Relativistic vs. Non-relativistic Nuclear Models
  Both the relativistic and non-relativistic model explain very well low-energy nuclear phenomena, but in a physically different way from each other. There seems to be no low-energy phenomenon to answer which model is more reasonable. In order to explore a difference between two models, high momentum transfer phenomena are investigated. First it is shown that the neutron spin-orbit charge density in the relativistic model reproduces very well experimental data on elastic electron scattering which have not been explained in the non-relativistic model. Next it is predicted that the relativistic Coulomb sum value is strongly quenched, compared with the non-relativistic one. This quenching is owing to the anti-nucleon degrees of freedom, which make the nucleon size larger and equivalently the vector-meson mass smaller in nuclear medium. New experiment on the Coulomb sum values around the momentum transfer 1GeV is expected to distinguish the relativistic from the non-relativistic model. 
H. Kurasawa (Chiba Univ.) and T. Suzuki (Fukui Univ.)