Dispersion relation for electromagnetic wave propagation in a strongly   magnetized plasma
  A dispersion relation for electromagnetic wave propagation in a strongly magnetized cold plasma is deduced, taking photon-photon scattering into account. It is shown that the combined plasma and quantum electrodynamic effect is important for understanding the mode-structures in magnetar and pulsar atmospheres. The implications of our results are discussed. 
G. Brodin M. Marklund, L. Stenflo and P.K. Shukla