The Metal-Insulator Transition in the Hubbard Model at Zero Temperature   II
  We study the metal-to-insulator transition of the Hubbard model at zero temperatures in infinite dimensions. The coexistence of metallic and insulating solutions for a finite range of the interaction is established. It is shown that the metallic solution is lower in energy for any interaction in the coexistence region and that the transition is of second order. 
Marcelo J. Rozenberg, Goetz Moeller, Gabriel Kotliar