Antisymmetrized molecular dynamics of wave packets with stochastic incorporation of the Vlasov equation

Abstract

On the basis of the antisymmetrized molecular dynamics (AMD) of wave packets for the quantum system, a novel model (called AMD-V) is constructed by the stochastic incorporation of the diffusion and the deformation of wave packets which is calculated by Vlasov equation without any restriction on the one-body distribution. In other words, the stochastic branching process in molecular dynamics is formulated so that the instantaneous time evolution of the averaged one-body distribution is essentially equivalent to the solution of Vlasov equation. Furthermore, as usual molecular dynamics, AMD-V keeps the many-body correlation and can naturally describe the fluctuation among many channels of the reaction. It is demonstrated that the newly introduced process of AMD-V has drastic effects in heavy ion collisions of 40 Ca + 40 Ca at 35 MeV/nucleon, especially on the fragmentation mechanism, and AMD-V reproduces the fragmentation data very well. Discussions are given on the interrelation among the frameworks of AMD, AMD-V and other microscopic models developed for the nuclear dynamics.

Nuclear stopping and light charged particle emission in C12+C12 at 95 MeV/nucleon

“…Fermi boost taken into account in the two-body collision process as described in the next section originates from the same nucleon-nucleon interaction, but in AMD in Ref. [27] the diffusion process and the two-body collision process are treated as independent processes. Therefore we need to take into account the quantum fluctuation as the Fermi boost in both processes.…”

“…For more details about the quantum branching, we refer to Refs. [27,28]. The physical origin of the quantum branching is to take into account the quantum fluctuation in phase space as seen in the above formulation.…”

“…The time evolution in AMD described in Refs. [27,28] is determined by two factors, the mean-field propagation and the decomposition into branches (quantum branching). The latter is treated numerically as follows.…”

“…AMD results, such as multiplicity, angular distributions and energy spectra, have often been compared with those from the experimental data in intermediate energy heavy ion collisions and reproduce them reasonably well [20,[27][28][29][31][32][33][34].…”

“…In order to further elucidate the production mechanism of LCPs at intermediate heavy ion collisions, we apply AMD [27][28][29], AMD-FM [26] and constrained molecular dynamics (CoMD) [30] to compare to the experimental angular distributions and energy spectra in the 12 C + 12 C reactions at 95 MeV/nucleon. The detailed comparisons reveal that the differences among these models in describing the production mechanism of charged light particles appear in these observables and enable us to constrain the models and their ingredients.…”