Dynamics of dark energy

TL;DR

This paper reviews various theoretical and observational approaches to understanding dark energy, emphasizing scalar field models, cosmological perturbations, and modifications of gravity to explain the universe's accelerated expansion.

Contribution

It provides a comprehensive overview of dark energy models, including scalar fields and modified gravity, and discusses methods to reconstruct the dark energy equation of state from observations.

Findings

Scalar field models can explain acceleration with different potentials.

Cosmological perturbations help constrain dark energy properties.

Modified gravity offers alternative explanations without new energy components.

Abstract

In this paper we review in detail a number of approaches that have been adopted to try and explain the remarkable observation of our accelerating Universe. In particular we discuss the arguments for and recent progress made towards understanding the nature of dark energy. We review the observational evidence for the current accelerated expansion of the universe and present a number of dark energy models in addition to the conventional cosmological constant, paying particular attention to scalar field models such as quintessence, K-essence, tachyon, phantom and dilatonic models. The importance of cosmological scaling solutions is emphasized when studying the dynamical system of scalar fields including coupled dark energy. We study the evolution of cosmological perturbations allowing us to confront them with the observation of the Cosmic Microwave Background and Large Scale Structure and demonstrate how it is possible in principle to reconstruct the equation of state of dark energy by also using Supernovae Ia observational data. We also discuss in detail the nature of tracking solutions in cosmology, particle physics and braneworld models of dark energy, the nature of possible future singularities, the effect of higher order curvature terms to avoid a Big Rip singularity, and approaches to modifying gravity which leads to a late-time accelerated expansion without recourse to a new form of dark energy.