Horizon instability of massless scalar perturbations of an extreme Reissner-Nordstr\"om-AdS black hole

We study the stability of extreme Reissner-Nordstr\"om-AdS black hole under massless scalar perturbations. We show that the perturbation on the horizon of the extreme Reissner-Nordstr\"om-AdS black hole experiences a power-law decay, instead of an exponential decay as observed in the nonextreme AdS black hole. On the horizon of the extreme Reissner-Nordstr\"om-AdS black hole, the blow up happens at lower order derivative of the scalar field compared with that of the extreme Reissner-Nordstr\"om black hole, which shows that extreme AdS black holes tend to instability in comparison to black holes in asymptotic flat space-times.