  In theories beyond the Standard Model, in particular in theories with extra
spatial dimensions such as superstring theory, there are a large number of
scalar fields which appear in the low energy effective action. These moduli
fields must be stabilized. Often, moduli stabilization involves a stage during
which the moduli fields oscillatte coherently about their ground state value.
Here, we study moduli and graviton production during the period during which
the background modulus field is oscillating, assuming that this period takes
place in the radiation phase. We find a resonant production of moduli
fluctuations, and a tachyonic instability to the generation of long wavelength
gravitational waves. As a consequence, the period of moduli stabilization is
short on a Hubble time scale.
