Accelerating cosmologies from M/String theory compactifications

TL;DR

This paper demonstrates that certain M/String theory compactifications involving dilaton and form fields can produce flat, accelerating 4D universes, providing a theoretical framework for cosmological acceleration within string theory.

Contribution

It shows that solutions with specific internal geometries and field configurations can yield accelerating cosmologies from M/String theory compactifications, extending previous models.

Findings

Accelerating cosmologies are achievable with hyperbolic and flat internal spaces.

Solutions correspond to space-like two branes (S2-branes) in string theory.

The model includes cases with vanishing dilaton and general field strengths.

Abstract

We point out that the solution of $(4+n)$-dimensional gravity coupled to the dilaton and an $n$-form field strength can give rise to a flat 4-dimensional universe (with a scale factor) of the type proposed recently under time dependent compactifications. The compact internal spaces could be hyperbolic, flat or spherical and the solution is identical to the space-like two brane or S2-brane. As has been shown previously for SM2 solution with a fixed field strength we show that for $n=7$ (where the dilaton is vanishing and with a general field strength), 6 the corresponding SM2 and SD2 solutions can give accelerating cosmologies in Einstein frame for both hyperbolic and flat internal spaces, thereby meeting the challenge of obtaining such a solution from M/String theory compactifications.