Polarization effects on light propagation in gravitational fields

<p>The effects of a gravitational field on the propagation of electromagnetic waves in a vacuum are typically analyzed using geometric optics. In this approach, high-frequency electromagnetic waves are treated as rays that follow null geodesics. However, this model is only precisely accurate when light frequencies approach infinity. For finite frequencies, there exists a polarization-dependent deviation known as the gravitational spin-Hall effect of light. This effect becomes particularly significant when considering propagation over substantial astronomical distances and emissions from regions with strong gravitational fields, especially for radio and microwaves.</p> <p>We use a recently developed covariant spin-optics method to investigate this effect in Schwarzschild spacetimes. These provide both the simplest mathematical setting that gives a chance to obtain analytical results that are important for qualitative understanding of the phenomena, and adequate description for the Solar-system observations. We conduct perturbative calculations, starting from exact solutions for null geodesics. As a result, we derive explicit expressions for the resulting trajectories and assess the magnitude of the effect concerning the gravitational deflection of light.</p> <p>Key findings are as follows: (1) Polarization-induced corrections are absent for radially propagating light. (2) The corrections occur orthogonally to the plane of the unperturbed geodesic trajectory. (3) These corrections are particularly significant for low-energy electromagnetic waves, such as radio waves, and may even be observable with the current technology.</p>