Upcoming Events

Due to the COVID 19 pandemic, no events are currently taking place on-site at the WIAS until further notice. Many events are organized online instead. Information on how to access these events can be found by clicking “more” below the respective entry.


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Tuesday, 26.05.2020, 15:00 (Online Event)
Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Dr. Alexandra Suvorikova, WIAS Berlin:
Analysis of 3D chromatin structure using Bures-Wasserstein distance
more ... Location
Online Event

Further Informations
Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics

Host
WIAS Berlin
Tuesday, 26.05.2020, 15:15 (Online Event)
Oberseminar Nonlinear Dynamics
Eckehard Schöll, TU Berlin:
Partial synchronization patterns in the brain
more ... Location
Online Event

Further Informations
Diesen Vortrag können Sie mit Zoom verfolgen unter: https://zoom.us/j/89795202774.

Host
Freie Universität Berlin
WIAS Berlin
Technische Universität Berlin
Wednesday, 27.05.2020, 15:15 (Online Event)
Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. Martin Heida, WIAS Berlin:
Stochastic homogenization on randomly perforated domains
more ... Location
Online Event

Host
Humboldt-Universität zu Berlin
WIAS Berlin
Thursday, 28.05.2020, 14:00 (Online Event)
Seminar Numerische Mathematik
Dr. Hang Si, WIAS Berlin:
Detri2, a 2D constrained Delaunay-Voronoi mesh generator
more ... Location
Online Event

Abstract
Detri2 is a C++ program to generate triangular meshes from arbitrary polygonal domains.It uses constrained Delaunay algorithms to conform the input line segments and maintain the locally Delaunay property of the mesh toplogy. It uses Delaunay refinement algorithms to generate meshes with good angle bounds. It can generate adaptive meshes corresponding to input mesh sizing functions. In this talk, I will give a brief tutorial of the basic functionalites of Detri2. I will demonstrate the aglorithms and many of the features of Detri2 using a graphic user interface - Detri2Qt. The source code of Detri2 and Detri2Qt are available at http://www.wias-berlin.de/people/si/detri2.html

Further Informations
For zoom login details please contact Alexander Linke linke@wias-berlin.de

Host
WIAS Berlin
Tuesday, 02.06.2020, 15:00 (Online Event)
Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Dr. Sebastian Riedel, WIAS Berlin:
Runge-Kutta methods for rough differential equations
more ... Location
Online Event

Further Informations
Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics

Host
WIAS Berlin
Wednesday, 03.06.2020, 10:00 (Online Event)
Forschungsseminar Mathematische Statistik
Prof. Ingrid van Keilegom, KU Leuven:
On a semiparametric estimation method for AFT mixture cure models
more ... Location
Online Event

Abstract
When studying survival data in the presence of right censoring, it often happens that a certain proportion of the individuals under study do not experience the event of interest and are considered as cured. The mixture cure model is one of the common models that take this feature into account. It depends on a model for the conditional probability of being cured (called the incidence) and a model for the conditional survival function of the uncured individuals (called the latency). This work considers a logistic model for the incidence and a semiparametric accelerated failure time model for the latency part. The estimation of this model is obtained via the maximization of the semiparametric likelihood, in which the unknown error density is replaced by a kernel estimator based on the Kaplan-Meier estimator of the error distribution. Asymptotic theory for consistency and asymptotic normality of the parameter estimators is provided. Moreover, the proposed estimation method is compared with a method proposed by Lu (2010), which uses a kernel approach based on the EM algorithm to estimate the model parameters. Finally, the new method is applied to data coming from a cancer clinical trial.

Further Informations
Der Vortrag findet bei Zoom statt: https://zoom.us/j/159082384

Host
Humboldt-Universität zu Berlin
WIAS Berlin
Wednesday, 03.06.2020, 15:15 (Online Event)
Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. Thilo Simon, Universität Bonn:
Skyrmions and stability of degree ±1 harmonic maps from the plane to the two-dimensional sphere
more ... Location
Online Event

Abstract
Skyrmions are topologically nontrivial patterns in the magnetization of extremely thin ferromagnets. Typically thought of as stabilized by the so-called Dzyaloshinskii--Moriya interaction (DMI), or antisymmetric exchange interaction, arising in such materials, they are of great interest in the physics community due to possible applications in memory devices. In this talk, I will characterize skyrmions as local minimizers of a two-dimensional limit of the full micromagnetic energy, augmented by DMI and retaining the nonlocal character of the stray field energy. In the regime of dominating Dirichlet energy, I will provide rigorous predictions for their size and ”wall angles”.The main tool is a quantitative stability result for harmonic maps of degree ±1 from the plane to the two-dimensional sphere, relating the energy excess of any competitor to the homogeneous H¹-distance to the closest harmonic map. This is joint work with Cyrill Muratov and Anne Bernard-Mantel.

Host
Humboldt-Universität zu Berlin
WIAS Berlin
Thursday, 04.06.2020, 14:00 (Online Event)
Seminar Numerische Mathematik
Prof. Volker John, WIAS Berlin:
On the provable convergence order for the kinetic energy of FEMs for the incompressible Navier--Stokes equations
more ... Location
Online Event

Abstract
The kinetic energy of a flow is proportional to the square of the L2(Ω) norm of the velocity. Given a sufficient regular velocity field u and a velocity finite element space with polynomials of degree r, then the best approximation error in L2(Ω) is of order r+1. This talk will discuss which order of convergence for the kinetic energy can be proved with robust error estimates, i.e., with estimates where the constant does not depend on inverse powers of the viscosity. To fix ideas, the first part of the talk is devoted to evolutionary scalar convection-diffusion equations. In the second part, results for robust discretizations of the time-dependent incompressible Navier--Stokes equations will be surveyed. This survey covers as well inf-sup stable pairs of finite element spaces as pressure-stabilized discretizations.

Further Informations
For zoom login details please contact Alexander Linke linke@wias-berlin.de

Host
WIAS Berlin
June 8 – 9, 2020 (Online Event)
Workshop/Konferenz: 13th Annual ERC Berlin-Oxford Young Researchers Meeting on Applied Stochastic Analysis
more ... Location
Online Event

Host
Technische Universität Berlin
WIAS Berlin
Tuesday, 09.06.2020, 15:15 (Online Event)
Oberseminar Nonlinear Dynamics
Peter Koltai, FU Berlin:
Reaction coordinates (order parameters) for metastable systems
more ... Location
Online Event

Abstract
We consider non-deterministic dynamical systems showing complex metastable behavior but no local separation in fast and slow coordinates. We raise the question whether and when such systems exhibit a low-dimensional parametrization supporting their effective statistical dynamics. For answering this question, we aim at finding nonlinear coordinates, called reaction coordinates (or order parameters), such that the projection of the dynamics onto these coordinates preserves the dominant time scales of the dynamics. We show that, based on a specific reducibility property, the existence of good low-dimensional reaction coordinates preserving the dominant time scales is guaranteed. Based on this theoretical framework, we develop and test a novel numerical approach for computing good reaction coordinates. The proposed algorithmic approach is fully local and thus less prone to the curse of dimension with respect to the state space of the dynamics than global methods. Hence, it is a promising method for data-based model reduction of complex dynamical systems such as?but not only?molecular dynamics.

Host
Freie Universität Berlin
WIAS Berlin
Wednesday, 10.06.2020, 15:00 (Online Event)
Forschungsseminar Mathematische Statistik
Dr. Jonathan Niles-Weed, New York University:
Minimax estimation of smooth densities in Wasserstein distance
more ... Location
Online Event

Abstract
We study nonparametric density estimation problems where error is measured in the Wasserstein distance, a metric on probability distributions popular in many areas of statistics and machine learning. We give the first minimax-optimal rates for this problem for general Wasserstein distances, and show that, unlike classical nonparametric density estimation, these rates depend on whether the densities in question are bounded below. Motivated by variational problems involving the Wasserstein distance, we also show how to construct discretely supported measures, suitable for computational purposes, which achieve the minimax rates. Our main technical tool is an inequality giving a nearly tight dual characterization of the Wasserstein distances in terms of Besov norms. Joint work with Q. Berthet.

Further Informations
Der Vortrag findet bei Zoom statt: https://zoom.us/j/159082384

Host
Humboldt-Universität zu Berlin
WIAS Berlin
Tuesday, 14.07.2020, 15:15 (Online Event)
Oberseminar Nonlinear Dynamics
Rico Berner, TU Berlin:
From coherence to incoherence: Stability islands in adaptive neuronal networks
more ... Location
Online Event

Host
Freie Universität Berlin
WIAS Berlin
November 2 – 4, 2020 (WIAS-ESH)
Workshop/Konferenz: Workshop on Stochastic Geometry and Communications
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
WIAS Berlin