Gauge dependence of the AdS instability problem
  Previous work on the AdS instability problem within the two-time framework (TTF) has found an "oscillating singularity" whose presence depends on the gauge choice. We give a physical interpretation of this singularity as a diverging redshift between the boundary and the center of AdS. This signals a genuine breakdown of the linearized gravity. One can also identify the diverging redshift through a back-reaction calculation purely in the boundary gauge, where the TTF result stays regular. 
Fotios V. Dimitrakopoulos, Ben Freivogel, Juan F. Pedraza and I-Sheng   Yang
hep-th gr-qc