Gravitational Kaluza-Klein modes in the String-Cigar Braneworld

TL;DR

This paper analyzes gravitational Kaluza-Klein modes in six-dimensional string-like braneworlds, revealing a new massless mode, a detailed spectrum, and resonant massive gravitons, with differences between thin and thick models.

Contribution

It introduces a comprehensive numerical analysis of KK modes in both thin and thick string-like braneworld models, highlighting new massless modes and resonance phenomena.

Findings

Discovery of a new massless graviton mode in both models

Identification of a complete graviton spectrum and eigenfunctions

Presence of resonant massive gravitons in the string-cigar model

Abstract

In this work the gravitational Kaluza-Klein (KK) modes are analysed on string-like braneworlds in six dimensions, namely the thin string-like Gherghetta-Shaposhnikov (GS) and the thick string-cigar model. We find a new massless mode in both modes satisfying the respective Schroedinger equation. By means of numerical analysis for both models, a complete graviton spectrum and eigenfunctions is attained. Besides the linear regime, the KK spectrum exhibits a decreasing behavior with an asymmetric mass gap with respect to the massless mode. The discontinuity is bigger in the GS model, and it is invariant upon the geometrical flow. A massive mode is obtained in the GS model with a tiny mass which does not match in any regime. It turns out that in the string-cigar model, the core brane structure smoothes and amplifies the KK modes near the brane. Further, the presence of a potential well allows the existence of resonant massive gravitons for small masses in the string-cigar scenario.