Masses of the Goldstone modes in the CFL phase of QCD at finite density
  We construct the U_L(3) x U_R(3) effective lagrangian which encodes the dynamics of the low energy pseudoscalar excitations in the Color-Flavor-Locking superconducting phase of QCD at finite quark density. We include the effects of instanton-induced interactions and study the mass pattern of the pseudoscalar mesons. A tentative comparison with the analytical estimate for the gap suggests that some of these low energy momentum modes are not stable for moderate values of the quark chemical potential. 
Cristina Manuel and Michel H. G. Tytgat