Massless metric preheating - art. no. 043507

Can super-Hubble metric perturbations be amplified exponentially during pre heating? Yes. An analytical existence proof is provided by exploiting the c onformal properties of massless inflationary models. The traditional conser ved quantity zeta is nonconserved in many regions of parameter space. We in clude back reaction through the homogeneous parts of the inflaton and prehe ating fields and discuss the role of initial conditions on the post-preheat ing power spectrum. Maximum field variances are strongly underestimated if metric perturbations are ignored. We illustrate this in the case of strong self-interaction of the decay products. Without metric perturbations, prehe ating in this case is very inefficient. However, metric perturbations incre ase the maximum field variances and give alternative channels for the reson ance to proceed. This implies that metric perturbations can have a large im pact on calculations of relic abundances of particles produced during prehe ating.