English

General Numerical Radius for Products of Sectorial Matrices

Functional Analysis 2025-06-04 v1

Abstract

In this paper, we investigate the generalized numerical radius ωN\omega_N, associated with a matrix norm NN defined by ωN(X)=supθRN(Re(eiθX))\omega_N(X) = \sup_{\theta \in \mathbb{R}} N(\operatorname{Re}(e^{i\theta}X)). We focus on matrices whose numerical ranges are contained in sectors of the complex plane (sectorial matrices) and derive upper bounds for ωN(XY)\omega_N(XY) and ωN(XY)\omega_N(X \circ Y) for such matrices XX and YY. Our results generalize and refine well known numerical radius inequalities. Several known inequalities for ω(X)\omega(X) are recovered as special cases.

Keywords

Cite

@article{arxiv.2506.02042,
  title  = {General Numerical Radius for Products of Sectorial Matrices},
  author = {Mohammad Alakhrass},
  journal= {arXiv preprint arXiv:2506.02042},
  year   = {2025}
}