Upcoming Events

November 4 – 6, 2025 (WIAS-ESH)

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

Host
WIAS Berlin

Wednesday, 12.11.2025, 11:30 (WIAS-406)

Seminar Interacting Random Systems
Sophia--Marie Mellis, Universität Bielefeld:
Genealogies in multitype populations: branching processes and structured coalescents
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Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Abstract
This talk focuses on the interplay between type and ancestry in two different multitype population models. In the first part, we briefly discuss the long-term behavior of critical multitype branching processes conditioned on survival, both with respect to the forward and the ancestral processes. Despite substantial differences in forward-time behavior and required techniques, their ancestral processes retain key structural similarities to the supercritical case. The main part of the talk then focuses on structured populations divided into $d$ colonies, where individuals migrate at rates proportional to a global scaling parameter $K$. We sample $N(K)$ individuals evenly across colonies and trace their ancestral lineages backward in time. Within each colony, coalescence occurs at a constant rate as in the Kingman coalescent. We encode the system?s state as a $d$-dimensional vector of empirical measures, recording both current lineage locations and the colonies of their sampled descendants. Our focus is on how the sample size affects the asymptotic behavior of this process as $K to infty$ (representing fast migration), distinguishing two regimes: the critical-sampling regime ($N(K) sim K$) and the large-sampling regime ($N(K) gg K$). After suitable time-space rescaling, we prove convergence to $d$-dimensional coagulation equations in both sampling regimes. In the critical regime, the solution admits a representation via a multitype birth-death process; in the large-sample regime, via the entrance law of a multitype Feller diffusion.

Further Informations
Seminar Interactin Random Systems

Host
WIAS Berlin

Wednesday, 12.11.2025, 14:15 (WIAS-ESH)

Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. Leonard Kreutz, Technische Universität München:
Gamma-expansion of the Cahn--Hilliard functional with Dirichlet boundary conditions
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Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
In this talk, we present the second-order asymptotic development of the Cahn--Hilliard functional under Dirichlet boundary conditions via Gamma-convergence. We begin by reviewing results from the literature on the asymptotic expansion of the Cahn--Hilliard functional. Subsequently, we discuss our ongoing research focused on the Cahn--Hilliard functional with Dirichlet boundary conditions. In particular, we examine the case where no interior interfaces are present and highlight several open questions for future investigation. This seminar is based on work in collaboration with Irene Fonseca and Giovanni Leoni.

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

Host
Humboldt-Universität zu Berlin
WIAS Berlin

Wednesday, 19.11.2025, 14:15 (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
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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

Host
Humboldt-Universität zu Berlin
WIAS Berlin

Thursday, 20.11.2025, 14:00 (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
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Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Abstract
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.

Further Informations
Material Modeling Seminar

Host
WIAS Berlin

Wednesday, 26.11.2025, 11:30 (WIAS-406)

Seminar Interacting Random Systems
Anh Duc Vu, WIAS Berlin:
tba
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Host
WIAS Berlin

Wednesday, 26.11.2025, 14:15 (WIAS-ESH)

Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. Illia Karabash, Universität Bonn:
Random boundary conditions for open resonators and the Laplace--Beltrami--Weyl asymptotics
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Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
Motivated by engineering and Photonics research on open resonators in structured deterministic or stochastic environments, the talk introduces rigorous randomizations of absorbing and conservative boundary conditions on Lipschitz boundaries. As underlying PDEs, we choose div-grad acoustic systems, which can be also considered as dimensionally reduced Maxwell equations. We give a description of random m-dissipative boundary conditions that produce acoustic operators with almost surely (a.s.) compact resolvents, and so, also with a.s. discrete spectra, which may be interpreted as stochastic point processes. Based on these results, examples of mathematically convenient randomizations are constructed in terms of eigenfunctions of Laplace--Beltrami operators. It will be shown that, for these special randomizations, the resolvent compactness is connected with the Weyl law on the boundary. If time allows us, the asymptotics of the Laplace--Beltrami eigenvalues on non-smooth boundaries will be also discussed. The talk is based on the paper https://doi.org/10.1016/j.jmaa.2025.129985.

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

Host
Humboldt-Universität zu Berlin
WIAS Berlin

Wednesday, 17.12.2025, 14:15 (WIAS-ESH)

Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. Sebastian Hensel, Universität Leipzig:
A weak-strong uniqueness principle for the Mullins--Sekerka equation
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Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
We establish a weak-strong uniqueness principle for the two-phase Mullins--Sekerka equation in ambient dimension d = 2 and 3: As long as a classical solution to the evolution problem exists, any weak De Giorgi type varifold solution (see for this notion the recent work with Stinson, Arch. Ration. Mech. Anal. 248, 8, 2024) must coincide with it. In particular, in the absence of topology changes such weak solutions do not introduce a mechanism for (unphysical) non-uniqueness. We also derive a stability estimate with respect to changes in the data. I will explain our method which is based on the notion of relative entropies for interface evolution problems, a reduction argument to a perturbative setting, and a stability analysis in this perturbative regime relying crucially on the gradient flow structure of the Mullins--Sekerka equation. This is joint work with Julian Fischer, Tim Laux and Theresa M. Simon.

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

Host
Humboldt-Universität zu Berlin
WIAS Berlin

January 12 – 13, 2026 (WIAS-ESH)

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

Host
WIAS Berlin

March 2 – 4, 2026 (IHP)

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

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

June 1 – 5, 2026 (WIAS-ESH)

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

Host
WIAS Berlin