String theory and the arrow of time

Time-like linear dilaton triggers, at the classical level, the creation of closed folded strings at an instant. We show that in cosmology these instant folded strings induce negative pressure at no energy cost. Hence they seem to allow an era in which the energy density increases (decreases) while the universe is expanding (contracting). This and other aspects of instant folded strings suggest that they might shed new light on the origin of the arrow of time.