Plenarvorträge - DPG-Tagungen

Dynamik und Statistische Physik Donnerstag
DY 46.34 Do 16:00 Poster D
Transport von Sauerstoff in dünne Flüssigkeitsfilme —
•Marcus J. B. Hauser und Stefan C. Müller — Otto-von-
Guericke-Universität, Institut für Experimentelle Physik, Abteilung
Biophysik, Universitätsplatz 2, 39106 Magdeburg
Der Transport von Sauerstoff aus der Gasphase in 1,5 mm dicken
Filme aus Schwefelsäure bzw. Wasser wird untersucht. Dazu wird der
zeitliche Verlauf der Sauerstoffkonzentration in den Flüssigkeitsfilmen
höhenabhängig (im Abstand von 0,1 mm) gemessen. Daraus werden die
Konzentrationsprofile berechnet. Während der Transport von Sauerstoff
in einen Wasser-Film über Diffusion erfolgt, ist die Situation im Falle der
Schwefelsäure-Filme komplexer. Der Sauerstofftransport in Schwefelsäure
zeigt oberfl#achenspannungsgetriebene (Marangoni) Konvektion, die in
den ersten 0,5 mm von der Grenzfläche (gasförmig / flüssig) auftritt. Der
Transport in tieferen Schichten des Schwefelsäure-Films (0,5 mm leq h ≤
1,5 mm) lässt sich gut durch Diffusion beschreiben. Über die Ursachen
für dieses Verhalten wird berichtet.
DY 46.35 Do 16:00 Poster D
Dynamics and Control of a 2-D Passive Dynamic Walker —
•Joachim Haß 1 , Norbert Mayer 2 , and Michael Herrmann 1 —
1 Max-Planck-Institut für Strömungsforschung, Göttingen, Germany —
2 GMD - Japan Research Laboratory Collaboration Center, Kitakyushu,
Japan
From the biomechanical point of view, bipedal locomotion can be considered
as the dynamics of a set of rigid bodies, connected by joints,
springs, and specifically placed actuators. A passive walker [1] is an even
more simplified model which is capable of stable walking on a downhill
slope with no actuation or control whatsoever.
Combining experimental, numerical and theoretical methods, stability
and speed of a modified walker closer to human gait dynamics were examined.
Both of them crucially depended on precise tuning of the walkers
internal parameters, which were optimized using a genetic algorithm in
the numerical simulations.
The basins of attraction in parameter space could be significantly
broadened by incorporating actuators and nonlinear control algorithms
into the model. Aside from increasing the walker’s stability, this also enabled
it to walk very efficiently on arbitrarily shallow slopes at a range of
different speeds. Furthermore, we considered more biologically motivated
forms of control, like synchronizing the body movements with a central
pattern generator.
[1] McGeer T. (1993) Int. J. Robotics Res. 9:2, 62-82.
DY 46.36 Do 16:00 Poster D
Calculation of periodic orbits and spectral correlations in pseudointegrable
systems — •Jesper Mellenthin and Stefanie Russ
— Institut für Theoretische Physik III, Universität Giessen, D-35392
Giessen, Germany
We investigate pseudointegrable quantum billiards of different genus
numbers g. We calculate numerically the periodic orbits and compare
them to the Fourier transform of the density of states. We find a very
good agreement between both. From the periodic orbits we calculate
the spectral correlation of the corresponding quantum system, i.e. the
spectral rigidity ∆3. We study how ∆3 depends on the energy and investigate
the difference between the diagonal approximation and the full
semiclassical expression over diagonal and non-diagonal terms. We find
that ∆3 for pseudointegrable systems is intermediate between integrable
and chaotic systems and that the contribution of very long orbits can be
neglected.
DY 46.37 Do 16:00 Poster D
Resonance-assisted tunneling in the kicked rotor —
•Christopher Eltschka and Peter Schlagheck — Institut
für theoretische Physik, Universität Regensburg
We investigate tunneling in the quantum kicked rotor, which manifests
itself in small eigenphase splittings between symmetric and antisymmetric
combinations of “left-moving” and “right-moving” quasi-modes. Our
special interest lies in the role of nonlinear resonances, which appear as
island chains in the classical phase space and which induce couplings that
substantially enhance the tunneling process [1]. Semiclassical reproductions
of the splittings, which are based on the resonance-assisted coupling
mechanism, are compared with the exact quantum splittings, which are
calculated by using multiple precision arithmetics.
[1] O. Brodier, P. Schlagheck, and D. Ullmo, Phys. Rev. Lett. 87,
064101 (2001), Ann. Phys. 300, 88 (2002).
DY 46.38 Do 16:00 Poster D
Level dynamics in pseudointegrable billiards: an experimental
study — •Yuriy Hlushchuk 1 , Stefanie Russ 1 , Ulrich Kuhl 2 , and
Hans-Jürgen Stöckmann 2 — 1 Institut für Theoretische Physik III,
Universität Giessen, D-35392 Giessen, Germany — 2 Fachbereich Physik,
Philipps-Universität Marburg, Renthof 5, D-35032 Marburg, Germany
The level dynamics of pseudointegrable systems with different genus
numbers g was studied experimentaly using microwave cavities. The
eigenvalue velocity distribution is found to be Gaussian, like in GOE
systems, and shows no dependances on the genus number g of the system.
Although the distributions of large curvatures in our pseudointegrable
systems correspond to the distribution in chaotic systems, the
small curvatures show the intermediate behavior between chaotic and integrable
systems. With growing genus number g the distribution of small
curvatures goes from that one for integrable systems in direction of the
distribution for pure GOE systems.
According to the conjecture of Yukawa the parametric motion of the
eigenvalues in a system can be treated as a motion of particles in a 1D
gas. The level dynamics of an integrable system corresponds to a 1D
gas without interaction between particles, while a chaotic level dynamics
corresponds to a 1D gas with a long-range interaction. The model of a
short-rage interaction between eigenvalue particles for the description of
the level dynamics in pseudointegrable systems is discussed.
DY 46.39 Do 16:00 Poster D
Soft wall quantum dots modelled with microwave cavities —
•Y.-H. Kim 1 , U. Kuhl 1 , H.-J. Stöckmann 1 , and J. P. Bird 2 —
1 Fachbereich Physik, Philipps-Universität Marburg, Renthof 5, D-35032
Marburg, Germany — 2 Department of Electrical Engineering and Center
for Solid State Electronics Research, Arizona State University, Tempe,
AZ 85287-5706, USA
By an adiabatic change of the height of flat microwave cavities quantum
billiards with soft wall potentials can be modelled [1]. Eigenresonances
and eigenfunctions are investigated for an harmonic oscillator like billiard,
serving as a test example, and a billiard corresponding to a quantum dot
with soft walls [2]. For the harmonic oscillator a good agreement between
measurements and theory is found. In case of the quantum dot billiard
the behaviour of the resonances corresponding to bouncing ball states is
investigated in detail.
[1] H.M. Lauber, Ph.D. thesis, Universität Heidelberg, 1994.
[2] de Moura et al, Phys. Rev. Lett. 88, 236804 (2002).
DY 46.40 Do 16:00 Poster D
Distribution of reflection coefficients for microwave cavities
in dependence of coupling and absorption strength — •U.
Kuhl 1 , H.-J. Stöckmann 1 , R. A. Méndez-Sánchez 2 , and C. H.
Lewenkopf 3 — 1 Fachbereich Physik, Philipps-Universität Marburg,
Renthof 5, D-35032 Marburg, Germany — 2 Centro de Ciencias Físicas
UNAM, A.P 48-3, 62210, Cuernavaca, Morelos, México — 3 Instituto de
Física, UERJ, R. São Francisco Xavier 524, 20550-900 Rio de Janeiro,
Brazil
The reflection spectra of rectangular microwave cavities, with a half
circular inset attached to one of the walls, have been measured in dependence
of the position of the inset. To cover the range from weak up
to strong absorption, for part of the measurements one wall was coated
with a layer of absorbing material. The distribution of reflection coefficients
was investigated in dependence of the antenna coupling strength
and the absorption within the cavities. The results are in good agreement
with numerical calculations, as well as with the theoretical predictions
for the limiting case of strong absorption [1]. In spite of the fact that
the system is time-reversal invariant, it is found that Gaussian unitary
ensemble calculations can be used to describe the results, if only the
coupling parameter is rescaled by a factor of two [2].
[1] E. Kogan, P.A. Mello, and H. Liqun, Phys. Rev. E 61, R17 (2000).
[2] D.V. Savin and H.-J. Sommers, Phys. Rev. E 68, 036211 (2003).
DY 46.41 Do 16:00 Poster D
TRANSPORT AND DYNAMICAL PROPERTIES OF THE
COSINE BILLIARD.THEORY V.S. EXPERIMENT. — •G.A.
Luna-Acosta 1,2 , U. Kuhl 1 , J.A. Mendez-Bermudez 3 und H.-J.
Stöckmann 1 — 1 Fachbereich Physik der Philipps Universität Marburg,
Renthof 5,D-35032 — 2 Instituto de Fisica, BUAP, Puebla, Mexico. —
3 Max Planck Institute für Strömungsforschung, Göttingen.
We investigate the properties of waves and particles reflected by and
transmitted through 2D chaotic waveguides, using the cosine billiard