Geometric Tachyon and Warm Inflation
  The inflationary models developed in presence of a background radiation can
be a solution to the reheating problem faced by common cold (isentropic)
inflationary scenario. A D-brane system comprising of k Neuvo-Schwarz(NS)
5-branes with a transverse circle and BPS D3-branes with world volume parallel
to the NS 5-branes, placed at a point on the transverse circle diametrically
opposite to the NS 5-branes has a point of unstable equilibrium and the D3
brane has a geometric tachyonic mode associated with displacement of the brane
along the circle. Cold inflationary scenario has been studied in connection
with this geometric tachyon \cite{PA1} where it was found that one needs a
background of minimum $10^4$ branes to realize a viable inflationary model. In
this piece of work, we have tried to study a model of inflation driven by this
geometric tachoyn in presence of radiation. We have found that compared to the
isentropic scenario, to satisfy the observational bounds, the number of
background branes required in this case reduces drastically and a viable model
can be obtained with even six to seven NS 5-branes in the background.In this
context, we have also analyzed the non-gaussianity associated with the model
and observed that the concerned parameter lies well within the observation
limit.
