2 citations · 2 across the 4 of their papers we have counts for
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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…
Efficient resonance computations for Helmholtz problems based on a Dirichlet-to-Neumann map
Juan Carlos Araujo-Cabarcas, Christian Engstrom, Elias Jarlebring
We present an efficient procedure for computing resonances and resonant modes of Helmholtz problems posed in exterior domains. The problem is formulated as a nonlinear eigenvalue p…
On spurious solutions in finite element approximations of resonances in open systems
Juan Carlos Araujo-Cabarcas, Christian Engström
In this paper, we discuss problems arising when computing resonances with a finite element method. In the pre-asymptotic regime, we detect for the one dimensional case, spurious so…
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…