Fermion localization on asymmetric two-field thick branes

TL;DR

This paper studies how fermions can be localized on asymmetric thick branes generated by two scalar fields, analyzing different couplings and identifying conditions for trapping left-handed fermion zero modes.

Contribution

It introduces and analyzes fermion coupling functions on asymmetric two-field branes, identifying conditions for fermion localization that differ from single-scalar models.

Findings

The coupling $ar{ ext{ extPsi}} ext{ extChi} ext{ extPhi} ext{ extPsi}$ does not support fermion localization.

The combination $ar{ ext{ extPsi}} ext{ extChi} ext{ extPsi} + ar{ ext{ extPsi}} ext{ extPhi} ext{ extPsi}$ allows trapping of left-handed fermion zero modes.

Localization depends on the specific scalar-fermion coupling functions and parameters.

Abstract

In this paper we investigate the localization of fermions on asymmetric thick branes generated by two scalars $\phi$ and $\chi$. In order to trap fermions on the asymmetric branes with kink-like warp factors, the couplings with the background scalars $\eta\bar{\Psi}F(\chi,\phi)\Psi$ are introduced, where $F(\chi,\phi)$ is a function of $\phi$ and $\chi$. We find that the coupling $\eta\bar{\Psi}\chi\phi\Psi$ do not support the localization of 4-dimensional fermions on the branes. While, for the case $\eta\bar{\Psi}\chi\Psi+\eta'\bar{\Psi}\phi\Psi$, which is the kink-fermion coupling corresponding to one-scalar-generated brane scenarios, the zero mode of left-handed fermions could be trapped on the branes under some conditions.