Quantum gravity and Standard-Model-like fermions

TL;DR

This paper shows that quantum gravity models compatible with observations must preserve chiral symmetry, with implications for the standard model and dark matter, highlighting fixed points in the renormalization group flow.

Contribution

It demonstrates that chiral symmetry is maintained in asymptotically safe quantum gravity models and explores fixed points relevant for standard model extensions.

Findings

Chiral symmetry is not an infrared attractor under quantum gravity fluctuations.

A chiral fixed point exists in asymptotically safe gravity.

Models with more than 10 fermions lack the fixed point, impacting UV completions.

Abstract

We discover that chiral symmetry does not act as an infrared attractor of the renormalization group flow under the impact of quantum gravity fluctuations. Thus, observationally viable quantum gravity models must respect chiral symmetry. In our truncation, asymptotically safe gravity does, as a chiral fixed point exists. A second non-chiral fixed point with massive fermions provides a template for models with dark matter. This fixed point disappears for more than 10 fermions, suggesting that an asymptotically safe ultraviolet completion for the standard model plus gravity enforces chiral symmetry.