| An effective field theory exists describing a large class of Coulomb gas problems that arise in biophysics and colloid science: the lowest order (mean field) version of this theory takes the form of a generalized Poisson-Boltzmann theory. Interaction terms depend on details (dielectric constant profile, finite-size effects, multipole properties, etc.). Convergence of the loop expansion holds only if mutual interactions of mobile charges are small compared to their interaction with the fixed-charge environment, which is frequently not the case. Problems with the strongly-coupled effective field theory can be circumvented via an alternative local lattice formulation, with real positive action. As an example, a system consisting of like charged parallel plates confining an aqueous solution of oppositely charged counterions is studied. Under certain conditions the plates are found to attract each other, an effect which is entirely missed by Poisson-Boltzmann theory. |
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