Upcoming Events
- Thursday, 04.09.2025, 15:00 (WIAS-ESH)
- Seminar Laserdynamik
Prof. Hiroya Nakao, Institute of Science , Japan:
Koopman operator approach to phase-amplitude reduction of nonlinear oscillators
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Abstract
Synchronization of self-sustained rhythms play important functional roles in real-world systems. Rhythmic systems are often modeled as nonlinear dynamical systems with stable limit-cycle orbits. In analyzing the dynamics of such limit-cycle oscillators, phase reduction theory, which approximately describes the oscillator using only the asymptotic phase defined along the limit cycle, has played a major role. Recently, Koopman operator theory has provided a new perspective on phase reduction, clarifying that the asymptotic phase and amplitudes are Koopman eigenfunctions of the oscillator. This has led to the generalization of conventional phase reduction into phase-amplitude reduction, enabling us to describe not only the phase but also amplitude deviations of the oscillator. In this talk, I will present a brief introduction to phase-amplitude reduction from the Koopman operator viewpoint and then several applications to synchronization control, including data-driven approaches.
Further Informations
Seminar Laserdynamik
Host
WIAS Berlin
- Wednesday, 10.09.2025, 14:15 (WIAS-ESH)
- Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Simon M. Murmann, Friedrich-Schiller-Universität Jena:
Hibler's time-periodic sea ice model on ℝ2
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Abstract
In 1979, Hibler introduced a model for the large-scale dynamics of sea ice, modeling it as a fluid with viscous-plastic rheology. The resulting momentum balance equation contains a stress tensor, which depends nonlinearly on the strain rate and on the ice strength. Here, the ice strength is given by the ice thickness characteristics - the mean ice thickness and the ice compactness -, which are in turn coupled to the system via continuity equations. In this talk, we consider a regularized version of Hibler's model on the whole space ℝ2 in a time-periodic framework. Our approach is based on interpreting the system as an abstract quasi-linear evolution equation and decomposing the linearized equation into a stationary and a purely oscillatory part. We will focus in particular on the challenges arising from the nonlinearities and the unboundedness of the domain and discuss possible strategies to overcome these difficulties.
Further Informations
Oberseminar “Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Host
Humboldt-Universität zu Berlin
WIAS Berlin
- Thursday, 11.09.2025, 14:00 (WIAS-ESH)
- Berlin Oberseminar: Optimization, Control and Inverse Problems
Dr. Thomas Surowiec, Simula Research Laboratory, Norway:
The Latent Variable Proximal Point Method: A New Solver Paradigm for Variational Inequalities, Nonlinear PDEs, and Beyond
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Abstract
The Latent Variable Proximal Point (LVPP) method is a novel, geometry?encoding scheme in which the continuous level informs the algorithms, discretization techniques, and implementation. Mathematically speaking, it embeds the problem at hand into a sequence of related saddle?point problems by introducing a structure?preserving transformation between a latent Banach space and the feasible set. LVPP arises at the confluence of information geometry, optimization, and convex analysis through its use of proximal point methods, Legendre functions, and the isomorphisms induced by their gradients. The method yields algorithms with mesh?independent convergence behaviour for obstacle problems, contact, topology optimization, fracture, plasticity, and more; in many cases, for the first time.
Further Informations
Berlin Oberseminar: Optimization, Control and Inverse Problems
Host
WIAS Berlin
- Wednesday, 17.09.2025, 11:30 (WIAS-405-406)
- Seminar Interacting Random Systems
César Zarco-Romero, WIAS Berlin:
Energy increment on abstract measure spaces
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
A relevant concept in the proof of the weak regularity lemma (as in the original version) is that of the energy of a sigma algebra. We shall first introduce the notion of a semiring together with some examples. We then revisit the classical argument in the proof of the weak regularity lemma in its most abstract sense and from a probabilistic point of view. We shall finally mention a noncommutative martingale convexity inequality from Ricard and Xu (2014) to argue a variant of it on $L^p$ spaces. Applications concern, for instance, large dense graphs, arithmetic progressions, and hypergraphs.
Host
WIAS Berlin
- September 29 – October 1, 2025 (WIAS-ESH)
- Workshop/Konferenz: Mathematical Analysis of Fluid Flows by Variational Methods
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Host
Freie Universität Berlin
Universität Leipzig
WIAS Berlin
- October 8 – 10, 2025 (WIAS-ESH)
- Workshop/Konferenz: Current Research at the Interface of Continuum Physics and Applied Mathematics (in memoriam Wolfgang Dreyer)
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Host
WIAS Berlin
- October 15 – 17, 2025 (WIAS-ESH)
- Workshop/Konferenz: Recent Developments in Spatial Interacting Random Systems
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Host
WIAS Berlin
- Wednesday, 29.10.2025, 11:30 (WIAS-405-406)
- Seminar Interacting Random Systems
Hanna Stange, Universität Münster:
tba
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Host
WIAS Berlin
- November 4 – 6, 2025 (WIAS-ESH)
- Workshop/Konferenz: Mathematics for Smart Energy
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Host
WIAS Berlin
- March 2 – 4, 2026 (IHP)
- Workshop/Konferenz: Leibniz MMS Days 2026
more ... Location
Leibniz Institute for High Performance Microelectronics Frankfurt/Oder
Host
Leibniz Institute for High Performance Microelectronics Frankfurt/Oder
WIAS Berlin