 Onsager–Machlup function

The Onsager–Machlup function is a mathematical formulation that describes the fluctuations of thermodynamic systems in nonequilibrium states. It was introduced by Lars Onsager and Gregory E. Machlup in the context of statistical mechanics and thermodynamics. The function plays a significant role in the study of the dynamics of systems that are not in equilibrium, particularly those exhibiting stochastic behaviors.