Observational Constraints on Phantom Crossing DGP Gravity
  We study the observational constraints on the Phantom Crossing DGP model. We
demonstrate that the crossing of the phantom divide does not occur within the
framework of the original Dvali-Gabadadze-Porrati (DGP) model or the DGP model
developed by Dvali and Turner. By extending their model in the framework of an
extra dimension scenario, we study a model that realizes crossing of the
phantom divide. We investigate the cosmological constraints obtained from the
recent observational data of Type Ia Supernovae, Cosmic Microwave Background
anisotropies, and Baryon Acoustic Oscillations. The best fit values of the
parameters with 1$\sigma$ (68%) errors for the Phantom Crossing DGP model are
$\Omega_{m,0}=0.27^{+0.02}_{-0.02}$, $\beta=0.54^{+0.24}_{-0.30}$. We find that
the Phantom Crossing DGP model is more compatible with the observations than
the original DGP model or the DGP model developed by Dvali and Turner. Our
model can realize late-time acceleration of the universe, similar to that of
$\Lambda$CDM model, without dark energy due to the effect of DGP gravity. In
our model, crossing of the phantom divide occurs at a redshift of $z \sim 0.2$.
