ABSTRACT
About one-millionth of a second after the big bang, the temperature of the cosmos cooled sufficiently to allow the quarks to cross the so-called quark—hadron phase transition and combine into the familiar nuclear particles. Very recently, it has been demonstrated that this transition may be taking place in reverse in today’s Universe – but this time inside pulsars. A first-order phase transition actually may give rise to two shocks which quickly coalesce. More importantly, it was shown that there may be significant differences in the evolution of cores with or without first-or second-order quark—hadron phase transitions which may eventually lead to observational signatures in the neutrino signal. Another issue concerns the formation of black holes from collapsing neutron stars, which is likely to be delayed if quarks are present. The chapter presents a representative model for the equation of state of hybrid-star matter.
