Tubular D-branes in Salam-Sezgin Model
  We study DBI-type effective theory of an unstable D3-brane in the background manifold R^{1,1} x M_2 where M_2 is an arbitrary two-dimensional manifold. We obtain an exact tubular D2-brane solution of arbitrary cross sectional shape by employing 1/cosh tachyon potential. When M_2=S^2, the solution is embedded in the background geometry R^{1,3} x S^2 of Salam-Sezgin model. This tachyon potential shows a unique property that an array of tachyon soliton solutions has a fixed period which is independent of integration constants of the equations of motion. The thin BPS limit of the configurations leads to supertubes of arbitrary cross sectional shapes. 
Chanju Kim, Yoonbai Kim, O-Kab Kwon