### Abstract or Additional Information

Abstract: The S-matrix is among the most basic -- and most physically relevant -- observables in any quantum field theory. At tree-level, it is well-defined even for theories that are not UV finite, such as general relativity, and captures the full non-linear complexity of the equations of motion. The traditional Feynman approach to computing S-matrix elements (scattering amplitudes) relies on a space-time Lagrangian description of the QFT we are interested in. However, remarkably compact expressions have been discovered for the full tree-level S-matrix of a wide array of massless QFTs which have no obvious derivation from standard Feynman rules. I will discuss how such formulae arise from certain two-dimensional conformal field theories. These 2d models give novel expressions for the S-matrix at higher loop orders (when this is well-defined) and also encode the equations of motion which we would usually think of as arising from a space-time Lagrangian.

About the speaker:

Dr. Tim Adamo graduated in 2009 from Pitt with B.S. in mathematics. One of our best math majors, Tim started doing research work here at Pitt in mathematical physics and game theory. He then went on to get his D. Phil from Oxford, followed by postdoctoral work at Cambridge and his present position at the Imperial College. His current research interests include

- Mathematical structures of gauge theory, gravity, and their observables
- Aspects of twistor theory and string theory
- Classical general relativity, asymptotic gravitation, null geodesic congruences