<B>Faculty Candidate Seminar</B><br><i>Scattering Amplitudes in Gravity and Gauge Theory</i>

Speaker: Dr. Henriette Elvang (Institute for Advanced Study, Princeton)

The unification of general relativity and quantum mechanics has long been an enticing, yet challenging, subject in theoretical physics. One difficulty is that graviton scattering amplitudes suffer from problematic divergences. However, it was recently proposed that all these divergences might cancel in a certain supersymmetric theory of gravity. Such surprising cancellations are currently being investigated through direct calculations of scattering amplitudes in supergravity. In my talk I will review these ideas and I will describe how new "on-shell methods" let us construct scattering amplitudes efficiently from a set of very simple building blocks. The techniques--which also apply to processes relevant for particle physics experiments --- reveal a structure much simpler than what is expected based on the standard Lagrangian formulations. This simplicity may guide us towards a new approach to quantum field theory.