Renormalization group flow equations connected to the $n$PI effective action

TL;DR

This paper establishes a connection between the 4PI effective action and renormalization group flow equations, deriving a hierarchy of Bethe-Salpeter-like equations that facilitate non-perturbative analysis.

Contribution

It introduces a hierarchy of integral equations from the 4PI effective action that can truncate the renormalization group flow equations, linking two non-perturbative methods.

Findings

Flow equations become total derivatives with respect to the flow parameter.

Truncation is equivalent to solving the nPI equations of motion.

Connects 4PI effective action with renormalization group methods.

Abstract

In this paper we derive a hierarchy of integral equations from the 4PI effective action which have the form of Bethe-Salpeter equations. We show that the vertex functions defined by 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. We also show that the truncation is equivalent to solving the $n$PI equations of motion. This result establishes a direct connection between two non-perturbative methods.