Cosmic vector for dark energy: Constraints from supernovae, cosmic microwave background, and baryon acoustic oscillations

It has been recently shown that the presence of a vector field over cosmological scales could explain the observed accelerated expansion of the Universe without introducing either new scales or unnatural initial conditions in the early Universe, thus avoiding the coincidence problem. Here, we present a detailed analysis of the constraints imposed by supernova type Ia (SNIa), cosmic microwave background (CMB), and baryon acoustic oscillation (BAO) data on the vector dark energy model with general spatial curvature. We find that contrary to standard cosmology, CMB data exclude a flat universe for this model and, in fact, predict a closed geometry for the spatial sections. We see that CMB and SNIa Gold data are perfectly compatible at the 1-sigma level, however the SNIa Union data set exhibits a 3-sigma tension with CMB. The same level of tension is also found between SNIa and BAO measurements.