Timescales of quantum equilibration, dissipation and fluctuation in nuclear collisions

Understanding the dynamics of equilibration processes in quantum systems as well as their interplay with dissipation and fluctuation is a major challenge in quantum many-body theory. The timescales of such processes are investigated in collisions of atomic nuclei using fully microscopic approaches. Results from time-dependent Hartree-Fock (TDHF) and time-dependent random-phase approximation (TDRPA) calculations are compared for 13 systems over a broad range of energies. The timescale for full mass equilibration ($\sim 2\times {10}^{-20}$s) is found to be much larger than timescales for neutron-to-proton equilibration, kinetic energy and angular momentum dissipations which are on the order of ${10}^{-21}$s. Fluctuations of mass numbers in the fragments and correlations between their neutron and proton numbers build up within only a few ${10}^{-21}$s. This indicates that dissipation is basically not impacted by mass equilibration, but is mostly driven by the exchange of nucleons between the fragments.