Das CeNoS selbst und die zugehörigen Fachbereiche bieten verschiedenste Veranstaltungen zum Thema Nonlinear Science an. Das Spektrum reicht dabei von Workshops und Tagungen, über das regelmäßige Kolloquium bis hin zu den zahlreichen Lehrveranstaltungen der beteiligten Fachbereiche.

Kolloquium Wintersemester 2017/18

The CeNoS Kolloquium starts always at 16.30 s.t in Room 222 of the Institute for Applied Physics. From 16.15 on coffee is available.

Datum Vortrag




Stability with respect to shocks

Prof. Dr. Ulrike Feudel
Universität Oldenburg

Natural or technical systems possess often several possible stable states of operation. Linear stability theory is the appropriate tool to study the stability properties of such states with respect to small perturbations. However, in nature perturbations are not necessarily small but are finite in size. We discuss two different methods how to investigate the stability with respect to large perturbations such as single shocks. Both methods aim to determine the distance to the boundary of the basin of attraction or the edge of chaos, respectively. The first method determines the minimal destabilizing perturbation for large dynamical systems such as networks. Besides the size of this perturbations the method allows also to obtain the direction of this perturbation. We illustrate this method using pollinator networks in ecology and energy networks and identify relations between the topology of a network and its stability properties. The second method measures return times to a stable state at the edge of chaos. This is demonstrated for the transition from laminar to turbulent motion in a shear flow.

Einladender: Dr. O. Kamps


Data Science als Berufsfeld für Physiker und Mathematiker

Dr. Anton Daitche

Einladender: Dr. O. Kamps


A Phase Field Model for Thin Elastic Structures with Topological Constraint

Prof. Patrick Dondl

Abteilung für Angewandte Mathematik, Albert-Ludwigs-Universität Freiburg

With applications in the area of biological membranes in mind, we consider the problem of minimizing Willmore’s energy among the class of closed, connected surfaces with given surface area that are confined to a fixed container. Based on a phase field model for Willmore’s energy originally introduced by de Giorgi, we develop a technique to incorporate the connectedness constraint into a diffuse interface model of elastic membranes. Our approach uses a geodesic distance function associated to the phase field to discern different connected components of the support of the limiting mass measure. We obtain both a suitable compactness property for finite energy sequences as well as a Gamma-convergence result. Furthermore, we present computational evidence for the effectiveness of our technique. The main argument in our proof is based on a new, natural notion of convergence to describe phase fields in three dimensions.

Einladender: Prof. B. Wirth


Nonlinear dynamics and time delays in engineering applications

Dr. Andreas Otto
Institut für Physik, TU Chemnitz

Time delay effects appear in many dynamical systems. Often the delay effect is a result of a transport phenomena and feedback and the systems are nonlinear. In this talk we discuss general aspects of such systems, which can be often found in engineering. The relevant applications ranging from manufacturing processes, such as rolling and metal cutting over gasoline engines to traffic flow dynamics. After an introduction to the field of time delay systems, we will first focus on systems with state-dependent delays. We show that in many situations equivalent representations with constant delays exist, which are much easier to analyze. In a second part systems with multiple and distributed delays are studied and we discuss our recent results on systems with dissipative delays. Dissipative delays are a specific class of time-varying delays and may lead to a hitherto unknown type of chaotic behavior in nonlinear delay systems.

Einladender: Dr. O. Kamps

Thin film modelling of surfactant-driven biofilm spreading
Sarah Trinschek (AG Thiele)

Active wetting drives collective cell migration in embryogenesis
Bernhard Wallermeyer (AG Betz)

Branched Covering Surfaces

Prof. Dr. Konrad Polthier
Freie Universität Berlin, AG Mathematical Geometry Processing

Multivalued functions and differential forms naturally lead to the concept of branched covering surfaces and more generally of branched covering manifolds in the spirit of Hermann Weyl's book "Die Idee der Riemannschen Fläche" from 1913. This talk will illustrate and discretize basic concepts of branched (simplicial) covering surfaces starting from complex analysis and surface theory up to their recent appearance in geometry processing algorithms and artistic mathematical designs.
Applications will touch differential based surface modeling, image and geometry retargeting, global surface and volume remeshing, and novel weaved geometry representations with recent industrial applications.