The Fluctuation Theorem and its Implications for Materials Processing and Modeling

Abstract

Thermodynamics describes the framework within which all macroscopic processes operate. Until the discovery of the Fluctuation Theorem [1], there was no equivalent framework for small (nano) systems observed for short times. The Fluctuation Theorem provides a generalisation of the Second Law of thermodynamics, that applies to finite systems observed over finite times. The Second Law of thermodynamics states that for all macroscopic processes the total entropy of the Universe can only increase. The Fluctuation Theorem says that for finite systems, the probability ratio that for a finite time the entropy decreases rather than increases, vanishes exponentially with system size and observation time. Thus in the so-called “thermodynamic limit”, the entropy can only increase and we obtain the Second Law.