Gravitationally coupled magnetic monopole and conformal symmetry breaking

TL;DR

This paper explores a conformally invariant Georgi-Glashow model coupled to gravity, where spontaneous symmetry breaking via gravitation leads to magnetic monopoles with Schwarzschild-AdS metrics, revealing emergent Einstein-Hilbert gravity.

Contribution

It demonstrates how conformal symmetry can be spontaneously broken by gravity, resulting in magnetic monopoles with emergent Einstein-Hilbert dynamics in the effective theory.

Findings

Magnetic monopole solutions in conformal gravity context

Emergence of Einstein-Hilbert term after symmetry breaking

Monopoles exhibit Schwarzschild-AdS spacetime outside the core

Abstract

We consider a Georgi-Glashow model conformally coupled to gravity. The conformally invariant action includes a triplet of scalar fields and SO(3) non-Abelian gauge fields. However, the usual mass term $\mu^2 \phi^2$ is forbidden by the symmetry and this role is now played by the conformal coupling of the Ricci scalar to the scalar fields. Spontaneous symmetry breaking occurs via gravitation. The spherically symmetric solutions correspond to localized solitons (magnetic monopoles) in asymptotically anti-de-Sitter (AdS) space-time and the metric outside the core of the monopole is found to be Schwarzschild-AdS. Though conformal symmetry excludes the Einstein-Hilbert term in the original action, it emerges in the effective action after spontaneous symmetry breaking and dominates the low-energy/long-distance regime outside the core of the monopole.