Nonlinear Dynamics at the Free University Berlin

Summer 2023

Advanced Differential Equations and Advanced Delay Equations (Internal seminar)

Prof. Dr. Bernold Fiedler, Dr. Isabelle Schneider


May 25th, 2023 Dr. Isabelle Schneider (Freie Universität Berlin)

Public lecture as part of the habilitation:

From Pythagoras to Differential Equations: Uncovering the Mysteries of Musical Sound
For over two millennia, the relationship between the frequency of a vibrating string and its length has been studied, starting with Pythagoras' legendary experiments with the monochord. Many renowned scientists and mathematicians, including Mersenne, Bernoulli, Euler, Lagrange, d'Alembert, and Helmholtz, have conducted their own investigations on this subject. Despite the fact that the linear wave equation is frequently employed to model the sound spectrum of musical instruments, it does not truly reproduce the entire sound spectrum. In this talk, we will embark on a search for the flageolet harmonics and compare our mathematical findings to what we hear during live musical experiments. We will investigate recent models for string and woodwind instruments that rely on partial and delay differential equations, and we will uncover intriguing phenomena such as stiff damping and hysteresis.

The public lecture will take place at 16:15 in Hörsaal 001, Arnimallee 3.

Wednesday, June 28th

Arnimallee 6, Seminar room 025/026

Nicola Vassena (University of Leipzig) Purely imaginary beasts and where to find them
Isabelle Schneider (Free University of Berlin) and Jia-Yuan Dai (National Chung Hsing University, Taiwan) Groupoids for Pattern-Selective Feedback Stabilization of the Chafee-Infante Equation
Thursday, June 29th Alejandro Lopez-Nieto (Free University of Berlin) PhD Defence: Enharmonic motion: Towards the global dynamics of negative delayed feedback
Kadomtsev and Petviashvili initially proposed the KP partial differential equation to study the stability of solutions in the Korteweg-De Vries (KdV) equation for shallow-water waves in channels. Over time, it has become clear that the KP equation and its family of symmetries showcase a rich integrable structure containing many of the currently known integrable systems. However, in recent years the focus has shifted to the study of regular solitons: explicit solutions that correspond to elements of a suitably chosen positive Grassmannian. The talk will discuss the work of Kodama and Williams (2011) regarding the combinatorial classification of KP soliton asymptotics. Their results will take us on an ambitious journey connecting topics as far apart as algebraic combinatorics and partial differential equations.

Time and Place

Talks usually take place on Thursdays at 15:15, SR 140 in Arnimallee 7, 14195 Berlin

Talks will also be available via Zoom. To obtain the Zoom link please contact Patricia Habasescu

Guests are always welcome!


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