Veranstaltungen

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Dienstag, 08.12.2020, 15:15 Uhr (Online Event)
Oberseminar Nonlinear Dynamics
Elisenda Feliu, University of Copenhagen, Denmark:
Understanding of bistability and Hopf bifurcations in biochemical reaction networks
mehr ... Veranstaltungsort
Online Event

Abstrakt
In the context of (bio)chemical reaction networks, the dynamics of the concentrations of the chemical species over time are often modelled by a system of parameter-dependent ordinary differential equations, which are typically polynomial or described by rational functions. The polynomial structure of the system allows the use of techniques from algebra to study properties of the system around steady states, for arbitrary parameter values. In this talk I will present the formalism of the theory of reaction networks, and how applied algebra plays a role in the study of three main questions: determination of bistability, determination of Hopf bifurcations, and parameter regions for multistationarity. I will present new results tackling these questions by using a ubiquitous and challenging network from cell signaling (the dual futile cycle) as a case example. For this network, which is relatively small, several basic questions, such as the existence of oscillations, the parameter region of multistationarity, and whether multistationarity implies bistability, remain unresolved.

Veranstalter
Freie Universität Berlin
WIAS Berlin
Mittwoch, 09.12.2020, 11:30 Uhr (Online Event)
Seminar Interacting Random Systems
Robert Patterson:
Large deviations for population growth from near zero concentration
mehr ... Veranstaltungsort
Online Event

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Seminar Interacting Random Systems

Veranstalter
WIAS Berlin
Mittwoch, 09.12.2020, 15:15 Uhr (Online Event)
Berliner Oberseminar „Nichtlineare partielle Differentialgleichungen” (Langenbach-Seminar)
Dr. Grigor Nika, WIAS Berlin:
Effective bulk-surface thermistor models for OLEDs (online talk)
mehr ... Veranstaltungsort
Online Event

Abstrakt
We consider a thin-film OLED device placed on a flat surface, part of a bulk substrate material. The device is assumed to have N>2 layers and total thickness h>0. An effective electrothermal model is derived by considering the limit of vanishing thickness as it approaches zero under physically motivated scalings. The effective equations consist of two equations for the lateral current flow in the top and bottom electrodes and an iterative set of algebraic equations for the vertical flow in the organic layers posed on the flat surface where the OLED is placed and coupled to the heat equation in the bulk substrate material.

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

Veranstalter
WIAS Berlin
Donnerstag, 10.12.2020, 15:00 Uhr (Online Event)
TES-Seminar on Energy-based Mathematical Methods and Thermodynamics
Dr. Martin Kružík, Czech Academy of Sciences:
Equilibrium for multiphase solids with Eulerian interfaces (online talk)
mehr ... Veranstaltungsort
Online Event

Abstrakt
We describe a general phase-field model for hyperelastic multiphase materials. The model features an elastic energy functional that depends on the phase-field variable and a surface energy term that depends in turn on the elastic deformation, as it measures interfaces in the deformed configuration. We prove the existence of energy minimizing equilibrium states and Gamma-convergence of diffuse-interface approximations to the sharp-interface limit. This is a joint work with D. Grandi, E. Mainini and U. Stefanelli.

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
Freitag, 11.12.2020, 10:00 Uhr (Online Event)
Forschungsseminar Mathematische Statistik
Prof. Judith Rousseau, University of Oxford, UK:
Bayesian nonparametric estimation in multivariate non linear Hawkes processes (online talk)
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Online Event

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

Veranstalter
Humboldt-Universität zu Berlin
WIAS Berlin
Dienstag, 12.01.2021, 15:00 Uhr (Online Event)
Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Dr. Pavel Dvurechensky, WIAS Berlin:
Accelerated alternating minimization methods (online talk)
mehr ... Veranstaltungsort
Online Event

Abstrakt
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.

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

Veranstalter
WIAS Berlin
Mittwoch, 13.01.2021, 11:30 Uhr (Online Event)
Seminar Interacting Random Systems
Sabine Jansen, Universität München:
Virial inversion and density functionals (online talk)
mehr ... Veranstaltungsort
Online Event

Abstrakt
We present a novel inversion theorem for functionals that map measures to measures. Our main application is in statistical mechanics of inhomogeneous systems, in which the activity $z(x) = z_0 exp( - V_ext(x))$ is mapped to a density profile $rho(x)$ and one seeks to invert the density-activity relation. In probabilistic terms, the question is how to invert the relation between the intensity measure of an underlying Poisson point process and the intensity measure of a Gibbs point process, a question also of interest in spatial statistics. We apply the inversion theorem to the derivation of density functionals. The inversion theorem works in situations where the inverse function theorem in Banach spaces fails. Based on joint work with Tobias Kuna and Dimitrios Tsagkarogiannis (arXiv:1906.02322 [math-ph]).

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Seminar Interacting Random Systems

Veranstalter
WIAS Berlin
Mittwoch, 27.01.2021, 11:30 Uhr (Online Event)
Seminar Interacting Random Systems
Lorenzo Taggi, University of Rome “La Sapienza”, Italien:
tba (online talk)
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Online Event

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Seminar Interacting Random Systems

Veranstalter
WIAS Berlin
Mittwoch, 03.02.2021, 11:30 Uhr (Online Event)
Seminar Interacting Random Systems
Elena Pulvirenti, Delft University of Technology, Niederlande:
tba (online talk)
mehr ... Veranstaltungsort
Online Event

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Seminar Interacting Random Systems

Veranstalter
WIAS Berlin