Inhomogeneous M-Theory Cosmologies

TL;DR

This paper investigates a class of inhomogeneous and anisotropic G_2 M-theory cosmological models, revealing their evolution from inhomogeneous, negatively curved states to homogeneous, flat solutions, with early inhomogeneities playing a significant role.

Contribution

It introduces a new class of separable G_2 M-theory cosmological models and analyzes their qualitative evolution, highlighting the importance of early-time inhomogeneities.

Findings

Models evolve from inhomogeneous, negatively curved states to flat, homogeneous solutions.

Early inhomogeneities are dynamically significant, influencing the evolution.

Late-time behavior matches previously studied spatially homogeneous models.

Abstract

We study a class of inhomogeneous and anisotropic $G_2$ string cosmological models. In the case of separable $G_2$ models we show that the governing equations reduce to a system of ordinary differential equations. We focus on a class of separable $G_2$ M-theory cosmological models, and study their qualitative behaviour (a class of models with time-reversed dynamics is also possible). We find that generically these inhomogeneous M-theory cosmologies evolve from a spatially inhomogeneous and negatively curved model with a non-trivial form field towards spatially flat and spatially homogeneous dilaton-moduli-vacuum solutions with trivial form--fields. The late time behaviour is the same as that of spatially homogeneous models previously studied. However, the inhomogeneities are not dynamically insignificant at early times in these models.