Physics Colloquium

During the lecture period on selected Tuesdays, a guest usually speaks about his or her current area of research. Everyone is cordially invited to this public event. Especially for students, this offers the opportunity to get a good overview of current topics in physics and adjacent areas.

Inaugural lecture Hide: New professors introduce themselves and their research with an inaugural lecture, a generally understandable scientific lecture in a festive setting, to students and members of the Institute of Physics as well as the general university public.
Colloquium day of the students Hide: Once a semester, the speaker in the Physics Colloquium is invited by the students.Once a semester, the speaker in the Physics Colloquium is invited by the students.
Physicists at Work - Almni Colloquium Hide: In cooperation with the 'Absolventen- und Förderverein MPI Uni Bayreuth e.V. ', the Department of Physics organizes a special alumni colloquium at which an alumni of physics reports on his professional practice after his studies in Bayreuth.

Organizer

The lecturers of physics

Programme for the winter semester 2025/2026

programme overview (PDF)

Wednesday, 22. October, 6 p.m., H15, NW I	Emil Warburg Award Ceremony Mikro-Dartscheiben für das Quanteninternet - Als eine Quantenlichtquelle auszog um Europa zu bereisen... (Micro dartboards for the quantum internet - When a quantum light source set out to travel across Europe...) Prof. Dr. Tobias Heindel (Department für Quantentechnologien, Universität Münster) https://www.physik.uni-bayreuth.de/warburgpreis
28 October	Physikalisches Kolloquium der Studierenden Cilia driven flow in the mammalian brain [poster] Prof. Dr. Dr. h. c. Eberhard Bodenschatz (Max Planck Institute for Dynamics and Self-Organization)
11 November 2025	Connecting Ferrofluids and Living Matter [poster] Prof. Dr. Jaakko Timonen (Aalto University, Espoo, Finland)
25 November 2025	Quantum Billiards with Free Electrons [poster] Prof. Dr. Claus Ropers (Max Planck Institute for Multidisciplinary Sciences, Göttingen)
9 Dezember 2025	Explaining flow patterns by non-existing solutions of the governing equations [poster] Prof. Dr. Tobias Schneider (EPFL, Lausanne, Switzerland)
13 January 2026	Physicists at Work - Almni Colloquium Lebensretter bei einem Crash: Einblicke in die Entwicklung von Kindersitzen bei Cybex (Life savers in a crash: insights into the development of child seats at Cybex) Dr. Thomas Müller (Director Analysis & Testing, Cybex, Bayreuth)
27 January 2026	“The Photophysics of Molecular Aggregates [poster] Prof. Dr. Jürgen Köhler (Soft Matter Spectroscopy, University of Bayreuth)

Place and time

Unless otherwise stated, on Tuesday, 5 pm (s.t.) in the Lecture Hall H18, building NW II.

Next event

Physikalisches Kolloquium am 9. Dezember 2025

Talk

Explaining flow patterns by non-existing solutions of the governing equations

Prof. Dr. Tobias Schneider
EPFL, Lausanne, Switzerland

Tuesday, 9 December 2025, 5pm s.t.

lecture hall H18, building NW II
University of Bayreuth

abstract Hide: Invariant solutions of the governing equations, such as unstable equilibria and periodic orbits, are believed to serve as elementary building blocks of chaotic fluid flows and to play a major role in the emergence of patterns and coherent flow structures. Close to a saddle-node bifurcation, when two invariant solutions collide and annihilate, the flow behavior can closely resemble that of the solution at the bifurcation point, even though the solution itself does not exist at the studied parameter value. Therefore, patterns and coherent flow structures may emerge as a result of the dynamics feeling a non-existing invariant solution, a phenomenon called the ‘ghost’ of a solution. We formulate invariant solutions as global minima (zeros) of a non-negative cost function defined in appropriate search spaces. With this definition of invariant solutions, their ghosts manifest as non-zero local minima of the cost function in the vicinity of a saddle-node bifurcation: Two global minima (that represent two invariant solutions) merge through a saddle-node bifurcation and, as the control parameter is further changed from the bifurcation point, a local minimum is formed which lifts away from zero. Thanks to recently developed matrix-free algorithms, we are now able to solve the posed minimization problem and, thereby, compute ghosts of equilibria and periodic orbits in very high-dimensional problems including 3D fluid flows. We converge and continue properties of ghosts in 3D Rayleigh—Bénard convection, and show that ghost states are indeed able to capture pattern dynamics within a chaotic regime.
biography Hide: Tobias M. Schneider is an Associate Professor in the School of Engineering at EPFL, the Swiss Federal Institute of Technology in Lausanne and the director of EPFL's Doctoral Program in Mechanics. He received his PhD in theoretical physics from the University of Marburg in 2007 for work on the transition to turbulence in pipe flow, before joining Harvard University as a postdoctoral fellow. In 2012, he established an independent Max Planck Research Group at the Max Planck Institute for Dynamics and Self-Organization in Göttingen, and in 2014 he moved to EPFL, where he teaches fluid mechanics and leads the Emergent Complexity in Physical Systems Laboratory. His research focuses on nonlinear mechanics, with particular emphasis on spatial turbulent–laminar patterns in transitional flows, the buckling of elastic shells, and emergent phenomena in nonlinear optics. Together with his team, he develops algorithmic frameworks and computational tools to uncover the solution structure of nonlinear differential equations governing fluid flows and other complex physical systems.

Department of Physics at the University of Bayreuth

Faculty of Mathematics, Physics and Computer Sciences