Non-Gaussianity and finite length inflation
  In the present paper, certain inflation models are shown to have large
non-Gaussianity in special cases. Namely, finite length inflation models with
an effective higher derivative interaction, in which slow-roll inflation is
adopted as inflation and a scalar-matter-dominated period or power inflation is
adopted as pre-inflation, are considered. Using Holman and Tolley's formula of
the nonlinearity parameter $f^\textrm{\tiny flattened}_\textrm{\tiny NL}$, we
calculate the value of $f^\textrm{\tiny flattened}_\textrm{\tiny NL}$. A large
value of $f^\textrm{\tiny flattened}_\textrm{\tiny NL}(f^\textrm{\tiny
flattened}_\textrm{\tiny NL} > 100)$ can be obtained for all of the models
considered herein when the length of inflation is 60-63 $e$-folds and
$f_\textrm{\tiny NL}$ has strong dependence on the length of inflation.
Interestingly, this length is similar to that for the case in which the
suppression of the CMB angular power spectrum of $l=2$ was derived using the
inflation models described in our previous papers.
