Universal low-energy dynamics for rotating black holes

Fundamental string theory has been used to show that low-energy excitations of certain black holes are described by a two-dimensional conformal field theory. This picture has been found to be extremely robust. In this paper it is argued that many essential features of the low-energy effective theory can be inferred directly from a semiclassical analysis of the general Kerr-Newman solution of supersymmetric four-dimensional Einstein-Maxwell gravity, without using string theory. We consider the absorption and emission of scalars with orbital angular momentum, which provide a sensitive probe of the black hole. We find that the semiclassical emission rates—including super-radiant emission and greybody factors—for such scalars agree in striking detail with those computed in the effective conformal field theory, in both four and five dimensions. Also the value of the quantum mass gap to the lowest-lying excitation of a charge-$Q$ black hole, $E_{\mathrm{gap}}{=1/8Q}^3$ in Planck units, can be derived without knowledge of fundamental string theory.