  We present ab-initio calculations of the binding energy and radii of the
two-neutron halo nucleus 6He using two-body low-momentum interactions based on
chiral effective field theory potentials. Calculations are performed via a
hyperspherical harmonics expansion where the convergence is sped up introducing
an effective interaction for non-local potentials. The latter is essential to
reach a satisfactory convergence of the extended matter radius and of the
point-proton radius. The dependence of the results on the resolution scale is
studied. A correlation is found between the radii and the two-neutron
separation energy. The importance of three-nucleon forces is pointed out
comparing our results and previous calculations to experiment.
