Constraining strongly-warped extra dimensions with rotating black holes

TL;DR

This paper uses superradiant instabilities of rotating black holes to place constraints on the size and warping of extra dimensions in string theory models, especially those involving strongly warped throats.

Contribution

It introduces a method to constrain warped extra dimensions by analyzing superradiant instabilities of spin-2 fields around black holes, specifically within the Randall-Sundrum model.

Findings

Constraints on the size of the extra dimension.

Bounds on the curvature of $AdS_5$.

Implications for string theory models with warped throats.

Abstract

Massive bosonic fields can trigger superradiant instabilities in rotating astrophysical black holes leading to gaps in their mass-spin distribution. For spin-2 fields, the instability timescale is orders of magnitude shorter than for any other superradiant mode, thereby yielding much stronger constraints. We consider a tower of ultra-light spin-2 fields arising from a warped compactification of a single extra dimension and translate superradiant constraints on their masses into constraints on the warping. As a concrete scenario we consider the 2-brane Randall-Sundrum model and find constraints on the size of the extra dimension and the curvature of $AdS_5$. We discuss the implications of these bounds for strongly warped throats and D-brane uplifts commonly used in attempts to realise metastable de Sitter vacua in string theory.