Brane motion in a compact space: Adiabatic perturbations of brane-bulk coupled fluids

When a brane is moving in a compact space, bulk-probing signals originating at the brane can arrive back at the brane outside the lightcone of the emitting event. In this paper, we study how adiabatic perturbations in the brane fluid, coupled to a bulk fluid, propagate in the moving brane. In the no...

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Bibliographic Details
Published in:Physical review. D 2024-01, Vol.109 (2), Article 023540
Main Authors: Bernardo, Heliudson, Guo, Fangyi
Format: Article
Language:English
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Summary:When a brane is moving in a compact space, bulk-probing signals originating at the brane can arrive back at the brane outside the lightcone of the emitting event. In this paper, we study how adiabatic perturbations in the brane fluid, coupled to a bulk fluid, propagate in the moving brane. In the nondissipative regime, we find an effective sound speed for such perturbations, depending on the brane and bulk fluid energy densities, equations of state, and brane speed. In the tight-coupling approximation, the effective sound speed might be superluminal for brane and bulk fluids that satisfy the strong energy condition. This has immediate consequences for brane-world cosmology models.
ISSN:2470-0010
2470-0029
DOI:10.1103/PhysRevD.109.023540