Constraints on the dark energy with barotropic equation of state:
  assessing the importance of different observations
  For dynamical dark energy with the barotropic equation of state we determine
the mean values of parameters and their confidence ranges together with other
cosmological parameters on the basis of different combined datasets. The used
observations include Planck data on CMB temperature anisotropy, E-mode
polarization and lensing, BICEP2/Keck Array data on B-mode polarization, BAO
from SDSS and 6dFGS, power spectrum of galaxies from WiggleZ, weak lensing from
CFHTLenS and SN Ia data from the JLA compilation. We find that all but one mean
models are phantom, mean values of the equation of state parameter at current
epoch are close to $-1$ and constraints on the adiabatic sound speed of dark
energy are weak. We investigate the effect of CMB polarization data on the dark
energy parameters estimation. We discuss also which type of data on the large
scale structure of the Universe allows to determine the dark energy parameters
most precisely.
