# Four loop scalar $\phi^4$ theory using the functional renormalization group

## TL;DR

This paper demonstrates a simplified four-loop calculation in scalar $\,\phi^4$ theory using a functional renormalization group approach, avoiding complex counterterm procedures typical in standard methods.

## Contribution

It introduces a renormalization group method for four-loop 2PI calculations that uses only one bare coupling, simplifying the process compared to traditional techniques.

## Key findings

- Successfully performs four-loop 2PI calculation with RG method
- Method can be extended to four-particle irreducible (4PI) level
- Simplifies renormalization by reducing counterterm complexity

## Abstract

We consider a symmetric scalar theory with quartic coupling in 4-dimensions. We show that the 4 loop 2PI calculation can be done using a renormalization group method. The calculation involves one bare coupling constant which is introduced at the level of the Lagrangian and is therefore conceptually simpler than a standard 2PI calculation, which requires multiple counterterms. We explain how our method can be used to do the corresponding calculation at the 4PI level, which cannot be done using any known method by introducing counterterms.