Pulling the straps of polygons
  Using the Operator Product Expansion for Wilson loops we derive a simple formula giving the discontinuities of the two loop result in terms of the one loop answer. We also argue that the knowledge of these discontinuities should be enough to fix the full two loop answer, for a general number of sides. We work this out explicitly for the case of the hexagon and rederive the known result. 
Davide Gaiotto, Juan Maldacena, Amit Sever, Pedro Vieira
hep-th hep-ph