Coarse-Grained Counterions in the Strong Coupling Limit

Recent Monte Carlo simulations (A. G. Moreira and R. R. Netz: Eur. Phys. J. E {\bf 8} (2002) 33) in the strong Coulomb coupling regime suggest strange counterion electrostatics unlike the Poisson-Boltzmann picture: when counterion-counterion repulsive interactions are much larger than counterion–macroion attraction, the coarse-grained counterion distribution around a macroion is determined only by the latter, and the former is irrelevant. Here, we offer an explanation for the apparently paradoxical electrostatics by mathematically manipulating the strong coupling limit.