Monthly seminar, usually first Wednesday, 4 pm (CET)  via Zoom.

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The abstracts and slides of all previous talks  can be found on researchseminars.org or here.

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01.04.2026 - 4 pm (CEST) - Michal Wojtylak (Jagiellonian University)

Title:

Linear algebra of dissipative Hamiltonian systems.

Abstract:

We will begin with a review of the Kronecker of pencils appearing in the port Hamiltonian modelling. Although the task  seems to be completed by  [1], and [2], the transfer function considerations in  [3] put a different light on these results.

In the second part of the talk we will concentrate on the eigenvalue infinity, and the size of the largest Kronecker block -  the index. 

We will study  the perturbation properties of the eigenvalue infinity, presenting non-asymptotic results based on the Bauer-Fike theorem, see [4].   Several numerical examples will be considered.

[1] C. Mehl, V. Mehrmann, and M. Wojtylak. Matrix pencils with coefficients that have positive
semidefinite Hermitian parts. SIMAX 2022. 

[2]  N. Gillis, V. Mehrmann, and P. Sharma. Computing the nearest stable matrix pairs. NLAA, 2018.

[3] K. Cherifi, H. Gernandt, and D. Hinsen. The difference between port-Hamiltonian, passive and
positive real descriptor systems. MCSS,  2024.

[4] H. Blazhko, M. Wojtylak, Detection of the higher order Kronecker blocks by perturbation, 2026 , preprint.

May 06, 2026 - Carsten Hartmann 

June 03, 2026- Anthony Hastir