Constraining dark energy using observational growth rate data
  Observational growth rate data had been derived from observations of redshift
distortions in galaxy redshift surveys. Here we use the growth rate data to
place constraints on the dark energy model parameters. By performing a joint
analysis with the Type Ia supernova, baryon acoustic oscillation and cosmic
microwave background data, it is found that the growth rate data are useful for
improving the constraints. The joint constraints show that the $\Lambda$CDM
model is still in good agreement with current observations, although a
time-variant dark energy still cannot be ruled out. It is argued that the
growth rate data are helpful for understanding the dark energy. With more
accurate data available in the future, we will have a powerful tool for
constraining the cosmological and dark energy parameters.
