Enlightening the dark ages with dark matter
  Constraints on dark matter annihilation or decay offer unique insights into
the nature of dark matter. We illustrate how surveys dedicated to detect the
highly redshifted 21 cm signal from the dark ages will offer a new window into
properties of particle dark matter. The 21 cm intensity mapping signal and its
fluctuations are sensitive to energy injection from annihilation or decay of
long-lived particles in a way that is complementary to other probes. We present
forecasted constraints from forthcoming and next-generation radio surveys. We
show that, while SKA might be capable of a detection for some cases, the most
promising opportunity to detect dark matter in the 21 cm intensity mapping
signal is with a futuristic radio array on the lunar far-side, with the
potential to detect a signal many orders of magnitude weaker than current or
maximal constraints from other probes.
