The Fluctuation Theorem is a significant result in statistical mechanics and nonequilibrium thermodynamics that describes the likelihood of observing certain fluctuations in the thermodynamic properties of systems far from equilibrium. It provides a mathematical framework for understanding how thermodynamic quantities, such as entropy, deviate from their average values during fluctuations in small systems.
Articles by others on the same topic
A fluctuation theorem compares the probability of a fluctuating sample trajectory with that of its reverse. Positive mean entropy production permits negative individual realizations: what is constrained is their relative probability, not a prohibition on every reversal. The finite statement below compares specified forward and reverse probability laws; replacing the reverse law by the forward law requires an additional symmetry. The biased-step entropy production model exhibits that symmetry exactly, while the Crooks fluctuation theorem compares two different driving protocols.