A CLASS OF NONSINGULAR GRAVI-DILATON BACKGROUNDS

We present a class of static, spherically symmetric, non-singular solu tions of the tree-level string effective action, truncated to first or der in alpha'. In the string frame the solutions approach asymptotical ly (as r --> 0 and r --> infinity) two different anti-de Sitter config urations, thus interpolating between two maximally symmetric states of different constant curvatures. The radial-dependent dilaton defines a string coupling which is everywhere finite, with a peak value that ca n be chosen arbitrarily small so as to neglect quantum-loop correction s. This example stresses the possible importance of finite-size alpha' corrections, typical of string theory, in avoiding space-time singula rities.