  Nucleon self-energies for 40Ca, 48Ca, 60Ca 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 40Ca and
48Ca. The \textit{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 non-locality 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 FPRA self-energies are explored. The
global features of the FRPA self-energies are not strongly dependent on the
choice of realistic nucleon-nucleon interaction.
