Particle Production in Tachyon Condensation
  We study particle production in the tachyon condensation process as described by different effective actions for the tachyon. By making use of invariant operators, we are able to obtain exact results for the density of produced particles, which is shown to depend strongly on the specific action. In particular, the rate of particle production remains finite only for one of the actions considered, hence confirming results previously appeared in the literature. 
G.L. Alberghi, R. Casadio, A. Tronconi