Decaying Dark Energy in Light of the Latest Cosmological Dataset

Ivan De Martino

doi:10.3390/sym10090372

Abstract

Decaying Dark Energy models modify the background evolution of the most common observables, such as the Hubble function, the luminosity distance and the Cosmic Microwave Background temperature–redshift scaling relation. We use the most recent observationally-determined datasets, including Supernovae Type Ia and Gamma Ray Bursts data, along with H ( z ) and Cosmic Microwave Background temperature versus z data and the reduced Cosmic Microwave Background parameters, to improve the previous constraints on these models. We perform a Monte Carlo Markov Chain analysis to constrain the parameter space, on the basis of two distinct methods. In view of the first method, the Hubble constant and the matter density are left to vary freely. In this case, our results are compatible with previous analyses associated with decaying Dark Energy models, as well as with the most recent description of the cosmological background. In view of the second method, we set the Hubble constant and the matter density to their best fit values obtained by the Planck satellite, reducing the parameter space to two dimensions, and improving the existent constraints on the model’s parameters. Our results suggest that the accelerated expansion of the Universe is well described by the cosmological constant, and we argue that forthcoming observations will play a determinant role to constrain/rule out decaying Dark Energy.

Highlights

In the last decades, several observations have pointed out that the Universe is in an ongoing period of accelerated expansion that is driven by the presence of an exotic fluid with negative pressure [1,2,3,4,5,6,7,8,9,10,11,12].Its simplest form is a cosmological constant Λ, having an equation of state w = −1
Our results suggest that the accelerated expansion of the Universe is well described by the cosmological constant, and we argue that forthcoming observations will play a determinant role to constrain/rule out decaying Dark Energy
We carried out two sets of analysis: (A) we fit the whole parameter space composed by the Hubble constant H0, the matter density parameter Ωm,0, γ and m; and (B) we set H0 = 67.37 ± 0.54 and Ωm,0 = 0.3147 ± 0.0074 which are the best fit values of joint analysis of the Cosmic Microwave Background (CMB) power spectrum and other probes [10], while m and γ stay free to vary

Summary

Introduction

Introducing higher order terms of the Ricci curvature in the Hilbert–Einstein Lagrangian, gives rise to an effective matter stress–energy tensor which could drive the current accelerated expansion (see, for example, the reviews [12,30,31,32,33,34,35]). Another alternative for reproducing the dark energy effects is by introducing non-derivative terms interactions in the action, in addition to the Einstein–Hilbert action term, such that it creates the effect of a massive graviton [36,37,38]

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Conclusion