Magnetic Black Holes in String Theory

We discuss the form of the string-loop-corrected effective action and the loop-corrected solutions of the equations of motion. At the string-tree level, a solution we consider is the extremal magnetic black hole, in which case the tree-level effective gauge couplings decrease at small r, and in this region string-loop corrections to the gauge couplings become important. The effective 4D theory is the N=2 supergravity interacting with matter. Using the N=2 structure of the theory, we calculate the loop corrections to the effective action and solve the loop-corrected equations of motion. In the resulting perturbative solution for the metric, singularity at the origin is smeared by quantum effects.