Comment on "Acoustics of tachyon Fermi gas" [E. Trojan and G.V. Vlasov, arXiv:1103.2276 (hep-ph)]

TL;DR

This paper refutes previous claims by demonstrating that an ideal Fermi gas of tachyons always has a subluminal sound velocity, ensuring causality and preventing exotic equations of state.

Contribution

It provides a corrected analysis showing tachyon Fermi gases are always causal and do not exhibit superluminal sound speeds or exotic pressure-energy relations.

Findings

Sound velocity is always subluminal for tachyon Fermi gases.

Causality condition holds at all particle densities.

Tachyon Fermi gases do not have pressure exceeding energy density.

Abstract

In contrast to Trojan and Vlasov [arXiv:1103.2276 (hep-ph)], it is found that an ideal Fermi gas of tachyons has a subluminous velocity of sound for any particle density and, therefore, the causality condition for a tachyon gas holds always true. Also, an ideal Fermi gas of tachyons never possesses an exotic equation of state with the pressure exceeding the energy density.