Self-Consistent Random Phase Approximation - Application to the Hubbard   Model for finite number of sites
  Within the 1D Hubbard model linear closed chains with various numbers of sites are considered in Self Consistent Random Phase Approximation (SCRPA). Excellent results with a minimal numerical effort are obtained for 2+4n sites cases, confirming earlier results with this theory for other models. However, the 4n sites cases need further considerations. SCRPA solves the two sites problem exactly. It therefore contains the two electrons and high density Fermi gas limits correctly. 
Mohsen Jemai, Peter Schuck, Jorge Dukelsky, Raouf Bennaceur