Virtual Journal on QCD Matter

Collisions of heavy nuclei at RHIC (and soon LHC) energies create a state of matter similar to that of the early universe a few microseconds after the big bang, characterized by a temperature of T ~200-400 MeV. Temperature is one useful intensive thermodynamical variable for depicting the phase diagram of nuclear matter. Another is the net baryon density ρ_B (or alternatively, the baryon chemical potential μ_B), reflecting the fact that baryon number is a conserved quantity. The central region of a collision at RHIC is nearly (net!) baryon free, with a value of μ_B/T ~10% << 1, and therefore crudely approximates the early universe, where this ratio was of order 10^-9.

As exciting as it is to explore the early universe in the laboratory, very relativistic nuclear collisions access only a ‘small’ region of the phase diagram near μ_B =0. There is also enormous astrophysical relevance along the μ_B axis very near T=0. This is the domain that describes nuclear matter as found in neutron stars. (more…)

Comments(0)

One of the key motivations often cited for QGP research is its astrophysical connection, namely that the early universe was in a QGP state shortly after its creation in the Big Bang. (more…)

Comments(0)