English

Various inequalities between quasi-arithmetic mean and quasi-geometric type means for matrices

Functional Analysis 2025-09-26 v2

Abstract

In this paper, for 0<α<10<\alpha<1, p>0p>0 and positive semidefinite matrices A,B0A,B\ge0, we consider the quasi-extension Aα,p(A,B):=((1α)Ap+αBp)1/p\mathcal{A}_{\alpha,p}(A,B):=((1-\alpha)A^p+\alpha B^p)^{1/p} of the α\alpha-weighted arithmetic matrix mean, and the quasi-extensions Mα,p(A,B):=Mα(Ap,Bp)1/p\mathcal{M}_{\alpha,p}(A,B):=\mathcal{M}_\alpha(A^p,B^p)^{1/p} of several different α\alpha-weighted geometric-type matrix means Mα(A,B)\mathcal{M}_\alpha(A,B) such as the α\alpha-weighted geometric mean in Kubo and Ando's sense and two types of α\alpha-weighted version of Fiedler and Pt\'ak's spectral geometric mean, as well as the R\'enyi mean and the α\alpha-weighted Log-Euclidean mean. For these we examine the inequalities Aα,p(A,B)Aα,q(A,B)\mathcal{A}_{\alpha,p}(A,B)\triangleleft\mathcal{A}_{\alpha,q}(A,B) and Mα,p(A,B)Aα,q(A,B)\mathcal{M}_{\alpha,p}(A,B)\triangleleft\mathcal{A}_{\alpha,q}(A,B) of arithmetic-geometric type, where \triangleleft is one of several different matrix orderings varying from the strongest Loewner order to the weakest order determined by trace inequality. For each choice of the above inequalities, our goal is to hopefully obtain the necessary and sufficient condition on p,q,αp,q,\alpha under which the inequality holds for all A,B0A,B\ge0.

Keywords

Cite

@article{arxiv.2508.20309,
  title  = {Various inequalities between quasi-arithmetic mean and quasi-geometric type means for matrices},
  author = {Fumio Hiai},
  journal= {arXiv preprint arXiv:2508.20309},
  year   = {2025}
}

Comments

53 pages, This is the first half of the author's plenary talk in ILAS2025. Appendix A is corrected