Two Aspects of Color Superconductivity: Gauge Independence and Neutrality

It is well known that cold dense quark matter is a color superconductor. Color superconducting phases are characterized by a non-vanishing gap function, which can be calculated self-consistently from the SchwingerDyson equation (gap equation). At asymptotic densities, calculations from first principles (QCD) should be possible. However, calculations of the gap function seem to give different results for covariant and Coulomb gauge. This was the motivation to construct a formal proof of gauge independence, which is presented in Sec. 2. It turns out that this proof involves nonvanishing expectation values of the gauge fields. These expectation values act as effective chemical potentials for color and electric charge, which will be briefly discussed in Secs. 3-5.