QED coupled to QEG

TL;DR

This paper investigates the non-perturbative renormalization group flow of QED coupled to QEG, identifying fixed points that could enable a consistent, interacting quantum field theory of gravity and electromagnetism.

Contribution

It finds two fixed points in the RG flow of QED coupled to QEG, one with a free IR fine-structure constant and one with a predicted non-zero IR value, advancing the asymptotic safety approach.

Findings

Two fixed points suitable for asymptotic safety.

One fixed point predicts a non-zero IR fine-structure constant.

The other fixed point leaves the IR value of the fine-structure constant undetermined.

Abstract

We discuss the non-perturbative renormalization group flow of Quantum Electrodynamics (QED) coupled to Quantum Einstein Gravity (QEG) and explore the possibilities for defining its continuum limit at a fixed point that would lead to a non-trivial, i.e. interacting field theory. We find two fixed points suitable for the Asymptotic Safety construction. In the first case, the fine-structure constant vanishes at the fixed point and its infrared ("renormalized") value is a free parameter not determined by the theory itself. In the second case, the fixed point value of the fine-structure constant is non-zero, and its infrared value is a computable prediction of the theory.