Cosmological Perturbations in the One-Bubble Open Universe

The spectrum of cosmological perturbations in the context of the one-bubble open inflation model is discussed fully taking into account fluctuations of the metric. For most of single field models, we find that there is no supercurvature mode. It is also proved that the model dependence of the continuous spectrum for both scalar and tensor type perturbations is small as long as the kinetic energy density of the background field does not dominate the total energy density. We conclude that the spectrum of the one-bubble open inflation is rather robust. The inplication to the two-field model is also discussed.