Korteweg - de Vries solitons in relativistic hydrodynamics

In a previous work, assuming that the nucleus can be treated as a perfect fluid, we have studied the propagation of perturbations in the baryon density. For a given equation of state we have derived a Korteweg - de Vries (KdV) equation from Euler and continuity equations in non-relativistic hydrodynamics. Here, using a more general equation of state, we extend our formalism to relativistic hydrodynamics.