NNLO corrections to nucleon-nucleon scattering and perturbative pions

We apply the effective field theory approach to the three-nucleon system. In particular, we consider S = 1 /2 neutron-deuteron scattering and the triton. We show that in this channel a unique nonperturbative renormalization takes place which requires the introduction of a single three-body force at leading order. With one fitted parameter we find a good description of low-energy data. Invariance under the renormalization group explains some universal features of the three-nucleon system - such as the Thomas and Efimov effects and the Phillips line - and the origin of SU(4) symmetry in nuclei.