QUASI-SIMPLE SECONDARY WAVES IN A GAS OF QUASI-PARTICLES

=θ ( 0 T is the equilibrium temperature) and chemical potential μ , if the number of quasiparticles at interactions is kept constant. In the linear approximation, this system of equations describes, in certain circumstances, the weakly attenuating secondary waves [1, 2] being similar to the second sound waves in He II [3]. These waves relate to a hyperbolic type, i.e. their dispersion is absent. The paper deals with the nonlinear secondary waves in a gas of quasi-particles, which are described by a system of non-linear equations of gas dynamics of quasi-particles in the second approximation. This system of equations is similar to the system of non-linear equations of gas dynamics of particles, describing the propagation of non-linear acoustic waves in a medium without dispersion [4-6]. Using this system of equations for the one-dimensional case, when there is no dissipation, we can derive an equation describing simple Riemann waves. Taking into account the dissipative processes one can find the generalized Burgers equation describing quasi-simple waves. These waves are featured by the distortion of their profiles, like, for example, in the case of a periodic wave - a sawtooth profile is formed.