Cross-Order Relations in N=4 Supersymmetric Gauge Theories
  The anti-de Sitter/conformal field theory duality conjecture raises the question of how the perturbative expansion in the conformal field theory can resum to a simple function. We exhibit a relation between the one-loop and two-loop amplitudes whose generalization to higher-point and higher-loop amplitudes would answer this question. We also provide evidence for the first of these generalizations. 
C. Anastasiou, Z. Bern, L. J. Dixon, D. A. Kosower