The state of cold quark matter really challenges both astrophysicists and
particle physicists, even many-body physicists. It is conventionally suggested
that BCS-like color superconductivity occurs in cold quark matter; however,
other scenarios with a ground state rather than of Fermi gas could still be
possible. It is addressed that quarks are dressed and clustering in cold quark
matter at realistic baryon densities of compact stars, since a weakly coupling
treatment of the interaction between constituent quarks would not be reliable.
Cold quark matter is conjectured to be in a solid state if thermal kinematic
energy is much lower than the interaction energy of quark clusters, and such a
state could be relevant to different manifestations of pulsar-like compact
stars.Comment: Proceedings of IWARA2009 (IJMP D
