Wednesday, December 14, 2016 1:00PM (334 JFB)
Title: Gauge and Gravity Scattering Amplitudes From CHY Formalism
In this thesis, we first review some recent progress on exploring the nature of scattering amplitudes. Then we present our recent work on direct evaluation of tree level MHV amplitudes by Cachazo-He-Yuan (CHY) formula, which naturally reproduce the Parke-Taylor and Hodges formula respectively for gauge and gravity. We also verify that they are supported only by one single solution to the scattering equation. In addition, we derive a new compact formula for tree level single trace MHV amplitudes for Einstein-Yang-Mills theory, which is equivalent to, but much simpler than the known Selivanov-Bern-De Freitas-Wong (SBDW) formula. It can be shown that other solutions do not contribute to the MHV amplitudes of Yang-Mills, gravity and Einstein-Yang-Mills theory. We further propose a method to characterize the solutions to the scattering equations using the rank of two discriminant matrices. In four dimensions, such a characterization can be used to understand the correspondence between the helicity configurations of external scattering particles and the solutions to the scattering equation.