Warping, Extra Dimensions and a Slice of AdS_d

TL;DR

This paper explores the extension of Randall-Sundrum models to higher-dimensional AdS spaces, analyzing Kaluza-Klein spectra, fermion localization, and the viability of bulk Standard Model fields, concluding they are likely confined to the IR brane.

Contribution

It generalizes the RS approach to flavor and gauge fields in AdS_d spaces with d > 5, analyzing KK spectra and the implications for Standard Model field localization.

Findings

KK spectra for gravitons, vectors, and gauge-scalars in higher dimensions

Bulk SM fields are not viable due to volume suppression of gauge couplings

Localization of chiral fermions controlled by bulk Dirac mass parameters

Abstract

Inspired by the Randall-Sundrum (RS) framework we consider a number of phenomenologically relevant model building questions on a slice of compactified AdS_d for d >5. Such spaces are interesting as they enable one to realize the weak scale via warping. We perform the Kaluza-Klein (KK) reduction for gravitons and bulk vectors in these spaces and for the case of AdS_6 consider the KK spectrum of gauge-scalars. We further obtain the KK towers for bulk fermions on a slice of AdS_7 and AdS_9 and show that the RS approach to flavor generalizes to these spaces with the localization of chiral zero mode fermions controlled by their bulk Dirac mass parameters. However for the phenomenologically interesting case where the transverse radius is R^{-1}\sim TeV we show that bulk Standard Model fields are not viable due to a resulting volume suppression of the gauge coupling constants. A similar suppression occurs for the case of UV localization. Thus it seems that the Standard Model fields should be confined to the infrared brane in such spaces. Sterile fields and extended gauge sectors may propagate in the bulk with the gauge-coupling volume suppression experienced by the latter motivating a weak coupling to Standard Model fields. We also discuss some issues regarding the effective 4D theory description in these spaces.