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We study the gluonic phase in a two-flavor color superconductor as a function of the ratio of the gap over the chemical potential mismatch, Δ/δμ. We find that the gluonic phase resolves the chromomagnetic instability encountered in a two-flavor color superconductor for Δ/δμ<2. We also calculate approximately the free energies of the gluonic phase and the single plane-wave LOFF phase and show that the former is favored over the latter for a wide range of coupling strengths.
We explore the formation of diquark bound states and their Bose–Einstein condensation (BEC) in the phase diagram of three-flavor quark matter at nonzero temperature, T, and quark chemical potential, μ. Using a quark model with a four-fermion interaction, we identify diquark excitations as poles of the microscopically computed diquark propagator. The quark masses are obtained by solving a dynamical equation for the chiral condensate and are found to determine the stability of the diquark excitations. The stability of diquark excitations is investigated in the T–μ plane for different values of the diquark coupling strength. We find that diquark bound states appear at small quark chemical potentials and at intermediate coupling strengths. Bose–Einstein condensation of non-strange diquark states occurs when the attractive interaction between quarks is sufficiently strong.
We perform a study of the possible existence of hybrid stars with color superconducting quark cores using a specific hadronic model in a combination with an NJL-type quark model. It is shown that the constituent mass of the non-strange quarks in vacuum is a very important parameter that controls the beginning of the hadron–quark phase transition. At relatively small values of the mass, the first quark phase that appears is the two-flavor color superconducting (2SC) phase which, at larger densities, is replaced by the color-flavor locked (CFL) phase. At large values of the mass, on the other hand, the phase transition goes from the hadronic phase directly into the CFL phase avoiding the 2SC phase. It appears, however, that the only stable hybrid stars obtained are those with the 2SC quark cores.
We compute neutrino emissivities, specific heat, and the resulting cooling rates in four spin-one color superconductors: color-spin locked, planar, polar, and A phases. In particular, the role of anisotropies and point nodes in the quasiparticle excitation spectra are investigated. Furthermore, it is shown that the A phase exhibits a helicity order, giving rise to a reflection asymmetry in the neutrino emissivity.