Quenching preheating by light fields

In this paper we investigate the role of additional light fields not directly coupled to the background during preheating. We extend our previous study that proved that the production of particles associated with such fields can be abundant due to quantum corrections, even for the massless states. We also obtain the expression for the occupation number operator in terms of interacting fields which includes the non-linear effects important for non-perturbative particle production. We show that adding too many light degrees of freedom without direct interactions with the background might attenuate or even quench preheating as the result of backreaction effects.