Inflaton perturbations in brane-world cosmology with induced gravity

We study cosmological perturbations in the brane models with an induced Einstein- Hilbert term on a brane. We consider an inflaton confined to a de Sitter brane in a five-dimensional Minkowski spacetime. There are two branches (± branches) of solutions for the background spacetime. In the + branch, which includes the selfaccelerating universe, a resonance appears. In the - branch, which can be thought as the Randall-Sundrum type brane-world with the high energy quantum corrections, there is no resonance. At high energies, we analytically confirm that four-dimensional Einstein gravity is recovered, which is related to the disappearance of van Dam- Veltman-Zakharov discontinuity in de Sitter spacetime. On sufficiently small scales, we confirm that the lineariaed gravity on the brane is well described by the Brans- Dicke theory with ω = 3Hr^c in - branch and ω = -3Hr^c in + branch, respectively, which confirms the existence of the ghost in + branch.