Fermionic Kaluza-Klein modes in the string-cigar braneworld

TL;DR

This paper investigates fermionic fields in a six-dimensional string-cigar braneworld, introducing a new coupling that yields a smooth, normalized massless mode and analyzing the mass spectrum and resonant states.

Contribution

It proposes a novel fermion coupling in the string-cigar model that ensures a smooth massless mode and explores the resulting mass spectrum and resonant states.

Findings

Massless fermion mode is smooth and normalized.

Massive KK tower shows increasing pattern without tachyons.

Resonant massive modes are identified near the brane.

Abstract

We study the spin 1/2 and spin 3/2 fermion fields in a thick braneworld scenario in six dimensions called string-cigar model. This smooth string-like model has a source that satisfies the dominant energy condition and undergoes a Ricci flow. We propose a new coupling for the fermions with a background gauge field which allows a smooth and normalized massless mode in the brane with positive tension. By numerical methods the mass spectrum and the massive eigenfunctions are obtained. The Kaluza-Klein massive tower exhibits the usual increasing pattern and, in this scenario, the coupling term does not allow tachyonic Kaluza-Klein states. The brane core and the background gauge field alter the properties of the massive KK tower, enhancing the amplitude of the massive states near the origin and changing the properties of the analogue Schroedinger potential. Furthermore, we find massive modes as resonant states in this scenario for both fermionic fields.