Abstract
Abstract
We present a semiclassical non-perturbative approach for calculating the preheating
process at the end of inflation. Our method involves integrating out the decayed particles within
the path integral framework and subsequently determining world-line instanton solutions in the
effective action. This enables us to obtain the effective action of the inflaton, with its
imaginary part linked to the phenomenon of particle creation driven by coherent inflaton field
oscillations. Additionally, we utilize the Bogoliubov transformation to investigate the evolution
of particle density within the medium after multiple inflaton oscillations. We apply our approach
to various final state particles, including scalar fields, tachyonic fields, and gauge fields.
The non-perturbative approach provides analytical results for preheating that are in accord with
previous methods.