Forschungsgruppe "Laserdynamik"

Seminar Laserdynamik (Archiv)

zu den aktuellen Veranstaltungen

Donnerstag, 12.07.2018, 10:00 Uhr (WIAS-ESH)
Prof. D. Turaev, Imperial College London, GB:
On positive metric entropy conjecture
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Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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WIAS Berlin
Montag, 11.06.2018, 16:00 Uhr (WIAS-406)
I. Bačić, University of Belgrade:
Stochastic dynamics in systems of adaptively coupled active rotators
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

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WIAS Berlin
Dienstag, 06.03.2018, 15:15 Uhr (WIAS-ESH)
Dr. O. D'Huys, Aston University, GB:
Dynamics of delay-coupled networks with time-varying connections
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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Seminar Laserdynamik

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WIAS Berlin
Montag, 26.02.2018, 14:00 Uhr (WIAS-ESH)
Dr. K. Mora, Universität Paderborn:
Says Newton to Hopf and Hogkin--Huxley: Vibrating! Impacting! Exciting!
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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WIAS Berlin
Donnerstag, 11.01.2018, 16:00 Uhr (WIAS-ESH)
Prof. A. L. Shilnikov, Neuroscience Institute, Georgia State University, USA:
Torus bifurcations in slow fast systems
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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WIAS Berlin
Dienstag, 05.12.2017, 10:00 Uhr (WIAS-ESH)
Prof. R. Čiegis, Vilnius Gediminas Technichal University, Litauen:
Numerical simulation of nonlocal delayed feedback controller for some new smart bioreactors
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstrakt
The new nonlocal delayed feedback controller is used to control the production of drugs in a simple bioreactor. This bioreactor is based on the enzymatic conversion of substrate into the required product. The dynamics of this device is described by a system of two nonstationary nonlinear diffusion-reaction equations. The control loop defines the changes of the substrate concentration delivered into the bioreactor at the external boundary of the bioreactor depending on the difference of measurements of the produced drug delivered into the body and the flux of the drug prescribed by a doctorin accordance with the therapeutic protocol. The system of PDEs is solved by using the finite difference method, the control loop parameters are defined from the analysis of stationary linearized equations. The stability of the algorithm for the inverse boundary condition is investigated. Results of computational experiments are presented and analyzed.

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WIAS Berlin
Donnerstag, 22.06.2017, 10:00 Uhr (WIAS-ESH)
S. Eydam, WIAS Berlin:
Phase oscillator mode-locking
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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Seminar Laserdynamik

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WIAS Berlin
Donnerstag, 27.04.2017, 10:00 Uhr (WIAS-ESH)
S. W. Haugland, Technische Universität München:
What can we learn about chimera states from minimal cluster dynamics?
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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Seminar Laserdynamik

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WIAS Berlin
Dienstag, 11.04.2017, 15:15 Uhr (WIAS-ESH)
Prof. D. Turaev, Imperial College London, GB:
Energy equilibration in slow-fast systems
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstrakt
We consider a slow-fast Hamiltonian system where the evolution of some degrees of freedom is slower than the evolution of others. It is well-known that the ergodicity of the fast subsystem prevents the full slow-fast system of achieving the state of statistical equilibrium.. We show that the violation of ergodicity in the fast subsystem drives the full system to equilibrium in an effective way.

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Seminar Laserdynamik

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WIAS Berlin
Dienstag, 04.04.2017, 15:15 Uhr (WIAS-ESH)
Prof. E. Knobloch, University of California, USA:
Geostrophic turbulence and the formation of large scale structure
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Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstrakt
Low Rossby number convection is studied using an asymptotically reduced system of equations valid in the limit of strong rotation. The equations describe four regimes as the Rayleigh number $Ra$ increases: a disordered cellular regime near threshold, a regime of weakly interacting convective Taylor columns at larger $Ra$, followed for yet larger $Ra$ by a breakdown of the convective Taylor columns into a disordered plume regime characterized by reduced heat transport efficiency, and finally by geostrophic turbulence. The Nusselt number--Rayleigh number scaling in the ültimate" regime of geostrophic turbulence is predicted and confirmed using direct numerical simulations of the reduced equations. These simulations reveal that geostrophic turbulence is unstable to the formation of large scale barotropic vortices, via a process known as spectral condensation. The details of this process are quantified and its implications explored.

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Seminar Laserdynamik

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WIAS Berlin
Dienstag, 20.09.2016, 15:15 Uhr (WIAS-ESH)
Dr. S. Olmi, WIAS Berlin:
Dynamics of fully coupled rotators with unimodal and bimodal frequency distribution
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstrakt
We analyze the synchronization transition of a globally coupled net- work of N phase oscillators with inertia (rotators) whose natural frequencies are unimodally or bimodally distributed. In the unimodal case [1], the system exhibits a discontinuous hysteretic transition from an incoherent to a partially synchronized (PS) state. For sufficiently large inertia, the system reveals the coexistence of a PS state and of a standing wave (SW) solution. In the bimodal case [2], the hysteretic synchronization transition involves several states. Namely, the system becomes coherent passing through traveling waves (TWs), SWs and finally arriving to a PS regime. The transition to the PS state from the SW occurs always at the same coupling, independently of the system size, while its value increases linearly with the inertia. On the other hand the critical coupling required to observe TWs and SWs increases with N suggesting that in the thermodynamic limit the transition from incoherence to PS will occur without any intermediate states. Finally a linear stability analysis reveals that the system is hysteretic not only at the level of macroscopic indicators, but also microscopically as verified by measuring the maximal Lyapunov exponent. [1] S. Olmi, A. Navas, S. Boccaletti and A. Torcini, ?Hysteretic transi- tions in the Kuramoto model with inertia?, Physical Review E, 90(4), p.042905. [2] S. Olmi and A. Torcini, ?Dynamics of fully coupled rotators with unimodal and bimodal frequency distribution?, Control of Self-Organizing Nonlinear Systems. Springer International Publishing, 2016. 25-45.

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WIAS Berlin
Donnerstag, 28.07.2016, 10:00 Uhr (WIAS-ESH)
Prof. D. Turaev, Imperial College London, GB:
Adiabatic acceleration in quantum mechanical systems
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstrakt
We discuss how the adiabatic evolution of a quantum-mechanical system due to the slow and periodic change of system parameters can lead to an exponential growth of the energy. This contradicts, at first glance, to the quantum adiabatic theorem, however we show that periodic creation and destruction of an additional quantum integral leads to the adiabatic level crossing necessary for the acceleration. As an example, we consider the Schroedinger equation in a periodically divided and reconnected domain.

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Seminar Laserdynamik

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WIAS Berlin
Donnerstag, 07.07.2016, 10:00 Uhr (WIAS-ESH)
Dr. S. Bialonski, Max-Planck-Institut für Physik komplexer Systeme:
Predicting and preventing extreme events in a spatially extended excitable system
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstrakt
Extreme events occur in many spatially extended systems and can threaten human life. Their reliable prediction and prevention is thus highly desirable. We study the prediction and prevention of extreme events in a spatially extended system, a network of FitzHugh-Nagumo units, in which events occur in a spatially and temporally irregular way. Despite being challenged by the rareness of events and without knowing the governing equations of motion, we can predict - with a data-driven method - the beginning, propagation, and termination of extreme events in this system remarkably well. We suppress extreme events via tiny and spatiotemporally localized perturbations which are guided by our predictions. We discuss how symmetries in the system could be exploited for better forecast performance.

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WIAS Berlin
Mittwoch, 11.05.2016, 14:00 Uhr (WIAS-406)
Dr. I. Franovic, Institute of Physics Belgrade, Serbien und Montenegro:
Mean-field approach for analysis of collective dynamics and activation processes in coupled noisy excitable systems
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Abstrakt
The first part of the talk will be concerned with the main approximations behind the mean-field approach and its application to analysis of collective dynamics in systems of delay-coupled excitable units. After introducing the formulation of the two main approximations behind the model, called the Gaussian approximation and the Quasi-independence approximation, it will be shown that the dynamics of the mean-field model can indicate in a self-consistent fashion the parameter domains where the Quasi-independence approximation fails. Using the examples of a network of globally coupled units, and the paradigmatic setup of two interacting assemblies, I shall demonstrate that the mean-field model can be used to qualitatively analyze the stability of the system, as well as the scenarios for the onset and the suppression of the collective mode. The second part of the talk will be dedicated to characterization of the activation process in coupled excitable systems influenced by two independent sources of noise, which may be interpreted as external and intrinsic noise. The mean-field model will be applied to explicitly demonstrate that an assembly of class II excitable units can itself exhibit macroscopic excitable behavior. The statistical features of the assembly activation process, such as the mean time-to-first pulse and the associated coefficient of variation, will be compared to the ones of a single and two coupled excitable units. Using the mean-field model, we will show that the universal behavior in all three cases generically derives from the fact that the considered systems undergo a stochastic bifurcation from the stochastically stable fixed point to continuous oscillations.

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Seminar Laserdynamik

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WIAS Berlin
Donnerstag, 23.07.2015, 10:00 Uhr (WIAS-ESH)
Dr. H. Chiba, Kyushu University, Japan:
Renormalization group methods for ODEs/PDEs
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Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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WIAS Berlin
Dienstag, 10.03.2015, 15:00 Uhr (WIAS-ESH)
Dr. S. Gurevich, Wilhelms-Universität Münster:
Control and selection of spatio-temporal patterns in dynamic self-assembly systems
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstrakt
Self-organization or dynamic self-assembly is a mechanism responsible for the formation of complex structures through multiple interactions among the microscopic components of the system. In the first part of the talk the formation of regular stripe patterns during the transfer of surfactant monolayers from water surfaces onto moving solid substrates is discussed by means of a generalized Cahn-Hilliard model. A combination of numerical simulations and continuation methods is employed to investigate stationary and time-periodic solutions of the model . The second part of the talk deals with the influence of a periodic spatial forcing on the pattern formation in Langmuir-Blodgett transfer experiments. We show that the occurring locking effects enable a control mechanism for the pattern formation process. In the one-dimensional case the parameter range in which patterns are created can be increased and the properties of occurring structures can be adjusted in a broader range. Alternatively, in two dimensions, one-dimensional stripe patterns can be destabilized, giving rise to a multitude of complex two-dimensional structures, including oblique and lattice patterns. In addition, a different control mechanism by means of a modulated transfer velocity is discussed. Our theoretical results predict that this method can also be used as an effective tool to control the pattern formation process.

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Seminar Laserdynamik

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WIAS Berlin
Dienstag, 24.06.2014, 13:00 Uhr (WIAS-ESH)
Prof. V. Kocharovskii, Russian Academy of Sciences, Institute of Applied Physics:
Dynamical and spectral features of superradiant lasing
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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Seminar Laserdynamik

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WIAS Berlin
Dienstag, 20.05.2014, 10:00 Uhr (WIAS-HVP-3.13)
Dr. D. Kulikov, Yaroslavl State University:
Local bifurcations of the generalized Kuramoto-Sivashinsky equation (Talk in Russian language)
mehr ... Veranstaltungsort
Weierstraß-Institut, Hausvogteiplatz 11A, 10117 Berlin, 3. Etage, Raum: 3.13

Abstrakt
Kuramoto-Sivashinsky equation with periodic boundary value condition is considered. The stability of the homogeneous status of equilibrium is investigated as well as the local bifurcation of the spatially non-homogeneous t periodic solutions. It is shown that these solutions form two-dimensional invariant manifolds. These manifolds can be stable or unstable but all solutions of these manifolds are always unstable. The bifurcation problem is reduced to investigation of a system of ordinary differential equations (normal form). This normal form was constructed by a modified Krylov-Bogolubov algorithm. These normal forms can be used to explain a ripple topography induced by ion bombardment

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Oberseminar Nonlinear Dynamics

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WIAS Berlin
Freie Universität Berlin
Donnerstag, 14.11.2013, 10:00 Uhr (WIAS-406)
Dr. I. Kashchenko, Yaroslavl Demidov State University, Russia:
Dynamics of Lang-Kobayashi equations with large control coefficient
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

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Seminar Laserdynamik

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WIAS Berlin
Donnerstag, 17.10.2013, 10:00 Uhr (WIAS-ESH)
O. Lass, University of Michigan, USA:
Nichtlinearität von VCSEL-Lasern
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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WIAS Berlin
Dienstag, 13.08.2013, 10:00 Uhr (WIAS-ESH)
Dr. E. Montbrio, Universitat Pompeu Fabra Barcelona, Spain:
Low-dimensional dynamics of populations of pulse-coupled oscillators
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstrakt
In 1967, Winfree proposed the first mathematical model for the collective synchronization observed in large populations of biological oscillators. The Winfree model consists of a large population of all-to-all pulse-coupled oscillators, and has has biologically realistic parameters, such as pulses and phase response curves. In this talk I will demonstrate that the Winfree model, evolves into the so-called Ott-Antonsen invariant manifold. This permits to exactly describe this high-dimensional system in terms of a few macroscopic variables, and to exhaustively investigate its dynamics in terms of biologically meaningful parameters. In this framework phenomena and problems that so far were only mathematically addressable using the celebrated Kuramoto model become tractable. We illustrate this by uncovering the existence of periodic, quasiperiodic and chaotic chimera states in simple networks of pulse-coupled oscillators.

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Seminar Laserdynamik

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WIAS Berlin
Donnerstag, 16.05.2013, 14:15 Uhr (WIAS-HVP-3.13)
Prof. A. Scheel, University of Minnesota, USA:
Pattern selection in the wake of fronts
mehr ... Veranstaltungsort
Weierstraß-Institut, Hausvogteiplatz 11A, 10117 Berlin, 3. Etage, Raum: 3.13

Abstrakt
Motivated by the formation of complex patterns in the wake of growth processes in bacterial colonies, we'll study more generally patterns formed in the wake of moving fronts. We discuss a number of mathematical problems that arise when one tries to predict which wavenumbers and what type of pattern is created by the growth process. We therefore describe in some detail how to derive linear predictions and analyze nonlinear mechanisms that lead to failure of these predictions. This is joint work with Matt Holzer and Ryan Goh.

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Seminar Laserdynamics

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WIAS Berlin
Donnerstag, 02.05.2013, 15:00 Uhr (WIAS-ESH)
S. Telker, Freie Universität Berlin:
Carmichaels Vermutung über die Phi-Funktion und Hyperkörper in der algebraischen Geometrie
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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Seminar Laserdynamik

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WIAS Berlin
Donnerstag, 02.05.2013, 14:00 Uhr (WIAS-ESH)
M. Babilon, Universität Paderborn:
Phasenübergangsstabilität von substratgestützten Indiumnanodrähten
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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Seminar Laserdynamik

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WIAS Berlin
Mittwoch, 16.01.2013, 13:00 Uhr (WIAS-406)
Prof. S. A. Kashchenko, Yaroslavl Demidov State University, Russia:
Relaxation oscillations in autogenerators with different delay feedbacks
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

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Seminar Laserdynamik

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WIAS Berlin
Dienstag, 08.01.2013, 15:00 Uhr (WIAS-ESH)
Prof. A. Shilnikov, Georgia State University, USA:
Symbolic toolkit for exploration of deterministic chaos
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstrakt
Computational technique based on the symbolic description utilizing kneading invariants is proposed for explorations of parametric chaos in a three exemplary systems with the Lorenz attractor: the canonical Lorenz equations from hydrodynamics, a normal model from mathematics, and a laser model from nonlinear optics. The technique allows for uncovering the stunning complexity and universality of the patterns discovered in the bi-parametric scans of the given models and detects their organizing centers ? codimension-two T-points and separating saddles. Joint with Tingli Xing, Jeremy Wojcik, Roberto Barrio

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Seminar Laserdynamik

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WIAS Berlin
Dienstag, 08.01.2013, 10:00 Uhr (WIAS-ESH)
Dr. S. Gurevich, Wilhelms-Universität Münster:
Instabilities of localized structures in reaction-diffusion systems with delayed feedback
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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WIAS Berlin
Dienstag, 18.12.2012, 10:30 Uhr (WIAS-ESH)
F. Schilder, Technical University of Denmark:
Coupling computational bifurcation analysis to lab experiments
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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Seminar Laserdynamics

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WIAS Berlin
Dienstag, 11.09.2012, 10:00 Uhr (WIAS-ESH)
M. Liertzer, Technische Universität Wien:
Introduction to the steady-state ab-initio laser theory and its applications
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstrakt
The key equations of semi-classical laser theory are the Maxwell-Bloch equations. This time-dependent and nonlinear set of partial differential equations describes a wealth of phenomena in laser physics but remains rather difficult to solve. An alternative for finding the steady-state solutions of the Maxwell-Bloch system that bypasses the expensive time-integration has recently been proposed in terms of the Steady-state Ab-initio Laser Theory (SALT) [1]. This new framework treats the openness of the cavity in an exact manner and includes all non-linear modal interactions to infinite order. The theory has meanwhile been applied to a multitude of different lasers. In my talk I will focus on results obtained for random lasers [2] and for coupled micro-cavity lasers [3], respectively. I will demonstrate how in these cases the SALT is not only ideally suited to find the lasing solutions efficiently but also to interpret these solutions conveniently. [1] Türeci, Stone, Ge, Rotter, Tandy, Nonlinearity 22, C1 (2009) [2] Türeci, Ge, Rotter, Stone, Science 320, 643 (2008) [3] Liertzer, Ge, Cerjan, Stone, Türeci, Rotter, PRL 108, 173901 (2012)

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Seminar Laserdynamik

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WIAS Berlin
Donnerstag, 16.08.2012, 10:00 Uhr (WIAS-ESH)
Dr. I. Kashchenko, Yaroslavl Demidov State University, Russia:
Dynamics of equations with large spatially distributed control
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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WIAS Berlin
Dienstag, 14.08.2012, 15:00 Uhr (WIAS-ESH)
Dr. I. Kashchenko, Yaroslavl Demidov State University, Russia:
Local analysis of a model for mode-locking in lasers
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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WIAS Berlin
Donnerstag, 22.03.2012, 10:00 Uhr (WIAS-406)
Dr. O. Omel'chenko, WIAS Berlin:
Coherence-incoherence patterns in systems of non-locally coupled phase oscillators
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

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WIAS Berlin
Dienstag, 13.12.2011, 10:00 Uhr (WIAS-ESH)
Dr. S. Zelik, University of Surrey, UK:
Infinite-dimensionality in the "finite-dimensional" dissipative dynamics
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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WIAS Berlin
Donnerstag, 08.12.2011, 10:00 Uhr (WIAS-ESH)
Prof. R. Ciegis, Gediminas Technical University, Vilnius:
Numerical approximation of one model of the bacterial self-organization: analysis of the dynamics
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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WIAS Berlin
Donnerstag, 01.12.2011, 10:00 Uhr (WIAS-ESH)
Dr. D. Glyzin, Yaroslavl State University:
Relaxation oscillations in a chain of coupled delay differential equations
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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WIAS Berlin
Dienstag, 09.08.2011, 15:00 Uhr (WIAS-ESH)
Th. Kolokolnikov, Dalhousie University:
Particle interaction models of biological aggregation
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstrakt
Animal groups often form striking aggregation patterns. Examples include from schools of fish to locust swarms, to patterns in bacterial cultures. In this talk, we discuss a very simple model of swarming based on pairwise particle interactions with short-range attraction and long-range repulsion, which can lead to very complex and intriguing patterns in two or three dimensions. Depending on the relative strengths of attraction and repulsion, a multitude of various patterns are observed, from nearly-constant density swarms to annular solutions, to complex N-fold symmetry patterns. We show that annular-type patterns may form if short-range repulsion is sufficiently weak. A Turing-type analysis of such annular states further reveals a wealth of possible instabilities which often lead to complicated and beautiful patterns. We also classify two-ring, annular and triangular patterns which arise when the ring becomes unstable. In three dimensions, we classify the stability of a sphere using spherical harmonics. Finally, we consider the inverse problem: given a target pattern, how to custom-design the interaction force to obtain said pattern as a steady state.

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WIAS Berlin
Dienstag, 26.07.2011, 15:00 Uhr (WIAS-ESH)
Prof. D. Turaev, Imperial College London:
Diffeomorphisms not conjugate to those of higher smoothness
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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WIAS Berlin
Dienstag, 19.07.2011, 10:00 Uhr (WIAS-406)
R. Arkhipov, Saint-Petersburg:
Theoretical investigations of some problems interaction of resonance laser radiation and matter - analytical and numerical simulations
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

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WIAS Berlin
Montag, 18.07.2011, 13:00 Uhr (WIAS-ESH)
S. Morawiec, Lodz:
Polarization effects in nitride light emitting diodes
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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WIAS Berlin
Donnerstag, 14.07.2011, 10:00 Uhr (WIAS-ESH)
K. Filonenko, St-Petersburg:
One-- and two--frequency spectral purities of optical parametric oscillator
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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WIAS Berlin
Dienstag, 05.07.2011, 10:00 Uhr (WIAS-ESH)
D. A. Puzyrev, St-Petersburg:
Advanced numerical and computational methods in modeling of quantum few-body phenomena
mehr ... Veranstaltungsort
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

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WIAS Berlin