About the connection between vacuum birefringence and the light–light scattering amplitude

Birefringence phenomena stemming from vacuum polarization are revisited in the framework of coherent scattering. Based on photon–photon scattering, our analysis brings out the direct connection between this process and vacuum birefringence. We show how this procedure can be extended to the Kerr and the Cotton–Mouton birefringences in vacuum, thus providing a unified treatment of various polarization schemes, including those involving static fields.