SHELL-LIKE STRUCTURES IN AN EXPANDING QUARK-ANTIQUARK PLASMA

The particle density distribution emerging from the solution of the Vl asov equation for relativistic, noninteracting particles with spherica lly symmetric initial conditions is shown to exhibit a shell-like stru cture for late fixed times in the center-of-mass (CM) frame of the sys tem. A similar phenomenon was recently observed employing the test-par ticle method to solve the Vlasou equation for quarks with Nambu-Jona-L asinio-type interactions, and was attributed to the attractive forces among the particles. Contrary to this claim, it is demonstrated here t hat this effect is of purely relativistic origin and is sensitive only to the mass of the particles and their initial phase-space distributi on.