Contribution of the hybrid inflation waterfall to the primordial curvature perturbation11A preliminary version of this paper appeared as arXiv:1005.2461

Abstract

A contribution ζχ to the curvature perturbation will be generatedduring the waterfall that ends hybrid inflation, that may be significanton small scales. In particular, it may lead to excessive black hole formation.We here consider standard hybrid inflation, where the tachyonic mass of the waterfallfield is much bigger than the Hubble parameter. We calculate ζχ in the simplest case, and see why earlier calculationsof ζχ are incorrect.