Limits on decaying dark energy density models from the CMB temperature-redshift relation

TL;DR

This paper investigates a decaying dark energy model where dark energy transforms into photons and particles, deriving a temperature-redshift relation for the CMB, and constrains the model parameters using observational data.

Contribution

It derives a new temperature-redshift relation for decaying dark energy models and constrains the effective equation of state using observational data.

Findings

Effective equation of state w_eff = -0.97 ± 0.034

Results compatible with a constant dark energy density

Supports dark energy being consistent with a cosmological constant

Abstract

The nature of the dark energy is still a mystery and several models have been proposed to explain it. Here we consider a phenomenological model for dark energy decay into photons and particles as proposed by Lima (J. Lima, Phys. Rev. D 54, 2571 (1996)). He studied the thermodynamic aspects of decaying dark energy models in particular in the case of a continuous photon creation and/or disruption. Following his approach, we derive a temperature redshift relation for the CMB which depends on the effective equation of state $w_{eff}$ and on the "adiabatic index" $\gamma$. Comparing our relation with the data on the CMB temperature as a function of the redshift obtained from Sunyaev-Zel'dovich observations and at higher redshift from quasar absorption line spectra, we find $w_{eff}=-0.97 \pm 0.034$, adopting for the adiabatic index $\gamma=4/3$, in good agreement with current estimates and still compatible with $w_{eff}=-1$, implying that the dark energy content being constant in time.