Constraining the cosmology of the phantom brane using distance measures

The phantom brane has several important distinctive features: (i) Its equation of state is phantomlike, but there is no future ``big rip'' singularity, and (ii) the effective cosmological constant on the brane is dynamically screened, because of which the expansion rate is smaller than that in ΛCDM at high redshifts. In this paper, we constrain the Phantom braneworld using distance measures such as type-Ia supernovae (SNeIa), baryon acoustic oscillations (BAO), and the compressed cosmic microwave background (CMB) data. We find that the simplest braneworld models provide a good fit to the data. For instance, BAO+SNeIa data can be accommodated by the braneworld for a large region in parameter space 0≤Ω_0.3 at 1σ. The Hubble parameter can be as high as H₀78 km s^-1 Mpc^-1, and the effective equation of state at present can show phantomlike behavior with w₀-1.2 at 1σ. We note a correlation between H₀ and w₀, with higher values of H₀ leading to a lower, and more phantomlike, value of w₀. Inclusion of CMB data provides tighter constraints Ω_0.1. (Here Ω_ encodes the ratio of the five- and four-dimensional Planck mass.) The Hubble parameter in this case is more tightly constrained to H₀71 km s^-1 Mpc^-1, and the effective equation of state to w₀-1.1. Interestingly, we find that the Universe is allowed to be closed or open, with -0.5Ω_κ0.5, even on including the compressed CMB data. There appears to be some tension in the low and high-z BAO data which may either be resolved by future data, or act as a pointer to interesting new cosmology.