Cosmological String Backgrounds from Gauged WZW Models

TL;DR

This paper explores how gauged WZW models can produce cosmological string backgrounds, including expanding universes, depending on algebraic parameters, expanding the understanding of string theory solutions.

Contribution

It introduces new cosmological string backgrounds derived from gauged WZW models, linking algebraic levels to cosmological solutions.

Findings

Gauged WZW models can produce cosmological backgrounds.

The sign of the Kac-Moody level determines the background type.

New expanding universe solutions are identified.

Abstract

We discuss the four-dimensional target-space interpretation of bosonic strings based on gauged WZW models, in particular of those based on the non-compact coset space $SL(2,{\bf R})\times SO(1,1)^2 /SO(1,1)$. We show that these theories lead, apart from the recently broadly discussed black-hole type of backgrounds, to cosmological string backgrounds, such as an expanding Universe. Which of the two cases is realized depends on the sign of the level of the corresponding Kac-Moody algebra. We discuss various aspects of these new cosmological string backgrounds.