Probing dark energy and primordial non-Gaussianity with the 21cm line observations

Abstract

In this paper I review some recent progress in the studies on redshifted 21cm line observations. The 21cm line have long been an important radio spectral line in astronomical observations, but so far its observation is limited to low redshifts, due to the difficulty in detecting this line at high or mid redshifts. However, more sophisticated data processing method are being developed, and a number of experiments are being carried out. Once this breakthrough is made, the observation may provide an wealth of information which would be useful in probing the nature of dark energy, and searching for primordial non-Gaussianity (PNG). I will also describe the status of the Tianlai experiment as of the summer of 2015.