Most physical systems are not in equilibrium, but rather are subject to driving and/or dissipation. Far from equilibrium, where nonlinear effects become important, these systems display a rich array of complex behaviors. Systems can be dynamic, chaotic, or turbulent, and more remarkably can produce static patterns or exhibit persistent dynamics while remaining statistically stationary. Although there is typically no free-energy-like functional to minimize in a nonequilibrium system, quantities analogous to those used in equilibrium statistical mechanics can often elucidate the mean behavior.
Current experiments address: