The large $N_c$ limit of four-point functions in N=4 super-Yang-Mills   theory from anti-de Sitter Supergravity
  We compute the imaginary part of scalar four-point functions in the AdS/CFT correspondence relevant to N=4 super Yang-Mills theory. Unitarity of the AdS supergravity demands that the imaginary parts of the correlation functions factorize into products of lower-point functions. We include the exchange diagrams for scalars as well as gravitons and find explicit expressions for the imaginary parts of these correlators. In momentum space these expressions contain only rational functions and logarithms of the kinematic invariants, in such a manner that the correlator is not a free-field result. The simplicity of these results, however, indicate the possibility of additional symmetry structures in N=4 super Yang-Mills theory in the large $N_c$ limit at strong effective coupling. The complete expressions may be computed from the integral results derived here. 
Gordon Chalmers, Koenraad Schalm