Propagation of infinitesimal disturbances in a gas according to a relativistic kinetic model (Q1057157)

A simple relativistic kinetic-theory model of a gas is considered in this paper with a special attention to the propagation of infinitesimally small disturbances. The dispersion relation is discussed on the basis of a special-relativistic version of the BGK model. A continuous spectrum is exhibited for the complex wave vector. However, an asymptotic analysis indicates the possibility of isolating a sort of discrete spectrum embedded in the continuum as frequency goes asymptotically to zero. This is in agreement with the results obtained by a direct formal expansion of the solution of the linearized Boltzmann equation. The paper is well documented and well written.