Gravitational analog of Faraday rotation in the magnetized Kerr and Reissner-Nordstr\"om spacetimes

Understand

It is known that the gravitational analog of the Faraday rotation arises in the rotating spacetime due to the nonzero gravitomagnetic field.

• In this paper, we show that it also arises in the "nonrotating" Reissner-Nordstr\"om spacetime, if it is immersed in a uniform magnetic field.
• The non-zero angular momentum (due to the presence of electric charge and magnetic field) of the electromagnetic field acts as the twist potential to raise the gravitational Faraday rotation as well as the gravitational Stern-Gerlach effect in the said spacetimes.
• The twisting can still exist even if the mass of the spacetime vanishes.