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.


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Tuesday, 20.04.2021, 15:00 (Online Event)
Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Dr. Caroline Geiersbach, WIAS Berlin:
Stochastic approximation with applications to PDE-constrained optimization under uncertainty (online talk)
more ... Location
Online Event

Further Informations
Dieser Vortrag findet bei Zoom statt: https://zoom.us/j/492088715

Host
WIAS Berlin
Tuesday, 20.04.2021, 15:15 (Online Event)
Oberseminar Nonlinear Dynamics
Alan Rendall, Johannes Gutenberg-Universität Mainz:
Bogdanov--Takens bifurcations and the regulation of enzymatic activity by autophosphorylation
more ... Location
Online Event

Abstract
An important mechanism of information storage in molecular biology is the binding of phosphate groups to proteins. In this talk we consider the case of autophosphorylation, where the protein is an enzyme and the substrate to which it catalyses the binding of a phosphate group is that enzyme itself. It turns out that this often leads to more complicated dynamics than those seen in the case where enzyme and substrate are distinct. We focus on the example of the enzyme Lck (lymphocyte-associated tyrosine kinase) which is of central importance in the function of immune cells. We study a model for the activation of Lck due to Kaimachnikov and Kholodenko and give a rigorous proof that it admits periodic solutions. We do so by showing that it exhibits a generic Bogdanov-Takens bifurcation. This is an example where this approach gives a simpler proof of the existence of periodic solutions than ones

Further Informations
Diesen Vortrag können Sie mit Zoom verfolgen unter: https://zoom.us/j/84203723799.

Host
Freie Universität Berlin
WIAS Berlin
Wednesday, 21.04.2021, 09:00 (Online Event)
Forschungsseminar Mathematische Statistik
Prof. Hans-Georg Müller, University of California, Davis, USA:
Functional models for time-varying random objects (online talk)
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Online Event

Abstract
In recent years, samples of random objects and time-varying object data such as time-varying distributions or networks that are not in a vector space have become increasingly prevalent. Such data can be viewed as elements of a general metric space that lacks local or global linear structure. Common approaches that have been used with great success for the analysis of functional data, such as functional principal component analysis, are therefore not applicable. The concept of metric covariance makes it possible to define a metric auto-covariance function for a sample of random curves that take values in a general metric space and it can be shown to be non-negative definite when the squared semi-metric of the underlying space is of negative type. Then the eigenfunctions of the linear operator with the auto-covariance function as kernel can be used as building blocks for an object functional principal component analysis, which includes real-valued Frechet scores and metric-space valued object functional principal components. Sample based estimates of these quantities are shown to be asymptotically consistent and are illustrated with various data. (Joint work with Paromita Dubey, Stanford University.)

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

Host
Humboldt-Universität zu Berlin
WIAS Berlin
Wednesday, 21.04.2021, 15:15 (Online Event)
Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. Nikolas Nüsken, Universität Potsdam:
The Stein geometry in machine learning: gradient flows, large deviations and convergence properties (online talk)
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Online Event

Abstract
Sampling or approximating high-dimensional probability distributions is a key challenge in computational statistics and machine learning. This talk will present connections to gradient flow PDEs and interacting particle systems, focusing on the recently introduced Stein variational gradient descent methodology. The construction induces a novel geometrical structure on the set of probability distributions related to a positive definite kernel function.We discuss the corresponding geodesic equations as well as large deviation functionals and leverage those to shed some light on the convergence properties of the algorithm. This is joint work with A. Duncan (Imperial College London), L. Szpruch (University of Edinburgh) and M. Renger (Weierstrass Institute Berlin).

Host
Humboldt-Universität zu Berlin
WIAS Berlin
Tuesday, 27.04.2021, 10:00 (Online Event)
Seminar Numerische Mathematik
Prof. Sashikumaar Ganesan, Indian Institute of Science Bangalore; Prof. Volker John, WIAS Berlin:
Minisymposium on machine learning
more ... Location
Online Event

Further Informations
For zoom login details please contact Volker John john@wias-berlin.de

Host
WIAS Berlin
Wednesday, 28.04.2021, 15:15 (Online Event)
Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. Katharina Hopf, WIAS Berlin:
Weak-strong uniqueness in energy-reaction-diffusion systems (online talk)
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Online Event

Abstract
We establish weak-strong uniqueness and stability properties of renormalised solutions to a class of energy-reaction-diffusion systems, which genuinely feature cross-diffusion effects. The systems considered are motivated by thermodynamically consistent models, and their formal entropy structure allows us to use as a key tool a suitably adjusted relative entropy method. Weak-strong uniqueness is obtained for general entropy-dissipating reactions without growth restrictions, and certain models with a non-integrable diffusive flux. The results also apply to a class of (isoenergetic) reaction-cross-diffusion systems.

Further Informations
Berliner Oberseminar “Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)

Host
Humboldt-Universität zu Berlin
WIAS Berlin
April 29, 2021 (Online Event)
Workshop/Konferenz: FUHRI2021: Finite volUme metHods for Real-world applIcations
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Online Event

Host
WIAS Berlin
Thursday, 20.05.2021, 14:00 (Online Event)
Seminar Numerische Mathematik
Prof. Thomas Richter, Universität Magdeburg:
Deep neural networks for accelerating fluid-dynamics simulations
more ... Location
Online Event

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

Host
WIAS Berlin
Tuesday, 08.06.2021, 15:15 (Online Event)
Oberseminar Nonlinear Dynamics
Chunming Zheng, MPI for Physics of Complex Systems, Dresden:
Transition to synchrony in the three-dimensional Noisy Kuramoto model
more ... Location
Online Event

Abstract
We investigate the transition from incoherence to global collective motion in a three-dimensional swarming model of agents with helical trajectories, subject to noise and global coupling. Without noise this model was recently proposed as a generalization of the Kuramoto model and it was found, that alignment of the velocities occurs for arbitrary small attractive coupling. Adding noise to the system resolves this singular limit.

Host
Freie Universität Berlin
WIAS Berlin
Tuesday, 15.06.2021, 15:15 (Online Event)
Oberseminar Nonlinear Dynamics
Philipp Lorenz-Spreen, MPI for Human Development, Berlin:
Modeling radicalization dynamics and polarization in temporal networks
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Online Event

Abstract
Echo chambers and opinion polarization have been recently quantified in several sociopolitical contexts, across different social media, raising concerns for the potential impact on the spread of misinformation and the openness of debates. Despite increasing efforts, the dynamics leading to the emergence of these phenomena remain unclear. Here, we propose a model that introduces the phenomenon of radicalization, as a reinforcing mechanism driving the evolution to extreme opinions from moderate initial conditions. Empirically inspired by the dynamics of social interaction, we consider agents characterized by heterogeneous activities and homophily. We analytically characterize the transition from a global consensus to an emerging radicalization that depends on parameters, which can be interpreted as the controversialness of a topic and the strength of social influence people exert on each other. Finally, we offer a definition of echo-chambers via our model and contrast the model's behavior against empirical data of polarized debates on Twitter, qualitatively reproducing the observed relation between users' engagement and opinions, as well as opinion segregation based on the interaction network. Our findings shed light on the dynamics that may lie at the core of the emergence of echo chambers and polarization in social media.

Host
Freie Universität Berlin
WIAS Berlin
June 16 – 18, 2021 (Online Event)
Workshop/Konferenz: Nonlinear Dynamics in Semiconductor Lasers
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Online Event

Host
WIAS Berlin
Tuesday, 22.06.2021, 15:15 (Online Event)
Oberseminar Nonlinear Dynamics
Bhumika Thakur, Jacobs University, Bremen:
Data driven discovery of model equations for anode-glow oscillations in a low-pressure plasma discharge
more ... Location
Online Event

Host
Freie Universität Berlin
WIAS Berlin