Multiple Hierarchies from a Warped Extra Dimension

TL;DR

This paper develops a stabilization mechanism for multiple branes in a 5D warped spacetime, analyzing radion and graviton spectra, which advances the construction of models with hierarchical mass scales beyond the Standard Model.

Contribution

It introduces a scalar field-based stabilization method for multiple branes, accounting for backreaction and computing radion and graviton spectra in warped extra dimensions.

Findings

Radion masses and couplings are suppressed by energy scales and profiles.

Kaluza-Klein graviton spectra and profiles are computed.

The mechanism enables stable multi-brane configurations for model building.

Abstract

Theories beyond the Standard Model often contain mass scales hierarchically different from the electroweak scale and the Planck scale. It has been shown that such hierarchical mass scales can be realized as typical energy scales of multiple 3-branes in a 5D warped spacetime. We present a mechanism for stabilizing the intervals between the multiple 3-branes in the warped extra dimension, by introducing a single 5D scalar field with brane-localized potentials. We discuss the radion stabilization by solving the Einstein equation and the scalar field equation of motion so that a backreaction effect on the geometry due to the presence of the scalar field is taken into account. Perturbations from the background configuration are then considered with proper identification of multiple radion degrees of freedom. By solving their equations of motion, we compute the mass spectrum of the radion-scalar field system and the radion couplings to brane-localized matter fields, which are found to be suppressed by typical energy scales and radion profiles at the branes. We also compute the mass spectrum of Kaluza-Klein gravitons and their profiles in the extra dimension. Some applications of the setup are briefly described. Our analysis provides a solid ground to build 5D warped extra dimension models with multiple 3-branes.