Covariant Loop Quantum Gravity, Low Energy Perturbation Theory, and Einstein Gravity with High Curvature UV Corrections

TL;DR

This paper develops a low-energy perturbation theory from covariant Loop Quantum Gravity, revealing that LQG introduces high curvature UV corrections to Einstein gravity, advancing understanding of its quantum and high-energy modifications.

Contribution

It presents the first covariant LQG-based perturbation theory showing UV modifications to Einstein gravity at high curvature regimes.

Findings

LQG produces high curvature UV corrections to Einstein gravity.

The leading order matches Einstein-Hilbert action.

Subleading terms organize quantum and high-energy modifications.

Abstract

A low-energy perturbation theory is developed from the nonperturbative framework of covariant Loop Quantum Gravity (LQG) by employing the background field method. The resulting perturbation theory is a 2-parameter expansion in the semiclassical and low-energy regime. The two expansion parameters are the large spin and small curvature. The leading order effective action coincides with the Einstein-Hilbert action. The subleading corrections organized by the two expansion parameters give the modifications of Einstein gravity in quantum and high-energy regime from LQG. The perturbation theory developed here shows for the first time that covariant LQG produces the high curvature corrections to Einstein gravity. This result means that LQG is not a naive quantization of Einstein gravity, but rather provides the UV modification. The result of the paper may be viewed as the first step toward understanding the UV completeness of LQG.