Testing the effects from dark radiation

TL;DR

This paper tests the effects of dark radiation using phase-space analysis and observational data, showing it can reconcile data tensions and slightly increase the effective number of neutrino species.

Contribution

It applies phase-space analysis to dark radiation models and uses multiple observational datasets to evaluate their consistency with cosmological history.

Findings

Dark radiation models are consistent with universe history.

Dark radiation reduces data tensions in flat ΛCDM.

Dark radiation slightly increases N_eff beyond 3.04.

Abstract

In this letter, the effects of dark radiation (DR) are tested. Theoretically, the phase-space analysis method is applied to check whether the model is consist with the history of our universe which shows positive results. Observationally, by using the observational data ($SNLS$ (SuperNovae Legacy Survey), $WMAP9$(Wilkinson Microwave Anisotropy Probe 9 Years Result), $PLANCK$ (Planck First Data Release), $BAO$ (Baryon Acoustic Oscillations), $H(z)$ (Hubble Parameter Data) and $BBN$ (Big Bang Nucleosynthesis)), the dark radiation is found to have the effect of wiping out the tension between the $SNLS$ data and the other data in flat $\Lambda CDM$ model. The effects of dark radiation also make the best fit value of $N_{eff}$ slightly larger than 3.04.