The Color-Superconducting {'}t Hooft Interaction

We consider the effect of a six-fermion interaction of the {'}t Hooft form in the quark-quark channel on the ground state of matter at finite density. The coupling constant for this new term is varied within the limits suggested by naturalness. The flavor-mixing effects of the additional term destabilize the color-flavor-locked (CFL) and, to a lesser extent, the two-color superconducting (2SC) phases of quark matter, especially for positive values of the coupling. For some values of the coupling, the critical density for the CFL phase is nearly larger than the maximum density in the neutron stars. We comment on the implications for neutron star evolution.