Quintessence reconstructed: new constraints and tracker viability
  We update and extend our previous work reconstructing the potential of a quintessence field from current observational data. We extend the cosmological dataset to include new supernova data, plus information from the cosmic microwave background and from baryon acoustic oscillations. We extend the modelling by considering Pad\'e approximant expansions as well as Taylor series, and by using observations to assess the viability of the tracker hypothesis. We find that parameter constraints have improved by a factor of two, with a strengthening of the preference of the cosmological constant over evolving quintessence models. Present data show some signs, though inconclusive, of favouring tracker models over non-tracker models under our assumptions. 
Martin Sahl\'en, Andrew R Liddle, and David Parkinson