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

Understand

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.