A Resolution of the Cosmological Singularity in String Theory

Abstract

In the standard cosmological models, a space-like big-bang singularity is present in the past. The existence of an initial singularity is, to a large extent, independent of the model, and in fact one can show that, under general assumptions, a singularity in the cosmological past is inevitable (Hawking and Ellis, 1973). Despite these problems, the standard cosmological models (far) below the Planck scale are extremely successful in explaining the present experimental data. Attempts to solve the cosmological singularity problem lead to the pre big-bang scenario conjecture (G. Veneziano), motivated by the existence of a minimum distance in string theory. However, either the exact string backgrounds are not realistic (Kiritsis and Kounnas), or they show time-like singularities whose nature has remained unclear (Kounnas and Lust, 1992; Grojean et al., 2001).