Quintessence: A Review

TL;DR

This review discusses the theoretical models, observational constraints, and particle physics motivations of quintessence as a dynamic dark energy candidate explaining late-time cosmic acceleration.

Contribution

It provides analytical expressions for the evolution of dark energy and growth of structure, constrains models with current data, and reviews particle physics models of quintessence.

Findings

Thawing models constrained to w_0<-0.7 (95% CL)

Tracking models are hard to distinguish from LCDM

Analytic formulae for growth rate of matter perturbations

Abstract

Quintessence is a canonical scalar field introduced to explain the late-time cosmic acceleration. The cosmological dynamics of quintessence is reviewed, paying particular attention to the evolution of the dark energy equation of state w. For the field potentials having tracking and thawing properties, the evolution of w can be known analytically in terms of a few model parameters. Using the analytic expression of w, we constrain quintessence models from the observations of supernovae type Ia, cosmic microwave background, and baryon acoustic oscillations. The tracking freezing models are hardly distinguishable from the LCDM model, whereas in thawing models the today's field equation of state is constrained to be w_0<-0.7 (95 % CL). We also derive an analytic formula for the growth rate of matter density perturbations in dynamical dark energy models, which allows a possibility to put further bounds on w from the measurement of redshift-space distortions in the galaxy power spectrum. Finally we review particle physics models of quintessence- such as those motivated by supersymmetric theories. The field potentials of thawing models based on a pseudo-Nambu-Goldstone boson or on extended supergravity theories have a nice property that a tiny mass of quintessence can be protected against radiative corrections.