Events & Teaching

Upcoming Events

go to archive

Thursday, 23.10.2014, 10.00 Uhr (WIAS-406)
Seminar Thermodynamische Modellierung und Analyse von Phasenübergängen
J.-F. Pietschmann, Technische Universität Darmstadt, Department of Mathematics:
Motion and size exclusion - Derivation and properties of non-linear cross-diffusion models
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Abstract
Modelling the transport of particles with size exclusion is of high relevance in many current applications, e.g., in molecular and cell biology. In the case of a single type of particle, various models have been proposed at the continuum level or derived from microscopic models typically leading to nonlinear drift-diffusion equations for the particle density. Less attention has been paid to the case of several different particles, which is, however, very relevant in many practical problems such as the transport of ions through narrow membrane channels. In this talk we will discuss the derivation of such a model based on a formal limit of a jump process and discuss several properties such as existence of solutions and long-time behaviour.

Host
WIAS Berlin
Thursday, 23.10.2014, 16.00 Uhr (WIAS-ESH)
Forschungsseminar Mathematische Modelle der Photonik
Prof. E. Tobisch, Universität Linz, Institut für Analysis, Austria:
Energy cascades in physical systems with small and moderate nonlinearity
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
We begin with a short overview of main historical concepts of energy cascading: Richardson (1922), Kolmogorov (1941) and Zakharov (1967). First two models are developed for a strongly nonlinear system (strong turbulence of vortexes) and the latter - for a very weakly nonlinear system (weak turbulence of waves). Both models predict a power law shape of the energy spectrum. A new model will be presented which is developed to fill the gap between strong and very weak nonlinearity: The dynamic cascade. Building on the sidebands from a modulational instability, the theory predicts a cascade of energy into additional sidebands, and the detailed cascade is described by the "chain equation". The shape of energy spectrum in common case is exponential but can be reduced to a power law, for some choice of initial excitation. The theory is applied to focusing NLS (water waves) and to mKdV; it is also supported by observations in the experiments with water waves.

Host
Humboldt-Universität zu Berlin
WIAS Berlin
Tuesday, 28.10.2014, 10.15 Uhr (WIAS-406)
Seminar Nichtlineare Optimierung und Inverse Probleme
Dr. N. Botkin, Technische Universität München:
Modeling of polarized radiation transfer: Application to computed tomography
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Host
WIAS Berlin
Tuesday, 28.10.2014, 15.00 Uhr (WIAS-406)
Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
M. Maurelli, WIAS Berlin:
Mean field equations and a model on lithium-ion batteries
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Abstract
In this talk I will introduce interacting particles systems and their mean field limit and I will then discuss a simple model on lithium-ion batteries, where a mean field interpretation arises naturally. In the first part I will show how a nonlinear partial differential equation (of a certain form) can be interpreted as a mean field limit of an interacting particle system. Advantages of this approach can be both in terms of the physical description of a phenomenon and in terms of simulations. In the second part I will put this into a particular model arising in the study of lithium-ion batteries. I will then discuss intuition and main challenges of this model.

Host
WIAS Berlin
Wednesday, 29.10.2014, 10.00 Uhr (WIAS-ESH)
Forschungsseminar Mathematische Statistik
Dr. D. Li, University of York, UK:
Panel data models with interactive fixed effects and multiple structural breaks
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
In this paper we consider estimation and inference of common structural breaks in panel data models with interactive fixed effects which are unobservable. We introduce a penalized principal component estimation procedure via adaptive group fused LASSO to detect the multiple structural breaks. Under mild conditions, we show that with probability tending to one our method can correctly determine the unknown number of breaks and consistently estimate the common break dates. Furthermore, to improve the convergence rates, we estimate the regression coefficients through the post-LASSO method and establish the asymptotic distribution theory of the resulting estimators. We also propose a data-driven method to determine the tuning parameter involved in the penalized principal component estimation procedure. The Monte Carlo simulation results demonstrate that the proposed method works well in finite sample case.

Host
WIAS Berlin
Humboldt-Universität zu Berlin
Universität Potsdam
Monday, 03.11.2014, 14.00 Uhr (WIAS-ESH)
INSTITUTSKOLLOQUIUM
N. Triantafyllidis, Ecole Polytechnique, Laboratoire de Mecanique des Solides & Departement de Mecanique:
Electromagnetic forming: a new coupled variational formulation and solution algorithms
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
WIAS Berlin
Tuesday, 04.11.2014, 15.00 Uhr (WIAS-406)
Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Dr. R. Hildebrand, WIAS Berlin:
A problem in geometric probability with applications to finance
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Host
WIAS Berlin
Wednesday, 05.11.2014, 10.00 Uhr (WIAS-HVP-3.13)
Halbleiterseminar
Prof. Dr. I. Popov, State University of Information Technologies, Mechanics and Optics, St.-Petersburg/Russia:
Spectral problem for chain type nanostructures
more ... Location
Weierstraß-Institut, Hausvogteiplatz 11A, 10117 Berlin, 3. Etage, Raum: 3.13

Abstract
The model of quantum graph for nanostructures of chain type is considered. The continuous spectrum is described for chain of rings (particularly in a magnetic field)? for nanoribbon and for decorated chain graph. We discuss the problem of the point spectrum for the corresponding locally perturbed systems.

Further Informations
WIAS-Halbleiterseminar

Host
WIAS Berlin
Wednesday, 05.11.2014, 10.00 Uhr (WIAS-ESH)
Forschungsseminar Mathematische Statistik
Dr. K. Efang, University of Kent at Canterbury, UK:
An adaptive composite quantile approach to dimension reduction for censored data
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
Sufficient dimension reduction [Li (1991)] has long been a prominent issue in multivariate nonparametric regression analysis. In this paper, we study dimension reduction(DR) for censored data, where semi-parametric structures are assumed for both the dependent variable and the censoring variable. Incorporating the idea of "redistribution-of-mass'' (Efron, 1967; Portnoy, 2003) for dealing with random censoring, we propose an adaptive composite quantile approach. As a general dimension reduction method, it requires minimal assumptions and is capable of recovering the entire DR spaces for both the dependent variable and the censoring variable and based on numerical evidence is more efficient than some existing methods compared with parametric methods such as the Cox proportional hazard (PH) model and the accelerated failure time (AFT) model, our new approach runs less risk of model misspecification, but retains comparable efficiency due to its use of a structure-adaptive kernel function. Asymptotic results are proved and numerical examples are provided. An application of the new method in the study of the popular primary biliary cirrhosis data, leads to a conclusion more consistent with empirical medical evidence than existing statistical analysis did.

Host
WIAS Berlin
Humboldt-Universität zu Berlin
Universität Potsdam
Wednesday, 05.11.2014, 15.15 Uhr (WIAS-ESH)
BERLINER OBERSEMINAR Nichtlineare partielle Differentialgleichungen (Langenbach-Seminar)
Dr. J. Fischer, MPI MIS, Leipzig:
Global existence of renormalized solutions to entropy-dissipating reaction-diffusion systems
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
Consider a single reversible chemical reaction with mass-action kinetics. The corresponding reaction-diffusion equation then formally satisfies an entropy inequality. Nevertheless, in general global existence of solutions for the reaction-diffusion equation has remained an open problem due to the possibly steep growth of the reaction terms. We propose a notion of renormalized solutions for such equations and succeed in proving global existence of solutions for general initial data and coefficients. Our notion of renormalized solutions reduces to the usual notion of weak solutions if the reaction terms are integrable.

Further Informations
Berliner Oberseminar ``Nichtlineare Partielle Differentialgleichungen'' (Langenbach Seminar)

Host
WIAS Berlin
Humboldt-Universität zu Berlin
Monday, 10.11.2014, 14.00 Uhr (WIAS-ESH)
INSTITUTSKOLLOQUIUM
Th. Schröder/G. Capellini, Leibniz-Institut für innovative Mikroelektronik (IHP):
Modern Materials Research for "More than Moore" Silicon Microelectronics (T. Schröder) / A Si CMOS compatible Ge laser source on Silicon (G. Capellini)
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
WIAS Berlin
Wednesday, 12.11.2014, 15.15 Uhr (WIAS-ESH)
BERLINER OBERSEMINAR Nichtlineare partielle Differentialgleichungen (Langenbach-Seminar)
Prof. Dr. A. Mielke, WIAS Berlin:
On the microscopic origin of generalized gradient structures
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Further Informations
Berliner Oberseminar ``Nichtlineare Partielle Differentialgleichungen'' (Langenbach Seminar)

Host
WIAS Berlin
Humboldt-Universität zu Berlin
November 20 – 21, 2014 (WIAS-ESH)
Workshop/Konferenz: Workshop on Recent Advances in High-Frequency Statistics
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
WIAS Berlin
SFB 649: Ökonomisches Risiko
Xiamen University
DFG Research Unit 1735
November 24 – 26, 2014 (WIAS-ESH)
Workshop/Konferenz: Collective dynamics in coupled oscillator systems
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
WIAS Berlin
SFB 910 ``Control of self-organizing nonlinear systems: Theoretical methods and concepts of application''
Thursday, 27.11.2014, 10.00 Uhr (WIAS-ESH)
Seminar Laserdynamik
J. Javaloyes, University of Balearic Island, Department of Physics:
t.b.a.
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Further Informations
Seminar Laserdynamics

Host
WIAS Berlin
Thursday, 27.11.2014, 16.00 Uhr (WIAS-ESH)
Forschungsseminar Mathematische Modelle der Photonik
Prof. Dr. R. Martin, Leibniz-Institut für Astrophysik Potsdam (AIP):
Highly stable mode-locked diode laser system for precision comparisons in microgravity
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
The contemporary term ?Astrophotonics? has already been in use since about a decade, but it is still a relatively new discipline to most physicists and astronomers. Adopting the definition of ?manipulation of light by materials? for photonics, quite analogous to the term ?electronics?, we understand astrophotonics as a subdiscipline of physics research and engineering, that utilizes optical effects of advanced materials for novel applications in observational astronomy and instrumentation. Historically, the field of photonics has emerged from optoelectronics with revolutionary innovations for the telecommunication sector. In a broader sense, there exist today a growing number of applications in other fields, such as industrial process technologies, sensor and illumination technologies, life science (biophotonics), etc. Astrophotonics seems to be a logical evolution in the area of astronomy, with promising applications for a future generation of instrumentation. I shall present a review of the evolution of astrophotonics with some remarks about the impact on the advance of astrophysics to date, and then focus on selected examples of current research like OH suppression fibre bragg gratings, miniaturized spectrographs ?on-the-chip?, and laser frequency combs for wavelength calibration in spectroscopy. I shall conclude with a somewhat speculative vision of future directions.

Host
Humboldt-Universität zu Berlin
WIAS Berlin
March 11 – 13, 2015 (WIAS-ESH)
Workshop/Konferenz: Applied Mathematics and Simulation for Semiconductors
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
WIAS Berlin