Cosmology with Neutral Hydrogen
Galaxy surveys have shown to be extremely powerful in mapping the Large Scale Structure (LSS) of the Universe. In combination with CMB data, they delivered the concordance LCDM model. On the other hand, we are still far from reaching the cosmic variance limit in the determination of several cosmological parameters, including neutrino masses and primordial non-gaussianities. Moreover, most of the volume of the Universe lives at z>2, where observing galaxies at high number densities becomes increasingly more difficult (and expensive). A possible solution is offered by neutral hydrogen (HI), which can be observed at very large scales, and with high sampling. In emission, HI can be mapped using the 21 cm or the Lyman-alpha line. In this talk I will discuss challenges in the modeling of the 21 cm line in the post-reionization era, presenting forecasts for a next generation experiment at z>2.5. I'll then discuss Lyman-alpha emitters (LAE), focusing on an effective description of radiative transfer effects on their clustering properties.