Bulk Fields and Supersymmetry in a Slice of AdS

TL;DR

This work analyzes putting the Standard Model in the bulk of a slice of AdS$_5$ as in the Randall–Sundrum setup, deriving the Kaluza–Klein spectra for scalars, fermions, and gauge fields, and exploring how warp-factor localization can address the fermion mass hierarchy. It extends the framework to include supersymmetry in the bulk, deriving mass relations and zero-mode structures for supermultiplets, and discusses how TeV-brane SUSY breaking can be mediated by bulk gauge fields to yield a phenomenologically viable spectrum. The authors examine phenomenological constraints from electroweak data and higher-dimensional operators, finding that non-supersymmetric bulk scenarios require Higgs localization on the TeV-brane, while supersymmetry allows Higgs and fermions to reside in the bulk with SUSY-breaking effects propagating from the TeV-brane. They propose a TeV-scale SUSY-breaking mechanism with gauge mediation via bulk vectors, offering a framework that combines a high fundamental cutoff with rich TeV-scale phenomenology and potential connections to Planckian physics. Overall, the paper highlights how bulk fields in AdS$_5$ can simultaneously address hierarchy concerns and yield distinctive, testable predictions for collider physics and flavor phenomena.

Abstract

Five-dimensional models where the bulk is a slice of AdS have the virtue of solving the hierarchy problem. The electroweak scale is generated by a ``warp'' factor of the induced metric on the brane where the standard model fields live. However, it is not necessary to confine the standard model fields on the brane and we analyze the possibility of having the fields actually living in the slice of AdS. Specifically, we study the behaviour of fermions, gauge bosons and scalars in this geometry and their implications on electroweak physics. These scenarios can provide an explanation of the fermion mass hierarchy by warp factors. We also consider the case of supersymmetry in the bulk, and analyze the conditions on the mass spectrum. Finally, a model is proposed where the warp factor generates a small (TeV) supersymmetry-breaking scale, with the gauge interactions mediating the breaking to the scalar sector.

Figures (2)

• Figure 1:
• Figure 2: The effective four-dimensional Yukawa coupling $\lambda_{ii}$ as a function of $c_{iL}$, for the case $c_{iL}=c_{iR}$ (solid line) and $c_{iR}=1/2$ (dotted line) .