Hubbard physics in the symmetric half-filled periodic anderson-hubbard model

Two very different methods — exact diagonalization on finite chains and a variational method — are used to study the possibility of a metal-insulator transition in the symmetric half-filled periodic Anderson-Hubbard model. With this aim we calculate the density of doubly occupied d sites (gnd) as a function of various parameters. In the absence of on-site Coulomb interaction (Uf) between f electrons, the two methods yield similar results. The double occupancy of d levels remains always finite just as in the one-dimensional Hubbard model. Exact diagonalization on finite chains gives the same result for finite Uf, while the Gutzwiller method leads to a Brinkman-Rice transition at a critical value (Udc), which depends on Uf and V.