Spin-orbit field and extrapolated properties of exotic nuclei

Using the extended Thomas-Fermi plus Strutinsky integral approximation to the Skyrme-Hartree-Fock method we show that provided the nuclear mass data are well fitted extrapolations to neutron-rich and super-heavy nuclei are quite insensitive to generalizations intended to simulate the main effects of relativistic mean-field theory. In particular, as far as energy-related quantities are concerned, it is sufficient to use the conventional spin-orbit force.