Low-momentum interaction in few-nucleon systems

The low-momentum nucleon-nucleon interaction Vlowk is applied to three- and four-nucleon systems. We investigate the 3H, 3He, and 4He binding energies for a wide range of the momentum cutoffs. By construction, all low-energy two-body observables are cutoff independent, and therefore, any cutoff dependence is due to missing three-body or higher-body forces. We argue that for reasonable cutoffs Vlowk is similar to high-order interactions derived from chiral effective field theory. This motivates augmenting Vlowk by corresponding three-nucleon forces. The set of low-momentum two- and three-nucleon forces can be used in calculations of nuclear structure and reactions. We find that three-nucleon force contributions are perturbative for small cutoffs