Metal-insulator transition in the Hubbard model by the irreducible Green functions method

Abstract
The irreducible Green functions method is developed to obtain an interpolational Green function for the Hubbard model that is appropriate both in the band limit and in the atomic limit. The metal-insulator transition occurs due to the collapse of the electron and hole Fermi surfaces and it is a very smooth transition of the 2.5 kind. The quasiparticle damping is zero on the Fermi surface in the metallic phase.