  We revisit the F-term hybrid inflation model in supergravity. In particular,
we point out that a constant term in the superpotential has significant effects
on the inflaton dynamics. It is shown that the hybrid inflation model suffers
from several potential problems: tuning of the initial condition, gravitino
overproduction and formation of cosmic strings, for both minimal and
non-minimal Kahler potentials. These problems can only be avoided in
gauge-mediated SUSY breaking models where the gravitino is relatively light and
the constant term in the superpotential is not important. Implications on the
non-thermal leptogenesis scenario are also described.

High Energy Physics - Phenomenology