Cosmological perturbations on the Phantom brane

Abstract

We obtain a closed system of equations for scalar perturbations in a multi-component braneworld. Our braneworld possesses a phantom-like equation of state at late times, $w_{\mathrm{eff}}<-1$, but no big-rip future singularity. In addition to matter and radiation, the braneworld possesses a new effective degree of freedom - the 'Weyl fluid' or 'dark radiation'. Setting initial conditions on super-Hubble spatial scales at the epoch of radiation domination, we evolve perturbations of radiation, pressureless matter and the Weyl fluid until the present epoch. We observe a gradual decrease in the amplitude of the Weyl-fluid perturbations after Hubble-radius crossing, which results in a negligible effect of the Weyl fluid on the evolution of matter perturbations on spatial scales relevant for structure formation. Consequently, the quasi-static approximation of Koyama and Maartens provides a good fit to the exact results during the matter-dominated epoch. We find that the late-time growth of density perturbations on the brane proceeds at a faster rate than in $\Lambda$CDM. Additionally, the gravitational potentials $\Phi$ and $\Psi$ evolve differently on the brane than in $\Lambda$CDM, for which $\Phi =\Psi$. On the brane, by contrast, the ratio $\Phi /\Psi$ exceeds unity during the late matter-dominated epoch ($z\lesssim 50$). These features emerge as "smoking gun" tests of phantom brane cosmology and allow predictions of this scenario to be tested against observations of galaxy clustering and large-scale structure.

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Cited by in corpus (10)

• Constraining the Cosmology of the Phantom Brane using Distance Measures
• Phantom braneworld and the Hubble tension
• Cosmological dynamics of brane gravity: A global dynamical system perspective
• Cosmic structure sizes in generic dark energy models
• Constraining phantom braneworld model from cosmic structure sizes
• Emulating $\Lambda$CDM-like expansion on the Phantom brane
• Cosmological screening and the phantom braneworld model
• Versatile parametrization of the perturbation growth rate on the phantom brane
• What if gravity becomes really repulsive in the future?
• The possibility of a stable flat dark energy-dominated Swiss-cheese Brane-world universe with a deceleration-acceleration transition