Microscopic theory of relaxation processes in systems of particles interacting with the hydrodynamic medium

Abstract

Our work considers spatially nonuniform states of particles, weakly interacting with a hydrodynamic medium. We developed a microscopic theory, describing such systems involving Bogolubov’s reduced description method. It was shown that such systems have both kinetic and hydrodynamic stages of evolution. At the kinetic stage of evolution the one-particle distribution function is a reduced description parameter for particles, and, therefore, a medium is described by five hydrodynamic parameters (density, temperature, and velocity). The coupled system of equations of motion describing the system on the kinetic stage of evolution was obtained on the basis of Bogolubov’s reduced description method. The transition from the kinetic to hydrodynamic stage of evolution for particles interacting with the medium was also studied within the reduced description method. It was shown that on the hydrodynamic stage the only description parameter of particles is their density, although the medium is still described by five hydrodynamic variables. Consequently, a coupled system of equations, which completely describe the evolution of the system under consideration on the hydrodynamic stage, including dissipation processes, was obtained. These equations were used to study the propagation of acoustic waves in our system. Also the influence of particles on relaxation processes was discussed. The obtained equations, for example, may be used to describe the neutrons propagating in a hydrodynamic medium without multiplication and capture.