  We review the role played by long-distance symmetries within the context of
the similarity renormalization group approach. This is based on
phase-shift-preserving continuous unitary transformations that evolve
Hamiltonians with a cutoff on energy differences. We find that there is a
similarity cutoff of 3/fm for which almost perfect fulfillment of Wigner SU(4)
symmetry is found at the two body level. This suggests to look for similar
symmetry patterns for three- and four-body forces. We also analyze the impact
of potentials based on Chiral Perturbation Theory in Nuclear Structure
calculations.
