Holographic cubic vertex in the pp-wave
  We revisit the cubic interaction of IIB string theory in the maximally supersymmetric pp-wave background. In the supergravity limit, we show that detailed comparison with AdS supergravity determine the vertex completely. Extension of this supergravity vertex to the full string theory leads to a new cubic vertex that combines the previous proposals and contains additional terms. We give an alternative derivation of the holographic duality map in supergravity, first found by Dobashi and Yoneya (hep-th/0406225) and show that our new vertex is consistent with it. We compare some non-BPS amplitudes (including impurity non-preserving ones) with the corresponding field theory correlators, and discuss what they imply for the stringy generalization of the duality map. We also notice that our vertex realizes the U(1)_Y symmetry linearly, and propose a similar modification for the flat space vertex. 
Sangmin Lee and Rodolfo Russo