Neutron stars in the large-Nc limit

We study the phase transition from dense baryonic matter to dense quark matter within the large-Nc limit. By using simple constant speed of sound equations of state for the two phases, we derive the scaling with Nc of the critical quark chemical potential mu_crit for this phase transition. While quark matter is strongly suppressed at large Nc, the phase transition at a large but finite density could nevertheless be important to determine the maximum mass of compact stars. In particular, in the range 3<Nc<5.5 the quark phase would take place in compact stars and would lead to the formation of an unstable branch of hybrid stars. As a consequence, the maximum mass is restricted to the range 2.1M_sun<Mmax