A Stringy Cloak for a Classical Singularity

We consider a class of 4D supersymmetric black hole solutions, arising fromstring theory compactifications, which classically have vanishing horizon areaand singular space-time geometry. String theory motivates the inclusion ofhigher derivative terms, which convert these singular classical solutions intoregular black holes with finite horizon area. In particular, the supersymmetricattractor equations imply that the central charge, which determines the radiusof the $AdS_2\times S^2$ near horizon geometry, acquires a non-vanishing valuedue to quantum effects. In this case quantum corrections to theBekenstein-Hawking relation between entropy and area are large. This is thefirst explicit example where stringy quantum gravity effects replace aclassical null singularity by a black hole with finite horizon area.Comment: 10 page