Full perturbative stability of the charged shellworld bounce

Establish the complete perturbative stability of the charged-AdS shellworld bounce by analyzing the full set of coupled scalar and metric perturbations, including their backreaction on the five-dimensional background spacetime.

Background

The paper studies linear fluctuations of a minimally coupled, massless test scalar field confined to the brane and finds that both short- and long-wavelength scalar modes remain finite across the bounce. This analysis neglects the perturbations’ contribution to the background evolution and does not include metric fluctuations.

The authors explicitly distinguish this test-field result from a complete stability analysis involving coupled scalar and metric perturbations and their backreaction. They therefore leave the full perturbative stability of the bouncing shellworld unresolved.

References

A complete stability analysis would require studying the full set of coupled scalar and metric perturbations, along with their backreaction on the background spacetime. Such an analysis is highly non-trivial and the detailed study of this aspect is deferred to future work.

— Bouncing shellworld embedded in charged AdS spacetime  (2608.22855 - Sherpa et al., 24 Aug 2026) in Section 3, subsection “Evolution of Test Scalar Fluctuations,” concluding paragraph