Discontinuities in Scalar Perturbations of Topological Black Holes
  We study the perturbative behaviour of topological black holes. We calculate both analytically and numerically the quasi-normal modes of scalar perturbations. In the case of small black holes we find discontinuities of the quasi-normal modes spectrum at the critical temperature and we argue that this is evidence of a second-order phase transition. 
George Koutsoumbas, Eleftherios Papantonopoulos and George Siopsis