Observational constraints on braneworld chaotic inflation

Abstract

We examine observational constraints on chaotic inflation models in the Randall-Sundrum type II braneworld. If inflation takes place in the high-energy regime, the perturbations produced by the quadratic potential are further from scale invariance than in the standard cosmology, in the quartic case more or less unchanged, while for potentials of greater exponent the trend is reversed. We test these predictions against a data compilation including the Wilkinson Microwave Anisotropy Probe measurements of microwave anisotropies and the two degree field galaxy power spectrum. While in the standard cosmology the quartic potential is at the border of what the data allow and all higher powers excluded, we find that in the high-energy regime of braneworld inflation even the quadratic case is under strong observational pressure. We also investigate the intermediate regime where the brane tension is comparable to the inflationary energy scale, where the deviations from scale invariance prove to be greater.