Spacetime singularity and AdS/CFT for time dependent background

The work [C. S. Chu and P. M. Ho, hep-th/0602054] on time-dependent AdS/CFT correspondence is reviewed. The supergravity solutions we construct are supersymmetric pp-waves on AdS and may have null singularity in the bulk. The dual gauge theory is also constructed explicitly and is given by a time-dependent supersymmetric Yang-Mills theory. We find that the two-point function computed by using duality is different from that by doing a direct field theory computation. In particular the spacetime singularity is not seen in the gauge description, suggesting that the spacetime singularity may be resolved in quantum gravity.