The strange quark-gluon plasma

Strangeness flavor has turned out be a very effective diagnostic tool of relativistic heavy ion physics. The absolute yield provides information about conditions arising in first instants of the interaction. Strange hadrons are abundant allowing a precise study of the chemical freeze-out conditions in the dense matter fireball. The thermal and chemical freeze-out universality seen in strange hadrons confirms sudden hadronization as the breakup mechanism. A plausible cause of sudden fireball breakup is the mechanical instability arising when a quark-gluon plasma phase supercools deeply in its adiabatic expansion. Applying these ideas, we interpret CERN-SPS and the first results on hadronic particle ratios obtained at RHIC. (author)