The rotation of polarization by gravitational waves

TL;DR

This paper clarifies the gravitational Faraday rotation effect on electromagnetic polarization caused by gravitational waves, showing it is negligible for localized waves and minimal for cosmological ones, resolving conflicting literature claims.

Contribution

It provides a simple formalism to analyze polarization rotation, demonstrating that the effect is a boundary phenomenon and clarifying previous conflicting statements.

Findings

Rotation angle vanishes for localized gravitational waves

Non-zero but negligible for cosmological gravitational waves

Boundary effect explanation for polarization rotation

Abstract

There are conflicting statements in the literature about the gravitational Faraday rotation of the plane of polarization of polarized electromagnetic radiation travelling through a gravitational wave. This issue is reconsidered using a simple formalism describing the rotation of the plane of polarization in a gravitational field, in the geometric optics approximation. It is shown that, to first order in the gravitational wave amplitude, the rotation angle is a boundary effect which vanishes for localized (astrophysically generated) gravitational waves and is non-zero, but nevertheless negligible, for cosmological gravitational waves.