Superstring Cosmology

TL;DR

This paper reviews superstring cosmology, focusing on duality symmetries, effective actions, and cosmological models, including pre-big bang inflation and primordial perturbations, highlighting recent theoretical developments and future directions.

Contribution

It provides a comprehensive review of superstring cosmology, emphasizing duality symmetries, effective actions, and the derivation of various cosmological solutions within string theory.

Findings

Analysis of duality symmetries in string effective actions

Derivation of cosmological models with NS-NS and R-R fields

Discussion of pre-big bang inflation and primordial spectra

Abstract

Aspects of superstring cosmology are reviewed with an emphasis on the cosmological implications of duality symmetries in the theory. The string effective actions are summarized and toroidal compactification to four dimensions reviewed. Global symmetries that arise in the compactification are discussed and the duality relationships between the string effective actions are then highlighted. Higher-dimensional Kasner cosmologies are presented and interpreted in both string and Einstein frames, and then given in dimensionally reduced forms. String cosmologies containing both non-trivial Neveu-Schwarz/Neveu-Schwarz and Ramond-Ramond fields are derived by employing the global symmetries of the effective actions. Anisotropic and inhomogeneous cosmologies in four-dimensions are also developed. The review concludes with a detailed analysis of the pre-big bang inflationary scenario. The generation of primordial spectra of cosmological perturbations in such a scenario is discussed. Possible future directions offered in the Horava-Witten theory are outlined.