The all-order structure of long-distance singularities for massless gauge theories

by Lorenzo Magnea (Unknown)

Monday 22 Mar 2010, 14:00 → 15:00 Europe/Zurich

Cubotron 727 (EPFL)

Infrared and collinear singularities in perturbation theory encode information on the long-range interactions of gauge fields, and are responsible for large corrections to physical cross sections that are important for collider phenomenology. I will review recent significant progress in our understanding of these singularities. For planar amplitudes, we now know that all singularities are generated by just three anomalous dimensions, which can be defined non-perturbatively in terms of Wilson lines and local operators. For N=4 Super Yang-Mills theory, the resulting exponentiation matches strong coupling calculations performed using the AdS/CFT correspondence, and points to possible exact results. Beyond the planar limit, the special properties of light-like Wilson lines severely constrain the form of the soft anomalous dimension matrices that govern exponentiation. A simple sum-over-dipoles formula emerges, which is conjectured to encode all soft singularities for any massless gauge theory. Suggested introductory readings: Phys. Rev. D42 p. 4222 (1990), arXiv:0901.1091, arXiv:0910.3653