Repulsive vector interaction as a trigger for the non-conformal peak in $V_s^2$

Abstract

Considering the NJL model with a repulsive vector channel, parametrized by GV , I show that one may generate a non-monotonic behavior for the speed of sound which peaks at V 2 s > 1/3. This can be achieved by assuming GV to be density dependent so that the resulting EoS is stiff/repulsive at low densities and soft/non-repulsive at high densities. The interpolation between the two regimes happens through a cross-over which takes place after the first order chiral transition sets in. The model explicitly shows that a non-conformal peak in V 2 s is not in tension with the QCD trace anomaly being positive at all densities, supporting recent claims in this direction. A brief discussion on how the running coupling may affect the mass-radius relation is carried out in the context of simple non-strange quark stars.

Temperature and strong magnetic field effects in dense matter

“…Figure 8 shows the different magneticfield profiles as a function of baryon chemical potential, In order not to repeat all our EOS results here with the magnetic-field profiles, we show instead the EOS derivatives, namely the speed of sound squared c 2 s ¼ dP=dϵ. This quantity has been shown to be directly relevant for astrophysical discussions of, for instance, stellar masses, radii, and tidal deformability [88][89][90][91][92][93], and the outcome of binary neutron-star mergers [94][95][96]. Besides, it has been suggested that this quantity may give some information about a possible deconfinement phase transition [89].…”