Emanuele Castorina (UCB) "Cosmology with Neutral Hydrogen in the Post Eeionization Era"

Measurements of the Cosmic Microwave Background (CMB) anisotropies and, more recently, of the distribution of galaxies at late times led us to the definition of a concordance cosmological model, the so called LCDM model. Despite its phenomenological success, several fundamental questions about the origin and fate of our Universe remain unanswered in the simplest LCDM scenario.  What mechanism, if any, has set up the initial conditions of the Universe? What is nature of Dark Energy? What is the value of neutrinos masses, and are there any other light particles?

Several upcoming experiments, like DESI, LSST and Simons Observatory, promise to shed light on some of these misteries, but will still be very far from the cosmic variance limit.

In fact most of the observable volume of the Universe lives at redshift z>2,  where observing galaxies at high number densities becomes increasingly more difficult.

A possible solution is offered by neutral hydrogen (HI), which is ubiquitous in our Universe at z<6. In emission, HI can be mapped using the infamous 21 cm line at radio frequencies.

In this talk, after summarizing the current status of 21 cm observations, I will present the science case for a Stage-II 21 cm experiment targeting the redshift range 2<z<6, and show it will dramatically improve our knowledge of DE and inflation, while keep reducing errorbars on other cosmological parameters.