Upcoming Events

June 16 – 18, 2025 (WIAS-ESH)

Workshop/Konferenz: Nonlinear Dynamics in Semiconductor Lasers 2025
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
WIAS Berlin

Tuesday, 17.06.2025, 13:30 (WIAS-405-406)

Seminar Numerische Mathematik
Prof. Dr. Raimund Bürger, Universidad de Concepción, Chile:
Numerical solution of multispecies kinematic flow models through invariant-region-preserving WENO schemes
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Abstract
Multispecies kinematic flow models are defined by systems of N strongly coupled, nonlinear first-order conservation laws, where the solution is a vector of N partial volume fractions or densities. The solution vector should take values in a set of physically relevant values (i.e., the components are nonnegative and sum up at most to a given maximum value). In the 1D case, it is shown that this set, the so-called invariant region, is preserved by numerical solutions produced by a new family of high-order finite volume numerical schemes adapted to this class of models [J. Barajas-Calonge, R. Bürger, P. Mulet and L.M. Villada, Invariant-region-preserving WENO schemes for one-dimensional multispecies kinematic flow models, J. Comput. Phys. 537 (2025), article 114081]. To achieve this property, and motivated by [X. Zhang, C.-W. Shu, On maximum-principle-satisfying high order schemes for scalar conserva- tion laws, J. Comput. Phys. 229 (2010) 3091-3120], a pair of linear scaling limiters is applied to a high-order weighted essentially non-oscillatory (CWENO) polynomial reconstruction [D. Levy, G. Puppo G. Russo, Central WENO schemes for hyperbolic systems of conservation laws, ESAIM: Math. Model. Numer. Anal. 33 (1999) 547-571] to obtain invariant-region-preserving (IRP) high-order polynomial reconstructions. These reconstructions are combined with a first-order numerical flux to obtain a high-order numerical scheme for the system of conservation laws. It is proved that this scheme satisfies an IRP property under a suitable CFL condition. For the 2D case, we study a polydisperse sedimentation model consisting in a system of conservation laws coupled with a Stokes problem describing the velocity of the mixture. We propose a second-order IRP WENO scheme for the numerical approximation. The theoretical analysis is corroborated with numerical simulations in some scenarios of interest. This presentation is based on joint work with Juan Barajas-Calonge and Luis Miguel Villada (Universidad del Bío-Bío, Concepción, Chile) and Pep Mulet (Universitat de València, Spain)

Host
WIAS Berlin

Tuesday, 17.06.2025, 15:00 (WIAS-405-406)

Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Dr. Alexey Kroshnin, WIAS Berlin:
Optimal rates of uniform approximation of additive time functionals of diffusion processes
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Abstract
We consider the uniform discrete approximation error of an additive time functional $int_0^1 f(X_t) d t$ of a d-dimensional Itô diffusion $(X_t)_t$. We obtain bounds on the expected error for Hölder functions as the number of discretization points grows. Notably, there are two regimes in the one-dimensional case, depending on the Hölder exponent, but only one in higher dimensions. Furthermore, on the example of Brownian motion, we show that these bounds are tight. Based on a joint work with Oleg Butkovsky and Antoine Grenier.

Further Informations
Dieser Vortrag findet auch via Zoom statt: https://zoom.us/j/492088715

Host
WIAS Berlin

Wednesday, 18.06.2025, 10:00 (WIAS-HVP-3.13)

Forschungsseminar Mathematische Statistik
PhD Lasse Vuursteen, University of Pennsylvania, USA:
Adaptive estimation under differential privacy constraints
more ... Location
Weierstraß-Institut, Hausvogteiplatz 11A, 10117 Berlin, 3. Etage, Raum: 3.13

Abstract
Estimation guarantees in nonparametric models typically depend on underlying function classes (or hyper- parameters) that are seldom known in practice. Adaptive estimators provide simultaneous near-optimal performance across multiple such function classes. In this talk, I will discuss recent work with co-authors Tony Cai and Abhinav Chakraborty, in which we study adaptation under differential privacy constraints. Differential privacy fundamentally limits the information that can be revealed about each individual datum by each data holder. We develop a general theory for adaptation under differential privacy in the context of estimating linear functionals of a density. Our framework characterizes the difficulty of private adaptation problems through a specific "between-class modulus of continuity" that exactly describes the optimal achievable performance for private estimators that must adapt across two or more function classes. Our theory reveals and quantifies the extent to which adaptation between specific function classes suffers as a consequence of imposing differential privacy constraints.

Further Informations
Dieser Vortrag findet hybrid statt. Die Teilnahme per Zoom ist über den (neuen!) Link:
https://hu-berlin.zoom-x.de/j/64809417303?pwd=iLT5xbdDZspAcUCuLrwNnaN90ZQBpj.1
Meeting-ID: 648 0941 7303
Passwort: 258449

Host
Humboldt-Universität zu Berlin
Universität Potsdam
WIAS Berlin

Thursday, 19.06.2025, 14:00 (WIAS-405-406)

Seminar Materialmodellierung
Dr. Nadire Nayir, Paul-Drude-Institut für Festkörperelektronik:
From equations to materials: The logic of modeling thin film growth
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Abstract
The synthesis of technologically vital thin films presents complex, multiscale challenges that lie at the intersection of physics, chemistry, and increasingly, mathematics. As materials science progresses toward predictive design and precise control of growth processes, mathematical modeling has become indispensable for understanding how microscopic rules shape macroscopic behavior. With a particular emphasis on simulation techniques rooted in quantum mechanics and Newtonian mechanics, in this talk, I will explain how atomic interactions are described mathematically -- starting from basic concepts like interatomic forces and potential energy surfaces, and moving toward how these are used in time-evolution schemes to simulate atomic motion. These elements form the foundation of computational models that help us understand key processes in thin film growth, such as how nuclei form, how domains align and grow, and how defects emerge and evolve on a substrate. To connect further these atomic-scale models with experimentally observable behavior, we will then turn to multiscale modeling, which provides a systematic way to combine different levels of description. I will show how we link atomistic simulations with continuum methods -- including phase-field models which describe morphological evolution and domain coarsening, and computational fluid dynamics, which captures macroscopic transport phenomena in the growth environment (as in chemical vapor deposition or hybrid molecular beam epitaxy). At this stage, I will walk through how they are coupled together to form an integrated, multiscale modeling framework. By grounding simulation techniques in their mathematical origins, this talk aims to provide a deeper understanding of how theoretical models mirror real-world materials behavior. Ultimately, I hope to show how mathematics not only powers atomistic simulations but also serves as a conceptual bridge between fundamental physics and the technological development of advanced materials.

Further Informations
Seminar Materialmodellierung

Host
WIAS Berlin

June 23 – 26, 2025 (Harnack-Haus)

Workshop/Konferenz: 4th Annual Conference of SPP 2265 Random Geometric Systems 2025
more ... Location
Harnack-Haus -- Tagungsstätte der Max-Planck-Gesellschaft

Host
WIAS Berlin

Tuesday, 24.06.2025, 15:00 (WIAS-405-406)

Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Sorelle Murielle Toukam, WIAS Berlin:
Expected signature of diffusion processes
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Further Informations
Dieser Vortrag findet auch via Zoom statt: https://zoom.us/j/492088715

Host
WIAS Berlin

Wednesday, 25.06.2025, 14:15 (WIAS-405-406)

Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Prof. Dr. Tomáš Roubíček, Czech Academy of Sciences, Tschechische Republik:
Brief notes about Earth's atmosphere energy budget, entropy, climate, and CO2 emissions
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Abstract
The goal of this talk is to present some of the less commonly discussed findings and connections in the atmospheric-emissions-climate field from a non-expert perspective. First, the basic physics of the Earth's atmosphere relevant to the climate, energy balance, and Erwin Schrödinger's idea of the role of negative entropy for the existence of life in open thermodynamic systems will be briefly surveyed. Then the presentation will focus on CO2 in the Earth's atmosphere, including e.g. Svante Arrhenius' historical idea of the greenhouse effect due to CO2. In particular, the development of CO2 concentration and temperature in geological time horizons will be mentioned, as well as recent Antarctic research and their reflection in climate-environmental activism (Al Gore etc). Finally, selected facts about the modern development of anthropogenic CO2 emissions in a socio-economic context will be presented, together how the atmospheric CO2 concentration can be predicted in a very simplified (and approximative) way in the near future in dependence on implementation of the Paris climatic agreement.

Further Informations
Oberseminar “Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)

Host
Humboldt-Universität zu Berlin
WIAS Berlin

Tuesday, 01.07.2025, 15:00 (WIAS-405-406)

Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Dr. Helena Kremp, WIAS Berlin:
Overcoming the order barrier for approximations of nonlinear SPDEs with additive space-time white noise
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Further Informations
Dieser Vortrag findet auch via Zoom statt: https://zoom.us/j/492088715

Host
WIAS Berlin

Wednesday, 09.07.2025, 14:15 (WIAS-ESH)

Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Prof. Dr. Amru Hussein, Universität Kassel:
The three limits of the hydrostatic approximation
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
The primitive equations are a large scale model for ocean and atmosphere. Formally, they are derived from the 3D-Navier--Stokes equations by the assumption of a hydrostatic balance. This can be formalized by a rescaling procedure on an $varepsilon$-thin domain where one considers anisotropic viscosities with vertical viscosity $varepsilon^gamma$ and $varepsilon$-independent horizontal viscosity. Now, the choice of the order $gamma$ leads to different limit equations:
For $gamma=2$, one obtains the primitive equations with full viscosity term $-Delta$;
For $gamma>2$, one obtains the primitive equations with only horizontal viscosity term $- Delta_H$;
For $gamma <2$, one obtains the 2D Navier-Stokes equations.
Thus, there are three possible limits of the hydrostatic approximation depending on the assumption on the vertical viscosity. Here, we show how maximal regularity methods and quadratic inequalities - reminiscent of the Fujita-Kato methods - can be an efficient approach to prove norm-convergences in all three cases. This is a joint work with Ken Furukawa, Yoshikazu Giga, Matthias Hieber, Takahito Kashiwabara, and Marc Wrona, see https://arxiv.org/abs/2312.03418 for a preprint.

Further Informations
Oberseminar “Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)

Host
Humboldt-Universität zu Berlin
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 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

November 3 – 7, 2025 (WIAS-Library)

Workshop/Konferenz:
more ... Location
Weierstraß-Institut, Hausvogteiplatz 5-7, 10117 Berlin, R411

Abstract
The ARISE project (Analysis of Robust Numerical Solvers for Innovative Semiconductors in View of Energy Transition) brings together the RAPSODI team at Inria Lille and the NUMSEMIC team at WIAS Berlin. It focuses on developing advanced mathematical and numerical models for drift-diffusion models for charge transport with mobile ions, with applications for novel semiconductor devices such as perovskite solar cells and memristors, as well as ionic solutions or corrosion phenomena.

Host
WIAS Berlin