Asymptotic safety of gravity-matter systems

TL;DR

This paper investigates the ultraviolet stability of gravity-matter systems using the functional renormalisation group, revealing that such systems are generally ultraviolet stable and that matter content does not constrain asymptotic safety within certain bounds.

Contribution

It extends the asymptotic safety analysis to general gravity-matter systems with dynamical couplings and compares fixed points to background counterparts, highlighting the robustness of the scenario.

Findings

Gravity-fermion systems are ultraviolet stable.

Gravity-scalar systems are ultraviolet stable within certain bounds.

Dynamical couplings differ significantly from background ones with matter inclusion.

Abstract

We study the ultraviolet stability of gravity-matter systems for general numbers of minimally coupled scalars and fermions. This is done within the functional renormalisation group setup put forward in \cite{Christiansen:2015rva} for pure gravity. It includes full dynamical propagators and a genuine dynamical Newton's coupling, which is extracted from the graviton three-point function. We find ultraviolet stability of general gravity-fermion systems. Gravity-scalar systems are also found to be ultraviolet stable within validity bounds for the chosen generic class of regulators, based on the size of the anomalous dimension. Remarkably, the ultraviolet fixed points for the dynamical couplings are found to be significantly different from those of their associated background counterparts, once matter fields are included. In summary, the asymptotic safety scenario does not put constraints on the matter content of the theory within the validity bounds for the chosen generic class of regulators.