Abstract
The $k$-rank numerical range $\Lambda_{k}(A)$ is expressed via an intersection of any countable family of numerical ranges $\{F(M^{*}_{\nu}AM_{\nu})\}_{\nu\in\mathbb{N}}$ with respect to $n\times (n-k+1)$ isometries $M_{\nu}$. This implication for $\Lambda_{k}(A)$ provides further elaboration of the $k$-rank numerical radii of $A$.
Citation
Aikaterini Aretaki. John Maroulas. "The k-rank numerical radii." Ann. Funct. Anal. 3 (1) 100 - 108, 2012. https://doi.org/10.15352/afa/1399900027
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