7.14 \times 10^{34}cm^{-3}$. $N_c$ bounds the values of particle densities for which self-magnetization is possible. The maximum field that could be self sustained by the gas corresponds to the critical density and has a magnitude of $2/3\times B_c$. The values of $B$ and $N$ for which a self-magnetization may occur are in the order of those typical of compact objects. The maximum field that can be self maintined by the NVBG is the same obtained for a gas of charged vector bosons with the same mass and magnetic moment, but in this case the critical particle density is of the order of $10^{32}cm^{-3}$ [@Elizabeth].

Anisotropic Pressures
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We will consider the energy momentum tensor and the anisotropic pressures of the system. The total energy momentum tensor of matter plus vacuum will be obtained as a diagonal tensor whose spatial part contains the pressures and the time component is the internal energy density $E$. One gets from the thermodynamical potential $$\label{emtensor}
T^i_j=\frac{\partial\Omega}{\partial a_{i,\lambda}}a_{j,\lambda}-\Omega\delta_{j}^i,\quad\quad T_4^4=-E,$$

where $a_{i}$ denotes the boson or fermion fields [@PerezRojas:2006dq]. For a thermodynamical potential that depends on an external field, Eq.(\[emtensor\]) leads to pressure terms of form

$$\textit{T}^i_j=-\Omega-F_k^i\left( \frac{\partial\Omega}{\partial F_k^j}\right),\quad  i=j.$$

Computing the pressures along each direction makes 