Strong Planck constraints on braneworld and non-commutative inflation

Abstract. We place observational likelihood constraints on braneworld and non-commutative inflation for a number of inflaton potentials, using Planck, WMAP polarization and BAO data. Both braneworld and non-commutative scenarios of the kind considered here are limited by the most recent data even more severely than standard general-relativity models. At more than 95% confidence level, the monomial potential V (φ) ∝ φp is ruled out for p ≥ 2 in the Randall–Sundrum (RS) braneworld cosmology and, for p > 0, also in the high-curvature limit of the Gauss–Bonnet (GB) braneworld and in the infrared limit of non-commutative inflation, due to a large scalar spectral index. Some parameter values for natural inflation, small-varying inflaton models and Starobinsky inflation are allowed in all scenarios, although some tuning is required for natural inflation in a non-commutative spacetime.