6,423 research outputs found
A unified model for the dynamics of driven ribbon with strain and magnetic order parameters
We develop a unified model to explain the dynamics of driven one dimensional
ribbon for materials with strain and magnetic order parameters. We show that
the model equations in their most general form explain several results on
driven magnetostrictive metallic glass ribbons such as the period doubling
route to chaos as a function of a dc magnetic field in the presence of a
sinusoidal field, the quasiperiodic route to chaos as a function of the
sinusoidal field for a fixed dc field, and induced and suppressed chaos in the
presence of an additional low amplitude near resonant sinusoidal field. We also
investigate the influence of a low amplitude near resonant field on the period
doubling route. The model equations also exhibit symmetry restoring crisis with
an exponent close to unity. The model can be adopted to explain certain results
on magnetoelastic beam and martensitic ribbon under sinusoidal driving
conditions. In the latter case, we find interesting dynamics of a periodic one
orbit switching between two equivalent wells as a function of an ac magnetic
field that eventually makes a direct transition to chaos under resonant driving
condition. The model is also applicable to magnetomartensites and materials
with two order parameters.Comment: 11 pages, 18 figure
Resonant symmetry lifting in a parametrically modulated oscillator
We study a parametrically modulated oscillator that has two stable states of
vibrations at half the modulation frequency . Fluctuations of the
oscillator lead to interstate switching. A comparatively weak additional field
can strongly affect the switching rates, because it changes the switching
activation energies. The change is linear in the field amplitude. When the
additional field frequency is , the field makes the
populations of the vibrational states different thus lifting the states
symmetry. If differs from , the field modulates the
state populations at the difference frequency, leading to fluctuation-mediated
wave mixing. For an underdamped oscillator, the change of the activation energy
displays characteristic resonant peaks as a function of frequency
Patterns and Collective Behavior in Granular Media: Theoretical Concepts
Granular materials are ubiquitous in our daily lives. While they have been a
subject of intensive engineering research for centuries, in the last decade
granular matter attracted significant attention of physicists. Yet despite a
major efforts by many groups, the theoretical description of granular systems
remains largely a plethora of different, often contradicting concepts and
approaches. Authors give an overview of various theoretical models emerged in
the physics of granular matter, with the focus on the onset of collective
behavior and pattern formation. Their aim is two-fold: to identify general
principles common for granular systems and other complex non-equilibrium
systems, and to elucidate important distinctions between collective behavior in
granular and continuum pattern-forming systems.Comment: Submitted to Reviews of Modern Physics. Full text with figures (2Mb
pdf) avaliable at
http://mti.msd.anl.gov/AransonTsimringReview/aranson_tsimring.pdf Community
responce is appreciated. Comments/suggestions send to [email protected]
Phase space transport in cuspy triaxial potentials: Can they be used to construct self-consistent equilibria?
(Abridged) This paper studies chaotic orbit ensembles evolved in triaxial
generalisations of the Dehnen potential which have been proposed to model
ellipticals with a strong density cusp that manifest significant deviations
from axisymmetry. Allowance is made for a possible supermassive black hole, as
well as low amplitude friction, noise, and periodic driving which can mimic
irregularities associated with discreteness effects and/or an external
environment. The degree of chaos is quantified by determining how (1) the
relative number of chaotic orbits and (2) the size of the largest Lyapunov
exponent depend on the steepness of the cusp and the black hole mass, and (3)
the extent to which Arnold webs significantly impede phase space transport,
both with and without perturbations. In the absence of irregularities, chaotic
orbits tend to be extremely `sticky,' so that different pieces of the same
chaotic orbit can behave very differently for 10000 dynamical times or longer,
but even very low amplitude perturbations can prove efficient in erasing many
-- albeit not all -- these differences. The implications thereof are discussed
both for the structure and evolution of real galaxies and for the possibility
of constructing approximate near-equilibrium models using Schwarzschild's
method. Much of the observed qualitative behaviour can be reproduced with a toy
potential given as the sum of an anisotropic harmonic oscillator and a
spherical Plummer potential, which suggests that the results may be generic.Comment: 18 pages, including 19 figures; Accepted for publication by MNRAS;
higher quality figures available from
http://www.astro.ufl.edu/~siopis/papers
Trapped ions in optical lattices for probing oscillator chain models
We show that a chain of trapped ions embedded in microtraps generated by an
optical lattice can be used to study oscillator models related to dry friction
and energy transport. Numerical calculations with realistic experimental
parameters demonstrate that both static and dynamic properties of the ion chain
change significantly as the optical lattice power is varied. Finally, we lay
out an experimental scheme to use the spin degree of freedom to probe the phase
space structure and quantum critical behavior of the ion chain
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