Moving Branes in Presence of the Background Tachyon Fields
  We compute the boundary state associated with a moving D$p$-brane in the presence of the open string tachyon field as a background field. The effect of the tachyon condensation on the boundary state will be discussed. It leads to a boundary state associated with a lower dimensional moving D-brane or a stationary instantonic D-brane. The former originates from condensation along the spatial directions and the latter comes from the temporal direction of the D-brane's worldvolume. Using the boundary state we also study the interaction amplitude between two arbitrary D$p_1$ and D$p_2$-branes. The long range behavior of the amplitude is investigated which shows an obvious deviation from the conventional form, due to the presence of the background tachyon field. 
Zahra Rezaei and Davoud Kamani
hep-th