#### Cross-order Integral Relations from Maximal Cuts

- Event time: 2:00pm
- Event date: 18th September 2014
- Speaker: Kasper Larsen (ETH Zurich)
- Location: Higgs Centre Seminar Room, James Clerk Maxwell Building (JCMB) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB

### Event details

In this talk I will review the status of maximal unitarity at two loops, a new framework for computing two-loop amplitudes based on unitarity rather than Feynman diagrams. In this approach, the two-loop amplitude is first expanded in a basis of integrals. The expansion coefficients are then determined by applying generalized unitarity cuts. We find explicit formulas for the integral coefficients as products of tree-level amplitudes integrated over specific contours in the complex plane, thus allowing the construction of the two-loop amplitude from appropriately defined tree amplitudes. The validity of this method extends to all four-dimensional gauge theories, in particular QCD. Next I will discuss how the sharing of leading singularities between loop integrals exhibits consistency of maximal cuts with the KLN theorem, and furthermore how this sharing can be used to infer integral identities such as the ABDK/BDS identity.

The Particle Physics Theory seminar is a weekly series of talks reflecting the diverse interests of the group. Topics include analytic and numerical calculations based on the Standard Model of elementary particle physics, theories exploring new physics, as well as more formal developments in gauge theories and gravity..