Constraints on a vacuum energy from both SNIa and CMB temperature observations

TL;DR

This paper explores how a decaying vacuum energy influences cosmic thermal evolution and constrains its properties using recent supernova and CMB temperature data, revealing small effects at low redshift and tighter constraints at early epochs.

Contribution

It introduces a model where vacuum energy decays into photons and constrains this with observational data, highlighting its minimal impact on late-time cosmic expansion.

Findings

Decaying vacuum energy effects are small but possible for z < 1.5.

CMB temperature observations impose strict constraints on vacuum decay parameters.

Thermal evolution deviations are mainly at early epochs.

Abstract

We investigate the cosmic thermal evolution with a vacuum energy which decays into photon at the low-redshift. We assume that the vacuum energy is a function of the scale factor that increases toward the early universe. We put on the constraints using recent observations of both type Ia supernovae (SNIa) by Union-2 compilation and the cosmic microwave background (CMB) temperature at the range of the redshift 0.01 < z < 3. From SNIa, we find that the effects of a decaying vacuum energy on the cosmic expansion rate should be very small but could be possible for z < 1.5. On the other hand, we obtain the severe constraints for parameters from the CMB temperature observations. Although the temperature can be still lower than the case of the standard cosmological model, it should only affect the thermal evolution at the early epoch.