0 60 90 03 v 1 1 S ep 2 00 6 Low - momentum interactions with smooth cutoffs

Nucleon-nucleon potentials evolved to low momentum, which show great promise in fewand many-body calculations, have generally been formulated with a sharp cutoff on relative momenta. However, a sharp cutoff has technical disadvantages and can cause convergence problems at the 10–100 keV level in the deuteron and triton. This motivates using smooth momentum-space regulators as an alternative. We generate low-momentum interactions with smooth cutoffs both through energy-independent renormalization group methods and using a multi-step process based on the BlochHorowitz approach. We find greatly improved convergence for calculations of the deuteron and triton binding energies in a harmonic oscillator basis compared to results with a sharp cutoff. Even a slight evolution of chiral effective field theory interactions to lower momenta is beneficial. The renormalization group preserves the long-range part of the interaction, and consequently the renormalization of longrange operators, such as the quadrupole moment, the radius and 〈1/r〉, is small. This demonstrates that low-energy observables in the deuteron are reproduced without short-range correlations in the wave function.