The Perturbation Spectrum of Black Holes in N=8 Supergravity

The near horizon geometry of four-dimensional black holes in the dilute gas regime is AdS_3 x S^2, and the global symmetry group is SU(2) x USp(6). This is exploited to calculate their perturbation spectrum using group theoretical methods. The result is interpreted in terms of three extreme M5-branes, orthogonally intersecting over a common string. We also consider N=8 black holes in five dimensions, and compute the spectrum by explicit decoupling of the equations of motion, extending recent work on N=4 black holes. This result is interpreted in terms of D1- and D5-branes that are wrapped on a small four-torus. The spectra are compared with string theory.