at the chiral point with Brown–Henneaux boundary conditions). It was argued in [@Castro:2011ui] that this is an artifact of the ignorance of the AdS heat kernel to the existence of null modes and negative energy states, which should be excluded from the spectrum of physical modes. It was suggested to calculate a different heat kernel, one that would not include log-modes or null states. While this seems to be a formidable, if challenging, task we will take a different approach.

It is hard to impose boundary conditions on the heat kernel, but it is very simple to do so for quasi-normal modes: choosing the ansatz for the solution determines the boundary conditions the mode will fulfill. Here we do not refer to the boundary conditions at the black hole horizon, which need be specified for quasi-normal modes, but to the asymptotic behavior of the mode.

An analysis like the one we carried out in section \[sec2\] is usually around thermal AdS, see e.g. [@Giombi:2008vd]. This is not a black hole background. However, the approach of [@Denef:2009kn] also holds for non black hole backgrounds, quasi-normal modes being replaced by normal modes [@Denef:2009kn]. On the other hand, the results obtained in section 