Two-loop renormalisation of gauge theories in $4D$ Implicit Regularisation and connections to dimensional methods

TL;DR

This paper calculates the two-loop beta functions for various gauge theories using Implicit Regularization in four dimensions, comparing it with dimensional methods and confirming gauge invariance properties.

Contribution

It introduces a fully four-dimensional Implicit Regularization approach for two-loop calculations and compares it with established dimensional methods, clarifying subtleties in gauge invariance.

Findings

IREG reproduces known two-loop beta functions.

Momentum routing invariance ensures gauge invariance in IREG.

Comparison shows consistency with dimensional regularization methods.

Abstract

We compute the two-loop $\beta$-function of scalar and spinorial quantum electrodynamics as well as pure Yang-Mills and quantum chromodynamics using the background field method in a fully quadridimensional setup using Implicit Regularization (IREG). Moreover, a thorough comparison with dimensional approaches such as conventional dimensional regularization (CDR) and dimensional reduction (DRED) is presented. Subtleties related to Lorentz algebra contractions/symmetric integrations inside divergent integrals as well as renormalisation schemes are carefully discussed within IREG where the renormalisation constants are fully defined as basic divergent integrals to arbitrary loop order. Moreover, we confirm the hypothesis that momentum routing invariance in the loops of Feynman diagrams implemented via setting well-defined surface terms to zero deliver non-abelian gauge invariant amplitudes within IREG just as it has been proven for abelian theories.