The weak-gravity bound in asymptotically safe gravity-gauge systems

TL;DR

This paper investigates the weak-gravity bound in complex gravity-gauge systems with multiple gauge fields, examining its implications for the dimensionality of spacetime and the robustness of asymptotic safety.

Contribution

It extends the analysis of the weak-gravity bound to systems with many gauge fields and tests its dependence on gauge parameters, strengthening the case for a mechanism explaining four-dimensional spacetime.

Findings

Weak-gravity bound persists in systems with 12 gauge fields.

The gravitational fixed point can evade the weak-gravity bound under certain conditions.

Results are robust against variations in gravitational gauge parameters.

Abstract

The weak-gravity bound has been discovered in asymptotically safe gravity-matter systems, where it limits the maximum strength of gravitational fluctuations. In the present paper, we explore it for the first time in systems with more than one gauge field, to discover whether systems with 12 gauge fields (like the Standard Model) exhibit a weak-gravity bound and whether the gravitational fixed point evades it. Further, we test the robustness of the present and previous results on the weak-gravity bound by exploring their dependence on a gravitational gauge parameter. Finally, the existence of the weak-gravity bound also has important phenomenological consequences: it is key to a proposed mechanism that bounds the spacetime dimensionality from above to four or five dimensions. In this paper, we strengthen the evidence for this mechanism. Thus, the predictive power of the asymptotic safety paradigm could extend to parameters of the spacetime geometry, such that the four-dimensionality of our universe could be explained from first principles.