Veranstaltungen

Dienstag, 21.10.2025, 13:30 Uhr (WIAS-406)

Seminar Numerische Mathematik
Hongpeng Li, WIAS Berlin:
Coupling of conforming and mixed finite element methods for a model of wave propagation in thermo-poroelasticity in the frequency domain
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Abstrakt
The thermo-poroelasticity model characterizes the coupling between mechanical deformation, fluid flow, and heat transfer in porous media. As an extension of Biot's classical poroelasticity theory, which models fluid-solid interaction under the isothermal condition, it incorporates the impact of temperature changes on solid displacement, as well as the compressibility and thermal expansion of both solid and fluid phases. We investigate a full-dynamic, linear thermo-poroelasticity model, containing inertial and relaxation terms with second-order time derivatives. The mathematical and numerical analysis of this model is performed in the frequency rather than time domain. We analyze the variational formulation within the framework of Fredholm's alternative and T-coercivity. The well-posedness is rigorously proved under reasonable parameter assumptions. We propose a stabilized coupling of conforming and mixed finite element methods, which are free of volume locking, pressure and temperature oscillations. By incorporating projections in certain sesquilinear forms, the well-posedness of the finite element solutions can be obtained through the same reasoning as in the continuous case. The optimal error estimates are derived for all variables. Numerical experiments validate the accuracy and robustness of our formulation.

Weitere Informationen
Numerical Mathematics

Veranstalter
WIAS Berlin

Mittwoch, 22.10.2025, 10:00 Uhr (WIAS-HVP-3.13)

Forschungsseminar Mathematische Statistik
Prof. Dr. Nina Dörnemann, Universität Aarhus:
Tracy-Widom, Gaussian, and Bootstrap: Approximations for leading eigenvalues in high-dimensional PCA
mehr ... Veranstaltungsort
Weierstraß-Institut, Hausvogteiplatz 11A, 10117 Berlin, 3. Etage, Raum: 3.13

Abstrakt
Under certain conditions, the largest eigenvalue of a sample covariance matrix undergoes a well-known phase transition when the sample size $n$ and data dimension $p$ diverge proportionally. In the subcritical regime, this eigenvalue has fluctuations of order $n^-2/3$ that can be approximated by a Tracy-Widom distribution, while in the supercritical regime, it has fluctuations of order $n^-1/2$ that can be approximated with a Gaussian distribution. However, the statistical problem of determining which regime underlies a given dataset is far from resolved. We develop a new testing framework and procedure to address this problem. In particular, we demonstrate that the procedure has an asymptotically controlled level, and that it is power consistent for certain alternatives. Also, this testing procedure enables the design of a new bootstrap method for approximating the distributions of functionals of the leading sample eigenvalues within the subcritical regime---which is the first such method that is supported by theoretical guarantees. This talk is based on a joint work with Miles E. Lopes (UC Davis).

Weitere Informationen
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

Veranstalter
Humboldt-Universität zu Berlin
Universität Potsdam
WIAS Berlin

Mittwoch, 22.10.2025, 11:30 Uhr (WIAS-405-406)

Seminar Interacting Random Systems
Helia Shafigh, WIAS Berlin:
Responsive dormancy of a spatial population among a moving trap
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Abstrakt
In this talk, we study a spatial model for dormancy in a random environment via a two-type branching random walk in continuous-time, where individuals switch between dormant and active states depending on the current state of a fluctuating environment (responsive switching). The branching mechanism is governed by the same random environment, which is here taken to be a simple symmetric random walk. We will interpret the presence of this random walk as a trap which attempts to kill the individuals whenever it meets them. The responsive switching between the active and dormant state is defined so that active individuals become dormant only when a trap is present at their location and remain active otherwise. Conversely, dormant individuals can only wake up once the environment becomes trap-free again. We quantify the influence of dormancy on population survival by analyzing the long-time asymptotics of the expected population size. The starting point for our mathematical considerations and proofs is the Parabolic Anderson Model via the Feynman-Kac formula. In particular, we investigate the quantitative role of dormancy by extending the Parabolic Anderson Model to a two-type random walk framework.

Joint work with Leo Tyrpak.

Veranstalter
WIAS Berlin

Mittwoch, 22.10.2025, 14:15 Uhr (WIAS-Library)

Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. Annamaria Massimini, Ecole Nationale des Ponts et Chaussées, FR:
Finite volumes for a generalized Poisson--Nernst--Planck system with cross-diffusion
mehr ... Veranstaltungsort
Weierstraß-Institut, Hausvogteiplatz 5-7, 10117 Berlin, R411

Abstrakt
Modeling concentrated ion mixtures in solvents like water is a complex research area with key applications in biology (e.g., ion transport through protein channels) and electrochemistry (e.g., batteries). In this talk, I will present a finite volume scheme for modeling the diffusion of ions in constrained geometries using a degenerate Poisson--Nernst--Planck system with size exclusion yielding cross-diffusion. The proposed method utilizes a two-point flux approximation and is part of the exponentially fitted scheme framework. The scheme is shown to be thermodynamically consistent, as it ensures the decay of some discrete version of the free energy. Classical numerical analysis results - existence of discrete solution, convergence of the scheme as the grid size and the time step go to 0 - follow. The long-time behavior of the scheme is also investigated, both from a theoretical and numerical point of view. Numerical simulations confirm our findings, but also point out some possibly very slow convergence towards equilibrium of the system under consideration. This is a joint work with Clément Cànces and Maxime Herda.

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

Veranstalter
Humboldt-Universität zu Berlin
WIAS Berlin

Mittwoch, 29.10.2025, 10:00 Uhr (WIAS-ESH)

Forschungsseminar Mathematische Statistik
Prof. Dr. Ludgar Overbeck, Justus-Liebig-Universität Gießen:
Bayesian estimation with MCMC methods for stochastic processes with hidden states
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Weitere Informationen
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

Veranstalter
Humboldt-Universität zu Berlin
Universität Potsdam
WIAS Berlin

Mittwoch, 29.10.2025, 11:30 Uhr (WIAS-405-406)

Seminar Interacting Random Systems
Hanna Stange, Universität Münster:
Non-local transport distance for point processes
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406

Abstrakt
We introduce a non-local transport distance on the space of point processes and analyse the induced geometry. We show -- among other things -- that the Ornstein--Uhlenbeck semigroup is the gradient flow of the specific relative entropy, functional inequalities like a Talagrand inequality, and exponential convergence of the Ornstein--Uhlenbeck flow to the Poisson point process. Towards the end, we discuss ongoing work on the extension of the framework adapted to Papangelou point processes. Based on joint work with Martin Huesmann and Matthias Erbar.

Veranstalter
WIAS Berlin

4. – 6. November 2025 (WIAS-ESH)

Workshop/Konferenz: Mathematics for Smart Energy
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Veranstalter
WIAS Berlin

Mittwoch, 19.11.2025, 14:15 Uhr (WIAS-ESH)

Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. Lutz Recke, Humboldt-Universität zu Berlin:
An H-convergence-based implicit function theorem and homogenization of nonlinear non-smooth elliptic systems
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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

Veranstalter
Humboldt-Universität zu Berlin
WIAS Berlin

Donnerstag, 20.11.2025, 14:00 Uhr (WIAS-406)

Seminar Materialmodellierung
Dr. Andrea Giudici, University of Oxford, GB:
From particle stresses to electrolyte flow: How mechanics affects the performance of lithium-ion batteries
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Abstrakt
Lithium-ion batteries are typically described by electrochemical models, yet mechanical effects play a decisive role in their operation and degradation. During cycling, swelling of active particles generates stresses and deformations that propagate across scales. These mechanical effects couple back into electrochemistry in two distinct ways.First, stresses around active particles modify lithium transport by altering the local chemical potential, leading to shifts in voltage curves that cannot be captured by standard Doyle?Fuller?Newman-type models. Using asymptotic homogenisation, we extend reduced-order models to incorporate this multiscale coupling systematically.Second, electrode swelling changes porosity and drives electrolyte flows. These flows interact with concentration gradients, causing an irreversible redistribution of electrolyte salt?typically bulk accumulation and edge depletion?conditions that promote lithium plating and performance loss. We model the flow-concentration coupling and derive a closed-form expression for the resulting electrolyte-movement-induced salt inhomogeneity (EMSI) in terms of swelling, porosity, permeability, and nonlinear mechanics, providing a mechanistic explanation of this degradation pathway.

Weitere Informationen
Material Modeling Seminar

Veranstalter
WIAS Berlin

12. – 13. Januar 2026 (WIAS-ESH)

Workshop/Konferenz: Recent Trends in Coupled Network Systems
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Veranstalter
WIAS Berlin

2. – 4. März 2026 (IHP)

Workshop/Konferenz: Leibniz MMS Days 2026
mehr ... Veranstaltungsort
Leibniz Institute for High Performance Microelectronics Frankfurt/Oder

Veranstalter
Leibniz Institute for High Performance Microelectronics Frankfurt/Oder
WIAS Berlin

1. – 5. Juni 2026 (WIAS-ESH)

Workshop/Konferenz: ESGI 194 - The Berlin Study Group with Industry
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Veranstalter
WIAS Berlin