2 citations · 2 across the 4 of their papers we have counts for
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math.FA2017
Accumulation of Complex Eigenvalues of a Class of Analytic Operator Functions
Christian Engström, Axel Torshage
For analytic operator functions, we prove accumulation of branches of complex eigenvalues to the essential spectrum. Moreover, we show minimality and completeness of the correspond…
math.FA2016
On Equivalence and Linearization of Operator Matrix Functions with Unbounded Entries
Christian Engström, Axel Torshage
In this paper we present equivalence results for several types of unbounded operator functions. A generalization of the concept equivalence after extension is introduced and used t…
math.FA2016
Enclosure of the Numerical Range of a Class of Non-Selfadjoint Rational Operator Functions
Christian Engström, Axel Torshage
In this paper we introduce an enclosure of the numerical range of a class of rational operator functions. In contrast to the numerical range the presented enclosure can be computed…