Upcoming Events
- November 21, 2025 (WIAS-ESH)
- Workshop/Konferenz: CRC Day on Rough Volatility
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Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Host
Humboldt-Universität zu Berlin
WIAS Berlin
- Monday, 24.11.2025, 14:00 (WIAS-ESH)
- Seminar Interacting Random Systems
François Baccelli, Unité de Recherche de Rocquencourt and ENS (Département d'Informatique, Frankreich:
On Dynamical Poisson-Voronoi Tessellations
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Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Abstract
Consider a dynamical network model featuring mobile stations on the Euclidean plane. The initial locations of the stations are given by a homogeneous Poisson point process. The stations are all moving at a constant speed and in a random direction. Consider fixed observers located in the Euclidean plane, which are served by the mobile stations. Each observer stays connected to the nearest station at any given point of time. Since the stations are moving, an observer disconnects and connects with different stations over time, by always selecting which ever station is the closest. This gives rise to a dynamical version of the Poisson-Voronoi tessellation. The focus of this paper is on the sequence of "handover" events of a typical observer, which are the epochs when its association changes. This defines a point process on time axis, the "handover point process". We show that this point process is stationary and we determine its main properties, in particular its intensity and the joint distribution of its inter-event times. We also analyze the handover Palm distributions of several variables of practical interest. This includes the distance to the closest mobile station and the point process of all other mobile stations at handover epochs. The analysis is conducted both in the single-speed and in the multi-speed scenarios. It leads to the identification of the three dimensional state variables that "Markovize" the association dynamics. The analysis is based on a specific system of non-compact particles. The motivations are in the modeling of low or medium orbit satellite wireless communication networks. The model studied here is a planar "caricature" of this problem, which is initially defined on the sphere. Joint work with Sanjoy Kumar Jhawar.
Further Informations
Seminar Interacting random Systems
Host
WIAS Berlin
- Tuesday, 25.11.2025, 14:00 (WIAS-Library)
- Seminar Materialmodellierung
Dr. Ralf Blossey, Université de Lille, Frankreich:
Structural polarization in electrolytes: A continuum approach
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Weierstraß-Institut, Hausvogteiplatz 5-7, 10117 Berlin, R411
Abstract
The standard continuum description of electrolytes is given by Poisson--Boltzmann theory. It describes a structureless solvent with a given dielectric constant (typically around 80, for water), and the dissociated ions by Boltzmann factors. Experimental advances in the past decades, and notably the ever-improving use of atomic force microscopy (AFM) in solution, have opened up new challenges for the mathematical description of electrolytes that require going beyond this basic approach, with numerous putative applications in biology and nanoscience, from biological cells to batteries. In this talk I will describe a recently developed theory of structural polarization forces in electrolytes that combines nonlocal and nonlinear interactions in such systems. After formulating the essential ingredients of this approach, I will discuss the derivation of boundary conditions and highlight some exemplary applications that are currently under way. Recent further developments for metal-solvent interfaces will be also be briefly discussed.
References :
R. Blossey and R. Podgornik, Field theory of structured liquid dielectrics, Phys. Rev. Res. 4, 023033 (2022)
R. Blossey and R. Podgornik, A comprehensive continuum theory of structured liquids, J. Phys. A: Math. Theor. 56 025002 (2023)
Further Informations
Oberseminar “Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Host
WIAS Berlin
- Wednesday, 26.11.2025, 10:00 (WIAS-ESH)
- Forschungsseminar Mathematische Statistik
Alessandro Palummo, Politecnico Milano, Italien:
Physics-informed functional principal component analysis of large-scale datasets
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Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Abstract
Physics-informed statistical learning is an emerging area of spatial and functional data analysis that integrates observational data with prior physical knowledge encoded by partial differential equations (PDEs). We propose an iterative Majorization?Minimization scheme for functional Principal Component Analysis of random fields in a general Hilbert space, formulated under the practically relevant assumption of partial observability of the data. By combining differential penalties with finite element discretizations, our approach recovers smooth principal component functions while preserving the geometric features of the spatial domain. The resulting estimation procedure involves solving a smoothing problem, which may become computationally demanding for large-scale datasets. After establishing the well-posedness of this smoothing problem under mild assumptions on the PDE parameters, we develop an efficient iterative algorithm for its solution. This framework enables the practical analysis of massive functional datasets at the population level, ranging from physics-informed fPCA to functional clustering, with applications to environmental and neuroimaging data.
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
- 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
- Thursday, 27.11.2025, 09:00 (WIAS-Library)
- MATh.en.JEANS
MATh.en.JEANS - SchülerInnen treffen LehrerInnen treffen Forschende
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Weierstraß-Institut, Hausvogteiplatz 5-7, 10117 Berlin, R411
Abstract
MATh.en.JEANS bietet eine einzigartige Lernumgebung, in der Schüler:innen die faszinierende Welt der Mathematik entdecken können. Der Kern des Konzepts liegt darin, Forscher:innen direkt in die Klassenzimmer zu bringen. Diese Zusammenarbeit ermöglicht es den Jugendlichen, Mathematik nicht nur als abstraktes Fach, sondern als lebendige Wissenschaft zu erleben. Sie haben die Chance, reale mathematische Probleme zu erforschen und von Expert:innen zu lernen, während sie ihre eigenen Entdeckungen machen. Diese direkte Interaktion zwischen Schüler:innen und Forschenden schafft eine inspirierende Lernatmosphäre, die das forschende Entdecken anregt und die Begeisterung für Mathematik weckt.
Host
WIAS Berlin
- Tuesday, 02.12.2025, 10:00 (Online Event)
- Joint Research Seminar on Nonsmooth Variational Problems and Operator Equations / Mathematical Optimization
Shida Wang, Universität des Saarlandes:
Convergence rates of regularized quasi-Newton methods without strong convexity (online talk)
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Online Event
Abstract
In this talk, we discuss the convergence rates of the cubic regularized proximal quasi-Newton method for solving non-smooth additive composite problems that satisfy the Kurdyka-Łojasiewicz (KL) property with respect to some desingularizing function, instead of relying on strong convexity. In particular, when the objective function is smooth and satisfies the Polyak-Łojasiewicz (PL) inequality, the algorithm attains a global superlinear convergence. Additionally, we introduce two practical and computationally efficient variants based on limited-memory quasi-Newton techniques.
Further Informations
Joint Research Seminar on Nonsmooth Variational Problems and Operator Equations
Host
WIAS Berlin
- Tuesday, 02.12.2025, 15:00 (WIAS-405-406)
- Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Dr. Davit Gogolashvili, WIAS Berlin:
Local regression on path spaces with signature metrics
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
We study nonparametric regression and classification for path-valued data. We introduce a functional Nadaraya-Watson estimator that combines the signature transform from rough path theory with local kernel regression. The signature transform provides a principled way to encode sequential data through iterated integrals, enabling direct comparison of paths in a natural metric space. Our approach leverages signature-induced distances within the classical kernel regression framework, achieving computational efficiency while avoiding the scalability bottlenecks of large-scale kernel matrix operations. We establish finite-sample convergence bounds demonstrating favorable statistical properties of signature-based distances compared to traditional metrics in infinite-dimensional settings. We propose robust signature variants that provide stability against outliers, enhancing practical performance. Applications to both synthetic and real-world data-including stochastic differential equation learning and time series classification-demonstrate competitive accuracy while offering significant computational advantages over existing methods.
Further Informations
Dieser Vortrag findet auch via Zoom statt: https://wias-berlin-de.zoom-x.de/j/69982487566
Host
WIAS Berlin
- Wednesday, 03.12.2025, 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, 03.12.2025, 14:15 (WIAS-ESH)
- Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Prof. Dr. Alexander Mielke, WIAS Berlin:
A simple approach to the chain rule for gradient systems
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
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
more ... Location
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
- Wednesday, 14.01.2026, 11:30 (WIAS-406)
- Seminar Interacting Random Systems
Marcel Ortgiese, University of Bath:
tba
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)
Abstract
tba
Further Informations
Seminar Interactin Random Systems
Host
WIAS Berlin
- Wednesday, 21.01.2026, 11:30 (WIAS-406)
- Seminar Interacting Random Systems
Yannic Steenbeck, TU Braunschweig:
tba
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)
Abstract
tba
Further Informations
Seminar Interactin Random Systems
Host
WIAS Berlin
- Wednesday, 21.01.2026, 14:15 (WIAS-ESH)
- Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
PD Dr. Olaf Klein, WIAS Berlin:
Uncertainty quantification for a model for a magnetostrictive material involving a hysteresis operator
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Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Host
Humboldt-Universität zu Berlin
WIAS Berlin
- Wednesday, 28.01.2026, 14:15 (WIAS-ESH)
- Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. Anastasija Pešić, WIAS Berlin:
Curvature-driven pattern formation in biomembranes: A gradient flow approach
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Host
Humboldt-Universität zu Berlin
WIAS Berlin
- Wednesday, 11.02.2026, 11:30 (WIAS-406)
- Seminar Interacting Random Systems
Elias Zimmermann, Universität Leipzig:
tba
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)
Abstract
tba
Further Informations
Seminar Interactin Random Systems
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
- July 6 – 8, 2026 (WIAS-ESH)
- Workshop/Konferenz: Spreading Dynamics in Random Environment
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Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Host
WIAS Berlin