Linear response functions of a quasi-one-dimensional electron gas

The predictions for density-density-type response functions of a quasi-one dimensional electron gas are compared in detail for various models (Hubbard and Tomonaga model) and for various approximations (Monte-Carlo calculations, RPA and extended RPA). It is shown that RPA does not lead to intrinsic contradictions for electron densities larger than 1.5 inverse exciton Bohr radii. Even in this high-density regime local field corrections enhance spin- and density susceptibilities significantly.