We study a holographic gauge theory living in the AdS$_4$ space-time at finite temperature. The gravity dual is obtained as a solution of the type IIB superstring theory with two free parameters, which correspond to four dimensional (4D) cosmological
constant ($lambda$) and the dark radiation ($C$) respectively. The theory studied here is in confining and chiral symmetry broken phase for $lambda <0$ and small $C$. When $C$ is increased, the transition to the deconfinement phase has been observed at a finite value of $C/|lambda|$. It is shown here that the chiral symmetry is still broken for a finite range of $C/|lambda|$ in the deconfinement phase. In other words, the chiral phase transition occurs at a larger value of $C/|lambda|$ than the one of the deconfinement transition. So there is a parameter range of a new deconfinement phase with broken chiral symmetry. In order to study the properties of this phase, we performed a holographic analysis for the meson mass-spectrum and other quantities in terms of the probe D7 brane. The results of this analysis are compared with a linear sigma model. Furthermore, the entanglement entropy is examined to search for a sign of the chiral phase trantion. Several comments are given for these analyses.
In this short paper, we argue the issue on dark matter capture in neutron stars. After summarizing the whole scenario and the introduction of previous studies along this line, we propose some potentially important effects due to the appearance of exo
tic phases such as neutron superfluidity, meson condensation and quark superconductivity. Those effects might be sizable and alter the previous results.
We have previously found a new phase of cold nuclear matter based on a holographic gauge theory, where baryons are introduced as instanton gas in the probe D8/$overline{rm D8}$ branes. In our model, we could obtain the equation of state (EOS) of our
nuclear matter by introducing fermi momentum. Then, here we apply this model to the neutron star and study its mass and radius by solving the Tolman-Oppenheimer-Volkoff (TOV) equations in terms of the EOS given here. We give some comments for our holographic model from a viewpoint of the other field theoretical approaches.
We study analytically the chiral phase transition for hot quark matter in presence of a strong magnetic background, focusing on the existence of a critical point at zero baryon chemical potential and nonzero magnetic field. We build up a Ginzburg-Lan
dau effective potential for the chiral condensate at finite temperature, computing the coefficients of the expansion within a chiral quark-meson model. Our conclusion is that the existence of the critical point at finite $bm B$ is very sensitive to the way the ultraviolet divergences of the model are treated. In particular, we find that after renormalization, no chiral critical point is present in the phase diagram. On the other hand, such a critical point there exists when the ultraviolet divergences are not removed by a proper renormalization of the thermodynamic potential.
We study cold nuclear matter based on the holographic gauge theory, where baryons are introduced as the instantons in the probe D8/D8 branes according to the Sakai-Sugimoto model. Within a dilute gas approximation of instantons, we search for the sta
ble states via the variational method and fix the instanton size. We find the first order phase transition from the vacuum to the nuclear matter phase as we increase the chemical potential. At the critical chemical potential, we could see a jump in the baryon density from zero to a finite definite value. While the size of the baryon in the nuclear matter is rather small compared to the nucleus near the transition point, where the charge density is also small, it increases with the baryon density. Those behaviors obtained here are discussed by relating them to the force between baryons.
