σ Exchange in the NN Interaction within the Chiral Unitary Approach
We study the nucleon-nucleon interaction in the isoscalar-scalar channel using the chiral unitary approach. The t-matrix of the pion-pion scattering in this channel is summed up to all orders using the B-S equation. We find that the calculated results at long distances are close to those of the �-exchange interaction. In addition, there appears a shorter range repulsion in this channel.