Coulomb blockade without tunnel junctions

Tunnel junctions are not needed to provide single electron effects in a met allic island. Eventually the tunnel junction may be replaced by an arbitrar y scatterer. To formulate this in exact terms, we derive and analyze the ef fective action that describes an arbitrary scatterer. It is important that even a diffusive scatterer provides a sufficient isolation for single elect ron effects to persist. We also consider the fluctuations of the effective charging energy.