Veranstaltungen

Dienstag, 28.01.2025, 13:30 Uhr (HU Berlin HVP)

Berlin Oberseminar: Optimization, Control and Inverse Problems
Prof. Steven Rayan, Department of Mathematics & Statistics, University of Saskatchewan:
A snapshot of mathematics in the second quantum revolution
mehr ... Veranstaltungsort
Humboldt-Universität zu Berlin, Hausvogteiplatz 5-7, R. 0007

Abstrakt
We are in the midst of an exciting revolution in quantum science and technology, comparable in ways to the first one that occurred about 100 years ago. One of the most tantalizing and potentially disruptive innovations to emerge from this second revolution is the prospect of quantum computing. Serious attempts in both academia and industry to design practical quantum computers are pushing physical materials to their extremes. The rise of quantum materials, influenced in part by these attempts, has involved new perspectives and tools not only from physics, chemistry, and material science, but also from mathematics - and not only applied mathematics, but also pure mathematics. I will discuss my work over the past half decade in using ideas from pure mathematics to anticipate new models of quantum materials as well as new paradigms for programming quantum devices that would result from these materials. I will explain, with lots of pictures, not only the mathematical and scientific ideas here, but also how the path to fabrication and actualization has led to exciting interdisciplinary collaborations between mathematics and other sciences and between academia and industry.

Veranstalter
WIAS Berlin

Dienstag, 28.01.2025, 15:00 Uhr (WIAS-405-406)

Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Luca Pelizzari, WIAS Berlin:
Polynomial Volterra processes: Moments and stochastic invariance
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Weitere Informationen
Dieser Vortrag findet auch via Zoom statt: https://zoom.us/j/492088715

Veranstalter
WIAS Berlin

29. – 31. Januar 2025 (WIAS-405-406)

Workshop/Konferenz: Critical behaviour in spatial particle systems
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Veranstalter
WIAS Berlin

Mittwoch, 29.01.2025, 10:00 Uhr (WIAS-HVP-3.13)

Forschungsseminar Mathematische Statistik
Prof. Dr. Davy Paindaveine, Université Libre de Bruxelles, Belgien:
Rank tests for PCA under weak identifiability
mehr ... Veranstaltungsort
Weierstraß-Institut, Hausvogteiplatz 11A, 10117 Berlin, 3. Etage, Raum: 3.13

Weitere Informationen
Dieser Vortrag findet hybrid statt. Die Teilnahme per Zoom ist über den (neuen!) Link: https://hu-berlin.zoom-x.de/j/62476510180?pwd=1bws9DORlDM2Iub3ANrb7zzDNANvsJ.1

Veranstalter
Humboldt-Universität zu Berlin
Universität Potsdam
WIAS Berlin

Mittwoch, 29.01.2025, 10:30 Uhr (WIAS-405-406)

Seminar Interacting Random Systems
Anh Duc Vu, WIAS Berlin:
Basics on random walks and electrical networks
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Abstrakt
The talk aims to give a low-level introduction to random walks on certain graphs and how they are intricately linked to physical quantities in electrical networks. Edges in the graph are assigned conductances which govern the rate at which the random walk traverses said edge. We will see that this model has nice intuitive interpretations in the framework of electrical networks and explore some milestone results, e.g. Solomon's "random walks in random environment" from 1975.

Veranstalter
WIAS Berlin

Mittwoch, 05.02.2025, 15:15 Uhr (WIAS-405-406)

Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Ass. Prof. Sebastian Schwarzacher, Uppsala University, Schweden:
Time-periodic solutions for fluid-solid interactions
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Abstrakt
I will discuss several recent analytic discoveries and numerical experiments about the appearance of time-periodic motions when fluids interact with solids. On one hand, I will present abstract results on the existence and uniqueness of solutions when a parabolic PDE interacts with a hyperbolic PDE. In this setting, geometric conditions will be explored that allow for unique solutions and, as such, exclude hyperbolic resonances. Additionally, I will discuss some results for deformable shells interacting with fluids. On the other hand, I will show numerical experiments related to the appearance of bifurcations in the Navier-Stokes equations, known as the von Karman vortex street. The work presented was established in collaboration with J. Cach, C. Midnrila, S. Mosny, B. Muha, K. Tuma, and J. Webster.

Weitere Informationen
Oberseminar “Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)

Veranstalter
Humboldt-Universität zu Berlin
WIAS Berlin

Dienstag, 11.02.2025, 12:00 Uhr (WIAS-405-406)

Seminar Interacting Random Systems
Benedikt Jahnel, WIAS Berlin and TU Braunschweig:
Basics on random walks and electrical networks
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Veranstalter
WIAS Berlin

12. – 13. Februar 2025 (WIAS-405-406)

Workshop/Konferenz: Joint RICAM WIAS Workshop
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Veranstalter
WIAS Berlin
Johann Radon Institute for Computational and Applied Mathematics

Mittwoch, 12.02.2025, 15:15 Uhr (WIAS-Library)

Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Prof. Dr. André Schlichting, Universität Ulm:
Breakdown of the mean-field description of interacting systems: Phase transitions, metastability and coarsening
mehr ... Veranstaltungsort
Weierstraß-Institut, Hausvogteiplatz 5-7, 10117 Berlin, R411

Abstrakt
We present results concerning the qualitative and quantitative description of interacting systems, with particular emphasis on those possessing a phase transition under the change of relevant system parameters. For this, we first discuss and identify continuous and discontinuous phase for mean-field limits of interacting particle systems on the torus and spheres. Since phase transitions are intimately related to the metastability of the stochastic particle system, we show how a suitable mountain pass theorem in the space of probability measures can describe the metastable behaviour of the underlying finite particle system. We also argue that the mean-field description of the particle system in the regime of strong local interaction has to break down. In this regime, coarsening is observed, where smaller clusters grow through coagulation events. We provide numerical experiments with a positivity preserving numerical scheme for a SPDE of Dean-Kawasaki type, consisting of the McKean-Vlasov equation and conservative noise. Joint works with Nicolai Gerber (U Ulm), Rishabh Gvalani (ETH Zürich), Greg Pavliotis (Imperial London) and Anna Shalova (TU Eindhoven).

Weitere Informationen
Oberseminar “Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)

Veranstalter
Humboldt-Universität zu Berlin
WIAS Berlin

Donnerstag, 20.02.2025, 10:15 Uhr (WIAS-405-406)

Seminar Nichtlineare Optimierung und Inverse Probleme
Prof. Dr. Giulio Schimperna, Università degli Studi di Pavia, Italien:
Some results on a modified Cahn-Hilliard model with chemotaxis
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Abstrakt
We will present some mathematical results for a new model coupling the Cahn-Hilllard system with an evolutionary equation describing the active (chemotactic) transport of a chemical species influencing the phase separation process. Specifically, the model may arise in connection with tumor growth processes; mathematically speaking, it may be interesting in itself as it provides a new coupling between a Keller-Segel-like relation (the equation describing the evolution of the concentration of the chemical substance) and a fourth order (rather than a second order as in most models for chemotaxis) evolutionary system. Our main result will be devoted to proving existence of weak solutions in the case when the chemotaxis sensitivity function has a controlled growth at infinity; a particular emphasis will be given to discussing the occurrence of critical exponents and to presenting a regularization scheme compatible with the a-priori estimates. Moreover, we will discuss an extension of the model where the effects of a macroscopic velocity flow of Brinkman type are taken into account and analyze the Darcy limit regime. Finally, referring to the (more difficult) case of linear chemotactic sensitivity we will shortly present some work in progress, in collaboration with Elisabetta Rocca (Pavia) and Robert Lasarzik (WIAS), related to the existence of very weak solutions as well as weak-strong uniqueness.

Veranstalter
WIAS Berlin

Donnerstag, 27.02.2025, 14:00 Uhr (WIAS-405-406)

Seminar Numerische Mathematik
Dr. El-Houssaine Quenjel, La Rochelle Université:
Stable finite volume methods for transient convection-diffusion systems with anisotropy
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Veranstalter
WIAS Berlin

Donnerstag, 27.03.2025, 14:00 Uhr (WIAS-405-406)

Seminar Numerische Mathematik
Prof. Cornelis Vuik, Delft University of Technology:
Resolving divergence: the first multigrid scheme for the highly indefinite Helmholtz equation using classical components
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Abstrakt
In this talk, we (V. Dwarka and C. Vuik) present the first stand-alone classical multigrid solver for the highly in- definite 2D Helmholtz equation with constant costs per iteration, addressing a longstanding open problem in numerical analysis [1]. Our work covers both large constant and non- constant wavenumbers up to k = 500 in 2D. We obtain a full V - and W -cycle without any level-dependent restrictions. Another powerful feature is that it can be combined with the computationally cheap weighted Jacobi smoother. The key novelty lies in the use of higher-order inter-grid transfer operators [2]. When combined with coarsening on the Complex Shifted Laplacian, rather than the original Helmholtz operator, our solver is h-independent and scales linearly with the wavenumber k. If we use GMRES(3) smoothing we obtain k- independent convergence, and can coarsen on the original Helmholtz operator, as long as the higher-order transfer operators are used. This work opens doors to study robustness of contemporary solvers, such as machine learning solvers inspired by multigrid components, without adding to the black-box complexity.

Veranstalter
WIAS Berlin