Open inflation without false vacua

We show that within the framework of a definite proposal for the initial conditions for the universe, the Hartle–Hawking “no boundary” proposal, open inflation is generic and does not require any special properties of the inflaton potential. In the simplest inflationary models, the semiclassical approximation to the Euclidean path integral and a minimal anthropic condition lead to Ω0≈0.01. This number may be increased in models with more fields or extra dimensions.