Microscopic self-energy calculations and dispersive optical-model potentials

Nucleon self-energies for {sup 40,48,60}Ca isotopes are generated with the microscopic Faddeev-random-phase approximation (FRPA). These self-energies are compared with potentials from the dispersive optical model (DOM) that were obtained from fitting elastic-scattering and bound-state data for {sup 40,48}Ca. The ab initio FRPA is capable of explaining many features of the empirical DOM potentials including their nucleon asymmetry dependence. The comparison furthermore provides several suggestions to improve the functional form of the DOM potentials, including among others the exploration of parity and angular momentum dependence. The nonlocality of the FRPA imaginary self-energy, illustrated by a substantial orbital angular momentum dependence, suggests that future DOM fits should consider this feature explicitly. The roles of the nucleon-nucleon tensor force and charge-exchange component in generating the asymmetry dependence of the FRPA self-energies are explored. The global features of the FRPA self-energies are not strongly dependent on the choice of realistic nucleon-nucleon interactions.