Related Experiment Video
Updated: Apr 25, 2026

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Condensation of fluctuations in and out of equilibrium
Marco Zannetti1, Federico Corberi2, Giuseppe Gonnella3
1Dipartimento di Fisica "E.R. Caianiello" and CNISM Unità di Salerno, Università di Salerno, via Ponte don Melillo, 84084 Fisciano (SA), Italy and Kavli Institute for Theoretical Physics China, CAS, Beijing 100190, China.
Abstract:
Condensation of fluctuations is an interesting phenomenon conceptually distinct from condensation on average. One striking feature is that, contrary to what happens on average, condensation of fluctuations may occur even in the absence of interaction. The explanation emerges from the duality between large deviation events in the given system and typical events in a new and appropriately biased system. This phenomenon is investigated in the context of the Gaussian model, chosen as a paradigmatical noninteracting system, before and after an instantaneous temperature quench. It is shown that the bias induces a mean-field-like effective interaction responsible for the condensation on average. Phase diagrams, covering both the equilibrium and the off-equilibrium regimes, are derived for observables representative of generic behaviors.
Related Concept Videos
Phase Transitions: Vaporization and Condensation
Phase Transitions: Sublimation and Deposition
Solution Equilibrium and Saturation
Entropy
Entropy
When an ideal gas expands isothermally, the disorder in the gas increases. From the molecular perspective, the gas molecules have more volume to move around in.
Consider an infinitesimal step in the expansion, which...
Oscillations about an Equilibrium Position

