  It has recently been realized that brane-antibrane annihilation (a possible
explanation for ending inflation) may result in defect formation, due to the
dynamics of the tachyon field. Studies of this possibility have generally
ignored the interaction of the brane fields with fields in the bulk; recently
it has been argued [1] that interactions with bulk fields suppress or even
eliminate defect formation.
  To investigate the impact of bulk fields on brane defect formation, we
construct a toy model that captures the essential features of the tachyon
condensation with bulk fields. We study the structure of defects in this toy
model, and simulate their formation and evolution on the lattice. We find that,
while the energetics and interactions of defects are influenced by the size of
the extra dimension and the bulk-brane coupling, the bulk-brane coupling does
not prevent the formation of a defect network.
