The Cosmology of M-Theory and Type II Superstrings

TL;DR

This paper reviews cosmological solutions in type II superstrings and M-theory, focusing on non-zero Ramond backgrounds, compactifications, singularities, and U-duality effects on cosmological parameters.

Contribution

It provides new explicit examples of U-duality covariant M-theory cosmology and analyzes their properties in various compactification scenarios.

Findings

Explicit example of type IIA superstring cosmology constructed.

Analysis of U-duality effects on Hubble parameters and transition times.

Demonstration of U-duality covariance in a five-dimensional M-theory model.

Abstract

We review cosmological solutions of type II superstrings and M-theory, emphasizing the role of non-vanishing Ramond form backgrounds. Compactifications on flat and, more generally, maximally symmetric spatial subspaces are presented. We give a physical discussion of both inflating and subluminally expanding cosmological solutions of such theories and explore their singularity structure. An explicit example, in the context of the type IIA superstring, is constructed. We then analyze compactifications of M-theory on Ricci flat manifolds. The external part of U--duality and its relation to cosmological solutions is studied in the low energy theory. In particular, we investigate the behaviour of important cosmological properties, such as the Hubble parameters and the transition time between two asymptotic regions, under U-duality transformations. Motivated by Horava-Witten theory, we present an explicit example of manifestly U-duality covariant M--theory cosmology in a five-dimensional model resulting from compactification on a Calabi-Yau three-fold.