A note on Tachyon dynamics
  A suitable splitting of tachyon field equation is able to disclose non trivial properties of Born-Infeld (some known, some unexpected) and Polyakov actions; the tachyon equation also can be analyzed in some detail. The analysis displays an intriguing connection between sine-Gordon theory and some crucial issues such as the emergence of perturbative string states when a D-Brane and an anti-D-Brane annihilate and the confinement of charged D-Branes. 
F. Canfora