Anisotropic equation of state of charged and neutral vector boson gases in a constant magnetic field. Astrophysical implications

Abstract

We obtain the pressures and equations of state (EoS) of charged and neutral vector boson gases in a constant magnetic field. The axial symmetry imposed to the system by the field splits the pressures in the parallel and perpendicular directions along the magnetic axis, and this leads to anisotropic equations of state. The values of pressures and energy densities are in the order of those of Fermi gases in compact objects. This opens the possibility to the existence of magnetized boson stars. Under certain conditions, the perpendicular pressure might be negative imposing a bound to the stability of the star. Other implications of negative pressures are also discussed.

Paramagnetic squeezing of a uniformly expanding quark-gluon plasma in and out of equilibrium

“…Whereas the second term on the lhs of (IV.32) vanishes because of the same argument as in (III. 16), the first term on the lhs of (IV.32) leads to…”

“…Assuming the magnetic field to be aligned in a fixed direction, an anisotropy is naturally induced in any magnetized medium including charged fermions. This kind of anisotropy is previously studied, e.g., in [11][12][13][14][15][16][17][18][19]. One of the consequences of this anisotropy is the difference between the longitudinal and transverse pressures with respect to the fixed direction of the magnetic field.…”

“…7 and 8 shows that the transverse speed of sound is in general smaller than the longitudinal speed of sound. Replacing, at this stage, the proper time τ arising in the corresponding expressions to c s0,i and c s,i , i =⊥, , with τ = τ T /T 3 from (II.29) with the initial time τ = 0.2 fm/c and the initial temperature T = 400 MeV, 16 we arrive at the T dependence of c s0,i and c s,i , i =⊥, . This is demonstrated in Fig.…”

“…This difference turns out to be proportional to the magnetization of the medium, and leads, in particular, to an anisotropic equation of state (EoS) for the magnetized QCD matter. The latter is studied, e.g., in [13][14][15][16] in different contexts. In [17], the EoS of the magnetized QCD is determined in the hadron resonance gas model.…”