|
Résumé |
A system, subject to continuous exchanges of matter, energy or information with its surroundings, may reach a non-equilibrium steady state in which various currents break time-reversal invariance and continuously generate entropy. Such a state can not be accounted for by the Principles of Thermodynamics or the Gibbs-Boltzmann laws of statistical physics. Besides, linear response theory and the Onsager-Machlup functional provide useful descriptions of large scale fluctuations in such driven systems only at first order, in the vicinity of equilibrium.
In the last two decades, important advances in our understanding of processes far from equilibrium have been achieved, for which rare events, large deviations and Fluctuations relations provide a unified framework. The emergence of universal features can be studied thanks to a variational principle, proposed by G. Jona-Lasinio and his collaborators, known as the Macroscopic Fluctuation Theory (MFT). In this theory, optimal fluctuations far from equilibrium are determined at a coarse-grained scale by two coupled non-linear hydrodynamic equations. The objective of this talk is to present these concepts and to illustrate them with some exact solutions of the MFT equations. |
