The evolution of fields in the process of preheating in the early Universe

The long-term evolution of fields on the stage of primary heating of the Universe after inflation is investigated. Preheating is the stage of evolution of the Universe at which the inflaton, after the stage of slow rolling down on inflation, begins to oscillate near the minimum of its potential energy and act as a compelling external force in the equations of motion of other fields that were in a quantum state with a relatively small amplitude on inflation. Numerical calculations of the system's dynamics for long times shows that during the early phase of preheating, the energy of the material field is due to parametric resonance it grows to the energy of the inflaton. However, after a considerable duration, when the energies of the fields become aligned and there is a multiple transfer of energy from one field to another, the energy of the material field decreases faster than the energy of the inflaton. This could suggest that parametric resonance may not be sufficient for the disintegration of the inflaton and pumping its energy into the energy of material fields.