Tachyonic thermal excitations and causality

Abstract

We consider an ideal Fermi gas of tachyonic thermal excitations as a continuous medium and establish when it satisfies the causality condition. At high temperature the sound speed is always subluminal c s < 1, but there is no stable form of tachyon matter below the critical temperature T < T c = 0.23m that depends on the tachyon mass m. The pressure P and energy density E cannot be arbitrary small, but P can exceed E, and P = 2.36E when T → T c .

Careful calculation of thermodynamical functions of tachyon gas

“…is always subluminal at all k F ≥ m. It may seem that the previous research of tachyon Fermi gas [10,12] is wrong because we have not taken into account the evident anomalous pressure (33). However, we need to check whether this concept is working at finite temperature.…”

“…The energy density, pressure, entropy and specific heat of tachyonic excitations [12] do remain right defined. The only correction concerns the particle number density, which is now…”

“…A system of many tachyons can be studied in the frames of statistical mechanics [6,7], and thermodynamical functions of ideal tachyon Fermi and Bose gases are calculated [8,9]. The properties of cold tachyon Fermi gas [10], its low-temperature behavior [11], tachyonic thermal excitations [12] and the hot tachyon gas [13] are also investigated.…”

Specific heat and entropy of tachyon Fermi gas

“…A system of many tachyons can be studied in the frames of statistical mechanics [1,2], and thermodynamical functions of ideal tachyon Fermi and Bose gases are calculated [3]. We have recently studied the equation of state (EOS) and acoustic properties of the cold tachyon Fermi [4] and Fermi gas of tachyonic thermal excitations [5].…”

Thermodynamics of absolute stiff matter

“…where w is dimensionless parameter that, in general, depends on E. Particularly, the EOS of ideal gas of non-relativistic particles has constant w = 2/3. The EOS with w = 1/3 describes radiation, the EOS of dust has w = 0, while tachyon matter admits P > E [1,2]. One of the most exotic examples…”