English

Asymmetric Choi--Davis inequalities

Functional Analysis 2021-07-23 v1

Abstract

Let Φ\Phi be a unital positive linear map and let AA be a positive invertible operator. We prove that there exist partial isometries UU and VV such that Φ(f(A))Φ(A)Φ(g(A))UΦ(f(A)Ag(A))U |\Phi(f(A))\Phi(A)\Phi(g(A))|\leq U^*\Phi(f(A)Ag(A))U and Φ(f(A))rΦ(A)rΦ(g(A))rVΦ(f(A)rArg(A)r)V\left|\Phi\left(f(A)\right)^{-r}\Phi(A)^r\Phi\left(g(A)\right)^{-r}\right|\leq V^*\Phi\left(f(A)^{-r}A^rg(A)^{-r}\right)V hold under some mild operator convex conditions and some positive numbers rr. Further, we show that if f2f^2 is operator concave, then Φ(f(A))Φ(A)Φ(Af(A)). |\Phi(f(A))\Phi(A)|\leq \Phi(Af(A)). In addition, we give some counterparts to the asymmetric Choi--Davis inequality and asymmetric Kadison inequality. Our results extend some inequalities due to Bourin--Ricard and Furuta.

Keywords

Cite

@article{arxiv.2001.09962,
  title  = {Asymmetric Choi--Davis inequalities},
  author = {Mohsen Kian and M. S. Moslehian and R. Nakamoto},
  journal= {arXiv preprint arXiv:2001.09962},
  year   = {2021}
}
R2 v1 2026-06-23T13:22:05.470Z