Zero-bias anomaly in finite-size systems

The small energy anomaly in the single-particle density of states of disordered interacting systems is studied for the zero-dimensional case. This anomaly interpolates between the nonperturbative Coulomb blockade and the perturbative limit, the latter being an extension of the Altshuler-Aronov zero-bias anomaly at d=0. Coupling of the zero-dimensional system to a dissipative environment leads to effective screening of the interaction and a modification of the density of states.