  The performance of many-body perturbation theory for calculating ground-state
properties is investigated. We present fully numerical results for the electron
gas in three and two dimensions in the framework of the GW approximation. The
overall agreement with very accurate Monte Carlo data is excellent, even for
those ranges of densities for which the GW approach is often supposed to be
unsuitable. The latter seems to be due to the fulfilment of general
conservation rules. These results open further prospects for accurate
calculations of ground-state properties circumventing the limitations of
standard density functional theory.
