Can String Theory Avoid Cosmological Singularities?

TL;DR

This paper investigates whether string theory can prevent cosmological singularities by analyzing the universe's evolution with matter and solitonic branes, finding conditions under which singularities are avoided.

Contribution

It demonstrates that singularity-free cosmological evolution is possible in string theory when certain phases involve solitonic branes or specific matter conditions.

Findings

Universe evolution becomes non-singular with solitonic p-branes

Strong coupling phases can resolve singularities

Certain matter conditions lead to singularity avoidance

Abstract

We consider the effective action for strings and describe in detail the evolution of a four dimensional homogeneous isotropic universe with matter included. We find that the evolution, which is singular in general, becomes singularity free if during certain Phase of the evolution, when the scale factor increases and the effective string coupling becomes strong, the universe is dominated by solitonic p-branes, p = 0 and/or - 1, or by `matter' for which $(pressure) \le - \frac{1}{\sqrt{3}} (density)$. The mechanism in the case of branes is reminiscent of the recently discovered field theory mechanism where heavy states become light and resolve the moduli space singularities.