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Summary: Entropy Production and Time Asymmetry in Nonequilibrium Fluctuations
D. Andrieux and P. Gaspard
Center for Nonlinear Phenomena and Complex Systems, Universite´ Libre de Bruxelles, Code Postal 231, Campus Plaine,
B-1050 Brussels, Belgium
S. Ciliberto, N. Garnier, S. Joubaud, and A. Petrosyan
Laboratoire de Physique, CNRS UMR 5672, Ecole Normale Supe´rieure de Lyon, 46 Alle´e d'Italie, 69364 Lyon Ce´dex 07, France
(Received 27 November 2006; published 10 April 2007)
The time-reversal symmetry of nonequilibrium fluctuations is experimentally investigated in two out-
of-equilibrium systems: namely, a Brownian particle in a trap moving at constant speed and an electric
circuit with an imposed mean current. The dynamical randomness of their nonequilibrium fluctuations is
characterized in terms of the standard and time-reversed entropies per unit time of dynamical systems
theory. We present experimental results showing that their difference equals the thermodynamic entropy
production in units of Boltzmann's constant.
DOI: 10.1103/PhysRevLett.98.150601 PACS numbers: 05.70.Ln, 02.50.Ey, 05.40.ÿa
Newton's equations ruling the motion of particles in
matter are known to be time-reversal symmetric. Yet mac-
roscopic processes present irreversible behavior in which
entropy is produced according to the second law of ther-
modynamics. Recent works suggest that this thermody-
namic time asymmetry could be understood in terms
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