Gapless color superconductivity at zero and at finite temperature

We present a detailed study of the recently proposed gapless color superconductivity in neutral two-flavor quark matter in β-equilibrium at zero as well as at finite temperature. We clarify the nature of the fermionic quasiparticles, and discuss the physical properties of this gapless phase of quark matter. The appearance of two "secondary" spin-1 condensates in the gapless ground state is pointed out. The gluon screening properties are also discussed. It is found that finite temperature properties of the gapless color superconductor are rather unusual. One of the most striking results is that the ratio of the critical temperature to the gap at zero temperature is not a universal number. Moreover, this ratio could become arbitrarily large at some values of the coupling constant. In addition, the value of the gap parameter is not a monotonic function of temperature, although the phase transition is a second order phase transition. In an extreme case, in fact, a nonzero finite temperature gap can appear even if its zero temperature value is vanishing.