2004/06/30 by Mark Alford, Chris Kouvaris, Krishna Rajagopal · 5 citations
Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #Condensed matter physics #Gapless playback #High-Energy Particle Collisions Research #Particle physics #Phase (matter) #Physics #Quantum Chromodynamics and Particle Interactions #Quantum mechanics #Quark #Quasiparticle #Strange matter #Strange quark #Superconductivity #hep-ph #nucl-th
paper · pdf · doi:10.1103/physrevd.71.054009
published as Phys.Rev.D71:054009,2005 · 18 pages, RevTeX; Version to appear in Phys Rev D. Minor rewording, references added
arxiv created 2004/08/02 · openalex publication_date 2005/03/04 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
In neutral cold quark matter that is sufficiently dense that the strange quark mass Ms is unimportant, all nine quarks (three colors; three flavors) pair in a color-flavor locked (CFL) pattern, and all fermionic quasiparticles have a gap. We recently argued that the next phase down in density (as a function of decreasing quark chemical potential \ensuremathμ or increasing strange quark mass Ms) is the new ``gapless CFL'' (gCFL) phase in which only seven quasiparticles have a gap, while there are gapless quasiparticles described by two dispersion relations at three momenta. There is a continuous quantum phase transition from CFL to gCFL quark matter at Ms2/\ensuremathμ\ensuremath≈2\ensuremathΔ, with \ensuremathΔ the gap parameter. Gapless CFL, like CFL, leaves unbroken a linear combination \stackrel\texttildelowQ of electric and color charges, but it is a \stackrel\texttildelowQ conductor with gapless \stackrel\texttildelowQ-charged quasiparticles and a nonzero electron density. In this paper, we evaluate the gapless CFL phase, in several senses. We present the details underlying our earlier work which showed how this phase arises. We display all nine quasiparticle dispersion relations in full detail. Using a general pairing ansatz that only neglects effects that are known to be small, we perform a comparison of the free energies of the gCFL, CFL, two-flavor (2SC), gapless 2SC, and two-flavor up-strange phases. We conclude that as density drops, making the CFL phase less favored, the gCFL phase is the next spatially uniform quark matter phase to occur. A mixed phase made of colored components would have lower free energy if color were a global symmetry, but in QCD such a mixed phase is penalized severely.