Dynamics of quantum equilibration, dissipation and fluctuation in nuclear collision

The equlibration processes are studied in collisions of atomic nuclei. We provide a general, systematic method to investigate the timescales of equilibration, dissipation, and fluctuation mechanisms through the use of a time-dependent, fully microscopic theory. Despite direct comparisons between wildly different systems spanning light and heavy nuclei at a range of collision energies, common timescales were found for each of the studied quantities. The longest process by far is mass equilibration, with a general equilibration time of $2\times 10^{-20}$s. Timescales for neutron-to-proton equilibration, mass fluctuation build up, kinetic energy dissipation, and angular momentum dissipation however are found to be on the order of $10^{-21}$s, an order of magnitude faster than that of mass equilibration. This vast separation implies the relative independence of dissipation mechanisms on mass equilibration, and that the primary generator of dissipative effects is fast nucleon exchange between interacting fragments. 1. C. Simenel, K. Godbey, and A. S. Umar, Phys. Rev. Lett. 124, 212504 (2020).