Symmetries for generating string cosmologies

TL;DR

This paper explores the symmetry properties of the low-energy effective action of type IIB superstring theory, focusing on how these symmetries can generate and analyze four-dimensional cosmological solutions with non-trivial fields.

Contribution

It demonstrates that the compactified effective action can be formulated as a non-linear sigma model invariant under SL(3,R) and SL(2,R) symmetries, aiding the study of cosmological solutions.

Findings

Identifies SL(3,R) as a symmetry of the truncated effective action.

Shows how SL(2,R) and Z2 symmetries relate to solution generation.

Analyzes spatially homogeneous cosmological solutions with Ramond-Ramond fields.

Abstract

We discuss the symmetry properties of the low-energy effective action of the type IIB superstring that may be employed to derive four-dimensional solutions. A truncated effective action, compactified on a six-torus, but including both Neveu/Schwarz-Neveu/Schwarz and Ramond-Ramond field strengths, can be expressed as a non-linear sigma model which is invariant under global SL(3,R) transformations. This group contains as a sub-group the SL(2,R) symmetry of the ten-dimensional theory and a discrete Z2 reflection symmetry which leads to a further SL(2,R) sub-group. The symmetries are employed to analyse a general class of spatially homogeneous cosmological solutions with non-trivial Ramond-Ramond fields.