Ionic criticality : an exactly soluble model

Gas-liquid criticality in ionic fluids is studied in exactly soluble spherical models that use interlaced sublattices to represent hard-core \textit{multi}component systems. Short range attractions in the uncharged fluid drive criticality but charged ions do not alter the universality class. Debye screening remains exponential \textit{at} criticality in charge-symmetric 1:1 models. However, \textit{asymmetry} couples charge and density fluctuations in a direct manner: the charge correlation length then diverges precisely as the density correlation length and the Stillinger-Lovett rule is violated \textit{at} criticality.