Inflation and braneworlds: Degeneracies and consistencies

Scalar and tensor perturbations arising in an inflationary braneworld scenario driven by a single scalar field are considered, where the bulk on either side of the brane corresponds to anti–de Sitter spaces with different cosmological constants. A consistency relation between the two spectra is derived and found to have an identical form to that arising in standard single-field inflation based on conventional Einstein gravity. The de Sitter/conformal field theory correspondence may provide further insight into the origin of this degeneracy. Possible ways of lifting such a degeneracy are discussed.