Ghost anomalous dimension in asymptotically safe quantum gravity

TL;DR

This paper calculates the ghost anomalous dimension in asymptotically safe quantum gravity, showing it is negative and supports the theory's UV completeness, with minimal impact on gravitational fixed points.

Contribution

It provides the first detailed computation of the ghost anomalous dimension within the asymptotic-safety framework, confirming the stability of the non-Gaussian fixed point.

Findings

Ghost anomalous dimension is negative, indicating improved UV behavior.

Backreaction of ghost flow preserves the non-Gaussian fixed point.

Gauge dependence of fixed points is slightly reduced.

Abstract

We compute the ghost anomalous dimension within the asymptotic-safety scenario for quantum gravity. For a class of covariant gauge fixings and using a functional RG scheme, the anomalous dimension $\eta_c$ is negative, implying an improved UV behavior of ghost fluctuations. At the non-Gaussian UV fixed point, we observe a maximum value of $\eta_c\simeq -0.78$ for the Landau-deWitt gauge within the given scheme and truncation. Most importantly, the backreaction of the ghost flow onto the Einstein-Hilbert sector preserves the non-Gaussian fixed point with only mild modifications of the fixed-point values for the gravitational coupling and cosmological constant and the associated critical exponents; also their gauge dependence is slightly reduced. Our results provide further evidence for the asymptotic-safety scenario of quantum gravity.