Steep inflation: Ending braneworld inflation by gravitational particle production - art. no. 023509

We propose a scenario for inflation based upon the braneworld picture, in w hich high-energy corrections to the Friedmann equation permit inflation to take place with potentials ordinarily too steep to sustain it. Inflation en ds when the braneworld corrections begin to lose their dominance. Reheating may naturally be brought about via gravitational particle production, rath er than the usual inflaton decay mechanism; the reheat temperature may be l ow enough to satisfy the gravitino bound and the Universe becomes radiation dominated early enough for nucleosynthesis. We illustrate the idea by cons idering steep exponential potentials, and show they can give satisfactory d ensity perturbations (both amplitude and slope) and reheat successfully. Th e scalar field may survive to the present epoch without violating observati onal bounds, and could be invoked in the quintessential inflation scenario of Peebles and Vilenkin.