Hidden variables in the critical region

Abstract

A gas in the one-phase region near the critical point exhibits unusually large fluctuations of density in volume elements much larger in linear dimension than are molecular diameters. These fluctuations in density give rise to forces and energy fluxes which may be treated by essentially macroscopic equations of thermodynamics and hydrodynamics, because the dominant wavelengths are so large in a Fourier decomposition of the density fluctuation. The anomalous thermal conductivity and shear viscosity of a gas near the critical point have been calculated, and compared with experiments on CO₂. The comparison of thermal conductivities is satisfactory, but the comparison of shear viscosities is inconclusive, because of the smallness of the predicted effect and the difficulty of its measurement.