ABSTRACT
Attraction between two indentical objects uniformly charged in
solution seems intuitively surprising on one hand because we
know that such objects do repel in vacuum and on another hand
because this simple mental picture is still preserved within the
Poisson-Boltzmann (PB) theory [40, 43, 47]. We recall that the PB
theory is a mean field approximation [39] of a primitive model of
electrolytes [16] in which ions are point-like and solvent is simply
a uniform medium of dielectric constant ε. Attraction mechanisms
mediated by counterions require therefore to modify at least one
of the aforementioned assumptions. We will see that one can find
attraction by (a) finding a situation in which two nonuniformly like
charged objects can attract each other even in vacuum, (b) adopting
another theoretical approximation for the samemodel of electrolyte,
and (c) changing the model for the ions.
