Nonuniversal Dynamical Crossover in Pure and Binary Fluids near a Critical Point

We compare the results of dynamical renormalization group theory with experiments in the nonasymptotic region at second order phase transitions in liquids and mixtures. Agreement is found with a parameter free prediction of the full temperature dependence of transport coefficients and first sound attenuation after fitting one transport coefficient (e.g., shear viscosity). Differences in the nonuniversal behavior between fluids and mixtures appear due to the flow of a dynamical parameter neglected in the mixtures so far.