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Subsonic Potentials in Ultradense Plasmas

Abstract The existence of the subsonic dynamic potential for a test charge in extremely dense quantum plasmas is pointed out for the first time. The dispersion equation of ion acoustic wave in relativistic plasmas is derived by using the quantum hydrodynamic model. The relativistic electrons obey Fermi statistics, whereas the ions are taken classically. The standard model of wake potential is hereafter applied for the derivation of dynamic potential of the test particle. A usual supersonic potential is found suppressed. However, the oscillatory subsonic wake potential does exist in small length scales. The analytical results are applied in different regions by taking the range of magnetic field as well as the electron number density. It is found that the dynamic potential exists only when vt < Cs, showing the presence of subsonic wake potential contrary to the usual supersonic condition vt > Cs. Here vt is the test particle speed and Cs is the acoustic speed defined by the Fermi temperature of the electrons. This work is significant in order to describe the structure formation in the astrophysical environment and laboratory dense plasmas.