Hidden Simplicity of Gauge Theory Amplitudes

Understand

These notes were given as lectures at the CERN Winter School on Supergravity, Strings and Gauge Theory 2010.

• We describe the structure of scattering amplitudes in gauge theories, focussing on the maximally supersymmetric theory to highlight the hidden symmetries which appear.
• Using the BCFW recursion relations we solve for the tree-level S-matrix in N=4 super Yang-Mills theory, and describe how it produces a sum of invariants of a large symmetry algebra.
• We review amplitudes in the planar theory beyond tree-level, describing the connection between amplitudes and Wilson loops, and discuss the implications of the hidden symmetries.