Scattering amplitudes play a pivotal role in quantum field theory as they are used to extract experimental predictions from theory. In order to explain the experimental data from the Large Hadron Collider (Cern), for instance, it is crucial to set up efficient ways to compute scattering cross-sections which then serve as a cross-check on the existing standard model of particle physics. There has been some remarkable work over the past few years that has improved both our understanding as well as our ability to calculate scattering amplitudes in gauge theories and, more recently, in gravity theories. These have led to a new perspective on scattering amplitudes in which underlying symmetries play a central role in solving for the amplitudes while conventional starting points - such as the Lagrangian - emerge as derived or secondary concepts. The most impressive results have been obtained for supersymmetric gauge theories, for which analytic computations are available for tree and many lo...
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