O(d,d)-invariance in inhomogeneous string cosmologies with perfect fluid

TL;DR

This paper extends O(d,d)-duality invariance to inhomogeneous string cosmologies with perfect fluids and demonstrates new dual solutions through explicit examples, broadening the understanding of duality in complex backgrounds.

Contribution

It generalizes O(d,d)-duality invariance from homogeneous to inhomogeneous cosmological backgrounds with perfect fluids, providing explicit duality transformations and novel solutions.

Findings

Extended duality invariance to inhomogeneous backgrounds

Explicit duality transformations in Einstein frame

New dual solutions not previously documented

Abstract

In the first part of the present paper, we show that O(d,d)-invariance usually known in a homogeneous cosmological background written in terms of proper time can be extended to backgrounds depending on one or several coordinates (which may be any space-like or time-like coordinate(s)). In all cases, the presence of a perfect fluid is taken into account and the equivalent duality transformation in Einstein frame is explicitly given. In the second part, we present several concrete applications to some four-dimensional metrics, including inhomogeneous ones, which illustrate the different duality transformations discussed in the first part. Note that most of the dual solutions given here do not seem to be known in the literature.