A COSMOLOGICAL INTERPRETATION OF DUALITY

We study the cosmological meaning of duality symmetry by considering a two dimensional model of string cosmology. We find that as seen by an internal observer in this universe, the scale factor rebounds at the self-dual length. This rebound is a consequence of the adiabatic expan sion. Furthermore, in this situation there are four mathematically dif ferent scenarios which describe physically equivalent universes which are in fact undistinguishable. We also stress that R-duality suffices to prove that all the possible evolutions present a maximun temperatur e.