Abstract:
In the weak field limit of Einstein gravity, there are gravitational analogues of the vector potential and the magnetic field. The equivalence principle guides us to a magnetic-like interaction arising from inertial acceleration. The spin precession due to this accelero-magnetic field is identified as the Thomas precession. Hence the torque that is responsible for the precession of the spin is identified as resulting from a physical interaction with a magnetic-like inertial-field. Once the equivalence principle is assumed to some accuracy, well supported by precision tests, this implies that the average effect of the accelero-magnetic field on a classical or quantum gyroscope is the same as that of the gravito-magnetic field on a gyroscope. Precision spectroscopy of spin-orbit doublets in atoms is hence an indirect high precision test of the existence and properties of the gravito-magnetic field. This also implies that the planned and current experiments will not see any deviations from the predictions of general relativity. This line of thought is extended to a brief discussion on the possibility of formulating an independent equivalence principle for the spin.
