Name: Sebastien Clesse Institution: Service de Physique Thorique, Universit Libre de Bruxelles Title: Hybrid inflation along waterfall trajectories Key Words: inflation, waterfall, hybrid model Abstract: By performing a bayesian Monte-Carlo-Markov-Chain analysis, it is shown that a large number of e-folds (more than 60) are generated classically during the waterfall after hybrid inflation in a large part of the parameter space of the model. As a result, the observable perturbation modes leave the Hubble radius during waterfall inflation. The power spectrum of adiabatic perturbations is red, possibly in agreement with CMB constraints. A particular attention has been given to study only the regions for which quantum backreactions do not affect the classical dynamics. Implications concerning the preheating and the absence of topological defects in our universe are discussed.