Testing the effects from dark radiation
  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.
