Scalar fields with barotropic equation of state: quintessence versus
  phantom
  We constrain the parameters of dynamical dark energy in the form of a
classical scalar field with barotropic equation of state jointly with other
cosmological parameters using various combined datasets including the CMB power
spectra from WMAP7, the baryon acoustic oscillations in the space distribution
of galaxies from SDSS DR7 and WiggleZ, the light curves of SN Ia from 3
different compilations: SDSS (SALT2 and MLCS2k2 light curve fittings), SNLS3
and Union2.1. The considered class of models involves both quintessential and
phantom subclasses. The analysis has shown that the phantom models are
generally preferred by the observational data. We discuss the effect of
allowing for non-zero masses of active neutrinos, non-zero curvature or
non-zero contribution from the tensor mode of perturbations on the precision of
dark energy parameters estimation. We also perform a forecast for the Planck
mock data.
