  We study a class of non-local, action-based, and purely gravitational models.
These models seek to describe a cosmology in which inflation is driven by a
large, bare cosmological constant that is screened by the self-gravitation
between the soft gravitons that inflation rips from the vacuum. Inflation ends
with the universe poised on the verge of gravitational collapse, in an
oscillating phase of expansion and contraction that should lead to rapid
reheating when matter is included. After the attainment of a hot, dense
universe the nonlocal screening terms become constant as the universe evolves
through a conventional phase of radiation domination. The onset of matter
domination triggers a much smaller anti-screening effect that could explain the
current phase of acceleration.
