Unlocking color and flavor in superconducting strange quark matter

We explore the phase diagram of strongly interacting matter with massless u and d quarks as a function of the strange quark mass m(s) and the chemical potential mu for baryon number. Neglecting electromagnetism, we describe t he different baryonic and quark matter phases at zero temperature. For quar k matter, we support our model-independent arguments with a quantitative an alysis of a model which uses a four-fermion interaction abstracted from sin gle-gluon exchange. For any finite m(s), at sufficiently large mu we find q uark matter in a color-flavor-locked state which leaves a global vector-lik e SU(2)(color+L+R) symmetry unbroken. As a consequence, chiral symmetry is always broken in sufficiently dense quark matter. As the density is reduced , for sufficiently large m(s) we observe a first-order transition from the color-flavor-locked phase to color superconducting phase analogous to that in two-flavor QCD. At this unlocking transition chiral symmetry is restored . For realistic values of m(s) our analysis indicates that chiral symmetry breaking may be present for all densities down to those characteristic of b aryonic matter. This supports the idea that quark matter and baryonic matte r may be continuously connected in nature. We map the gaps at the quark Fer mi surfaces in the high density color-flavor-locked phase onto gaps at the baryon Fermi surfaces at low densities. (C) 1999 Published by Elsevier Scie nce B.V. All rights reserved.