Similarity Renormalization Group for Nucleon-Nucleon Interactions
  The similarity renormalization group (SRG) is based on unitary transformations that suppress off-diagonal matrix elements, forcing the hamiltonian towards a band-diagonal form. A simple SRG transformation applied to nucleon-nucleon interactions leads to greatly improved convergence properties while preserving observables, and provides a method to consistently evolve many-body potentials and other operators. 
S.K. Bogner, R.J. Furnstahl, R.J. Perry