Sum rules in charged fluids

The screening effects in fluid phases of charged particles give rise to a variety of exact sum rules for their correlation functions. Some of them have been known for a long time, while others have been derived more recently—in particular, for nonuniform fluids. A presentation of these sum rules for static and time-displaced, classical or quantum-mechanical correlations is given from a unifying viewpoint: they appear as consistency relations imposed by the long range of the Coulomb force in the equilibrium or dynamical equations. The cluster properties and the fluctuations of electrical quantities are also discussed.