Classical resummation and breakdown of strong-field QED: https://arxiv.org/abs/2101.12111
T. Heinzl, A. Ilderton, B. King
QED perturbation theory has been conjectured to break down in sufficiently strong backgrounds, obstructing the analysis of strong-field physics. We show that the breakdown occurs even in classical electrodynamics, at lower field strengths than previously considered, and that it may be cured by resummation. As a consequence, an analogous resummation is required in QED. A detailed investigation shows, for a range of observables, that unitarity removes diagrams previously believed to be responsible for the breakdown of QED perturbation theory.
Comments: 5 pages, 2 figures