Upcoming Events
Due to infection prevention measures, participation in events at the institute is presently not possible for guests.
Many events are currently organized online. Information on how to access these events can be found by clicking “more” below the respective entry.
- Wednesday, 18.11.2020, 10:00 (Online Event)
- Forschungsseminar Mathematische Statistik
Dr. Matthias Löffler, ETH Zürich:
Computationally efficient sparse clustering
more ... Location
Online Event
Further Informations
Der Vortrag findet bei Zoom statt: https://zoom.us/j/159082384
Host
Humboldt-Universität zu Berlin
WIAS Berlin
- Wednesday, 18.11.2020, 15:15 (Online Event)
- Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. Janusz Ginster, Humboldt-Universität zu Berlin:
On the motion of curved dislocations in three dimensions: Simplified linearized elasticity
more ... Location
Online Event
Abstract
In this talk we discuss a simplified equilibrium problem for a curved dislocation line in a three-dimensional domain. As the core radius tends to zero, we derive an asymptotic expression to characterize the induced elastic energy. We then obtain the force on the dislocation line as the variation of thi sexpression and identify the highest order terms explicitly. As a main ingredient, we present an explicit asymptotic formula for the induced elastic strain which depends on the curvature of the dislocation line and thus highlights the difference to existing work on straight dislocation lines. Eventually, we present results on the corresponding dynamics. The presented methods area blueprint for the more physical setting of linearized isotropic elasticity. This is joint work with I. Fonseca and S. Wojtowytsch.
Host
Humboldt-Universität zu Berlin
WIAS Berlin
- Thursday, 19.11.2020, 15:00 (Online Event)
- TES-Seminar on Energy-based Mathematical Methods and Thermodynamics
Prof. Dr. Christian Wieners, Karlsruher Institut für Technologie:
A discontinuous Galerkin method for phase field approximations of dynamic fracture
more ... Location
Online Event
Abstract
We present a new numerical method for dynamic fracture at small strains which is based on a discontinuous Galerkin approximation of a first order formulation for elastic waves and where the fracture is approximated by a phase field driven by a stress based fracture criterion. The staggered algorithm in time combines the implicit midpoint rule for the wave propagation followed by an implicit Euler step for the phase field evolution. Then, driven by a stress based fracture criterion, the material is degradated, and the waves are reflected at the diffusive interface. Then method is evaluated in detail in one dimension, and then we demonstrate in a 2D application the fracture evolution with multiple fractures initiated by reflections. This is joint work with Kerstin Weinberg, Siegen.
Further Informations
Please register on this link: https://mathplus.de/topic-development-lab/tes-winter-2020-21/tes-seminar-on-energy-based-mathematical-methods-and-thermodynamics/
Host
Technische Universität Berlin
WIAS Berlin
- Thursday, 19.11.2020, 16:00 (Online Event)
- Forschungsseminar Mathematische Modelle der Photonik
Dr. Konstantinos Mamis, Hellenic Naval Academy, Greece:
Formulating nonlinear Fokker--Planck equations for dynamical systems under coloured noise excitation
more ... Location
Online Event
Host
WIAS Berlin
- Tuesday, 24.11.2020, 10:15 (Online Event)
- Seminar Nichtlineare Optimierung und Inverse Probleme
Dr. Sergey Nechayev, Ferdinand-Braun-Institut, Berlin:
Towards LDSL-based multiphysics modeling of semiconductor lasers: Ideals and challenges
more ... Location
Online Event
Further Informations
Diesen Vortrag können Sie mit Zoom verfolgen unter: https://zoom.us/j/98493865627.
Host
WIAS Berlin
- Tuesday, 24.11.2020, 15:00 (Online Event)
- Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Dr. Alexander Gasnikov, WIAS Berlin:
Parallel and distributed algorithms for ML problems
more ... Location
Online Event
Further Informations
Dieser Vortrag findet bei Zoom statt: https://zoom.us/j/492088715
Host
WIAS Berlin
- Wednesday, 25.11.2020, 10:00 (Online Event)
- Forschungsseminar Mathematische Statistik
Dr. Alexander Kreiß, KU Leuven:
Unbiased Markov chain Monte Carlo methods with couplings
more ... Location
Online Event
Abstract
We will consider multivariate stochastic processes indexed either by vertices or pairs of vertices of a dynamic network. Under a dynamic network we understand a network with a fixed vertex set and an edge set which changes randomly over time. We will assume that the spatial dependence-structure of the processes conditional on the network behaves in the following way: Close vertices (or pairs of vertices) are dependent, while we assume that the dependence decreases conditionally on that the distance in the network increases. We make this intuition mathematically precise by considering three concepts based on correlation, beta-mixing with time-varying beta-coefficients and conditional independence. These concepts allow proving weak-dependence results, e.g. an exponential inequality. These results will be useful for studying asymptotic regimes in which the network grows (i.e. the number of vertices tends to infinity) and we can expect that a growing network results in a larger distance between most vertices. Since the network is dynamic we allow that vertices move around the network and come close to different vertices. In order to demonstrate the use of these concepts in an application we study the asymptotics (for growing networks) of a goodness of fit test in a dynamic interaction network model based on a Cox-type model for counting processes. This model is then applied to bike-sharing data.
Further Informations
Der Vortrag findet bei Zoom statt: https://zoom.us/j/159082384
Host
Humboldt-Universität zu Berlin
WIAS Berlin
- Wednesday, 25.11.2020, 11:30 (Online Event)
- Seminar Interacting Random Systems
Willem van Zuijlen:
Total mass asymptotics of the parabolic Anderson model
more ... Location
Online Event
Abstract
e consider the parabolic Anderson model with a white noise potential in two dimensions. This model is also called the stochastic heat equation with a multiplicative noise. We study the large time asymptotics of the total mass of the solution. Due to the irregularity of the white noise, in two dimensions the equation is a priori not well-posed. Using paracontrolled calculus or regularity structures one can make sense of the equation by a renormalisation, which can be thought of as “subtracting infinity of the potential”. To obtain the asymptotics of the total mass we use the spectral decomposition, an alternative Feynman-Kac type representation and heat-kernel estimates which come from joint works with Khalil Chouk, Wolfgang König and Nicolas Perkowski.
Further Informations
Seminar Interacting Random Systems
Host
WIAS Berlin
- Wednesday, 25.11.2020, 15:15 (Online Event)
- Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. Annika Bach, Technische Universität München:
Geometrically frustrated spin systems: The antiferromagnetic XY model on the triangular lattice
more ... Location
Online Event
Abstract
Antiferromagnetic spin systems are magnetic lattice systems in which the exchange interaction between two spins (i.e., vectors in S1) favors anti-alignment. Such systems are said to be geometrically frustrated if, due to the geometry of the lattice, there is no orientation of spins that simultaneously minimizes all pairwise interactions. This is the case for the antiferromagnetic XY model on the two-dimensional triangular lattice. As a consequence, the system has two families of ground states which can be distinguished one from the other by what is called their chirality. In this talk we present a recent result obtained in collaboration with M. Cicales, L. Kreutz, and G. Orlando, where we characterise the discrete-to-continuum Gamma-limit of the XY-model energy in a regime which detects chirality transitions on one-dimensional interfaces between the two admissible chirality phases.
Host
Humboldt-Universität zu Berlin
WIAS Berlin
- Thursday, 26.11.2020, 15:00 (Online Event)
- TES-Seminar on Energy-based Mathematical Methods and Thermodynamics
Prof. Dr. Miroslav Grmela, Polytechnique Montréal:
Multiscale thermodynamics
more ... Location
Online Event
Abstract
Multiscale thermodynamics is a theory of relations among levels of investigation of complex systems. It includes the classical equilibrium thermodynamics as a special case but it is applicable to both static and time evolving processes in externally and internally driven macroscopic systems that are far from equilibrium and are investigated on microscopic, mesoscopic, and macroscopic levels. In this talk we formulate the multiscale thermodynamics, explain its origin, and illustrate it in mesoscopic dynamics that combines levels, see [1] for more details. [1] M. Grmela: Multiscale Thermodynamics. arxiv-preprint 2020.
Further Informations
Please register on this link: https://mathplus.de/topic-development-lab/tes-winter-2020-21/tes-seminar-on-energy-based-mathematical-methods-and-thermodynamics/
Host
Technische Universität Berlin
WIAS Berlin
- Thursday, 26.11.2020, 16:00 (Online Event)
- Forschungsseminar Mathematische Modelle der Photonik
Regina Finsterhölzl, TU Berlin:
Applying feedback control on quantum many-body systems within the matrix-product-state framework
more ... Location
Online Event
Host
WIAS Berlin
- Tuesday, 01.12.2020, 15:00 (Online Event)
- Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Roman Kravchenko, Humboldt-Universität zu Berlin:
Distributed optimization with quantization for computing Wasserstein barycenters
more ... Location
Online Event
Further Informations
Dieser Vortrag findet bei Zoom statt: https://zoom.us/j/492088715
Host
WIAS Berlin
- Tuesday, 08.12.2020, 15:00 (Online Event)
- Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Dr. Pavel Dvurechensky, WIAS Berlin:
Accelerated alternating minimization methods
more ... Location
Online Event
Abstract
We combine alternating minimization (AM) and Nesterov-type momentum acceleration and propose a generic accelerated alternating minimization method with a $1/k^2$ convergence rate in terms of the objective for convex problems and $1/k$ in terms of the squared gradient norm for non-convex problems, where $k$ is the iteration counter. Our method does not require any knowledge of neither convexity of the problem nor function parameters such as smoothness constant, i.e. it is adaptive to convexity and smoothness. Further, we develop its primal-dual modification for convex problems with linear constraints. We consider two applications of our methods to highlight their properties. The first one is the non-convex collaborative filtering problem, and the second one is optimal transport, where our primal-dual method takes a form of accelerated Sinkhorn's algorithm or accelerated Iterative Bregman Projections algorithm. In both applications, we show numerically that our methods outperform the baselines. In the second application, we also obtain state-of-the-art complexity results for optimal transport problems.
Further Informations
Dieser Vortrag findet bei Zoom statt: https://zoom.us/j/492088715
Host
WIAS Berlin
- Wednesday, 09.12.2020, 11:30 (Online Event)
- Seminar Interacting Random Systems
Robert Patterson:
tba
more ... Location
Online Event
Further Informations
Seminar Interacting Random Systems
Host
WIAS Berlin