Open inflation models and gravitational wave anisotropies in the CMB

Abstract

We study the large scale power spectrum of gravitational wave perturbations of the microwave background in the context of single-bubble open inflation models. We compute the ratio of tensor to scalar contributions to the CMB anisotropies as a function of $\Omega_0$, the spectral index $n_S$ and the tunneling parameter $2\pi GS_1/H$. We find that gravitational wave anisotropies can be very large at small values of this tunneling parameter. We also consider the contribution of supercurvature and bubble wall modes and find constraints on the parameters of open inflation models from the observed temperature anisotropies of the CMB. We show that the induced gravity and open hybrid scenarios are compatible with present observations for a reasonable range of parameters.