Upcoming Events (Archive)
- January 29 – 31, 2025 (WIAS-405-406)
- Workshop/Konferenz: Critical behaviour in spatial particle systems
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Host
WIAS Berlin
- Wednesday, 22.01.2025, 14:00 (WIAS-405-406)
- Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Prof. Dr. Jan-Frederik Pietschmann, Universität Augsburg:
Gradient flows on metric graphs with reservoirs
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
We study an evolution equation on metric graphs with reservoirs, that is graphs where a one-dimensional interval is associated to each edge and, in addition, the vertices are able to store mass. We focus on the case then the dynamics is driven by an entropy functional, defined both on edges and vertices. We provide a rigorous understanding of such equations as a gradient flow (in continuity equation format) with respect to metric that allows for a coupling between edge and vertex dynamics. By approximating the edges by a sequence of vertices, resulting in a fully discrete system, we are able to establish existence of solutions in this formalism. Next, we study several scaling limits and using in the framework of EDP convergence with embedding we are able to rigorously show convergence to again gradient flows on reduced graphs. Finally, numerical studies confirm our theoretical findings.
Further Informations
Oberseminar “Nichtlineare Partielle Differentialgleichungen” (Langenbach Seminar)
Host
Humboldt-Universität zu Berlin
WIAS Berlin
- Wednesday, 15.01.2025, 10:00 (WIAS-ESH)
- Forschungsseminar Mathematische Statistik
Xiaorui Zuo, National University of Singapore:
Cryptos have rough volatility and correlated jumps
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal
Further Informations
Dieser Vortrag findet hybrid statt. Die Teilnahme per Zoom ist über den (neuen!) Link: https://hu-berlin.zoom-x.de/j/62476510180?pwd=1bws9DORlDM2Iub3ANrb7zzDNANvsJ.1
Host
Humboldt-Universität zu Berlin
Universität Potsdam
WIAS Berlin
- Tuesday, 14.01.2025, 13:30 (WIAS-405-406)
- Seminar Numerische Mathematik
Prof. Dr. Jinchao Xu, King Abdullah University of Science and Technology:
Finite neuron methods for partial differential equations
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
In this talk, I will report several theoretical and numerical studies of finite neuron method for partial differential equations. Topics include approximation properties of neural network functions, error estimates for the finite neuron method, convergence analysis of training algorithms, the relationship between ReLU^k finite neuron method with the tradition finite element and spectral method, and the comparison of their efficiency for high dimensional problems.
Host
WIAS Berlin
- January 13, 2025 (WIAS-Library)
- Workshop/Konferenz: MATh.en.JEANS - Workshop von und für Schüler:innen
more ... Location
Weierstraß-Institut, Hausvogteiplatz 5-7, 10117 Berlin, R411
Host
WIAS Berlin
- Wednesday, 08.01.2025, 15:15 (WIAS-405-406)
- Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. Joachim Rehberg, WIAS Berlin:
Estimates for operator functions
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Raum: 405/406
Abstract
In several branches of mathematics and mathematical physics estimates for operator functions are of high interest. On one hand, this is the case in quantum chemistry, in particular in the analysis of the Kohn--Sham system. Here we present an elementary proof of the Birman--Solomyak theorem - which was an open problem for a long time. The second item of the talk affects operator functions for second order divergence operators. We give an impoved estimate for the angle of the sector which contains the numerical range and draw several consequences of this.
Further Informations
Berliner Oberseminar “Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Host
Humboldt-Universität zu Berlin
WIAS Berlin
- Wednesday, 08.01.2025, 10:00 (WIAS-HVP-3.13)
- Forschungsseminar Mathematische Statistik
Prof. Dr. Johannes Schmidt-Hieber, University of Twente:
Statistical stimation using zeroth-order optimization
more ... Location
Weierstraß-Institut, Hausvogteiplatz 11A, 10117 Berlin, 3. Etage, Raum: 3.13
Abstract
In this talk, we study statistical properties of zeroth-order optimization schemes, which do not have access to the gradient of the loss and rely solely on evaluating the loss function. Such methods are often considered to be suboptimal for high-dimensional problems, as their convergence rates to the minimizer of the objective function are typically slower than those of gradient-based methods. This performance gap becomes more pronounced as the number of parameters increases. Considering the linear model, we show that reusing the same data point for multiple zeroth-order updates can overcome the gap in the estimation rates. Additionally, we demonstrate that zeroth-order optimization methods can achieve the optimal estimation rate when only queries from the linear regression model are available. Special attention will be given to the non-standard minimax lower bound in the query model. This is joint work with Thijs Bos, Niklas Dexheimer and Wouter Koolen.
Further Informations
Dieser Vortrag findet hybrid statt. Die Teilnahme per Zoom ist über den (neuen!) Link: https://hu-berlin.zoom-x.de/j/62476510180?pwd=1bws9DORlDM2Iub3ANrb7zzDNANvsJ.1
Host
Humboldt-Universität zu Berlin
Universität Potsdam
WIAS Berlin
- Tuesday, 17.12.2024, 14:00 (WIAS-Library)
- Joint Research Seminar on Nonsmooth Variational Problems and Operator Equations / Mathematical Optimization
Marcelo Bongarti, WIAS Berlin:
Multi-objective optimization with linear hyperbolic PDE constraints: generalized Nash equilibrium problems and gas market applications
more ... Location
Weierstraß-Institut, Hausvogteiplatz 5-7, 10117 Berlin, R411
Abstract
The concept of Nash equilibrium is fundamental to a wide range of applications, spanning fields from particle mechanics to micro and macroeconomics. However, much of the existing literature focuses on finite-dimensional settings. In this seminar, we draw on energy markets coupled with transport dynamics to motivate the study of multi-objective optimization problems with hyperbolic PDE constraints. We will explore the core ideas and challenges posed by generalized Nash equilibrium problems, particularly those related to dimensionality and regularity. Finally, we present some recent results on the existence and characterization of equilibria, emphasizing optimality conditions as a framework for understanding such solutions.
Further Informations
Joint Research Seminar on Nonsmooth Variational Problems and Operator Equations
Host
WIAS Berlin
