English

Some generalized numerical radius inequalities involving Kwong functions

Functional Analysis 2018-01-24 v1

Abstract

We prove several numerical radius inequalities involving positive semidefinite matrices via the Hadamard product and Kwong functions. Among other inequalities, it is shown that if XX is an arbitrary n×nn\times n matrix and A,BA,B are positive semidefinite, then \begin{align*} \omega(H_{f,g}(A))\leq k\, \omega(AX+XA), \end{align*} which is equivalent to \begin{align*} \omega\big(H_{f,g}(A,B)\pm H_{f,g}(B,A)\big)\leq k'\,\left\{\omega((A+B)X+X(A+B))+\omega((A-B)X-X(A-B))\right\}, \end{align*} where ff and gg are two continuous functions on (0,)(0,\infty) such that h(t)=f(t)g(t)h(t)={f(t)\over g(t)} is Kwong, k=max{f(λ)g(λ)λ:λσ(A)}k=\max\left\{{f(\lambda)g(\lambda)\over \lambda}: {\lambda\in\sigma(A)}\right\} and k=max{f(λ)g(λ)λ:λσ(A)σ(B)}k'=\max\left\{{f(\lambda)g(\lambda)\over \lambda}: {\lambda\in\sigma(A)\cup\sigma(B)}\right\}.

Keywords

Cite

@article{arxiv.1801.07619,
  title  = {Some generalized numerical radius inequalities involving Kwong functions},
  author = {Mojtaba Bakherad},
  journal= {arXiv preprint arXiv:1801.07619},
  year   = {2018}
}

Comments

To appear in Hacettepe Journal of Mathematics and Statistics

R2 v1 2026-06-22T23:53:15.299Z