TIME-LIKE DUALITY

Several stationary solutions of the low energy string equations are du alized with respect to their timelike symmetry. Many of the duals have simple physical interpretations. Those of the nonextremal three-dimen sional black hole and black string ace negative mass black strings. Th e extremal cases of these, and extremal higher-dimensional black strin gs also, give negative energy plane-fronted waves. In fact, all of the duals of positive mass solutions that will be considered here have no npositive energies, but an argument is given which suggests that this is not true in general.