B. King, N. Elkina, H. Ruhl
An electromagnetic pair-creation cascade seeded by an electron or a photon in an intense plane wave interacts in a complicated way with the external field. Many simulations neglect the vector nature of photons by including their interaction using unpolarised cross-sections. After deriving rates for the tree-level processes of non-linear Compton scattering and pair creation with an arbitrary linearly-polarised photon in a constant-crossed field, we present results of numerical simulations that include the photon's vector nature. The simulations of seed electrons in a rotating electric field of optical frequency on the one hand support the approximation of using unpolarised cross-sections for tree-level processes to within around 5 percent, whereas on the other, indicate after 0.15 external-field periods, more than a factor 3 difference in the distribution of photon polarisations and more than a 40 percent difference in the number of pairs created by these polarisations. Moreover, these figures were seen to increase with simulation time. The results are particularly of relevance when the external field is anisotropic and the polarisation of the photon is influenced by its environment.
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http://arxiv.org/abs/1301.7001
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