Pair production in strong fields: The Trident process
The process of electron-positron pair production in strong fields deviates from the well-known perturbative result in weak field backgrounds. In a strong field background an electron can directly emit a photon which in turn can generate a pair. The investigation of the strong field Trident process shows that the emission of a real photon dominates the electron-field interaction at low background field strength while pair production via a virtual photon can no longer be neglected at high background fields. The second order Trident process could play a dominant role in situations of ultra-strong fields and small field volumes.