Asymptotic safety in higher-derivative gravity

TL;DR

This paper investigates the non-perturbative renormalization group flow of higher-derivative gravity, revealing a non-trivial ultraviolet fixed point that supports the asymptotic safety conjecture and discusses implications for unitarity.

Contribution

It demonstrates the existence of a non-trivial UV fixed point in higher-derivative gravity using functional renormalization group methods, advancing the asymptotic safety program.

Findings

Identification of a non-trivial UV fixed point with three attractive and one repulsive directions.

Non-perturbative effects shift the known perturbative fixed point.

Discussion on the impact of fixed point structure on unitarity in higher-derivative gravity.

Abstract

We study the non-perturbative renormalization group flow of higher-derivative gravity employing functional renormalization group techniques. The non-perturbative contributions to the $\beta$-functions shift the known perturbative ultraviolet fixed point into a non-trivial fixed point with three UV-attractive and one UV-repulsive eigendirections, consistent with the asymptotic safety conjecture of gravity. The implication of this transition on the unitarity problem, typically haunting higher-derivative gravity theories, is discussed.