The numerical range of non-negative operators in Krein spaces

We define and characterize the Krein space numerical range $W(A)$ and the Krein space co-numerical range $W_{\rm co}(A)$ of a non-negative operator $A$ in a Krein space. It is shown that the non-zero spectrum of $A$ is contained in the closure of $W(A)\cap W_{\rm co}(A)$.

Bibliographic Details
Published in:Linear algebra and its applications, 438(2013), 5, Seite 2542-2556
Main Author: Philipp, Friedrich (Author)
Other Involved Persons: Trunk, Carsten
Format: electronic Article
Published: 2013
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