsen
Moslehian, Mohammad Sal
Publication Year :
2023

Abstract

Let $A$ and $ B$ be $n\times n$ positive definite complex matrices, let $\sigma$ be a matrix mean, and let $f : [0,\infty)\to [0,\infty)$ be a differentiable convex function with $f(0)=0$. We prove that $$f^{\prime}(0)(A \sigma B)\leq \frac{f(m)}{m}(A\sigma B)\leq f(A)\sigma f(B)\leq \frac{f(M)}{M}(A\sigma B)\leq f^{\prime}(M)(A\sigma B),$$ where $m$ represents the smallest eigenvalues of $A$ and $B$ and $M$ represents the largest eigenvalues of $A$ and $B$. If $f$ is differentiable and concave, then the reverse inequalities hold. We use our result to improve some known subadditivity inequalities involving unitarily invariant norms under certain mild conditions. In particular, if $f(x)/x$ is increasing, then $$|||f(A)+f(B)|||\leq\frac{f(M)}{M} |||A+B|||\leq |||f(A+B)|||$$ holds for all $A$ and $B$ with $M\leq A+B$. Furthermore, we apply our results to explore some related inequalities. As an application, we present a generalization of Minkowski's determinant inequality.equality.<br />Comment: to appear in Aequationes Mathematicae

Details

Database :
arXiv
Publication Type :
Report
Accession number :
edsarx.2302.08127
Document Type :
Working Paper
Full Text :
https://doi.org/10.1007/s00010-024-01059-z