Tachyon Condensation and Brane Descent Relations in p-adic String Theory
  It has been conjectured that an extremum of the tachyon potential of a bosonic D-brane represents the vacuum without any D-brane, and that various tachyonic lump solutions represent D-branes of lower dimension. We show that the tree level effective action of p-adic string theory, the expression for which is known exactly, provides an explicit realisation of these conjectures. 
Debashis Ghoshal and Ashoke Sen