A small Universe

Understand

Many cosmological models assume or imply that the total size of the universe is very large, perhaps even infinite.

• Here we argue instead that the universe might be comparatively small, in fact not much larger than the currently observed size.
• A concrete implementation of this idea is provided by the no-boundary proposal, in combination with a plateau-shaped inflationary potential.
• In this model, opposing effects of the weighting of the wave function and of the criterion of allowability of the geometries conspire to favour small universes.