Abstract
Let $A \in M_n(C)$. The numerical range of $A$ is defined as $W(A) = \{x^*Ax: x \in C^n, |x|=1 \}$. We give a necessary and sufficient condition for $W(A)$ to be an elliptic disk. The criterion is applied to prove the elliptic numerical ranges of certain bordered matrices.
Citation
Mao-Ting Chien. Kuo-Chih Hung. "ELLIPTIC NUMERICAL RANGES OF BORDERED MATRICES." Taiwanese J. Math. 16 (3) 1007 - 1016, 2012. https://doi.org/10.11650/twjm/1500406675
Information
