  We investigate the star formation history of the universe using FIREWORKS, a
multiwavelength survey of the CDFS. We study the evolution of the specific star
formation rate (sSFR) with redshift in different mass bins from z = 0 to z ~ 3.
We find that the sSFR increases with redshift for all masses. The logarithmic
increase of the sSFR with redshift is nearly independent of mass, but this
cannot yet be verified at the lowest-mass bins at z > 0.8, due to
incompleteness. We convert the sSFRs to a dimensionless growth rate to
facilitate a comparison with a semi-analytic galaxy formation model that was
implemented on the Millennium Simulation. The model predicts that the growth
rates and sSFRs increase similarly with redshift for all masses, consistent
with the observations. However, we find that for all masses, the inferred
observed growth rates increase more rapidly with redshift than the model
predictions. We discuss several possible causes for this discrepancy, ranging
from field-to-field variance, conversions to SFR, and shape of the IMF. We find
that none of these can solve the discrepancy completely. We conclude that the
models need to be adapted to produce the steep increase in growth rate between
redshift z=0 and z=1.
