  We consider cosmological consequences of string theory tachyon condensation.
We show that it is very difficult to obtain inflation in the simplest versions
of this theory. Typically, inflation in these theories could occur only at
super-Planckian densities, where the effective 4D field theory is inapplicable.
Reheating and creation of matter in models where the tachyon potential V(T) has
a minimum at infinitely large T is problematic because the tachyon field in
such theories does not oscillate. If the universe after inflation is dominated
by the energy density of the tachyon condensate, it will always remain
dominated by the tachyons. It might happen that string condensation is
responsible for a short stage of inflation at a nearly Planckian density, but
one would need to have a second stage of inflation after that. This would imply
that the tachyon played no role in the post-inflationary universe until the
very late stages of its evolution. These problems do not appear in the recently
proposed models of hybrid inflation where the complex tachyon field has a
minimum at T << M_p.
