ABSTRACT
Field theoretic approaches have been particularly useful in studying
colloidal and biological systems, in which long-range electrostatic
interactions are important. For weakly coupled systems, the field
theoretic methods reduce to the commonly known Poisson-
Boltzmann (PB) theory [Chapman (1913); Gouy (1910)], which
has been shown to be very accurate for these systems and has
been used with great success to understand and solve numerous
problems in soft matter. However, in recent decades, focus has
turned toward strongly coupled systems, where highly charged
surfaces or multivalent counterions introduce strong correlations,
that cannot be treated by amean field theory or approaches inwhich
the fluctuations are assumed to be weak (e.g., loop expansions).
These correlations are important in many systems [Levin (2002);
Naji et al. (2005); Messina (2009)] and can lead to many effects that cannot be explained by the PB theory, such as attraction between
like-charged surfaces.
