Cosmological screening and the phantom braneworld model

The scalar and vector cosmological perturbations at all length scales of our Universe are studied in the framework of the phantom braneworld model. The model is characterized by the parameter $\Omega_M\equiv M^3/2m^2H_0$, with $M$ and $m$ the 5- and 4-dimensional Planck scales, respectively, and $H_0$ the Hubble parameter today, while $\Omega_M\rightarrow 0$ recovers the $\Lambda\rm CDM$ model. Ignoring the backreaction due to the peculiar velocities and also the bulk cosmological constant, allows the explicit computation of the gravitational potentials, $\Phi$ and $\Psi$. They exhibit exponentially decreasing screening behaviour characterized by a screening length which is a function of the quasidensity parameter $\Omega_M$.