Quantum Ergodicity and Localization in Conservative Systems: the Wigner   Band Random Matrix Model
  First theoretical and numerical results on the global structure of the energy shell, the Green function spectra and the eigenfunctions, both localized and ergodic, in a generic conservative quantum system are presented. In case of quantum localization the eigenfunctions are shown to be typically narrow and solid, with centers randomly scattered within the semicircle energy shell while the Green function spectral density (local spectral density of states) is extended over the whole shell, but sparse. 
G.Casati, B.V.Chirikov, I.Guarneri and F.M.Izrailev