Abstract
We consider the combined influence of disorder, electron4ectron interactions and quantum hopping on the properties of electronic systems in a localized phase, approaching an insulator-metal transition. The generic models in this regime are the quantum Coulomb glass and its generalization to electrons with spin. After introducing these models we explain our computational method, the Hartree-Fock-based diagonalization. We then discuss the conductance and compare spinless fermions and electrons. It turns out that spin degrees of freedom do not play an essential role in the systems considered. Finally, we analyse localization and decay of single-particle excitations. We find that interactions generically tend to localize these excitations, which is a result of the Coulomb gap in the single-particle density of states.