Contribution of the hybrid inflation waterfall to the primordial curvature perturbation

A contribution $\zeta_\chi$ to the curvature perturbation will be generated during the waterfall that ends hybrid inflation, that may be significant on small scales. In particular, it may lead to excessive black hole formation. We here consider standard hybrid inflation, where the tachyonic mass of the waterfall field is much bigger than the Hubble parameter. We calculate $\zeta_\chi$ in the simplest case, and see why earlier calculations of $\zeta_\chi$ are incorrect.Comment: Simpler and more complete results, especiallly for delta N approac

The Non-Gaussianity of Racetrack Inflation Models

In this paper, we use the result in [7] to calculate the non-Gaussianity of the racetrack models in [3, 5]. The two models give different non- Gaussianities. Both of them are reasonable.Comment: 8 pages, no figures; PACS and Keywords are added; mistake is correcte

Gauge-invariant perturbations at second order: multiple scalar fields on large scales

We derive the governing equations for multiple scalar fields minimally coupled to gravity in a flat Friedmann–Robertson–Walker background spacetime on large scales. We include scalar perturbations up to second order and write the equations in terms of physically transparent gauge-invariant variables at first and second order. This allows us to write the perturbed Klein–Gordon equation at second order solely in terms of the field fluctuations on flat slices at first and second order