  We consider a brane world inflationary model in which inflation is driven by
dynamics of a self-interacting scalar field living in the five-dimensional
bulk. The scalar field is non-minimally coupled to matter fields on the brane
and acts as an inflaton which induces a slow-roll inflation. We show that
although the Friedmann equation is modified at early times due to effects of
the extra dimension, the slow-roll condition is the same as that of the
four-dimensional case. Due to the non-minimal coupling of matter with the bulk
scalar, there is an energy transfer between the two components. We investigate
the conditions under which the direction of this energy transfer can be from
matter onto the bulk scalar. There are at least two advantages in this case: 1)
It establishes a mechanism by which a large effective cosmological term on the
brane is deflated during the inflation period. 2) The energy flow onto the bulk
inflaton gives a more strongly damped evolution of the scalar field in the
slow-roll region for a given potential. We then show that our results are
supported by numerical estimations with quadratic and exponential potentials.
