On the proposed AdS dual of the critical O(N) sigma model for any   dimension 2<d<4
  We evaluate the 4-point function of the auxiliary field in the critical O(N) sigma model at O(1/N) and show that it describes the exchange of tensor currents of arbitrary even rank l>0. These are dual to tensor gauge fields of the same rank in the AdS theory, which supports the recent hypothesis of Klebanov and Polyakov. Their couplings to two auxiliary fields are also derived. 
T. Leonhardt, A. Meziane, W. Ruehl