# Scalar perturbations of Eddington-inspired Born-Infeld braneworld

## TL;DR

This paper analyzes scalar perturbations in Eddington-inspired Born-Infeld braneworld models, deriving stability conditions and identifying parameter ranges where solutions are stable or unstable.

## Contribution

It provides the first detailed stability analysis of scalar perturbations in these models, including conditions for tachyonic-free and stable solutions.

## Key findings

- Solutions are tachyonic-free and stable when F_1(y)>0.
- The known domain wall solution is stable for 0<p<√(8/3).
- Solutions with F_1(y)<0 are unstable.

## Abstract

We consider the scalar perturbations of Eddington-inspired Born-Infeld braneworld models in this paper. The dynamical equation for the physical propagating degree of freedom $\xi(x^\mu,y)$ is achieved by using the Arnowitt-Deser-Misner decomposition method: $F_1(y) {\partial_y^2 \xi} + F_2(y){\partial_y \xi } + {\partial^{\mu}\partial_{\mu}}\xi=0$. We conclude that the solution is tachyonic-free and stable under scalar perturbations for $F_1(y)>0$ but unstable for $F_1(y)< 0$. The stability of a known analytic domain wall solution with the warp factor given by $a(y)= \text{sech}^{\frac{3}{{4p}}}(ky)$ is analyzed and it is shown that only the solution for $0<p<\sqrt{8/3}$ is stable.