U-duality covariant m-theory cosmology.

manifestly U-duality covariant approach to M-theory cosmology is developed and applied to cosmologies in dimensions D = 4,5. Cosmological properties such as expansion powers and Hubble parameters turn out to be U-duality invariant in certain asymptotic regions. U-duality transformations acting on cosmological solutions, on the other hand, shift the transition time between two asymptotic regions and determine the details of the transition. Moreover, in D = 5, we show that U-duality can map expanding negative and positive branch solutions into each other. (C) 1998 Published by Elsevier Science B.V. All rights reserved.