A small Universe

TL;DR

This paper proposes that the universe might be small rather than infinite, supported by the no-boundary proposal and inflationary models, aligning with swampland conjectures and dark dimension ideas.

Contribution

It introduces a model where the universe's small size is favored by quantum cosmology and inflation, challenging the common assumption of an infinitely large universe.

Findings

Small universes are favored by the no-boundary proposal.

The model aligns with swampland conjectures.

It relates to the dark dimension scenario.

Abstract

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. We point out that a small size of the universe also fits well with swampland conjectures, and we comment on the relation with the dark dimension scenario.