Current cosmological constraints on the curvature, dark energy and
  modified gravity
  We apply the Union2 compilation of 557 supernova Ia data, the baryon acoustic
oscillation measurement of distance, the cosmic microwave background radiation
data from the seven year Wilkinson Microwave Anisotropy Probe, and the Hubble
parameter data to study the geometry of the Universe and the property of dark
energy by using models and parametrizations with different high redshift
behaviours of $w(z)$. We find that $\Lambda$CDM model is consistent with
current data, that the Dvali-Gabadadze-Porrati model is excluded by the data at
more than $3\sigma$ level, that the Universe is almost flat, and that the
current data is unable to distinguish models with different behaviours of
$w(z)$ at high redshift. We also add the growth factor data to constrain the
growth index of Dvali-Gabadadze-Porrati model and find that it is more than
$1\sigma$ away from its theoretical value.
