CONJECTURES ON NONLOCAL EFFECTS IN STRING BLACK-HOLES

We consider the modifications to general relativity by the non-local (classical and quantum) string effects for the case of a D-dimensional Schwarzschild black hole. The classical non-local effects do not alter the spacetime topology (the horizon remains unshifted, at least perturbatively). We suggest a simple analytic continuation of the perturbative result into the non-perturbative domain, which eliminates the black hole singularity at the origin and yields an ultraviolet-finite theory of quantum gravity. We investigate the quantum non-local effects (including massive modes) and argue that the inclusion of these back reactions resolves the problem of the thermal spectrum in the semiclassical approach of field quantization in a black hole background, through the bootstrap condition. The density of states for both the quantum and thermal interpretation of the WKB formula are finally shown to differ quantitatively when including the non-local effects. (C) 1995 Academic Press, Inc.