Vacuum fluctuations of quantum fields are altered in the presence of a strong gravitational background, with important physical consequences. We argue that a nontrivial spacetime geometry can act as an optically active medium for quantum electromagnetic radiation, in such a way that the state of polarization of radiation changes in time, even in the absence of electromagnetic sources. This is a quantum effect, and is a consequence of an anomaly related to the classical invariance under electric-magnetic duality rotations in Maxwell theory.
Publication Source (Journal or Book title)
International Journal of Modern Physics D
Agullo, I., Del Rio, A., & Navarro-Salas, J. (2017). Gravity and handedness of photons. International Journal of Modern Physics D, 26 (12) https://doi.org/10.1142/S0218271817420019