Scalar perturbations of higher dimensional rotating and ultra-spinning   black holes
  We investigate the stability of higher dimensional rotating black holes against scalar perturbations. In particular, we make a thorough numerical and analytical analysis of six-dimensional black holes, not only in the low rotation regime but in the high rotation regime as well. Our results suggest that higher dimensional Kerr black holes are stable against scalar perturbations, even in the ultra-spinning regime. 
Vitor Cardoso, George Siopsis, Shijun Yoshida