Colloquium on December 7, 2009

Andreas Engel
University of Oldenburg

Non-equilibrium work and fluctuation theorems

The general theoretical description of systems driven violently away from thermodynamic equilibrium is still an open problem. Whereas equilibrium situations are comprehensively characterized by a small number of general principles, and near-equilibrium processes can be modeled within the framework of linear-response theory the extreme diversity of phenomena which occur far from equilibrium has up to now precluded a coherent theoretical description.

Nevertheless, a set of simple, exact and general relations have been established recently which apply to systems driven arbitrarily far from thermal equilibrium. These relations are by now referred to as fluctuation and work theorems respectively, and are in particular relevant for small systems with energies of the order of the thermal energy k_B T. Somewhat complementary to the traditional emphasis of statistical mechanics on averages these theorems focus on the large deviation properties of particular observables. They offer a fresh view on some classical problems in non-equilibrium statistical mechanics, open interesting possibilities for further developements, and have motivated new experimental techniques and numerical algorithms.

The talk gives an introduction to the general issue and discusses some special recent applications.