Two-loop scattering amplitudes from the Riemann sphere
Two-loop scattering amplitudes from the Riemann sphere
The scattering equations give striking formulas for massless scattering amplitudes at tree level and, as shown recently, at one loop. The progress at loop level was based on ambitwistor-string theory, which naturally yields the scattering equations. We proposed that, for ambitwistor strings, the standard loop expansion in terms of the …