Neutron-proton effective mass splitting in neutron-rich matter and its impacts on nuclear reactions

Understand

The neutron-proton effective mass splitting in neutron-rich nucleonic matter reflects the space-time nonlocality of the isovector nuclear interaction.

• It affects the neutron/proton ratio during the earlier evolution of the Universe, cooling of protoneutron stars, structure of rare isotopes and dynamics of heavy-ion collisions.
• While there is still no consensus on whether the neutron-proton effective mass splitting is negative, zero or positive and how it depends on the density as well as the isospin-asymmetry of the medium, significant progress has been made in recent yeas in addressing these issues.
• We first recall the connections among the neutron-proton effective mass splitting, the momentum dependence of the isovector potential and the density dependence of the symmetry energy.