6,342 research outputs found
Collective motion occurs inevitably in a class of populations of globally coupled chaotic elements
We discovered numerically a scaling law obeyed by the amplitude of collective
mo tion in large populations of chaotic elements. Our analysis strongly
suggests that such populations generically exhibit collective motion in the
presence of interaction, however weak it may be. A phase diagram for the
collective motion, which is characterized by peculiar structures similar to
Arnold tongues, is obtained.Comment: 6 pages, 9 Postscript figures, uses revtex.st
Thermodynamic Irreversibility from high-dimensional Hamiltonian Chaos
This paper discusses the thermodynamic irreversibility realized in
high-dimensional Hamiltonian systems with a time-dependent parameter. A new
quantity, the irreversible information loss, is defined from the Lyapunov
analysis so as to characterize the thermodynamic irreversibility. It is proved
that this new quantity satisfies an inequality associated with the second law
of thermodynamics. Based on the assumption that these systems possess the
mixing property and certain large deviation properties in the thermodynamic
limit, it is argued reasonably that the most probable value of the irreversible
information loss is equal to the change of the Boltzmann entropy in statistical
mechanics, and that it is always a non-negative value. The consistency of our
argument is confirmed by numerical experiments with the aid of the definition
of a quantity we refer to as the excess information loss.Comment: LaTeX 43 pages (using ptptex macros) with 11 figure
Kink Solution in a Fluid Model of Traffic Flows
Traffic jam in a fluid model of traffic flows proposed by Kerner and
Konh\"auser (B. S. Kerner and P. Konh\"auser, Phys. Rev. E 52 (1995), 5574.) is
analyzed. An analytic scaling solution is presented near the critical point of
the hetero-clinic bifurcation. The validity of the solution has been confirmed
from the comparison with the simulation of the model.Comment: RevTeX v3.1, 6 pages, and 2 figure
A heat pump at a molecular scale controlled by a mechanical force
We show that a mesoscopic system such as Feynman's ratchet may operate as a
heat pump, and clarify a underlying physical picture. We consider a system of a
particle moving along an asymmetric periodic structure . When put into a
contact with two distinct heat baths of equal temperature, the system transfers
heat between two baths as the particle is dragged. We examine Onsager relation
for the heat flow and the particle flow, and show that the reciprocity
coefficient is a product of the characteristic heat and the diffusion constant
of the particle. The characteristic heat is the heat transfer between the baths
associated with a barrier-overcoming process. Because of the correlation
between the heat flow and the particle flow, the system can work as a heat pump
when the particle is dragged. This pump is particularly effective at molecular
scales where the energy barrier is of the order of the thermal energy.Comment: 7 pages, 5 figures; revise
Capture of free-flying payloads with flexible space manipulators
A recently developed control system for capturing free-flying payloads with flexible manipulators is discussed. Three essential points in this control system are, calculating optimal path, using a vision sensor for an external sensor, and controlling active vibration. Experimental results are shown using a planar flexible manipulator
Posterior probability and fluctuation theorem in stochastic processes
A generalization of fluctuation theorems in stochastic processes is proposed.
The new theorem is written in terms of posterior probabilities, which are
introduced via the Bayes theorem. In usual fluctuation theorems, a forward path
and its time reversal play an important role, so that a microscopically
reversible condition is essential. In contrast, the microscopically reversible
condition is not necessary in the new theorem. It is shown that the new theorem
adequately recovers various theorems and relations previously known, such as
the Gallavotti-Cohen-type fluctuation theorem, the Jarzynski equality, and the
Hatano-Sasa relation, when adequate assumptions are employed.Comment: 4 page
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