Chi-Kwong Li

collaborators

2 papers

math.FA2026

Numerical radius of certain two-by-two block matrices

Hwa-Long Gau, Jia-Huo Hong, Chi-Kwong Li +1

We investigate the numerical range $W (T)$ and numerical radius $w (T)$ of operators of the form $T = (A 0 B 0)$ . We show that $W (T)$ is the union…

math.FA2024

Norm of an operator with numerical range in a sector

Chi-Kwong Li, Kuo-Zhong Wang

We refine a recent result of Drury concerning the optimal ratio between the norm and numerical radius of a bounded linear operator $T$ with numerical range lying in a sector of a c…