Dynamics of a wavy plane Wilson surface observable from AdS-CFT   correspondence
  Guided by the paper hep-th/0002106 by Polyakov and Rychkov, we compute the second variational derivative of a wavy plane Wilson surface observable, to find that a necessary condition for a proposed surface equation to be satisfied in the large $N$ limit is that we are in the critical dimension D=6. 
Andreas Gustavsson