Cosmology from the EoR/Cosmic Dawn with the SKA
  The SKA will build upon early detections of the EoR by precursor instruments,
such as MWA, PAPER, and LOFAR, and planned instruments, such as HERA, to make
the first high signal-to-noise measurements of fluctuations in the 21 cm
brightness temperature from both reionization and the cosmic dawn. This will
allow both imaging and statistical maps of the 21cm signal at redshifts z = 6 -
27 and constrain the underlying cosmology and evolution of the density field.
This era includes nearly 60% of the (in principle) observable volume of the
Universe and many more linear modes than the CMB, presenting an opportunity for
SKA to usher in a new level of precision cosmology. This optimistic picture is
complicated by the need to understand and remove the effect of astrophysics, so
that systematics rather than statistics will limit constraints. This chapter
describes the cosmological, as opposed to astrophysical, information available
to SKA. Key areas for discussion include: cosmological parameters constraints
using 21cm fluctuations as a tracer of the density field; lensing of the 21cm
signal, constraints on heating via exotic physics such as decaying or
annihilating dark matter; impact of fundamental physics such as non-Gaussianity
or warm dark matter on the source population; and constraints on the bulk flows
arising from the decoupling of baryons and photons at z = 1000. The chapter
explores the path to separating cosmology from astrophysics, for example via
velocity space distortions and separation in redshift. We discuss new
opportunities for extracting cosmology made possible by the sensitivity of SKA
Phase 1 and explores the advances achievable with SKA2.
