Bulk Matters on a GRS-Inspired Braneworld

TL;DR

This paper studies how different bulk matter fields, including fermions, scalars, and vectors, can be localized or have bound states on a GRS-inspired braneworld with a specific brane configuration.

Contribution

It provides a detailed analysis of localization conditions and mass spectra for various matter fields in a GRS-inspired braneworld model, including the effects of brane separation and scalar couplings.

Findings

Fermion zero modes can be localized on the thick brane with finite brane separation.

Massive bound states and resonances exist for fermions and scalars under certain conditions.

Vector fields do not have localized bound states in this setup.

Abstract

In this paper we investigate the localization and mass spectra of bulk matter fields on a Gergory-Rubakov-Sibiryakov-inspired braneworld. In this braneworld model, there are one thick brane located at the origin of the extra dimension and two thin branes at two sides. For spin 1/2 fermions coupled with the background scalar $\phi$ via $\eta\bar{\Psi}\phi^p\Psi$ with $p$ a positive odd integer, the zero mode of left-hand fermions can be localized on the thick brane for finite distance of the two thin branes, and there exist some massive bound modes and resonance modes. The resonances correspond to the quasi-localized massive fermions. For free massless spin 0 scalars, the zero mode can not be localized on the thick brane when the two thin branes are located finitely. While for a massive scalar $\Phi$ coupled with itself and the background scalar field $\phi$, in order to get a localized zero mode on the thick brane, a fine-tuning relation should be introduced. Some massive bound modes and resonances also will appear. For spin 1 vectors, there is no bound KK mode because the effective potential felt by vectors vanishes outside the two thin branes. We also investigate the physics when the distance of the two thin branes tends to infinity.