The gravitational Higgs mechanism and resulting smoking gun effects

TL;DR

This paper explores a toy model where a scalar field causes spontaneous symmetry breaking in compact objects, leading to a massive gauge field, and investigates potential violations of the Weak Equivalence Principle in neutron stars.

Contribution

It provides a physical example of how the gravitational Higgs mechanism can lead to observable effects and potential WEP violations in neutron star magnetic fields.

Findings

Scalarization causes gauge field mass generation.

Differences in magnetic field behavior between theories.

Potential observable signatures of WEP violations.

Abstract

Recently, a toy model was introduced to demonstrate that screening mechanisms in alternative theories of gravitation can hide additional effects. In this model a scalar field is charged under a $U(1)$ symmetry. In sufficiently compact objects the scalar field spontaneously grows, i.e. the object scalarizes, spontaneously breaking the $U(1)$ symmetry. Exactly as in the $U(1)$ Higgs mechanism this leads to the emergence of a mass for the gauge field. The aim of this paper is to provide an example of the physical consequences if we consider this toy model as a prototype of Weak Equivalence Principle (WEP) violations. We model neutron stars with a dipolar magnetic field to compare the magnetic field behaviour of stars in Einstein-Maxwell theory on the one hand and in scalar-tensor theory with the, so-called, gravitational Higgs mechanism on the other hand.