  We study inflation arising from the motion of a BPS D3-brane in the
background of a stack of k parallel D5-branes. There are two scalar fields in
this set up-- (i) the radion field R, a real scalar field, and (ii) a complex
tachyonic scalar field chi living on the world volume of the open string
stretched between the D3 and D5 branes. We find that inflation is realized by
the potential of the radion field, which satisfies observational constraints
coming from the Cosmic Microwave Background. After the radion becomes of order
the string length scale l_s, the dynamics is governed by the potential of the
complex scalar field. Since this field has a standard kinematic term, reheating
can be successfully realized by the mechanism of tachyonic preheating with
spontaneous symmetry breaking.
