Cosmology with Ricci dark energy

TL;DR

This paper explores a Ricci-scale holographic dark energy model in cosmology, analyzing its background and perturbation dynamics, and compares its predictions with observational data, revealing stability issues and parameter constraints.

Contribution

It introduces a Ricci-scale holographic dark energy model with a detailed analysis of perturbations and observational consistency, highlighting stability constraints.

Findings

Background dynamics align with supernova and BAO data.

Perturbation analysis shows instabilities excluding phantom equations.

Stable configurations are marginally consistent with observations.

Abstract

We assume the cosmological dark sector to consist of pressureless matter and holographic dark energy with a cutoff length proportional to the Ricci scale. The requirement of separate energy-momentum conservation of the components is shown to establish a relation between the matter fraction and the (necessarily time-dependent) equation-of-state parameter of the dark energy. Focusing on intrinsically adiabatic pressure perturbations of the dark-energy component, the matter perturbations are found as linear combinations of the total energy-density perturbations of the cosmic medium and the relative (nonadiabatic) perturbations of the components. The resulting background dynamics is consistent with observations from supernovae of type Ia, baryonic acoustic oscillations and the differential age of old objects. The perturbation dynamics, on the other hand, is plagued by instabilities which excludes any phantom-type equation of state. The only stable configuration is singled out by a fixed relation between the present matter fraction $\Omega_{m0}$ and the present value $\omega_{0}$ of the equation-of-state parameter of the dark energy. However, this instability-avoiding configuration is only marginally consistent with the observationally preferred background values of the mentioned parameters.