Anisotropic effects of background fields on Born–Infeld electromagnetic waves

We show exact solutions of the Born–Infeld theory for electromagnetic plane waves propagating in the presence of static background fields. The non-linear character of the Born–Infeld equations generates an interaction between the background and the wave that changes the speed of propagation and adds a longitudinal component to the wave. As a consequence, in a magnetic background the ray direction differs from the propagation direction—a behavior resembling the one of a wave in an anisotropic medium. This feature could open up a way to experimental tests of the Born–Infeld theory.