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Prof. Dr. Achim Ilchmann

Head of Group

Phone +49 3677 69-3623

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M. Sc. Hannes Gernandt

E-Mail:   hannes.gernandt[at]
Telefon: +49 3677 69-3254
Telefax: +49 3677 69-3270
Büro:      Curiebau, Raum C 230, 
             Weimarer Straße 25, 98693 Ilmenau



9. Locating the extremal entries of the Fiedler vector for rose trees,

    to appear in Proc. Appl. Math. Mech. 19. pdf-file


8. Invariance of the essential spectra of operator pencils (with N. Moalla,

     F. Philipp, W. Selmi, and C. Trunk), submitted.


7. Schur reduction of trees and extremal entries of the Fiedler vector

     (with J.P. Pade), Linear Algebra Appl. 570 (2019), 93-122. pdf-file


6. Locally finite extensions and Gesztesy-Šeba realizations for the Dirac

operator on a metric graph (with C. Trunk), submitted. pdf-file


5. The gap distance to the set of singular matrix pencils

(with T. Berger, C. Trunk, H. Winkler, M. Wojtylak), submitted. pdf-file


4. A new method for network redesign via rank one updates, 

(with D. Krauße, R. Sommer, C. Trunk), Proc. Appl. Math. Mech. 17 (2017). pdf-file


3. A new bound for the distance to singularity of a regular matrix pencil,

(with T. Berger, C. Trunk, H. Winkler, M. Wojtylak), Proc. Appl. Math. Mech. 17 (2017). pdf-file


2. Eigenvalue placement for regular matrix pencils with rank one perturbations

(with C. Trunk), SIAM J. Matrix Anal. & Appl. 38 (2017), pp. 134-154.  pdf-file


1. On the parametric eigenvalue behavior of matrix pencils under rank one perturbations

(with C. Trunk), Proc. Appl. Math. Mech. 16 (2016), pp. 873-874;

Extended Version: pdf-file



Untersuchung von Quantengraphen mittels direkter Summen von Randtripeln           




03/2019: One-dimensional perturbations of singular matrix pencils, 9th Descriptor Workshop,

                Paderborn. Slides

02/2019: On the essential spectrum of operator pencils, 90th GAMM Annual Meeting,

                Vienna. Slides

09/2018: On network redesign, Siegmundsburg Workshop, Ilmenau.

09/2018: Point interactions on infinite graphs, Mikael-Passare-Day, Stockholm.

04/2018: Eigenvalue assignment for matrix pencils with application to network redesign,

                Seminario de Análisis Funcional "Mischa Cotlar", Buenos Aires.

03/2018: On the distance between DAEs, Siegmundsburg Workshop.

02/2018: On the gap distance between matrix pencils, Absolventen-Seminar Numerische

                 Mathematik, TU Berlin. Slides

08/2017: The end of the saga? A solution to a problem posed by R. Sommer, Siemundsburg

               Workshop, Ilmenau. Slides

06/2017: Rank one perturbation of matrix pencils with application to electric circuits,

               Forschungsseminar: Mathematische Modellierung & numerische Simulation, HU Berlin.

05/2017: Locally finite extensions of direct sum operators, Workshop of the GAMM Activity

                Group Applied Operator Theory, Hamburg.

03/2017: On the rank one inverse eigenvalue problem for Hermitian matrix pencils,

   88th Annual Meeting GAMM, Weimar. Slides

08/2016: Distance to singularity for DAEs, Oberseminar Systemtheorie, Erfurt. Slides

06/2016: The Dantzig Selector, Seminar "Sparse Recovery and Compressed Sensing",

TU Ilmenau. Skript

03/2016: Eigenvalue placement for regular matrix pencils with rank one perturbations,

Gemeinsame Jahrestagung von GAMM und DMV, Braunschweig. Slides

09/2015: Laplacians on infinite graphs, 4th Najman conference on Spectral Problems for

Operators and Matrices, Opatija.  Slides

07/2015: Konvergenz von Markovketten, Seminar "Graphen und Stochastik", TU Ilmenau.