Accelerating Cosmologies from S-Branes

Abstract

We point out that the recently proposed model of a flat 4-dimensional universe with accelerated expansion in string/M-theory is a special case of time-dependent solutions that the author found under the name of ``S-branes.'' We also show that similar accelerating models can be obtained from S-branes if the internal space is chosen to be hyperbolic or flat spaces.

8 pages, 4 figures, comments added, a typo corrected, final version to appear in Phys. Rev. Lett