Simulating the Langevin force by simple noise in nuclear one-body dynamics

For the purpose of addressing catastrophic phenomena in nuclear dynamics, we explore the possibility of simulating the stochastic part of the collision integral in the Boltzmann-Langevin model by the numerical noise associated with the finite number of test particles in the ordinary Boltzmann-Uehling-Uhlenbeck (BUU) treatment. Considering idealized two-dimensional matter, for which it is practical to simulate the Boltzmann-Langevin equation directly, we demonstrate that the number of test particles per nucleon can be adjusted so that the corresponding BUU calculation yields a good reproduction of the spontaneous clusterization occurring inside the spinodal region. This approximate method may therefore provide a relatively easy way to introduce meaningful fluctuations in simulations of unstable nuclear dynamics.