Two fluid acoustic modes and inhomogeneous cosmologies

Anisotropic and Inhomogeneous Cosmologies

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...

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.

Inhomogeneous M-Theory Cosmologies

Abstract We study a class of inhomogeneous and anisotropic G2 string cosmological models. In the case of separable G2 models we show that the governing equations reduce to a system of ordinary differential equations. We focus on a class of separable G2 M-theory cosmological models, and study their qualitative behaviour (a class of models with time-reversed dynamics is also possible). We find th...

Averaging inhomogeneous Newtonian cosmologies

Idealizing matter as a pressureless fluid and representing its motion by a peculiar-velocity field superimposed on a homogeneous and isotropic Hubble expansion, we apply (Lagrangian) spatial averaging on an arbitrary domain D to the (nonlinear) equations of Newtonian cosmology and derive an exact, general equation for the evolution of the (domain dependent) scale factor aD (t). We consider the ...