Early-Matter-Like Dark Energy and the Cosmic Microwave Background

Abstract

Early-matter-like dark energy is defined as a dark energy component whose equation of state approaches that of cold dark matter (CDM) at early times. Such a component is an ingredient of unified dark matter (UDM) models, which unify the cold dark matter and the cosmological constant of the LambdaCDM concordance model into a single dark fluid. Power series expansions in conformal time of the perturbations of the various components for a model with early-matter-like dark energy are provided. They allow the calculation of the cosmic microwave background (CMB) anisotropy from the primordial initial values of the perturbations. For a phenomenological UDM model, which agrees with the observations of the local Universe, the CMB anisotropy is computed and compared with the CMB data. It is found that a match to the CMB observations is possible if the so-called effective velocity of sound c_eff of the early-matter-like dark energy component is very close to zero. The modifications on the CMB temperature and polarization power spectra caused by varying the effective velocity of sound are studied.

References in corpus (5)

• Planck 2015 results. XIV. Dark energy and modified gravity
• Dark energy with non-adiabatic sound speed: initial conditions and detectability
• Unified Dark Matter Scalar Field Models
• Non-adiabatic dark fluid cosmology
• Clustering GCG: a viable option for unified dark matter-dark energy?

Cited by in corpus (3)

• The variance of the CMB temperature gradient: a new signature of a multiply connected Universe
• On the concordance of cosmological data in the case of the generalized Chaplygin gas
• Analytic Study of Cosmological Perturbations in a Unified Model of Dark Matter and Dark Energy with a Sharp Transition