One-loop multicollinear limits from 2-point amplitudes on self-dual backgrounds

Tim Adamo*, Anton Ilderton, Alexander J. MacLeod

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


For scattering amplitudes in strong background fields, it is -- at least in principle -- possible to perturbatively expand the background to obtain higher-point vacuum amplitudes. In the case of self-dual plane wave backgrounds we consider this expansion for two-point, one-loop amplitudes in pure Yang-Mills, QED and QCD. This enables us to obtain multicollinear limits of 1-loop vacuum amplitudes; the resulting helicity configurations are surprisingly restricted, with only the all-plus helicity amplitude surviving. These results are shown to be consistent with well-known vacuum amplitudes. We also show that for both abelian and non-abelian supersymmetric gauge theories, there is no helicity flip (and hence no vacuum birefringence) on any plane wave background, generalising a result previously known in the Euler-Heisenberg limit of super-QED.
Original languageEnglish
Article number207
Pages (from-to)1-31
Number of pages31
JournalJournal of High Energy Physics
Issue number12
Publication statusPublished - 28 Dec 2021


  • hep-th
  • hep-ph


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