The effect of gravitation on the polarization state of a light ray

TL;DR

This paper derives how the polarization of light is rotated by the gravitational field of a rotating body using Kerr geometry, showing that such effects are absent in non-rotating (Schwarzschild) spacetime and depend on the impact parameter.

Contribution

It provides a theoretical derivation of polarization rotation due to gravity in Kerr spacetime, extending previous work by considering impact parameters and orbit directions.

Findings

Polarization rotation occurs only in rotating (Kerr) spacetime.

No polarization rotation in non-rotating (Schwarzschild) spacetime.

The effect depends on impact parameter and orbit direction.

Abstract

In the present work the rotation of polarization vector due to the gravitational field of a rotating body has been derived, from the general expression of Maxwell's equation in the curved space-time. Considering the far field approximation (i.e impact parameter is greater than the Schwarzschild radius and rotation parameter), the amount of rotation of polarization vector as a function of impact parameter has been obtained for a rotating body (considering Kerr geometry). Present work shows that, the rotation of polarization vector can not be observed in case of Schwarzschild geometry. This work also calculates the effect, considering prograde and retrograde orbit for the light ray. Although the present work demonstrates the effect of rotation of polarization vector for electromagnetic wave (light ray), but it confirms that there would be no net polarization of electromagnetic wave due to the curved space-time geometry.