Itinerant and localized states in strongly correlated systems by a modified mean-field slave-boson approach

The standard mean field slave-boson solution for the infinite-U Hubbard mod el is revised. R slightly modified version is proposed which includes prope rly the incoherent contribution of the localized states. In contrast to the standard mean field result, this new proposed solution defines a unique sp ectral function to be used in the calculation of local and not local quanti ties, and satisfies the correct thermodynamic relations. The same approach is applied also to the mean field approximation in terms of Hubbard operato rs. iis a byproduct of this analysis, Luttinger's theorem is shown to be fu lfilled in a natural way.