H. Gouin, MATERIAL WAVES FOR FLUID INTERFACES IN TH E VICINITY OF THE CRITICAL-POINT, Comptes rendus de l'Academie des sciences. Serie 2, Mecanique, physique, chimie, sciences de l'univers, sciences de la terre, 317(10), 1993, pp. 1263-1268
A non-linear model associated with a Landau-Ginzburg-like behaviour in
mean-field approximation forecasts solitary wave for fluids near the
critical point. Above the critical temperature, the solitary waves can
only be supersonic with respect to the isothermal acoustic speed.