Large deviations in non-equilibrium systems

Over the last 30 years the study of large deviations has become a central aspect in the theory of non-equilibrium systems. They give a generalization of the concept of free energy for non-equilibrium systems. They also give a way to generalize the fluctuation dissipation theorem and to give a probablistic understanding of the Second Law. A number of methods have been developed to calculate these large deviations, in particular a field theory called the Macroscopic Fluctuation Theory which has become the main tool to determine these large deviations for non-equilibrium systems.