Upper bound on the Abelian gauge coupling from asymptotic safety

TL;DR

This paper investigates how asymptotically safe quantum gravity influences the Abelian gauge coupling, establishing an upper bound on its infrared value and connecting quantum gravity effects to Standard Model parameters.

Contribution

It demonstrates that quantum gravity fluctuations can induce a power-law running of the gauge coupling and set an upper bound on its value, linking quantum gravity to Standard Model predictions.

Findings

Quantum gravity can trigger a free fixed point for the gauge coupling.

Quantum gravity fluctuations generate an interacting fixed point acting as a boundary.

An upper bound of approximately 35% above the Standard Model hypercharge coupling is found.

Abstract

We explore the impact of asymptotically safe quantum gravity on the Abelian gauge coupling in a model including a charged scalar, confirming indications that asymptotically safe quantum fluctuations of gravity could trigger a power-law running towards a free fixed point for the gauge coupling above the Planck scale. Simultaneously, quantum gravity fluctuations balance against matter fluctuations to generate an interacting fixed point, which acts as a boundary of the basin of attraction of the free fixed point. This enforces an upper bound on the infrared value of the Abelian gauge coupling. In the regime of gravity couplings which in our approximation also allows for a prediction of the top quark and Higgs mass close to the experimental value [1], we obtain an upper bound approximately 35% above the infrared value of the hypercharge coupling in the Standard Model.