Duality invariance and cosmological dynamics

TL;DR

This paper explores a duality transformation in cosmology that links expanding and contracting models, identifying a duality-invariant description applicable to various cosmic media and perturbations.

Contribution

It introduces a duality invariance principle for cosmological models, extending it to perturbations and applying it to multiple cosmic components and scalar field models.

Findings

Duality transformation relates expanding and contracting cosmologies.

The duality invariance applies to matter, radiation, and scalar fields.

Adiabatic pressure perturbations remain invariant under duality.

Abstract

A duality transformation that interrelates expanding and contracting cosmological models is shown to single out a duality invariant, interacting two-component description of any irrotational, geodesic and shearfree cosmic medium with vanishing three curvature scalar. We apply this feature to a system of matter and radiation, to a mixture of dark matter and dark energy, to minimal and conformal scalar fields, and to an enlarged Chaplygin gas model of the cosmic substratum. We extend the concept of duality transformations to cosmological perturbations and demonstrate the invariance of adiabatic pressure perturbations under these transformations.