We point out that the recently proposed model of a flat four-dimensional universe with accelerated expansion in string or M theory is a special case of time-dependent solutions that the author found under the name of spacelike ($S$) 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.

• Received 31 March 2003

DOI:https://doi.org/10.1103/PhysRevLett.91.061303