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≤Ωℓ≲0.3 at 1σ. The Hubble parameter can be as high as H0≲78 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 Ωℓ≲0.1. (Here Ωℓ encodes the ratio of the five- and four-dimensional Planck mass.) The Hubble parameter in this case is more tightly constrained to H0≲71 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 −0.5≲Ωκ≲0.5, 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.