  Fluctuations in the intensity and polarization of the cosmic microwave
background (CMB) and the large-scale distribution of matter in the universe
each contain clues about the nature of the earliest moments of time. The next
generation of CMB and large-scale structure (LSS) experiments are poised to
test the leading paradigm for these earliest moments---the theory of cosmic
inflation---and to detect the imprints of the inflationary epoch, thereby
dramatically increasing our understanding of fundamental physics and the early
universe.
  A future CMB experiment with sufficient angular resolution and frequency
coverage that surveys at least 1% of the sky to a depth of 1 uK-arcmin can
deliver a constraint on the tensor-to-scalar ratio that will either result in a
5-sigma measurement of the energy scale of inflation or rule out all
large-field inflation models, even in the presence of foregrounds and the
gravitational lensing B-mode signal. LSS experiments, particularly
spectroscopic surveys such as the Dark Energy Spectroscopic Instrument, will
complement the CMB effort by improving current constraints on running of the
spectral index by up to a factor of four, improving constraints on curvature by
a factor of ten, and providing non-Gaussianity constraints that are competitive
with the current CMB bounds.
