Stability and (quasi-)localization of gravitational fluctuations in Eddington-Inspired Born-Infeld brane system

TL;DR

This paper demonstrates the stability and localization of gravitational fluctuations in a general EiBI brane system, showing that the massless graviton can be localized and analyzing the spectrum of massive KK gravitons with two example models.

Contribution

It extends previous work by analyzing general brane systems in EiBI gravity, revealing conditions for stability, localization, and the emergence of gravitational resonances.

Findings

Gravitational perturbations are stable in general EiBI brane systems.

The massless graviton can be localized on the brane.

Resonances appear when the brane has inner structure.

Abstract

Stability and localization of the gravitational perturbations for a special brane system in Eddington-inspired Born-Infeld (EiBI) gravity were studied in [Phys. Rev. D 85, 124053 (2012)]. In this paper, we show that the gravitational perturbations for a general brane system are stable, the four-dimensional graviton (massless KK graviton) can be localized on the brane, and the mass spectrum of massive KK gravitons are gapless and continuous. Two models are constructed as examples. In the first model, which is a generalization of [Phys. Rev. D 85, 124053 (2012)], the brane has no inner structure and there is no gravitational resonance (quasi-localized KK gravitons). In the second one, the background scalar field is a double-kink when the parameter in the model approaches its critical value. Correspondingly, the brane has inner structure and some gravitational resonances appear.