Astro 2020 Science White Paper: Fundamental Cosmology in the Dark Ages with 21-cm Line Fluctuations

TL;DR

This paper discusses the potential of 21-cm line fluctuations during the Dark Ages to provide unique insights into fundamental cosmological parameters, inflation, and dark matter physics, despite observational challenges.

Contribution

It highlights the importance of 21-cm observations for probing the Dark Ages and their potential to constrain key cosmological theories and exotic physics.

Findings

21-cm fluctuations can probe large cosmological volumes

Fluctuations remain linear on small scales during the Dark Ages

Observations can constrain inflation and dark matter physics

Abstract

The Dark Ages are the period between the last scattering of the cosmic microwave background and the appearance of the first luminous sources, spanning approximately 1100 < z < 30. The only known way to measure fluctuations in this era is through the 21-cm line of neutral hydrogen. Such observations have enormous potential for cosmology, because they span a large volume while the fluctuations remain linear even on small scales. Observations of 21-cm fluctuations during this era can therefore constrain fundamental aspects of our Universe, including inflation and any exotic physics of dark matter. While the observational challenges to these low-frequency 21-cm observations are enormous, especially from the terrestrial environment, they represent an important goal for cosmology.