  In natural inflation models, the inflaton is a pseudo Nambu-Goldstone boson
and the flatness of the potential is protected by shift symmetries. In this
framework, a successful inflation requires the global symmetry to be
spontaneously broken at a scale close to the Planck mass. Such a high value of
the spontaneous breaking scale may not be legitimate in an effective field
theory. On the other hand, if natural inflation occurs during the
nonconventional high-energy era in braneworld cosmology, the conditions for the
inflaton slow rolling can be eased and the spontaneous breaking scale can be
lowered to values below the Planck scale. We examine the observational
constraints on this scenario and study the possibility that the baryon
asymmetry of the universe is generated by the decay of the pseudo
Nambu-Goldstone boson during the reheating era.

High Energy Physics - Phenomenology