Energy Dependent Isospin Asymmetry in Mean-Field Dynamics
  The Lagrangian density of relativistic mean-field (RMF) theory with non-linear derivative (NLD) interactions is applied to isospin asymmetric nuclear matter. We study the symmetry energy and the density and energy dependences of nucleon selfenergies. At high baryon densities a soft symmetry energy is obtained. The energy dependence of the isovector selfenergy suppresses the Lane-type optical potential with increasing energy and predicts a $\rho$-meson induced mass splitting between protons and neutrons in isospin asymmetric matter. 
T. Gaitanos, M. Kaskulov
nucl-th