  We study the phase space of initial conditions for brane inflation, and find
that including the effects of the Dirac-Born-Infeld (DBI) kinetic term
dramatically improves previous estimates on the amount of fine tuning of
initial conditions necessary for inflation, even for models dominated by slow
roll. Two effects turn out to be important for the phase space analysis:
restrictions on the total available phase space due to UV effects in brane
inflation, and the extension of the inflationary attractor to the DBI
inflationary regime. We compare the amount of initial conditions fine tuning
required for a brane inflation model and its standard field theory counterpart
and find that brane inflation decreases the required tuning by several orders
of magnitude.
