2017MNRAS.472.2398V

We analyse the spectrum of the Hamiltonian of a photon propagating in a strong magnetic field B ∼ B_cr, where B_cr= m^2/e ∼eq 4.4 x 10^{13} G is the Schwinger critical field. We show that the anomalous magnetic moment of a photon in the one-loop approximation is a non-decreasing function of the magnetic field B in the range 0 <= B <= 30 B_cr. We provide a numerical representation of the expression for the anomalous magnetic moment in terms of special functions. We find that the anomalous magnetic moment m_g of a photon for B = 30 B_cr is 8/3 of the anomalous magnetic moment of a photon for B = 1/2B_cr. Based on the recent observational evidence for vacuum birefringence from the neutron star RX J1856.5-3764 by Mignani et al., we suggest vacuum birefringence, the anomalous magnetic moment of the photon and the Faraday rotation angle as key observables for future experiments and measurements.