Evolution of perturbations in distinct classes of canonical scalar field models of dark energy

TL;DR

This paper investigates how dark energy perturbations evolve in canonical scalar field models, specifically in thawing and freezing classes, highlighting their distinct impacts on matter perturbations and the ISW effect.

Contribution

The study provides a detailed analysis of the evolution of dark energy perturbations in different scalar field models, emphasizing their observational differences from the cosmological constant.

Findings

Dark energy perturbations differ significantly between freezing and thawing models.

Matter perturbations in freezing models deviate early, unlike in thawing models.

Differences in perturbation evolution can help distinguish dark energy models via ISW effect.

Abstract

Dark energy must cluster in order to be consistent with the equivalence principle. The background evolution can be effectively modelled by either a scalar field or by a barotropic fluid.The fluid model can be used to emulate perturbations in a scalar field model of dark energy, though this model breaks down at large scales. In this paper we study evolution of dark energy perturbations in canonical scalar field models: the classes of thawing and freezing models.The dark energy equation of state evolves differently in these classes.In freezing models, the equation of state deviates from that of a cosmological constant at early times.For thawing models, the dark energy equation of state remains near that of the cosmological constant at early times and begins to deviate from it only at late times.Since the dark energy equation of state evolves differently in these classes,the dark energy perturbations too evolve differently. In freezing models, since the equation of state deviates from that of a cosmological constant at early times, there is a significant difference in evolution of matter perturbations from those in the cosmological constant model.In comparison, matter perturbations in thawing models differ from the cosmological constant only at late times. This difference provides an additional handle to distinguish between these classes of models and this difference should manifest itself in the ISW effect.