664 research outputs found
Dynamics and Scaling of Noise-Induced Domain Growth
The domain growth processes originating from noise-induced nonequilibrium
phase transitions are analyzed, both for non-conserved and conserved dynamics.
The existence of a dynamical scaling regime is established in the two cases,
and the corresponding growth laws are determined. The resulting universal
dynamical scaling scenarios are those of Allen-Cahn and Lifshitz-Slyozov,
respectively. Additionally, the effect of noise sources on the behaviour of the
pair correlation function at short distances is studied.Comment: 11 pages (including 13 figures) LaTeX file. Accepted in EPJ
Spatial Coherence Resonance near Pattern-Forming Instabilities
The analogue of temporal coherence resonance for spatial degrees of freedom
is reported. Specifically, we show that spatiotemporal noise is able to
optimally extract an intrinsic spatial scale in nonlinear media close to (but
before) a pattern-forming instability. This effect is observed in a model of
pattern-forming chemical reaction and in the Swift-Hohenberg model of fluid
convection. In the latter case, the phenomenon is described analytically via an
approximate approach.Comment: 4 pages, 4 figure
Coherence and synchronization in diode-laser arrays with delayed global coupling
The dynamics of a semiconductor-laser array whose individual elements are
coupled in a global way through an external mirror is numerically analysed. A
coherent in-phase solution is seen to be preferred by the system at
intermediate values of the feedback coupling strength. At low values of this
parameter, a strong amplification of the spontaneous emission noise is
observed. A tendency towards chaos synchronization is also observed at large
values of the feedback strength.Comment: 8 pages, LaTeX, 6 PS figures, to appear in International Journal of
Bifurcation and Chao
Self-sustained spatiotemporal oscillations induced by membrane-bulk coupling
We propose a novel mechanism leading to spatiotemporal oscillations in
extended systems that does not rely on local bulk instabilities. Instead,
oscillations arise from the interaction of two subsystems of different spatial
dimensionality. Specifically, we show that coupling a passive diffusive bulk of
dimension d with an excitable membrane of dimension d-1 produces a
self-sustained oscillatory behavior. An analytical explanation of the
phenomenon is provided for d=1. Moreover, in-phase and anti-phase
synchronization of oscillations are found numerically in one and two
dimensions. This novel dynamic instability could be used by biological systems
such as cells, where the dynamics on the cellular membrane is necessarily
different from that of the cytoplasmic bulk.Comment: Accepted for publication in Physical Review Letter
Localization lengths of ultrathin disordered gold and silver nanowires
The localization lengths of ultrathin disordered Au and Ag nanowires are
estimated by calculating the wire conductances as functions of wire lengths. We
study Ag and Au monoatomic linear chains, and thicker Ag wires with very small
cross sections. For the monoatomic chains we consider two types of disorder:
bounded random fluctuations of the interatomic distances, and the presence of
random substitutional impurities. The effect of impurity atoms on the nanowire
conductance is much stronger. Our results show that electrical transport in
ultrathin disordered wires may occur in the strong localization regime, and
with relatively small amounts of disorder the localization lengths may be
rather small. The localization length dependence on wire thickness is
investigated for Ag nanowires with different impurity concentrations.Comment: 6 pages, postscript figures included, submitted to PR
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