We show that a low-energy action for massless fluctuations around a tachyonic
soliton background representing a codimension one D-brane coincides with the
Dirac-Born-Infeld action. The scalar modes which describe transverse
oscillations of the D-brane are translational collective coordinates of the
soliton. The appearance of the DBI action is a universal feature independent of
details of a tachyon effective action, provided it has the structure implied by
the open string sigma model partition function.Comment: LaTex, 15 p. v2: references adde