Three-nucleon interaction in nuclei, nuclear and neutron matter

Abstract

We review the effect of three-nucleon interactions on nuclei, nuclear and neutron matter, and neutron stars. There are three pairs and only one triplet in the three-nucleon system, while there are six pairs and four triplets in the four-nucleon system. Such general considerations suggest that three-nucleon interactions may have a relatively larger contribution in systems that have a large number of nucleons at high density. We review the results obtained with realistic two-nucleon interactions, and show that these underbind light nuclei, and give too large an equilibrium density for nuclear matter. A realistic model of the three-nucleon interaction, having an attractive two-pion exchange part and a repulsive shorter-ranged part is used. Its strengths are determined by fitting binding energies of light nuclei and empirical properties of nuclear matter. It is shown that the three-nucleon interaction makes the equation of state of nuclear and neutron matter stiff at high densities, and that this effect has measureable consequences in heavy-ion reactions and astrophysics.