Fluctuations in electrolytes: The Lebowitz and other correlation lengths

Explicit low-density expansions (using Meeron and hypernetted-chain graphic al resummations) are reported for various charge and density correlation le ngths in hard-sphere electrolytes with general valences, z(sigma), and diam eters, a(sigma tau). The "Lebowitz length" quantifies the area law for char ge fluctuations, [Q(Lambda)(2)], in a large domain Lambda; it approaches bu t differs from the Debye and other correlation lengths. All corresponding, universal limiting-law predictions of generalized Debye-Huckel (GDH) theory (Lee and Fisher, 1996-1997) prove exact, thus validating GDH theory as a b asis for studying anomalies in Coulombic criticality.