Faraday rotation near charged black holes and other electrovacuum geometries

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Abstract
In space permeated by a steady background electromagnetic field a gravitational wave and an electromagnetic wave not only undergo beat frequency oscillations, but the linear polarizations of these waves undergo Faraday rotations as well. The beating and the Faraday rotations are inextricably related. The classification of these phenomena requires three parameters, the three Euler parameters of SU(2). They specify in a more general sense the "polarization" of an electrograviton mode. The evolution of the beat frequency oscillations and the Faraday rotations along a propagating wave front is described as a moving point in SU(2). Consequently, a charged black hole serves not only as a catalyst for converting suitably directed electromagnetic radiation into gravitational radiation, but also as an agent that randomized the linear polarizations of radiation emerging from it. An assessment of these phenomena in relation to the origin of Weber's signals is given.