  A forefront area of research concerns the exploration of the properties of
hadronic matter under extreme conditions of temperature and density, and the
determination of the equation of state--the relation between pressure,
temperature and density--of such matter. Experimentally, relativistic heavy-ion
collision experiments enable physicists to cast a brief glance at hot and
ultra-dense matter for times as little as about $10^{-22}$ seconds.
Complementary to this, the matter that exists in the cores of neutron stars,
observed as radio pulsars, X-ray pulsars, and magnetars, is at low temperatures
but compressed permanently to ultra-high densities that may be more than an
order of magnitude higher than the density of atomic nuclei. This makes pulsars
superb astrophysical laboratories for medium and high-energy nuclear physics,
as discussed in this paper.
