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Fluctuations in out of equilibrium systems : from theory to experiment

Sergio Ciliberto

Mercredi 23 mai 2012

à 11h en salle C. Brot

The study of the fluctuations in out of equilibrium systems is a subject of current interest ranging from the dynamical systems to the stochastic ones. In this talk we will discuss the problem of the fluctuations of the injected and dissipated power in these systems. There are only a few theoretical results, which may predict several statistical properties of these fluctuations. This is the case of the Fluctuation Theorem (FT), which has been first found in the context of dynamical systems and later extended to stochastic ones. The proof relies upon several hypotheses which merit to be tested experimentally. We will focus on stochastic systems dominated by thermal fluctuations and we will discuss them from the experimental point of view. We describe a rather general case, that is the work fluctuations of an oscillator in contact with a heat reservoir and driven out of equilibrium by an external force. We also consider de fluctuations of the heat dissipated towards the heat bath. The experimental analysis in the context of Fluctuation Theorem (FT) allows us to recall the general properties of this theorem and its importance for experimental systems. We discuss the finite time corrections that depend on the observable and show that for the total entropy production rate the FT is verified for all times. The role of non-linearities is considered by briefly describing the experimental results of a Brownian particle confined in a non double well potential and driven out of equilibrium by an external force. We finally describe the important consequences of FT and some useful applications to the analysis of experimental data.

Voir en ligne : ENS Lyon