In the inflationary cosmology it occurs frequently that the inflaton field is trapped in a local , transient minimum with non-zero vacuum energy .
The difficulty regarding the curvature perturbation produced during such a stage is that classically the inflaton does not move so that the comoving hypersurfaces are not well defined at linear order in the scalar field perturbation .
In this paper , assuming a mechanism of trapping which resembles a high temperature correction to the potential , we explicitly calculate for the first time the resulting power spectrum of the curvature perturbation by evaluating the quantum two-point correlation function directly .
The spectrum is steeply blue with the spectral index n _ { \mathcal { R } } = 4 .