ZERO-BIAS ANOMALY IN FINITE-SIZE SYSTEMS

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