Constraining a possible dependence of Newton's constant on the Earth's magnetic field

Abstract

Some time ago Mbelek and Lachieze-Rey proposed that the discrepancy between the results of the various measurements of Newton's constant could be explained by introducing a gravielectric coupling between the Earth's gravitational and magnetic fields mediated by two scalar fields. A critical assessment of this model is performed. By calculating the static field configuration of the relevant scalar around a nucleus in the linearised theory and then folding this result with the mass density of the nucleus its effective gravitational mass is determined. Considering test bodies of different materials one finds violations of the weak equivalence principle for torsion-balance experiments which are four orders of magnitude beyond the current experimental limit, thus rendering the model non-viable. The method presented can be applied to generic theories with gravielectric coupling and seems to rule out in general the explanation of the discrepant measurements of Newton's constant by such couplings.