  In this Letter we discuss the issues of the graceful exit from inflation and
of matter creation in the context of a recent scenario \cite{RHBrev} in which
the back-reaction of long wavelength cosmological perturbations induces a
negative contribution to the cosmological constant and leads to a dynamical
relaxation of the bare cosmological constant. The initially large cosmological
constant gives rise to primordial inflation, during which cosmological
perturbations are stretched beyond the Hubble radius. The cumulative effect of
the long wavelength fluctuations back-reacts on the background geometry in a
form which corresponds to the addition of a negative effective cosmological
constant to the energy-momentum tensor. In the absence of an effective scalar
field driving inflation, whose decay can reheat the Universe, the challenge is
to find a mechanism which produces matter at the end of the relaxation process.
In this Letter, we point out that the decay of a condensate representing the
order parameter for a ``flat'' direction in the field theory moduli space can
naturally provide a matter generation mechanism. The order parameter is
displaced from its vacuum value by thermal or quantum fluctuations, it is
frozen until the Hubble constant drops to a sufficiently low value, and then
begins to oscillate about its ground state. During the period of oscillation it
can decay into Standard Model particles similar to how the inflaton decays in
scalar-field-driven models of inflation.
