Eigenmodes of Classical Fluids in Thermal Equilibrium

摘要

The eigenmodes of a classical fluid in thermal equilibrium are discussed. For long wavelengths and times, they can be computed from linear hydrodynamic equations. They are then the hydrodynamic modes, in particular, the heat mode, which describes the diffusion of heat in the fluid and two sound modes. For short wavelengths and times they can be derived from linear kinetic operators. For low densities, the linear Boltzmann operator can be employed and the three most important eigenmodes are direct extensions of the kinetic analogues of the heat and sound modes. For high densities, a generalization of the Boltzmann operator is used. The most important eigenmode is the extended heat mode, while next in importance come two eigenmodes that are extensions of the sound modes. These three extended hydrodynamic modes can be used to obtain the light and neutron spectra of fluids and vice versa. 42 refs., 8 figs. (ERA citation 11:052441)