STRONG WEAK COUPLING DUALITY RELATIONS FOR NONSUPERSYMMETRIC STRING THEORIES/

Both the supersymmetric SO(32) and E-8 x E-8 heterotic strings in ten dimensions have known strong-coupling duals. However, it has not been known whether there also exist strong-coupling duals for the non-super symmetric heterotic strings in ten dimensions. In this paper, we const ruct explicit open-string duals for the circle compactifications of se veral of these non-supersymmetric theories, among them the tachyon-fre e SO(16) x SO(16) string. Our method involves the construction of hete rotic and open-string interpolating models that continuously connect n on-supersymmetric strings to supersymmetric strings. We find that our non-supersymmetric dual theories have exactly the same massless spectr a as their heterotic counterparts within a certain range of our interp olations. We also develop a novel method for analyzing the solitons of non-supersymmetric open-string theories, and find that the solitons o f our dual theories also agree with their heterotic counterparts. Thes e are therefore the first known examples of strong/weak coupling duali ty relations between non-supersymmetric, tachyon-free string theories. Finally, the existence of these strong-coupling duals allows us to ex amine the non-perturbative stability of these strings, and we propose a phase diagram for the behavior of these strings as a function of cou pling and radius. (C) 1998 Elsevier Science B.V.