Article,
Color superconductivity in dense quark matter
Reviews of Modern Physics, 80 (4): 1455--1515 (Jan 21, 2008)
DOI: 10.1103/revmodphys.80.1455
Abstract
Matter at high density and low temperature is expected to be a color
superconductor, which is a degenerate Fermi gas of quarks with a condensate of
Cooper pairs near the Fermi surface that induces color Meissner effects. At the
highest densities, where the QCD coupling is weak, rigorous calculations are
possible, and the ground state is a particularly symmetric state, the
color-flavor locked (CFL) phase. The CFL phase is a superfluid, an
electromagnetic insulator, and breaks chiral symmetry. The effective theory of
the low-energy excitations in the CFL phase is known and can be used, even at
more moderate densities, to describe its physical properties. At lower
densities the CFL phase may be disfavored by stresses that seek to separate the
Fermi surfaces of the different flavors, and comparison with the competing
alternative phases, which may break translation and/or rotation invariance, is
done using phenomenological models. We review the calculations that underlie
these results, and then discuss transport properties of several
color-superconducting phases and their consequences for signatures of color
superconductivity in neutron stars.
