Black holes and D-branes

Black holes have an entropy proportional to the area of the horizon. The microscopic degrees of freedom that give rise to the entropy are not visible in the classical theory. String theory, a quantum theory of gravity, provides a microscopic quantum description of the thermodynamic properties of some extremal and near extremal charged black holes. The description uses properties of some string theory solitons called D-branes. In this description, Hawking radiation emerges as a simple perturbative process. The low energy dynamics of particle absorption and emission agrees in detail with the semiclassical analysis in the thermodynamic limit.