Veranstaltungen

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Dienstag, 24.11.2020, 10:15 Uhr (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
mehr ... Veranstaltungsort
Online Event

Weitere Informationen
Diesen Vortrag können Sie mit Zoom verfolgen unter: https://zoom.us/j/98493865627.

Veranstalter
WIAS Berlin
Dienstag, 24.11.2020, 15:00 Uhr (Online Event)
Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Dr. Alexander Gasnikov, WIAS Berlin:
Parallel and distributed algorithms for ML problems
mehr ... Veranstaltungsort
Online Event

Weitere Informationen
Dieser Vortrag findet bei Zoom statt: https://zoom.us/j/492088715

Veranstalter
WIAS Berlin
Dienstag, 24.11.2020, 15:15 Uhr (Online Event)
Oberseminar Nonlinear Dynamics
Dr. Giulia Ruzzene, Universitat Pompeu Fabra, Palma de Mallorca, Spain:
Control of chimera states in multilayer networks
mehr ... Veranstaltungsort
Online Event

Abstrakt
Chimera states are one of the most intriguing and studied types of partial synchronization. In small systems, which are the most relevant for experimental situations, chimera states present various instabilities. Therefore, it is natural to investigate methods to control them. We propose a control mechanism based on the idea of a pacemaker oscillator, which allows to control the position of a chimera state within a network and to prevent its collapse to the fully synchronous state. We show how this mechanism developed for ring networks of phase oscillators can be applied to multilayer networks with more complex node dynamics, such as FitzHugh-Nagumo oscillator. In particular, we show that it allows to remotely control a chimera state in one layer via a pacemaker in the other layer.

Weitere Informationen
Diesen Vortrag können Sie mit Zoom verfolgen unter: https://zoom.us/j/82815629022.

Veranstalter
Freie Universität Berlin
WIAS Berlin
Mittwoch, 25.11.2020, 10:00 Uhr (Online Event)
Forschungsseminar Mathematische Statistik
Dr. Alexander Kreiß, KU Leuven:
Unbiased Markov chain Monte Carlo methods with couplings
mehr ... Veranstaltungsort
Online Event

Abstrakt
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.

Weitere Informationen
Der Vortrag findet bei Zoom statt: https://zoom.us/j/159082384

Veranstalter
Humboldt-Universität zu Berlin
WIAS Berlin
Mittwoch, 25.11.2020, 11:30 Uhr (Online Event)
Seminar Interacting Random Systems
Willem van Zuijlen:
Total mass asymptotics of the parabolic Anderson model
mehr ... Veranstaltungsort
Online Event

Abstrakt
We 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.

Weitere Informationen
Seminar Interacting Random Systems

Veranstalter
WIAS Berlin
Mittwoch, 25.11.2020, 15:15 Uhr (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 (online talk)
mehr ... Veranstaltungsort
Online Event

Abstrakt
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.

Veranstalter
Humboldt-Universität zu Berlin
WIAS Berlin
Donnerstag, 26.11.2020, 15:00 Uhr (Online Event)
TES-Seminar on Energy-based Mathematical Methods and Thermodynamics
Prof. Dr. Miroslav Grmela, Polytechnique Montréal:
Multiscale thermodynamics (online talk)
mehr ... Veranstaltungsort
Online Event

Abstrakt
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.

Weitere Informationen
Please register on this link: https://mathplus.de/topic-development-lab/tes-winter-2020-21/tes-seminar-on-energy-based-mathematical-methods-and-thermodynamics/

Veranstalter
Technische Universität Berlin
WIAS Berlin
Donnerstag, 26.11.2020, 16:00 Uhr (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
mehr ... Veranstaltungsort
Online Event

Veranstalter
WIAS Berlin