ON SINGULARITIES OF SPHERICALLY SYMMETRICAL BACKGROUNDS IN STRING THEORY

We suggest that for singular rotationally invariant closed string backgrounds which need sources for their support at the origin (in particular, for special plane waves and fundamental strings) certain 'trivial' alpha'-corrections (which are usually ignored since in the absence of sources they can be eliminated by a field redefinition) may play an important role leading to the absence of singularities in the exact solutions. These corrections effectively regularize the source delta-function at the scale of root alpha'. We demonstrate that similar smearing of the singularity of the leading-order point-charge solution indeed takes place in the open string theory.