Constraining the Cosmology of the Phantom Brane using Distance Measures
  The phantom brane has several important distinctive features: (i) Its
equation of state is phantom-like, but there is no future `big rip'
singularity, (ii) the effective cosmological constant on the brane is
dynamically screened, because of which the expansion rate is {\em smaller} than
that in $\Lambda$CDM 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 $0 < \Omega_l < 0.3$ at $1\sigma$. The
Hubble parameter can be as high as $H_0 < 78$ km/s/Mpc, and the effective
equation of state at present can show phantom-like behaviour with $w_0 < -1.2$
at $1\sigma$. We note a correlation between $H_0$ and $w_0$, with higher values
of $H_0$ leading to a lower, and more phantom-like, value of $w_0$. Inclusion
of CMB data provides tighter constraints $\Omega_l < 0.1$. (Here $\Omega_l$
encodes the ratio of the five and four dimensional Planck mass.) The Hubble
parameter in this case is more tightly constrained to $H_0 < 71$ km/s/Mpc, and
the effective equation of state to $w_0 < -1.1$. Interestingly, we find that
the universe is allowed be closed or open, with $-0.5 < \Omega_{\kappa} < 0.5$,
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.
