Cold nuclear matter at high densities

Abstract

Consideration of matter at high densities shows that nuclear or neutron matter does not merge to quark matter at densities achieved in the collapse of large stars or in neutron stars. Since the quark/gluon core of the nucleon is only ~ 0.5 fm in radius, boson-exchange models are adequate for the discussion of the equation of state up to ϱ ~ 8 ϱ nm, where ϱ nm is nuclear-matter density. Manufacturing equations of state for nuclear and neutron matter requires not only treatment of two-body interactions, but also relativistic corrections and three-body interactions. In going to high densities, it is essential to include higher-order loop corrections. For “successful” supernovae in which neutron stars are formed, the nuclear equation of state must be quite soft in the region ϱ ~ 1–3 ϱ nm. The merging of nucleons into quarks at densities ϱ ~ 8 ϱ nm seems to be accomplished by the chiral bags in the nucleon extending throughout the volume, “squeezing out” the meson cloud. This transition should be a very smooth one.