Spectrum of quantum black holes and quasinormal modes

The spectrum of multiple level transitions of a quantum black hole is considered and the linewidths calculated. Initial evidence is found for these higher order transitions in the spectrum of quasinormal modes for Schwarzschild and Kerr black holes, further bolstering the idea that there exists a correspondence principle between quantum transitions and classical ``ringing modes.'' Several puzzles are noted, including a fine-tuning problem between the linewidth and level degeneracy. A more general explanation is provided for why setting the Immirzi parameter of loop quantum gravity from the black hole spectrum necessarily gives the correct value for the black hole entropy.