In a de Sitter braneworld a four-dimensional expanding universe is realized as a brane embedded in a five-dimensional warped bulk, and its gravitational perturbations along the extra dimension obey a Schrodinger-like equation with a Poschl-Teller-shaped effective potential. Solving this equation analytically shows that, apart from the graviton zero mode, the quasinormal spectrum consists of a discrete set of purely imaginary frequencies, so the perturbations decay without oscillation. The spectrum depends only on the brane internal-structure parameter and the Hubble constant, letting the brane cosmological constant be read off from the late-time gravitational-wave signal.
This paper studies the quasinormal modes (QNMs) of gravitational perturbations in de Sitter (dS) braneworld models: five-dimensional spacetimes in which a four-dimensional de Sitter brane, carrying a…