paper

A New Cosmological Scenario in String Theory

arXiv:hep-th/0203031 · doi:10.1103/PhysRevD.66.066001

Abstract

We consider new cosmological solutions with a collapsing, an intermediate and an expanding phase. The boundary between the expanding (collapsing) phase and the intermediate phase is seen by comoving observers as a cosmological past (future) horizon. The solutions are naturally embedded in string and M-theory. In the particular case of a two-dimensional cosmology, space-time is flat with an identification under boost and translation transformations. We consider the corresponding string theory orbifold and calculate the modular invariant one-loop partition function. In this case there is a strong parallel with the BTZ black hole. The higher dimensional cosmologies have a time-like curvature singularity in the intermediate region. In some cases the string coupling can be made small throughout all of space-time but string corrections become important at the singularity. This happens where string winding modes become light which could resolve the singularity. The new proposed space-time casual structure could have implications for cosmology, independently of string theory.

28 pages, 3 figures; v2: Added new subsection relating two-dimensional model to BTZ black hole, typos corrected and references added; v3: minor corrections, PRD version

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