Gravity at the Tip of the Throat

TL;DR

This paper investigates how warped throat geometries in string compactifications influence gravitational interactions and potential observable signatures, including modifications to Newtonian gravity and gravitational wave signals.

Contribution

It provides a detailed analysis of the Kaluza-Klein spectrum and gravitational signatures in warped throats, connecting string theory models to phenomenological constraints.

Findings

KK graviton masses depend on warping and bulk size

Modified Newtonian potential predictions are consistent with current constraints

Warping can produce gravitational wave signals within experimental detection ranges

Abstract

We study the gravitational signatures that arise from compactifying Type IIB supergravity on a compact space containing a Klebanov-Strassler warped throat. After reviewing the dimensional reduction of the 10d graviton and explicitly obtaining the equations of motion for the 4d tensor $h_{\mu\nu}$, vector $h_{\mu n}$ and scalar $h_{mn}$ modes, we find the masses and wavefunctions of the Kaluza-Klein tower of spin-2 states. We explore how the masses and wavefunctions depend on the balance between the strength of the warping and the size of the bulk, and how these relate to the range and strength of the interactions which correct the Newtonian gravitational potential. By computing the modified Newtonian potential for sources on a brane somewhere along the throat, and applying consistency constraints on the Klebanov-Strassler parameters, we obtain predictions for the phenomenological parameter space. In the case of a fully warped throat, and depending on where the brane is along the throat, these predictions are narrow in range and consistent with current observational and experimental constraints. We also begin an exploration of gravitational wave signatures of KK gravitons in warped throats, finding that strong warping can bring the corresponding frequencies down to the windows of current and proposed experiments.