Local order effects on the dynamics of fluids near the liquid-gas critical point

Local order effects on the dynamical properties of critical fluids are taken into account by introducing a new slowly varying tensorial quantity which is related to the angular momentum of a group of correlated molecules. The theory is applied to an analysis of ultrasonic and light scattering measurements. The presence of two central Lorentzians is predicted and the properties of the broader Lorentzian are successfully described. A preliminary comparison of the theory with experiment is encouraging.