DUALITY WITHOUT SUPERSYMMETRY - THE CASE OF THE SO(16)XSO(16) STRING

We extend strong/weak coupling duality to string theories without spac etime supersymmetry, and focus on the case of the unique ten-dimension al, nonsupersymmetric, tachyon-free SO(16)X SO(16) heterotic string. W e construct a tachyon-free heterotic string model that interpolates sm oothly between this string and the ten-dimensional supersymmetric SO(3 2) heterotic string, and we construct a dual for this interpolating mo del. We find that the perturbative massless states of our dual theorie s precisely match within a certain range of the interpolation. Further evidence for this proposed duality comes from a calculation of the on e-loop cosmological constant in both theories, as well as the presence of a soliton in the dual theory. This is therefore the first known du ality relation between nonsupersymmetric tachyon-free string theories. Using this duality, we then investigate the perturbative and nonpertu rbative stability of the SO(16)X SO(16) string, and present a conjectu re concerning its ultimate fate. (C) 1997 Elsevier Science B.V.