Birefringence and non-transversality of light propagation in an ultra-strongly magnetized vacuum

Abstract

The birefringence phenomenon in the vacuum with a constant magnetic background of arbitrary strength is considered within the framework of the effective action approach. A new feature of the birefringence in a magnetized vacuum is that the parallel mode, which is polarized parallel to the plane containing the magnetic field and the photon wave vector, is no longer transverse. We have studied this feature in detail for arbitrary magnetic field and provided analytic results for the ultra-strong magnetic field regime. Possible physical implications of our results in astrophysics are discussed.