Hubbard approximation for the dielectric response function of a confined inhomogeneous electron gas

The most significant features of a confined electron gas in, e.g., a quantu m well are (i) the inhomogeneous charge distribution and (ii) the multiband nature of the spectrum of quasi 2D electron states. Both facts are here ta ken into account in the dielectric response of a confined electron gas, for which a Hubbard approximation is obtained which is the multiband extension of the standard result for the 3D case and reflects both the dynamics and the multiband nature of the spectrum of a confined quasi 2D electron gas.