Quintessence versus phantom dark energy: the arbitrating power of
  current and future observations
  We analyze the possibility to distinguish between quintessence and phantom
scalar field models of dark energy using observations of luminosity distance
moduli of SNe Ia, CMB anisotropies and polarization, matter density
perturbations and baryon acoustic oscillations. Among the present observations
only Planck data on CMB anisotropy and SDSS DR9 data on baryon acoustic
oscillations may be able to decide between quintessence or phantom scalar field
models, however for each model a set of best-fit parameters exists, which
matches all data with similar goodness of fit. We compare the relative
differences of best-fit model predictions with observational uncertainties for
each type of data and we show that the accuracy of SNe Ia luminosity distance
data is far from the one necessary to distinguish these types of dark energy
models, while the CMB data (WMAP, ACT, SPT and especially Planck) are close to
being able to reliably distinguish them. Also an improvement of the large-scale
structure data (future releses of SDSS BOSS and e.g. Euclid or BigBOSS) will
enable us to surely decide between quintessence and phantom dark energy.
