Constraining the nature of dark energy using the SKA

Current models for dark energy include a cosmological constant and scalar field models such as quintessence and k-essence. By measuring the dark energy sound speed, c_{eff}, and its equation of state parameter, w, one can distinguish between these. Here we investigate the possibility of measuring c_{eff} and w using combined observations from the SKA and CMB experiments. We present theoretical predictions for the cross-power spectrum of ISW fluctuations in the CMB and the expected field of HI galaxies detectable with the SKA.