Construction of nonsingular cosmological solutions in string theories

Abstract

We study nonsingular cosmological scenarios in a general $D$-dimensional string effective action of the dilaton-modulus-axion system in the presence of the matter source. In the standard dilatonic Brans-Dicke parameter ($\omega =-1$) with radiation, we analytically obtain singularity-free bouncing solutions where the universe starts out in a state with a finite curvature and evolves toward the weakly coupled regime. We apply this analytic method to the string-gas cosmology including the massive state in addition to the leading massless state (radiation), with and without the axion. We numerically find bouncing solutions which asymptotically approach an almost radiation-dominant universe with a decreasing curvature irrespective of the presence of the axion, implying that inclusion of the matter source is crucial for the existence of such solutions for $\omega =-1$. In the theories with $\omega \ne -1$, it is possible to obtain complete regular bouncing solutions with a finite dilaton and curvature in both past and future asymptotics for the general dimension, $D$. We also discuss the case where dilatonic higher-order corrections are involved to the tree-level effective action and demonstrate that the presence of axion/modulus fields and the matter source does not significantly affect the dynamics of the dilaton-driven inflation and the subsequent graceful exit.

27 pages, 6 eps figures

Cited by in corpus (25)

• Dynamics of dark energy
• Dilatonic ghost condensate as dark energy
• Coupled dark energy: Towards a general description of the dynamics
• The fate of (phantom) dark energy universe with string curvature corrections
• Dark energy and cosmological solutions in second-order string gravity
• Avoidance of future singularities in loop quantum cosmology
• Big Crunch Avoidance in k = 1 Semi-Classical Loop Quantum Cosmology
• String-inspired cosmology: Late time transition from scaling matter era to dark energy universe caused by a Gauss-Bonnet coupling
• Aspects of String-Gas Cosmology at Finite Temperature
• The Big Bounce in Rainbow Universe
• Bouncing alternatives to inflation
• UV stable, Lorentz-violating dark energy with transient phantom era
• Patch dualities and remarks on nonstandard cosmologies
• Late-time dynamics of brane gas cosmology
• Multiple kinetic k-essence, phantom barrier crossing and stability
• Late cosmology of brane gases with a two-form field
• Stable super-inflating cosmological solutions in f(R)-gravity
• Observational signatures of a non-singular bouncing cosmology
• Towards a Stringy Resolution of the Cosmological Singularity
• String creation in cosmologies with a varying dilaton
• Study of symmetry in F(R) theory of gravity
• Inaccessible Singularities in Toral Cosmology
• Universe scenarios from loop quantum cosmology
• Asymptotic solutions in f(R)-gravity
• Falsifying Tree Level String Motivated Bouncing Cosmologies