Dilaton-driven brane inflation in type IIB string theory

TL;DR

This paper investigates the cosmological evolution of a three-brane within type IIB string theory backgrounds, deriving equations that describe universe expansion and highlighting effects of dilaton and axion fields on cosmological dynamics.

Contribution

It derives Friedman-like equations for brane cosmology in type IIB backgrounds with nontrivial dilaton profiles, analyzing the impact of axion fields on universe recollapse.

Findings

Effective density diverges near singularity, indicating initial singularity.

Presence of axion accelerates universe recollapse.

Cosmological evolution resembles matter-dominated universe.

Abstract

We consider the cosmological evolution of the three-brane in the background of type IIB string theory. For two different backgrounds which give nontrivial dilaton profile we have derived the Friedman-like equations. These give the cosmological evolution which is similar to the one by matter density on the universe brane. The effective density blows up as we move towards the singularity showing the initial singularity problem. The analysis shows that when there is axion field in the ambient space the recollapsing of the universe occurs faster compared with the case without axion field.