Entropy of 4D black holes and the enhancon - art. no. 104004

We consider the physics of enhancons as applied to four dimensional black h oles which are constructed by wrapping both D-branes and NS-branes on K3. A s was recently shown for the five dimensional black holes, the enhangon is crucial in maintaining consistency with the second law of thermodynamics. T his is true for both the D-brane and NS-brane sectors of these black holes. In particular NS5-branes in both type IIA and IIB string theory are found to exhibit enhangon physics when wrapped on a K3 manifold.