524 research outputs found
Probing an nonequilibrium Einstein relation in an aging colloidal glass
We present a direct experimental measurement of an effective temperature in a
colloidal glass of Laponite, using a micrometric bead as a thermometer. The
nonequilibrium fluctuation-dissipation relation, in the particular form of a
modified Einstein relation, is investigated with diffusion and mobility
measurements of the bead embedded in the glass. We observe an unusual
non-monotonic behavior of the effective temperature : starting from the bath
temperature, it is found to increase up to a maximum value, and then decreases
back, as the system ages. We show that the observed deviation from the Einstein
relation is related to the relaxation times previously measured in dynamic
light scattering experiments.Comment: 4 pages, 4 figures, corrected references, published in Phys. Rev.
Lette
On chaotic behavior of gravitating stellar shells
Motion of two gravitating spherical stellar shells around a massive central
body is considered. Each shell consists of point particles with the same
specific angular momenta and energies. In the case when one can neglect the
influence of gravitation of one ("light") shell onto another ("heavy") shell
("restricted problem") the structure of the phase space is described. The
scaling laws for the measure of the domain of chaotic motion and for the
minimal energy of the light shell sufficient for its escape to infinity are
obtained.Comment: e.g.: 12 pages, 8 figures, CHAOS 2005 Marc
Escaping from nonhyperbolic chaotic attractors
We study the noise-induced escape process from chaotic attractors in
nonhyperbolic systems. We provide a general mechanism of escape in the low
noise limit, employing the theory of large fluctuations. Specifically, this is
achieved by solving the variational equations of the auxiliary Hamiltonian
system and by incorporating the initial conditions on the chaotic attractor
unambiguously. Our results are exemplified with the H{\'e}non and the Ikeda map
and can be implemented straightforwardly to experimental data.Comment: replaced with published versio
Solving procedure for a twenty-five diagonal coefficient matrix: direct numerical solutions of the three dimensional linear Fokker-Planck equation
We describe an implicit procedure for solving linear equation systems
resulting from the discretization of the three dimensional (seven variables)
linear Fokker-Planck equation. The discretization of the Fokker-Planck equation
is performed using a twenty-five point molecule that leads to a coefficient
matrix with equal number of diagonals. The method is an extension of Stone's
implicit procedure, includes a vast class of collision terms and can be applied
to stationary or non stationary problems with different discretizations in
time. Test calculations and comparisons with other methods are presented in two
stationary examples, including an astrophysical application for the
Miyamoto-Nagai disk potential for a typical galaxy.Comment: 20 pages, RevTex, no proofreading, accepted in Journal of
Computational Physic
Quadratic Volume Preserving Maps
We study quadratic, volume preserving diffeomorphisms whose inverse is also
quadratic. Such maps generalize the Henon area preserving map and the family of
symplectic quadratic maps studied by Moser. In particular, we investigate a
family of quadratic volume preserving maps in three space for which we find a
normal form and study invariant sets. We also give an alternative proof of a
theorem by Moser classifying quadratic symplectic maps.Comment: Ams LaTeX file with 4 figures (figure 2 is gif, the others are ps
Core Collapse via Coarse Dynamic Renormalization
In the context of the recently developed "equation-free" approach to
computer-assisted analysis of complex systems, we extract the self-similar
solution describing core collapse of a stellar system from numerical
experiments. The technique allows us to side-step the core "bounce" that occurs
in direct N-body simulations due to the small-N correlations that develop in
the late stages of collapse, and hence to follow the evolution well into the
self-similar regime.Comment: 5 pages, 3 figure
Nambu-Hamiltonian flows associated with discrete maps
For a differentiable map that has
an inverse, we show that there exists a Nambu-Hamiltonian flow in which one of
the initial value, say , of the map plays the role of time variable while
the others remain fixed. We present various examples which exhibit the map-flow
correspondence.Comment: 19 page
Chaos and Rotating Black Holes with Halos
The occurrence of chaos for test particles moving around a slowly rotating
black hole with a dipolar halo is studied using Poincar\'e sections. We find a
novel effect, particles with angular momentum opposite to the black hole
rotation have larger chaotic regions in phase space than particles initially
moving in the same direction.Comment: 9 pages, 4 Postscript figures. Phys. Rev. D, in pres
The Tidal Tails of the Ultra-Faint Globular Cluster Palomar 1
Using the Optimal Filter Technique applied to Sloan Digital Sky Survey
photometry, we have found extended tails stretching about 1 degree (or several
tens of half-light radii) from either side of the ultra-faint globular cluster
Palomar 1. The tails contain roughly as many stars as does the cluster itself.
Using deeper Hubble Space Telescope data, we see that the isophotes twist in a
chacteristic S-shape on moving outwards from the cluster centre to the tails.
We argue that the main mechanism forming the tails may be relaxation driven
evaporation and that Pal 1 may have been accreted from a now disrupted dwarf
galaxy ~500 Myr ago.Comment: 6 figures, accepted for publication in MNRAS Letters Changes in v2:
Merged previous figures 3 and 5 and slightly expanded discussio
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