Plenarvorträge - DPG-Tagungen

Dynamik und Statistische Physik Montag
DY 12 Dynamical Phenomena
Zeit: Montag 11:30–13:00 Raum: H2
DY 12.1 Mo 11:30 H2
Out-of-equilibrium critical dynamics at surfaces: Cluster dissolution
and non-algebraic correlations — •Michel Pleimling 1
and Ferenc Iglói 2,3 — 1 Institut für Theoretische Physik I, Universität
Erlangen-Nürnberg, D-91058 Erlangen — 2 Research Institute for Solid
State Physics and Optics, P.O.Box 49, H-1525 Budapest — 3 Institute of
Theoretical Physics, Szeged University, H-6720 Szeged
We study nonequilibrium dynamical properties at free surfaces after
the system is quenched from the high-temperature phase into the critical
point. We show that if the spatial surface correlations decay sufficiently
rapidly the surface magnetization and/or the surface manifold correlations
have a qualitatively different universal short time behavior than the
same quantities in the bulk. At a free surface cluster dissolution may take
place instead of domain growth and as a result dynamical correlations
decay in a non-algebraic, stretched exponential form. This phenomenon
takes place in the three-dimensional Ising model and should be observable
in real ferromagnets.
DY 12.2 Mo 11:45 H2
Paradoxical non-linear response of a Brownian particle — •Ralf
Eichhorn and Peter Reimann — Universität Bielefeld, Fakultät für
Physik, D-33615 Bielefeld
We consider a single, classical Brownian particle in a periodic potential
landscape far from thermal equilibrium, that shows the following remarkable
response behavior to an external static force: Though the system is
far from equilibrium, its linear response is exactly the same as in the
equilibrium case; in particular, the particle motion follows the direction
of the external static force. However, upon increasing the static force to
the non-linear response regime, the particle suddenly starts to move in
the direction opposite to the static bias. These astonishing properties of
our system are investigated analytically and numerically.
DY 12.3 Mo 12:00 H2
Novel universality classes of a coupled driven diffusive system
— •Abhik Basu and Erwin Frey — Abteilung Theorie (SF5), Hahn-
Meitner-Institute, D-14109 Berlin
Motivated by the phenomenologies of dynamic roughening of strings
in random media and magnetohydrodynamics, we examine the universal
properties of driven diffusive system with coupled fields. We demonstrate
that cross-correlations between the fields lead to amplitude-ratios and
scaling exponents varying continuosly with the strength of these cross-
DY 14 Solitons and Stochastic Dynamics
correlations. The implications of these results for experimentally relevant
systems are discussed.
DY 12.4 Mo 12:15 H2
Critical Behavior of Coupled Oscillators. Renormalization
Group and Universality Class. — •Thomas Risler 1 , Jacques
Prost 2 , and Frank Jülicher 1 — 1 Max-Planck-Institut für Physik
komplexer Systeme, Nöthnitzer Str. 38, D-01187 Dresden. — 2 Ecole
Supérieure de Physique et de Chimie Indutrielles, 10 rue Vauquelin,
75231 Paris Cedex 05, France.
We study the behavior of coupled oscillators in the vicinity of a uniform
oscillatory instability or Hopf bifurcation in the presence of fluctuations.
A Hopf bifurcation is an example for a dynamic critical point.
The corresponding field theory is described by a complex Ginzburg Landau
equation with noise. We apply perturbative renormalization group
techniques in a 4 − ǫ dimensional space and find that the critical behavior
is related to the fixed point of the dynamic O(2) model. While the
dynamics is far from equilibrium and breaks the fluctuation dissipation
theorem, a universal relation between correlation and response exists at
the critical point.
Hauptvortrag DY 12.5 Mo 12:30 H2
Local scale invariance in ageing phenomena — •Malte Henkel
— Laboratoire de Physique des Matériaux, Université Henri Poincaré
Nancy I, B.P. 239, F - 54506 Vandœuvre-lès-Nancy, France
The temporal behaviour of ageing systems is described by the two-time
correlators C(t, s) and the response function R(t, s), where t is the observation
time and s is the waiting time. The dynamical scaling in ageing
systems leads to the scaling form R(t, s) = s −1−a f(t/s). The extension of
dynamical scaling to a local scale invariance, in close analogy to conformal
invariance, is studied. In particular, if the dynamical exponent z = 2,
we show that through a Ward identity, Galilei invariance implies local
scale invariance. This in turn leads to an explicit form of f(x), which is
tested via extensive simulation in the ageing 2D/3D Glauber-Ising model.
This provides the first evidence for Galilei invariance in an ageing
system. In addition, local scale invariance allows to reliably extract the
exponent a from integrated response functions (dynamical susceptibilities).
[1] M. Henkel, Nucl. Phys. B641, 405 (2002). [2] M. Henkel, J.
Unterberger, Nucl. Phys. B660, 407 (2003) [3] M. Henkel, M. Pleimling,
Phys. Rev. E, cond-mat/0302482 [4] M. Henkel, M. Paessens, M.
Pleimling, Europhys. Lett. 62, 664 (2003) and cond-mat/0310761.
Zeit: Montag 14:30–16:45 Raum: H2
DY 14.1 Mo 14:30 H2
Investigation of the dynamics of dissipative solitons using
stochastic data analysis — •Hendrik U. Bödeker 1 , Andreas W.
Liehr 1 , Till D. Frank 2 , Rudolf Friedrich 2 , and Hans-Georg
Purwins 1 — 1 Westfälische Wilhelms-Universität Münster, Institut für
Angewandte Physik, Corrensstr. 2/4, 48149 Münster — 2 Westfälische
Wilhelms-Universität Münster, Institut für Theoretische Physik,
Wilhelm-Klemm-Str. 9, 48149 Münster
We develop methods to analyze the dynamics and the interaction of dissipative
solitons in the form of localized current filaments under the influence
of strong fluctuations in a quasi-2-dimensional planar gas-discharge
system with high-ohmic barrier. The form of the experimentally recorded
trajectories motivates a modelling of the dynamics by stochastic differential
equations in the form of Langevin equations. Methods of stochastic
data analysis allow for a quantitative separation of the deterministic and
the stochastic part of the dynamics of isolated dissipative solitons from
the recorded data series. In this case, both intrinsically stationary and intrinsically
propagating solitons can be found. The transition takes place
via a supercritical bifurcation with a typical scaling law. This is also the
result of theoretical predictions. An extension of the Langevin equations
by generalized interaction forces enables the description of interaction
processes between several filaments. The determination of the interaction
function of mutually interacting dissipative solitons from experimentally
recorded data series reveals a distance-dependent interaction law with
varying regions of attraction and repulsion.
DY 14.2 Mo 14:45 H2
Vielteilchen-Phänomene in Reaktions-Diffusions-Systemen —
•A. W. Liehr, M. C. Röttger und H.-G. Purwins — Westfälische
Wilhelms-Universität Münster, Institut für Angewandte Physik, Corrensstr.
2/4, 48149 Münster
Dissipative Solitonen sind großamplitudige lokalisierte Strukturen mit
ausgeprägten Teilcheneigenschaften, die in diesem Beitrag anhand eines
dreikomponentigen Reaktions-Diffusions-Systems untersucht werden.
In der Nähe der Drift-Bifurkation kann die Dynamik und Wechselwirkung
der dissipativen Solitonen mittels einen Teilchenansatzes durch
Ordnungsparametergleichungen beschrieben werden, wobei als relevante
Größen die Positionen und die Propagatormodenamplituden der dissipativen
Solitonen erfasst werden [1]. Dies ermöglicht die Untersuchung
von Vielteilchensystemen, für die wir charakteristische Phänomene wie
Kompressionsfronten in kondensierten Phasen oder das Auflösen kondensierter
Phasen durch Rauscheinfluss diskutieren.
[1] Bode, M. et al.: Interaction of dissipative solitons: particle-like behaviour
of localized structures in a three-component reaction-diffusion system. Physica
D 161, 2002, S. 45ff.