Closed string tachyon: inflation and cosmological collapse

Abstract

Starting with a compactification of critical bosonic string theory on an internal space with constant curvature, we look for conditions upon which an assumed closed string tachyon potential drives an inflationary Universe to collapse as the tachyon reaches the minimum of the potential. We find that all these features are possible in a scenario in which the internal manifold is negatively curved with a constant volume. We restrict our study to the case in which the scale factor and the dilaton are not dynamically coupled. Near to the minima of the potential the dilaton slows down to a null or constant velocity while rolling towards strong values on a dynamical string metric. Finally, some comments are addressed about the existence of similar cosmological features in alternative tachyonic potentials. Communicated by P R L V Moniz