Remarks on the density functional approach to the inhomogeneous electron gas

The density functional approach is reformulated by using the most general form of the Hohenberg-Kohn theorem based on p-particle densities. Comparison with the reduced density matrix theory is made, exhibiting fully the p-particle hierarchy of both theories. Some advantages and drawbacks of the generalized density functional approach are discussed. The 1-particle spin-polarized case is presented to indicate the place of the usual DFA within the framework of the generalized theory.