Nuclear Force from String Theory

We compute nuclear force in a holographic model of QCD on the basis of a D4-D8 brane configuration in type IIA string theory. Repulsive core of nucleons is quite important in nuclear physics, but its origin has not been well-understood in strongly-coupled QCD. We find that string theory via gauge/string duality deduces this repulsive core at short distance between nucleons. Since baryons in the model are realized as solitons given by Yang-Mills instanton configuration on flavor D8-branes, ADHM construction of two instantons probes well the nucleon interaction at short scale, which provides the nuclear force quantitatively. We obtain, as well as a tensor force, a central force which is strongly repulsive as suggested in experiments and lattice results. In particular, the nucleon-nucleon potential V (r) (as a function of the distance) scales as r−2, which is peculiar to the holographic model. We compare our results with one-boson exchange model using the nucleon-nucleon-meson coupling obtained in our previous paper [6].