2-BODY CORRELATIONS IN PIONIC SYSTEMS

In close analogy to fermionic many-body theory the truncation of the b osonic BBGKY density matrix hierarchy on the two-body level leads to a coupled set of nonlinear equations of motion for the one-body density matrix and the two-body correlation function. These equations provide a nonperturbative description of the nonequilibrium time evolution of particle-number conserving bosonic many-body systems including the dy namical resummation of parquet-like diagrams. Within this framework we study the properties of a pionic system as a function of temperature and density with focus on two-body quantities. For each temperature we find a related pion density for which the relative strength of the tw o-body correlation function assumes a maximum and the pionic system is far from the mean-field limit. However, these correlated phases up to T = 200 MeV only appear at pion densities which are very low compared to those expected in central nucleus-nucleus collisions at SPS or RHI C energies.