Large Scale Power and Running Spectral Index in New Old Inflation

We have proposed a new class of inflationary scenarios in which the first stage of expansion is driven by ''old'' false vacuum inflation. This ends by nucleation of a bubble, which then further inflates. Unlike the standard slow-roll scenarios the ''clock'' ending the second inflationary phase is not a local order parameter, but rather the average value of an oscillating scalar field, which locks the system at a saddle point of the potential in a temporary inflationary state. Inflation ends when the amplitude drops below a certain critical point and liberates the system from the false vacuum state. The second stage of inflation has only about 50 e-foldings, a number which is determined entirely by the ratio of the fundamental mass scales, such as the Planck/string scale and the supersymmetry breaking scale. The density perturbations are generated due to fluctuations of moduli-dependent Yukawa couplings. In this note we explore the observable imprints in the fluctuation spectrum of generic cross-couplings in the superpotential and in the Kaehler potential. We show that in the presence of generic non-renormalizable interactions in the superpotential between the fluctuating modulus and the oscillating inflaton, the amplitude of the density perturbations is exponentially cut-off for sufficiently largemore » wavelengths. With reasonable choices of scales and interactions, this long wavelength cutoff can occur at approximately the current horizon size. The perturbative corrections in the Kaehler potential give non-trivial potentially observable tilt and a running of the spectral index which is different from the standard inflationary models.« less