Simplicity in the Structure of QED and Gravity Amplitudes

Understand

We investigate generic properties of one-loop amplitudes in unordered gauge theories in four dimensions.

• For such theories the organisation of amplitudes in manifestly crossing symmetric expressions poses restrictions on their structure and results in remarkable cancellations.
• We show that one-loop multi-photon amplitudes in QED with at least eight external photons are given only by scalar box integral functions.
• This QED `no-triangle' property is true for all helicity configurations and has similarities to the `no-triangle' property found in the case of maximal N = 8 supergravity.