Heat fluctuations in an out of equilibrium bath
  We measure the energy fluctuations of a Brownian particle confined by an optical trap in an aging gelatin after a very fast quench (less than 1 ms). The strong nonequilibrium fluctuations due to the assemblage of the gel, are interpreted, within the framework of fluctuation theorem, as a heat flux from the particle towards the bath. We derive, from a simple model, an analytical expression of the heat probability distribution, which fits the experimental data and satisfies a fluctuation relation similar to that of a system in contact with two baths at different temperatures. 
Juan Ruben Gomez-Solano (Phys-ENS), Artyom Petrosyan (Phys-ENS),   Sergio Ciliberto (Phys-ENS)
cond-mat.stat-mech