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Colloquium Mathematics, Matthias Bollhöfer, TU Braunschweig

01 March 2011

Join us for coffee and tea at 15.45 p.m.


Date: Tuesday, March 1st 2011

Speaker: Matthias Bollhöfer (TU Braunschweig)

Room: 5161.0267 (Bernoulliborg),

Time: 16.15





Title:Numerical solution methods for shifted Helmholtz and
time-harmonic Maxwell equations



The simulation of acoustic- and electromagnetic phenomena leads to
Helmholtz-, respectively to time-harmonic Maxwell equations. These
equations lead to large scale symmetric systems which are highly
indefinite and the process of solving them numerically is known to be
challenging. When approximating indefinite systems using preconditioning,
the eigenvalues of the preconditioned system have to cross the origin to
be finally clustered around the eigenvalue 1. One common approach to
bypass this bottleneck consists of shifting the initial system
appropriately and approximating the shifted system. To treat symmetric,
indefinite systems we consider approximating shifted systems by structure-
preserving techniques based on approximate LU factorizations. These apply
matching techniques from combinatorial optimization and use multilevel
strategies. We illustrate numerical results to show the effectiveness of
the combined approach.




Colloquium coordinators are Prof.dr. A.C.D. van Enter (e-mail : and

Dr. M. Dür (e-mail:


Last modified:06 June 2018 2.04 p.m.

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