Generation of metric perturbations during preheating - art. no. 023505

We consider the generation of the scalar mode of metric perturbations durin g the preheating stage in a two field model with the potential V(phi, chi) = m(2)phi(2)/2 + g(2) phi(2)chi(2)/2. We discuss two possible sources of su ch perturbations: (a) due to the coupling between the perturbation of the m atter field delta chi and the background part of the matter field chi(0)(t) : (b) due to nonlinear fluctuations in a condensate of "particles" of the f ield chi. Both types of metric perturbations are assumed to be small, and e stimated using the linear theory of;metric perturbations. We estimate analy tically the upper limit of the amplitude of the metric perturbations for al l scales in the limit of so-called broad resonance, and show that the large scale metric perturbations are very small, and taking them into account do es not influence the standard picture of the production of metric perturbat ions in the inflationary scenario.