# A new look at the pertubative expansion of quantum field theory

#### A new look at the pertubative expansion of quantum field theory

- Event time: 2:00pm
- Event date: 8th March 2017
- Speaker: Piotr Tourkine (DAMTP Cambridge)
- Location: Higgs Centre Seminar Room, Room 4305, James Clerk Maxwell Building (JCMB) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB

### Event details

Scattering amplitudes are crucial in high energy physics. They bridge the gap between theory and experiment, and major progress over the last 25 years have lead us to discover an unexpected simplicity underlying the theories that describe nature (gauge, gravity).

In this talk I aim to introduce an elegant formalism that takes a radically new look to the computation of S-matrix elements, based on the Cachazo-He-Yuan formulae and the ambitwistor string.

I will present some work of mine, in collaboration with two distinct groups (*). This first part will concern the extension of this formalism to loops. The second explains that the deep raison d’être of this elegant formalism is a special kind of string theory called “null strings”, whose quantization give rise to ambitwistor strings.

This program gives the hope to be able to develop a complete reformulation of the loop expansion in QFTs.

(*): (Geyer-Mason-Monteiro; Casali-Herfray)

### 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..