Lattice Study of Classical Inflaton Decay

We study numerically the decay of the inflaton by solving the full non-linear equations of motion on the lattice. We confirm that parametric resonance is effective in transferring energy from the inflaton to a scalar field as long as the self-interactions of the second field are very small. However, in the very broad resonance case (q AE 1) the decay rate is limited by scatterings, which significantly slows down the decay. We also find that the inflaton cannot decay via parametric resonance into a scalar field with moderate self-interactions. This means that the preheating stage may be completely absent in many natural inflationary models. 11.10.-z,11.15.Kc,98.80.-k,98.80.Cq Typeset using REVT E X E-mail:tomislav@hepth.cornell.edu y E-mail: roost@hepth.cornell.edu I. INTRODUCTION According to inflationary scenarios of cosmic evolution the Universe undergoes a period of exponential expansion after which it is essentially devoid of matter. At this stage the energy density is almos..