Nonthermal Gravitino Production after Large Field Inflation
  We revisit the nonthermal gravitino production at the (p)reheating stage
after inflation. Particular attention is paid to large field inflation models
with a $\mathbb{Z}_2$ symmetry, for which the previous perturbative analysis is
inapplicable; and inflation models with a stabilizer superfield, which have not
been studied non-perturbatively. It is found that in single-superfield
inflation models (without the stabilizer field), nonthermal production of the
transverse gravitino can be cosmologically problematic while the abundance of
the longitudinal gravitino is small enough. In multi-superfield inflation
models (with the stabilizer field), production of the transverse and
longitudinal gravitinos is significantly suppressed, and they are
cosmologically harmless. We also clarify the relation between the background
field method used in the preheating context and the standard perturbative decay
method to estimate the gravitino abundance.
