Dynamics of Entropy Fluctuations in a Critical Binary Mixture

Using a very sophisticated light-beating spectrometer and a new correlation technique, we have measured the relaxation time of entropy fluctuations in a critical binary mixture in the reduced temperature range of 4×10^-6<~t<~10^-1. In the hydrodynamic regime this relaxation time, which is proportional to the specific heat at constant pressure and critical concentration, is found to behave as t^-α(1+Bt⁺ˣ) with a critical exponent α=0.059±0.003 and x=1.05±0.15.