Neutron Stars, Supernova Explosions and the Transition to Quark Matter

The transition to quark matter can take place in neutron stars. The structure of a hybrid star, containing a core made of quark matter is discussed. The maximum mass of the non-rotating hybrid star turns out to be 1.6 M_s. Possible signatures of the quark phase as pulsar's timing, cooling rate etc. are briefly analyzed. The deconfinement transition can also take place during the pre-supernova collapse. This possibility is studied by introducing a finite temperature EOS. The dependence of the latter on the proton fraction is shown to be crucial. The softening of the EOS at densities just above nuclear matter saturation density for Z/A = 0.3 helps in obtaining an explosion. At the same time, at larger densities the EOS is stiff enough to support a neutron star compatible with observations.