One-body transport model of fluctuation processes in nuclear collisions

摘要

Many aspects of a many-body system can be described in terms of one- body transport models in which the system at any time is characterized by its single-particle density rather than by the full many-body information. In these one-body models evaluation of the single-particle density is determined by a transport equation which contains the self-consistent mean-field potential and a collision term due to binary two-body collisions. Recently, this approach in a semi-classical limit with a Boltzmann-Uehling-Uhlenbeck (BUU) form of a collision term has been applied to nuclear collisions at intermediate energies. Common to all one-body models, only the average effects of two-body collisions are retained in the equation of motion and higher order correlations are entirely neglected. This approximation corresponds to an ensemble averaging which is evident, for example, from the ''molecular chaos assumption'' introduced in derivation of Boltzmann equation. As a result, these one-body models determine the ensemble averaged single-particle density and cannot provide a description for the fluctuation processes in nuclear collisions. On the other hand, at low and intermediate energies dynamical fluctuations are substantial due to large available phase space for decay into many final states. Therefore, it is of great interest to improve one-body transport models by incorporating dynamical fluctuations due to high order correlations into the equation of motion. 5 refs., 3 figs.