A stringy realization of a small and positive cosmological constant in dark bubble cosmology

TL;DR

This paper constructs a string theory model of an expanding universe with a small positive cosmological constant, using branes in extra dimensions, and explores its phenomenological implications.

Contribution

It provides a string-theoretic realization of dark bubble cosmology with loop corrections inducing a small positive cosmological constant.

Findings

Predicts large extra dimensions consistent with observations

Shows loop corrections can generate a small positive cosmological constant

Connects dark bubble cosmology with dark dimension proposals

Abstract

In this paper we construct a stringy embedding of the dark bubble model of an expanding 4D cosmology with the help of branes rotating in extra dimensions. The universe rides a bubble which has nucleated in an unstable higher dimensional background. Our construction is therefore a string theoretical realization of Vilenkin's quantum cosmology. While the cosmological constant vanishes at lowest order, loop corrections predicted by the Weak Gravity Conjecture can induce a phenomenologically viable value. The model predicts the existence of large extra dimensions compatible with observational constraints, and we note a possible connection with the dark dimension proposal.