  The 4PI effective action provides a a hierarchy of integral equations which
have the form of Bethe-Salpeter equations. The vertex functions obtained from
these equations can be used to truncate the exact renormalization group flow
equations. This truncation has the property that the flow is a total derivative
with respect to the flow parameter and is equivalent to solving the nPI
equations of motion. This result establishes a direct connection between two
non-perturbative methods.
