TH String Theory Seminar

# Yangian invariants, on-shell graphs and deformations

## by Johannes Broedel

Tuesday, 18 February 2014 from to (Europe/Zurich)
at CERN ( 4-3-006 - TH Conference Room )
 Description On-shell graphs are a convenient way of representing Yangian invariants which serve as building blocks for amplitudes in N=4 super-Yang-Mills theory. Maintaining Yangian invariance, one can deform these on-shell graphs by shifting the helicities of the external legs. In the first part of the talk, I will discuss the construction of deformed on-shell graphs as well as their relation to scattering amplitudes and the BCFW recursion relation. In addition, I will comment on the possibility of using the deformation parameter as a regulator for the one-loop four-point amplitude. In a second part, I am going to review an algebraic formulation of scattering amplitudes recently suggested by Chicherin, Derkachov and Kirschner. In this language, (deformed) amplitudes are generated by repeatedly acting with certain R-operators on a vacuum and Yangian invariance is ensured by demanding the resulting objects to be eigenstates of a monodromy matrix. I will discuss advantages and extensions of this formalism, relate it to the previous one and will show that the constraints on possible deformations of scattering amplitudes are equivalent. Organised by James Drummond