AN EXACT COSMOLOGICAL SOLUTION TO STRING THEORY

TL;DR

This paper constructs an exact four-dimensional cosmological solution in string theory using a non-semisimple Lie group WZW model, providing insights into string propagation in an expanding-contracting universe with specific background fields.

Contribution

It introduces a novel exact cosmological solution in string theory derived from an ungauged WZW model based on a non-semisimple Lie group, with a detailed string spectrum analysis.

Findings

Exact homogeneous anisotropic cosmological solution in string theory

Representation of current algebra using free bosons and parafermions

Analysis of string spectrum in the constructed background

Abstract

A homogeneous anisotropic four dimensional spacetime with Lorentzian signature is constructed from an ungauged WZW model based on a non-semisimple Lie group. The associated non-linear $\sigma $-model describes string propagation in an expanding-contracting universe with antisymmetric tensor and dilaton backgrounds. The current algebra of SL(2,R)$\times $R is constructed in terms of two free boson fields and two generalized parafermions, or four free bosons with background charge. This representation is used to study the string spectrum in the cosmological background.