Mean field theory for Coulomb systems

We study a classical charge symmetric system with an external charge distribution q in three dimensions in the limit that the plasma parameter e{open}→ zero. We prove that if q is scaled appropriately then the correlation functions converge pointwise to those of an ideal gas in the external mean field Ψ(x) where Ψ is given by-ΔΨ+ 2z sinh(βΨ) =q This is the mean field equation of Debye and Hückel. The proof uses the sine-Gordon transformation, the Mayer expansion, and a correlation inequality.