Closed inhomogeneous string cosmologies

Closed Inhomogeneous String Cosmologies

We present a general algorithm which permits to construct solutions in string cosmology for heterotic and type-IIB superstrings in four dimensions. Using a chain of transformations applied in sequence: conformal, T-duality and SL(2,R) rotations, along with the usual generating techniques associated to Geroch transformations in Einstein frame, we obtain solutions with all relevant low-energy rem...

Inhomogeneous String Cosmologies

We present exact inhomogeneous and anisotropic cosmological solutions of low-energy string theory containing dilaton and axion fields. The spacetime metric possesses cylindrical symmetry. The solutions describe ever-expanding universes with an initial curvature singularity and contain known homogeneous solutions as subcases. The asymptotic form of the solution near the initial singularity has a...

Asymptotic Behaviour of Inhomogeneous String Cosmologies

The asymptotic behaviour at late times of inhomogeneous axion-dilaton cosmologies is investigated. The space-times considered here admit two abelian space-like Killing vectors. These space-times evolve towards an anisotropic universe containing gravitational radiation. Furthermore, a peeling-off behaviour of the Weyl tensor and the antisymmetric tensor field strength is found. The relation to t...

Anisotropic and Inhomogeneous Cosmologies

Scalar Field Inhomogeneous Cosmologies

Some exact solutions for the Einstein eld equations corresponding to inhomogeneous G2 cosmologies with an exponential-potential scalar eld which generalize solutions obtained previously are considered. Several particular cases are studied and the properties related to generalized in ation and asymptotic behaviour of the models are discussed.