The Dark Dimension in a Warped Throat

TL;DR

This paper proposes a string theory model where a warped throat creates a large, mesoscopic extra dimension, aligning with swampland conjectures and observational data, and discusses its implications for the universe's structure.

Contribution

It introduces a string theoretic mechanism using a warped throat to realize a large extra dimension scaling with the cosmological constant, connecting quantum gravity conjectures with observable universe features.

Findings

A warped throat can produce a large extra dimension of size ~10^{-6} m.

The KK tower in the throat scales as m ~ Λ^{1/4}.

Challenges remain in keeping other KK modes heavy enough to satisfy astrophysical constraints.

Abstract

By combining swampland conjectures with observational data, it was suggested that our universe should lie in an asymptotic region of the quantum gravity landscape. The generalized distance conjecture for dS, the smallness of the cosmological constant and astrophysical constraints led to a scenario with one mesoscopic large dimension of size $\ell\sim \Lambda^{-1/4}\sim 10^{-6}$m. We point out that a strongly warped throat with its redshifted KK tower provides a natural string theoretic mechanism that realizes the scaling $m\sim \Lambda^{\alpha}$ with the factor $\alpha=1/4$, the dark dimension being the one along the throat. We point out that in string theory it could be challenging to keep other KK towers heavy enough to avoid a conflict with astrophysical constraints on the number of extra large dimensions.