Abstract:
Open inflation is receiving renewed interest in the context of string landscape. Since there are a large number of metastable de Sitter vacua in the string landscape, tunneling from one vacuum to another occurs frequently through the bubble nucleation and open inflation is naturally realized. We argue that though the universe appears to be very flat, a small deviation of $\Omega_{0}$ from unity can make the effect of tensor-type perturbations on the large angle CMB anisotropy significant. Thus we are already testing the string landscape against observations.