Loop Amplitudes in an Extended Gravity Theory

TL;DR

This paper extends gravity's S-matrix with R^3 terms, analyzes its renormalizability using unitarity, and identifies one-loop R^4 counter-terms, revealing their relation to supersymmetric theories.

Contribution

It introduces an extended gravity theory with R^3 terms and applies unitarity to analyze its renormalization and counter-terms at one-loop.

Findings

Identification of R^4 counter-terms at one-loop

Complementarity of R^4 terms with supersymmetric Lagrangians

Demonstration of unitarity as a tool for renormalizability analysis

Abstract

We extend the $S$-matrix of gravity by the addition of the minimal three-point amplitude or equivalently adding $R^3$ terms to the Lagrangian. We demonstrate how Unitarity can be used to simply examine the renormalisability of this theory and determine the $R^4$ counter-terms that arise at one-loop. We find that the combination of $R^4$ terms that arise in the extended theory is complementary to the $R^4$ counter-term associated with supersymmetric Lagrangians.