Quasinormal modes for massless topological black holes
  An exact expression for the quasinormal modes of scalar perturbations on a massless topological black hole in four and higher dimensions is presented. The massive scalar field is nonminimally coupled to the curvature, and the horizon geometry is assumed to have a negative constant curvature. 
Rodrigo Aros, Cristian Martinez, Ricardo Troncoso and Jorge Zanelli