Delta-Delta intermediate states in nucleon-nucleon scattering from a large-N_c perspective

The large-N_c picture, where N_c is the number of colors, successfully explains some features of the nucleon-nucleon (NN) interactions. This success is somewhat surprising. In the large-N_c limit, the nucleon and the Delta isobar become degenerate, and the Delta plays an important role for the consistency of the large-N_c approach in the single-baryon sector. However, large-N_c analyses of NN interactions so far have not taken into account intermediate Delta-Delta states. We analyze the impact of including Delta intermediate states in NN scattering and provide a possible explanation for the success of “Delta-less” large-N_c approaches.