Phys. Rev. A 92, 032115 (2015)

Light propagation through vacuum can be modified due to the polarizability of virtual electron–positron pairs. By using numerical simulations and analytically solving modified Maxwell and wave equations, Patrick Böhl and Hartmut Ruhl from Ludwig-Maximilians-Universität München, together with Ben King from Plymouth University, have studied the effects of vacuum interactions on a plane probe pulse propagating through a strong electromagnetic field. Specifically, a pump–probe set-up is used with a linearly polarized oscillating plane wave (probe) counterpropagating through a stronger plane wave background (pump). Taking virtual electron–positron pair creation into account, their numerical simulations suggest that a shock wave can arise from vacuum high-harmonic generation. The team has identified a nonlinear shock parameter of ν ≈ 1, which indicates when the self-interaction of the probe due to the polarized vacuum becomes important and can be consistently described using a probe-dependent vacuum refractive index. The findings will be of importance for studies of X-ray pulsars and highly magnetized neutron stars or 'magnetars'.