# Loop Amplitudes from Ambitwistor Strings

#### Loop Amplitudes from Ambitwistor Strings

- Event time: 2:00pm
- Event date: 28th March 2018
- Speaker: Ricardo Monteiro (Queen Mary University London)
- Location: Higgs Centre Seminar Room, 4305 James Clerk Maxwell Building (JCMB) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB

### Event details

I will describe recent progress in the study of scattering amplitudes in gauge theory and gravity via ambitwistor strings and the scattering equations, including loop level contributions. Ambitwistor strings are worldsheet models of quantum field theories, inspired by string theory. They naturally lead to a representation of amplitudes based on the scattering equations. I will describe how the usual loop-level string formalism of higher-genus Riemann surfaces can be avoided, by turning a higher-genus surface into a nodal Riemann sphere, with the nodes representing the loop momenta. This leads to new formulas for loop integrands in gauge theory and gravity, with or without supersymmetry.

#### Event resources

### About Particle Physics Theory seminars

The Particle Physics Theory seminar is a weekly series of talks reflecting the diverse interests of the group. Topics include analytic and numerical calculations based on the Standard Model of elementary particle physics, theories exploring new physics, as well as more formal developments in gauge theories and gravity..