Inflation driven by single geometric tachyon with D-brane orbiting   around NS5-branes
  We investigate models in which inflation is driven by a single geometrical tachyon. We assume that the D-brane as a probe brane in the background of NS5-branes has non-zero angular momentum which is shown to play similar role as the number of the scalar fields of the assisted inflation. We demonstrate that the angular momentum corrected effective potential allows to account for the observational constraint on COBE normalization, spectral index $n_S$ and the tensor to scalar ratio of perturbations consistent with WMAP seven years data. 
Pyung Seong Kwon, Gyeong Yun Jun, Kamal L. Panigrahi and M. Sami
hep-th