ar X iv : n uc l - th / 9 60 50 10 v 1 8 M ay 1 99 6 Hyperon - rich Matter Jürgen

The phase diagram of nuclear matter offers fascinating features for heavy ion physics and astrophysics when extended to strangeness and antimatter. We will discuss some regions of this phase diagram as strange matter at zero temperature, hypermatter at high densities and the antiworld at high densities and strangeness fraction. 1 Strange Matter and Hypermatter Relativistic heavy ion collisions provide a promising tool for studying the physics of strange quark and strange hadronic matter (see recent review [1]). Fig. 1 shows schematically the phase diagram of hot, dense and strange matter. Perhaps the only unambiguous way to detect the transient existence of a quark gluon plasma (QGP) might be the experimental observation of exotic remnants, like the formation of strange quark matter (SQM) droplets. First studies in the context of the MIT-bag model predicted that sufficiently heavy strangelets might be metastable or even absolutely stable. The reason for the possible stability of SQM is related to a third flavour degree of freedom, the strangeness. As the mass of the strange quark is smaller than the Fermi energy of the quarks, the total energy of the system is lowered by adding strange quarks. According to this picture, the number of strange