Diquark Condensation in Electrically and Color Neutral Quark Matter

We discuss the possible phase structure of strongly interacting matter in the regime of high densities and low temperatures where the quarks are expected to be in a color superconducting state. We focus on the additional constraints imposed by the requirement of electric and color neutrality which is essential for the description of neutron star interiors. To that end we employ a 3‐flavor NJL‐type quark model, which treats the diquark condensates and the quark‐antiquark condensates on an equal footing. The resulting phase diagram at zero temperature and the various independent chemical potentials turns out to be very rich, containing at least five different color superconducting phases. We search for regions of electrically and color neutral matter and also discuss the possibility of mixed phases with zero net charge. Neglecting surface and Coulomb effects we find nine different mixed phases with up to four components. Preliminary estimates indicate, however, that the mixed phases become unstable if surface and Coulomb effects are included.