  We study the embedding of flat BPS 3-branes in five dimensional N=2
supergravity theory. We derive the branes' dynamical equations as well as
general expressions for the hypermultiplet fields then focus on a single brane
and study its time evolution. It is shown that the brane's Hubble parameter
correlates with the moduli of the underlying manifold's complex structure. For
certain particular solutions, the moduli seem to exhibit an instability; being
large valued at early times then rapidly decaying to either zero or some
convergent constant value. The possibility of extending these results to the
cosmology of our universe is implied and briefly discussed. Our results are in
line with the production and decay of heavy moduli in the early universe, as is
currently believed in the literature.
