Fluctuations in Nonequilibrium Statistical Mechanics

The fluctuations in nonequilibrium systems are under intense theoretical and experimental investigation. Topical ``fluctuation relations'' describe symmetries of the statistical properties of certain observables, in a variety of models and phenomena. They have been derived in deterministic and, later, in stochastic frameworks. After presenting an introduction of the fluctuation theorems for the transient response and the steady state, we present and discuss recent exact results for the behavior of thermodynamic fluctuations out of equilibrium. The convergence properties of different thermodynamic and dynamic measures, as well as the physical mechanisms underlying this behavior, will also be discussed.