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.