Natural occupation numbers: when do they vanish?

@article{Giesbertz2013NaturalON,
  title={Natural occupation numbers: when do they vanish?},
  author={Klaas J. H. Giesbertz and Robert van Leeuwen},
  journal={The Journal of chemical physics},
  year={2013},
  volume={139 10},
  pages={
          104109
        }
}
The non-vanishing of the natural orbital (NO) occupation numbers of the one-particle density matrix of many-body systems has important consequences for the existence of a density matrix-potential mapping for nonlocal potentials in reduced density matrix functional theory and for the validity of the extended Koopmans' theorem. On the basis of Weyl's theorem we give a connection between the differentiability properties of the ground state wavefunction and the rate at which the natural occupations… 

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