CMB Temperature and Matter Power Spectrum in a Decay Vacuum Dark Energy Model

TL;DR

This paper analyzes a decay vacuum dark energy model's impact on cosmic microwave background and matter power spectrum, comparing it with observational data and exploring its generalizations and parameter constraints.

Contribution

It provides a detailed analysis of the decay vacuum model's background evolution and perturbations, highlighting its limitations in matching observational data.

Findings

Decay vacuum model matches late-time expansion rate but not CMB and matter spectrum.

The generalized model requires the parameter ξ_2 to be zero to avoid fine tuning.

Energy density positivity constrains model parameters.

Abstract

In this paper, a decay vacuum model $\bar{\rho}_\Lambda=3\sigma M_p^2H_0 H$ is revisited by detailed analysis of background evolution and perturbation equations. We show the imprints on CMB temperature and matter power spectrum from the effective coupling terms between dark sectors by comparing to the standard cosmological constant model and observational data points (WMAP7 and SDSS DR7). We find that the decay vacuum model can describe the expansion rate at late times as well as the standard cosmological constant model but it fails to simultaneously reproduce the observed CMB and matter power spectrum. Its generalization $\bar{\rho}_\Lambda=3M_p^2(\xi_1 H_0 H+\xi_2 H^2)$ is also discussed. Detailed analysis of the background evolution shows that the dimensionless parameter $\xi_{2}$ would be zero to avoid the unnatural 'fine tuning' and to keep the positivity of energy density of dark matter and dark energy in the early epoch.