Crystal-assisted quantum electrodynamics; pair production and radiation

When energetic particles travel along crystal axes or planes, radiation and pair creation are altered by coherent effects associated with multiple scattering. The effective transverse crystal fields, obtained by averaging along the trajectory of the incident particles, is the source of anomalous rates of pair creation and radiation. The theory of the quantum electrodynamic processes in crystal fields is closely related to theories of pair creation and radiation in the ultra-strong fields which are only seen in the astrophysical world. However, it is now clear that an accurate description of recent experimental data must go beyond the simplest application of homogeneous strong-field theory: the variations of the fields within the crystal cannot be ignored, and they lead to significant modifications of the theoretical predictions.