Upcoming Events
- Wednesday, 17.12.2025, 10:00 (WIAS-HVP-3.13)
- Forschungsseminar Mathematische Statistik
Dr. Cesare Miglioli, University of Pittsburgh, USA:
Incomplete U-statistics of equireplicate designs: Berry-Esseen bound and efficient construction
more ... Location
Weierstraß-Institut, Hausvogteiplatz 11A, 10117 Berlin, 3. Etage, Raum: 3.13
Abstract
U-statistics are a fundamental class of estimators that generalize the sample mean and underpin much of nonparametric statistics. Although extensively studied in both statistics and probability, key challen- ges remain. These include their inherently high computational cost addressed partly through incomplete U-statistics and their non-standard asymptotic behavior in the degenerate case, which typically requires resampling methods for hypothesis testing. This talk presents a novel perspective on U-statistics, groun- ded in hypergraph theory and combinatorial designs. Our approach bypasses the traditional Hoe?ding decomposition, which is the the main analytical tool in this literature but is highly sensitive to degeneracy. By fully characterizing the dependence structure of a U-statistic, we derive a new Berry-Esseen bound that applies to all incomplete U-statistics based on deterministic designs, yielding conditions under which Gaussian limiting distributions can be established even in the degenerate case and when the order diverges. Moreover, we introduce e cient algorithms to construct incomplete U-statistics of equireplicate designs, a subclass of deterministic designs that, in certain cases, enable to achieve minimum variance. To illustrate the power of this novel framework, we apply it to kernel-based testing, focusing on the widely used two- sample Maximum Mean Discrepancy (MMD) test. Our approach leads to a permutation-free variant of the MMD test that delivers substantial computational gains while retaining statistical validity.
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, 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
- Thursday, 18.12.2025, 11:00 (WIAS-ESH)
- CRC/TRR 388 Winter Lectures
Dr. Alessandra Frabetti, Université Claude Bernard Lyon 1:
Transport maps on manifolds using groupoids and direct connections
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Abstract
In the theory of Regularity Structures, local solutions of (singular and stochastic) PDEs at different points of a base manifold are related by means of some transport maps. On non-flat manifolds, such operators are best described by Lie groupoids, a bi-fibred version of Lie groups where each element has a source and a target point on the manifold. After a short review of two motivating examples, we shall introduce the basic mathematical tools for such a geometric approach: groupoid actions on vector bundles and direct connections on groupoids giving rise to transport maps.
Host
WIAS Berlin
Technische Universität Berlin
- Thursday, 18.12.2025, 14:00 (WIAS-ESH)
- CRC/TRR 388 Winter Lectures
Dr. Alessandra Frabetti, Université Claude Bernard Lyon 1:
Direct connections on jet groupoids and regularity structures
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Abstract
Solutions of PDEs obtained by means of some local Taylor expansion are geometrically naturally described in terms of jet bundles. In order to relate such local solutions, we consider direct connections on jet groupoids. In this talk we shall present a natural jet prolongation of direct connections to jet groupoids. We shall also provide an example of a direct connection on a jet groupoid which does not arise in the context of Regularity Structures.
Host
WIAS Berlin
Technische Universität Berlin
- January 12 – 13, 2026 (WIAS-ESH)
- Workshop/Konferenz: Recent Trends in Coupled Network Systems
more ... Location
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
- Thursday, 15.01.2026, 14:00 (WIAS-405-406)
- Seminar Numerische Mathematik
Prof. Petr Knobloch, Charles University, Tschechische Republik:
Computation of stabilization parameters using machine learning
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
For various types of partial differential equations, standard finite element discretizations are often unstable, which can be cured by adding suitable stabilization terms. Typically, these terms contain user-chosen parameters whose optimal choice is usually not known but which considerably influence the quality of the approximate solution. In this talk, we will consider stabilized methods for steady convection-diffusion equations. A typical example is the streamline upwind Petrov-Galerkin (SUPG) method. It is possible to compute the stabilization parameters a posteriori in an adaptive way by minimizing a target functional characterizing the quality of the approximate solution, however, this functional is often difficult to design. Moreover, the solution of this high-dimensional constrained nonlinear optimization problem is usually very time-consuming. Therefore, we proposed a method based on techniques from machine learning in order to select (nearly) optimal stabilization parameters in a cheap way. The idea is to compute these parameters locally based on properties of the SUPG solution obtained with standard (nonoptimal) parameters. The training phase will use parameters computed by the mentioned minimization approach employing accurate approximate solutions which can be obtained using nonlinear (and hence again costly) approaches. We will report our first experiences with this strategy. This is the joint work with Manoj Prakash (Charles University, Prague).
Further Informations
Seminar Numerical Mathematics
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
more ... Location
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
more ... Location
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
more ... Location
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
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Host
WIAS Berlin