Horizon States for AdS Black Holes
  We study the time-independent modes of a massless scalar field in various black hole backgrounds, and show that for these black holes, the time-independent mode is localised at the horizon. A similar analysis is done for time-independent equilibrium modes of the five dimensional plane AdS black hole. A self-adjointness analysis of this problem reveals that in addition to the modes corresponding to the usual glueball states, there is a discrete infinity of other equilibrium modes with imaginary mass for the glueball. We suggest these modes may be related to a Savvidy-Nielsen-Olesen-like vacuum instability in QCD. 
T.R. Govindarajan, V. Suneeta and S. Vaidya