19 research outputs found
Dynamical behavior of a dissipative particle in a periodic potential subject to chaotic noise: Retrieval of chaotic determinism with broken parity
Dynamical behaviors of a dissipative particle in a periodic potential subject
to chaotic noise are reported. We discovered a macroscopic symmetry breaking
effect of chaotic noise on a dissipative particle in a multi-stable systems
emerging, even when the noise has a uniform invariant density with parity
symmetry and white Fourier spectrum. The broken parity symmetry of the
multi-stable potential is not necessary for the dynamics with broken symmetry.
We explain the mechanism of the symmetry breaking and estimate the average
velocity of a particle under chaotic noise in terms of unstable fixed points.Comment: 4 pages, 7 Postscript figures (Revtex, tar+compress+uuencode); to
appear in Phys.Rev.Let
Timely pandemic countermeasures reduce both health damage and economic loss: Generality of the exact solution
Balancing pandemic control and economics is challenging, as the numerical
analysis assuming specific economic conditions complicates obtaining
predictable general findings. In this study, we analytically demonstrate how
adopting timely moderate measures helps reconcile medical effectiveness and
economic impact, and explain it as a consequence of the general finding of
``economic irreversibility" by comparing it with thermodynamics. A general
inequality provides the guiding principles on how such measures should be
implemented. The methodology leading to the exact solution is a novel
theoretical contribution to the econophysics literature.Comment: 6 pages, 4 figure
Effect of time-correlation of input patterns on the convergence of on-line learning
We studied the effects of time correlation of subsequent patterns on the
convergence of on-line learning by a feedforward neural network with
backpropagation algorithm. By using chaotic time series as sequences of
correlated patterns, we found that the unexpected scaling of converging time
with learning parameter emerges when time-correlated patterns accelerate
learning process.Comment: 8 pages(Revtex), 5 figure
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Adaptation-induced collective dynamics of a single-cell protozoan
We investigate the behavior of a single-cell protozoan in a narrow tubular ring. This environment forces them to swim under a one-dimensional periodic boundary condition. Above a critical density, single-cell protozoa aggregate spontaneously without external stimulation. The high-density zone of swimming cells exhibits a characteristic collective dynamics including translation and boundary fluctuation. We analyzed the velocity distribution and turn rate of swimming cells and found that the regulation of the turing rate leads to a stable aggregation and that acceleration of velocity triggers instability of aggregation. These two opposing effects may help to explain the spontaneous dynamics of collective behavior. We also propose a stochastic model for the mechanism underlying the collective behavior of swimming cells
Energetics of Forced Thermal Ratchet
Molecular motors are known to have the high efficiency of energy
transformation in the presence of thermal fluctuation.
Motivated by the surprising fact, recent studies of thermal ratchet models
are showing how and when work should be extracted from non-equilibrium
fluctuations.
One of the important finding was brought by Magnasco where he studied the
temperature dependence on the fluctuation-induced current in a ratchet
(multistable) system and showed that the current can generically be maximized
in a finite temperature.
The interesting finding has been interpreted that thermal fluctuation is not
harmful for the fluctuation-induced work and even facilitates its efficiency.
We show, however, this interpretation turns out to be incorrect as soon as we
go into the realm of the energetics
[Sekimoto,J.Phys.Soc.Jpn.66,1234-1237(1997)]: the efficiency of energy
transformation is not maximized at finite temperature, even in the same system
that Magnasco considered. The maximum efficiency is realized in the absence of
thermal fluctuation. The result presents an open problem whether thermal
fluctuation could facilitate the efficiency of energetic transformation from
force-fluctuation into work.Comment: 3pages, 4sets of figure
Effect of Chaotic Noise on Multistable Systems
In a recent letter [Phys.Rev.Lett. {\bf 30}, 3269 (1995), chao-dyn/9510011],
we reported that a macroscopic chaotic determinism emerges in a multistable
system: the unidirectional motion of a dissipative particle subject to an
apparently symmetric chaotic noise occurs even if the particle is in a
spatially symmetric potential. In this paper, we study the global dynamics of a
dissipative particle by investigating the barrier crossing probability of the
particle between two basins of the multistable potential. We derive
analytically an expression of the barrier crossing probability of the particle
subject to a chaotic noise generated by a general piecewise linear map. We also
show that the obtained analytical barrier crossing probability is applicable to
a chaotic noise generated not only by a piecewise linear map with a uniform
invariant density but also by a non-piecewise linear map with non-uniform
invariant density. We claim, from the viewpoint of the noise induced motion in
a multistable system, that chaotic noise is a first realization of the effect
of {\em dynamical asymmetry} of general noise which induces the symmetry
breaking dynamics.Comment: 14 pages, 9 figures, to appear in Phys.Rev.
Inattainability of Carnot efficiency in the Brownian heat engine
We discuss the reversibility of Brownian heat engine. We perform asymptotic
analysis of Kramers equation on B\"uttiker-Landauer system and show
quantitatively that Carnot efficiency is inattainable even in a fully
overdamping limit. The inattainability is attributed to the inevitable
irreversible heat flow over the temperature boundary.Comment: 5 pages, to appear in Phys. Rev.
The Carnot Cycle for Small Systems: Irreversibility and the Cost of Operations
We employ the recently developed framework of the energetics of stochastic
processes (called `stochastic energetics'), to re-analyze the Carnot cycle in
detail, taking account of fluctuations, without taking the thermodynamic limit.
We find that both processes of connection to and disconnection from heat
baths and adiabatic processes that cause distortion of the energy distribution
are sources of inevitable irreversibility within the cycle. Also, the so-called
null-recurrence property of the cumulative efficiency of energy conversion over
many cycles and the irreversible property of isolated, purely mechanical
processes under external `macroscopic' operations are discussed in relation to
the impossibility of a perpetual machine, or Maxwell's demon.Comment: 11 pages with 3 figures. Resubmitted to Physical Review E. Many
paragraphs have been modifie