Quark description of the Nambu-Goldstone bosons in the color-flavor locked phase

Abstract

We investigate the color-singlet order parameters and the quark description of the Nambu-Goldstone (NG) bosons in the color-flavor locked (CFL) phase. We put emphasis on the NG boson (phason) called $H$ associated with the ${\mathrm{U}}_{\mathrm{B}}(1)$ symmetry breaking. We qualitatively argue the nature of $H$ as the second sound in the hydrodynamic regime. We articulate, based on a diquark picture, how the structural change of the condensates and the associated NG bosons occurs continuously from hadronic to CFL quark matter if the quark-hadron continuity is realized. We sharpen the qualitative difference between the flavor octet pions and the singlet phason. We propose a conjecture that superfluid $H$ matter undergoes a crossover to a superconductor with tightly bound diquarks, and then a crossover to superconducting matter with diquarks dissociated.