STRINGS IN COSMOLOGICAL SPACETIMES AND THEIR BACK-REACTION

TL;DR

This paper reviews the behavior of strings in curved spacetimes, especially cosmological models, and discusses recent progress in self-consistent string cosmologies with realistic matter and inflation.

Contribution

It provides a comprehensive review of string dynamics in cosmological backgrounds and introduces self-consistent solutions to Einstein equations with string matter.

Findings

String behavior in cosmological spacetimes is well understood.

Self-consistent string cosmological solutions exhibit realistic matter and radiation dominated eras.

Inflation within string theory frameworks is discussed.

Abstract

This is a short review on strings in curved spacetimes. We start by recalling the classical and quantum string behaviour in singular plane waves backgrounds. We then report on the string behaviour in cosmological spacetimes (FRW, de Sitter, power inflation) which is by now largerly understood. Recent progress on self-consistent solutions to the Einstein equations for string dominated universes is reviewed. The energy-momentum tensor for a gas of strings is considered as source of the spacetime geometry. The string equation of state is determined from the behaviour of the explicit string solutions. This yields a self-consistent cosmological solution exhibiting realistic matter dominated behaviour $ R \sim (T)^{2/3}\; $ for large times and radiation dominated behaviour $ R \sim (T)^{1/2}\; $ for early times. Inflation in the string theory context is discussed.