Lorentz-violating brane worlds and cosmological perturbations

We consider an inflating brane-world setup in which 4-dimensional Lorentz-invariance is violated at high 3-momentum scale PLV ≫ H, where H is the inflationary Hubble parameter. We study massless scalar field in this background as a model for cosmological perturbations. Towards the end of inflation, the spectrum has both the standard, 4-dimensional part due to a brane-localized mode, and exotic, bulk induced contribution. The suppression of the latter is power-law only, (H/PLV ) α , provided that there exist bulk modes with energies ! ≪ H. Contrary to general expectations,