Publikationen Prof. Trunk

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Results: 171
Created on: Fri, 19 Apr 2024 23:10:39 +0200 in 0.0923 sec


Derkach, Volodymyr; Schmitz, Philipp; Trunk, Carsten
PT-symmetric Hamiltonians as couplings of dual pairs. - Ilmenau : Technische Universität Ilmenau, Institut für Mathematik, 2021. - 1 Online-Ressource (15 Seiten). - (Preprint ; M21,02)
https://nbn-resolving.org/urn:nbn:de:gbv:ilm1-2021200042
Leben, Leslie; Martínez Pería, Francisco; Philipp, Friedrich; Trunk, Carsten; Winkler, Henrik
Finite rank perturbations of linear relations and matrix pencils. - In: Complex analysis and operator theory, ISSN 1661-8262, Bd. 15 (2021), 2, 37, insges. 37 S.

We elaborate on the deviation of the Jordan structures of two linear relations that are finite-dimensional perturbations of each other. We compare their number of Jordan chains of length at least n. In the operator case, it was recently proved that the difference of these numbers is independent of n and is at most the defect between the operators. One of the main results of this paper shows that in the case of linear relations this number has to be multiplied by n+1 and that this bound is sharp. The reason for this behavior is the existence of singular chains. We apply our results to one-dimensional perturbations of singular and regular matrix pencils. This is done by representing matrix pencils via linear relations. This technique allows for both proving known results for regular pencils as well as new results for singular ones.



https://doi.org/10.1007/s11785-021-01082-x
Janse van Rensburg, Dawie B.; van Straaten, Madelein; Theron, Frieda; Trunk, Carsten
Square roots of H-nonnegative matrices. - In: Linear algebra and its applications, ISSN 0024-3795, Bd. 621 (2021), S. 29-49

https://doi.org/10.1016/j.laa.2021.03.006
Baidiuk, Dmytro; Derkach, Volodymyr; Hassi, Seppo
Unitary boundary pairs for isometric operators in Pontryagin spaces and generalized coresolvents. - In: Complex analysis and operator theory, ISSN 1661-8262, Bd. 15 (2021), 2, 32, insges. 52 S.

https://doi.org/10.1007/s11785-020-01073-4
Berger, Thomas; Snoo, Hendrik S. V. de; Trunk, Carsten; Winkler, Henrik
Linear relations and their singular chains. - Ilmenau : Technische Universität Ilmenau, Institut für Mathematik, 2021. - 1 Online-Ressource (17 Seiten). - (Preprint ; M21,01)
https://nbn-resolving.org/urn:nbn:de:gbv:ilm1-2021200018
Derkach, Volodymyr; Dym, Harry
Functional models for entire symmetric operators in rigged de Branges Pontryagin spaces. - In: Journal of functional analysis, ISSN 1096-0783, Bd. 280 (2021), 2, 108776

The theory of operator extensions in rigged Pontryagin spaces is used to develop two functional models for closed symmetric entire operators S with finite deficiency indices (p,p) acting in a separable Pontryagin space K. In the first functional model it is shown that every such operator S is unitarily equivalent to the multiplication operator in a de Branges-Pontryagin space B(E) of p×1 vector valued entire functions. The second functional model is used to parametrize a class of compressed resolvents of extensions ÜÞS of S in terms of the range of a linear fractional transformation that is associated with the model. This approach is independent of the methods used by Krein and Langer to parameterize a related class of extensions.



https://doi.org/10.1016/j.jfa.2020.108776
Gernandt, Hannes; Haller, Frederic E.; Reis, Timo; Schaft, Abraham Jan van der
Port-Hamiltonian formulation of nonlinear electrical circuits. - In: Journal of geometry and physics, Bd. 159 (2021), 103959, insges. 15 S.

We consider nonlinear electrical circuits for which we derive a port-Hamiltonian formulation. After recalling a framework for nonlinear port-Hamiltonian systems, we model each circuit component as an individual port-Hamiltonian system. The overall circuit model is then derived by considering a port-Hamiltonian interconnection of the components. We further compare this modeling approach with standard formulations of nonlinear electrical circuits.



https://doi.org/10.1016/j.geomphys.2020.103959
Gernandt, Hannes; Moalla, Nedra; Philipp, Friedrich; Selmi, Wafa; Trunk, Carsten
Invariance of the essential spectra of operator pencils. - In: Operator theory, operator algebras and their interactions with geometry and topology, (2020), S. 203-219

Gernandt, Hannes; Haller, Frédéric E.; Reis, Timo
A linear relation approach to port-Hamiltonian differential-algebraic equations. - [Hamburg[ : [Fachbereich Mathematik, Universität Hamburg], 2020. - 1 Online-Ressource (31 Seiten). - ([Hamburger Beiträge zur Angewandten Mathematik] ; [2020, 16])Titel der monographischen Reihe und Veröffentlichungsangabe von der Homepage entnommen

http://epub.sub.uni-hamburg.de/epub/volltexte/2020/112509/
Janse van Rensburg, Dawie B.; Van Straaten, Madelein; Theron, Frieda; Trunk, Carsten
Square roots of H-nonnegative matrices. - Ilmenau : Technische Universität Ilmenau, Institut für Mathematik, 2020. - 1 Online-Ressource (24 Seiten). - (Preprint ; M20,01)
https://nbn-resolving.org/urn:nbn:de:gbv:ilm1-2020200426

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