Electromagnetic fields in curved spacetimes

TL;DR

This paper derives exact covariant wave equations for electromagnetic fields in general curved spacetimes, revealing how gravitational fields influence electromagnetic wave propagation and suggesting mechanisms for magnetic field amplification in cosmology.

Contribution

It provides a fully covariant formulation of electromagnetic wave evolution in arbitrary spacetimes, explicitly identifying gravitational sources affecting electromagnetic disturbances.

Findings

Gravitational fields act as sources for electromagnetic waves.

Superadiabatic amplification of large-scale magnetic fields in open Friedmann models.

Exact wave equations applicable to general curved spacetimes.

Abstract

We consider the evolution of electromagnetic fields in curved spacetimes and calculate the exact wave equations of the associated electric and magnetic components. Our analysis is fully covariant, applies to a general spacetime and isolates all the sources that affect the propagation of these waves. Among others, we explicitly show how the different parts of the gravitational field act as driving sources of electromagnetic disturbances. When applied to perturbed FRW cosmologies, our results argue for a superadiabatic-type amplification of large-scale cosmological magnetic fields in Friedmann models with open spatial curvature.